text
stringlengths 89
2.49k
| category
stringclasses 19
values |
|---|---|
Interpretation of Scalar and axial mesons in LHCb from an historical
perspective: LHCb measurements of $B_{d,s} \to J/\psi + X$ are shown to be consistent with
historical data on scalar and axial mesons below 2 GeV. This is in contrast to
some recent interpretations of these data. Further tests of our hypotheses in
other $B_{u,d,s} \to J/\psi + X$ decay modes are suggested. | hep-ex |
Search for Factorization-Suppressed B -> chi_c K(*) Decays: We search for the factorization-suppressed decays B -> chi_c0 K(*) and B ->
chi_c2 K(*), with chi_c0 and chi_c2 decaying into J/psi gamma using a sample of
124 10^6 BBbar events collected with the BABAR detector at the PEP-II storage
ring of the Stanford Linear Accelerator Center. | hep-ex |
Study of Top-quark Production and Decay Vertices with LCD Fast
Simulation: We report a study of top-quark reconstruction in $e^+e^- \rightarrow
t\bar{t}$ events at a 500 GeV linear collider using the LCD Fast simulator. The
initial study of top-quark anomalous couplings is also reported. The final
states of 4 jets and lepton as well as 6 jets are used. Using the 4 jets and
lepton final state, we estimate the preliminary sensitivities for form factors
at the $\gamma/Z^0 t\bar{t}$ vertex. In the 6 jets reconstruction, we show
abilities of the top-quark charge identification and the $c$-quark tagging in W
decays. | hep-ex |
Evaluation of the LEP Centre-of-Mass Energy Above the W-Pair Production
Threshold: Knowledge of the centre-of-mass energy at LEP2 is of primary importance to
set the absolute energy scale for the measurement of the W-boson mass. The beam
energy above 80 GeV is derived from continuous measurements of the magnetic
bending field by 16 NMR probes situated in a number of the LEP dipoles. The
relationship between the fields measured by the probes and the beam energy is
calibrated against precise measurements of the average beam energy between 41
and 55 GeV made using the resonant depolarisation technique. The linearity of
the relationship is tested by comparing the fields measured by the probes with
the total bending field measured by a flux loop. This test results in the
largest contribution to the systematic uncertainty. Several further corrections
are applied to derive the the centre-of-mass energies at each interaction
point. In addition the centre-of-mass energy spread is evaluated. The beam
energy has been determined with a precision of 25 MeV for the data taken in
1997, corresponding to a relative precision of 2.7x10^{-4}. This is small in
comparison to the present uncertainty on the W mass measurement at LEP.
However, the ultimate statistical precision on the W mass with the full LEP2
data sample should be around 25 MeV, and a smaller uncertainty on the beam
energy is desirable. Prospects for improvements are outlined. | hep-ex |
Global search for new physics at CDF: A model-independent global search for new physics has been performed at the
CDF experiment. This search examines 399 final states, looking for
discrepancies between observation and the standard model expectation in
populations, kinematic shapes, bumps in mass distributions suggestive of new
resonances and the tails of the summed transverse momentum distribution. This
global search reveals no evidence of physics beyond the Standard Model in 2.0
fb^-1 of p-pbar collisions at sqrt(s)=1.96 TeV. | hep-ex |
Evidence for the associated production of the Higgs boson and a top
quark pair with the ATLAS detector: A search for the associated production of the Higgs boson with a top quark
pair ($t\bar t H$) is reported. The search is performed in multilepton final
states using a dataset corresponding to an integrated luminosity of 36.1
fb$^{-1}$ of proton--proton collision data recorded by the ATLAS experiment at
a center-of-mass energy $\sqrt{s} = 13$ TeV at the Large Hadron Collider. Higgs
boson decays to $WW^*$, $\tau\tau$, and $ZZ^*$ are targeted. Seven final
states, categorized by the number and flavor of charged-lepton candidates, are
examined for the presence of the Standard Model Higgs boson with a mass of 125
GeV and a pair of top quarks. An excess of events over the expected background
from Standard Model processes is found with an observed significance of 4.1
standard deviations, compared to an expectation of 2.8 standard deviations. The
best fit for the $t\bar t H$ production cross section is $\sigma(t\bar t H) =
790^{+230}_{-210}$ fb, in agreement with the Standard Model prediction of
$507^{+35}_{-50}$ fb. The combination of this result with other $t\bar t H$
searches from the ATLAS experiment using the Higgs boson decay modes to $b\bar
b$, $\gamma\gamma$ and $ZZ^* \to 4\ell$, has an observed significance of 4.2
standard deviations, compared to an expectation of 3.8 standard deviations.
This provides evidence for the $t\bar t H$ production mode. | hep-ex |
Measurement of CP-violating asymmetries in B^0 -> (rho pi)^0 decays
using a time-dependent Dalitz plot analysis: We present results for a time-dependent Dalitz plot measurement of
CP-violating asymmetries in the mode B^0 -> pi^+ pi^- pi^0. The dataset is
derived from the complete sample of 471 x 10^6 BBbar meson pairs collected with
the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at the SLAC
National Accelerator Laboratory operating on the Upsilon(4S) resonance. We
extract parameters describing the time-dependent B^0 -> rho pi decay
probabilities and CP asymmetries, including C = 0.016\pm0.059\pm0.036, DeltaC =
0.234\pm0.061\pm0.048, S = 0.053\pm0.081\pm0.034, and DeltaS =
0.054\pm0.082\pm0.039, where the uncertainties are statistical and systematic,
respectively. We perform a two-dimensional likelihood scan of the direct
CP-violation asymmetry parameters for B^0 -> rho^\pm pi^\mp decays, finding the
change in chi^2 between the minimum and the origin (corresponding to no direct
CP violation) to be Delta(chi^2)=6.42. We present information on the
CP-violating parameter alpha in a likelihood scan that incorporates B^\pm ->
rho pi measurements. | 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 |
Search for Standard Model Higgs in WH->lvbb at the Tevatron: We present a search for the Standard Model Higgs boson produced in
association with a W boson in $p\bar{p}$ collisions at a center-of-mass energy
of $\sqrt{s} = 1.96$ TeV. The search is performed in the $WH\to \ell\nu
b\bar{b}$ channel using 2.7 fb$^{-1}$ of data collected by both the CDF
detector and by the $D\O$ detector, at the Fermilab Tevatron. The searches
employ artificial neural network, matrix element and boosted decision tree
techniques to improve the separation between signal and background. Additional
techniques used to improve the Higgs sensitivity include the use of optimized
b-quark jet energy corrections and improved algorithms for identifying
b-quarks. In the absence of an observed excess in data, upper limits are set by
both experiments on the Higgs production rate times branching ratio for a range
of possible Higgs masses between 100 and 150 GeV. | hep-ex |
A search for flavor-changing non-standard neutrino interactions by MINOS: We report new constraints on flavor-changing non-standard neutrino
interactions (NSI) using data from the MINOS experiment. We analyzed a combined
set of beam neutrino and antineutrino data, and found no evidence for
deviations from standard neutrino mixing. The observed energy spectra constrain
the NSI parameter to the range $-0.20 < \varepsilon_{\mu\tau} <
0.07\;\text{(90% C.L.)}$ | hep-ex |
Observation of $D^+\toηηπ^+$ and improved measurement of
$D^{0(+)}\toηπ^+π^{-(0)}$: Using an $e^+e^-$ annihilation data sample corresponding to an integrated
luminosity of $2.93\,\rm fb^{-1}$ collected at the center-of-mass energy of
3.773\,GeV with the BESIII detector, we measure the absolute branching
fractions of $D^+\to\eta\eta\pi^+$, $D^+\to\eta\pi^+\pi^0$, and
$D^0\to\eta\pi^+\pi^-$ to be $(2.96 \pm 0.24 \pm 0.13)\times 10^{-3}$, $(2.23
\pm 0.15 \pm 0.11)\times 10^{-3}$, and $(1.20 \pm 0.07 \pm 0.04)\times
10^{-3}$, respectively, where the first uncertainties are statistical and the
second ones systematic. The $D^+\to\eta\eta\pi^+$ decay is observed for the
first time and the branching fractions of $D^{+(0)}\to\eta\pi^+\pi^{0(-)}$ are
measured with much improved precision. In addition we test for $CP$ asymmetries
in the separated charge-conjugate branching fractions; no evidence of $CP$
violation is found. | hep-ex |
Search for the charged lepton flavor violating decay $J/ψ\to eτ$: A search for the charged lepton flavor violating decay $J/\psi\to
e^{\pm}\tau^{\mp}$ with $\tau^{\mp} \to \pi^{\mp}\pi^0\nu_{\tau}$ is performed
with about $10$ billion $J/ \psi$ events collected with the BESIII detector at
the BEPCII. No significant signal is observed, and an upper limit is set on the
branching fraction $\mathcal{B}(J/\psi\to e^{\pm}\tau^{\mp})<7.5\times10^{-8}$
at the 90$\%$ confidence level. This improves the previously published limit by
two orders of magnitude. | hep-ex |
High momentum particle and jet production in photon-photon collisions: Jet and particle production have been studied in collisions of quasi-real
photons collected during the LEP2 program. OPAL and DELPHI report good
agreement of NLO perturbative QCD with the measured differential di-jet cross
sections, which reach a mean transverse energy of the di-jet system of 25 GeV.
L3, on the other hand, finds drastic disagreement of the same calculation with
single jet production for transverse jet momenta larger than about 25 GeV. L3
observes similar disagreement between data and NLO QCD in their measurements of
charged and neutral particle production at high transverse momenta of the
particles. A recent measurement performed by DELPHI of the same quantities does
not confirm this observation. | hep-ex |
Double Helicity Asymmetries of Forward Neutral Pions from $\sqrt{s}=510$
GeV $pp$ Collisions at STAR: Longitudinally polarized $p+p$ scattering experiments provide access to gluon
polarization via measurement of the double helicity asymmetry, $A_{LL}$. At the
completion of the 2013 RHIC running period, a significant dataset of $\pi^{0}$s
corresponding to an integrated luminosity of 46 $\text{pb}^{-1}$ (2012) and 8
$\text{pb}^{-1}$ (2013) produced from polarized $p+p$ scattering at
$\sqrt{s}=510$ GeV with an average beam polarization of approximately $50\%$
was acquired. The $\pi^{0}$ kinematics were measured via isolation cones by the
STAR Forward Meson Spectrometer, an electromagnetic calorimeter covering a
forward pseudorapidity range of $2.6 < \eta <4$. The asymmetric $qg \to qg$
subprocess becomes more dominant in this forward region than in the midrapidity
region; furthermore, asymmetry measurements in the forward region are sensitive
to low-$x$ gluons. Progress on $A_{LL}$ determined from forward $\pi^{0}$
events, complementing previous midrapidity measurements, are presented. | hep-ex |
Study of di-pion bottomonium transitions and search for the h_b(1P)
state: We study inclusive di-pion decays using a sample of 108 x 10^6 Upsilon(3S)
events recorded with the BABAR detector. We search for the decay mode
Upsilon(3S) --> pi+ pi- h_b(1P) and find no evidence for the bottomonium
spin-singlet state h_b(1P) in the invariant mass distribution recoiling against
the pi+ pi- system. Assuming the h_b(1P) mass to be 9.900 GeV/c^2, we measure
the upper limit on the branching fraction B[Upsilon(3S) --> pi+ pi- h_b(1P)] <
1.2 x 10^{-4}, at 90% confidence level. We also investigate the chi_{bJ}(2P)
--> pi+ pi- chi_{bJ}(1P), Upsilon(3S) --> pi+ pi- Upsilon(2S), and Upsilon(2S)
--> pi+ pi- Upsilon(1S) di-pion transitions and present an improved measurement
of the branching fraction of the Upsilon(3S) --> pi+ pi- Upsilon(2S) decay and
of the Upsilon(3S)-Upsilon(2S) mass difference. | hep-ex |
Measuring the tau polarization at ILC: Measurement of the tau lepton polarization in \eett\ is an important
electro-weak measurement at ILC and other future electron-positron colliders.
