The pseudorapidity density of charged particles, Formula omitted, in p-Pb collisions has been measured at a centre-of-mass energy per nucleon-nucleon pair of Formula omitted = 8.16 TeV at ...mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, Formula omitted. The Formula omitted value is Formula omitted at Formula omitted. This quantity divided by Formula omitted / 2 is Formula omitted, where Formula omittedis the average number of participating nucleons, is 9.5% higher than the corresponding value for p-Pb collisions at Formula omitted = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the Formula omitted distribution. Saturation-based models reproduce the distributions well for Formula omitted. The Formula omitted is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p-Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.
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Where does the energy loss lose strength? Barnaföldi, G G; Fai, G; Lévai, P ...
Journal of physics. G, Nuclear and particle physics,
10/2008, Letnik:
35, Številka:
10
Journal Article, Conference Proceeding
The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of Formula omitted vector mesons off proton targets in ultra-peripheral p-Pb collisions at a centre-of-mass ...energy per nucleon pair Formula omitted TeV. The e Formula omittede Formula omitted and Formula omitted decay channels are used to measure the cross section as a function of the rapidity of the Formula omitted in the range Formula omitted, corresponding to an energy in the Formula omittedp centre-of-mass in the interval Formula omitted GeV. The measurements, which are consistent with a power law dependence of the exclusive Formula omitted 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.
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First results on Formula omitted, Formula omitted and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in Formula omitted collisions at Formula ...omitted. The observable Formula omitted, which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for Formula omitted show a change of sign in Formula omitted from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and Formula omitted exhibits a change in sign for Formula omitted and K/p.
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Is strangeness still strange at the LHC? Barnaföldi, G G; Fai, G; Lévai, P ...
Journal of physics. G, Nuclear and particle physics,
04/2008, Letnik:
35, Številka:
4
Journal Article, Conference Proceeding
Neutral pion and Formula omitted meson invariant differential yields were measured in non-single diffractive p-Pb collisions at Formula omitted = 5.02 TeV with the ALICE experiment at the CERN LHC. ...The analysis combines results from three complementary photon measurements, utilizing the PHOS and EMCal calorimeters and the Photon Conversion Method. The invariant differential yields of Formula omitted and Formula omitted meson inclusive production are measured near mid-rapidity in a broad transverse momentum range of Formula omitted and Formula omitted, respectively. The measured Formula omitted ratio increases with Formula omitted and saturates for Formula omitted > 4 Formula omitted at Formula omitted. A deviation from Formula omitted scaling is observed for Formula omitted 2 Formula omitted. The measured Formula omitted ratio is consistent with previous measurements from proton-nucleus and pp collisions over the full Formula omitted range. The measured Formula omitted ratio at high Formula omitted also agrees within uncertainties with measurements from nucleus-nucleus collisions. The Formula omitted and Formula omitted yields in p-Pb relative to the scaled pp interpolated reference, Formula omitted, are presented for Formula omitted 20 Formula omitted and Formula omitted 20 Formula omitted, respectively. The results are compared with theoretical model calculations. The values of Formula omitted are consistent with unity for transverse momenta above 2 Formula omitted. These results support the interpretation that the suppressed yield of neutral mesons measured in Pb-Pb collisions at LHC energies is due to parton energy loss in the hot QCD medium.
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We report on the measurement of the inclusive J/ Formula omitted polarization parameters in pp collisions at a center of mass energy Formula omitted 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 Formula omitted. J/ Formula omitted resonances are reconstructed in their di-muon decay channel in the rapidity interval Formula omitted and over the transverse-momentum interval Formula omitted Formula omitted. The three polarization parameters ( Formula omitted, Formula omitted, Formula omitted) are measured as a function of Formula omitted both in the helicity and Collins-Soper reference frames. The measured J/ Formula omitted polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at Formula omitted TeV.
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Formula omitted meson measurements provide insight into strangeness production, which is one of the key observables for the hot medium formed in high-energy heavy-ion collisions. ALICE measured ...Formula omitted production through its decay in muon pairs in Pb-Pb collisions at Formula omitted TeV in the intermediate transverse momentum range Formula omitted GeV/c and in the rapidity interval Formula omitted. The Formula omitted yield was measured as a function of the transverse momentum and collision centrality. The nuclear modification factor was obtained as a function of the average number of participating nucleons. Results were compared with the ones obtained via the kaon decay channel in the same Formula omitted range at midrapidity. The values of the nuclear modification factor in the two rapidity regions are in agreement within uncertainties.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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