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Kinematical Reconstruction of the ttbar System Near its Threshold at
Future e+e- Linear Colliders: We developed a new method for full kinematical reconstruction of the ttbar
system near its threshold at future linear e+e- colliders. In the core of the
method lies likelihood fitting which is designed to improve measurement
accuracies of the kinematical variables that specify the final states resulting
from ttbar decays. The improvement is demonstrated by applying this method to a
Monte-Carlo ttbar sample generated with various experimental effects including
beamstrahlung, finite acceptance and resolution of the detector system, etc. A
possible application of this method and its expected impact are also discussed. | hep-ex |
Search for Supersymmetry in Events with Large Missing Transverse
Momentum, Jets, and at Least One Tau Lepton in 7 TeV Proton-Proton Collision
Data with the ATLAS Detector: A search for supersymmetry (SUSY) in events with large missing transverse
momentum, jets, and at least one hadronically decaying tau lepton, with zero or
one additional light lepton (e/mu), has been performed using 4.7 fb-1 of
proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS
detector at the Large Hadron Collider. No excess above the Standard Model
background expectation is observed and a 95% confidence level visible
cross-section upper limit for new phenomena is set. In the framework of
gauge-mediated SUSY-breaking models, lower limits on the mass scale Lambda are
set at 54 TeV in the regions where the stau is the next-to-lightest SUSY
particle (tan(beta) > 20). These limits provide the most stringent tests to
date of GMSB models in a large part of the parameter space considered. | hep-ex |
Recent Results from the KTeV Experiment: We present recent preliminary results from five decay channels. From the
$K_L\to\pi^+\pi^-\gamma$ channel, we extract form factors for the CP violating
M1 direct photon emission amplitude and the fraction of the total decay
amplitude that is due to direct emission. We have placed an upper limit on the
$K_L\to\pi^0\pi^0\gamma$ branching ratio, and preliminary measurements of the
$K_L\to\pi^{\pm}e^{\mp}\nu e^+e^-$ and $\pi^0\to e^+e^-$ branching ratios are
presented. Finally, we report measurements of both the branching ratio and the
form factor parameters for the decay $K_L\to e^+e^-\gamma$. | hep-ex |
Search for supersymmetry in final states with disappearing tracks in
proton-proton collisions at $\sqrt{s}$ = 13 TeV: A search is presented for charged, long-lived supersymmetric particles in
final states with one or more disappearing tracks. The search is based on data
from proton-proton collisions at a center-of-mass energy of 13 TeV collected
with the CMS detector at the CERN LHC between 2016 and 2018, corresponding to
an integrated luminosity of 137 fb$^{-1}$. The search is performed over final
states characterized by varying numbers of jets, b-tagged jets, electrons, and
muons. The length of signal-candidate tracks in the plane perpendicular to the
beam axis is used to characterize the lifetimes of wino- and higgsino-like
charginos produced in the context of the minimal supersymmetric standard model.
The d$E$/d$x$ energy loss of signal-candidate tracks is used to increase the
sensitivity to charginos with a large mass and thus a small Lorentz boost. The
observed results are found to be statistically consistent with the
background-only hypothesis. Limits on the pair production cross section of
gluinos and squarks are presented in the framework of simplified models of
supersymmetric particle production and decay, and for electroweakino production
based on models of wino and higgsino dark matter. The limits presented are the
most stringent to date for scenarios with light third-generation squarks and a
wino- or higgsino-like dark matter candidate capable of explaining the known
dark matter relic density. | hep-ex |
Forward Jets, Dijets, and Subjets at the Tevatron: Recent new results on the determination of the rapidity dependence of the
differential inclusive jet cross section, $<d^{2}\sigma/d\et d\eta >$, as a
function of jet $E_{T}$ in \ppbar collisions at $\sqrt{s}=1800$ GeV, measured
by the D0 detector at the Tevatron, are presented along with the comparisons to
theoretical next-to-leading order (NLO) perturbative QCD predictions. Triple
differential dijet cross sections, $<d^{3}\sigma/d\et d\eta_{1} d\eta_{2}>$, at
$\sqrt{s}=1800$ GeV, as well as the new results on jet structure at
$\sqrt{s}=1800$ and 630 GeV, as measured by the CDF and D0 detectors, are also
discussed. | hep-ex |
Observation of the $Y(4230)$ and a new structure in $e^+e^- \rightarrow
K^+K^-J/ψ$: The cross sections of $e^+e^- \rightarrow K^+K^-J/\psi$ at center-of-mass
energies from 4.127 to 4.600~GeV are measured based on 15.6 fb$^{-1}$ data
collected with the BESIII detector operating at the BEPCII storage ring. Two
resonant structures are observed in the line shape of the cross sections. The
mass and width of the first structure are measured to be
($4225.3\pm2.3\pm21.5$) MeV and ($72.9\pm6.1\pm30.8$)~MeV, respectively. They
are consistent with those of the established $Y(4230)$. The second structure is
observed for the first time with a statistical significance greater than
8$\sigma$, denoted as $Y(4500)$. Its mass and width are determined to be
($4484.7\pm13.3\pm24.1$) MeV and ($111.1\pm30.1\pm15.2$) MeV, respectively. The
first presented uncertainties are statistical and the second ones are
systematic. The product of the electronic partial width with the decay
branching fraction $ \Gamma(Y(4230)\to e^+ e^-) \mathcal{B}(Y(4230) \to K^+ K^-
J/\psi)$ is reported. | hep-ex |
Photoproduction of Isolated Photons, Inclusively and with a Jet, at HERA: The photoproduction of isolated photons, both inclusive and together with a
jet, has been measured with the ZEUS detector at HERA using an integrated
luminosity of $374\, \mathrm{pb}^{-1}$. Differential cross sections are
presented in the isolated-photon transverse-energy and pseudorapidity ranges $6
< E_T^\gamma < 15$ GeV and $-0.7 < \eta^\gamma < 0.9,$ and for jet
transverse-energy and pseudorapidity ranges $4 < E_T^{jet} < 35$ GeV and $-1.5
< \eta^{jet} < 1.8,$ for exchanged-photon virtualities $Q^2 < 1$ GeV$^2$.
Differential cross sections are also presented for inclusive isolated-photon
production as functions of the transverse energy and pseudorapidity of the
photon. Higher-order theoretical calculations are compared to the results. | hep-ex |
Search for pair-produced leptoquarks in e+e- interactions at sqrt(s) =
183 GeV: A search for pair-produced leptoquarks has been performed using a sample of
e+e- collision events collected by the OPAL detector at LEP at e+e-
centre-of-mass energies of about 183 GeV. The data sample corresponds to an
integrated luminosity of 55.9 pb-1. The leptoquarks were assumed to be produced
via couplings to the photon and the Z0 and then to decay within a single
fermion generation. No evidence for contributions from leptoquark pair
production processes was observed. Lower limits on scalar and vector leptoquark
masses are obtained. The existing limits are improved in the region of large
decay branching ratio to quark-neutrino. | hep-ex |
phi2/alpha: We report the recent phi2/alpha results from Belle with KEKB accelerator and
Babar with PEP-II accelerator. The analysis of B->pi pi, B->rho rho and B->rho
pi are included in this report. These b->u u_bar d decay modes are related to
the CKM angle phi2/alpha and the method of phi2/alpha extraction of
corresponding decay are also included. After combining all the decay modes, the
constraint of phi2/alpha is 100.2+15.0-8.8 degree. | hep-ex |
First measurements of absolute branching fractions of $Ξ_c^0$ at Belle: We present the first measurements of absolute branching fractions of
$\Xi_c^0$ decays into $\Xi^- \pi^+$, $\Lambda K^- \pi^+$, and $p K^- K^- \pi^+$
final states. The measurements are made using a data set comprising $(772\pm
11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance
with the Belle detector at the KEKB $e^+e^-$ collider. We first measure the
absolute branching fraction for $B^- \to \bar{\Lambda}_c^- \Xi_c^0$ using a
missing-mass technique; the result is ${\cal B}(B^- \to \bar{\Lambda}_c^-
\Xi_c^0) = (9.51 \pm 2.10 \pm 0.88) \times 10^{-4}$. We subsequently measure
the product branching fractions ${\cal B}(B^- \to \bar{\Lambda}_c^-
\Xi_c^0){\cal B}(\Xi_c^0 \to \Xi^- \pi^+)$, ${\cal B}( B^- \to
\bar{\Lambda}_c^- \Xi_c^0) {\cal B}(\Xi_c^0 \to \Lambda K^- \pi^+)$, and ${\cal
B}( B^- \to \bar{\Lambda}_c^- \Xi_c^0) {\cal B}(\Xi_c^0 \to p K^- K^- \pi^+)$
with improved precision. Dividing these product branching fractions by the
result for $B^- \to \bar{\Lambda}_c^- \Xi_c^0$ yields the following branching
fractions: ${\cal B}(\Xi_c^0 \to \Xi^- \pi^+)= (1.80 \pm 0.50 \pm 0.14)\%$,
${\cal B}(\Xi_c^0 \to \Lambda K^- \pi^+)=(1.17 \pm 0.37 \pm 0.09)\%$, and
${\cal B}(\Xi_c^0 \to p K^- K^- \pi^+)=(0.58 \pm 0.23 \pm 0.05)\%.$ For the
above branching fractions, the first uncertainties are statistical and the
second are systematic. Our result for ${\cal B}(\Xi_c^0 \to \Xi^- \pi^+)$ can
be combined with $\Xi_c^0$ branching fractions measured relative to $\Xi_c^0
\to \Xi^- \pi^+$ to yield other absolute $\Xi_c^0$ branching fractions. | hep-ex |
Beam-Spin Asymmetries in the Azimuthal Distribution of Pion
Electroproduction: A measurement of the beam-spin asymmetry in the azimuthal distribution of
pions produced in semi-inclusive deep-inelastic scattering off protons is
presented. The measurement was performed using the {HERMES} spectrometer with a
hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of
HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle
$\phi$ of the hadron production plane around the virtual photon direction
relative to the lepton scattering plane was measured for $\pi^+,\pi^-$ and
$\pi^0$ mesons. The dependence of this amplitude on the Bjorken scaling
variable and on the pion fractional energy and transverse momentum is
presented. The results are compared to theoretical model calculations. | hep-ex |
Recent Results of BABAR: The BABAR detector at SLAC's PEP-II storage ring has collected data
equivalent to about 30.4 fb-1 through June 2001. Results on CP violation, and
in particular searches for direct CP violation, and measurement of rare B
decays are presented. | hep-ex |
Search for a light CP-odd Higgs boson in the radiative decays of J/psi: We search for a light Higgs boson $A^0$ in the fully reconstructed decay
chain of $J/\psi \rightarrow \gamma A^0$, $A^0 \rightarrow \mu^+\mu^-$ using
$(225.0\pm2.8)\times10^6$ $J/\psi$ events collected by the BESIII experiment.
