(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production of the strange and double-strange baryon resonances (..., ...) has been measured at mid-rapidity (... ...) ...in proton-proton collisions at ... ... 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the ... pentaquark, decaying in the ... channel, has been carried out but no evidence is seen.
A measurement of the transverse momentum spectra of jets in Pb-Pb collisions at sqrt(sNN)=2.76TeV is reported. Jets are reconstructed from charged particles using the anti-k_T jet algorithm with jet ...resolution parameters R of 0.2 and 0.3 in pseudo-rapidity |eta|<0.5. The transverse momentum p_T of charged particles is measured down to 0.15 GeV/c which gives access to the low p_T fragments of the jet. Jets found in heavy-ion collisions are corrected event-by-event for average background density and on an inclusive basis (via unfolding) for residual background fluctuations and detector effects. A strong suppression of jet production in central events with respect to peripheral events is observed. The suppression is found to be similar to the suppression of charged hadrons, which suggests that substantial energy is radiated at angles larger than the jet resolution parameter R=0.3 considered in the analysis. The fragmentation bias introduced by selecting jets with a high p_T leading particle, which rejects jets with a soft fragmentation pattern, has a similar effect on the jet yield for central and peripheral events. The ratio of jet spectra with R=0.2 and R=0.3 is found to be similar in Pb-Pb and simulated PYTHIA pp events, indicating no strong broadening of the radial jet structure in the reconstructed jets with R<0.3.
The production of the strange and double-strange baryon resonances (Formula: see text, Formula: see text) has been measured at mid-rapidity (Formula: see textFormula: see text) in proton-proton ...collisions at Formula: see text Formula: see text 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the Formula: see text pentaquark, decaying in the Formula: see text channel, has been carried out but no evidence is seen.
Invariant yields of neutral pions at midrapidity in the transverse momentum range 0.6 < p T < 12 GeV/c mea-sured in Pb–Pb collisions at √ s NN = 2.76 TeV are presented for six centrality classes. The ...pp reference spectrum was mea-sured in the range 0.4 < p T < 10 GeV/c at the same center-of-mass energy. The nuclear modification factor, R AA , shows a suppression of neutral pions in central Pb–Pb collisions by a factor of up to about 8−10 for 5 p T 7 GeV/c. The presented measurements are compared with results at lower center-of-mass energies and with theoretical calculations.
The transverse momentum (p T) distribution of primary charged particles is measured at midrapidity in minimum-bias p–Pb collisions at √ s NN = 5.02 TeV with the ALICE detector at the LHC in the range ...0.15 < p T < 50 GeV/c. The spectra are compared to the expectation based on binary collision scaling of particle production in pp colli-sions, leading to a nuclear modification factor consistent with unity for p T larger than 2 GeV/c, with a weak indication of a Cronin-like enhancement for p T around 4 GeV/c. The mea-surement is compared to theoretical calculations and to data in Pb–Pb collisions at √ s NN = 2.76 TeV. Measurements of particle production in proton-nucleus colli-sions at high energies enable the study of fundamental proper-ties of Quantum Chromodynamics (QCD) over a broad range of parton fractional momentum x and parton densities (see 1 for a review). They also provide reference measurements for the studies of deconfined matter created in nucleus–nucleus collisions 2. The first measurements of charged-particle production in minimum-bias p–Pb collisions at the LHC at a centre-of-mass energy per nucleon-nucleon pair of √ s NN = 5.02 TeV
The p_{T}-differential production cross sections of the prompt charmed mesons D^{0}, D^{+}, D^{*+}, and D_{s}^{+} and their charge conjugate in the rapidity interval -0.96<y_{cms}<0.04 were measured ...in p-Pb collisions at a center-of-mass energy sqrts_{NN}=5.02 TeV with the ALICE detector at the LHC. The nuclear modification factor R_{pPb}, quantifying the D-meson yield in p-Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%-20% uncertainties with unity in the transverse momentum interval 1<p_{T}<24 GeV/c. No significant difference among the R_{pPb} of the four D-meson species is observed. The results are described within uncertainties by theoretical calculations that include initial-state effects. The measurement adds experimental evidence that the modification of the momentum spectrum of D mesons observed in Pb-Pb collisions with respect to pp collisions is due to strong final-state effects induced by hot partonic matter.
We present the first measurement at the LHC of exclusive J/ψ photoproduction off protons, in ultraperipheral proton-lead collisions at sqrts_{NN}=5.02 TeV. Events are selected with a dimuon pair ...produced either in the rapidity interval, in the laboratory frame, 2.5<y<4 (p-Pb) or -3.6<y<-2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections σ(γ+p→J/ψ+p) are 33.2±2.2(stat)±3.2(syst)±0.7(theor) nb in p-Pb and 284±36(stat)_{-32}^{+27}(syst)±26(theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the γp center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/ψ photoproduction cross section in γp energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between ∼2×10^{-2} and ∼2×10^{-5}, thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.
Abstract The ALICE Collaboration has studied the inclusive production of the charmonium state psi(2S) in proton-lead (p-Pb) collisions at the nucleon-nucleon centre of mass energy ... = 5.02 TeV at ...the CERN LHC. The measurement was performed at forward (2.03 < y cms < 3.53) and backward (-4.46 < y cms < -2.96) centre of mass rapidities, studying the decays into muon pairs. In this paper, we present the inclusive production cross sections sigma psi(2S), both integrated and as a function of the transverse momentum p T, for the two y cms domains. The results are compared to those obtained for the 1S vector state (J/psi), by showing the ratios between the production cross sections, as well as the double ratios sigma psi(2S) /sigma J/psi pPb /sigma psi(2S) /sigma J/psipp between p-Pb and proton-proton collisions. Finally, the nuclear modification factor for inclusive psi(2S) is evaluated and compared to the measurement of the same quantity for J/psi and to theoretical models including parton shadowing and coherent energy loss mechanisms. The results show a significantly larger suppression of the psi(2S) compared to that measured for J/psi and to models. These observations represent a clear indication for sizeable final state effects on psi(2S) production. Figure not available: see fulltext.
...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1434-6044/small "Production of [Sigma](1385)^sup +/-^ and [Xi](1530)^sup 0^ in proton-proton collisions at [SQRT]s = 7 TeV")
PDF
