65 research outputs found
Measurement of jet production in deep inelastic scattering and NNLO determination of the strong coupling at ZEUS
A new measurement of inclusive-jet cross sections in the Breit frame in
neutral current deep inelastic scattering using the ZEUS detector at the HERA
collider is presented. The data were taken in the years 2004 to 2007 at a
centre-of-mass energy of and correspond to an integrated
luminosity of . Massless jets, reconstructed using the
-algorithm in the Breit reference frame, have been measured as a function
of the squared momentum transfer, , and the transverse momentum of the
jets in the Breit frame, . The measured jet cross
sections are compared to previous measurements and to perturbative QCD
predictions. The measurement has been used in a next-to-next-to-leading-order
QCD analysis to perform a simultaneous determination of parton distribution
functions of the proton and the strong coupling, resulting in a value of
, whose accuracy is improved compared to
similar measurements. In addition, the running of the strong coupling is
demonstrated using data obtained at different scales.Comment: 42 pages, 10 figues, to be submitted to Eur. Phys. J.
Measurement of the cross-section ratio in exclusive photoproduction at HERA
The exclusive photoproduction reactions and
have been measured at an centre-of-mass energy
of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373
pb. The measurement was made in the kinematic range GeV,
GeV and GeV, where is the photon--proton
centre-of-mass energy, is the photon virtuality and is the squared
four-momentum transfer at the proton vertex. The decay channels used were
, and with subsequent decay . The
ratio of the production cross sections, , has been measured as a function of and and
compared to previous data in photoproduction and deep inelastic scattering and
with predictions of QCD-inspired models of exclusive vector-meson production,
which are in reasonable agreement with the data.Comment: 31 pages, 9 figures. Updated according to comments from journal
referee including a new table. Added full collaboration author lis
Search for effective Lorentz and CPT violation using ZEUS data
Lorentz and CPT symmetry in the quark sector of the Standard Model are
studied in the context of an effective field theory using ZEUS
data. Symmetry-violating effects can lead to time-dependent oscillations of
otherwise time-independent observables, including scattering cross sections. An
analysis using five years of inclusive neutral-current deep inelastic
scattering events corresponding to an integrated HERA luminosity of at Gev has been performed. No evidence for
oscillations in sidereal time has been observed within statistical and
systematic uncertainties. Constraints, most for the first time, are placed on
42 coefficients parameterising dominant CPT-even dimension-four and CPT-odd
dimension-five spin-independent modifications to the propagation and
interaction of light quarks.Comment: 36 pages, 12 figures. Additional material included as an ancillary
file for this arXiv entr
Search for effective Lorentz and CPT violation using ZEUS data
Lorentz and CPT symmetry in the quark sector of the Standard Model are studied in the context of an effective field theory using ZEUS e±p data. Symmetry-violating effects can lead to time-dependent oscillations of otherwise time-independent observables, including scattering cross sections. An analysis using five years of inclusive neutral-current deep inelastic scattering events corresponding to an integrated HERA luminosity of 372 pb-1 at s=318 GeV has been performed. No evidence for oscillations in sidereal time has been observed within statistical and systematic uncertainties. Constraints, most for the first time, are placed on 42 coefficients parametrizing dominant CPT-even dimension-four and CPT-odd dimension-five spin-independent modifications to the propagation and interaction of light quarks
K meson production in inelastic p+p interactions at 158 GeV/c beam momentum measured by NA61/SHINE at the CERN SPS
The production of K mesons in inelastic p+p collisions at beam momentum 158 GeV / (=17.3 GeV ) was measured with the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicity of K was determined to be 0.162±0.001(.)±0.011(.). The results on K production are compared with model predictions (EPOS 1.99, SMASH 2.0, PHSD and UrQMD 3.4 models) as well as with published world data
Spectra and mean multiplicities of π- in central 40 Ar+ 45 Sc collisions at 13A, 19A, 30A, 40A, 75A and 150 AGeV/c beam momenta measured by the NA61/SHINE spectrometer at the CERN SPS: NA61/SHINE Collaboration