The $A^0$ is a hypothetical CP-odd light Higgs boson predicted by many
extensions of the Standard Model including two spin-0 doublets plus an extra
singlet. We find no evidence for $A^0$ production and set $90\%$
confidence-level upper limits on the product branching fraction
$\mathcal{B}(J/\psi \rightarrow \gamma A^0) \times \mathcal{B}(A^0 \rightarrow
\mu^+\mu^-)$ in the range of $(2.8-495.3)\times 10^{-8}$ for $0.212 \le m_{A^0}
\le 3.0$ GeV/c$^2$. The new limits are $5$ times below our previous results,
and the nature of the $A^0$ is constrained to be mostly singlet. | hep-ex |
Measurements of Neutral B Decay Branching Fractions to K0S pi+ pi- Final
States and the Charge Asymmetry of B0 --> K*+ pi-: We analyze the decay B0 -> K0s pi+ pi- using a sample of 232 million
Upsilon(4S) -> BB decays collected with the BaBar detector at the SLAC PEP-II
asymmetric-energy B factory. A maximum likelihood fit finds the following
branching fractions: BF(B0 -> K0 pi+ pi-) = (43.0 +/- 2.3 +/- 2.3) x 10^{-6},
BF(B0 -> f0 (-> pi+ pi-) K0) = (5.5 +/- 0.7 +/- 0.5 +/- 0.3) x 10^{-6} and
BF(B0 -> K*+ pi-) = (11.0 +/- 1.5 +/- 0.5 +/- 0.5) x 10^{-6}. For these
results, the first uncertainty is statistical, the second is systematic, and
the third (if present) is due to the effect of interference from other
resonances. We also measure the CP-violating charge asymmetry in the decay B0
-> K*+ pi-, A(B0 -> K*+ pi-) = -0.11 +/- 0.14 +/- 0.05. | hep-ex |
Search for Doubly Charmed Baryons Xi_cc^+ and Xi_cc^++ in BABAR: We search for the production of doubly charmed baryons in e^+e^-
annihilations at or near a center-of-mass energy of 10.58 GeV, in a data sample
with an integrated luminosity of 232 fb^-1 recorded with the BABAR detector at
the PEP-II storage ring at the Stanford Linear Accelerator Center. We search
for Xi_cc^+ baryons in the final states Lambda_c^+K^-pi^+ and Xi_c^0pi^+, and
Xi_cc^++ baryons in the final states Lambda_c^+K^-pi^+pi^+ and Xi_c^0pi^+pi^+.
We find no evidence for the production of doubly charmed baryons. | hep-ex |
Measurement of the Top-antitop Production Cross Section in pp Collisions
at sqrt(s)=7 TeV using the Kinematic Properties of Events with Leptons and
Jets: A measurement of the top-antitop production cross section in proton-proton
collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC
with the CMS detector. The analysis uses a data sample corresponding to an
integrated luminosity of 36 inverse picobarns and is based on the
reconstruction of the final state with one isolated, high transverse-momentum
electron or muon and three or more hadronic jets. The kinematic properties of
the events are used to separate the top-antitop signal from W+jets and QCD
multijet background events. The measured cross section is 173 + 39 - 32 (stat.
+ syst.) pb, consistent with standard model expectations. | hep-ex |
Status of Charm Flavor Physics: The role of charm in testing the Standard Model description of quark mixing
and CP violation through measurements of lifetimes, decay constants and
semileptonic form factors is reviewed. Together with Lattice QCD, charm has the
potential this decade to maximize the sensitivity of the entire flavor physics
program to new physics. and pave the way for understanding physics beyond the
Standard Model at the LHC in the coming decade. The status of indirect searches
for physics beyond the Standard Model through charm mixing, CP-violation and
rare decays is also reported. | hep-ex |
Improved Measurement of the Reactor Antineutrino Flux at Daya Bay: This work reports a precise measurement of the reactor antineutrino flux
using 2.2 million inverse beta decay (IBD) events collected with the Daya Bay
near detectors in 1230 days. The dominant uncertainty on the neutron detection
efficiency is reduced by 56% with respect to the previous measurement through a
comprehensive neutron calibration and detailed data and simulation analysis.
The new average IBD yield is determined to be
$(5.91\pm0.09)\times10^{-43}~\rm{cm}^2/\rm{fission}$ with total uncertainty
improved by 29%. The corresponding mean fission fractions from the four main
fission isotopes $^{235}$U, $^{238}$U, $^{239}$Pu, and $^{241}$Pu are 0.564,
0.076, 0.304, and 0.056, respectively. The ratio of measured to predicted
antineutrino yield is found to be $0.952\pm0.014\pm0.023$
($1.001\pm0.015\pm0.027$) for the Huber-Mueller (ILL-Vogel) model, where the
first and second uncertainty are experimental and theoretical model
uncertainty, respectively. This measurement confirms the discrepancy between
the world average of reactor antineutrino flux and the Huber-Mueller model. | hep-ex |
Amplitude Analysis of the decay D^0 --> K^- K^+ pi^0: Using 385 fb^-1 of e^+e^- collisions at the CM energies of around 10.6 GeV
recorded by the BaBar experiment, we study the amplitudes of the singly
Cabibbo-suppressed decay D^0 --> K^- K^+ pi^0. We measure the strong phase
difference between the D0bar and D0 decays to the K^*(892)^+ K^- state to be
-35.5 +/- 1.9 (stat) +/- 2.2 (syst) degrees, and their amplitude ratio to be
0.599 +/- 0.013 (stat) +/- 0.011 (syst). We observe significant contributions
from the Kpi and K^-K^+ scalar and vector amplitudes, and analyze the moments
of the cosine of the helicity angle in these systems. We find no evidence for
charged, scalar kappa(800) state, nor for higher spin states. We also perform a
model-independent partial wave analysis of the K^-K^+ system in a limited mass
range around 1 GeV/c^2. We study several models for Kpi S-wave amplitude, and
describe which one is favored by our data. | hep-ex |
Reply to 'Corrections to the HARP-CDP Analysis of the LSND Neutrino
Oscillation Backgrounds': The alleged mistakes in recent papers that reanalyze the backgrounds to the
'LSND anomaly' do not exist. We maintain our conclusion that the significance
of the 'LSND anomaly' is not 3.8 sigma but not larger than 2.3 sigma. | hep-ex |
An optimal method of moments to measure the charge asymmetry at the
$Z^0$: Parity violation at LEP or SLC can be measured through the charge asymmetry.
An optimal method of moments is developed here to measure this asymmetry, as
well as similar asymmetries. This method is equivalent to the likelihood fit.
It is simpler in use, as it gives analytical formulas for both the asymmetry
and its statistical error. These formulas give the dependence of the accuracy
on the experimental angular acceptance explicitly. | hep-ex |
Bounds on the width, mass difference and other properties of X(3872) -->
pi+pi-J/psi decays: We present results from a study of X(3872) --> pi+pi- J/psi decays produced
via exclusive B--> K X(3872) decays. We determine the mass to be M_X(3872)=
(3871.84\pm 0.27 (stat)\pm 0.19 (syst)) MeV, a 90% CL upper limit on the
natural width of Gamma_X(3872)<1.2 MeV, the product branching fraction Bf(B+->
K+X(3872))xBf(X(3872)-->pi+pi-J/psi)=(8.61 \pm 0.82(stat) \pm 0.52 (syst))
x10^{-6}, and a ratio of branching fractions Bf(B0--> K0 X(3872))/BF(B+--> K+
X(3872))=0.50\pm 0.14(stat)\pm0.04(syst). The difference in mass between the
X(3872)-->pi+pi-J/psi signals in B+ and B0 decays is Delta M_{X(3872)= (-0.69
\pm 0.97 (stat)} \pm 0.19 (syst)) MeV. A search for a charged partner of the
X(3872) in the decays Bbar0-->K- X+ or B+-->K0X+, X+-->pi+pi0 J/psi resulted in
upper limits on the product branching fractions for these processes that are
well below expectations for the case that the X(3872) is the neutral member of
an isospin triplet. In addition, we examine possible J^{PC} quantum number
assignments for the X(3872) based on comparisons of angular correlations
between final state particles in X(3872)-->pi+pi-J/psi decays with simulated
data for J^{PC} values of 1^{++} and 2^{-+}. We examine the influence of
rho-omega interference in the M(pi+pi-) spectrum. The analysis is based on a
711fb^{-1} data sample that contains 772 million BBbar meson pairs collected at
the Upsilon(4S) resonance in the Belle detector at the KEKB e+e- collider. | hep-ex |
Search for the B_c Meson in Hadronic Z^0 Decays: A search for decays of the B_c meson was performed using data collected from
1990-1995 with the OPAL detector on or near the Z peak at LEP. The decay
channels B_c^+ -> J/psi pi^+, B_c^+ -> J/psi a_1^+ and B_c^+ -> J/psi ell^+ nu
were investigated, where ell denotes an electron or a muon. Two candidates are
observed in the mode B_c^+ -> J/psi pi^+, with an estimated background of (0.63
+/- 0.20) events. The weighted mean of the masses of the two candidates is
(6.32 +/- 0.06) GeV/c^2, which is consistent with the predicted mass of the B_c
meson. One candidate event is observed in the mode B_c^+ -> J/psi ell^+ nu with
an estimated background of (0.82 +/- 0.19) events. No candidate events are
observed in the B_c^+ -> J/psi a_1^+ decay mode, with an estimated background
of (1.10 +/- 0.22) events. Upper bounds at the 90% confidence level are set on
the production rates for these processes. | hep-ex |
Study of Jet Shapes in Inclusive Jet Production in ppbar Collisions at
sqrt{s} = 1.96 TeV: We report on a study of jet shapes in inclusive jet production in $p \bar{p}$
collisions at $\sqrt{s} = 1.96 {\rm TeV}$ using the upgraded Collider Detector
at Fermilab in Run II (CDF II) based on an integrated luminosity of $170 \rm
pb^{-1}$. Measurements are carried out on jets with rapidity $0.1 < |Y^{\rm
jet}| < 0.7$ and transverse momentum 37 GeV/c $< P_T^{\rm jet} < 380$ GeV/c.
