A
bstract
Next-to-leading order (NLO) QCD predictions for the production of heavy quarks in proton-proton collisions are presented within three different approaches to quark mass, resummation and ...fragmentation effects. In particular, new NLO and parton shower simulations with POWHEG are performed in the ALICE kinematic regime at three different centre-of-mass energies, including scale and parton density variations, in order to establish a reliable baseline for future detailed studies of heavy-quark suppression in heavy-ion collisions. Very good agreement of POWHEG is found with FONLL, in particular for centrally produced
D
0
,
D
+
and
D
*+
mesons and electrons from charm and bottom quark decays, but also with the generally somewhat higher GM-VFNS predictions within the theoretical uncertainties. The latter are dominated by scale rather than quark mass variations. Parton density uncertainties for charm and bottom quark production are computed here with POWHEG for the first time and shown to be dominant in the forward regime, e.g. for muons coming from heavy-flavour decays. The fragmentation into
D
s
mesons seems to require further tuning within the NLO Monte Carlo approach.
A
bstract
In this paper we present a study of in-medium jet modifications performed with JEWEL and PYTHIA 6.4, focusing on the uncertainties related to variations of the perturbative scales and ...nuclear parton distribution functions (PDFs) and on the impact of the initial and crossover temperature variations of the medium. The simulations are compared to LHC data for the jet spectrum and the nuclear modification factor. We assess the interplay between the choice of nuclear PDFs and different medium parameters and study the impact of nuclear PDFs and the medium on the jet structure via the Lund plane.
We present a calculation of the elliptic flow of electrons from beauty-hadron decays in semi-central Pb-Pb collisions at centre-of-mass energy per colliding nucleon pair, represented as Formula ...omitted, of 2.76 TeV. The result is obtained by the subtraction of the charm-quark contribution in the elliptic flow of electrons from heavy-flavour hadron decays in semi-central Pb-Pb collisions at Formula omitted recently made publicly available by the ALICE collaboration.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present a calculation of the elliptic flow of electrons from beauty-hadron decays in semi-central Pb–Pb collisions at centre-of-mass energy per colliding nucleon pair, represented as sNN, of 2.76 ...TeV. The result is obtained by the subtraction of the charm-quark contribution in the elliptic flow of electrons from heavy-flavour hadron decays in semi-central Pb–Pb collisions at sNN=2.76TeV recently made publicly available by the ALICE collaboration.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
We present a systematic theoretical analysis of the ALICE measurement of low-
p
T
direct-photon production in central lead-lead collisions at the LHC with a centre-of-mass-energy of
TeV. ...Using NLO QCD, we compute the relative contributions to prompt-photon production from different initial and final states and the theoretical uncertainties coming from independent variations of the renormalisation and factorisation scales, the nuclear parton densities and the fragmentation functions. Based on different fits to the unsubtracted and prompt-photon subtracted ALICE data, we consistently find
T
= 304 ± 58MeV and 309 ± 64MeV for the effective temperature of the quark-gluon plasma (or hot medium) at
p
T
∈ 0
.
8; 2
.
2 GeV and
p
T
∈ 1
.
5; 3
.
5 GeV as well as a power-law (
) behavior for
p
T
>
4 GeV as predicted by QCD hard scattering.
We present a calculation of the elliptic flow of electrons from beauty-hadron decays in semi-central Pb–Pb collisions at centre-of-mass energy per colliding nucleon pair, represented as
s
NN
, of ...2.76 TeV. The result is obtained by the subtraction of the charm-quark contribution in the elliptic flow of electrons from heavy-flavour hadron decays in semi-central Pb–Pb collisions at
s
NN
=
2.76
TeV
recently made publicly available by the ALICE collaboration.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present a systematic theoretical analysis of the ALICE measurement of low-pT direct-photon production in central lead-lead collisions at the LHC with a centre-of-mass energy of sNN=2.76 TeV. Using ...next-to-leading order of perturbative QCD, we compute the relative contributions to prompt-photon production from different initial and final states and the theoretical uncertainties coming from independent variations of the renormalisation and factorisation scales, the nuclear parton densities and the fragmentation functions. Based on different fits to the unsubtracted and prompt-photon subtracted ALICE data, we consistently find an exponential, possibly thermal, photon spectrum from the quark-gluon plasma (or hot medium) with slope T=304±58 MeV and 309±64 MeV at pT∈0.8;2.2 GeV and pT∈1.5;3.5 GeV as well as a power-law (pT−4) behavior for pT>4 GeV as predicted by QCD hard scattering.
PDF