The physics goal of the strong interaction program of the NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) is to study the phase diagram of hadronic matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents differential inclusive spectra of transverse momentum, transverse mass and rapidity of π mesons produced in central Ar45Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A Ge V /c. Energy and system size dependence of parameters of these distributions – mean transverse mass, the inverse slope parameter of transverse mass spectra, width of the rapidity distribution and mean multiplicity – are presented and discussed. Furthermore, the dependence of the ratio of the mean number of produced pions to the mean number of wounded nucleons on the collision energy was derived. The results are compared to predictions of several models
Spectra and mean multiplicities of in central collisions at 13A, 19A, 30A, 40A, 75A and 150A Ge V/c beam momenta measured by the NA61/SHINE spectrometer at the CERN SPS
International audienceThe physics goal of the strong interaction program of the NA61/SHINE experiment at the CERN Super Proton Synchrotron (SPS) is to study the phase diagram of hadronic matter by a scan of particle production in collisions of nuclei with various sizes at a set of energies covering the SPS energy range. This paper presents differential inclusive spectra of transverse momentum, transverse mass and rapidity of mesons produced in centralAr+Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150. Energy and system size dependence of parameters of these distributions – mean transverse mass, the inverse slope parameter of transverse mass spectra, width of the rapidity distribution and mean multiplicity – are presented and discussed. Furthermore, the dependence of the ratio of the mean number of produced pions to the mean number of wounded nucleons on the collision energy was derived. The results are compared to predictions of several models
Measurements of multiplicity fluctuations of identified hadrons in inelastic proton–proton interactions at the CERN Super Proton Synchrotron: NA61/SHINE Collaboration
Measurements of multiplicity fluctuations of identified hadrons produced in inelastic p+p interactions at 31, 40, 80, and 158 GeV/c beam momentum are presented. Three different measures of multiplicity fluctuations are used: the scaled variance ω and strongly intensive measures Σ and Δ. These fluctuation measures involve second and first moments of joint multiplicity distributions. Data analysis is preformed using the Identity method which corrects for incomplete particle identification. Strongly intensive quantities are calculated in order to allow for a direct comparison to corresponding results on nucleus–nucleus collisions. The results for different hadron types are shown as a function of collision energy. A comparison with predictions of string-resonance Monte-Carlo models: EPOS, SMASH and VENUS, is also presented
Light (anti)nuclei production cross section studies in +C collisions at the NA61/SHINE experiment
NA61/SHINE is a large-acceptance fixed-target experiment located at the CERN SPS, which studies final hadronic states in interactions of various particles and nuclei. It is unique in terms of providing data on a variety of collision systems at different collision energies. This allows for wide deuteron, antiproton and antideuteron production cross-section studies. The latter are currently considered a possible dark matter interaction signal with exceptionally small background. The measurements on carbon target are important to reduce systematic experimental effects due to experiment-internal antideuteron production, as the most abundant element in the path of an incoming particle for the AMS-02 experiment is carbon. My talk will focus on analysis of NA61/SHINE data on +C thin target collisions in context of light (anti)nuclei production. I will present a preliminary analysis of experimental data and discuss quality cuts and the particle identification method as well as present deuteron and antideuteron yields
meson production in inelastic p+p interactions at 40 and 80 beam momenta measured by NA61/SHINE at the CERN SPS
Measurements of K∗(892)0 resonance production via its K+π− decay mode in inelastic p+p collisions at beam momenta 40 and 80 GeV /c (sNN−−−−√=8.8 and 12.3 GeV ) are presented. The data were recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The template method was used to extract the K∗(892)0 signal. Transverse momentum and rapidity spectra were obtained. The mean multiplicities of K∗(892)0 mesons were found to be (35.1±1.3(stat)±3.6(sys))⋅10−3 at 40 GeV /c and (58.3±1.9(stat)±4.9(sys))⋅10−3 at 80 GeV /c. The NA61/SHINE results are compared with the Epos1.99 and Hadron Resonance Gas models as well as with world data. The transverse mass spectra of K∗(892)0 mesons and other particles previously reported by NA61/SHINE were fitted within the Blast-Wave model. The transverse flow velocities are close to 0.1–0.2 of the speed of light and are significantly smaller than the ones determined in heavy nucleus-nucleus interactions at the same beam momenta
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