The jets have been corrected to the hadron level. The measured jet shapes are
compared to leading-order QCD parton-shower Monte Carlo predictions as
implemented in the PYTHIA and HERWIG programs. PYTHIA, tuned to describe the
underlying event as measured in CDF Run I, provides a better description of the
measured jet shapes than does PYTHIA or HERWIG with their default parameters. | hep-ex |
Measurement of the very rare $K^+\rightarrowπ^+ν\barν$ decay: The NA62 experiment reports the branching ratio measurement BR$(K^+
\rightarrow \pi^+ \nu\bar{\nu}) = (10.6^{+4.0}_{-3.4} |_{\rm stat} \pm 0.9_{\rm
syst}) \times 10 ^{-11}$ at 68% CL, based on the observation of 20 signal
candidates with an expected background of 7.0 events from the total data sample
collected at the CERN SPS during 2016-2018. This provides evidence for the very
rare $K^+ \rightarrow \pi^+ \nu\bar{\nu}$ decay, observed with a significance
of 3.4$\sigma$. The experiment achieves a single event sensitivity of
$(0.839\pm 0.054)\times 10^{-11}$, corresponding to 10.0 events assuming the
Standard Model branching ratio of $(8.4\pm1.0)\times10^{-11}$. This measurement
is also used to set limits on BR($K^+ \to \pi^+ X$), where $X$ is a scalar or
pseudo-scalar particle. Details are given of the analysis of the 2018 data
sample, which corresponds to about 80% of the total data sample. | hep-ex |
Search for magnetic monopoles and stable particles with high electric
charges in 8 TeV $pp$ collisions with the ATLAS detector: A search for highly ionizing particles produced in proton-proton collisions
at 8 TeV center-of-mass energy is performed by the ATLAS collaboration at the
CERN Large Hadron Collider. The dataset used corresponds to an integrated
luminosity of 7.0 fb$^{-1}$. A customized trigger significantly increases the
sensitivity, permitting a search for such particles with charges and energies
beyond what was previously accessible. No events were found in the signal
region, leading to production cross section upper limits in the mass range
200--2500 GeV for magnetic monopoles with magnetic charge in the range
$0.5g_{D}<|g|<2.0g_{D}$, where $g_{D}$ is the Dirac charge, and for stable
particles with electric charge in the range $10<|z|<60$. Model-dependent limits
are presented in given pair-production scenarios, and model-independent limits
are presented in fiducial regions of particle energy and pseudorapidity. | hep-ex |
Investigation of Colour Reconnection in WW Events with the DELPHI
detector at LEP-2: In the reaction e+e- -> WW -> (q_1 qbar_2)(q_3 qbar_4) the usual
hadronization models treat the colour singlets q_1 qbar_2 and q_3 qbar_4 coming
from two W bosons independently. However, since the final state partons may
coexist in space and time, cross-talk between the two evolving hadronic systems
may be possible during fragmentation through soft gluon exchange. This effect
is known as Colour Reconnection. In this article the results of the
investigation of Colour Reconnection effects in fully hadronic decays of W
pairs in DELPHI at LEP are presented. Two complementary analyses were
performed, studying the particle flow between jets and W mass estimators, with
negligible correlation between them, and the results were combined and compared
to models. In the framework of the SK-I model, the value for its kappa
parameter most compatible with the data was found to be: kappa_{SK-I} =
2.2^{+2.5}_{-1.3} corresponding to the probability of reconnection P_{reco} to
be in the range 0.31 < P_{reco} < 0.68 at 68% confidence level with its best
value at 0.52. | hep-ex |
Search for Pair Production of Supersymmetric Top Quarks in Dilepton
Events from $p\bar{p}$ Collisions at $\sqrt{s}$ = 1.96 TeV: We present the results of a search for pair production of the supersymmetric
partner of the top quark (the stop quark $\tilde{t}_{1}$) decaying to a
$b$-quark and a chargino $\chargino$ with a subsequent $\chargino$ decay into a
neutralino $\neutralino$, lepton $\ell$, and neutrino $\nu$. Using a data
sample corresponding to 2.7 fb$^{-1}$ of integrated luminosity of $p\bar{p}$
collisions at $\sqrt{s} = 1.96$ TeV collected by the CDF II detector, we
reconstruct the mass of candidate stop events and fit the observed mass
spectrum to a combination of standard model processes and stop quark signal. We
find no evidence for $\pairstop$ production and set 95% C.L. limits on the
masses of the stop quark and the neutralino for several values of the chargino
mass and the branching ratio ${\cal B}(\chargino\to\neutralino\ell^{\pm}\nu)$. | hep-ex |
Comparison of D --> K_s^0 pi and D --> K_L^0 pi Decay Rates: We present measurements of D -> K0_S pi and D -> K0_L pi branching fractions
using 281 pb-1 of psi(3770) data at the CLEO-c experiment. We find that B(D0 ->
K0_S pi0) is larger than B(D0 -> K0_L pi0), with an asymmetry of R(D0) = 0.108
+- 0.025 +- 0.024. For B(D+ -> K0_S pi+) and B(D+ -> K0_L pi+), we observe no
measurable difference; the asymmetry is R(D+) = 0.022 +- 0.016 +- 0.018. The D0
asymmetry is consistent with the value based on the U-spin prediction A(D0 ->
K0 pi0)/A(D0 -> K0bar pi0) = -tan^2(theta_C), where theta_C is the Cabibbo
angle. | hep-ex |
Charmless Hadronic B Decays at CLEO: The CLEO collaboration has studied two-body charmless hadronic decays of $B$
mesons into final states containing two pseudo-scalar mesons, or a
pseudo-scalar and a vector meson. We summarize and discuss results presented
during the winter/spring 1999 conference season, and provide a brief outlook
towards future attractions to come.
In particular, CLEO presented preliminary results on the decays $B^\pm \to
\pi^\pm\rho^0$ ($Br(B^\pm \to \pi^\pm\rho^0) = (1.5 \pm 0.5 \pm 0.4)\times
10^{-5}$), $B\to \pi^\pm\rho^\mp$ ($Br(B\to
\pi^\pm\rho^\mp)=(3.5^{+1.1}_{-1.0}\pm 0.5)\times 10^{-5}$), $B\to \pi^\pm
K^{\star\mp}$ ($Br(B\to \pi^\pm K^{\star\mp}) =
(2.2^{+0.8+0.4}_{-0.6-0.5})\times 10^{-5}$), and $B^\pm \to K^\pm \pi^0$
($Br(B^\pm \to K^\pm \pi^0) = (1.5 \pm 0.4 \pm 0.3) \times 10^{-5}$) at DPF99,
APS99, APS99, and ICHEP98 respectively. None of these decays had been observed
previously. The first two of these constitute the first observation of hadronic
$b\to u$ transitions. In addition, CLEO presented preliminary updates on a
large number of previously published branching fractions and upper limits. | hep-ex |
Pion spectra in Ar+Sc interactions at SPS energies: This contribution discusses recent results from analysis of Ar+Sc
interactions recorded with the NA61/SHINE detector at six beam momenta: 13A,
19A, 30A, 40A, 75A, 150A GeV/c at the CERN SPS. Rapidity and transverse mass
spectra of pions obtained with the "h-" analysis method are presented and
compared to results from p+p, Be+Be and Pb+Pb collisions. | hep-ex |
Real time data analysis with the ATLAS Trigger at the LHC in Run-2: The trigger selection capabilities of the ATLAS detector have been
significantly enhanced for the LHC Run- 2 in order to cope with the higher
event rates and with the large number of simultaneous interactions (pile-up)
per protonproton bunch crossing. A new hardware system, designed to analyse
real time event-topologies at Level-1 came to full use in 2017. A
hardware-based track reconstruction system, expected to be used real-time in
2018, is designed to provide track information to the high-level software
trigger at its full input rate. The high-level trigger selections are largely
relying on offline-like reconstruction techniques, and in some cases
multivariate analysis methods. Despite the sudden change in LHC operations
during the second half of 2017, which caused an increase in pile-up and
therefore also in CPU usage of the trigger algorithms, the set of triggers (so
called trigger menu) running online has undergone only minor modifications
thanks to the robustness and redundancy of the trigger system, and the use of a
levelling luminosity scheme in agreement with LHC and other experiments. This
presentation gives a brief yet comprehensive review of the real-time
performance of the ATLAS trigger system in 2017. Considerations will be
presented on the most relevant parameters of the trigger (efficiency to collect
signal and output data rate) as well as details on some aspects of the
algorithms which are run real-time on the High Level Trigger CPU farm. | hep-ex |
Observation of charmonium pairs produced exclusively in $pp$ collisions: A search is performed for the central exclusive production of pairs of
charmonia produced in proton-proton collisions. Using data corresponding to an
integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies
of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which
have been produced in the absence of any other activity inside the LHCb
acceptance that is sensitive to charged particles in the pseudorapidity ranges
$(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave
charmonia and limits are set on their production. The cross-sections for these
processes, where the dimeson system has a rapidity between 2.0 and 4.5, are
measured to be $$ \begin{array}{rl} \sigma^{J/\psi J/\psi} &= 58\pm10{(\rm
stat)} \pm 6{(\rm syst)} {\rm\ pb} , \\ \sigma^{J/\psi\psi(2S)} &= 63
^{+27}_{-18}{(\rm stat)}\pm 10{(\rm syst)} {\rm\ pb} , \\
\sigma^{\psi(2S)\psi(2S)} &< 237 {\rm\ pb}, \\ \sigma^{\chi_{c0}\chi_{c0}} &<
69 {\rm\ nb}, \\ \sigma^{\chi_{c1}\chi_{c1}} &< 45 {\rm\ pb}, \\
\sigma^{\chi_{c2}\chi_{c2}} &< 141 {\rm\ pb}, \\ \end{array} $$ where the upper
limits are set at the 90% confidence level. The measured $J/\psi J/\psi$ and
$J/\psi\psi(2S)$ cross-sections are consistent with theoretical expectations. | hep-ex |
FunctionalObjects.h: Using Symbolic Syntax in C++ Programs: functionalObjects.h allows the C++ programmer performing common mathematical
calculations to use a more symbolic syntax rather than an algorithmic syntax.
This is not as ambitious as a symbolic manipulation program such as
Mathematica; it is more like having the ability to drop a very simple
Mathematica statement into a C++ program. | hep-ex |
Recent Studies of Exotic Hadrons at the LHCb Experiment: Recent results on studies of exotic hadrons at the LHCb experiment are
summarised. These are the observation of new resonances decaying to J/$\psi
K^{+}$ and J/$\psi\phi$, evidence of a J/$\psi\Lambda$ structure and
observation of excited $\Xi^{-}$ states in the $\Xi_{b}^{-}\to J/\psi \Lambda
K^{-}$ decay and the study of $B_{s}^{0}\to J/\psi\pi^{+}\pi^{-}K^{+}K^{-}$
decays. | hep-ex |
Properties of the X(3872) at Belle: We report recent results on the properties of the X(3872) produced via the B+
--> K+ X(3872) decay process. We observe X -->pi+pi-pi0 J/psi decays where the
3pi invariant masses cluster near the upper kinematic boundary suggesting that
they originate from sub-threshold decays to virtual omega(782) mesons. This is
consistent with expectations for a DD*-bar bound state interpretation for the
X(3872). In addition, we constrain the possible charmonium-state assignments
for this particles. Results are obtained from a 253/fb data sample that
contains 274 million BB-barr pairs that was collected near the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. | hep-ex |
SM+Top at the LHC: These proceedings highlight a selection of recent results by the ATLAS, CMS
and LHCb collaborations. The majority of the featured analyses make use of the
large set of $\sqrt{s}=13$ TeV proton-proton collision data collected during
the successful second run of the LHC. A particular focus is placed on analyses
of Standard Model processes involving either hadronic jets or W/Z bosons.
Searches and cross-section measurements involving top quark signatures are also
given prominence, as are those targeting highly boosted objects such as W/Z and
H bosons, and which feature the use of large-radius jets and substructure
techniques. | hep-ex |
Up and Down Quark Structure of the Proton: We measure proton structure parameters sensitive primarily to valence quarks
using 8.6 fb$^{-1}$ of data collected by the D0 detector in $\sqrt{s}=1.96$ TeV
$p\bar{p}$ collisions at the Fermilab Tevatron. We exploit the property of the
forward-backward asymmetry in dilepton events to be factorized in to distinct
structure parameters and electroweak quark-level asymmetries. Contributions to
the asymmetry from $s$, $c$ and $b$ quarks, as well as from $u$ and $d$ quarks,
are suppressed allowing valence $u$ and $d$ quarks to be separately determined.
We find and $u$ to $d$ quark ratio near the peak values in the quark density
distributions that is smaller than predictions from modern parton distribution
functions. | hep-ex |
Dalitz Plot Study of B0 --> K+K-K0S Decays: We present a study of the dynamics in B0 --> K+ K- K0S decays with
approximately 230 million BBbar events collected by the BABAR detector at SLAC.
