text
stringlengths 89
2.49k
| category
stringclasses 19
values |
|---|---|
Study of a narrow pi+ pi- peak at about 755 MeV/c^2 in bar-p n --> 2 pi+
3 pi- annihilation at rest: A narrow peak in the pi+ pi- mass distribution was seen by the Rome-Syracuse
Collaboration in bar-p n --> 2 pi+ 3 pi- annihilation at rest 39 years ago. The
reanalysis of this peak finds a mass of 757.4 +- 2.6 MeV/c^2 and a width
slightly narrower than the experimental resolution. The evidence of the peak is
5.2 standard deviations. This state is generated in (12.4 +- 2.4)% of the bar-p
n --> 2 pi+ 3 pi- annihilations at rest. No spin analysis is possible with the
statistics of the experiment. | hep-ex |
Search for Photon-Photon Elastic Scattering in the X-ray Region: We report the first results of a search for real photon-photon scattering
using X rays. A novel system is developed to split and collide X-ray pulses by
applying interferometric techniques. A total of $6.5\times10^{5}$ pulses (each
containing about $10^{11}$ photons) from an X-ray Free-Electron Laser are
injected into the system. No scattered events are observed, and an upper limit
of $1.7\times 10^{-24}$ ${\rm m^{2}}$ (95% C.L.) is obtained on the
photon-photon elastic scattering cross section at 6.5 keV. | hep-ex |
Ultimate sensitivity on gamma/phi3 from B->DK: Measurement of the CKM phase gamma in B->DK decays can be potentially
performed with high precision due to low theoretical uncertainties. However,
the precision measurement requires very large experimental samples of B decays.
This report covers prospects for gamma measurement at the future e+e-
facilities and upgraded LHCb detector. | 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 |
New New-Phenomena Results from Dzero: We have searched for diphoton events (\ggmet) with large missing transverse
momentum, $\gamma\rlap{\kern0.25em/}E_T$ events (\gmetjj) with two or more
jets, and diphoton events ($\gamma\gamma$) with high transverse energies in
$p\bar p$ collisions at $\sqrt{s} = 1.8$ TeV using approximately 100~pb$^{-1}$
of data collected with the D\O detector at the Fermilab Tevatron in 1992--1996.
No excess of events beyond the expected backgrounds is observed. The null
results are interpreted in supersymmetric models with a dominant
$\tilde\chi^0_2\to\gamma\tilde\chi^0_1$ decay and in terms of Dirac pointlike
monopole production. | hep-ex |
Determination of electroweak parameters in polarised deep-inelastic
scattering at HERA: The parameters of the electroweak theory are determined in a combined
electroweak and QCD analysis using all deep-inelastic $e^+p$ and $e^-p$ neutral
current and charged current scattering cross sections published by the H1
Collaboration, including data with longitudinally polarised lepton beams.
Various fits to Standard Model parameters in the on-shell scheme are performed.
The mass of the $W$ boson is determined as $m(W)=80.520\pm 0.115$ GeV. The
axial-vector and vector couplings of the light quarks to the $Z$ boson are also
determined. Both results improve the precision of previous H1 determinations
based on HERA-I data by about a factor of two. Possible scale dependence of the
weak coupling parameters in both neutral and charged current interactions
beyond the Standard Model is also studied. All results are found to be
consistent with the Standard Model expectations. | hep-ex |
Measurement of the forward charged particle pseudorapidity density in pp
collisions at sqrt{s} = 7 TeV with the TOTEM experiment: The TOTEM experiment has measured the charged particle pseudorapidity density
dN_{ch}/deta in pp collisions at sqrt{s} = 7 TeV for 5.3<|eta|<6.4 in events
with at least one charged particle with transverse momentum above 40 MeV/c in
this pseudorapidity range. This extends the analogous measurement performed by
the other LHC experiments to the previously unexplored forward eta region. The
measurement refers to more than 99% of non-diffractive processes and to single
and double diffractive processes with diffractive masses above ~3.4 GeV/c^2,
corresponding to about 95% of the total inelastic cross-section. The
dN_{ch}/deta has been found to decrease with |eta|, from 3.84 pm 0.01(stat) pm
0.37(syst) at |eta| = 5.375 to 2.38 pm 0.01(stat) pm 0.21(syst) at |eta| =
6.375. Several MC generators have been compared to data; none of them has been
found to fully describe the measurement. | hep-ex |
Prospect for precision measurements of MW+ -MW- & MW at the LHC:
Shortcuts revisited: The claim that the W boson mass might be measured at the LHC with a precision
of O(10 MeV) is critically reviewed. It is argued that such a precision cannot
be achieved, unless a dedicated measurement program, specific to the LHC is
pursued. We propose such a program. Its main target is to significantly improve
the experimental control of the relative polarisation of the W+, W- and Z
bosons. We propose to achieve this goal either by running dedicated isoscalar
beams at the LHC or by running, in parallel to the standard p-p collision
program, a dedicated muon scattering "LHC-support-experiment" at the CERN SPS.
One of these auxiliary measurements is necessary for the "precision measurement
program" at the LHC, but not sufficient. It must be followed by dedicated
measurement strategies which are robust with respect to both the systematic
measurement uncertainties and to the perturbative and non-perturbative QCD
effects. We propose such strategies and evaluate their precision. At the LHC,
contrary to the Tevatron case, both the masses of the W+ and of the W- bosons
must be measured with high precision. In this context, we propose and evaluate
LHC dedicated strategies to measure the difference of the masses of the W+ and
W- bosons and of the absolute mass of the W boson assuming both masses are
equal. We show how one can overcome the obstacles in measuring the masses of W+
and W- to a precision of 10 MeV. We present a detailed evaluation of the
precision of the proposed methods based on the studies of a large, O(10^11),
sample of simulated W and Z production events. | hep-ex |
Search for Proton Decay into Muon plus Neutral Kaon in Super-Kamiokande
I, II, and III: We have searched for proton into muon plus neutral kaon using data from a
91.7 kiloton-year exposure of Super-Kamiokande-I, a 49.2 kiloton-year exposure
of Super-Kamiokande-II, and a 31.9 kiloton-year exposure of
Super-Kamiokande-III. The number of candidate events in the data was consistent
with the atmospheric neutrino background expectation and no evidence for proton
decay in this mode was found. We set a partial lifetime lower limit of
1.6x10^33 years at the 90% confidence level. | hep-ex |
Search for WH production with a light Higgs boson decaying to prompt
electron-jets in proton-proton collisions at sqrt(s)=7 TeV with the ATLAS
detector: A search is performed for WH production with a light Higgs boson decaying to
hidden-sector particles resulting in clusters of collimated electrons, known as
electron-jets. The search is performed with 2.04 fb-1 of data collected in 2011
with the ATLAS detector at the LHC in proton-proton collisions at sqrt(s)=7
TeV. One event satisfying the signal selection criteria is observed, which is
consistent with the expected background rate. Limits on the product of the WH
production cross section and the branching ratio of a Higgs boson decaying to
prompt electron-jets are calculated as a function of a Higgs boson mass in the
range from 100 GeV to 140 GeV. | hep-ex |
Recent progress on the study of the charmoniumlike states: In this article, we review the recent experimental studies on the
charmoniumlike states, mainly from the e+e- annihilation experiments BESIII,
Belle, BaBar, and CLEO-c, and the hadron collider experiment LHCb. We discuss
the results on the X(3872), the vector Y states [Y(4008), Y(4660), and those in
e+e- to pi+pi-h_c], and the charged charmoniumlike Z_c^- states. | hep-ex |
New Results from the Muon g-2 Experiment: The Muon g-2 collaboration has measured the anomalous magnetic g value, a =
(g-2)/2, of the positive muon with an unprecedented uncertainty of 0.7 parts
per million. The result, based on data collected in the year 2000 at Brookhaven
National Laboratory, is in good agreement with the preceding data. The
measurement tests standard model theory, which at the level of the current
experimental uncertainty involves quantum electrodynamics, quantum
chromodynamics, and electroweak interaction in a significant way. | hep-ex |
Search for Dark Photons in $γγ\rightarrow e^+e^-$ at RHIC: The fundamental nature of Dark Matter remains one of the major mysteries of
modern physics. Some models postulate the existence of a massive gauge boson, a
"dark photon" ($A^\prime$), that may allow Dark Matter particles to interact
with Standard Model particles. Ultra-relativistic heavy-ion collisions produce
highly Lorentz-contracted electromagnetic fields with sufficient energy density
to potentially manifest as light dark photons. We report limits on dark photon
parameters via a search for anomalous production of $e^+e^-$ pairs in $\gamma
A^\prime$ and $A^\prime A^\prime$ fusion from ultra-peripheral
$\rm{Au}+\rm{Au}$ collisions. This study utilizes measurements of the
Breit-Wheeler process ($\gamma\gamma \rightarrow e^+e^-$) carried out by STAR,
specifically making use of polarization-dependent final-state azimuthal
asymmetries in $e^+e^-$ pairs. These limits are informative for future searches
in the ultra-peripheral heavy-ion collisions and to constrain future
theoretical developments of the dark photon mechanism. | hep-ex |
Deep Underground Neutrino Experiment (DUNE), Far Detector Technical
Design Report, Volume II: DUNE Physics: The preponderance of matter over antimatter in the early universe, the
dynamics of the supernovae that produced the heavy elements necessary for life,
and whether protons eventually decay -- these mysteries at the forefront of
particle physics and astrophysics are key to understanding the early evolution
of our universe, its current state, and its eventual fate. DUNE is an
international world-class experiment dedicated to addressing these questions as
it searches for leptonic charge-parity symmetry violation, stands ready to
capture supernova neutrino bursts, and seeks to observe nucleon decay as a
signature of a grand unified theory underlying the standard model.
The DUNE far detector technical design report (TDR) describes the DUNE
physics program and the technical designs of the single- and dual-phase DUNE
liquid argon TPC far detector modules. Volume II of this TDR, DUNE Physics,
describes the array of identified scientific opportunities and key goals.
Crucially, we also report our best current understanding of the capability of
DUNE to realize these goals, along with the detailed arguments and
investigations on which this understanding is based.
This TDR volume documents the scientific basis underlying the conception and
design of the LBNF/DUNE experimental configurations. As a result, the
description of DUNE's experimental capabilities constitutes the bulk of the
document. Key linkages between requirements for successful execution of the
physics program and primary specifications of the experimental configurations
are drawn and summarized.
This document also serves a wider purpose as a statement on the scientific
potential of DUNE as a central component within a global program of frontier
theoretical and experimental particle physics research. Thus, the presentation
also aims to serve as a resource for the particle physics community at large. | hep-ex |
Open Heavy Flavor Production in Deeply Inelastic ep Scattering at HERA: Recent results on inclusive D^0 and D^{*+-} production in deeply inelastic ep
scattering at sqrt(s)=301 GeV are summarized. The data have been collected by
the H1 and ZEUS experiments at HERA. The total and the differential cross
sections are discussed in the framework of LO and NLO QCD predictions. The data
exhibit clear evidence for boson gluon fusion dominating open heavy flavor
production in the kinematic range currently explored at HERA. The measurements
of F_2^{cc}(x,Q^2) at small Bjorken x are presented. The prospects for future
analyses of open charm and beauty production including detector upgrades and
anticipated high luminosities are investigated. | hep-ex |
On the Energy Spectrum of Cosmogenic Neutrons: The processes of the generation of cosmogenic neutrons (cg-neutrons)
underground are considered. The neutrons produced by cosmic-ray muons in their
interactions with matter are called cosmogenic. Deep-inelastic
${\pi}A$-collisions of pions in muon-induced hadronic showers are mainly their
source at energies above 30 MeV. The characteristics of the energy spectrum for
the generation of cg-neutrons have been determined by invoking the additive
quark model of deep-inelastic soft processes and the mechanism for the
interactions of high-energy nucleons in a nucleus. The three-component shape of
the spectrum is explained, and the energy of the "knee" in the spectrum has
been found to depend on the mass number $A$. The peculiarities of
deep-inelastic ${\pi}A$-scattering lead to the conclusion that the spectrum of
cg-neutrons steepens sharply at energies above 1 GeV. The calculated
quantitative characteristics of the spectrum are compared with those obtained
in measurements. | hep-ex |
Recent QCD results from OPAL: Some recent QCD results from the OPAL Collaboration are summarized. In
particular: a test of color reconnection models and a search for glueballs
using gluon jets with a rapidity gap; a study of unbiased gluon jet properties
using a new technique called jet boost algorithm; a measurement of the strong
coupling constant from radiative events. | hep-ex |
Results and Future Prospects for Muon (g-2): Spin physics had its beginnings in the famous experiments of Stern and
Gerlach, which eventually resulted in the postulation of spin by Goudsmit and
Uhlenbeck. The Stern-Gerlach experiment told us that the $g$-value of the
electron was 2, but we now know that because of radiative corrections, the
$g$-value of the leptons is slightly greater than 2, the lowest-order
contribution being $\alpha/\pi$, where $\alpha$ is the fine-structure constant.
Measurements of the magnetic dipole moments of the electron and muon have
played a major role in our understanding of QED and of the standard model. In
this talk I discuss the progress on measurements and theory of the magnetic
dipole moment of the muon. | hep-ex |
Neutral pion photoproduction off protons in the energy range 0.3 GeV <
E(gamma) < 3 GeV: Single pi0 photoproduction has been studied with the CB-ELSA experiment at
Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental
setup covers a very large solid angle of about 98% of 4 pi. Differential cross
sections (d sigma)/(d Omega) have been measured. Complicated structures in the
angular distributions indicate a variety of different resonances being produced
in the s channel intermediate state gamma p --> N* (Delta*) --> p pi0. A
combined analysis including the data presented in this letter along with other
data sets reveals contributions from known resonances and evidence for a new
resonance N(2070)D15. | hep-ex |
Search for pseudoscalar bosons decaying into $e^+e^-$ pairs in the NA64
experiment at the CERN SPS: We report the results of a search for a light pseudoscalar particle $a$ that
couples to electrons and decays to $e^+e^-$ performed using the high-energy
CERN SPS H4 electron beam. If such pseudoscalar with a mass $\simeq 17$ MeV
exists, it could explain the ATOMKI anomaly. We used the NA64 data samples
collected in the "visible mode" configuration with total statistics
corresponding to $8.4\times 10^{10}$ electrons on target (EOT) in 2017 and
2018. In order to increase sensitivity to small coupling parameter $\epsilon$
we used also the data collected in 2016-2018 in the "invisible mode"
configuration of NA64 with a total statistics corresponding to $2.84\times
10^{11}$ EOT. A thorough analysis of both these data samples in the sense of
background and efficiency estimations was already performed and reported in our
previous papers devoted to the search for light vector particles and axion-like
particles (ALP). In this work we recalculate the signal yields, which are
different due to different cross section and life time of a pseudoscalar
particle $a$, and perform a new statistical analysis. As a result, the region
of the two dimensional parameter space $m_a - \epsilon$ in the mass range from
1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of
$\epsilon$ in the range $2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}$
are excluded. | hep-ex |
Observation of Hyperfine Transitions in Trapped Ground-State
Antihydrogen: This paper discusses the first observation of stimulated magnetic resonance
transitions between the hyperfine levels of trapped ground state atomic
antihydrogen, confirming its presence in the ALPHA apparatus. Our observations
show that these transitions are consistent with the values in hydrogen to
within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave
field are consistent with our measurements. | hep-ex |
Determination of the strangeness content of light-flavour isoscalars
from their production rates in hadronic Z decays at LEP: A new phenomenological approach is suggested for determining the strangeness
content of light-flavour isoscalars. This approach is based on phenomenological
laws of hadron production related to the spin, isospin, strangeness content and
mass of the particles. From the total production rates per hadronic Z decay of
all light-flavour hadrons, measured so far at LEP, the values of the
nonstrange-strange mixing angles are found to be |\phi_P| = 42.3^{\circ} \pm
3.5^{\circ}, |\phi_V| = 10^{\circ} \pm 8^{\circ}, |\phi_T| = 16^{\circ} \pm
11^{\circ} and |\phi_S| = 13^{\circ} \pm 9^{\circ}. Our results on the
\eta-\eta^{\prime}, \omega-\phi and f_2-f_2^{\prime} isoscalar mixing are
consistent with the present experimental evidence. The strangeness content
obtained for the f_0(980) scalar/isoscalar is not consistent with the values
supported by recent model studies and is discussed further in the framework of
our approach and the K-matrix analysis. | hep-ex |
Neural-network-driven proton decay sensitivity in the $p\rightarrow
\barν K^{+}$ channel using large liquid argon time projection chambers: We report on an updated sensitivity for proton decay via $p \rightarrow
\bar{\nu} K^+ $ at large, dual phase liquid argon time projection chambers (LAr
TPCs). Our work builds on a previous study in which several nucleon decay
channels have been simulated and analyzed [arXiv:hep-ph/0701101]. At the time
several assumptions were needed to be made on the detector and the backgrounds.
Since then, the community has made progress in defining these, and the
computing power available enables us to fully simulate and reconstruct large
samples in order to perform a better estimate of the sensitivity to proton
decay. In this work, we examine the benchmark channel $p\rightarrow \bar{\nu}
K^{+}$, which was previously found to be one of the cleanest channels. Using an
improved neutrino event generator and a fully simulated LAr TPC detector
response combined with a dedicated neural network for kaon identification, we
demonstrate that a lifetime sensitivity of $ \tau / \text{Br} \left( p
\rightarrow \bar{\nu} K^+ \right) > 7 \times 10^{34} \, \text{years}$ at $90 \,
\%$ confidence level can be reached at an exposure of $1 \, \text{megaton}
\cdot \text{year}$ in quasi-background-free conditions, confirming the
superiority of the LAr TPC over other technologies to address the challenging
proton decay modes. | hep-ex |
Search for supersymmetry in pp collisions at sqrt(s) = 13 TeV in the
single-lepton final state using the sum of masses of large-radius jets: Results are reported from a search for supersymmetric particles in
proton-proton collisions in the final state with a single, high transverse
momentum lepton; multiple jets, including at least one b-tagged jet; and large
missing transverse momentum. The data sample corresponds to an integrated
luminosity of 2.3 inverse femtobarns at sqrt(s) = 13 TeV, recorded by the CMS
experiment at the LHC. The search focuses on processes leading to high jet
multiplicities, such as gluino pair production with gluinos to t t-bar
neutralino[1]. The quantity M[J], defined as the sum of the masses of the
large-radius jets in the event, is used in conjunction with other kinematic
variables to provide discrimination between signal and background and as a key
part of the background estimation method. The observed event yields in the
signal regions in data are consistent with those expected for standard model
backgrounds, estimated from control regions in data. Exclusion limits are
obtained for a simplified model corresponding to gluino pair production with
three-body decays into top quarks and neutralinos. Gluinos with a mass below
1600 GeV are excluded at a 95% confidence level for scenarios with low
neutralino[1] mass, and neutralinos with a mass below 800 GeV are excluded for
a gluino mass of about 1300 GeV. For models with two-body gluino decays
producing on-shell top squarks, the excluded region is only weakly sensitive to
the top squark mass. | hep-ex |
$J/ψ$ and $ψ(2S)$ production at forward rapidity in $p$+$p$
collisions at $\sqrt{s}=510$ GeV: The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the
differential cross section, mean transverse momentum, mean transverse momentum
squared of inclusive $J/\psi$ and cross-section ratio of $\psi(2S)$ to $J/\psi$
at forward rapidity in \pp collisions at \sqrts = 510 GeV via the dimuon decay
channel. Comparison is made to inclusive $J/\psi$ cross sections measured at
\sqrts = 200 GeV and 2.76--13 TeV. The result is also compared to leading-order
nonrelativistic QCD calculations coupled to a color-glass-condensate
description of the low-$x$ gluons in the proton at low transverse momentum
($p_T$) and to next-to-leading order nonrelativistic QCD calculations for the
rest of the $p_T$ range. These calculations overestimate the data at low $p_T$.
