Search results for "Collider"
showing 10 items of 1690 documents
Search for a standard model Higgs boson in the H→ZZ→ℓ+ℓ−νν¯ decay channel using 4.7 fb−1 of s=7 TeV data with the ATLAS detector
2012
A search for a Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-) nu(nu) over bar, where l represents electrons or muons, is presented. It is based on proton-proton collision data at ...
Nuclear PDFs in the beginning of the LHC era
2014
The status of the global fits of nuclear parton distributions (nPDFs) is reviewed. In addition to comparing the contemporary analyses of nPDFs, difficulties and controversies posed by the neutrino-nucleus deeply inelastic scattering data is overviewed. At the end, the first dijet data from the LHC proton+lead collisions is briefly discussed.
Charmonia production in hadron colliders and the extraction of colour-octet matrix elements
1997
We present the results of our analysis on charmonia ($J/\psi$ and $\psi'$) hadroproduction taking into account higher-order QCD effects induced by initial-state radiation in a Monte Carlo framework, with the colour-octet mechanism implemented in the event generation. We find that those colour-octet matrix elements extracted so far from Fermilab Tevatron data for both $J/\psi$ and $\psi'$ production have to be lowered significantly. We finally make predictions for charmonia production at the LHC, presenting a code for a fast simulation with PYTHIA based on the colour-octet model.
Monte Carlo Simulation for Elastic Energy Loss of Hard Partons in a Hydrodynamical Background
2011
We have developed a Monte Carlo simulation describing the $2 \rightarrow 2$ scatterings of perturbatively produced, non-eikonally propagating high-energy partons with the quarks and gluons of the expanding QCD medium created in ultrarelativistic heavy ion collisions. The partonic scattering rates are computed in leading-order perturbative QCD (pQCD), while three different hydrodynamical scenarios are used to model the strongly interacting medium. We compare our results and tune the model with the neutral pion suppression observed in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions at the BNL-RHIC. We find the incoherent nature of elastic energy loss incompatible with the measured angular dependence…
YaJEM — A MONTE CARLO CODE FOR IN-MEDIUM SHOWER EVOLUTION
2010
High transverse momentum (P_T) QCD scattering processes are regarded as a valuable tool to study the medium produced in heavy-ion collisions, as due to uncertainty arguments their cross section should be calculable independent of medium properties whereas the medium then modifies only the final state partons emerging from a hard vertex. With the heavy-ion physics program at the CERN LHC imminent, the attention of high P_T physics in heavy ion collisions is shifting from the observation of hard single hadrons to fully reconstructed jets. However, the presence of a background medium at low P_T complicates jet-finding as compared to p-p collisions. Monte-Carlo (MC) codes designed to simulate t…
Measurements of differential cross sections of Z/γ∗+jets+X events in pp¯ collisions at s=1.96 TeV
2009
We present cross section measurements for Z/gamma* + jets + X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the DO detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb(-1). Leading and next-to-leading order perturbative QCD predictions are compared with the measurements. and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. …
Measurement of the ratio of three-jet to two-jet cross sections in pp¯ collisions at s=1.96 TeV
2013
We present a measurement of the ratio of multijet cross sections in pp-bar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the PYTHIA event generator do not agree with the data, while SHERPA provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, correcte…
Measurement of D⁎±, D± and Ds± meson production cross sections in pp collisions at s=7 TeV with the ATLAS detector
2016
The production of D*(+/-), D-+/- and D-S(+/-) charmed mesons has been measured with the ATLAS detector in pp collisions at,/7s = 7 TeV at the LHC, using data corresponding to an integrated luminosi ...
Analysis of the deuteron spin structure by COMPASS
2007
New results on the longitudinal inclusive spin asymmetry A 1 d in the range 1 Q 2 100 (GeV/c) 2 and 0.004 x 0.7 are presented. From these results we derive the spin-dependent structure function g 1 d which we include in a QCD analysis of the world data. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered off a large polarized 6 LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy in the region 0.004 x 0.03 .
Charged-pion cross sections and double-helicity asymmetries in polarizedp+pcollisions ats=200 GeV
2015
We present midrapidity charged-pion invariant cross sections, the ratio of the pi(-) to pi(+) cross sections and the charge-separated double-spin asymmetries in polarized p + p collisions at root s = p + 200 GeV. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The char…