We find that the Dalitz plot distribution is best parameterized with the phi
K0S mode, an S-wave K+ K- resonance near 1500 MeV/c^2, and a large non-resonant
contribution. We set limits on resonances not included in our model, and study
models for the non-resonant contribution. | hep-ex |
Combined measurements of the properties of the Higgs boson using the
ATLAS detector: The combined measurement of the mass, couplings and spin-CP properties of the
recently discovered Higgs boson obtained with the ATLAS detector using up to
$25$ fb$^{-1}$ of $7$ TeV and $8$ TeV $pp$ collision data is reviewed. | hep-ex |
Production of $π^{0}$, $K^{\pm}$ and $η$ mesons in Pb-Pb and pp
collisions at $\sqrt{s_{\rm NN}}=$2.76 TeV measured with the ALICE detector
at the LHC: One of the key signatures of the Quark-Gluon Plasma (QGP) is the modification
of hadron transverse momentum differential cross-sections in heavy-ion
collisions (HIC) as compared to proton-proton (pp) collisions. Suppression of
hadron production at high transverse momenta ($p_{\rm T}$) in HIC has been
explained by the energy loss of the partons produced in the hard scattering
processes which traverse the deconfined quantum chromodynamic (QCD) matter. The
dependence of the observed suppression on the $p_{\rm T}$ of the measured
hadron towards higher $p_{\rm T}$ is an important input for the theoretical
understanding of jet quenching effects in the QGP and the nature of the energy
loss, while suppression towards lower $p_{\rm T}$ gives information about
collective behaviour. The ALICE experiment at the Large Hadron Collider (LHC)
performs a variety of measurements including the spectra of neutral mesons and
kaons at mid-rapidity in a wide $p_{\rm T}$ range in pp, p-Pb and Pb-Pb
collisions. An overview of ALICE results in HIC and pp collisions at
$\sqrt{s_{NN}}=$2.76 TeV of neutral pions, kaons and eta mesons as a function
of transverse momentum ($p_{\rm T}$) and centrality will be presented. Ratios
$\eta$/$\pi^{0}$, $K^{\pm}$/$\pi^{\pm}$ as well as comparisons to model
calculations will also be discussed. | hep-ex |
A study of time-dependent CP-violating asymmetries in B0 --> J/psi K0S
and B0 --> psi(2S) K0S decays: BABAR has studied the time dependent asymmetries in the the decays B0 ->
J/psi K0S and B0 -> psi(2S) K0S in a data set of 9.0 fb^-1 taken at the
Y(4S)resonance. In these channels we reconstruct 168 events of which 120 are
flavor tagged and used in a likelihood fit where we determine sin2beta. The
flavor of the other neutral $B$ mesons is tagged using information primarily
from identified leptons and Kaons. A neural network is used to recover events
without any clear Kaon or lepton signature. A preliminary result of
sin2beta=0.12+/-0.37+/-0.09 is obtained. | hep-ex |
Search for $B \to π\ell^+\ell^-$ Decays at Belle: We present a search for the B-> pi e^+ e^- and B-> pi \mu^+ \mu^- decays,
with a data sample of 657 million BBbar pairs collected with the Belle detector
at the KEKB $e^+e^-$ collider. Signal events are reconstructed from a charged
or a neutral pion candidate and a pair of oppositely charged electrons or
muons. No significant signal is observed and we set the upper limit on the
isospin-averaged branching fraction BF(B -> \pi \ell^+\ell^-) < 6.2x10^-8 at
the 90% confidence level. | hep-ex |
A Vision of Nuclear and Particle Physics: This paper will consist of a selected, personal view of some of the issues
associated with the intersections of nuclear and particle physics. As well as
touching on the recent developments we will attempt to look at how those
aspects of the subject might evolve over the next few years. | hep-ex |
Comparative overview of differential measurements at ATLAS and CMS: The study of the top quark has a central role for both the ATLAS and CMS
experiments. The measurement of the $t\bar{t}$ production differential cross
section, in particular, is sensitive to existence of new resonances, it is a
stringent test of perturbative QCD calculations and it is used to improve the
modelling of $t\bar{t}$ production. ATLAS and CMS provided a large number of
results during the last years at $\sqrt{s}$=7, 8, 13 TeV, in different regions
of the phase space, considering different channels and topology and measuring
the cross section as a function of the kinematic variables of the $t\bar{t}$
system, the top quarks and/or their decay products. Even if the individual
steps are dependent on the specific analysis all the differential cross section
measurements proceed through the same workflow: the event selection, the
background determination, the reconstruction of the $t\bar{t}$ system, the
definition of the fiducial phase space, the unfolding applied to remove the
effect of limited acceptance and resolution of the detector and the evaluation
of the systematic uncertainties. In the following I will focus on the
techniques used by ATLAS and CMS to perform some of these steps while
presenting a selection of recent results by the two experiments. | hep-ex |
Search for magnetic monopoles and stable particles with high electric
charges in 8 TeV $pp$ collisions with the ATLAS detector: A search for highly ionizing particles produced in proton-proton collisions
at 8 TeV center-of-mass energy is performed by the ATLAS collaboration at the
CERN Large Hadron Collider. The dataset used corresponds to an integrated
luminosity of 7.0 fb$^{-1}$. A customized trigger significantly increases the
sensitivity, permitting a search for such particles with charges and energies
beyond what was previously accessible. No events were found in the signal
region, leading to production cross section upper limits in the mass range
200--2500 GeV for magnetic monopoles with magnetic charge in the range
$0.5g_{D}<|g|<2.0g_{D}$, where $g_{D}$ is the Dirac charge, and for stable
particles with electric charge in the range $10<|z|<60$. Model-dependent limits
are presented in given pair-production scenarios, and model-independent limits
are presented in fiducial regions of particle energy and pseudorapidity. | hep-ex |
Recent Progress and Puzzles in Charmonium Physics: While the charmonium model has been effective in describing ccbar bound
mesons, there have been many recently discovered charmonium-like states it
cannot accommodate. Here I provide a review of recent results from the
B-factories including the X(3872), three new particles in the mass range near
3.93 GeV, and four new resonances in initial state radiation (ISR) decays. | hep-ex |
Study of the lineshape of $X(3872)$ using $B$ decays to
$D^0\overline{D}{}^{*0}K$: We present a study of the $X(3872)$ lineshape in the decay $B \to X(3872)K\to
D^0\overline{D}{}^{*0}K$ using a data sample of $772\times 10^6$
$B\overline{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle
detector at the KEKB asymmetric-energy $e^+e^-$ collider. The peak near the
threshold in the $D^0\overline{D}{}^{*0}$ invariant mass spectrum is fitted
using a relativistic Breit-Wigner lineshape. We determine the mass and width
parameters to be $m = 3873.71 ^{+0.56}_{-0.50} ({\rm stat}) \pm0.13 ({\rm
syst}) ~{\rm MeV}/c^2$ and $\Gamma_0 = 5.2 ^{+2.2}_{-1.5} ({\rm stat}) \pm 0.4
({\rm syst})~{\rm MeV}$, respectively. The branching fraction is found to be
${\cal B} (B^+\to X(3872)K^+) \times {\cal{B}}(X(3872) \to
D^0\overline{D}{}^{*0}) = (0.97 ^{+0.21}_{-0.18} ({\rm stat}) \pm 0.10 ({\rm
syst})) \times 10^{-4}$. The signal from $B^0$ decays is observed for the first
time with $5.2\sigma$ significance, and the ratio of branching fractions
between charged and neutral $B$ decays is measured to be ${\cal B}(B^0\to
X(3872)K^0)/{\cal B}(B^+ \to X(3872)K^+) = 1.34^{+0.47}_{-0.40} ({\rm stat})
^{+0.10}_{-0.12} ({\rm syst})$. The peak is also studied using a Flatt\'{e}
lineshape. We determine the lower limit on the $D\overline{D}{}^{*}$ coupling
constant $g$ to be $0.075$ at 95% credibility in the parameter region where the
ratio of $g$ to the mass difference from the $D^0\overline{D}{}^{*0}$ threshold
is equal to $-15.11~{\rm GeV}^{-1}$, as measured by LHCb. | hep-ex |
Evidence for Direct CP Violation from Dalitz-plot analysis of B+/- ->
K+/- pi+/- pi-/+: We report a Dalitz-plot analysis of the charmless hadronic decays of charged
B mesons to the final state K+/- pi+/- pi-/+. Using a sample of 383.2 +/- 4.2
million BBbar pairs collected by the BaBar detector, we measure CP-averaged
branching fractions and direct CP asymmetries for intermediate resonant and
nonresonant contributions. We find evidence for direct CP violation in the
decay B+ -> rho0(770) K+, with a CP violation parameter A_CP = (+44 +/- 10 +/-
4 +5,-13)%. | hep-ex |
Measurement of neutrino oscillations by means of a high density detector
on the atmospheric neutrino beam: A high-density calorimeter, consisting of magnetized iron planes interleaved
by RPCs, as tracking and timing devices, is a good candidate for a next
generation experiment on atmospheric neutrinos. With 34 kt of mass and in four
years of data taking, this experiment will be sensitive to $\nu_\mu \to \nu_x$
oscillation with $\Delta m^2 > 6 \times 10^{-5}$ and mixing near to maximal and
fully cover the region of oscillation parameters suggested by Super-Kamiokande
results. Moreover, the experimental method will enable to measure the
oscillation parameters from the modulation of the L/E spectrum ($\nu_\mu$
disappearance). For $\Delta m^2 > 3 \times 10^{-3}$ eV$^2$, this experiment can
also establish whether the oscillation occurs into a tau or a sterile neutrino,
by looking for an excess of muon-less events at high energies produced by
upward-going tau neutrinos ($\nu_\tau$ appearance). | hep-ex |
Muon Identification at ATLAS and CMS: Muonic final states will provide clean signatures formany physics processes
at the LHC. The two LHC experiments ATLAS and CMS will be able to identify
muons with a high reconstruction efficiency above 96% and a high transverse
momentum resolution better than 2% for transverse momenta below 400 GeV/c and
about 10% at 1 TeV/c. The two experiments follow complentary concepts of muon
detection. ATLAS has an instrumented air-toroid mangetic system serving as a
stand-alone muon spectrometer. CMS relies on high bending power and momentum
resolution in the inner detector, and uses an iron yoke to increase its
magnetic field. The iron yoke is instrumented with chambers used for muon
identification. Therefore, muon momenta can only be reconstructed with high
precision by combining inner-detector information with the data from the muon
chambers. | hep-ex |
Diphoton resonance at e+e- and photon colliders: In this note, I will review the opportunities offered by the hint of a new
resonance observed at LHC for future e+e- TeV linear collider (LC) projects.