While consistent with the data within uncertainties above $\approx3$ GeV/$c$,
the calculations are systematically below the data. The total cross section
times the branching ratio is BR $d\sigma^{J/\psi}_{pp}/dy (1.2<|y|<2.2,
0<p_T<10~\mbox{GeV/$c$}) =$ 54.3 $\pm$ 0.5 (stat) $\pm$ 5.5 (syst) nb. | hep-ex |
Inclusive jet cross section in ${\bar p p}$ collisions at $\sqrt{s}=1.8$
TeV: The inclusive jet differential cross section has been measured for jet
transverse energies, $E_T$, from 15 to 440 GeV, in the pseudorapidity region
0.1$\leq | \eta| \leq $0.7. The results are based on 19.5 pb$^{-1}$ of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with $E_T>200$ GeV is significantly
higher than current predictions based on O($\alpha_s^3$) perturbative QCD
calculations. Various possible explanations for the high-$E_T$ excess are
discussed. | hep-ex |
Higher-order multipole amplitudes in charmonium radiative transitions: Using 24 million $\psi' \equiv \psi(2S)$ decays in CLEO-c, we have searched
for higher multipole admixtures in electric-dipole-dominated radiative
transitions in charmonia. We find good agreement between our data and
theoretical predictions for magnetic quadrupole (M2) amplitudes in the
transitions $\psi' \to \gamma \chi_{c1,2}$ and $\chi_{c1,2} \to \gamma J/\psi$,
in striking contrast to some previous measurements. Let $b_2^J$ and $a_2^J$
denote the normalized M2 amplitudes in the respective aforementioned decays,
where the superscript $J$ refers to the angular momentum of the $\chi_{cJ}$. By
performing unbinned maximum likelihood fits to full five-parameter angular
distributions, we determine the ratios $a_2^{J=1}/a_2^{J=2} =
0.67^{+0.19}_{-0.13}$ and $a_2^{J=1}/b_2^{J=1} = -2.27^{+0.57}_{-0.99}$, where
the theoretical predictions are independent of the charmed quark magnetic
moment and are $a_2^{J=1}/a_2^{J=2} = 0.676 \pm 0.071$ and $a_2^{J=1}/b_2^{J=1}
= -2.27 \pm 0.16$. | hep-ex |
First Jet and High $\pT$ Measuerements with the ALICE Experiment at the
LHC: The Large Hadron Collider at CERN currently provides p$+$p collisions at
center of mass energies of $\sqrt{s} = 7$~TeV, which allow to study high $\pT$
particle production and jet properties in a new energy regime. For a clear
interpretation and the quantification of the medium influence in heavy-ion
collisions on high $\pT$ observables a detailed understanding of these
elementary reactions is essential. We present first results on the observation
of jet-like properties with the ALICE experiment and discuss the performance of
jet reconstruction in the first year of data taking. | hep-ex |
LHC analysis-specific datasets with Generative Adversarial Networks: Using generative adversarial networks (GANs), we investigate the possibility
of creating large amounts of analysis-specific simulated LHC events at limited
computing cost. This kind of generative model is analysis specific in the sense
that it directly generates the high-level features used in the last stage of a
given physics analyses, learning the N-dimensional distribution of relevant
features in the context of a specific analysis selection. We apply this idea to
the generation of muon four-momenta in $Z \to \mu\mu$ events at the LHC. We
highlight how use-case specific issues emerge when the distributions of the
considered quantities exhibit particular features. We show how substantial
performance improvements and convergence speed-up can be obtained by including
regression terms in the loss function of the generator. We develop an objective
criterion to assess the geenrator performance in a quantitative way. With
further development, a generalization of this approach could substantially
reduce the needed amount of centrally produced fully simulated events in large
particle physics experiments. | hep-ex |
Future Prospects at Electron-Positron Machines: This review will present the future prospects for physics at
electron-positron colliders running near the Upsilon(4S) as well as at the
charm and tau thresholds. It includes a review of the Belle II and SuperB
projects. Also reviewed are the plans for BES III, which operates near the
charm threshold at the IHEP BEPC machine in Bejing and the status of the Super
Charm/Tau Factory proposed for the Budker Institute for Nuclear Physics (BINP)
in Novosibirsk. | hep-ex |
Measurement of the $W \to e ν$ and $Z/γ^* \to e^+e^-$ Production
Cross Sections at Mid-rapidity in Proton-Proton Collisions at $\sqrt{s}$ =
500 GeV: We report measurements of the charge-separated $W^{+(-)} \to e^{+(-)} +
\nu_e(\bar{\nu}_e)$ and $Z/\gamma^* \to e^+e^-$ production cross sections at
mid-rapidity in proton-proton collisions at $\sqrt{s}$ = 500 GeV. These results
are based on 13.2 pb$^{-1}$ of data recorded in 2009 by the STAR detector at
RHIC. Production cross sections for W bosons that decay via the $e \nu$ channel
were measured to be $\sigma(pp \to W^+ X) \cdot BR(W^+ \to e^+ \nu_e)$ = 117.3
\pm 5.9(stat) \pm 6.2(syst) \pm 15.2(lumi) pb, and $\sigma(pp \to W^- X) \cdot
BR(W^- \to e^- \bar{\nu}_e)$ = 43.3 \pm 4.6(stat) \pm 3.4(syst) \pm 5.6(lumi)
pb. For $Z/\gamma^*$ production, $\sigma(pp \to Z/\gamma^* X) \cdot
BR(Z/\gamma^* \to e^+ e^-)$ = 7.7 \pm 2.1(stat) $^{+0.5}_{-0.9}$(syst) \pm
1.0(lumi) pb for di-lepton invariant masses $m_{e^+e^-}$ between 70 and 110
GeV/$c^2$. First measurements of the W cross section ratio, $\sigma(pp \to W^+
X) / \sigma(pp \to W^- X)$, at $\sqrt{s}$ = 500 GeV are also reported.
Theoretical predictions, calculated using recent parton distribution functions,
are found to agree with the measured cross sections. | hep-ex |
The GENIUS Project - Background and technical studies: The potential of GENIUS as a dark matter detector is discussed. A study was
performed to demonstrate the good behaviour of the proposed detector design of
naked HPGe-crystals in liquid nitrogen. The expected background components were
simulated and are discussed in some detail.With the obtained background GENIUS
could cover a large part of the favoured MSSM parameter-space. | hep-ex |
J/$ψ$ and $ψ$(2S) production in p-Pb collisions at
$\sqrt{s_{NN}}=\mathrm{5.02}$ TeV with ALICE at the LHC: The ALICE Collaboration has studied the inclusive J/$\psi$ and
$\psi(\mathrm{2S})$ production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02
TeV, at the CERN LHC. The J/$\psi$ measurement is performed in the
$\mu^{+}\mu^{-}$ and in the $e^{+}e^{-}$ decay channels, down to zero
$p_{\mathrm{T}}$. The results are in fair agreement with theoretical
predictions. The $\psi(\mathrm{2S})$ measurement has also been performed. In
particular, a smaller $\psi(\mathrm{2S})$ nuclear modification factor, with
respect to the J$/\psi$ one, has been observed. | hep-ex |
Measurement of the $K^+\toπ^+γγ$ decay: A sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an
estimated background of $291\pm14$ events, was collected by the NA62 experiment
at CERN during 2017-2018. In order to describe the observed di-photon mass
spectrum, the next-to-leading order contribution in chiral perturbation theory
was found to be necessary. The decay branching ratio in the full kinematic
range is measured to be $(9.61\pm0.17)\times10^{-7}$. The first search for
production and prompt decay of an axion-like particle with gluon coupling in
the process $K^+\to\pi^+a$, $a\to\gamma\gamma$ is also reported. | hep-ex |
Search for new physics in final states with an energetic jet or a
hadronically decaying W or Z boson and transverse momentum imbalance at
$\sqrt{s} = $ 13 TeV: A search for new physics using events containing an imbalance in transverse
momentum and one or more energetic jets arising from initial-state radiation or
the hadronic decay of W or Z bosons is presented. A data sample of
proton-proton collisions at $\sqrt{s} = $ 13 TeV, collected with the CMS
detector at the LHC and corresponding to an integrated luminosity of 35.9
fb$^{-1}$, is used. The observed data are found to be in agreement with the
expectation from standard model processes. The results are interpreted as
limits on the dark matter production cross section in simplified models with
vector, axial-vector, scalar, and pseudoscalar mediators. Interpretations in
the context of fermion portal and nonthermal dark matter models are also
provided. In addition, the results are interpreted in terms of invisible decays
of the Higgs boson and set stringent limits on the fundamental Planck scale in
the Arkani-Hamed, Dimopoulos, and Dvali model with large extra spatial
dimensions. | hep-ex |
Search for the Standard Model Higgs Boson at LEP: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have collected 2465
pb-1 of e+e- collision data at energies between 189 and 209 GeV, of which 542
pb-1 were collected above 206 GeV. Searches for the Standard Model Higgs boson
have been performed by each of the LEP collaborations. Their data have been
combined and examined for their consistency with the Standard Model background
and various Standard Model Higgs boson mass hypotheses. A lower bound of 114.1
GeV has been obtained at the 95% confidence level for the mass of the Higgs
boson. The likelihood analysis shows a preference for a Higgs boson with a mass
of 115.6 GeV. At this mass, the probability for the background to generate the
observed effect is 3.4%. | hep-ex |
Searches for New Neutral Gauge Bosons and Leptoquarks at the Tevatron: This contribution reports on some of the most recent searches for new heavy
neutral bosons and leptoquarks performed at the Tevatron experiments. | hep-ex |
Experimental investigation of transverse spin asymmetries in muon-p
SIDIS processes: Collins asymmetries: The COMPASS Collaboration at CERN has measured the transverse spin azimuthal
asymmetry of charged hadrons produced in semi-inclusive deep inelastic
scattering using a 160 GeV positive muon beam and a transversely polarised NH_3
target. The Collins asymmetry of the proton was extracted in the Bjorken x
range 0.003<x<0.7. These new measurements confirm with higher accuracy previous
measurements from the COMPASS and HERMES collaborations, which exhibit a
definite effect in the valence quark region. The asymmetries for negative and
positive hadrons are similar in magnitude and opposite in sign. They are
compatible with model calculations in which the u-quark transversity is
opposite in sign and somewhat larger than the d-quark transversity distribution
function. The asymmetry is extracted as a function of Bjorken $x$, the relative
hadron energy $z$ and the hadron transverse momentum p_T^h. The high statistics
and quality of the data also allow for more detailed investigations of the
dependence on the kinematic variables. These studies confirm the leading-twist
nature of the Collins asymmetry. | hep-ex |
B Physics at the Tevatron Run II: We present the B physics results from the CDF and D{\O} experiments at the
Tevatron Run II at Fermilab and their future prospect. This includes various B
mass and lifetime measurements, B mixing, the confirmation of the discovery of
the X particle, rare decays, CP violation and spectroscopy. | hep-ex |
Search for resonant top plus jet production in ttbar + jets events with
the ATLAS detector in pp collisions at sqrt(s) = 7 TeV: This paper presents a search for a new heavy particle produced in association
with a top or antitop quark. Two models in which the new heavy particle is a
color singlet or a color triplet are considered, decaying respectively to tbarq
or tq, leading to a resonance within the ttbar + jets signature. The full 2011
ATLAS pp collision dataset from the LHC (4.7 fb-1) is used to search for ttbar
events produced in association with jets, in which one of the W bosons from the
top quarks decays leptonically and the other decays hadronically. The data are
consistent with the Standard Model expectation, and a new particle with mass
below 430 GeV for both W boson and color triplet models is excluded at 95%
confidence level, assuming unit right-handed coupling. | hep-ex |
Inclusive Measurements of $B \to X_c\ellν$ and $B \to X_sγ$
Decays: A mini-review of measurements of inclusive semileptonic $B \to X_c\ell\nu$
and radiative $B\to X_s\gamma$ decays is presented. The semileptonic $X_c$ mass
moments are presented from Belle and BABAR. The inclusive $B\to X_s\gamma$
gamma branching fraction is presented from Belle as well as a preliminary
measurement of the direct CP-asymmetry of $B \to X_{s+d}\gamma$ decays at
BABAR. Fundamental Standard Model parameters and heavy quark parameters can be
derived from the $X_c$ mass and lepton energy moments from $B \to X_c\ell\nu$
decays and from the photon energy moments from $B \to X_s\gamma$ decays. The
values of the CKM matrix element $|V_{cb}|$, the $b$-quark mass $m_b$, and the
Fermi motion of the $b$-quark inside the $B$-meson are presented based on a
global fit to these moments by the Heavy Flavor Averaging Group. | hep-ex |
Top-quark mass measurement using events with missing transverse energy
and jets at CDF: We present a measurement of the top-quark mass using a sample of $t\bar{t}$
events in 5.7 fb$^{-1}$ of integrated luminosity from $p\bar{p}$ collisions at
the Fermilab Tevatron with $\sqrt{s} =$ 1.96 TeV and collected by the CDF II
Detector. We select events having no identified charged leptons, large missing
transverse energy, and four, five, or six jets with at least one jet tagged as
coming from a $b$ quark. This analysis considers events from the semileptonic
\ttbar decay channel, including events that contain tau leptons. The
measurement is based on a multidimensional template method. We fit the data to
signal templates of varying top-quark masses and background templates, and
measure a top-quark mass of $\mtop = \gevcc{\measStatSyst{172.3}{2.4}{1.0}}$. | hep-ex |
Single Spin Asymmetries on a transversely polarised proton target at
COMPASS: COMPASS is a running fixed-target experiment at the CERN SPS with a rich
physics program focused on nucleon spin structure and on hadron spectroscopy.
