Nonadditive composition rules for several physical quantities are treated in thermodynamics. It is argued that the zeroth law defines the existence of their additive forms, the formal logarithms. A ...further principle, the universal thermostat independence leads to a particular formal logarithm, equivalent to Tsallis entropy Sq. We connect q with generalized susceptibilities of the thermostat.
Non-extensive thermodynamics is a novel approach in high energy physics. In high-energy heavy-ion, and especially in proton-proton collisions we are far from a canonical thermal state, described by ...the Boltzmann-Gibbs statistic. In these reactions low and intermediate transverse momentum spectra are extremely well reproduced by the Tsallis-Pareto distribution, but the physical origin of Tsallis parameters is still an unsettled question. Here, we analyze whether Tsallis-Pareto energy distribution do overlap with hadron spectra at high-pT. We fitted data, measured in proton-proton (proton-antiproton) collisions in wide center of mass energy range from 200 GeV RHIC up to 7 TeV LHC energies. Furthermore, our test is extended to an investigation of a possible -dependence of the power in the Tsallis-Pareto distribution, motivated by QCD evolution equations. We found that Tsallis-Pareto distributions fit well high-pT data, in the wide center of mass energy range. Deviance from the fits appears at pT > 20–30 GeV/c, especially on CDF data 7. Introducing a pT-scaling ansatz, the fits at low and intermediate transverse momenta still remain good, and the deviations tend to disappear at the highest-pT data.
A third workshop on small-x physics, within the Small-x Collaboration, was held in Hamburg in May 2004 with the aim of overviewing recent theoretical progress in this area and summarizing the ...experimental status.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of Formula omitted 7 TeV. The ...measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of Formula omitted in pseudorapidity and a transverse momentum range of Formula omitted. The result extends the Formula omitted coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller Formula omitted. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present a study of the inclusive charged-particle transverse momentum ( Formula omitted) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity, Formula omitted, in ...pp collisions at Formula omitted and 13 TeV covering the kinematic range Formula omitted and Formula omitted GeV/c. The results are presented for events with at least one charged particle in Formula omitted (INEL Formula omitted). The Formula omitted spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The Formula omitted spectra normalized to that for INEL Formula omitted show little energy dependence. Moreover, the high- Formula omitted yields of charged particles increase faster than the charged-particle multiplicity density. The average Formula omitted as a function of multiplicity and transverse spherocity is reported for pp collisions at Formula omitted TeV. For low- (high-) spherocity events, corresponding to jet-like (isotropic) events, the average Formula omitted is higher (smaller) than that measured in INEL Formula omitted pp collisions. Within uncertainties, the functional form of Formula omitted is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average Formula omitted in jet-like events.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The measurements of the production of prompt Formula omitted, Formula omitted, Formula omitted, and Formula omitted mesons in proton-proton (pp) collisions at Formula omitted with the ALICE detector ...at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity ( Formula omitted) via their hadronic decay channels Formula omitted, Formula omitted, Formula omitted, Formula omitted, and their charge conjugates. The production cross sections were measured in the transverse momentum interval Formula omitted for Formula omitted, Formula omitted for Formula omitted and Formula omitted, and in Formula omitted for Formula omitted mesons. Thanks to the higher integrated luminosity, an analysis in finer Formula omitted bins with respect to the previous measurements at Formula omitted was performed, allowing for a more detailed description of the cross-section Formula omitted shape. The measured Formula omitted-differential production cross sections are compared to the results at Formula omitted TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at Formula omitted. This measurement will allow for a more accurate determination of the nuclear modification factor in p-Pb and Pb-Pb collisions performed at the same nucleon-nucleon centre-of-mass energy.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Jet tomography in the forward direction at RHIC Barnaföldi, G.G.; Lévai, P.; Papp, G. ...
European physical journal. C, Particles and fields,
01/2007, Letnik:
49, Številka:
1
Journal Article
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Hadron production at high pT displays a strong suppression pattern in a wide rapidity region in heavy ion collisions at RHIC energies. This finding indicates the presence of strong final state ...effects for both transversally and longitudinally traveling partons, namely induced energy loss. We have developed a perturbative QCD based model to describe hadron production in pp collisions, which can be combined with the Glauber–Gribov model to describe hadron production in heavy ion collisions. Investigating AuAu and CuCu collisions at energy at mid-rapidity, we find the opacity of the strongly interacting hot matter to be proportional to the participant nucleon number. Considering forward rapidities, the suppression pattern indicates the formation of a longitudinally contracted dense deconfined zone in central heavy ion collisions. We determine the parameters for the initial geometry from the existing data.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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