This discussion is mainly influenced by two specific scenarios of physics which
assume either a (pseudo-)scalar or a tensor resonance, but these estimates can
be used in most scenarios. I envisage either a photon collider, which has a
guaranteed signal with the LHC observation, or a standard e+e- collider, more
straightforward to implement. After a detailed study of the heavy graviton
scenario, I conclude that at a TeV LC, high accuracy measurements, including
rare modes, allow to unambiguously establish the origin of this resonance. Also
envisaged in some detail is a radion scenario which illustrates the production
of a scalar. The role of an LC for precision measurements on Higgs and top
couplings is recalled in the context of the Randall Sundrum model. | hep-ex |
Dark Matter Benchmark Models for Early LHC Run-2 Searches: Report of the
ATLAS/CMS Dark Matter Forum: This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum
organized by the ATLAS and CMS collaborations with the participation of experts
on theories of Dark Matter, to select a minimal basis set of dark matter
simplified models that should support the design of the early LHC Run-2
searches. A prioritized, compact set of benchmark models is proposed,
accompanied by studies of the parameter space of these models and a repository
of generator implementations. This report also addresses how to apply the
Effective Field Theory formalism for collider searches and present the results
of such interpretations. | hep-ex |
Charm Decays Within the Standard Model and Beyond: The charm quark has unique properties that make it a very important probe of
many facets of the Standard Model. New experimental information on charm decays
is becoming available from dedicated experiments at charm factories, and
through charm physics programs at the b-factories and hadron machines. In
parallel, theorists are working on matrix element calculations based on
unquenched lattice QCD, that can be validated by experimental measurements and
affect our ultimate knowledge of the quark mixing parameters. Recent
predictions are compared with corresponding experimental data and good
agreement is found. Charm decays can also provide unique new physics
signatures; the status of present searches is reviewed. Finally, charm data
relevant for improving beauty decay measurements are presented. | hep-ex |
Evidence for a bottom baryon resonance Lambda_b* in CDF data: Using data from proton-antiproton collisions at Ecms=1.96 TeV recorded by the
CDF II detector at the Fermilab Tevatron, evidence for the excited resonance
state Lambda_b* is presented in its Lambda_b0 pi+ pi- decay, followed by the
Lambda_b0 -->Lambda_c+ (-->proton K- pi+) pi- decays. The analysis is based on
a data sample corresponding to an integrated luminosity of 9.6/fb collected by
an online event selection based on charged-particle tracks displaced from the
proton-antiproton interaction point. The significance of the observed signal is
3.5 Gaussian sigmas. The mass of the observed state is found to be 5919.22 +-
0.76 MeV in agreement with similar findings in proton-proton collision
experiments. | hep-ex |
Search for a W' Boson via the Decay Mode W' -> mu nu in 1.8 TeV p-pbar
Collisions: We report the results of a search for a W' boson produced in p-pbar
collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample
recorded by the Collider Detector at Fermilab. We consider the decay channel W'
-> mu nu and search for anomalous production of high transverse mass mu-nu
lepton pairs. We observe no excess of events above background and set limits on
the rate of W' boson production and decay relative to Standard Model W boson
production and decay using a fit of the transverse mass distribution observed.
If we assume Standard Model strength couplings of the W' boson to quark and
lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c**2
at 95% confidence level. | hep-ex |
Observation of new $Ξ_c^0$ baryons decaying to $Λ_c^+ K^-$: The $\Lambda_c^+K^-$ mass spectrum is studied with a data sample of $pp$
collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated
luminosity of 5.6 fb$^{-1}$ collected by the LHCb experiment. Three $\Xi_c^0$
states are observed with a large significance and their masses and natural
widths are measured to be \begin{eqnarray*} m(\Xi_c(2923)^0)&=& 2923.04 \pm
0.25 \pm 0.20 \pm 0.14 ~\mathrm{MeV}, \Gamma(\Xi_c(2923)^0) &=& 7.1 \pm 0.8 \pm
1.8 ~\mathrm{MeV}, \end{eqnarray*} \begin{eqnarray*} m(\Xi_c(2939)^0) &=&
2938.55 \pm 0.21 \pm 0.17 \pm 0.14 ~\mathrm{ MeV}, \Gamma(\Xi_c(2939)^0) &=&
10.2 \pm 0.8 \pm 1.1 ~\mathrm{ MeV}, \end{eqnarray*} \begin{eqnarray*}
m(\Xi_c(2965)^0) &=& 2964.88 \pm 0.26 \pm 0.14 \pm 0.14~\mathrm{ MeV},
\Gamma(\Xi_c(2965)^0) &=& 14.1 \pm 0.9 \pm 1.3~\mathrm{ MeV}, \end{eqnarray*}
where the uncertainties are statistical, systematic, and due to the limited
knowledge of the $\Lambda_c^+$ mass. The $\Xi_c(2923)^0$ and $\Xi_c(2939)^0$
baryons are new states. The $\Xi_c(2965)^0$ state is in the vicinity of the
known $\Xi_c(2970)^0$ baryon; however, their masses and natural widths differ
significantly. | hep-ex |
Measurements of differential cross sections of Z/gamma*+jets+X events in
proton anti-proton collisions at sqrt{s}=1.96 TeV: We present cross section measurements for Z/gamma*+jets+X production,
differential in the transverse momenta of the three leading jets. The data
sample was collected with the D0 detector at the Fermilab Tevatron proton
anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to
an integrated luminosity of 1 fb-1. Leading and next-to-leading order
perturbative QCD predictions are compared with the measurements, and agreement
is found within the theoretical and experimental uncertainties. We also make
comparisons with the predictions of four event generators. Two
parton-shower-based generators show significant shape and normalization
differences with respect to the data. In contrast, two generators combining
tree-level matrix elements with a parton shower give a reasonable description
of the the shapes observed in data, but the predicted normalizations show
significant differences with respect to the data, reflecting large scale
uncertainties. For specific choices of scales, the normalizations for either
generator can be made to agree with the measurements. | hep-ex |
Determination of αS using OPAL hadronic event shapes at sqrt(s) =
91 - 209 GeV and resummed NNLO calculations: Hadronic event shape distributions from e+e- annihilation measured by the
OPAL experiment at centre-of-mass energies between 91 GeV and 209 GeV are used
to determine the strong coupling {\alpha}S. The results are based on QCD
predictions complete to the next-to- next-to-leading order (NNLO), and on NNLO
calculations matched to the resummed next-to-leading-log-approximation terms
(NNLO+NLLA). The combined NNLO result from all variables and centre-of-mass
energies is {\alpha}S(mZ0) = 0.1201 {\pm} 0.0008(stat.) {\pm} 0.0013(exp.)
{\pm} 0.0010(had.) {\pm} 0.0024(theo.). while the combined NNLO+NLLA result is
{\alpha}S(mZ0) = 0.1189 {\pm} 0.0008(stat.) {\pm} 0.0016(exp.) {\pm}
0.0010(had.) {\pm} 0.0036(theo.). The completeness of the NNLO and NNLO+NLLA
results with respect to missing higher order contributions, studied by varying
the renormalization scale, is improved compared to previous results based on
NLO or NLO+NLLA predictions only. The observed energy dependence of {\alpha}S
agrees with the QCD prediction of asymptotic freedom and excludes the absence
of running. | hep-ex |
X-Ray Multi-Energy Introscopy Systems with New Semiconductor
Scintillators: Theoretical background and data on the ways of practical realization are
presented, related to the problem of detection of dangerous organic objects
(explosives, drugs, etc.) in the presence of other organic substances with
atomic number differing by no more than 20-30%. For this purpose, multi-energy
X-ray introscopy is used. It has been shown that the "weakest link" in the
existing multi-energy introscopes used for safety inspection and medicine are
detectors of ionizing radiation. In particular, critical is the type of
scintillator used in the low-energy detection subsystem. Data are presented on
design principles and properties of combined detectors based on a new type of
semiconductor scintillators (SCS) -- $ZnSe(Te,O)$, with conversion efficiency
of 19-22%, afterglow level less then $0.05 %$ after $10 ms$, and radiation
stability up to $500 Mrad$. Results are given on the practical use of
experimental samples of the low-energy detector subsystem based on the new SCS
material in two-energy introscopes of the 4th and 5th generation. | hep-ex |
Precision Measurements of the Semileptonic Charm Decays $D^0 \to π^-
\ell^+ ν$ and $D^0 \to K^- \ell^+ ν$: We investigate the decays $D^0\to\pi^-\ell^+\nu$ and $D^0\to K^-\ell^+ \nu$,
where $\ell$ is $e$ or $\mu$, using approximately 7 ${\rm fb}^{-1}$ of data
collected with the CLEO III detector. We find $R_0\equiv {\cal B}(D^0\to
\pi^-e^+\nu)/{\cal B}(D^0\to K^-e^+\nu)= 0.082 \pm 0.006 \pm 0.005$. Fits to
the kinematic distributions of the data provide parameters describing the form
factor of each mode. Combining the form factor results and $R_0$ gives
$|f^{\pi}_{+}(0)|^2 |V_{cd}|^2/|f^K_{+}(0)|^2 |V_{cs}|^2 =
0.038^{+0.006+0.005}_{-0.007-0.003}$. | hep-ex |
Recent $J/ψ$ Results from BESII: The studies on the multi-quark candidates, light scalar mesons and excited
baryon states at BES are presented, based on $5.8 \times 10^7$ $J/\psi$ data
collected with BESII detector. The measurements of some $J/\psi$ and $\eta_c$
decays are presented too. We also report the searches for the lepton flavor
violation and pentaquark states in $J/\psi$ decays. | hep-ex |
The Spin Structure Function $g_1^{\rm p}$ of the Proton and a Test of
the Bjorken Sum Rule: New results for the double spin asymmetry $A_1^{\rm p}$ and the proton
longitudinal spin structure function $g_1^{\rm p}$ are presented. They were
obtained by the COMPASS collaboration using polarised 200 GeV muons scattered
off a longitudinally polarised NH$_3$ target. The data were collected in 2011
and complement those recorded in 2007 at 160\,GeV, in particular at lower
values of $x$. They improve the statistical precision of $g_1^{\rm p}(x)$ by
about a factor of two in the region $x\lesssim 0.02$. A next-to-leading order
QCD fit to the $g_1$ world data is performed. It leads to a new determination
of the quark spin contribution to the nucleon spin, $\Delta \Sigma$ ranging
from 0.26 to 0.36, and to a re-evaluation of the first moment of $g_1^{\rm p}$.
The uncertainty of $\Delta \Sigma$ is mostly due to the large uncertainty in
the present determinations of the gluon helicity distribution. A new evaluation
of the Bjorken sum rule based on the COMPASS results for the non-singlet
structure function $g_1^{\rm NS}(x,Q^2)$ yields as ratio of the axial and
vector coupling constants $|g_{\rm A}/g_{\rm V}| = 1.22 \pm 0.05~({\rm stat.})
\pm 0.10~({\rm syst.})$, which validates the sum rule to an accuracy of about
9\%. | hep-ex |
LHCb time-dependent results: This review reports preliminary results of time-dependent measurements of
decays of B^0 mesons and B^0_s mesons coming from the analysis of about 36
pb^-1 of data collected by the LHCb experiment during the 2010 run of the Large
Hadron Collider at sqrt(s)=7 TeV. | hep-ex |
Potential Constraints to Neutrino-Nucleus Interactions Based on Electron
Scattering Data: A thorough understanding of neutrino-nucleus interactions physics is crucial
to achieving precision goals in broader neutrino physics programs. The
complexity of nuclei comprising the detectors and limited understanding of
their weak response constitutes one of the biggest systematic uncertainties in
neutrino experiments - both at intermediate energies affecting the short- and
long-baseline neutrino programs as well as at lower energies affecting coherent
scattering neutrino programs. While electron and neutrino interactions are
different at the primary vertex, many underlying relevant physical processes in
the nucleus are the same in both cases, and electron scattering data collected
with precisely controlled kinematics, large statistics and high precision
allows one to constrain nuclear properties and specific interaction processes.