One of the main goals of the spin program is the measurement of the transverse
spin effects in semi-inclusive DIS off transversely polarised nucleons. In the
years 2002, 2003 and 2004 data have been taken using a 160 $GeV/c$ naturally
polarised $\mu^{+}$ beam and a deuterium target ($^{6}LiD$) transversely
polarised respect to the beam direction. In 2007 the run year has been devoted
to collect data with a proton ($NH_{3}$) target. The preliminary results for
the Collins and Sivers asymmetries, extracted from the 2007 data with
transverse target polarisation, are presented here. Results are also compared
with existing model predictions. | hep-ex |
Correlations between D and $\bar{D}$ mesons produced in 500 GeV/c
$π^-$-nucleon interactions: We present a study of correlations between D and $\bar{D}$ mesons produced in
500 GeV/$c$ $\pi^-$-nucleon interactions, based on data from experiment E791 at
Fermilab. We have fully reconstructed $791 \pm 44$ charm meson pairs to study
correlations between the transverse and longitudinal momenta of the two D
mesons and the relative production rates for different types of D meson pairs.
We see slight correlations between the longitudinal momenta of the D and the
$\bar D$, and significant correlations between the azimuthal angle of the D and
the $\bar D$. The experimental distributions are compared to a
next-to-leading-order QCD calculation and to predictions of the {\sc
Pythia/Jetset} Monte Carlo event generator. We observe less correlation between
transverse momenta and different correlations between longitudinal momenta than
these models predict for the default values of the model parameters. Better
agreement between data and theory might be achieved by tuning the model
parameters or by adding higher order perturbative terms, thus contributing to a
better understanding of charm production.
The relative production rates for the four sets of charm pairs,
$D^0\bar{D}^{0}$, $D^0D^-$, $D^+\bar{D}^{0}$, $D^+D^-$, as calculated in the
{\sc Pythia/Jetset} event generator with the default parameters, agree with
data as far as the relative ordering, but predict too many $D^+\bar{D}^{0}$
pairs and too few $D^+D^-$ pairs. | hep-ex |
DAMA/LIBRA results and perspectives: The DAMA/LIBRA experiment ($\sim$ 250 kg of highly radio-pure NaI(Tl)) is
running deep underground at the Gran Sasso National Laboratory (LNGS) of the
I.N.F.N. Here we briefly recall the results obtained in its first phase of
measurements (DAMA/LIBRA--phase1, total exposure: 1.04 ton $\times$ yr).
DAMA/LIBRA--phase1 and the former DAMA/NaI (cumulative exposure: $1.33$ ton
$\times$ yr) give evidence at 9.3 $\sigma$ C.L. for the presence of DM
particles in the galactic halo by exploiting the model-independent DM annual
modulation signature. No systematic or side reaction able to mimic the
exploited DM signature has been found or suggested by anyone over more than a
decade. At present DAMA/LIBRA--phase2 is running with increased sensitivity. | hep-ex |
Branching fraction measurements of $ψ(3686) \to γχ_{cJ}$: Using a sample of 106 million $\psi(3686)$ decays, the branching fractions of
$\psi(3686) \to \gamma \chi_{c0}, \psi(3686) \to \gamma \chi_{c1}$, and
$\psi(3686) \to \gamma \chi_{c2}$ are measured with improved precision to be
$(9.389 \pm 0.014 \pm 0.332)\,\%$, $(9.905 \pm 0.011 \pm 0.353)\,\% $, and
$(9.621 \pm 0.013 \pm 0.272)\,\% $, respectively, where the first uncertainties
are statistical and the second ones are systematic. The product branching
fractions of $\psi(3686) \to \gamma \chi_{c1}, \chi_{c1} \to \gamma J/\psi$ and
$\psi(3686) \to \gamma \chi_{c2}, \chi_{c2} \to \gamma J/\psi$ and the
branching fractions of $\chi_{c1} \to \gamma J/\psi$ and $\chi_{c2} \to \gamma
J/\psi$ are also presented. | hep-ex |
Top quark properties at CDF: We present the top property measurements in the CDF.Most of measurements
utilize close to the integrated luminosity of 3 fb$^{-1}$. | hep-ex |
Latest Results from NA48 and NA48/1: The first observations of the rare decays KS->pi0e+e- and KS->pi0mu+mu- have
been made by the NA48/1 collaboration at the CERN SPS accelerator. From high
intensity KS data collected during the 2002 run, clean signals of 7 KS->pi0e+e-
events and 6 KS->pi0mu+mu- events were observed, giving branching ratio
measurements of BR(KS->pi0e+e-) = 5.8 +2.9 -2.4 x 10^-9 and BR(KS->pi0mu+mu-) =
2.9 +1.5 -1.2 x 10^-9. These results constrain the indirect CP violating
component of the corresponding KL decays. Other recent results from NA48 are
also presented. | hep-ex |
Prospects for e+e- physics at Frascati between the phi and the psi: We present a detailed study, done in the framework of the INFN 2006 Roadmap,
of the prospects for e+e- physics at the Frascati National Laboratories. The
physics case for an e+e- collider running at high luminosity at the phi
resonance energy and also reaching a maximum center of mass energy of 2.5 GeV
is discussed, together with the specific aspects of a very high luminosity
tau-charm factory. Subjects connected to Kaon decay physics are not discussed
here, being part of another INFN Roadmap working group. The significance of the
project and the impact on INFN are also discussed. All the documentation
related to the activities of the working group can be found in
http://www.roma1.infn.it/people/bini/roadmap.html. | hep-ex |
Observation of $D^0\to K_1(1270)^- e^+ν_e$: Using 2.93 fb$^{-1}$ of $e^+e^-$ collision data taken with the BESIII
detector at a center-of-mass energy of 3.773 $\rm \,GeV$, the observation of
the $D^0\to K_1(1270)^- e^+\nu_e$ semileptonic decay is presented. The
statistical significance of the decay $D^0\to K_1(1270)^- e^+\nu_e$ is greater
than $10\sigma$. The branching fraction of $D^0\to K_1(1270)^- e^+\nu_e$ is
measured to be $(1.09\pm0.13^{+0.09}_{-0.16} \pm 0.12)\times10^{-3}$. Here, the
first uncertainty is statistical, the second is systematic, and the third
originates from the assumed branching fraction of $K_1(1270)^- \rightarrow
K^-\pi^+\pi^-$. The fraction of longitudinal polarization in $D^0\to
K_1(1270)^- e^+\nu_e$ is determined for the first time to be $0.50\pm0.19_{\rm
stat}\pm0.08_{\rm syst}$. | hep-ex |
Production of pi+, pi-, K+, K-, p and p-bar in Light (uds), c and b Jets
from Z0 Decays: We present improved measurements of the differential production rates of
stable charged particles in hadronic Z0 decays, and of charged pions, kaons and
protons identified over a wide momentum range using the SLD Cherenkov Ring
Imaging Detector. In addition to flavor-inclusive Z0 decays, measurements are
made for Z0 decays into light (u, d, s), c and b primary flavors, selected
using the upgraded Vertex Detector. Large differences between the flavors are
observed that are qualitatively consistent with expectations based upon
previously measured production and decay properties of heavy hadrons. These
results are used to test the predictions of QCD in the Modified Leading
Logarithm Approximation, with the ansatz of Local Parton-Hadron Duality, and
the predictions of three models of the hadronization process. The light-flavor
results provide improved tests of these predictions, as they do not include the
contribution of heavy-hadron production and decay; the heavy-flavor results
provide complementary model tests. In addition we have compared hadron and
antihadron production in light quark (as opposed to antiquark) jets.
