We present measurements of the cross section and double-helicity asymmetry ALL of direct-photon production in p→+p→ collisions at s=510 GeV. The measurements have been performed at midrapidity (|η|
The ALICE experiment has measured the inclusive J/ψ production in Pb-Pb collisions at √ s NN = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4 . A suppression of the ...inclusive J/ψ yield in Pb-Pb is observed with respect to the one measured in ppcollisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%–80% most central collisions, is 0.545 ± 0.032 ( stat ) ± 0.083 ( syst ) and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/ψ production from charm quarks in a deconfined partonic phase can describe our data.
Suppression of the J/ψ nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was ...attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the ψ(2S) state in p+A and d+A collisions suggested the presence of final-state effects. Results of J/ψ and ψ(2S) measurements in the dimuon decay channel are presented here for p+p, p+Al, and p+Au collision systems at sNN=200GeV. The results are predominantly shown in the form of the nuclear-modification factor, RpA, the ratio of the ψ(2S) invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in p+p collisions. Measurements of the J/ψ and ψ(2S) nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large Hadron Collider energies.
The first measurement of two-pion Bose–Einstein correlations in central Pb–Pb collisions at sNN=2.76 TeV at the Large Hadron Collider is presented. We observe a growing trend with energy now not only ...for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.
A
bstract
Inclusive J/
ψ
production has been studied with the ALICE detector in p-Pb collisions at the nucleon-nucleon center of mass energy
= 5.02 TeV at the CERN LHC. The measurement is performed ...in the center of mass rapidity domains 2.03
< y
cms
<
3
.
53 and −4
.
46
< y
cms
<
−2
.
96, down to zero transverse momentum, studying the
μ
+
μ
−
decay mode. In this paper, the J/
ψ
production cross section and the nuclear modification factor
R
pPb
for the rapidities under study are presented. While at forward rapidity, corresponding to the proton direction, a suppression of the J/
ψ
yield with respect to binary-scaled pp collisions is observed, in the backward region no suppression is present. The ratio of the forward and backward yields is also measured differentially in rapidity and transverse momentum. Theoretical predictions based on nuclear shadowing, as well as on models including, in addition, a contribution from partonic energy loss, are in fair agreement with the experimental results.
The PHENIX experiment reports systematic measurements at the Relativistic Heavy Ion Collider of φ-meson production in asymmetric Cu+Au collisions at sNN=200GeV and in U+U collisions at sNN=193GeV. ...Measurements were performed via the φ→K+K- decay channel at midrapidity |η|
The p{sub t}-differential inclusive production cross sections of the prompt charmed mesons D{sup 0}, D{sup +}, and D{sup {sm_bullet}+} in the rapidity range |y| < 0.5 were measured in proton-proton ...collisions at {radical}s = 7 TeV at the LHC using the ALICE detector. Reconstructing the decays D{sup 0} {yields} K{sup -}{pi}{sup +}, D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +}, D{sup {sm_bullet}+} {yields} D{sup 0}{pi}{sup +}, and their charge conjugates, about 8,400 D{sup 0}, 2,900 D{sup +}, and 2,600 D{sup {sm_bullet}+} mesons with 1 < p{sub t} < 24 GeV/c were counted, after selection cuts, in a data sample of 3.14 x 10{sup 8} events collected with a minimum-bias trigger (integrated luminosity L{sub int} = 5 nb{sup -1}). The results are described within uncertainties by predictions based on perturbative QCD.
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