To this end, electron-nucleus scattering experiments provide vital
complementary information to test, assess and validate different nuclear models
and event generators intended to be used in neutrino experiments. In fact, for
many decades, the study of electron scattering off a nucleus has been used as a
tool to probe the properties of that nucleus and its electromagnetic response.
While previously existing electron scattering data provide important
information, new and proposed measurements are tied closely to what is required
for the neutrino program in terms of expanding kinematic reach, the addition of
relevant nuclei and information on the final states hadronic system. | hep-ex |
Deep Learning for direct Dark Matter search with nuclear emulsions: We propose a new method for the discrimination of sub-micron nuclear recoil
tracks from an instrumental background in fine-grain nuclear emulsions used in
the directional dark matter search. The proposed method uses a 3D Convolutional
Neural Network, whose parameters are optimised by Bayesian search. Unlike
previous studies focused on extracting the directional information, we focus on
the signal/background separation exploiting the polarisation dependence of the
Localised Surface Plasmon Resonance phenomenon. Comparing the proposed method
with the conventional cut-based approach shows a significant boost in the
reduction factor for given signal efficiency. | hep-ex |
Charged kaon lifetime at KLOE: Preliminary result on the charged kaon lifetime, obtained by the KLOE
experiment operating at DA$\Phi$NE, the Frascati $\phi$-factory, is presented | hep-ex |
Observation of $Λ_c^+ \to Λ^0 K^+$, $Λ_c^+ \to
Σ^0 K^+$ and $Λ_c^+ \to Σ^+ K^+π^-$ decays: We present measurements of the Cabibbo-suppressed decays $\Lambda_c^+ \to
\Lambda^0 K^+$ and $\Lambda_c^+ \to \Sigma^0 K^+$ (both first observations),
$\Lambda_c^+ \to \Sigma^+ K^+\pi^-$ (seen with large statistics for the first
time), $\Lambda_c^+ \to p K^+ K^-$ and $\Lambda_c^+ \to p \phi$ (measured with
improved accuracy). Improved branching ratio measurements for the decays
$\Lambda_c^+ \to \Sigma^0 K^+ K^-$ and $\Lambda_c^+ \to \Sigma^0 \phi$, which
are attributed to W-exchange diagrams, are shown. We also present the first
evidence for $\Lambda_c^+ \to \Xi(1690) K^+$ and set an upper limit on
non-resonant $\Lambda_c^+ \to \Sigma^0 K^+ K^-$ decay. This analysis was
performed using 23.6 fb$^{-1}$ of data collected by the Belle detector at the
$e^+ e^-$ asymmetric collider KEKB. | hep-ex |
Observation of medium induced modifications of jet fragmentation in PbPb
collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV using isolated-photon-tagged
jets: Measurements of fragmentation functions for jets associated with an isolated
photon are presented for the first time in pp and PbPb collisions. The analysis
uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon
center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for
jets with p$_\mathrm{T}^\text{jet} >$ 30 GeV in events containing an isolated
photon with p$_\mathrm{T}^\gamma>$ 60 GeV, using charged tracks with transverse
momentum p$_\mathrm{T}^\text{trk} >$ 1 GeV in a cone around the jet axis. The
association with an isolated photon constrains the initial p$_\mathrm{T}$ and
azimuthal angle of the parton whose shower produced the jet. For central PbPb
collisions, modifications of the jet fragmentation functions are observed when
compared to those measured in pp collisions, while no significant differences
are found in the 50% most peripheral collisions. Jets in central PbPb events
show an excess (depletion) of low (high) p$_\mathrm{T}$ particles, with a
transition around 3 GeV. This measurement shows for the first time the
in-medium shower modifications of partons (quark dominated) with well defined
initial kinematics. It constitutes a new well-controlled reference for testing
theoretical models of the parton passage through the QGP. | hep-ex |
Observation of the Higgs boson decay to a pair of tau leptons with the
CMS detector: A measurement of the coupling strength of the Higgs boson to a pair of tau
leptons is performed using events recorded in proton-proton collisions by the
CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV. The
data set corresponds to an integrated luminosity of 35.9 inverse femtobarns.
The H to tau tau signal is established with a significance of 4.9 standard
deviations, to be compared to an expected significance of 4.7 standard
deviations. The best fit of the product of the observed H to tau tau signal
production cross section and branching fraction is 1.09 +0.27-0.26 times the
standard model expectation. The combination with the corresponding measurement
performed with data collected by the CMS experiment at center-of-mass energies
of 7 and 8 TeV leads to an observed significance of 5.9 standard deviations,
equal to the expected significance. This is the first observation of Higgs
boson decays to tau leptons by a single experiment. | hep-ex |
Measurements of underlying-event properties using neutral and charged
particles in pp collisions at 900 GeV and 7 TeV with the ATLAS detector at
the LHC: We present first measurements of charged and neutral particle-flow
correlations in pp collisions using the ATLAS calorimeters. Data were collected
in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were
selected using a minimum-bias trigger which required a charged particle in
scintillation counters on either side of the interaction point. Particle flows,
sensitive to the underlying event, are measured using clusters of energy in the
ATLAS calorimeters, taking advantage of their fine granularity. No Monte Carlo
generator used in this analysis can accurately describe the measurements. The
results are independent of those based on charged particles measured by the
ATLAS tracking systems and can be used to constrain the parameters of Monte
Carlo generators. | hep-ex |
Uncovering the neutrino mass ordering with the next galactic
core-collapse supernova neutrino burst using water Cherenkov detectors: A major challenge of particle physics is determining the neutrino mass
ordering (MO). Due to matter effects, the flavor content of the neutrino flux
from a Core-Collapse Supernova (CCSN) depends on the true neutrino MO resulting
in markedly different energy and angle distributions for the measured lepton in
water Cherenkov neutrino detectors. In this article, those distributions are
compared for eight different CCSN models and used to study how their
differences affect the determination of the neutrino mass ordering. In all
cases, the inferred neutrino mass ordering is found to be either correct or
inconclusive, with no significant false positives. However, the substantial
variation observed among model predictions emphasizes the criticality of
ongoing research in CCSN modeling. | hep-ex |
Standard Model Higgs Boson Searches at the Tevatron: The CDF and D{\O} experiments at the Tevatron are currently the only capable
of searching for the Standard Model Higgs boson. This article describes their
most sensitive searches in the expected Higgs mass range, focusing on advanced
methods used to extract the maximal sensitivity from the data. CDF presents
newly updated results for $H \to W^+W^-$ and $ZH \to l^+l^- b\bar{b}$. D{\O}\
presents two new searches for $WH \to l\nu b\bar{b}$. These new analyses use
the same 1 fb$^{-1}$ dataset as previous searches, but with improved techniques
resulting in markedly improved sensitivity. | hep-ex |
First measurement of $\rm Ω_c^0$ production in pp collisions at
$\sqrt{s}=13$ TeV with ALICE: Recent measurements of charm-baryon production in proton--proton (pp)
collisions at midrapidity by the ALICE collaboration showed that
baryon-to-meson yield ratios are significantly higher than those measured in
$\rm e^+e^-$ collisions. The charm baryon-to-meson and charm baryon-to-baryon
yield ratios provide unique information on hadronization mechanisms since the
contributions from parton distribution function and parton--parton scattering
terms cancel in the ratios. In this contribution, the first measurement of $\rm
\Omega_{c}^{0}$ production via the hadronic decay channel $\rm \Omega_{c}^{0}
\rightarrow \Omega^{-}\pi^{+}$ (and its charge conjugate) in $2<p_{\rm T}<12$
GeV/$c$ performed with the ALICE detector at midrapidity in pp collisions at
$\sqrt{s}=$ 13 TeV is presented. The $\rm \Omega_c^0/D^0$ and $\rm
\Omega_c^0/\Xi_c^0$ ratios multiplied by the decay branching ratio $\rm
BR(\Omega_{c}^{0} \rightarrow \Omega^{-}\pi^+)$, which is not experimentally
measured, are compared to MC generators with fragmentation fractions based on
$\rm e^+e^-$ measurements and models including hadronization of charm quark via
coalescence. | hep-ex |
Inclusive production of π^0 in pp collisions at 0.9 and 7 TeV and
perspectives for heavy-ion measurements with the ALICE calorimeters: The inclusive spectrum of \pi^0 production has been measured in pp collisions
at \sqrt{s} = 900 GeV and 7 TeV with the ALICE experiment. The preliminary
results of these measurements are presented, and perspectives for \pi^0
measurements with heavy ions are discussed. | hep-ex |
Z boson transverse momentum spectrum from the lepton angular
distributions: In view of recent discussions concerning the possibly limiting energy
resolution systematics on the measurement of the Z boson transverse momentum
distribution at hadron colliders, we propose a novel measurement method based
on the angular distributions of the decay leptons. We also introduce a
phenomenological parametrization of the transverse momentum distribution that
adapts well to all currently available predictions, a useful tool to quantify
their differences. | hep-ex |
Improved measurement of solar neutrinos from the Carbon-Nitrogen-Oxygen
cycle by Borexino and its implications for the Standard Solar Model: We present an improved measurement of the CNO solar neutrino interaction rate
at Earth obtained with the complete Borexino Phase-III dataset. The measured
rate R$_{\rm CNO}$ = $6.7^{+2.0}_{-0.8}$ counts/(day$ \cdot$ 100 tonnes),
allows us to exclude the absence of the CNO signal with about 7$\sigma$ C.L.
