A
bstract
Transverse momentum spectra of identified particles produced in heavy-ion collisions at the Large Hadron Collider are described with relativistic fluid dynamics. We perform a systematic ...comparison of experimental data for pions, kaons and protons up to a transverse momentum of 3 GeV
/c
with calculations using the F
luid
u
M code package to solve the evolution equations of fluid dynamics, the T
r
ENT
o
model to describe the initial state and the F
ast
R
eso
code to take resonance decays into account. Using data in five centrality classes at the center-of-mass collision energy per nucleon pair
s
NN
= 2
.
76 TeV, we determine systematically the most likely parameters of our theoretical model including the shear and bulk viscosity to entropy ratios, the initialization time, initial density and freeze-out temperature through a global search and quantify their posterior probability. This is facilitated by the very efficient numerical implementation of F
luid
u
M and F
ast
R
eso
. Based on the most likely model parameters we present predictions for the transverse momentum spectra of multi-strange hadrons as well as identified particle spectra from Pb-Pb collisions at
s
NN
= 5
.
02 TeV.
Abstract A study of prompt and non-prompt $$\mathrm {J}/\psi $$ J/ψ production as a function of charged-particle multiplicity in inelastic proton–proton (pp) collisions at a centre-of-mass energy of ...$$\sqrt{s}$$ s = 13 TeV based on calculations using the PYTHIA8 Monte Carlo is reported. Recent experimental data shows an intriguing stronger-than-linear increase of the self-normalized $$\mathrm {J}/\psi $$ J/ψ yield with multiplicity; several models, based on initial or final state effects, have been able to describe the observed behaviour. In this paper, the microscopic reasons for this behaviour, like the role of multiple parton interactions, colour reconnections and auto-correlations are investigated. It is observed that the stronger-than-linear increase and the transverse momentum ($$p_\mathrm {T}$$ pT ) dependence, contrary to what is predicted by the other available models, can be attributed to auto-correlation effects only. In absence of auto-correlation effects, the increase of the yield of $$\mathrm {J}/\psi $$ J/ψ with multiplicity – and in general for all hard processes – is weaker than linear for multiplicities exceeding about three times the mean multiplicity. The possibility of disentangling auto-correlation effects from other physical phenomena by measuring the charged-particle multiplicity in different pseudo-rapidity and azimuthal regions relative to the $$\mathrm {J}/\psi $$ J/ψ direction is investigated. In this regard, it is suggested to extend the experimental measurements of $$\mathrm {J}/\psi $$ J/ψ production as a function of the charged-particle multiplicity by determining the multiplicity in several azimuthal regions and in particular in the Transverse region with respect to the direction of the $$\mathrm {J}/\psi $$ J/ψ meson.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A study of prompt and non-prompt
J
/
ψ
production as a function of charged-particle multiplicity in inelastic proton–proton (pp) collisions at a centre-of-mass energy of
s
= 13 TeV based on ...calculations using the PYTHIA8 Monte Carlo is reported. Recent experimental data shows an intriguing stronger-than-linear increase of the self-normalized
J
/
ψ
yield with multiplicity; several models, based on initial or final state effects, have been able to describe the observed behaviour. In this paper, the microscopic reasons for this behaviour, like the role of multiple parton interactions, colour reconnections and auto-correlations are investigated. It is observed that the stronger-than-linear increase and the transverse momentum (
p
T
) dependence, contrary to what is predicted by the other available models, can be attributed to auto-correlation effects only. In absence of auto-correlation effects, the increase of the yield of
J
/
ψ
with multiplicity – and in general for all hard processes – is weaker than linear for multiplicities exceeding about three times the mean multiplicity. The possibility of disentangling auto-correlation effects from other physical phenomena by measuring the charged-particle multiplicity in different pseudo-rapidity and azimuthal regions relative to the
J
/
ψ
direction is investigated. In this regard, it is suggested to extend the experimental measurements of
J
/
ψ
production as a function of the charged-particle multiplicity by determining the multiplicity in several azimuthal regions and in particular in the Transverse region with respect to the direction of the
J
/
ψ
