Wed·Sep 17, 2014Wednesday·September 17, 2014

1. 01*

   Probing hot and dense matter production in heavy ion collisions via neutral mesons and photons with the ALICE detector at the LHC

   Astrid Morreale (for the ALICE collaboration)🇫🇷

   One of the key signatures of the Quark Gluon Plasma (QGP) is the modification of hadron and direct photon spectra in heavy-ion collisions as compared to proton-proton (pp) collisions. Suppression of hadron production at high transverse momenta in heavy-ion collisions can be explained by the energy loss of the partons produced in the hard scattering processes which traverse the hot and dense QCD matter. The dependence of the observed suppression on the transverse momentum (pT) of the measured hadron towards higher pT is an important input for the theoretical understanding of jet quenching effects in the QGP and the nature of energy loss. Another key observable which has helped establish the energy loss picture, is high pT direct photon production for which no suppression is expected. For low pT photon production, it is expected that thermal sources will lead to enhancement of direct photons. We report an overview of photon and neutral meson production measurements by the ALICE experiment at the LHC in heavy-ion and pp collisions.

   nucl-ex3 citations
2. 02*

   Charmonium Production at Forward Rapidity in pp, p-Pb and Pb-Pb Collisions, with ALICE

   Hugo Pereira Da Costa (for the ALICE Collaboration)🇫🇷

   This contribution focuses on latest ALICE results on charmonium forward production in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the TeV scale. In p-Pb and Pb-Pb collisions, measurements are presented in the form of the charmonium nuclear modification factor (the properly normalized ratio of its production cross section in heavy ion collisions to its pp counterpart) as a function of the charmonium rapidity and transverse momentum. These measurements are compared to available theoretical calculations. Possible interpretations of these results in terms of gluon saturation, initial and final state energy loss, color screening and recombination are also discussed.

   nucl-ex2 citations
3. 03*

   Jet Production in p-Pb Collisions

   Megan Connors (for the ALICE Collaboration)🇺🇸

   One of the major results from the study of high energy heavy ion collisions is the observation of jet quenching. The suppression of the number of jets observed in heavy ion collisions relative to pp collisions at the same energy scaled by the number of binary collisions, is attributed to partonic energy loss in the quark gluon plasma (QGP). However, cold nuclear matter effects due to the presence of a nucleus in the initial state could also influence this measurement. To disentangle these effects p-Pb collisions are studied, where QGP formation is not expected to occur and only cold nuclear matter effects are present. In addition to being an important baseline for understanding jet quenching, jets in p-Pb collisions may also be used to provide constraints on the nuclear parton distribution functions. Fully reconstructed jets measured using the ALICE tracking system and electro-magnetic calorimeter in p-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are reported. In addition to the spectra, studies of the jet fragmentation behavior in p-Pb collisions are also presented.

   nucl-ex7 citations
4. 04*

   Heavy-flavour production and multiplicity dependence in pp and p--Pb collisions with ALICE

   Elena Bruna (for the ALICE Collaboration)🇮🇹

   The production of heavy quarks in pp collisions provides a precision test of perturbative QCD calculations at the LHC energies. More complex collision systems like p--Pb collisions allow studies of cold nuclear matter effects, such as modifications of the parton distribution functions at small x and of the $\text{kt}$ broadening effect. We present the ALICE results of prompt D-meson production as a function of the charged-particle multiplicity, in pp and p--Pb collisions at $\sqrt{s}=7$ TeV and $\sqrt{s_{NN}}=5.02$ TeV respectively. The per-event yield of D mesons in different multiplicity and $\text{pt}$ intervals are compared for pp and p--Pb collisions to study the contribution of multi-parton interactions to open-charm production. Angular correlations of prompt D mesons and heavy-flavour decay electrons with charged hadrons in pp and p-Pb collisions are also shown in different kinematic ranges and compared to pQCD models. These measurements provide information on the charm fragmentation processes, on cold nuclear matter effects on charm production, and on the participation of charm in the collective motion arising in small collision systems like p-Pb.

   nucl-ex0 citations
5. 05*

   Modifications of Heavy-Flavor Spectra in $\sqrt{s_{\mathrm{NN}}}=62.4\mathrm{GeV}$ Au-Au Collisions

   Min He🇨🇳 · Rainer J. Fries🇺🇸 · Ralf Rapp🇺🇸

   We calculate open heavy-flavor (HF) production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$=62.4 GeV utilizing a nonperturbative transport approach as previously applied in nuclear collisions at top RHIC and LHC energies. The effects of hot QCD matter are treated in a strong-coupling framework, by implementing heavy-quark diffusion, hadronization and heavy-flavor meson diffusion within a hydrodynamic background evolution. Since in our approach the heavy-flavor coupling to the medium is strongest in the pseudo-critical region, it is of interest to test its consequences at lower collision energies where the sensitivity to this region should be enhanced relative to the hotter (early) fireball temperatures reached at top RHIC and LHC energies. We find that the suppression and flow pattern of the non-photonic electrons from heavy-flavor decays at 62.4 GeV emerges from an intricate interplay of thermalization and initial-state effects, in particular a Cronin enhancement which is known to become more pronounced toward lower collision energies.

   ↳ nucl-thhep-phnucl-exPRC(2015)·20 citations
6. 06*

   Pion, kaon, and proton femtoscopy in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=2.76 TeV modeled in 3+1D hydrodynamics

   Adam Kisiel🇵🇱 · Mateusz Galazyn🇵🇱 · Piotr Bozek🇵🇱

   Femtoscopy is providing information on system size and its dynamics in heavy-ion collisions. At ultra-relativistic energies, such as those obtained at the LHC, significant production of pions, kaons and protons enables femtoscopic measurements for these particles. In particular the dependence of system size on pair momentum and particle type is interpreted as evidence for strong collective flow. Such phenomena are naturally modeled by hydrodynamics. We present calculations within the 3+1D hydrodynamic model coupled to statistical hadronization code THERMINATOR 2, corresponding to Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$2.76 TeV. We obtain femtoscopic radii for pions, kaons, and protons, as a function of pair transverse momentum and collision centrality. We find that an approximate universal scaling of radii with pair transverse mass and final state event multiplicity is observed, and discuss the consequences for the interpretation of experimental measurements.

   ↳ nucl-thnucl-exPRC(2014)·65 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.