Search results for "PP collision"
showing 10 items of 51 documents
Top-quark production in proton–nucleus and nucleus–nucleus collisions at LHC energies and beyond
2015
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and eff…
Measuring KS0K± interactions using pp collisions at √s = 7 TeV
2019
We present the first measurements of femtoscopic correlations between the K0 S and K± particles in pp collisions at √s = 7 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding solely via the a0(980) resonance. The extracted kaon source radius and correlation strength parameters for K0 SK− are found to be equal within the experimental uncertainties to those for K0 SK+. Results of the present study are compared with those from identical-kaon femtoscopic studies also performed with pp collisions at √s = 7 TeV by ALICE and with a K0 SK± measurement in Pb–Pb collisions at √sNN = 2.76 TeV. Combined with the Pb–Pb resul…
Measurement of Upsilon production in collisions at root s=2.76 TeV
2014
The production of Υ(1S) , Υ(2S) and Υ(3S) mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 3.3pb-1 collected in proton–proton collisions at a centre-of-mass energy of s=2.76 TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the Υ transverse momentum and rapidity, over the ranges pT<15 GeV/ c and 2.0<y<4.5 . The total cross-sections in this kinematic region, assuming unpolarised production, are measured to be σpp→Υ(1S)X×BΥ(1S)→μ+μ-=1.111±0.043±0.044nb,σpp→Υ(2S)X×BΥ(2S)→μ+μ-=0.264±0.023±0.011nb,σpp→Υ(3S)X×BΥ(3S)→μ+μ-=0.159±0.020±0.…
Upgrade of the ALICE Experiment Letter Of Intent
2014
ALICE (A Large Ion Collider Experiment) is studying the physics of strongly interacting matter, and in particular the properties of the Quark–Gluon Plasma (QGP), using proton–proton, proton–nucleus and nucleus–nucleus collisions at the CERN LHC (Large Hadron Collider). The ALICE Collaboration is preparing a major upgrade of the experimental apparatus, planned for installation in the second long LHC shutdown in the years 2018–2019. These plans are presented in the ALICE Upgrade Letter of Intent, submitted to the LHCC (LHC experiments Committee) in September 2012. In order to fully exploit the physics reach of the LHC in this field, high- precision measurements of the heavy-flavour production…
Confronting current NLO parton fragmentation functions with inclusive charged-particle spectra at hadron colliders
2013
The inclusive spectra of charged particles measured at high transverse momenta ($p_T\gtrsim$2GeV/c) in proton-proton and proton-antiproton collisions in the range of center-of-mass energies $\sqrt{s}=200-7000$GeV are compared with next-to-leading order perturbative QCD calculations using seven recent sets of parton-to-hadron fragmentation functions (FFs). Accounting for the uncertainties in the scale choices and in the parton distribution functions, we find that most of the theoretical predictions tend to overpredict the measured LHC and Tevatron cross sections by up to a factor of two. We identify the currently too-hard gluon-to-hadron FFs as the probable source of the problem, and justify…
Search for massive colored scalars in four-jet final states in √s = 7 TeV proton–proton collisions with the ATLAS detector
2011
A search for pair-produced scalar particles decaying to a four-jet final state is presented. The analysis is performed using an integrated luminosity of 34 pb[superscript −1] recorded by the ATLAS detector in 2010. No deviation from the Standard Model is observed. For a scalar mass of 100 GeV (190 GeV) the limit on the scalar gluon pair production cross section at 95% confidence level is 1 nb (0.28 nb). When these results are interpreted as mass limits, scalar-gluons (hyperpions) with masses of 100 to 185 GeV (100 to 155 GeV) are excluded at 95% confidence level with the exception of a mass window of width about 5 GeV (15 GeV) around 140 GeV.
Measurement of photon?jet transverse momentum correlations in 5.02 TeV Pb + Pb and pp collisions with ATLAS
2019
Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb−1 of Pb + Pb collision data at TeV and 25 pb−1 of pp collision data at TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum GeV and are paired with all jets in the event that have GeV and pseudorapidity . The transverse momentum balance given by the jet-to-photon ratio, , is measured for pairs with azimuthal opening angle . Distributions of the per-photon jet yield as a function…
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at √s = 7 TeV with the ATLAS detector
2011
The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton–proton collisions at a centre-of-mass energy of √s =7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb[superscript −1]. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the ra…
Measurement of the inclusive J/ψ polarization at forward rapidity in pp collisions at √s = 8 TeV
2018
We report on the measurement of the inclusive J/ ψ polarization parameters in pp collisions at a center of mass energy s√=8 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb −1 . J/ ψ resonances are reconstructed in their di-muon decay channel in the rapidity interval 2.5<y<4.0 and over the transverse-momentum interval 2<pT<15 GeV/c . The three polarization parameters ( λθ , λφ , λθφ ) are measured as a function of pT both in the helicity and Collins-Soper reference frames. The measured J/ ψ polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all ava…
Energy dependence of forward-rapidity J/ψ and ψ(2S) production in pp collisions at the LHC
2017
We present results on transverse momentum (pt) and rapidity (y) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/ψ and ψ(2S) at forward rapidity (2.5 15 GeV/c the non-prompt contribution reaches up to 50% of the total charmonium yield. peerReviewed