In this paper we discuss several methods to extract polarimeter information for
\eett\ events at the nominal centre-of-mass energy, and develop a new method,
based on charged particle impact parameter measurement, which can accurately
reconstruct tau momenta even in events with significant Initial State
Radiation.
In future work we will extend the study to estimate the precision with which
the tau polarization can be measured at ILC-250, both for high-mass tau pairs
and for those which radiatively return to the $Z^0$ peak. This will complement
our past study which showed that the tau polarization can be measured to better
than 1\% at the ILC-500. | hep-ex |
Review on reactor neutrino present and future: Nuclear reactors are an essential source of neutrinos. In this proceeding, I
review the past and current status of the research on neutrino oscillations
using reactor neutrinos. I also present a promising idea for positron tagging
that will potentially be a game-changer in the field. | hep-ex |
Heavy Flavour Physics at HERA: New results with increased statistics are presented for heavy flavour
production at Q2<150 Gev2 and in the photoproduction limit Q2-->0. Cross
sections for Dstar production, F2charm, the gluon density in the proton, and
inelastic J/psi production are discussed and compared to theoretical
calculations. A first measurement of the b anti-b cross section is reported. | hep-ex |
Time-Integrated Luminosity Recorded by the BABAR Detector at the PEP-II
e+e- Collider: We describe a measurement of the time-integrated luminosity of the data
collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider
at the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances and in a continuum
region below each resonance. We measure the time-integrated luminosity by
counting e+e- --> e+e- and (for the Upsilon(4S) only) e+e- --> mu+mu- candidate
events, allowing additional photons in the final state. We use data-corrected
simulation to determine the cross sections and reconstruction efficiencies for
these processes, as well as the major backgrounds. Due to the large cross
sections of e+e- --> e+e- and e+e- --> mu+mu-, the statistical uncertainties of
the measurement are substantially smaller than the systematic uncertainties.
The dominant systematic uncertainties are due to observed differences between
data and simulation, as well as uncertainties on the cross sections. For data
collected on the Upsilon(3S) and Upsilon(2S) resonances, an additional
uncertainty arises due to Upsilon --> e+e-X background. For data collected off
the Upsilon resonances, we estimate an additional uncertainty due to
time-dependent efficiency variations, which can affect the short off-resonance
runs. The relative uncertainties on the luminosities of the on-resonance
(off-resonance) samples are 0.43% (0.43%) for the Upsilon(4S), 0.58% (0.72%)
for the Upsilon(3S), and 0.68% (0.88%) for the Upsilon(2S). | hep-ex |
Introduction to HOBIT, a b-Jet Identification Tagger at the CDF
Experiment Optimized for Light Higgs Boson Searches: We present the development and validation of the Higgs Optimized b
Identification Tagger (HOBIT), a multivariate b-jet identification algorithm
optimized for Higgs boson searches at the CDF experiment at the Fermilab
Tevatron. At collider experiments, b taggers allow one to distinguish particle
jets containing B hadrons from other jets; these algorithms have been used for
many years with great success at CDF. HOBIT has been designed specifically for
use in searches for light Higgs bosons decaying via H ! b\bar{b}. This fact
combined with the extent to which HOBIT synthesizes and extends the best ideas
of previous taggers makes HOBIT unique among CDF b-tagging algorithms.
Employing feed-forward neural network architectures, HOBIT provides an output
value ranging from approximately -1 ("light-jet like") to 1 ("b-jet like");
this continuous output value has been tuned to provide maximum sensitivity in
light Higgs boson search analyses. When tuned to the equivalent light jet
rejection rate, HOBIT tags 54% of b jets in simulated 120 GeV/c2 Higgs boson
events compared to 39% for SecVtx, the most commonly used b tagger at CDF. We
present features of the tagger as well as its characterization in the form of
b-jet finding efficiencies and false (light-jet) tag rates. | hep-ex |
Measurement of top quark pair production in association with a Z boson
in proton-proton collisions at $\sqrt{s} =$ 13 TeV: A measurement of the inclusive cross section of top quark pair production in
association with a Z boson using proton-proton collisions at a center-of-mass
energy of 13 TeV at the LHC is performed. The data sample corresponds to an
integrated luminosity of 77.5 fb$^{-1}$, collected by the CMS experiment during
2016 and 2017. The measurement is performed using final states containing three
or four charged leptons (electrons or muons), and the Z boson is detected
through its decay to an oppositely charged lepton pair. The production cross
section is measured to be $\sigma(\mathrm{t\bar{t}Z})$ $=$ 0.95 $\pm$ 0.05
(stat) $\pm$ 0.06 (syst) pb. For the first time, differential cross sections
are measured as functions of the transverse momentum of the Z boson and the
angular distribution of the negatively charged lepton from the Z boson decay.
The most stringent direct limits to date on the anomalous couplings of the top
quark to the Z boson are presented, including constraints on the Wilson
coefficients in the framework of the standard model effective field theory. | hep-ex |
New results from VES: The results of the patial wave analysis(PWA) of the pi+pi-pi- and omegapi-pi0
systems are presented. The a3 and a4(2040) signals are observed in the
rho(770)pi and f2(1270)pi channels. Indications of the a1' meson existence was
found in the 1+0+ rhopi S-wave. The decay branching ratio of the a2(1320)- to
omegapi-pi0 was measured. The 2+1+ wave shows a broad bump at M~1.7GeV. The
decays of the pi2(1670), a4(2040) and pi(1740) into omegarho- were found. The
resonance in the b1(1235)pi wave with exotic quantum numbers jpc=1-+ at M~1.6
is observed and the simultaneous analysis of the 1-+ wave in the b1(1235)pi,
etha'pi and rhopi final states is presented. | hep-ex |
Averages of $b$-hadron, $c$-hadron, and $τ$-lepton properties as of
summer 2014: This article reports world averages of measurements of $b$-hadron,
$c$-hadron, and $\tau$-lepton properties obtained by the Heavy Flavor Averaging
Group (HFAG) using results available through summer 2014. For the averaging,
common input parameters used in the various analyses are adjusted (rescaled) to
common values, and known correlations are taken into account. The averages
include branching fractions, lifetimes, neutral meson mixing parameters, $CP$
violation parameters, parameters of semileptonic decays and CKM matrix
elements. | hep-ex |
Angular analysis of $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$: We present a measurement of angular observables, $P_4'$, $P_5'$, $P_6'$,
$P_8'$, in the decay $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$, where
$\ell^+\ell^-$ is either $e^+e^-$ or $\mu^+\mu^-$. The analysis is performed on
a data sample corresponding to an integrated luminosity of
$711~\mathrm{fb}^{-1}$ containing $772\times 10^{6}$ $B\bar B$ pairs, collected
at the $\Upsilon(4S)$ resonance with the Belle detector at the
asymmetric-energy $e^+e^-$ collider KEKB. Four angular observables,
$P_{4,5,6,8}'$ are extracted in five bins of the invariant mass squared of the
lepton system, $q^2$. We compare our results for $P_{4,5,6,8}'$ with Standard
Model predictions including the $q^2$ region in which the LHCb collaboration
reported the so-called $P_5'$ anomaly. | hep-ex |
Muon Decay Asymmetries from $K^0_L \to π^0 μ^+ μ^-$ Decays: We have examined the decay $K^0_L \to \pi^0 \mu^+ \mu^-$ in which the
branching ratio, the muon energy asymmetry and the muon decay asymmetry could
be measured. In particular, we find that within the Standard Model the
longitudinal polarization ($P_L$) of the muon is proportional to the direct CP
violating amplitude. On the other hand the energy asymmetry and the
out-of-plane polarization ($P_N$) depend on both indirect and direct CP
violating amplitudes. Although the branching ratio is small and difficult to
measure because of background, the asymmetries could be large $\cal{O}$(1) in
the Standard Model. A combined analysis of the energy asymmetry, $P_L$ and
$P_N$ could be used to separate indirect CPV, direct CPV, and CP conserving
contributions to the decay. | hep-ex |
Measurement of hard double-parton interactions with the ATLAS detector: The production of W boson in association with two jets in proton-proton
collisions at the LHC with a centre-of-mass energy of $\sqrt{s}$ = 7 TeV has
been investigated using data collected with the ATLAS detector. The fraction of
events arising from double-parton scattering has been measured through the
transverse momentum balance between the two jets. The measurement provides new
information on the scaling of the rate of double-parton scattering processes
and constraints on proton transverse profile modeling. | hep-ex |
Measurements of $A_{CP}(B^0\rightarrow K^+ π^-)$ and
$A_{CP}(B_s\rightarrow π^+ K^-)$ at LHCb: The LHCb experiment is designed to perform flavour physics measurements at
the Large Hadron Collider. Using data collected during the 2010 run, we
reconstruct a sample of $H_b\rightarrow h^+h'^-$ decays, where $H_b$ can be
either a $B^0$ meson, a $B_s^0$ meson or a $\Lambda_b$ baryon, while $h$ and
$h^\prime$ stand for $\pi$, $K$ or $p$. We provide preliminary values of the
direct $\mathcal{CP}$ asymmetries of the neutral $B^0$ and $B_s^0$ mesons
$A_{CP} (B^0\rightarrow K^+\pi^-) = -0.074 \pm 0.033\mathrm{(stat.)} \pm
0.008\mathrm{(syst.)}$ and $A_{CP}(B_s^0\rightarrow\pi^+K^-)=0.15 \pm
0.19\mathrm{(stat.)} \pm 0.02\mathrm{(syst.)}$. | hep-ex |
Simulations of neutron background in a time projection chamber relevant
to dark matter searches: Presented here are results of simulations of neutron background performed for
a time projection chamber acting as a particle dark matter detector in an
underground laboratory. The investigated background includes neutrons from rock
and detector components, generated via spontaneous fission and (alpha, n)
reactions, as well as those due to cosmic-ray muons. Neutrons were propagated
to the sensitive volume of the detector and the nuclear recoil spectra were
calculated. Methods of neutron background suppression were also examined and
limitations to the sensitivity of a gaseous dark matter detector are discussed.