Differences are observed at high momentum for all three charged hadron species,
providing direct probes of leading particle effects, and stringent constraints
on models. | hep-ex |
Search for New Physics at CDF: We present the current status of the search for new physics at CDF, using
integrated luminosity up to 3.2 fb-1. We cover searches for supersymmetry,
extra dimensions, new heavy bosons, and generic dilepton resonances. | 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 |
Measurement of the top-quark mass in t t-bar events with lepton+jets
final states in pp collisions at sqrt(s) = 7 TeV: The mass of the top quark is measured using a sample of t t-bar candidate
events with one electron or muon and at least four jets in the final state,
collected by CMS in pp collisions at sqrt(s) = 7 TeV at the LHC. A total of
5174 candidate events is selected from data corresponding to an integrated
luminosity of 5.0 inverse femtobarns. For each event the mass is reconstructed
from a kinematic fit of the decay products to a t t-bar hypothesis. The
top-quark mass is determined simultaneously with the jet energy scale (JES),
constrained by the known mass of the W boson in q anti-q decays, to be 173.49
+/- 0.43 (stat.+JES) +/- 0.98 (syst.) GeV. | hep-ex |
$B$ Meson Lifetimes at CDF: Measurements of the $B_u$, $B_d$, and $B_s$ meson lifetime using semileptonic
$B_u \rightarrow e \nu D^0 X, B_d \rightarrow e \nu D^* X, B_s \rightarrow l
\nu D_s X$ events and exclusive $B_u \rightarrow \psi^{(\prime)} K^{(*)}, B_d
\rightarrow \psi^{(\prime)} K^{(*)}_{(s)}, B_s \rightarrow \psi \phi$ events
are presented. These results used the precise position measurements of the CDF
SVX silicon vertex detector and were obtained from a 19.3 pb$^{-1}$ sample of
1.8 TeV $\overline{p}p$ collisions collected in 1992-93 at the Fermilab
Tevatron collider. Comparisons with previous measurements will be shown. | hep-ex |
Search for physics beyond the standard model in events with tau leptons,
jets, and large transverse momentum imbalance in pp collisions at sqrt(s) = 7
TeV: A search for physics beyond the standard model is performed with events
having one or more hadronically decaying tau leptons, highly energetic jets,
and large transverse momentum imbalance. The data sample corresponds to an
integrated luminosity of 4.98 inverse femtobarns of proton-proton collisions at
sqrt(s) = 7 TeV collected with the CMS detector at the LHC in 2011. The number
of observed events is consistent with predictions for standard model processes.
Lower limits on the mass of the gluino in supersymmetric models are determined. | hep-ex |
Jets in deep-inelastic scattering at HERA: Jet cross sections in deep-inelastic scattering over a wide region of phase
space have been measured at HERA. These cross section measurements provide a
thorough test of the implementation of Quantum Chromodynamics in
next-to-leading order (NLO) calculations. They also provide the opportunity to
test the consistency of the gluon distribution in the proton as extracted from
(mainly) inclusive DIS measurements. Comparison of the cross sections with NLO
enables accurate extractions of the strong coupling constant, $\alpha_s$, to be
made, several of which are reported here. | hep-ex |
Spin Physics with the PHENIX Detector System: The PHENIX experiment at RHIC has extended its scope to cover spin physics
using polarized proton beams. The major goals of the spin physics at RHIC are
elucidation of the spin structure of the nucleon and precision tests of the
symmetries. Sensitivities of the spin physics measurements with the PHENIX
detector system are reviewed. | hep-ex |
Neutrino Physics at Muon Colliders: An overview is given of the neutrino physics potential of future muon storage
rings that use muon collider technology to produce, accelerate and store large
currents of muons. | hep-ex |
CP violation in the B system: The phenomenon of CP violation is crucial to understand the asymmetry between
matter and antimatter that exists in the Universe. Dramatic experimental
progress has been made, in particular in measurements of the behaviour of
particles containing the b quark, where CP violation effects are predicted by
the Kobayashi-Maskawa mechanism that is embedded in the Standard Model. The
status of these measurements and future prospects for an understanding of CP
violation beyond the Standard Model are reviewed. | hep-ex |
Search for resonant t t-bar production in proton-proton collisions at
sqrt(s) = 8 TeV: A search is performed for the production of heavy resonances decaying into
top-antitop quark pairs in proton-proton collisions at sqrt(s) = 8 TeV. Data
used for the analyses were collected with the CMS detector and correspond to an
integrated luminosity of 19.7 inverse femtobarns. The search is performed using
events with three different final states, defined by the number of leptons
(electrons and muons) from the t t-bar to W b W b decay. The analyses are
optimized for reconstruction of top quarks with high Lorentz boosts, where jet
substructure techniques are used to enhance the sensitivity. Results are
presented for all channels and a combination is performed. No significant
excess of events relative to the expected yield from standard model processes
is observed. Upper limits on the production cross section of heavy resonances
decaying to t t-bar are calculated. A narrow leptophobic topcolor Z' resonance
with a mass below 2.4 TeV is excluded at 95% confidence level. Limits are also
derived for a broad Z' resonance with a 10% width relative to the resonance
mass, and a Kaluza-Klein excitation of the gluon in the Randall-Sundrum model.
These are the most stringent limits to date on heavy resonances decaying into
top-antitop quark pairs. | hep-ex |
Exclusive Rho Rho Production in Tagged Gamma-Gamma Interactions at LEP: Exclusive rho rho production in two-photon collisions between a quasi-real,
gamma, and a virtual, gamma*, photons is studied at LEP at centre-of-mass
energies 89 GeV < sqrt{s} < 209 GeV with a total integrated luminosity of 854.7
pb-1. The cross sections of the gamma gamma* -> rho rho processes are
determined as a function of the photon virtuality, Q^2, and the two-photon
centre-of-mass energy, Wgg, in the kinematic region: 0.2 GeV^2 < Q^2 < 30 GeV^2
and 1.1 GeV < Wgg < 3 GeV. | hep-ex |
Measurement of relative branching fractions of B decays to $ψ(2S)$
and $J/ψ$ mesons: The relative rates of B-meson decays into $J/\psi$ and $\psi(2S)$ mesons are
measured for the three decay modes in pp collisions recorded with the LHCb
detector. The ratios of branching fractions ($\mathcal{B}$) are measured to be
$\frac{\mathcal{B}(B^+ \to \psi(2S) K^+)}{\mathcal{B}(B^+ \to J/\psi K^+)} =
0.594 \pm 0.006 (stat) \pm 0.016 (syst) \pm 0.015 (R_{\psi})$,
$\frac{\mathcal{B}(B^0 \to \psi(2S) K^{*0})}{\mathcal{B}(B^0 \to J/\psi
K^{*0})} = 0.476 \pm 0.014 (stat) \pm 0.010 (syst) \pm 0.012\,(R_{\psi})$,
$\frac{\mathcal{B}^{0}_{s}(B^0_s \to \psi(2S)\phi)}{\mathcal{B}(B^0_s \to
J/\psi\phi)} = 0.489 \pm 0.026 (stat) \pm 0.021 (syst) \pm 0.012\,(R_{\psi})$
where the third uncertainty is from the ratio of the $\psi(2S)$ and $J/\psi$
branching fractions to $\mu\mu$. | hep-ex |
Real and virtual photon structure from dijet events: Jet production in $ep$ collisions is sensitive to the partonic structure of
photon. The latest measurements of dijet production from the H1 experiment
provide new results of the gluon density of real photons at low $x$ and, for
the first time, on the partonic density of virtual photons. Properties of the
photon remnant were measured as a function of the hard scale defined by the
$p_T$ of the jets. The comparison of dijet cross sections with the NLO QCD
calculation shows the non-triviality of the concept of virtual photon
structure. | hep-ex |
Top quark mass measurements with the CMS experiment at the LHC: Measurements of the top quark mass are presented, obtained from CMS data
collected in proton proton collisions at the LHC at centre-of-mass energies of
7 TeV and 8 TeV. The mass of the top quark is measured using several methods
and channels, including the reconstructed invariant mass distribution of the
top quark as well as measurements based on charged particle information. The
dependence of the mass measurement on the kinematic phase space is
investigated. The results of the various channels are combined and compared to
the world average. The top mass is extracted from the inclusive top quark pair
production cross section measured at CMS. | hep-ex |
Observation of $ψ(3686) \to p \bar{p} η^{\prime}$ and improved
measurement of $J/ψ\to p \bar{p} η^{\prime}$: We observe the process $\psi(3686) \to p \bar{p} \eta^{\prime}$ for the first
time, with a statistical significance higher than 10$\sigma$, and measure the
branching fraction of $J/\psi \to p \bar{p} \eta^{\prime}$ with an improved
accuracy compared to earlier studies. The measurements are based on $4.48
\times 10^8$ $\psi(3686)$ and $1.31 \times 10^{9}$ $J/\psi$ events collected by
the BESIII detector operating at the BEPCII. The branching fractions are
determined to be $B(\psi(3686) \to p \bar{p} \eta^{\prime}) =
(1.10\pm0.10\pm0.08)\times10^{-5}$ and $B(J/\psi \to p \bar{p}
\eta^{\prime})=(1.26\pm0.02\pm 0.07)\times10^{-4}$, where the first
uncertainties are statistical and the second ones systematic. Additionally, the
$\eta-\eta^{\prime}$ mixing angle is determined to be $-24^{\circ} \pm
11^{\circ}$ based on $\psi(3686) \to p \bar{p} \eta^{\prime}$, and $-24^{\circ}
\pm 9^{\circ}$ based on $J/\psi \to p \bar{p} \eta^{\prime}$, respectively. | hep-ex |
Measurements of the branching fraction, isospin asymmetry, and
lepton-universality ratio in $B \to J/ψK$ decays at Belle II: We report a study of $B \to J/\psi(\ell^{+}\ell^{-})K$ decays, where $\ell$
represents an electron or a muon, using $e^{+}e^{-}$ collisions at the
$\Upsilon(4S)$ resonance. The data were collected by the Belle II experiment at
the SuperKEKB asymmetric-energy collider during 2019-2021, corresponding to an
integrated luminosity of $189$ fb$^{-1}$. The measured quantities are the
branching fractions (${\mathcal B}$) of the decay channels $B^{+} \to
J/\psi(e^{+}e^{-})K^{+}$, $B^{+} \to J/\psi(\mu^{+}\mu^{-}) K^{+}$, $B^{0} \to
J/\psi(e^{+}e^{-}) K^{0}_{S}$, and $B^{0} \to J/\psi(\mu^{+}\mu^{-})K^{0}_{S}$;
the lepton-flavor-dependent isospin asymmetries for the electron [$A_{I}\left(B
\to J/\psi(e^{+}e^{-}) K\right)$] and muon [$A_{I}\left(B \to J/\psi(\mu^{+}
\mu^{-}) K\right)$] channels; and the ratios of branching fractions between the
muon and electron channels for the charged [$R_{K^{+}}\left(J/\psi\right)$] and
neutral kaon [$R_{K^{0}}\left(J/\psi\right)$] case. The measurements are
consistent with the world-average values. | hep-ex |
Measurement of the W+W-gamma Cross Section and Direct Limits on
Anomalous Quartic Gauge Boson Couplings at LEP: The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2. | hep-ex |
Search for supersymmetry in multijet events with missing transverse
momentum in proton-proton collisions at 13 TeV: A search for supersymmetry is presented based on multijet events with large
missing transverse momentum produced in proton-proton collisions at a
center-of-mass energy of sqrt(s) = 13 TeV. The data, corresponding to an
integrated luminosity of 35.9 inverse femtobarns, were collected with the CMS
detector at the CERN LHC in 2016. The analysis utilizes four-dimensional
exclusive search regions defined in terms of the number of jets, the number of
tagged bottom quark jets, the scalar sum of jet transverse momenta, and the
magnitude of the vector sum of jet transverse momenta. No evidence for a
significant excess of events is observed relative to the expectation from the
standard model. Limits on the cross sections for the pair production of gluinos
and squarks are derived in the context of simplified models. Assuming the
lightest supersymmetric particle to be a weakly interacting neutralino, 95%
confidence level lower limits on the gluino mass as large as 1800 to 1960 GeV
are derived, and on the squark mass as large as 960 to 1390 GeV, depending on
the production and decay scenario. | hep-ex |
Study of the Y (4260) resonance in e+e- collisions with initial state
radiation at Belle: We present a study of Y(4260) properties using the initial-state radiation
process e^+e^- -> gamma_{ISR} Y(4260). The Y(4260) resonance is reconstructed
in the pi^+ pi^- J/\psi decay mode, using data collected by the Belle detector
at the KEKB e^+e^- collider. We find a significant signal with a central mass
value of (4295 +-10 +10 -3) MeV/c^2 and a width of (133 +-26 +13 -6) MeV/c^2.