meson.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Heavy-ion collisions are well described by a dynamical evolution with a long hydrodynamical phase. In this phase the properties of the strongly coupled quark-gluon plasma are reflected in the ...equation of state (EoS) and the transport coefficients, most prominently by the shear and bulk viscosity over entropy density ratios η/s(T) and ζ/s(T), respectively. While the EoS is by now known to a high accuracy, the transport coefficients and in particular their temperature and density dependence are not well known from first-principle computations yet, as well as the possible influence they can have once used in hydrodynamical simulations. In this work, the most recent QCD-based parameters are provided as input to the MUSIC framework. A ratio η/s(T) computed with a QCD based approach is used for the first time. The IP-Glasma model is used to describe the initial energy density distribution, and UrQMD for the dilute hadronic phase. Simulations are performed for Pb–Pb collisions at sNN=2.76 TeV, for different centrality intervals. The resulting kinematic distributions of the particles produced in the collisions are compared to data from the LHC, for several experimental observables. The high precision of the experimental results and the broad variety of observables considered allow to critically verify the quality of the description based on first-principle input to the hydrodynamic evolution.
A study of prompt and non-prompt Formula omitted production as a function of charged-particle multiplicity in inelastic proton-proton (pp) collisions at a centre-of-mass energy of Formula omitted = ...13 TeV based on calculations using the PYTHIA8 Monte Carlo is reported. Recent experimental data shows an intriguing stronger-than-linear increase of the self-normalized Formula omitted yield with multiplicity; several models, based on initial or final state effects, have been able to describe the observed behaviour. In this paper, the microscopic reasons for this behaviour, like the role of multiple parton interactions, colour reconnections and auto-correlations are investigated. It is observed that the stronger-than-linear increase and the transverse momentum ( Formula omitted) dependence, contrary to what is predicted by the other available models, can be attributed to auto-correlation effects only. In absence of auto-correlation effects, the increase of the yield of Formula omitted with multiplicity - and in general for all hard processes - is weaker than linear for multiplicities exceeding about three times the mean multiplicity. The possibility of disentangling auto-correlation effects from other physical phenomena by measuring the charged-particle multiplicity in different pseudo-rapidity and azimuthal regions relative to the Formula omitted direction is investigated. In this regard, it is suggested to extend the experimental measurements of Formula omitted production as a function of the charged-particle multiplicity by determining the multiplicity in several azimuthal regions and in particular in the Transverse region with respect to the direction of the Formula omitted meson.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Heavy quarks, i.e. charm and beauty, are produced on a shorter time scale
with respect to the strongly-interacting matter produced in high-energy
heavy-ion collisions. Therefore, they are unique ...probes to study the mechanisms
of parton energy loss, hadronisation and thermalization in the hot and dense
state of matter. The nuclear modification factor ($R_{\rm AA}$) and the
elliptic flow ($v_{2}$) are two of the main experimental observables that allow
us to investigate the interaction strength of heavy quarks with the medium. The
most recent results on heavy-flavour production and elliptic flow measured by
the ALICE collaboration in Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76
TeV will be discussed.
The formation of hadrons is a fundamental process in nature that can be investigated at particle colliders. As several recent findings demonstrate, with \(\mathrm{e^+e^-}\) collisions as a ..."vacuum-like" reference at one extreme, and central nucleus--nucleus as a dense, extended-size system characterized by flow and local equilibrium at the opposite extreme, different collision systems offer a lever arm that can be exploited to probe with a range of heavy-flavour hadron species the onset of various hadronization processes. In this review, we present an overview of the theoretical and experimental developments. The focus is on open-heavy-flavour measurements. The comparison with model predictions and connections among the results in electron-positron, proton--proton, proton--nucleus, nucleus--nucleus collisions are discussed. After reviewing the current state, we suggest some prospects and future developments.
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