Results indicate that neutrons should not limit sensitivity to WIMP-nucleon
interactions down to a level of (1 - 3) x 10^{-8} pb in a 10 kg detector. | hep-ex |
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 8:
Instrumentation Frontier: These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 8, on the Instrumentation Frontier,
discusses the instrumentation needs of future experiments in the Energy,
Intensity, and Cosmic Frontiers, promising new technologies for particle
physics research, and issues of gathering resources for long-term research in
this area. | hep-ex |
Probe of soft-QCD in minimum bias events of pp collisions with the ATLAS
at the LHC: The study of the minimum-bias charged-particle distributions is reviewed. The
data are obtained using the ATLAS detector at the LHC in proton-proton
collisions at the centre-of-mass energies from 0.9 to13 TeV. The particles are
required to have an absolute pseudorapidity less than 2.5. For charged-particle
distributions study two transverse momentum thresholds cases, greater than 100
MeV and 500 MeV were taken. The charged-particle multiplicity, its dependence
on the transverse momentum and pseudorapidity, dependence of the average
transverse momentum on the charged-particle multiplicity and the KNO-scaling
study are presented. The measured distributions are compared with the
predictions of various tunings of Monte Carlo generator, which implement
different minimum-bias models.The Monte Carlo model predictions qualitatively
describe the data well, but with some significant discrepancies. Measurements
of minimum-bias events by the ALICE and CMS Collaborations are presented. | hep-ex |
Measurement of the branching fractions for Cabibbo-suppressed decays
$D^{+}\to K^{+} K^{-}π^{+}π^{0}$ and $D_{(s)}^{+}\to
K^{+}π^{-}π^{+}π^{0}$ at Belle: We present measurements of the branching fractions for the singly
Cabibbo-suppressed decays $D^+\to K^{+}K^{-}\pi^{+}\pi^{0}$ and $D_s^{+}\to
K^{+}\pi^{-}\pi^{+}\pi^{0}$, and the doubly Cabibbo-suppressed decay $D^{+}\to
K^{+}\pi^{-}\pi^{+}\pi^{0}$, based on 980 ${\rm fb}^{-1}$ of data recorded by
the Belle experiment at the KEKB $e^{+}e^{-}$ collider. We measure these modes
relative to the Cabibbo-favored modes $D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}$ and
$D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0}$. Our results for the ratios of branching
fractions are $B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})/B(D^{+}\to
K^{-}\pi^{+}\pi^{+}\pi^{0}) = (11.32 \pm 0.13 \pm 0.26)\%$, $B(D^{+}\to
K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}) = (1.68 \pm
0.11\pm 0.03)\%$, and $B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D_s^{+}\to
K^{+}K^{-}\pi^{+}\pi^{0}) = (17.13 \pm 0.62 \pm 0.51)\%$, where the
uncertainties are statistical and systematic, respectively. The second value
corresponds to $(5.83\pm 0.42)\times\tan^4\theta_C$, where $\theta_C$ is the
Cabibbo angle; this value is larger than other measured ratios of branching
fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored
decay. Multiplying these results by world average values for $B(D^{+}\to
K^{-}\pi^{+}\pi^{+}\pi^{0})$ and $B(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})$
yields $B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})= (7.08\pm 0.08\pm 0.16\pm
0.20)\times10^{-3}$, $B(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})= (1.05\pm 0.07\pm
0.02\pm 0.03)\times10^{-3}$, and $B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}) =
(9.44\pm 0.34\pm 0.28\pm 0.32)\times10^{-3}$, where the third uncertainty is
due to the branching fraction of the normalization mode. The first two results
are consistent with, but more precise than, the current world averages. The
last result is the first measurement of this branching fraction. | hep-ex |
Observation of WZ Production: We report the first observation of the associated production of a W boson and
a Z boson. This result is based on 1.1 fb-1 of integrated luminosity from ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We observe 16 WZ candidates passing our event selection with
an expected background of 2.7 +/- 0.4 events. A fit to the missing transverse
energy distribution indicates an excess of events compared to the background
expectation corresponding to a significance equivalent to six standard
deviations. The measured cross section is sigma(ppbar -> WZ) =
5.0^{+1.8}_{-1.6} pb, consistent with the standard model expectation. | hep-ex |
Measurement of the $\boldsymbol{W}$ Boson Production Charge Asymmetry in
$\boldsymbol{p\bar{p}\rightarrow W+X \rightarrow eν+X}$ Events at
$\boldsymbol{\sqrt{s}=1.96}$ TeV: We present a measurement of the $W$ boson production charge asymmetry in
$p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center of mass energy
of 1.96 TeV, using 9.7 fb$^{-1}$ of integrated luminosity collected with the D0
detector at the Fermilab Tevatron Collider. The neutrino longitudinal momentum
is determined using a neutrino weighting method, and the asymmetry is measured
as a function of the $W$ boson rapidity. The measurement extends over wider
electron pseudorapidity region than previous results, and is the most precise
to date, allowing for precise determination of proton parton distribution
functions in global fits. | hep-ex |
Cross section measurement of $e^{+}e^{-} \to K_{S}^{0}K_{L}^{0}$ at
$\sqrt{s}=2.00-3.08~{\rm GeV}$: The cross sections of the process $e^{+}e^{-} \to K_{S}^{0}K_{L}^{0}$ are
measured at fifteen center-of-mass energies $\sqrt{s}$ from $2.00$ to
$3.08~{\rm GeV}$ with the BESIII detector at the Beijing Electron Positron
Collider (BEPCII). The results are found to be consistent with those obtained
by BaBar. A resonant structure around $2.2~{\rm GeV}$ is observed, with a mass
and width of $2273.7 \pm 5.7 \pm 19.3~{\rm MeV}/c^2$ and $86 \pm 44 \pm 51~{\rm
MeV}$, respectively, where the first uncertainties are statistical and the
second ones are systematic. The product of its radiative width
($\Gamma_{e^+e^-}$) with its branching fraction to $K_{S}^{0}K_{L}^{0}$
($Br_{K_{S}^{0}K_{L}^{0}}$) is $0.9 \pm 0.6 \pm 0.7~{\rm eV}$. | hep-ex |
Simultaneous measurements of the $t\bar{t}$, $W^+W^-$, and
$Z/γ^{*}\rightarrowττ$ production cross-sections in $pp$
collisions at $\sqrt{s} = 7$ TeV with the ATLAS detector: Simultaneous measurements of the $t\bar{t}$, $W^+W^-$, and
$Z/\gamma^{*}\rightarrow\tau\tau$ production cross-sections using an integrated
luminosity of $4.6\,\mathrm{fb}^{-1}$ of $pp$ collisions at $\sqrt{s} =
7\,\mathrm{TeV}$ collected by the ATLAS detector at the LHC are presented.
Events are selected with two high transverse momentum leptons consisting of an
oppositely charged electron and muon pair. The three processes are separated
using the distributions of the missing transverse momentum of events with zero
and greater than zero jet multiplicities. Measurements of the fiducial
cross-section are presented along with results that quantify for the first time
the underlying correlations in the predicted and measured cross-sections due to
proton parton distribution functions. These results indicate that the
correlated NLO predictions for $t\bar{t}$ and $Z/\gamma^{*}\rightarrow\tau\tau$
underestimate the data, while those at NNLO generally describe the data well.
The full cross-sections are measured to be $\sigma(t\bar{t}) = 181.2 \pm
2.8^{+9.7}_{-9.5} \pm 3.3 \pm 3.3\,\mathrm{pb}$, $\sigma(W^+W^-) = 53.3 \pm
2.7^{+7.3}_{-8.0} \pm 1.0 \pm 0.5\,\mathrm{pb}$, and
$\sigma(Z/\gamma^{*}\rightarrow\tau\tau) = 1174 \pm 24^{+72}_{-87} \pm 21 \pm
9\,\mathrm{pb}$, where the cited uncertainties are due to statistics,
systematic effects, luminosity and the LHC beam energy measurement,
respectively. The $W^+W^-$ measurement includes the small contribution from
Higgs boson decays, $H\rightarrow W^+W^-$. | hep-ex |
New Resonances and Meson Spectroscopy at BaBar and Belle: We present a short review on the recent progresses that have been made in
meson spectroscopy. We discuss the experimental discoveries made at the BaBar
and Belle experiments, as well as the possible interpretations of the new
resonances. | hep-ex |
Four-gap glass RPC as a candidate to a large area thin time-of-flight
detector: A four-gap glass RPC with 0.3mm gap size was tested with hadron beam as a
time-of-flight detector having a time resolution of ~ 100ps. A thickness of the
detector together with front-end electronics is ~ 12mm. Results on time
resolution dependently on a pad size are presented. This paper contains first
result on the timing RPC (with ~ 100ps resolution) having a strip read-out.
Study has been done within the HARP experiment (CERN-PS214) R&D work. A obtaned
data can be useful if a design of a large area thin timing detector has to be
done. | hep-ex |
Signal detection using biphotons and potential application in axion-like
particle search: This paper presents a new optical system for detecting light signals
associated with the change in incoming photon number. The system employs
quantum correlation of photon pairs created via spontaneous parametric
down-conversion (SPDC). The signal, if present, will perturb the flux of the
incident photon stream. The perturbed photon stream is first projected through
a birefringent crystal where SPDC occurs, converting a single high-energy
photon into a pair of low energy photons. The photons in each pair eventually
arrive at separate detectors. By examining the biphoton correlation using the
probability distribution of the photons at the detectors, which varies
depending on the displacement of the main pump photon stream and the change in
the number of photons, the small optical displacement of the photon stream and
its variance can be determined. The change in incident photon number, in other
words, the presence of light signal does not influence the average of the
measured optical displacement values. Nevertheless, the change in optical
displacement measurement variance when the number of incident photons has
changed detects the light signal. This optical setup enables the detection of
light signals with low noise and remarkably high precision and sensitivity
using quantum correlation. The proposed technique has potential application for
axion-like particle search in experimental high energy physics. | hep-ex |
Analytical considerations for optimal axion haloscope design: The cavity haloscope provides a highly sensitive method to search for dark
matter axions in the microwave regime. Experimental attempts to enhance the
sensitivity have focused on improving major aspects, such as producing strong
magnetic fields, increasing cavity quality factors, and achieving lowest
possible noise temperatures. Minor details, however, also need to be carefully
considered in realistic experimental designs. They are associated with
non-uniform magnetic fields over the detection volume, noise propagation under
attenuation and temperature gradients, and thermal disequilibrium in the cavity
system. We take analytical approaches to these topics and offer optimal
treatments for improved performance. | hep-ex |
Determination of |Vcb| using the semileptonic decay \bar{B}^0 -->
D^{*+}e^-\barν: We present a measurement of the Cabibbo-Kobayashi-Maskawa (CKM) matrix
element |Vcb| using a 10.2 fb^{-1} data sample recorded at the \Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric e^+e^- storage ring.
By extrapolating the differential decay width of the \bar{B}^0 -->
D^{*+}e^-\bar{\nu} decay to the kinematic limit at which the D^{*+} is at rest
with respect to the \bar{B}^0, we extract the product of |Vcb| with the
normalization of the decay form factor F(1), |Vcb |F(1)=
(3.54+/-0.19+/-0.18)x10^{-2}, where the first error is statistical and the
second is systematic. A value of |Vcb| = (3.88+/-0.21+/-0.20+/-0.19)x10^{-2} is
obtained using a theoretical calculation of F(1), where the third error is due
to the theoretical uncertainty in the value of F(1). The branching fraction
B(\bar{B}^0 --> D^{*+}e^-\bar{\nu}) is measured to be
(4.59+/-0.23+/-0.40)x10^{-2}. | hep-ex |
Charge Asymmetry in 1-1000 GeV Electromagnetic Showers and Possibility
of Its Measurementnt: For the high energy electromagnetic showers the thickness dependence of a)
the development of electron and positron components, b) the difference between
the secondary electron and positron numbers, c) the charge asymmetry of high
energy electromagnetic showers, as well as d) the spectral distributions of the
components at the shower maxima for various energies of primary particle
energies,1 - 1000 GeV were investigated employing GEANT Monte Carlo simulation
package. Using these simulation results it is discussed the possibility of
observation and study of the charge asymmetry with the help of a magnetic
spectrometer which is important for the current and future experiments on the
detection of radiowaves produced by high energy neutrinos. | hep-ex |
Search for scalar leptoquarks produced via $τ$-lepton-quark
scattering in pp collisions at $\sqrt{s}$ = 13 TeV: The first search for scalar leptoquarks produced in $\tau$-lepton-quark
collisions is presented. It is based on a set of proton-proton collision data
recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV
corresponding to an integrated luminosity of 138 fb$^{-1}$. The reconstructed
final state consists of a jet, significant missing transverse momentum, and a
$\tau$ lepton reconstructed through its hadronic or leptonic decays. Limits are
set on the product of the leptoquark production cross section and branching
fraction and interpreted as exclusions in the plane of the leptoquark mass and
the leptoquark-$\tau$-quark coupling strength. | hep-ex |
High luminosity fixed-target experiment at the LHC: By extracting the beam with a bent crystal or by using an internal gas
target, the multi-TeV proton and lead LHC beams allow one to perform the most
energetic fixed-target experiments ever and to study $pp$, $p$d and $p$A
collisions at $\sqrt{s_{NN}}=115$ GeV and Pb$p$ and PbA collisions at
$\sqrt{s_{NN}}=72$ GeV with high precision and modern detection techniques.
Such studies would address open questions in the domain of the nucleon and
nucleus partonic structure at high-$x$, quark-gluon plasma and, by using
longitudinally or transversally polarised targets, spin physics. In this paper,
we will review the technical solutions to obtain a high-luminosity fixed-target
experiment at the LHC and will discuss their possible implementations with the
ALICE and LHCb detectors. | hep-ex |
Snowmass 2021 Dark Matter Complementarity Report: The fundamental nature of Dark Matter is a central theme of the Snowmass 2021
process, extending across all Frontiers. In the last decade, advances in
detector technology, analysis techniques and theoretical modeling have enabled
a new generation of experiments and searches while broadening the types of
candidates we can pursue. Over the next decade, there is great potential for
discoveries that would transform our understanding of dark matter. In the
following, we outline a road map for discovery developed in collaboration among
the Frontiers. A strong portfolio of experiments that delves deep, searches
wide, and harnesses the complementarity between techniques is key to tackling
this complicated problem, requiring expertise, results, and planning from all
Frontiers of the Snowmass 2021 process. | hep-ex |
Determination of the QCD color factor ratio CA/CF from the scale
dependence of multiplicity in three jet events: I examine the determination of the QCD color factor ratio CA/CF from the
scale evolution of particle multiplicity in e+e- three jet events. I fit an
analytic expression for the multiplicity in three jet events to event samples
generated with QCD multihadronic event generators. I demonstrate that a one
parameter fit of CA/CF yields the expected result CA/CF=2.25 in the limit of
asymptotically large energies if energy conservation is included in the
calculation. In contrast, a two parameter fit of CA/CF and a constant offset to
the gluon jet multiplicity, proposed in a recent study, does not yield
CA/CF=2.25 in this limit. I apply the one parameter fit method to recently
published data of the DELPHI experiment at LEP and determine the effective
value of CA/CF from this technique, at the finite energy of the Z0 boson, to be
1.74+-0.03+-0.10, where the first uncertainty is statistical and the second is
systematic. | hep-ex |
Search for b--> u transitions in B- -> [K+pi-pi0]_D K-: We search for decays of a B meson into a neutral D meson and a kaon, with the
D meson decaying into K+pi-pi0. This final state can be reached through the b
--> c transition B- -> D0K- followed by the doubly Cabibbo-suppressed D0 -->
K+pi-pi0, or the b --> u transition B- --> D0bar K- followed by the
Cabibbo-favored D0bar --> K+ pi-pi0. The interference of these two amplitudes
is sensitive to the angle gamma of the unitarity triangle. We present
preliminary results based on 226 10^{6} e+e- --> Y(4s) --> BBbar events
collected with the BABAR detector at SLAC. We find no significant evidence for
these decays and we set a limit R_ADS =(BR(B- -->[K+pi-pi0]_D K-)+ BR(B- -->
[K-pi+pi0]_D K+))/(BR(B- -->[K-pi+pi0]_D K-)+ BR(B- --> [K+pi-pi0]_D K+))<0.039
at 95% confidence level, which we translate with a Bayesian approach into r_B =
|A(B- --> D0bar K-)|/|A(B- --> D0bar K-)| < 0.185 at 95% confidence level. | hep-ex |
Measurement of the $H \to γγ$ and $H \to ZZ^* \to 4 \ell$
cross-sections in $pp$ collisions at $\sqrt{s}=13.6$ TeV with the ATLAS
detector: The inclusive Higgs boson production cross-section is measured in the
di-photon and the $ZZ^* \to 4 \ell$ decay channels using 31.4 and 29.0
fb$^{-1}$ of $pp$ collision data respectively, collected with the ATLAS
detector at a centre-of-mass energy of $\sqrt{s}=13.6$ TeV. To reduce the model
dependence, the measurement in each channel is restricted to a particle-level
phase space that closely matches the channel's detector-level kinematic
selection, and it is corrected for detector effects. These measured fiducial
cross-sections are $\sigma_{\mathrm{fid},\gamma \gamma} = 76^{+14}_{-13}$ fb,
and $\sigma_{\mathrm{fid},4 \ell} = 2.80 \pm 0.74$ fb, in agreement with the
corresponding Standard Model predictions of $67.6 \pm 3.7 $ fb and $3.67 \pm
0.19 $ fb. Assuming Standard Model acceptances and branching fractions for the
two channels, the fiducial measurements are extrapolated to the full phase
space yielding total cross-sections of $\sigma(pp \to H) = 67^{+12}_{-11}$ pb
and $46 \pm 12$ pb at $13.6$ TeV from the di-photon and $ZZ^* \to 4 \ell$
measurements respectively. The two measurements are combined into a total
cross-section measurement of $\sigma(pp \to H)= 58.2 \pm 8.7$ pb, to be
compared with the Standard Model prediction of $\sigma(pp \to H)_\mathrm{SM} =
59.9 \pm 2.6 $ pb. | hep-ex |
Form Factor Fit for e^+e^- to pi^+pi^-pi^+pi^-: The cross section of e^+e^- to pi^+pi^-pi^+pi^- has been measured by BABAR
collaboration. We apply the theoretical cross section deduced from the extended
VMD (VectorMeson Dominance) model to fit these experimental data. The relevant
parameters and the isovector form factor are obtained | hep-ex |
Measurements of the 125 GeV Higgs boson at CMS: Results of the measurements of the 125 GeV Higgs boson properties with
proton-proton collision data at $\sqrt{s}=13$ TeV collected by CMS detector are
presented. The used Higgs boson decay channels include the five major decay
modes, $\mathrm{H}\rightarrow\gamma\gamma$, $\mathrm{H}\rightarrow{\rm Z}{\rm
Z}\rightarrow4\ell$, $\mathrm{H}\rightarrow{\rm W}{\rm
W}\rightarrow\ell\nu\ell\nu$, $\mathrm{H}\rightarrow\tau^{+}\tau^{-}$ and
$\mathrm{H}\rightarrow b\bar{b}$, and two rare decay modes,
$\mathrm{H}\rightarrow\mu^{+}\mu^{-}$ and $\mathrm{H}\rightarrow{\rm
Z}/\gamma^{*}+\gamma\rightarrow\ell\ell\gamma$, with $\ell={\rm e},\mu$. The
measured Higgs boson properties include its mass, signal strength relative to
the standard model prediction, signal strength modifiers for different Higgs
boson production modes, coupling modifiers to fermions and bosons, effective
coupling modifiers to photons and gluons, simplified template cross sections,
fiducial cross sections. All results are consistent, within their
uncertainties, with the expectations for the Standard Model Higgs boson. | hep-ex |
A Measurement of the Proton Structure Function $F_{\!2}(x,Q^2)$: A measurement of the proton structure function $F_{\!2}(x,Q^2)$ is reported
for momentum transfer squared $Q^2$ between 4.5 $GeV^2$ and 1600 $GeV^2$ and
for Bjorken $x$ between $1.8\cdot10^{-4}$ and 0.13 using data collected by the
HERA experiment H1 in 1993. It is observed that $F_{\!2}$ increases