We find Gamma_{ee}.B(Y(4260) -> pi^+ pi^- J/\psi) = (8.7 +- 1.1 +0.3 -0.9) eV.
These results are preliminary. | hep-ex |
Search for $B^+ \to e^+ ν$ and $B^+ \to μ^+ ν$ decays using
hadronic tagging: We present a search for the rare leptonic decays $B^+ \to e^+ \nu_e$ and $B^+
\to \mu^+ \nu_\mu$, using the full $\Upsilon(4S)$ data sample of $772\times
10^6$ $B\bar{B}$ pairs collected with the Belle detector at the
$\small\textbf{KEKB}$ asymmetric-energy $e^+ e^-$ collider. One of the $B$
mesons from the $\Upsilon(4S) \to B\bar{B}$ decay is fully reconstructed in a
hadronic mode, while the recoiling side is analyzed for the signal decay. We
find no evidence of a signal in any of the decay modes. Upper limits of the
corresponding branching fractions are determined as ${\cal B}(B^+ \to e^+
\nu_e)<3.5\times 10^{-6}$ and ${\cal B}(B^+ \to \mu^+ \nu_\mu)<2.7 \times
10^{-6}$ at 90$\%$ confidence level. | hep-ex |
Rare decays at the LHCb experiment: Rare decays of beauty and charm hadrons offer a rich playground to make
precise tests of the Standard Model and look for New Physics at the level of
quantum corrections. A review of recent LHCb results will be presented. | hep-ex |
Measurement of the Drell--Yan triple-differential cross section in $pp$
collisions at $\sqrt{s} = 8$ TeV: This paper presents a measurement of the triple-differential cross section
for the Drell--Yan process $Z/\gamma^*\rightarrow \ell^+\ell^-$ where $\ell$ is
an electron or a muon. The measurement is performed for invariant masses of the
lepton pairs, $m_{\ell\ell}$, between $46$ and $200$ GeV using a sample of
$20.2$ fb$^{-1}$ of $pp$ collisions data at a centre-of-mass energy of
$\sqrt{s}=8$ TeV collected by the ATLAS detector at the LHC in 2012. The data
are presented in bins of invariant mass, absolute dilepton rapidity,
$|y_{\ell\ell}|$, and the angular variable $\cos\theta^{*}$ between the
outgoing lepton and the incoming quark in the Collins--Soper frame. The
measurements are performed in the range $|y_{\ell\ell}|<2.4$ in the muon
channel, and extended to $|y_{\ell\ell}|<3.6$ in the electron channel. The
cross sections are used to determine the $Z$ boson forward-backward asymmetry
as a function of $|y_{\ell\ell}|$ and $m_{\ell\ell}$. The measurements achieve
high-precision, below the percent level in the pole region, excluding the
uncertainty in the integrated luminosity, and are in agreement with
predictions. These precision data are sensitive to the parton distribution
functions and the effective weak mixing angle. | hep-ex |
Recent charmonium results from BABAR: Recent results in the field of spectroscopy from the BABAR experiment are
reported, with particular attention to the new states observed in ISR and
$\gamma \gamma$ interactions using the full BABAR data sample. We confirm the
states Y(4260) and Y(4360) with higher precision and for the first time the
state Y(4660) is observed. We do not confirm the Y(4008) state reported by
Belle. In addition, the analysis of the invariant mass of the $J/\psi \omega$
system produced in $\gamma \gamma$ interactions is presented in confirmation of
the Belle observation of the X(3915) in this process. | hep-ex |
New H1 results on isolated leptons and missing pt at HERA: The search for events containing isolated leptons (electrons or muons) and
missing transverse momentum produced in $e^{\pm}p$ collisions is performed with
the H1 detector at HERA in the period 1994--2005. The analysed data sample
corresponds to an integrated luminosity of 279 pb$^{-1}$, which includes 53
pb$^{-1}$ of $e^{+}p$ data and 107 pb$^{-1}$ of $e^{-}p$ data from the new
HERA~II phase. A total of 40 events are observed in the data, compared to a
Standard Model (SM) prediction of 34.3 $\pm$ 4.8. At large hadronic transverse
momentum $P_{T}^{X} >$ 25 GeV, a total of 17 events are observed compared to
9.0 $\pm$ 1.5 predicted by the SM. In this region, 15 events are observed in
the $e^{+}p$ data compared to a SM prediction of 4.6 $\pm$ 0.8, whereas in the
$e^{-}p$ data 2 events are observed compared to a SM prediction of 4.4 $\pm$
0.7. | hep-ex |
Measurement of the absolute branching ratios for semileptonic K+/-
decays with the KLOE detector: Using a sample of over 600 million phi->K+K- decays collected at the Dafne
e+e- collider, we have measured with the KLOE detector the absolute branching
ratios for the charged kaon semileptonic decays, K+/- -> p0 e nu (gamma) (Ke3)
and K+/- -> p0 mu nu (gamma) (Kmu3). The results, BR(Ke3) = 0.04965 +/-
0.00038_{stat} +/- 0.00037_{syst} and BR(Kmu3) = 0.03233 +/- 0.00029_{stat} +/-
0.00026_{syst}, are inclusive of radiation. Accounting for correlations, we
derive the ratio Kmu3/Ke3 = 0.6511+/-0.0064. Using the semileptonic form
factors measured in the same experiment, we obtain V_{us}f_{+}(0) = 0.2141 +/-
0.0013. | hep-ex |
Hadronization in Nuclei - Multidimensional Study: Hadron multiplicities in semi-inclusive deep-inelastic scattering were
measured on neon, krypton and xenon targets relative to deuterium at an
electron-beam energy of 27.6 GeV at HERMES. These ratios were determined as a
function of the virtual-photon energy nu, its virtuality Q2, the fractional
hadron energy z and the transverse hadron momentum with respect to the
virtual-photon direction p_t . Dependences were analysed separately for
positively and negatively charged pions and kaons as well as protons and
antiprotons in a two-dimensional representation. These results will help to
constrain mechanisms and models of hadronization much more decisively than by
the use of integrated results as traditionally done. A few features particular
to the two-dimensional representation are highlighted in this contribution. | hep-ex |
Super-ORCA: Measuring the leptonic CP-phase with Atmospheric Neutrinos
and Beam Neutrinos: Studying the atmospheric neutrino oscillation probabilities below 2 GeV with
a multi-megaton Cherenkov detector allows for a measurement of the leptonic
CP-phase $\delta_{CP}$. The most relevant CP-sensitive energy range is below
the neutrino detection threshold of KM3NeT/ORCA, which is an underwater
Cherenkov detector optimised to determine the neutrino mass ordering by
measuring the oscillation pattern of 3-30 GeV atmospheric neutrinos. With
Super-ORCA, a $\sim 10$ times more-densely instrumented version of ORCA, the
detection threshold can be lowered and the event reconstruction capabilities
improved.