The correspondent CNO neutrino flux is $6.6^{+2.0}_{-0.9} \times 10^8$
cm$^{-2}$ s$^{-1}$, taking into account the neutrino flavor conversion. We use
the new CNO measurement to evaluate the C and N abundances in the Sun with
respect to the H abundance for the first time with solar neutrinos. Our result
of $N_{\rm CN}$ = $(5.78^{+1.86}_{-1.00})\times10^{-4}$ displays a
$\sim$2$\sigma$ tension with the "low metallicity" spectroscopic photospheric
measurements. On the other hand, our result used together with the $^7$Be and
$^8$B solar neutrino fluxes, also measured by Borexino, permits to disfavour at
3.1$\sigma$ C.L. the "low metallicity" SSM B16-AGSS09met as an alternative to
the "high metallicity" SSM B16-GS98. | hep-ex |
Search for supersymmetry in proton-proton collisions at 13 TeV using
identified top quarks: A search for supersymmetry is presented based on proton-proton collision
events containing identified hadronically decaying top quarks, no leptons, and
an imbalance $p_\mathrm{T}^\text{miss}$ in transverse momentum. The data were
collected with the CMS detector at the CERN LHC at a center-of-mass energy of
13 TeV, and correspond to an integrated luminosity of 35.9 fb$^{-1}$. Search
regions are defined in terms of the multiplicity of bottom quark jet and top
quark candidates, the $p_\mathrm{T}^\text{miss}$, the scalar sum of jet
transverse momenta, and the $m_{\mathrm{T2}}$ mass variable. No statistically
significant excess of events is observed relative to the expectation from the
standard model. Lower limits on the masses of supersymmetric particles are
determined at 95% confidence level in the context of simplified models with top
quark production. For a model with direct top squark pair production followed
by the decay of each top squark to a top quark and a neutralino, top squark
masses up to 1020 GeV and neutralino masses up to 430 GeV are excluded. For a
model with pair production of gluinos followed by the decay of each gluino to a
top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeV and
neutralino masses up to 1150 GeV are excluded. These limits extend previous
results. | hep-ex |
Hot Topics From BABAR Experiment: We search for a new light non-Standard Model CP-odd Higgs boson, $A^0$,
decaying to $\tau^+\tau^-$, $\mu^+\mu^-$, and invisible in radiative decays of
the $\Upsilon(2S)$ and $\Upsilon(3S)$. We search for the light scalar particle
produced in single-photon decays of the $\Upsilon(3S)$ resonance through the
process $\Upsilon(3S) \to \gamma A^0, A^0 \to$ invisible. We also search for
evidence of an undetectable $\Upsilon(1S)$ decay recoiling against the dipion
system. The data samples contain $99 \times 10^6 \Upsilon(2S)$ and $122 \times
10^6 \Upsilon(3S)$ decays collected by the \babar\ detector at the SLAC PEP-II
$B$ factory. | hep-ex |
Measurement of the Absolute Branching Fractions for
$D^-_s\!\rightarrow\!\ell^-\barν_{\ell}$ and Extraction of the Decay
Constant $f_{D_s}$: The absolute branching fractions for the decays
$D^-_s\!\rightarrow\!\ell^-\bar{\nu}_{\ell}$ ($\ell=e$, $\mu$, or $\tau$) are
measured using a data sample corresponding to an integrated luminosity of 521
fb$^{-1}$ collected at center of mass energies near 10.58 GeV with the
\mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller
A\kern-0.2em R}} detector at the PEP-II $e^+e^-$ collider at SLAC. The number
of $D^-_s$ mesons is determined by reconstructing the recoiling system
$DKX\gamma$ in events of the type $e^+e^-{\rightarrow}DKXD^{*-}_s$, where
$D^{*-}_s\rightarrow D^-_s\gamma$ and $X$ represents additional pions from
fragmentation. The $D^-_s\!\rightarrow\!\ell^-\bar{\nu}_{\ell}$ events are
detected by full or partial reconstruction of the recoiling system
$DKX\gamma\ell$. The branching fraction measurements are combined to determine
the $D^-_s$ decay constant $f_{D_s} = (258.6 \pm 6.4 \pm 7.5)$ MeV, where the
first uncertainty is statistical and the second is systematic. | hep-ex |
Searches for 25 rare and forbidden decays of $D^+$ and $D_s^+$ mesons: A search is performed for rare and forbidden charm decays of the form
$D_{(s)}^+ \to h^\pm \ell^+ \ell^{(\prime)\mp}$, where $h^\pm$ is a pion or
kaon and $\ell^{(')\pm}$ is an electron or muon. The measurements are performed
using proton-proton collision data, corresponding to an integrated luminosity
of $1.6\text{fb}^{-1}$, collected by the LHCb experiment in 2016. No evidence
is observed for the 25 decay modes that are investigated and $90\%$ confidence
level limits on the branching fractions are set between $1.4\times10^{-8}$ and
$6.4\times10^{-6}$. In most cases, these results represent an improvement on
existing limits by one to two orders of magnitude. | hep-ex |
Production of electroweak bosons in association with jets with the ATLAS
detector: This report summarises studies of associated production of electroweak gauge
bosons and jets in proton-proton collisions at LHC with center of mass energy
of 8 and 13 TeV. It is based on a selection of results published by the ATLAS
Collaboration in the first half of 2017. | hep-ex |
Properties of Weakly-decaying Bottom Baryons, Xi_b^- and Omega_b^-, at
CDF: We present properties of weakly decaying bottom baryons, Xi_b and Omega_b,
using 4.2 fb^-1 of data from p-pbar collisions at sqrt{s}=1.96 TeV, and
recorded with the Collider Detector at Fermilab. We report the observation of
the Omega_b through the decay chain Omega_b -> J/psi Omega^-, where J/psi ->
mu^+ mu^-, Omega^- -> Lambda K^-, and Lambda -> p pi^-. Significance of the
observed signal is estimated to be 5.5 Gaussian standard deviations. The
Omega_b mass and lifetime are measured to be 6054.4 +- 6.8 (stat.) +- 0.9
(syst.) MeV/c^2 and 1.13^{+0.53}_{-0.40}(stat.) +- 0.02(syst.) ps,
respectively. In addition, the mass and lifetime of the Xi_b baryon are
measured to be 5790.9 +- 2.6(stat.) +- 0.8(syst.) MeV/c^2 and
1.56^{+0.27}_{-0.25}(stat.) +- 0.02(syst.) ps, respectively. Under the
assumption that the Xi_b and Omega_b are produced with similar kinematic
distributions as the Lambda_b baryon, we measure
\sigma.Br(Xi_b -> J/psi Xi^-)/\sigma.Br(Lambda_b -> J/Psi Lambda) = 0.167
^{+0.037}_{-0.025}(stat.) +- 0.012(syst.) and \sigma.Br(Omega_b -> J/psi
Omega^-)/\sigma.Br(Lambda_b -> J/Psi Lambda) = 0.045 ^{+0.017}_{-0.012}(stat.)
+- 0.004(syst.) for baryons produced with transverse momentum in the range of 6
- 20 GeV/c. | hep-ex |
Top cross section measurements at ATLAS: Measurements of the production cross section of top-quark pairs ($t\bar t$)
in $pp$ collisions at $\sqrt{s}$ = 7 TeV are presented using 35 \ipb\ of data
recorded with the ATLAS detector at the Large Hadron Collider. Events are
selected in the single lepton (electron or muon) and dilepton topologies with
multi-jets, and large missing transverse energy. The result is $\sigma_{t\bar
t} = 180 \pm 9\,\mathrm{(stat.)} \pm15 \,\mathrm{(syst.)} \pm 6
\,\mathrm{(lumi.)\,pb}$, which agrees with the Standard Model prediction. | hep-ex |
Measurement of $CP$ asymmetry in $B_s^0 \to D_s^{\mp} K^{\pm}$ decays: We report the measurements of the $CP$-violating parameters in $B_s^0 \to
D_s^{\mp} K^{\pm}$ decays observed in $pp$ collisions, using a data set
corresponding to an integrated luminosity of $3.0\,\text{fb}^{-1}$ recorded
with the LHCb detector. We measure $C_f = 0.73 \pm 0.14 \pm 0.05$, $A^{\Delta
\Gamma}_f = 0.39 \pm 0.28 \pm 0.15$, $A^{\Delta \Gamma}_{\overline{f}} = 0.31
\pm 0.28 \pm 0.15$, $S_f = -0.52 \pm 0.20 \pm 0.07$, $S_{\overline{f}} = -0.49
\pm 0.20 \pm 0.07$, where the uncertainties are statistical and systematic,
respectively. These parameters are used together with the world-average value
of the $B_s^0$ mixing phase, $-2\beta_s$, to obtain a measurement of the CKM
angle $\gamma$ from $B_s^0 \to D_s^{\mp} K^{\pm}$ decays, yielding $\gamma =
(128\,_{-22}^{+17})^\circ$ modulo $180^\circ$, where the uncertainty contains
both statistical and systematic contributions. This corresponds to
$3.8\,\sigma$ evidence for $CP$ violation in the interference between decay and
decay after mixing. | hep-ex |
Event Shapes and Power Corrections in ep DIS: Deep-inelastic ep scattering data, taken with the H1 detector at HERA, are
used to study the event shape variables thrust, jet broadening, jet mass, C
parameter, and two kinds of differential two-jet rates over a large range of
``relevant energy'' Q between 7 GeV and 100 GeV. The Q dependence of the mean
values is fit to second order calculations of perturbative QCD applying power
law corrections proportional to 1/Q^p to account for hadronization effects. The
concept of these power corrections is tested by a systematic investigation in
terms of a non-perturbative parameter alpha_{p-1} and the strong coupling
constant. | hep-ex |
Physics in the tau-charm Region at BESIII: The Beijing Spectrometer (BESIII) collaboration uses $e^+e^-$ collisions in
the tau-charm energy region to study a broad spectrum of topics. These include
studies of light mesons and light baryons, studies of charmonium, including
exotic mesons and baryons containing charmonium, studies of charmed mesons and
baryons, studies of QCD and tau physics, as well as searches for new physics.
