2,066 research outputs found
Measurement of the production of charm jets tagged with D mesons in pp collisions at = 7 TeV
The production of charm jets in proton-proton collisions at a center-of-mass
energy of TeV was measured with the ALICE detector at the CERN
Large Hadron Collider. The measurement is based on a data sample corresponding
to a total integrated luminosity of , collected using a
minimum-bias trigger. Charm jets are identified by the presence of a D
meson among their constituents. The D mesons are reconstructed from their
hadronic decay DK. The D-meson tagged jets are
reconstructed using tracks of charged particles (track-based jets) with the
anti- algorithm in the jet transverse momentum range
and pseudorapidity
. The fraction of charged jets containing a D-meson
increases with from to . The distribution of D-meson tagged jets as a
function of the jet momentum fraction carried by the D meson in the
direction of the jet axis () is reported for two ranges
of jet transverse momenta, and
in the intervals
and , respectively. The
data are compared with results from Monte Carlo event generators (PYTHIA 6,
PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum
Chromodynamics calculation, obtained with the POWHEG method and interfaced with
PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation
and underlying event.Comment: 29 pages, 8 captioned figures, 3 tables, authors from page 24,
published version, figures at http://alice-publications.web.cern.ch/node/525
Energy dependence of exclusive photoproduction off protons in ultra-peripheral p-Pb collisions at = 5.02 TeV
The ALICE Collaboration has measured the energy dependence of exclusive
photoproduction of vector mesons off proton targets in
ultra-peripheral p-Pb collisions at a centre-of-mass energy per nucleon pair
TeV. The ee and decay channels
are used to measure the cross section as a function of the rapidity of the
in the range , corresponding to an energy in the
p centre-of-mass in the interval GeV.
The measurements, which are consistent with a power law dependence of the
exclusive photoproduction cross section, are compared to previous
results from HERA and the LHC and to several theoretical models. They are found
to be compatible with previous measurements.Comment: 25 pages, 3 captioned figures, 3 tables, authors from page 19,
published version, figures at http://alice-publications.web.cern.ch/node/455
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Inclusive J/Ï production at mid-rapidity in pp collisions at âs = 5.02 TeV
Inclusive J/Ï production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of s = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity (|y| < 0.9) in the dielectron decay channel down to zero transverse momentum pT, using a data sample corresponding to an integrated luminosity of Lint = 19.4 ± 0.4 nbâ1. The measured pT-integrated inclusive J/Ï production cross sec- tion is dÏ/dy = 5.64 ± 0.22(stat.) ± 0.33(syst.) ± 0.12(lumi.) ÎŒb. The pT-differential cross section d2Ï/dpTdy is measured in the pT range 0â10 GeV/c and compared with state-of- the-art QCD calculations. The J/Ï ăpTă and ăpT2ă are extracted and compared with results obtained at other collision energies. [Figure not available: see fulltext.]
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Measurement of electrons from heavy-flavour hadron decays as a function of multiplicity in p-Pb collisions at âsNN = 5.02 TeV
The multiplicity dependence of electron production from heavy-flavour hadron decays as a function of transverse momentum was measured in p-Pb collisions at sNN = 5.02 TeV using the ALICE detector at the LHC. The measurement was performed in the centre-of-mass rapidity interval â1.07 < ycms< 0.14 and transverse momentum interval 2 < pT< 16 GeV/c. The multiplicity dependence of the production of electrons from heavy-flavour hadron decays was studied by comparing the pT spectra measured for different multiplicity classes with those measured in pp collisions (QpPb) and in peripheral p-Pb collisions (Qcp). The QpPb results obtained are consistent with unity within uncertainties in the measured pT interval and event classes. This indicates that heavy-flavour decay electron production is consistent with binary scaling and independent of the geometry of the collision system. Additionally, the results suggest that cold nuclear matter effects are negligible within uncertainties, in the production of heavy-flavour decay electrons at midrapidity in p-Pb collisions. [Figure not available: see fulltext.
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Measurement of Î (1520) production in pp collisions at âs=7TeV and pâPb collisions at âsNN=5.02TeV
The production of the Î (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s=7TeV and in pâPb collisions at sNN=5.02TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Î (1520) â pK - and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and pâPb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (Ï, K, KS0, p, Î) describes the shape of the Î (1520) transverse momentum distribution up to 3.5GeV/c in pâPb collisions. In the framework of this model, this observation suggests that the Î (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Î (1520) to the yield of the ground state particle Î remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in pâPb collisions on the Î (1520) yield
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Studies of J/Ï production at forward rapidity in PbâPb collisions at âsNN = 5.02 TeV
The inclusive J/Ï production in PbâPb collisions at the center-of-mass energy per nucleon pair sNN = 5.02 TeV, measured with the ALICE detector at the CERN LHC, is reported. The J/Ï meson is reconstructed via the dimuon decay channel at forward rapidity (2.5 < y < 4) down to zero transverse momentum. The suppression of the J/Ï yield in PbâPb collisions with respect to binary-scaled pp collisions is quantified by the nuclear modification factor (RAA). The RAA at sNN = 5.02 TeV is presented and compared with previous measurements at sNN = 2.76 TeV as a function of the centrality of the collision, and of the J/Ï transverse momentum and rapidity. The inclusive J/Ï RAA shows a suppression increasing toward higher transverse momentum, with a steeper dependence for central collisions. The modification of the J/Ï average transverse momentum and average squared transverse momentum is also studied. Comparisons with the results of models based on a transport equation and on statistical hadronization are carried out. [Figure not available: see fulltext.
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