In this paper, the key detector performance indicators for a possible
Super-ORCA detector and the sensitivity to $\delta_{CP}$ with atmospheric
neutrinos are presented. Including systematics, a 1$\sigma$-resolution on
$\delta_{CP}$ of about $38^\circ$ ($23^\circ$) is achieved for $\delta_{CP}=0$
($\delta_{CP}=\pi/2$) after 10 years. In addition, the potential of using a
neutrino beam from the Protvino accelerator facility to the Super-ORCA detector
is discussed. With this, a 1$\sigma$-resolution on $\delta_{CP}$ of about
$10^\circ$ ($16^\circ$) is achieved for $\delta_{CP}=0$ ($\delta_{CP}=\pi/2$)
after 10 years. | hep-ex |
Observation of narrow baryon resonance in $pK^0_s$ mode in
$pA$-interactions at $70 GeV/c$ with SVD-2 setup: We report on the SVD-2 experiment data analysis aimed to search for an exotic
baryon state, the $\Theta^+$-baryon, in a $pK^0_s$ decay mode with IHEP U-70
accelerator proton beam at $70 GeV/c$. A resonant structure with
$M=1526\pm3(stat.)\pm 3(syst.)~MeV/c^2$ and $\Gamma < 24 MeV/c^2$ was found in
the $pK^0_s$ invariant mass spectrum, with the statistical significance of this
peak estimated as $5.6~\sigma$. | hep-ex |
W and Z production in the forward region at LHCb: Measurements of electroweak boson production in pp collisions at $\sqrt{s} =
7$ TeV are presented using the decays $W \rightarrow \mu\nu$, $Z \rightarrow
\mu\mu$ and $Z \rightarrow \tau\tau$ recorded using the LHCb detector at the
LHC. For muonic $W$ and $Z$ decays, the data sample corresponds to an
integrated luminosity of 37.1 $\pm$ 1.3 pb$^{-1}$. Here the $W$ and $Z$ bosons
are reconstructed from muons with transverse momenta, $p_{T}$, above 20 GeV and
pseudorapidity, $\eta$, between 2 and 4.5, and, in the case of the $Z$, a
dimuon invariant mass $M_{Z}$ between 60 GeV and 120 GeV. For $Z$ decays to tau
lepton final states, 247 pb$^{-1}$ of data has been used. Here one tau is
identified through its decay to a muon and neutrinos; the other through its
decay to an electron or muon and neutrinos. The cross-sections are measured to
be: $\sigma(W^{+}\rightarrow\mu^{+}\nu) = $ 808 $\pm$ 7 $\pm$ 28 $\pm$ 28 pb;
$\sigma(W^{+}\rightarrow\mu^{+}\nu) = $ 634 $\pm$ 7 $\pm$ 21 $\pm$ 22 pb;
$\sigma(Z\rightarrow\mu\mu) = $ 74.9 $\pm$ 1.6 $\pm$ 3.8 $\pm$ 2.6 pb;
$\sigma(Z\rightarrow\tau\tau) = $ 82 $\pm$ 8 $\pm$ 7 $\pm$ 4 pb. Here the first
error is statistical, the second is systematic and the third is due to the
luminosity determination. For muonic final states, differential measurements,
cross-section ratios and the $W$ charge asymmetry are also measured in the same
kinematic region. The ratio of the $Z\rightarrow\tau\tau$ and
$Z\rightarrow\mu\mu$ cross-sections has been measured to be 1.09 $\pm$ 0.17,
consistent with lepton universality. Theoretical predictions, calculated at
next-to-next-to-leading order (NNLO) in QCD using recent parton distribution
functions, are found to be in agreement with the measurements. | hep-ex |
Diffractive Deep-Inelastic Scattering: New results on diffractive deep-inelastic $e p$ scattering at HERA are
presented using data taken in 1994 with the H1 detector. The cross section for
diffractive deep-inelastic scattering is measured in terms of a diffractive
structure function $F_2^{D(3)}(\beta,Q^2,\xpom)$ over an extended kinematic
range. The dependence of $F_2^{D(3)}$ on $\xpom$ is found not to depend on
$Q^2$, but to depend on $\beta$. Therefore the $\xpom$ dependence no longer
factorizes. The $Q^2$ and $\beta$ dependence of $F_2^{D(3)}$ is analyzed after
an integration over the dependence on $\xpom$. For fixed $\beta$ a clear rise
with $\log Q^2$ is observed, persisting up to high values of $\beta$. In terms
of the Altarelli-Parisi (DGLAP) QCD evolution equations, these scaling
violations give clear indications for a gluon dominated process. Subsequently
an attempt is made to quantify the parton content of the diffractive exchange
using the DGLAP evolution. At the starting scale a ``leading'' gluon
distribution is found which contributes about $80 \%$ of the momentum in the
diffractive exchange. Measurements of the hadronic final state (energy flow and
production of $D^{*}$ mesons) are found to be consistent with the predictions
of a model of deep-inelastic electron pomeron scattering using the information
on the parton content obtained. | hep-ex |
Observation of excited $Ω_c^0$ baryons in $Ω_b^- \to Ξ_c^+
K^-π^-$ decays: The first observation of the $\Omega_b^- \to \Xi_c^+ K^- \pi^-$ decay is
reported using $pp$ collision data at centre-of-mass energies of 7, 8 and
13\,$\mathrm{TeV}$ collected by the LHCb experiment, corresponding to an
integrated luminosity of 9\,$\mathrm{fb}^{-1}$. Four excited $\Omega_c^0$
baryons are observed in the $\Xi_c^+ K^-$ mass projection of the $\Omega_b^-
\to \Xi_c^+ K^- \pi^-$ decays with the significance of each exceeding five
standard deviations. They coincide with the states previously observed in
prompt \proton\proton and $e^+e^-$ production. Relative production rates,
masses and natural widths of the states are measured, and a test of spin
hypotheses is performed. Moreover, the branching ratio of $\Omega_b^- \to
\Xi_c^+ K^- \pi^-$ is measured relative to the $\Omega_b^- \to \Omega_c^0
\pi^-$ decay mode and a precise measurement of the $\Omega_b^-$ mass of
\mbox{$6044.3 \pm 1.2 \pm 1.1^{\,+0.19}_{\,-0.22}\,\mathrm{MeV}$} is obtained. | hep-ex |
Observation of new resonances decaying to $Dπ$ and $D^*π$ in
inclusive $e^+e^-$ collisions near $\sqrt{s}=$10.58 GeV: We present a study of the $D^+\pi^-$, $D^0\pi^+$, and $D^{*+}\pi^-$ systems
in inclusive $e^+e^- \rightarrow c\bar{c}$ interactions in a search for new
excited $D$ meson states. We use a dataset, consisting of $\sim$454 fb$^{-1}$,
collected at center-of-mass energies near 10.58 GeV by the BABAR detector at
the SLAC PEP-II asymmetric-energy collider. We observe, for the first time,
candidates for the radial excitations of the $D^0$, $D^{*0}$, and $D^{*+}$, as
well as the L=2 excited states of the $D^0$ and $D^+$, where $L$ is the orbital
angular momentum of the quarks. | hep-ex |
New Tagging Method of B Flavor of Neutral B Meson in CP Violation
Measurement in Asymmetric B-Factory Experiment: In CP violation measurements in asymmetric B-factory experiments, a
determination of the B flavor of the neutral B mesons is necessary. A new
method to this purpose using only three vectors of charged particles has been
developed. This method (weighted charge method) does not require either lepton
identification or charged-kaon identification. The tagging efficiency,
probability for incorrect tagging, and effective tagging efficiency of this
method are 43.1, 18.3, and 17.3\%, respectively. | hep-ex |
MACRO and the atmospheric neutrino problem: After a brief presentation of the MACRO detector we discuss the updated data
on atmospheric muon neutrinos, and the interpretation in terms of neutrino
oscillations. | hep-ex |
Search for resonances decaying to a pair of Higgs bosons in the
$\mathrm{b\overline{b}q\overline{q}'}\ellν$ final state in proton-proton
collisions at $\sqrt{s} =$ 13 TeV: A search for new massive particles decaying into a pair of Higgs bosons in
proton-proton collisions at a center-of-mass energy of 13 TeV is presented.
Data were collected with the CMS detector at the LHC, corresponding to an
integrated luminosity of 35.9 fb$^{-1}$. The search is performed for resonances
with a mass between 0.8 and 3.5 TeV using events in which one Higgs boson
decays into a bottom quark pair and the other decays into two W bosons that
subsequently decay into a lepton, a neutrino, and a quark pair. The Higgs boson
decays are reconstructed with techniques that identify final state quarks as
substructure within boosted jets. The data are consistent with standard model
expectations. Exclusion limits are placed on the product of the cross section
and branching fraction for generic spin-0 and spin-2 massive resonances. The
results are interpreted in the context of radion and bulk graviton production
in models with a warped extra spatial dimension. These are the best results to
date from searches for an HH resonance decaying to this final state, and they
are comparable to the results from searches in other channels for resonances
with masses below 1.5 TeV. | hep-ex |
A conceptual design of TOF based on MRPC technology for the future
electron-positron Higgs factory: Future electron-positron Higgs factories could provide excellent
opportunities to examine the Standard Model and search for new physics with
much higher precision than the LHC. A precise particle identification is
crucial for the physics program at these future colliders and can be achieved
via precise time-of-flight (TOF) measurements of the final state particles. In
this paper, we propose a conceptual design of TOF system based on the multigap
resistive plate chamber (MRPC) technology for future electron-positron Higgs
factories. This TOF system has a time resolution of < 35 ps, a total active
area of 77m2, and a construction budget of the order of 5 million USD.
Keywords: MRPC, TOF, PID, CEPC | hep-ex |
Search for new phenomena with large jet multiplicities and missing
transverse momentum using large-radius jets and flavour-tagging at ATLAS in
13 TeV $pp$ collisions: A search is presented for particles that decay producing a large jet
multiplicity and invisible particles. The event selection applies a veto on the
presence of isolated electrons or muons and additional requirements on the
number of b-tagged jets and the scalar sum of masses of large-radius jets.
Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton
collisions at $\sqrt{s}=13~\mathrm{TeV}$, which corresponds to 36.1 fb$^{-1}$
of integrated luminosity, no evidence is found for physics beyond the Standard
Model. The results are interpreted in the context of simplified models inspired
by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are
pair-produced. More generic models within the phenomenological minimal
supersymmetric Standard Model are also considered. | hep-ex |
New Phenomena II: Recent Results from the Fermilab Tevatron: The CDF and D\O collaborations continue to search for new physics using more
than 100~pb$^{-1}$ of \xxbar{p} collisions at $\sqrt{s}=1.8$ TeV collected at
the Fermilab Tevatron. We present recent results from both experiments on
R-parity violating Supersymmetry and $Z'$/Technicolor production with $ee$ and
\xxbar{t} final states. In addition we introduce Sherlock, a new
quasi-model-independent search strategy. | hep-ex |
Search for the Decay J/psi -> gamma + invisible: A search for J/psi radiative decay to weakly interacting neutral final states
was performed using the CLEO-c detector at CESR. A total of 3.7 x 10^{6} tagged
J/psi events was collected at the psi(2S) resonance and used to study the decay
J/psi -> gamma+X, where X is a narrow state that is invisible to the detector.