significantly with decreasing $x$, confirming our previous measurement made
with one tenth of the data available in this analysis. The $Q^2$ dependence is
approximately logarithmic over the full kinematic range covered. The subsample
of deep inelastic events with a large pseudo-rapidity gap in the hadronic
energy flow close to the proton remnant is used to measure the "diffractive"
contribution to $F_{\!2}$. | hep-ex |
Search for pair production of Higgs bosons in the $b\bar{b}b\bar{b}$
final state using proton--proton collisions at $\sqrt{s} = 13$ TeV with the
ATLAS detector: A search for Higgs-boson pair production in the $b\bar{b}b\bar{b}$ final
state is carried out with 3.2 fb$^{-1}$ of proton--proton collision data
collected at $\sqrt{s} = 13$ TeV with the ATLAS detector. The data are
consistent with the estimated background and are used to set upper limits on
the production cross section of Higgs-boson pairs times branching ratio to
$b\bar{b}b\bar{b}$ for both nonresonant and resonant production. In the case of
resonant production of Kaluza--Klein gravitons within the Randall--Sundrum
model, upper limits in the 24 to 91 fb range are obtained for masses between
600 and 3000 GeV, at the 95% confidence level. The production cross section
times branching ratio for nonresonant Higgs-boson pairs is also constrained to
be less than 1.22 pb, at the 95% confidence level. | hep-ex |
Results on alpha_s and QCD from (and Above) the Z0: Measurements of alpha_s from e+e- annihilation experiments are reviewed and
compared with measurements from other processes. Highlights are presented of
recent QCD studies in e+e- annihilation at the Z0 resonance. | hep-ex |
The $φ(1020)\toπ^0π^0γ$ decay: In the SND experiment at VEPP-2M $e^+e^-$ collider the
$\phi(1020)\to\pi^0\pi^0\gamma$ decay was studied and its branching ratio was
measured: $B(\phi\to\pi^0\pi^0\gamma)=(1.221\pm 0.098\pm0.061)\cdot10^{-4}$. It
was shown, that $f_0(980)\gamma$ intermediate state dominates in this decay and
the $f_0(980)$-meson parameters were obtained. | hep-ex |
α_S from LEP: Recent results on measurements of the strong coupling $\alpha_S$ from LEP are
reported. These include analyses of the 4-jet rate using the Durham or
Cambridge algorithm, of hadronic $Z^0$ decays with hard final state photon
radiation, of scaling violations of the fragmentation function, of the
longitudinal cross section, of the $Z^0$ lineshape and of hadronic $\tau$
lepton decays. | hep-ex |
Search for an anomalous excess of charged-current $ν_e$ interactions
without pions in the final state with the MicroBooNE experiment: This article presents a measurement of $\nu_e$ interactions without pions in
the final state using the MicroBooNE experiment and an investigation into the
excess of low-energy electromagnetic events observed by the MiniBooNE
collaboration. The measurement is performed in exclusive channels with
(1$e$N$p$0$\pi$) and without (1$e$0$p$0$\pi$) visible final-state protons using
6.86$\times 10^{20}$ protons on target of data collected from the Booster
Neutrino Beam at Fermilab. Events are reconstructed with the Pandora pattern
recognition toolkit and selected using additional topological information from
the MicroBooNE liquid argon time projection chamber. Using a goodness-of-fit
test the data are found to be consistent with the predicted number of events
with nominal flux and interaction models with a $p$-value of 0.098 in the two
channels combined. A model based on the low-energy excess observed in MiniBooNE
is introduced to quantify the strength of a possible $\nu_e$ excess. The
analysis suggests that if an excess is present, it is not consistent with a
simple scaling of the $\nu_e$ contribution to the flux. Combined, the
1$e$N$p$0$\pi$ and 1$e$0$p$0$\pi$ channels do not give a conclusive indication
about the tested model, but separately they both disfavor the low-energy excess
model at $>$90% CL. The observation in the most sensitive 1$e$N$p$0$\pi$
channel is below the prediction and consistent with no excess. In the less
sensitive 1$e$0$p$0$\pi$ channel the observation at low energy is above the
prediction, while overall there is agreement over the full energy spectrum. | hep-ex |
Studies of Quantum-Mechanical Coherency Effects in Neutrino-Nucleus
Elastic Scattering: Neutrino-nucleus elastic scattering ($\nu {\rm A}_{el}$) provides a unique
laboratory to study the quantum-mechanical (QM) coherency effects in
electroweak interactions. The deviations of the cross-sections from those of
completely coherent systems can be quantitatively characterized through a
coherency parameter $\alpha ( q^2 )$. The relations between $\alpha$ and the
underlying nuclear physics in terms of nuclear form factors are derived. The
dependence of cross-section on $\alpha ( q^2 )$ for the various neutrino
sources is presented. The $\alpha ( q^2 )$-values are evaluated from the
measured data of the COHERENT CsI and Ar experiments. Complete coherency and
decoherency conditions are excluded by the CsI data with $p {=} 0.004$ at $q^2
{=} 3.1 {\times} 10^{3} ~ {\rm MeV^2}$ and with $p {=} 0.016$ at $q^2 {=} 2.3
{\times} 10^{3} ~ {\rm MeV^2}$, respectively, verifying that both QM
superpositions and nuclear many-body effects contribute to $\nu {\rm A}_{el}$
interactions. | hep-ex |
Measurement of charged-particle spectra in Pb+Pb collisions at
$\sqrt{{s}_\mathsf{NN}} = 2.76$ TeV with the ATLAS detector at the LHC: Charged-particle spectra obtained in 0.15 nb${}^{-1}$ of Pb+Pb interactions
at $\sqrt{{s}_\mathsf{{NN}}}=2.76$TeV and 4.2 pb${}^{-1}$ of pp interactions at
$\sqrt{s}=2.76$ TeV with the ATLAS detector at the LHC are presented in a wide
transverse momentum ($0.5 < p_{\mathrm{T}} < 150$ GeV) and pseudorapidity
($|\eta|<2$) range. For Pb+Pb collisions, the spectra are presented as a
function of collision centrality, which is determined by the response of the
forward calorimeter located on both sides of the interaction point. The nuclear
modification factors $R_{\mathrm{AA}}$ and $R_{\mathrm{CP}}$ are presented in
detail as function of centrality, $p_{\mathrm{T}}$ and $\eta$. They show a
distinct $p_{\mathrm{T}}$-dependence with a pronounced minimum at about 7 GeV.
Above 60 GeV, $R_{\mathrm{AA}}$ is consistent with a plateau at a
centrality-dependent value, within the uncertainties. The value is
$0.55\pm0.01(stat.)\pm0.04(syst.)$ in the most central collisions. The
$R_{\mathrm{AA}}$ distribution is consistent with flat $|\eta|$ dependence over
the whole transverse momentum range in all centrality classes. | hep-ex |
Measurement of the polarization amplitudes and triple product
asymmetries in the B_s^0 -> phi phi decay: Using 1.0 fb^{-1} of pp collision data collected at a centre-of-mass energy
of sqrt{s}=7 TeV with the LHCb detector, measurements of the polarization
amplitudes, strong phase difference and triple product asymmetries in the B_s^0
-> phi phi decay mode are presented. The measured values are |A_0|^2 = 0.365 +-
0.022 (stat) +- 0.012 (syst), |A_perp|^2 = 0.291 +- 0.024 (stat) +- 0.010
(syst), cos(delta_parallel) = -0.844 +- 0.068 (stat) +- 0.029 (syst), A_U =
-0.055 +- 0.036 (stat) +- 0.018 (syst), A_V = 0.010 +- 0.036 (stat) +- 0.018
(syst) . | hep-ex |
Search for High-Mass States with Lepton Plus Missing Transverse Energy
Using the ATLAS Detector at Center-of-Mass Energy of 7 TeV: The ATLAS detector has been used to search for high-mass states decaying into
a single high momentum lepton and missing transverse energy, such as new heavy
charged gauge bosons. The latest search results for a W Prime boson decaying to
lepton plus neutrino in 1.04 fb^-1 of proton-proton collisions at a center of
mass energy of 7 TeV produced at the Large Hadron Collider are presented. | hep-ex |
Measurements of $t$-channel single top-quark production cross sections
at $\sqrt{s} = 7$ TeV with the ATLAS detector: This article presents measurements of the $t$-channel single top-quark ($t$)
and top-antiquark ($\bar{t}$) total production cross sections $\sigma(tq)$ and
$\sigma(\bar{t}q)$, their ratio $R_t=\sigma(tq)/\sigma(\bar{t}q)$. Differential
cross sections for the $\sigma(tq)$ and $\sigma(\bar{t}q)$ processes are
measured as a function of the transverse momentum and the absolute value of the
rapidity of ($t$) and ($\bar{t}$), respectively. The analysed data set was
recorded with the ATLAS detector and corresponds to an integrated luminosity of
4.59 fb$^{-1}$. The cross sections are measured by performing a binned
maximum-likelihood fit to the output distributions of neural networks. The
resulting measurements are $\sigma(tq)=46 \pm 6$ pb, $\sigma(\bar{t}q)=23 \pm
4$ pb, $R_t=2.04 \pm 0.18$, consistent with the Standard Model expectation. | hep-ex |
Observation of B_s0->D_s*- pi+, B_s0->D_s(*)- rho+ Decays and
Measurement of B_s0->D_s*- rho+ Polarization: First observations of the B_s0->D_s*- pi+, B_s0->D_s- rho+ and B_s0->D_s*-
rho+ decays are reported together with measurements of their branching
fractions: B(B_s0->D_s*- pi+)=(2.4 +0.5-0.4(stat.) +-0.3(syst.)
+-0.4(fs))x10^(-3), B(Bs->D_s- rho+)=(8.5 +1.3-1.2(stat.) +-1.1(syst.)
+-1.3(fs))x10^(-3) and B(Bs->D_s*- rho+)=(11.8 +2.2-2.0(stat.) +-1.7(syst.)
+-1.8(fs))x10^(-3) (f_s=N(B_s(*)B_s(*)-bar)/N(b b-bar)). From helicity-angle
distributions, we measured the longitudinal polarization fraction in
B_s0->D_s*- rho+ decays to be f_L(Bs->D_s*- rho+)=1.05 +0.08-0.10(stat.)
