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Adam, J.

Publications and source records attributed to Adam, J..

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Kaon femtoscopy in Pb-Pb collisions at s NN = 2.76 TeV

Here, we present the results of three-dimensional femtoscopic analyses for charged and neutral kaons recorded by ALICE in Pb-Pb collisions at s NN =2.76 TeV. Femtoscopy is used to measure the space-time characteristics of particle production from the effects of quantum statistics and final-state interactions in two-particle correlations. Kaon femtoscopy is an important supplement to that of pions because it allows one to distinguish between different model scenarios working equally well for pions. In particular, we compare the measured three-dimensional kaon radii with a purely hydrodynamical calculation and a model where the hydrodynamic phase is followed by a hadronic rescattering stage. The former predicts an approximate transverse mass (m T ) scaling of source radii obtained from pion and kaon correlations. This m T scaling appears to be broken in our data, which indicates the importance of the hadronic rescattering phase at LHC energies. A k T scaling of pion and kaon source radii is observed instead. The time of maximal emission of the system is estimated by using the three-dimensional femtoscopic analysis for kaons. The measured emission time is larger than that of pions. Our observation is well supported by the hydrokinetic model predictions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Insight into particle production mechanisms via angular correlations of identified particles in pp collisions at $\sqrt{\mathrm{s}}=7$ TeV

We measured two-particle angular correlations in pp collisions at √s=7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon–baryon and anti-baryon–anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of electrons from beauty-hadron decays in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV and Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV

The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1 s NN = 5.02 TeV and in 1.3 < pT< 8 GeV/c in the 20% most central Pb-Pb collisions at √ s NN = 2.76 TeV. The pp reference spectra at √ s NN = 5.02 TeV and √s = 2.76 TeV, needed for the calculation of the nuclear modification factors R pPb and R PbPb , were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at √s = 7 TeV. In the p T interval 3 < p T < 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower p T , the R PbPb values increase with large systematic uncertainties. The R pPb is consistent with unity within systematic uncertainties and is well described by theoretical calculations that include cold nuclear matter effects in p-Pb collisions. The measured R pPb and these calculations indicate that cold nuclear matter effects are small at high transverse momentum also in Pb-Pb collisions. Therefore, the observed reduction of R PbPb below unity at high p T may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of azimuthal correlations of D mesons with charged particles in pp collisions at √s = 7 TeV and p–Pb collisions at √s NN = 5.02 TeV

The azimuthal correlations of D mesons with charged particles were measured with the ALICE apparatus in pp collisions at s = 7 &#xA0; T e V and p–Pb collisions at s N N = 5.02 &#xA0; T e V at the Large Hadron Collider. D 0 , D + , and D &#x2217;<!-- * --> + mesons and their charge conjugates with transverse momentum 3 < p T < 16 &#xA0; G e V / c and rapidity in the nucleon-nucleon centre-of-mass system | y c m s | < 0.5 (pp collisions) and &#x2212;<!-- - --> 0.96 < y c m s < 0.04 (p–Pb collisions) were correlated to charged particles with p T > 0.3 &#xA0; G e V / c . The yield of charged particles in the correlation peak induced by the jet containing the D meson and the peak width are compatible within uncertainties in the two collision systems. The data are described within uncertainties by Monte-Carlo simulations based on PYTHIA, POWHEG, and EPOS 3 event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

W and Z boson production in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV

The W and Z boson production was measured via the muonic decay channel in proton-lead collisions at √ s NN = 5.02 TeV at the Large Hadron Collider with the ALICE detector. The measurement covers backward (–4.46 < y cms < –2.96) and forward (2.03 < y cms < 3.53) rapidity regions, corresponding to Pb-going and p-going directions, respectively. The Z-boson production cross section, with dimuon invariant mass of 60 < m μμ < 120 GeV/c 2 and muon transverse momentum (p T μ ) larger than 20 GeV/c, is measured. The production cross section and charge asymmetry of muons from W-boson decays with p T μ > 10 GeV/c are determined. The results are compared to theoretical calculations both with and without including the nuclear modification of the parton distribution functions. The W-boson production is also studied as a function of the collision centrality: the cross section of muons from W-boson decays is found to scale with the average number of binary nucleon-nucleon collisions within uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Charged-particle multiplicities in proton–proton collisions at $$\sqrt{s} = 0.9$$ s = 0.9 to 8 TeV

A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton–proton collisions, at s= 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range | η| < 2 , was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval | η| < 1. The use of an improved track-counting algorithm combined with ALICE’s measurements of diffractive processes allows a higher precision compared to our previous publications. A KNO scaling study was performed in the pseudorapidity intervals | η| < 0.5, 1.0 and 1.5. The data are compared to other experimental results and to models as implemented in Monte Carlo event generators PHOJET and recent tunes of PYTHIA6, PYTHIA8 and EPOS.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