No significant signal was observed and upper limits on the branching fraction
were set for masses m_X up to 960 MeV/c^2. The upper limit corresponding to
m_X=0 is 4.3x 10^{-6} at the 90% confidence level. | hep-ex |
Observation of the rare decay B+->K+pi0pi0 and measurement of the
quasi-two body contributions B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+: We report an analysis of the charmless hadronic decays of charged B meson to
the final state K+pi0pi0, using a data sample of 470+/-2.8 million BBbar events
collected at the Y(4S) resonance. We observe an excess of signal events, with a
significance above 10 standard deviations including systematic uncertainties,
and measure the branching fraction and CP asymmetry to be
B(B+->K+pi0pi0)=(16.2+/-1.2+/-1.5)x10^-6 and
A_CP(B+->K+pi0pi0)=-0.06+/-0.06+/-0.04, where the uncertainties are statistical
and systematic respectively. Additionally we study the contributions of the
B+->K*(892)+pi0, B+->f0(980)K+ and B+->chic0K+ quasi-two body decays. We report
the world's best measurements of the branching fractions and CP asymmetry of
the B+->K+pi0pi0 and B+->K*(892)+pi0 channels. | hep-ex |
Spin Structure Functions g_1 and g_2 for the Proton and Deuteron: The experiment E155 at SLAC measured the spin structure functions g_1 and g_2
of the proton and deuteron. The experiment used deep inelastic scattering of
48.3 GeV longitudinally polarized electrons incident on polarized solid
^{15}NH_3 and ^{6}LiD targets. The data taken by three independent
spectrometers covered a kinematic range of 0.014 < x < 0.9 and 1 (GeV/c)^2 <
Q^2 < 40 (GeV/c)^2. Due to the high luminosity and polarization available at
SLAC the data on g_1 are to date the most precise in this kinematic range. The
x and Q^2 dependence of g_1 has been studied using NLO PQCD fits, allowing
extraction of values for the Bjorken sum rule and quark and gluon spin
contributions to the nucleon. Results are presented for g_1 and g_2 for the
proton and deuteron. | hep-ex |
Search for dark matter in events with a leptoquark and missing
transverse momentum in proton-proton collisions at 13 TeV: A search is presented for dark matter in proton-proton collisions at a
center-of-mass energy of $\sqrt{s} =$ 13 TeV using events with at least one
high transverse momentum ($p_\mathrm{T}$) muon, at least one
high-$p_\mathrm{T}$ jet, and large missing transverse momentum. The data were
collected with the CMS detector at the CERN LHC in 2016 and 2017, and
correspond to an integrated luminosity of 77.4 fb$^{-1}$. In the examined
scenario, a pair of scalar leptoquarks is assumed to be produced. One
leptoquark decays to a muon and a jet while the other decays to dark matter and
low-$p_\mathrm{T}$ standard model particles. The signature for signal events
would be significant missing transverse momentum from the dark matter in
conjunction with a peak at the leptoquark mass in the invariant mass
distribution of the highest $p_\mathrm{T}$ muon and jet. The data are observed
to be consistent with the background predicted by the standard model. For the
first benchmark scenario considered, dark matter masses up to 500 GeV are
excluded for leptoquark masses $M_\mathrm{LQ}$ $\approx$ 1400 GeV, and up to
300 GeV for $M_\mathrm{LQ}$ $\approx$ 1500 GeV. For the second benchmark
scenario, dark matter masses up to 600 GeV are excluded for $M_\mathrm{LQ}$
$\approx$ 1400 GeV. | hep-ex |
Measurement of Branching Fractions for $B\to χ_{c1(2)} K (K^*)$ at
Belle: We have measured the branching fractions for the exclusive decay modes $B\to
{\chi}_{c1(2)} K(K^*)$ using a $140~{\rm fb}^{-1}$ data sample collected by the
Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The measured
branching fractions for $B^+\to {\chi}_{c1}K^+$, $B^0\to {\chi}_{c1}K^0$,
$B^0\to {\chi}_{c1}K^{*0}$ and $B^+\to {\chi}_{c1}K^{*+}$ decay modes are
$(4.5\pm 0.2\pm0.5)\times 10^{-4}$, $(3.5\pm 0.3\pm0.5)\times 10^{-4}$,
$(3.1\pm 0.3\pm0.7)\times 10^{-4}$ and $(4.1\pm 0.6\pm0.9)\times 10^{-4}$,
respectively, where the first error is statistical and the second error is
systematic. We do not observe statistically significant signals for the $B\to
{\chi}_{c2}K(K^*)$ decay modes and set upper limits at the 90% confidence
level. We also study the helicity distribution for $B\to {\chi}_{c1} K^*$ decay
mode and show that the longitudinal polarization component is dominant. {{\it
Keywords:} {$B$-meson, Charmonium, Branching Fractions, Polarization}} {{\it
PACS:} 13.25.Hw, 11.30.Er} | hep-ex |
Search for weakly interacting sub-eV particles with the OSQAR
laser-based experiment: results and perspectives: Recent theoretical and experimental studies highlight the possibility of new
fundamental particle physics beyond the Standard Model that can be probed by
sub-eV energy experiments. The OSQAR photon regeneration experiment looks for
"Light Shining through a Wall" (LSW) from the quantum oscillation of optical
photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or
axion-like particles (ALPs), in a 9 T transverse magnetic field over the
unprecedented length of $2 \times 14.3$ m. No excess of events has been
detected over the background. The di-photon couplings of possible new light
scalar and pseudo-scalar particles can be constrained in the massless limit to
be less than $8.0\times10^{-8}$ GeV$^{-1}$. These results are very close to the
most stringent laboratory constraints obtained for the coupling of ALPs to two
photons. Plans for further improving the sensitivity of the OSQAR experiment
are presented. | hep-ex |
Results from the first heavy ion run at the LHC: Early November 2010, the LHC collided for the first time heavy ions, Pb on
Pb, at a centre-of-mass energy of 2.76 TeV/nucleon. This date marked both the
end of almost 20 years of preparing for nuclear collisions at the LHC, as well
as the start of a new era in ultra-relativistic heavy ion physics at energies
exceeding previous machines by more than an order of magnitude. This
contribution summarizes some of the early results from all three experiments
participating in the LHC heavy ion program (ALICE, ATLAS, and CMS), which show
that the high density matter created at the LHC, while much hotter and larger,
still behaves like the very strongly interacting, almost perfect liquid
discovered at RHIC. Some surprising and even puzzling results are seen in
particle ratios, jet-quenching, and Quarkonia suppression observables. The
overall experimental conditions at the LHC, together with its set of powerful
and state-of-the-art detectors, should allow for precision measurements of
quark-gluon-plasma parameters like viscosity and opacity. | hep-ex |
Measurement of the Branching Fractions for Inclusive $B^-$ and $\bar
B^0$ Decays to Flavor-tagged $D$, $D_s$ and $Λ_c$: We report on the inclusive branching fractions of $B^-$ and of ${\bar B}^0$
mesons decaying to ${D^0 X}$, ${{\bar D}^0 X}$, ${D^+ X}$, ${D^- X}$, ${D_s^+
X}$, ${D_s^- X}$, ${\Lambda_c^+ X}$, ${{\bar \Lambda}_c^- X}$, based on a
sample of 88.9 million $B \bar B$ events recorded with the $BABAR$ detector at
the $\Upsilon(4S)$ resonance. Events are selected by completely reconstructing
one $B$ and searching for a reconstructed charmed particle in the rest of the
event. We measure the number of charmed and of anti-charmed particles per $B$
decay and derive the total charm yield per $B^-$ decay, $n_c^- = 1.313 \pm
0.037 \pm 0.062 ^{+0.063}_{-0.042} $, and per ${\bar B}^0$ decay, $n_c^0 =
1.276 \pm 0.062 \pm 0.058 ^{+0.066}_{-0.046}$ where the first uncertainty is
statistical, the second is systematic, and the third reflects the charm
branching-fraction uncertainties. | hep-ex |
Analysis of Neutral Current Interactions in MINOS: A Search for Sterile
Neutrinos: A search for disappearance of active neutrinos over a baseline of 735 km was
conducted using the NuMI neutrino beam and the MINOS detectors. The data
analyzed correspond to an exposure of 3.18x10^{20} protons on target. The data
are fitted to neutrino oscillation models in which mixing with one sterile
neutrino is assumed. A comparison of the neutral-current-like spectrum at the
FD with the expectation derived from the near detector measurement shows that
the fraction of disappearing muon neutrinos converting to a sterile state is
less than 52% at the 90% confidence level. In addition, the possibility of
decay of active neutrinos into sterile species occurring concurrently with
neutrino oscillations was analyzed. Pure neutrino decay is disfavored at 5.4
sigma as an alternate explanation to oscillations for the depletion of muon
neutrinos at 735 km. The methodology employed in the analysis of neutral
current neutrino events observed in MINOS is described and newly obtained
results are presented. | hep-ex |
Search for Dimuon Decays of a Light Scalar Boson in Radiative
Transitions Upsilon -> gamma A0: We search for evidence of a light scalar boson in the radiative decays of the
Upsilon(2S) and Upsilon(3S) resonances: Upsilon(2S,3S)-> gamma A0, A0 -> mu^+
mu^-. Such a particle appears in extensions of the Standard Model, where a
light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no
evidence for such processes in the mass range 0.212<= m(A0)<= 9.3 GeV in the
samples of 99*10^6 Upsilon(2S) and 122*10^6 Upsilon(3S) decays collected by the
BABAR detector at the PEP-II B-factory and set stringent upper limits on the
effective coupling of the b quark to the A0. We also limit the dimuon branching
fraction of the eta_b meson: BR(eta_b->mu^+mu^-)<0.9% at 90% confidence level. | hep-ex |
Status and Perspectives of Neutrino Physics: I will first give a brief but comprehensive review of the status of our
knowledge in neutrino physics. With reference to a not too far future I will
then discuss the perspectives that appear to me to be most important and
promising. | 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.