+0.03-0.04(syst.). These results are based on a 23.6 /fb data sample collected
at the Y(5S) resonance with the Belle detector at the KEKB e+e- collider. | hep-ex |
Observation of a resonance X(1835) in J/ψ--> γπ^+ π^-
η^{\prime}: The decay channel J/\psi --> \gamma \pi^+ \pi^- \eta^{\prime} is analyzed
using a sample of 5.8\times 10^7 J\psi events collected with the BESII
detector. A resonance, the X(1835), is observed in the \pi^+ \pi^-
\eta^{\prime} invariant mass spectrum with a statistical significance of 7.7
\sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 \pm
6.1(stat) \pm 2.7(syst) MeV/c^2, a width \Gamma = 67.7 \pm 20.3(stat) \pm
7.7(syst) MeV/c^2 and a product branching fraction B(J/\psi --> \gamma X) B(X
--> \pi^+ \pi^- \eta^{\prime}) = (2.2 \pm 0.4(stat) \pm 0.4(syst)) \times
10^{-4}. The mass and width of the X(1835) are not compatible with any known
meson resonance. Its properties are consistent with expectations for the state
that produces the strong p\bar{p} mass threshold enhancement observed in the
J\psi -->\gamma p \bar{p} process at BESII. | hep-ex |
Study of the Reaction $np \rightarrow np π^+ π^-$ at Intermediate
Energies: The reaction $np \rightarrow np \pi^+ \pi^-$ was studied at the various
momenta of incident neutrons. It was shown that the characteristics of the
reaction at the momenta above 3 GeV/c could be described by the model of
reggeized $\pi$ exchange (OPER). At the momenta below 3 GeV/c, it was necessary
to use additionally the mechanism of one baryon exchange (OBE). | hep-ex |
A Measurement of CP Asymmetry in b->sgamma using a Sum of Exclusive
Final States: We perform a measurement of the CP asymmetry in b->sgamma decays using a
sample of 383 BB events collected by the BABAR detector at the PEP-II
asymmetric B factory. We reconstruct sixteen flavor-specific B decay modes
containing a high-energy photon and a hadronic system (Xs) containing an s
quark. We measure the \CP asymmetry to be -0.011+/- 0.030(stat)+/-0.014(syst)
for a photon energy threshold at 1.6 GeV and the hadronic system mass between
0.6 and 2.8 GeV/c2. | hep-ex |
Moriond 2012, QCD and High Energy Interactions: Baryonic B decays at
BaBar: We report on the analyses of the baryonic B decays B0bar -> LambdaC+ p- p+ p-
and B- -> SigmaC++ p- pi- pi-. The underlying data sample consists of 470 x
10^6 BBbar pairs generated in the process e+e- -> Y(4S) and collected with the
BaBar detector at the PEP-II storage ring at SLAC. We find BR(B0bar -> LambdaC+
p- p+ p-) x BR(LambdaC+ -> p+ K- pi+) / 5% < 6.2 x 10^(-6) @ CL=90% and BR(B-
-> SigmaC++ p- pi- pi-) = [2.98 +/- 0.16(stat) +/- 0.15(syst) +/-
0.77(LambdaC+)] x 10^(-4), where the last error is due to the uncertainty in
BR(LambdaC+ -> p+ K- pi+). The data suggest the existence of resonant
subchannels B- -> LambdaC(2595)+ p- pi- and, possibly, B- -> SigmaC++
anti-Delta-- pi-. We see unexplained structures in m(SigmaC++ pi- pi-) at 3.25
GeV/c^2, 3.8 GeV/c^2, and 4.2 GeV/c^2. | hep-ex |
Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at
Large Liquid Scintillator Detectors: Non-vanishing electromagnetic properties of the neutrinos have been predicted
by many theories beyond the Standard Model, and an enhanced neutrino magnetic
moment can have profound implications for fundamental physics. The XENON1T
experiment recently detected an excess of electron recoil events in the 1-7 keV
energy range, which can be compatible with solar neutrino magnetic moment
interaction at a most probable value of $\mu_{\nu} = 2.1 \times 10^{-11}
\mu_{\text{B}}$. However, tritium backgrounds and solar axion interaction in
this energy window are equally plausible causes. Upcoming multi-tonne noble
liquid detectors will test these scenarios more in depth, but will continue to
face similar ambiguity. We report a unique capability of future large liquid
scintillator detectors to help resolve the potential neutrino magnetic moment
scenario. With a liquid scintillator exposure of $O$(100) kton$\cdot$year, a
sensitivity of $\mu_{\nu} < 10^{-11} \mu_{\text{B}}$ can be reached at an
energy threshold greater than 40 keV, where no tritium or solar axion events
but only neutrino magnetic moment signal is still present. | hep-ex |
Light Hadron Spectroscopy and Decay at BESIII: Light hadron spectroscopy plays an important role in understanding the decay
dynamics of unconventional hadronic states, such as strangeonium and glueballs.
BESIII provides an ideal avenue to search for these exotic states thanks to a
huge amount of data recorded at various energy points in the tau-charm mass
region including J/psi resonance. This report summarizes recent results of the
BESIII experiment related to the glueballs and strangeonium-like states. | hep-ex |
Search for top squarks in final states with two top quarks and several
light-flavor jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV: Many new physics models, including versions of supersymmetry characterized by
$R$-parity violation (RPV), compressed mass spectra, long decay chains, or
additional hidden sectors, predict the production of events with top quarks,
low missing transverse momentum, and many additional quarks or gluons. The
results of a search for new physics in events with two top quarks and
additional jets are reported. The search is performed using events with at
least seven jets and exactly one electron or muon. No requirement on missing
transverse momentum is imposed. The study is based on a sample of proton-proton
collisions at $\sqrt{s} =$ 13 TeV corresponding to 137 fb$^{-1}$ of integrated
luminosity collected with the CMS detector at the LHC in 2016-2018. The data
are used to determine best fit values and upper limits on the cross section for
pair production of top squarks in scenarios of RPV and stealth supersymmetry.
Top squark masses up to 670 (870) GeV are excluded at 95% confidence level for
the RPV (stealth) scenario, and the maximum observed local signal significance
is 2.8 standard deviations for the RPV scenario with top squark mass of 400
GeV. | hep-ex |
Updated Combination of CDF and D0 Searches for Standard Model Higgs
Boson Production with up to 10.0 fb-1 of Data: We combine results from the CDF and D0 Collaborations on direct searches for
the standard model (SM) Higgs boson (H) in ppbar collisions at the Fermilab
Tevatron at sqrt(s)=1.96 TeV. Compared to the previous Tevatron Higgs boson
search combination, more data have been included, additional channels have been
incorporated, and some previously used channels have been reanalyzed to gain
sensitivity. Searches are carried out for hypothesized Higgs boson masses
between 100 and 200 GeV/c^2. With up to 10 fb-1 of luminosity analyzed, the 95%
C.L. median expected upper limits on Higgs boson production are factors of
0.89, 1.08, and 0.48 times the values of the SM cross section for Higgs bosons
of mass m_H=115 GeV/c^2, 125 GeV/c^2, and 165 GeV/c^2, respectively. In the
absence of signal, we expect to exclude the regions 100<m_{H}<120 GeV/c^2 and
139<m_H<184 GeV/c^2. We exclude, at the 95% CL, two regions: 100<m_H<103
GeV/c^2, and 147<m_H<180 GeV/c^2. There is a significant excess of data events
with respect to the background estimation in the mass range 115<m_H<140
GeV/c^2, which causes our observed limits to not be as stringent as expected.
At m_H=120 GeV/c^2, the p-value for a background fluctuation to produce this
excess is \sim1.5x10^-3, corresponding to a local significance of 3.0 standard
deviations. The global significance for such an excess anywhere in the full
mass range investigated is approximately 2.5 standard deviations. We also
combine separately searches for H to bb and H to WW. We find that the excess is
concentrated in the H to bb channel, appearing in the searches over a broad
range of m_H. The maximum local significance of 3.2 standard deviations
corresponds to a global significance of approximately 2.9 standard deviations.
Our results in the H to WW channels are also consistent with the possible
presence of a low-mass Higgs boson. | hep-ex |
A study of topological vertexing for heavy quark tagging: We compare heavy quark tagging and anti-tagging efficiencies for vertex
detectors with different inner raddi using the topological vertex technique
developed at the SLC/SLD experiment. Charm tagging benefits by going to very
small inner radii. | hep-ex |
Measurements of Higgs boson properties in the diphoton decay channel in
proton-proton collisions at $\sqrt{s} =$ 13 TeV: Measurements of Higgs boson properties in the H $\to\gamma\gamma$ decay
channel are reported. The analysis is based on data collected by the CMS
experiment in proton-proton collisions at $\sqrt{s} =$ 13 TeV during the 2016
LHC running period, corresponding to an integrated luminosity of 35.6
fb$^{-1}$. Allowing the Higgs mass to float, the measurement yields a signal
strength relative to the standard model prediction of 1.18 $^{+0.17}_{-0.14} =$
1.18 $^{+0.12}_{-0.11}$ (stat) $^{+0.09}_{-0.07}$ (syst) $^{+0.07}_{-0.06}$
(theo), which is largely insensitive to the exact Higgs mass around 125 GeV.
Signal strengths associated with the different Higgs boson production
mechanisms, couplings to bosons and fermions, and effective couplings to
photons and gluons are also measured. | hep-ex |
The "Golden Mode" at the Upgraded Tevatron?: The exiatence of extra SM families results in essential enhancement of the
gluon fusion channel Higgs boson production at hadron colliders. In this case,
the SM Higgs boson can be seen at the upgraded Tevatron via the "golden mode"
(H-->4l) for certain values of its mass. | hep-ex |
The LHCB Commissioning: The LHCb experiment is dedicated to precision measurements of CP violation
and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN. The
LHCb installation has been finished in spring 2008 and an intensive testing and
commissioning of the system has been started. An overview and the results from
our commissioning activities are described. | hep-ex |
Measurement of Trilinear Gauge Boson Couplings WWV, (V = Z,gamma) in
e+e- Collisions at 189 GeV: Measurements of the trilinear gauge boson couplings WWgamma and WWZ are
presented using the data taken by DELPHI in 1998 at a centre-of-mass energy of
189 GeV and combined with DELPHI data at 183 GeV. Values are determined for
Delta(g_1^Z) and Delta(kappa_gamma), the differences of the WWZ charge coupling
and of the WWgamma dipole coupling from their Standard Model values, and for
lambda_gamma, the WWgamma quadrupole coupling. A measurement of the magnetic
dipole and electric quadrupole moment of the W is extracted from the results
for Delta(kappa_gamma) and lambda_gamma. The study uses data from the final
states jjlv, jjjj, lX, jjX and gammaX, where j represents a quark jet, l an
identified lepton and X missing four-momentum. The observations are consistent
with the predictions of the Standard Model. | hep-ex |
Measurements of the reaction $\bar{p}p \to φη$ of antiproton
annihilation at rest at three hydrogen target densities: The proton-antiproton annihilation at rest into the $\phi\eta$ final state
was measured for three different target densities: liquid hydrogen, gaseous
hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in
the liquid hydrogen target is smaller than in the low-pressure gas target. The
branching ratios of the $\phi\eta$ channel were calculated on the basis of
simultaneous analysis of the three data samples. The branching ratio for
annihilation into $\phi\eta$ from the $^3S_1$ protonium state turns out to be
about ten times smaller as compared to the one from the $^1P_1$ state. | hep-ex |
Evidence for new interference phenomena in the decay D+ to K- pi+ mu+ nu: Using a large sample of charm semileptonic decays collected by the FOCUS
photoproduction experiment at Fermilab, we present evidence for a small, even
spin K- \pi+ amplitude that interferes with the dominant K*0 component in the
K-pi+ mu- nu final state. Although this interference significantly distorts the
decay angular distributions, the new amplitude creates only a very small
distortion to the observed kaon pion mass distribution when integrated over the
other kinematic variables describing the decay. Our data can be described by
K*0 interference with either a constant amplitude or broad spin zero resonance. | hep-ex |
New PVLAS results and limits on magnetically induced optical rotation
and ellipticity in vacuum: IIn 2006 the PVLAS collaboration reported the observation of an optical
rotation generated in vacuum by a magnetic field. To further check against
possible instrumental artifacts several upgrades to the PVLAS apparatus have
been made during the last year. Two data taking runs, at the wavelength of 1064
nm, have been performed in the new configuration with magnetic field strengths
of 2.3 T and 5 T. The 2.3 T field value was chosen in order to avoid stray
fields. The new observations do not show the presence of a rotation signal down
to the levels of $1.2\cdot 10^{-8}$ rad at 5 T and $1.0\cdot 10^{-8}$ rad at
2.3 T (at 95% c.l.) with 45000 passes in the magnetic field zone. In the same
conditions no ellipticity signal was detected down to $1.4\cdot 10^{-8}$ at 2.3
T (at 95% c.l.), whereas at 5 T a signal is still present. The physical nature
of this ellipticity as due to an effect depending on $B^2$ can be excluded by
the measurement at 2.3 T. These new results completely exclude the previously
published magnetically induced vacuum dichroism results, indicating that they
were instrumental artifacts. These new results therefore also exclude the
particle interpretation of the previous PVLAS results as due to a spin zero
boson. The background ellipticity at 2.3 T can be used to determine a new limit
on the total photon-photon scattering cross section of $\sigma_{\gamma\gamma} <
4.5 \cdot10^{-34}$ barn at 95% c.l.. | hep-ex |
Search for the Weak Decay of a Lightly Bound H Dibaryon: We present results of a search for a neutral, six-quark, dibaryon state
called the \h, a state predicted to exist in several theoretical models.
Observation of such a state would signal the discovery of a new form of
hadronic matter. Analyzing data collected by experiment E799-II, using the KTeV
detector at Fermilab, we searched for the decay $H^0 \to \Lambda p \piminus$
and found no candidate events. We exclude the region of lightly bound mass
states just below the $\Lambda\Lambda$ mass threshold, $2.194~\gev < M_H <
2.231$~\gev, with lifetimes from $\sim$$ 5 \times 10^{-10}$~sec to $\sim$$1
\times 10^{-3}$~sec. | hep-ex |
Precision Measurement of B(D+ -> mu+ nu) and the Pseudoscalar Decay
Constant fD+: We measure the branching ratio of the purely leptonic decay of the D+ meson
with unprecedented precision as B(D+ -> mu+ nu) = (3.82 +/- 0.32 +/-
0.09)x10^(-4), using 818/pb of data taken on the psi(3770) resonance with the
CLEO-c detector at the CESR collider. We use this determination to derive a
value for the pseudoscalar decay constant fD+, combining with measurements of
the D+ lifetime and assuming |Vcd| = |Vus|. We find fD+ = (205.8 +/- 8.5 +/-
2.5) MeV. The decay rate asymmetry [B(D+ -> mu+ nu)-B(D- -> mu- nu)]/[B(D+ ->
mu+ nu)+B(D- -> mu- nu)] = 0.08 +/- 0.08, consistent with no CP violation. We
also set 90% confidence level upper limits on B(D+ -> tau+ nu) < 1.2x10^(-3)
and B(D+ -> e+ nu) < 8.8x10^(-6). | hep-ex |
Observation of two resonances in the $Λ_b^0 π^\pm$ systems and
precise measurement of $Σ_b^\pm$ and $Σ_b^{*\pm}$ properties: The first observation of two structures consistent with resonances in the
final states $\Lambda_b^0 \pi^-$ and $\Lambda_b^0 \pi^+$ is reported using
samples of $pp$ collision data collected by the LHCb experiment at $\sqrt{s} =
7$ and $8$ TeV, corresponding to an integrated luminosity of 3
$\mathrm{fb}^{-1}$. The ground states $\Sigma_b^\pm$ and $\Sigma_b^{*\pm}$ are
also confirmed and their masses and widths are precisely measured. | hep-ex |
Transverse Spin Studies with STAR at RHIC: STAR has observed sizable transverse single-spin asymmetries for inclusive
pi^0 production at forward rapidity in p+p collisions at sqrt{s}=200 GeV. These
asymmetries may arise from either the Sivers or Collins effect. Studies are
underway during the current RHIC run to elucidate the dynamics that underlie
these single-spin asymmetries. Additional measurements are underway to search
for the Sivers effect in mid-rapidity di-jet production. | hep-ex |
Probing the BFKL dynamics at hadronic colliders: We describe different possibilities to probe the BFKL dynamics at hadronic
colliders, namely Mueller-Navelet jet, and jet gap jet events. We also discuss
briefly the jet veto measurement as performed by the ATLAS collaboration at the
LHC. | hep-ex |
Measurements of top-quark pair to $Z$-boson cross-section ratios at
$\sqrt s = 13, 8, 7$TeV with the ATLAS detector: Ratios of top-quark pair to $Z$-boson cross sections measured from
proton--proton collisions at the LHC centre-of-mass energies of $\sqrt
s=13$TeV, 8TeV, and 7TeV are presented by the ATLAS Collaboration. Single
ratios, at a given $\sqrt s$ for the two processes and at different $\sqrt s$
for each process, as well as double ratios of the two processes at different
$\sqrt s$, are evaluated. The ratios are constructed using previously published
ATLAS measurements of the $t\overline{t}$ and $Z$-boson production cross
sections, corrected to a common phase space where required, and a new analysis
of $Z \rightarrow \ell^+ \ell^-$ where $\ell=e,\mu$ at $\sqrt s=13$TeV
performed with data collected in 2015 with an integrated luminosity of
$3.2$fb$^{-1}$. Correlations of systematic uncertainties are taken into account
when evaluating the uncertainties in the ratios. The correlation model is also
used to evaluate the combined cross section of the $Z\rightarrow e^+e^-$ and
the $Z\rightarrow \mu^+ \mu^-$ channels for each $\sqrt s$ value. The results
are compared to calculations performed at next-to-next-to-leading-order
accuracy using recent sets of parton distribution functions. The data
demonstrate significant power to constrain the gluon distribution function for
the Bjorken-$x$ values near 0.1 and the light-quark sea for $x<0.02$. | hep-ex |
The indication for $^{40}$K geo-antineutrino flux with Borexino
phase-III data: We provide the indication of high flux of $^{40}$K geo-antineutrino and
geo-neutrino ($^{40}$K-geo-($\bar{\nu} + \nu$)) with Borexino Phase III data.
This result was obtained by introducing a new source of single events, namely
$^{40}$K-geo-($\bar{\nu} + \nu$) scattering on electrons, in multivariate fit
analysis of Borexino Phase III data. Simultaneously we obtained the count rates
of events from $^7$Be, $pep$ and CNO solar neutrinos. These count rates are
consistent with the prediction of the Low metallicity Sun model SSM B16-AGSS09.
MC pseudo-experiments showed that the case of High metallicity Sun and absence
of $^{40}$K-geo-($\bar{\nu} + \nu$) can not imitate the result of multivariate
fit analysis of Borexino Phase III data with introducing
$^{40}$K-geo-($\bar{\nu} + \nu$) events. We also provide arguments for the high
abundance of potassium in the Earth. | hep-ex |
Observation of new baryons in the $Ξ_b^-π^+π^-$ and
$Ξ_b^0π^+π^-$ systems: The first observation and study of two new baryonic structures in the final
state $\Xi_b^0\pi^+\pi^-$ and the confirmation of the $\Xi_b(6100)^-$ state in
the $\Xi_b^-\pi^+\pi^-$ decay mode are reported using proton-proton collision
data collected by the LHCb experiment, corresponding to an integrated
luminosity of 9$\mathrm{fb}^{-1}$. In addition, the properties of the known
$\Xi_b^{*0}$, $\Xi_b^{'-}$ and $\Xi_b^{*-}$ resonances are measured with
improved precision. The new decay mode of the $\Xi_b^0$ baryon to the
$\Xi_c^+\pi^-\pi^+\pi^-$ final state is observed and exploited for the first
time in these measurements. | hep-ex |
Review of physics results from the Tevatron: QCD physics: We present a summary of results from studies of quantum chromodynamics at the
Fermilab Tevatron collider by the CDF and the D0 experiments. These include Run
II results for the time period up to the end of Summer 2014. A brief
description of Run I resultsis also given. This review covers a wide spectrum
of topics, and includes measurements with jet and vector boson final states in
the hard (perturbative) energy regime, as well as studies of soft physics such
as diffractive and elastic scatterings, underlying and minimum bias events,
hadron fragmentation, and multiple parton interactions. | hep-ex |
Search for WH associated production at Dø Tevatron: The Higgs mechanism introduced in 1964 gives a satisfactory solution to a
major problem of the standard model of elementary particles: the origin of the
mass. It predicts the existence of the Higgs scalar boson, which has not been
discovered experimentally yet. The Tevatron, a hadron accelerator based at
Fermi National Accelerator Laboratory near Chicago, has delivered data to its
two multi-purpose detectors CDF and DZERO since 1983 up to september 2011.
Leaving us about 11 fb-1 of data per experiment to analyze. Associated
production of a Higgs boson and a vector gauge boson W or Z is the main search
channel for a light standard Higgs boson (i.e. below 135 GeV/c2). Using data
collected by DZERO, we are looking for this production mode taking advantage of
sophisticated techniques to improve the signal sensitivity such as b-jet
identification and multivariate discriminants. In the end, a statistical
approach allows us to set an upper limit on the ratio between the observed
(resp. expected) Higgs production cross section and its theoretical cross
section. The latest result obtained in the WH channel using 8.5 f b-1 at DZERO
is 4.6 (resp. 3.5) for a 115 GeV/c2 Higgs boson. | hep-ex |
Experimental results on $K_L$ decays: Recent measurements by the NA48 at CERN of selected $K_L$ decays are
presented. These are the branching ratios and form factors for channels $K_L\to
\pi^{\pm}\pi^0\e^{\mp}\nu_e$ (final result), $K_L\to\pi^{\pm}e^{\mp}\nu_e$ and
$K_L\to e^+e^-e^+e^-$ (preliminary results). | hep-ex |
Measurement of the production cross section for $Z/γ^*$ in
association with jets in pp collisions at $\sqrt{s}$ = 7 TeV with the ATLAS
Detector: We present results on the production of jets of particles in association with
a $Z/\gamma^*$ boson, in proton-proton collisions at $\sqrt{s} = 7$ TeV with
the ATLAS detector at the LHC. The analysis includes the full 2010 data set,
collected with a low rate of multiple proton-proton collisions in the
accelerator, corresponding to an integrated luminosity of $36 \rm pb^{-1}$.
