Search results for " Collider"
showing 10 items of 1415 documents
Forward J / ψ and D meson nuclear suppression at the LHC
2017
Abstract Using the color glass condensate formalism, we study the nuclear modification of forward J/ψ and D meson production in high energy proton-nucleus collisions at the LHC. We show that relying on the optical Glauber model to obtain the dipole cross section of the nucleus from the one of the proton fitted to HERA DIS data leads to a smaller nuclear suppression than in the first study of these processes in this formalism and a better agreement with experimental data.
Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at s=7 TeV with the ATLAS detector
2012
A measurement is presented of the cross section for the production of a W boson with one or two jets, of which at least one must be a b-jet, in pp collisions at root s = 7 TeV. Production via top d ...
Measurement of the cross-section for b-jets produced in association with a Z boson at s=7 TeV with the ATLAS detector
2012
A measurement is presented of the inclusive cross-section for b-jet production in association with a Z boson in pp collisions at a centre-of-mass energy of root s = 7 TeV. The analysis uses the data sample collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb(-1). The event selection requires a Z boson decaying into high P-T electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse momentum p(T) > 25 GeV and rapidity vertical bar y vertical bar < 2.1. After subtraction of background processes, the yield is extracted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-se…
Measurement of the inclusive isolated prompt photon cross-section in pp collisions at s=7 TeV using 35 pb−1 of ATLAS data
2011
A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement cove ...
Transverse momenta of partons and dimuons in QCD
1978
Abstract Intrinsic (primordial) transverse momenta of quarks and gluons are calculated as well as those arising from recoil (bremsstrahlung) effects, using only the well-known parton distributions as input. The intrinsic kT's lie typically in the range of 150–250 MeV. Recent approaches using heuristic integro-differential equations for kT distributions of partons are shown to disagree with the results obtained by rigorous QCD calculations. The transverse momenta of dimuon pairs produced in pp → μ+μ− + X at the ISR can be solely explained by dynamical recoil effects, i.e., q q →(μ + μ − ) g and gq →(μ + μ − ) q , and no significant intrinsic transverse parton momenta are required. These dimu…
Renormalization group evolution of multi-gluon correlators in high energy QCD
2011
Many-body QCD in leading high energy Regge asymptotics is described by the Balitsky-JIMWLK hierarchy of renormalization group equations for the x evolution of multi-point Wilson line correlators. These correlators are universal and ubiquitous in final states in deeply inelastic scattering and hadronic collisions. For instance, recently measured di-hadron correlations at forward rapidity in deuteron-gold collisions at the Relativistic Heavy Ion Collider (RHIC) are sensitive to four and six point correlators of Wilson lines in the small x color fields of the dense nuclear target. We evaluate these correlators numerically by solving the functional Langevin equation that describes the Balitsky-…
Collision centrality andτ0dependence of the emission of thermal photons from a fluctuating initial state in an ideal hydrodynamic calculation
2012
Fluctuations in the initial QCD matter density distribution are found to enhance the production of thermal photons significantly in the range $2\ensuremath{\leqslant}{p}_{T}\ensuremath{\leqslant}4$ GeV/$c$ compared to a smooth initial state averaged profile in ideal hydrodynamic calculation for $200A$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and $2.76A$ TeV Pb+Pb collisions at the Large Hadron Collider (LHC). The thermal emission of photons is strongly dependent on the initial temperature of the system where the presence of ``hot spots'' in the initial state translates into enhanced production of photons compared to a smooth profile. The effect of fluctuations in t…
Determination of the pole and MS¯ masses of the top quark from the tt¯ cross section
2011
We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the ttbar cross section measured in the lepton+jets channel in ppbar collisions at sqrt(s)=1.96 TeV using 5.3 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and MSbar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
Neutral pion production with respect to centrality and reaction plane in Au+Au collisions atsNN=200GeV
2013
The PHENIX experiment has measured the production of pi(0)s in Au + Au collisions at root S-NN = 200 GeV. The new data offer a fourfold increase in recorded luminosity, providing higher precision and a larger reach in transverse momentum, p(T), to 20 GeV/c. The production ratio of eta/pi(0) is 0.46 +/- 0.01(stat) +/- 0.05(syst), constant with p(T) and collision centrality. The observed ratio is consistent with earlier measurements, as well as with the p + p and d + Au values. pi(0) are suppressed by a factor of 5, as in earlier findings. However, with the improved statistical precision a small but significant rise of the nuclear modification factor R-AA vs p(T), with a slope of 0.0106 +/-(0…
Measurement of Dijet Azimuthal Decorrelations inppCollisions ats=7 TeV
2011
Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set ( integral Ldt = 36 pb(-1)) acquired by the ATLAS detector during the 2010 root s = 7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime.