High-multiplicity pp collisions exhibit features, traditionally associated with nuclear effects. Coherence motivates to treat high-multiplicity pp, pA, and AA collisions on an equal footing. We rely ...on the phenomenological parametrization for mean multiplicities of light hadrons and J/ψ, assuming their linear dependence on Ncoll in pA collisions. The results of this approach underestimate the recently measured production rate of J/ψ at very high hadronic multiplicities. The linear dependence of J/ψ multiplicity on Ncoll is subject to predicted nonlinear corrections, related to mutual boosting of the saturation scales in colliding dense parton clouds. A parameter-free calculation of the nonlinear corrections allows us to explain data for pT-integrated yield of J/ψ at high hadronic multiplicities. Calculations are in a good accord with data binned in several pTintervals as well. As was predicted, Υ and J/ψ are equally suppressed at forward rapidities in pA collisions. Consequently, their fractional multiplicities at forward rapidities in pp collisions are equal as well, and their magnitude agrees with data.
We study string fragmentation in high multiplicity proton-proton collisions in a model where the string tension fluctuates. These fluctuations produce exponential pion spectra which are fitted to the ...transverse momentum distributions of charged particles for different multiplicities. For each multiplicity the so obtained hadronic slope parameter defines the magnitude of the string fluctuations which in turn determines the produced ratio of strange to light quarks. pythia string decay simulations are used to convert each ratio of strange to light quarks to the appropriate ratio of strange hadrons to pions.
Direct photons are an important tool for the detection of the quark-gluon plasma in ultra-relativistic nucleus-nucleus collisions. Direct-photon measurements were made in Pb + Pb collisions at ...\(\sqrt{s_{\mathrm{NN}}} = 17.2\) GeV and in Au + Au collisions at \(\sqrt{s_{\mathrm{NN}}} = 200\) GeV. These results are reviewed and compared with model calculations.
We study the electron/pion identification performance of the ALICE Transition Radiation Detector (TRD) prototypes using a neural network (NN) algorithm. Measurements were carried out for particle ...momenta from 2 to 6
GeV/
c. An improvement in pion rejection by about a factor of 3 is obtained with NN compared to standard likelihood methods.
Transverse momentum (
p
T
) spectra of neutral pions and charged hadrons measured in Au+Au and d+Au collisions at
√s
NN = 200GeV by the PHENIX experiment at RHIC are compared to p+p reference spectra ...at the same
√
s
NN. In central Au+Au collisions a factor 4 – 5 suppression for neutral pions and charged hadrons with
p
T
> 5GeV/c is found relative to the p+p reference scaled by the nuclear overlap function˚
T
AB«. In contrast, such a suppression of high
p
T
particles is absent in d+Au collisions.
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