Inclusive jet cross sections in $Z/\gamma^*$ events, with $Z/\gamma^*$ decaying
into electron or muon pairs, are measured for jets with transverse momentum
$p_T >$ 30 GeV and jet rapidity $|y| < 4.4$. The measurements are compared to
next-to-leading-order perturbative QCD calculations, and to predictions from
different Monte Carlo generators implementing leading-order matrix elements
supplemented by parton showers. | hep-ex |
Future Polarised DIS Fixed Target Experiments: New experiments in polarised deep inelastic scattering will mainly
concentrate on the measurement of semi-inclusive asymmetries. Especially, the
upgraded HERMES experiment at DESY and the newly build COMPASS experiment at
CERN will investigate the gluon polarisation via open charm and high p_T hadron
pair production, study in detail the flavour decomposition of the quark
helicity distributions and measure the tranversity distributions with
tranversely polarised targets. | hep-ex |
Search for a Charged Higgs Boson Produced in the Vector-boson Fusion
Mode with Decay $H^\pm \to W^\pm Z$ using $pp$ Collisions at $\sqrt{s}=8$ TeV
with the ATLAS Experiment: A search for a charged Higgs boson, $H^\pm$, decaying to a $W^\pm$ boson and
a $Z$ boson is presented. The search is based on 20.3 fb$^{-1}$ of
proton-proton collision data at a center-of-mass energy of 8 TeV recorded with
the ATLAS detector at the LHC. The $H^\pm$ boson is assumed to be produced via
vector-boson fusion and the decays $W^\pm \to q\bar{q^\prime}$ and
$Z\rightarrow e^+e^-/\mu^+\mu^-$ are considered. The search is performed in a
range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the
production of an $H^\pm$ boson is observed. Upper limits of 31-1020 fb at 95%
CL are placed on the cross section for vector-boson fusion production of an
$H^\pm$ boson times its branching fraction to $W^\pm Z$. The limits are
compared with predictions from the Georgi-Machacek Higgs Triplet Model. | hep-ex |
First background-free limit from a directional dark matter experiment:
results from a fully fiducialised DRIFT detector: The addition of O2 to gas mixtures in time projection chambers containing CS2
has recently been shown to produce multiple negative ions that travel at
slightly different velocities. This allows a measurement of the absolute
position of ionising events in the z (drift) direction. In this work, we apply
the z-fiducialisation technique to a directional dark matter search. In
particular, we present results from a 46.3 live-day source-free exposure of the
DRIFT-IId detector run in this completely new mode. With full-volume
fiducialisation, we have achieved the first background-free operation of a
directional detector. The resulting exclusion curve for spin-dependent
WIMP-proton interactions reaches 1.1 pb at 100 GeV/c2, a factor of 2 better
than our previous work. We describe the automated analysis used here, and argue
that detector upgrades, implemented after the acquisition of these data, will
bring an additional factor of >3 improvement in the near future. | hep-ex |
Search for a Higgs Boson Decaying into Two Photons at LEP: A Higgs particle produced in association with a Z boson and decaying into two
photons is searched for in the data collected by the L3 experiment at LEP. All
possible decay modes of the Z boson are investigated. No signal is observed in
447.5 pb^-1 of data recorded at centre-of-mass energies up to 209 GeV. Limits
on the branching fraction of the Higgs boson decay into two photons as a
function of the Higgs mass are derived. A lower limit on the mass of a
fermiophobic Higgs boson is set at 105.4 GeV at 95% confidence level. | hep-ex |
Evidence for the direct decay of the 125 GeV Higgs boson to fermions: The discovery of a new boson with a mass of approximately 125 GeV in 2012 at
the LHC has heralded a new era in understanding the nature of electroweak
symmetry breaking and possibly completing the standard model of particle
physics. Since the first observation in decays to gamma gamma, WW, and ZZ boson
pairs, an extensive set of measurements of the mass and couplings to W and Z
bosons, as well as multiple tests of the spin-parity quantum numbers, have
revealed that the properties of the new boson are consistent with those of the
long-sought agent responsible for electroweak symmetry breaking. An important
open question is whether the new particle also couples to fermions, and in
particular to down-type fermions, since the current measurements mainly
constrain the couplings to the up-type top quark. Determination of the
couplings to down-type fermions requires direct measurement of the
corresponding Higgs boson decays, as recently reported by the CMS experiment in
the study of Higgs decays to bottom quarks and tau leptons. In this paper we
report the combination of these two channels which results, for the first time,
in strong evidence for the direct coupling of the 125 GeV Higgs boson to
down-type fermions, with an observed significance of 3.8 standard deviations,
when 4.4 are expected. | hep-ex |
Search for Leptoquarks in Electron-Photon Scattering at sqrt(s_ee) up to
209 GeV at LEP: Searches for first generation scalar and vector leptoquarks, and for squarks
in R-parity violating SUSY models with the direct decay of the squark into
Standard Model particles, have been performed using e+e- collisions collected
with the OPAL detector at LEP at e+e- centre-of-mass energies between 189 and
209 GeV. No excess of events is found over the expectation from Standard Model
background processes. Limits are computed on the leptoquark couplings for
different values of the branching ratio to electron-quark final states. | hep-ex |
Search for Electron Neutrino Appearance in a 250 km Long-baseline
Experiment: We present a search for electron neutrino appearance from accelerator
produced muon neutrinos in the K2K long baseline neutrino experiment. One
candidate event is found in the data corresponding to an exposure of 4.8*10^19
protons on target. The expected background in the absence of neutrino
oscillations is estimated to be 2.4+-0.6 events and is dominated by
mis-identification of events from neutral current pi^0 production. We exclude
the \nu_\mu to \nu_e oscillations at 90% C.L. for the effective mixing angle in
2-flavor approximation of sin^2(2theta_\mu_e) (~= 1/2 sin^2 2 th_13) > 0.15 at
Delta m^2_\mu_e = 2.8*10^{-3} eV^2, the best fit value of the \nu_\mu
disappearance analysis in K2K. The most stringent limit of sin^2(2theta_\mu_e)
< 0.09 is obtained at Delta m^2_\mu_e = 6*10^{-3} eV^2. | hep-ex |
Search for high-mass resonances in final states with a lepton and
missing transverse momentum at $\sqrt{s}=$ 13 TeV: A search for new high-mass resonances in proton-proton collisions having
final states with an electron or muon and missing transverse momentum is
presented. The analysis uses proton-proton collision data collected in 2016
with the CMS detector at the LHC at a center-of-mass energy of 13 TeV,
corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The transverse
mass distribution of the charged lepton-neutrino system is used as the
discriminating variable. No significant deviation from the standard model
prediction is found. The best limit, from the combination of electron and muon
channels, is 5.2 TeV at 95% confidence level for the mass of a W$'$ boson with
the same couplings as those of the standard model W boson. Exclusion limits of
2.9 TeV are set on the inverse radius of the extra dimension in the framework
of split universal extra dimensions. In addition, model-independent limits are
set on the production cross section and coupling strength of W$'$ bosons
decaying into this final state. An interpretation is also made in the context
of an R parity violating supersymmetric model with a slepton as a mediator and
flavor violating decay. | hep-ex |
Measurement of the effective weak mixing angle at the CEPC: We present a study of the measurement of the effective weak mixing angle
parameter ($\sin^2\theta^{\ell}_\text{eff}$) at the Circular Electron Positron
Collider (CEPC). As a fundamental physics parameter,
$\sin^2\theta^{\ell}_\text{eff}$ plays a key role not only in the global test
of the standard model electroweak sector, but also in constraining the
potential beyond standard model new physics at high energy frontier. CEPC
proposes a two year running period around the Z boson mass pole at high
instataneous luminosity, providing a large data sample with $4\times 10^{12}$
$Z$ candidates generated in total. It allows a high precision measurement of
$\sin^2\theta^{\ell}_\text{eff}$ both in the lepton and quark final states, of
which the uncertainty can be one order of magnitude lower than any previous
measurement at the LEP, SLC, Tevatron and LHC. It will not only improve the
overall precision of the $\sin^2\theta^\ell_\text{eff}$ experimental
determination to be comparable to the preicision of the theoretical calculation
with two-loop radiative corrections, but also provide direct comparisons
between different final states. In this paper, we also study the measurement of
$\sin^2\theta^{\ell}_\text{eff}$ at high mass region. With one month data
taken, the precision of $\sin^2\theta^{\ell}_\text{eff}$ measured at 130 GeV
from $b$ quark final state is 0.00010, which will be an important experimental
observation on the energy-running effect of $\sin^2\theta^{\ell}_\text{eff}$. | hep-ex |
Total Cross Section in gamma gamma Collisions at LEP: The reaction e+e- -> e+e- gamma* gamma* -> e+e- hadrons for quasi-real
photons is studied using data from root(s) = 183 GeV up to 202 GeV.
Results on the total cross sections sigma(e+e- -> e+e- hadrons) and sigma(+e-
gamma* gamma* -> e+e- hadrons) are given for the two-photon centre-of-mass
energies 5 GeV < Wgammagamma < 185 GeV.
The total cross section of two real photons is described by a Regge
parametrisation. We observe a steeper rise with the two-photon centre-of-mass
energy as compared to the hadron-hadron and the photon-proton cross sections.
The data are also compared to the expectations of different theoretical models. | hep-ex |
Measurement of associated production of vector bosons and top
quark-antiquark pairs at sqrt(s) = 7 TeV: The first measurement of vector-boson production associated with a top
quark-antiquark pair in proton-proton collisions at sqrt(s) = 7 TeV is
presented. The results are based on a data set corresponding to an integrated
luminosity of 5.0 inverse femtobarms, recorded by the CMS detector at the LHC
in 2011. The measurement is performed in two independent channels through a
trilepton analysis of t t-bar Z events and a same-sign dilepton analysis of t
t-bar V (V = W or Z) events. In the trilepton channel a direct measurement of
the t t-bar Z cross section sigma(t t-bar Z) = 0.28 +0.14/-0.11 (stat)
+0.06/-0.03 (syst) pb is obtained. In the dilepton channel a measurement of the
t t-bar V cross section yields sigma(t t-bar V) = 0.43 +0.17/-0.15 (stat)
+0.09/-0.07 (syst) pb. These measurements have a significance, respectively, of
3.3 and 3.0 standard deviations from the background hypotheses and are
compatible, within uncertainties, with the corresponding next-to-leading order
predictions of 0.137 +0.012/-0.016 and 0.306 +0.031/-0.053 pb. | hep-ex |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.