The following is a Snowmass white paper that outlines the BESIII
accomplishments and potential in each of these areas. | hep-ex |
Search for pair-produced three-jet resonances in proton-proton
collisions at $\sqrt{s} =$ 13 TeV: A search has been performed for pair-produced resonances decaying into three
jets. The proton-proton collision data used for this analysis were collected
with the CMS detector in 2016 at a center-of-mass energy of 13 TeV and
correspond to an integrated luminosity of 35.9 fb$^{-1}$. The mass range from
200 to 2000 GeV is explored in four separate mass regions. The observations
show agreement with standard model expectations. The results are interpreted
within the framework of $R$-parity violating SUSY, where pair-produced gluinos
decay to a six quark final state. Gluino masses below 1500 GeV are excluded at
95% confidence level. An analysis based on data with multijet events
reconstructed at the trigger level extends the reach to masses as low as 200
GeV. Improved analysis techniques have led to enhanced sensitivity, allowing
the most stringent limits to date to be set on gluino pair production. | hep-ex |
Searching for diboson resonances in the boosted all-hadronic final state
at $\sqrt{\rm{s}}=13$ TeV with CMS: This article summarises three searches for diboson resonances in the
all-hadronic final state using data collected at a center-of-mass energy of
$\sqrt{\rm{s}}=13$ TeV with the CMS experiment at the CERN LHC. The boson decay
products are contained in one large-radius jet, resulting in dijet final states
which are resolved using jet substructure techniques. The analyses presented
use 2.3, 35.9 and 77.3 inverse femtobarns of data collected between 2015 and
2017. These include the first search for diboson resonances using data
collected at a 13 TeV collision energy, the introduction of a new algorithm to
tag vector bosons in the context of analyzing the data collected in 2016, and
the development of a novel multidimensional fit improving on the sensitivity of
the previous search method with up to $30\%$. The results presented here are
the most sensitive to date of diboson resonance searches in the dijet final
state. An emphasis on improvements in technique for vector boson tagging is
made. | hep-ex |
Experimental Prospects for CP and T Violation Studies in Charm: We present the current status of experimental results and prospects for the
determination of CP and T violation in the charm sector. Such measurements have
acquired renewed interest in recent years in view of theoretical work, which
has highlighted the possibility to probe experimental signatures from New
Physics beyond the Standard Model, since the effect of CP violation due to
Standard Model processes is expected to be highly suppressed in D decays. The
current limits of experimental sensitivities for these studies are reaching the
interesting theoretical regimes. We include new measurements from the Belle,
BABAR, and CLEO-c collaborations. | hep-ex |
Electroweak penguin decays at LHCb: Promising ways to search for New Physics effects in radiative penguin decays
are in the angular analysis of $B_{d} \rightarrow K^{*0} \mu^{+}\mu^{-}$, in
the measurement of direct CP violation in $\B_{d} \rightarrow
K^{*0}\mu^{+}\mu^{-}$ and a time dependent analysis of $B_{s} \rightarrow \phi
\gamma$. All of these studies are being pursued at LHCb. First results will be
shown from the 2010 and early 2011 data, with particular emphasis on $B_{d}
\rightarrow K^{*0} \mu^{+}\mu^{-}$. | hep-ex |
Recent results on nucleon resonance electrocouplings from the studies of
$π^{+}π^{-}p$ electroproduction with the CLAS detector: Recent results on nucleon resonance studies in $\pi^{+}\pi^{-}p$ electro-
production off protons with the CLAS detector are presented. The analysis of
CLAS data allowed us to determine all essential contributing mechanisms,
providing a credible separation between resonant and non-resonant parts of the
cross sections in a wide kinematical area of invariant masses of the final
hadronic system $1.3<W<1.8$ GeV and photon virtualities $0.2<Q^{2}<1.5$
$GeV^2$. Electrocouplings of several excited proton states with masses less
than 1.8 GeV were obtained for the first time from the analysis of
$\pi^{+}\pi^{-}p$ exclusive electroproduction channel. | hep-ex |
Measurement of Branching Fractions for B->ππ, Kπand KK Decays: We report measurements of the branching fractions for $B^0\to\pi^+\pi^-$,
$K^+\pi^-$, $K^+K^-$ and $K^0\pi^0$, and $B^+\to\pi^+\pi^0$, $K^+\pi^0$,
$K^0\pi^+$ and $K^+\bar{K}{}^0$. The results are based on 10.4 fb$^{-1}$ of
data collected on the $\Upsilon$(4S) resonance at the KEKB $e^+e^-$ storage
ring with the Belle detector, equipped with a high momentum particle
identification system for clear separation of charged $\pi$ and $K$ mesons. We
find ${\cal B}(B^0\to\pi^+\pi^-) =(0.56^{+0.23}_{-0.20}\pm 0.04)\times
10^{-5}$, ${\cal B}(B^0\to K^+\pi^-) =(1.93^{+0.34 +0.15}_{-0.32 -0.06})\times
10^{-5}$, ${\cal B}(B^+\to K^+\pi^0) =(1.63^{+0.35 +0.16}_{-0.33 -0.18})\times
10^{-5}$, ${\cal B}(B^+\to K^0\pi^+) =(1.37^{+0.57 +0.19}_{-0.48 -0.18})\times
10^{-5}$, and ${\cal B}(B^0\to K^0\pi^0) =(1.60^{+0.72 +0.25}_{-0.59
-0.27})\times 10^{-5}$, where the first and second errors are statistical and
systematic. We also set upper limits of ${\cal B}(B^+\to\pi^+\pi^0)<1.34\times
10^{-5}$, ${\cal B}(B^0\to K^+K^-)<0.27\times 10^{-5}$, and ${\cal B}(B^+\to
K^+\bar{K}{}^0)<0.50\times 10^{-5}$ at the 90% confidence level. | hep-ex |
Measurement of B(Y(nS) -> mu+ mu-) at CLEO: The decay branching fractions of the three narrow Upsilon resonances to mu+
mu- have been measured by analyzing about 4.3 1/fb e+e- data collected with the
CLEO III detector. The branching fraction B(Y(1S) -> mu+ mu-) = (2.49 +- 0.02
+- 0.07)% is consistent with the current world average but B(Y(2S) -> mu+ mu-)
= (2.03 +- 0.03 +- 0.08)% and B(Y(3S) -> mu+ mu-) = (2.39 +- 0.07 +- 0.10)% are
significantly larger than prior results. These new muonic branching fractions
imply a narrower total decay width for the Y(2S) and Y(3S) resonances and lower
other branching fractions that rely on these decays in their determination. | hep-ex |
Time-dependent CP asymmetries in Bs decays at LHCb: The LHCb experiment will search for New Physics in Bs mixing. The Bs mixing
phase will be extracted from the measurement of the time-dependent CP asymmetry
in exclusive Bs decays governed by the b -> ccbar s quark-level transition.
Large New Physics effects can be discovered or excluded with the data collected
during the very first physics run of LHC. Based on Monte Carlo simulations of
the LHCb detector, the expected sensitivity with 2 inverse fb on the
CP-violation parameter phi_s is sigma(phi_s) = 0.022. | hep-ex |
Study of Upsilon(3S,2S) -> eta Upsilon(1S) and Upsilon(3S,2S) -> pi+pi-
Upsilon(1S) hadronic trasitions: We study the Upsilon(3S,2S)->eta Upsilon(1S) and Upsilon(3S,2S)->pi+pi-
Upsilon(1S) transitions with 122 million Upsilon(3S) and 100 million
Upsilon(2S) mesons collected by the BaBar detector at the PEP-II asymmetric
energy e+e- collider. We measure B[Upsilon(2S)->eta
Upsilon(1S)]=(2.39+/-0.31(stat.)+/-0.14(syst.))10^-4 and Gamma[Upsilon(2S)->eta
Upsilon(1S)]/Gamma[Upsilon(2S)-> pi+pi-
Upsilon(1S)]=(1.35+/-0.17(stat.)+/-0.08(syst.))10^-3. We find no evidence for
Upsilon(3S)->eta Upsilon(1S) and obtain B[Upsilon(3S)->eta Upsilon(1S)]<1.0
10^-4 and Gamma[Upsilon(3S)->eta Upsilon(1S)]/Gamma[Upsilon(3S)->pi+pi-
Upsilon(1S)]<2.3 10^-3 as upper limits at the 90% confidence level. We also
provide improved measurements of the Upsilon(2S) - Upsilon(1S) and Upsilon(3S)
- Upsilon(1S) mass differences, 562.170+/-0.007(stat.)+/-0.088(syst.) MeV/c^2
and 893.813+/-0.015(stat.)+/-0.107(syst.) MeV/c^2 respectively. | hep-ex |
Event Structure and Double Helicity Asymmetry in Jet Production from
Polarized p+p Collisions at sqrt(s) = 200 GeV: We report on event structure and double helicity asymmetry ($A_LL$) of jet
production in longitudinally polarized p+p collisions at $\sqrt{s}$=200 GeV.
Photons and charged particles were measured at midrapidity $|\eta| < 0.35$ with
the requirement of a high-momentum ($>2$ GeV/$c$) photon in each event.
Measured event structure is compared with {\sc pythia} and {\sc geant}
simulations. The shape of jets and the underlying event were well reproduced at
this collision energy. For the measurement of jet $A_{LL}$, photons and charged
particles were clustered with a seed-cone algorithm to obtain the cluster $p_T$
sum ($p_T^{\rm reco}$). The effect of detector response and the underlying
events on $p_T^{\rm reco}$ was evaluated with the simulation. The production
rate of reconstructed jets is satisfactorily reproduced with the NLO pQCD jet
production cross section. For $4 < p_T^{\rm reco} < 12$ GeV/$c$ with an average
beam polarization of $< P > = 49%$ we measured $A_{LL} = -0.0014 \pm
0.0037^{\rm stat}$ at the lowest $p_T^{\rm reco}$ bin (4-5 GeV/$c$) and
$-0.0181 \pm 0.0282^{\rm stat}$ at the highest $p_T^{\rm reco}$ bin (10-12
GeV/$c$) with a beam polarization scale error of 9.4% and a $\pT$ scale error
of 10%. Jets in the measured $p_T^{\rm reco}$ range arise primarily from
hard-scattered gluons with momentum fraction $0.02 < x < 0.3$ according to {\sc
pythia}. The measured $A_{LL}$ is compared with predictions that assume various
$\Delta G(x)$ distributions based on the GRSV parameterization. The present
result imposes the limit $-1.1 < \int_{0.02}^{0.3}dx \Delta G(x, \mu^2 = 1 {\rm
GeV}^2) < 0.4$ at 95% confidence level or $\int_{0.02}^{0.3}dx \Delta G(x,
\mu^2 = 1 {\rm GeV}^2) < 0.5$ at 99% confidence level. | hep-ex |
The Status and Prospects of the Muon $g-2$ Experiment at Fermilab: The E989 Muon $g-2$ Experiment at Fermilab aims to measure the muon magnetic
anomaly, $a_\mu$, to an unprecedented precision of 140 parts per billion (ppb),
representing a four-fold improvement over the current best measurement,
achieved at Brookhaven National Lab. There stands a greater than 3 standard
deviations discrepancy between the Brookhaven measurement of $a_\mu$ and the
theoretical value predicted using the Standard Model. The Fermilab experiment
seeks to either resolve or confirm this discrepancy, which is suggestive of new
physics interactions. To achieve the E989 target precision, the anomalous
precession frequency of muons in a magnetic storage ring must be determined
with a systematic uncertainty below 70\,ppb, and the average magnetic field
experienced by these stored muons must be known equally well. The muon
anomalous precession frequency is imprinted on the time-dependent energy
distribution of decay positrons observed by 24 electromagnetic calorimeters. A
suite of pulsed NMR probes continually monitors the magnetic field. This
document presents the current status of the Fermilab experiment while
emphasizing the ongoing analysis of the 2018 Run 1 dataset and the systematic
effects that complicate it. | hep-ex |
Measurement of Event Shapes in Proton-Antiproton Collisions at
Center-of-Mass Energy 1.96 TeV: A study of event shape observables in proton-antiproton collisions at 1.96
TeV is presented. The data for this analysis were recorded by the CDF II
detector at the Tevatron collider. The variables studied are the transverse
thrust and thrust minor, both defined in the plane perpendicular to the beam
direction. The observables are measured using energies from unclustered
calorimeter cells. In addition to studies of the differential distributions, we
present the dependence of event shape mean values on the leading jet transverse
energy. Data are compared with pythia Tune A and to resummed parton level
predictions that were matched to fixed order results at NLO accuracy (NLO+NLL).
Predictions from pythia Tune A agree fairly well with the data. However, the
underlying event contributes significantly to these observables, making it
difficult to make direct comparisons to the NLO+NLL predictions, which do not
account for the underlying event. To overcome this difficulty, we introduce a
new observable, a weighted difference of the mean values of the thrust and
thrust minor, which is less sensitive to the underlying event, allowing for a
comparison with NLO+NLL. Both pythia Tune A and the NLO+NLL calculations agree
well within the 20% theoretical uncertainty with the data for this observable,
indicating that perturbative QCD successfully describes shapes of the hadronic
final states. | hep-ex |
Hunting for Axionlike Dark Matter by Searching for an Oscillating
Neutron Electric Dipole Moment: We report on a search for ultra-low-mass axion-like dark matter by analysing
the ratio of the spin-precession frequencies of stored ultracold neutrons and
$^{199}$Hg atoms for an axion-induced oscillating electric dipole moment of the
neutron and an axion-wind spin-precession effect. No signal consistent with
dark matter is observed for the axion mass range $10^{-24}~\textrm{eV} \le m_a
\le 10^{-17}~\textrm{eV}$. Our null result sets the first laboratory
constraints on the coupling of axion dark matter to gluons, which improve on
astrophysical limits by up to 3 orders of magnitude, and also improves on
previous laboratory constraints on the axion coupling to nucleons by up to a
factor of 40. The results were initially presented in Phys. Rev. X 7, 041034,
of which this proceeding is largely a summary. | hep-ex |
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