Bottomonium production in heavy-ion collisions at STAR

Bottomonium measurements provide unique insight into hot and cold nuclear matter effects present in the medium that is formed in high-energy heavy-ion collisions. Recent STAR results show that in $\sqrt{s_{NN}}$ = 200 GeV central Au+Au collisions the $\Upsilon$(1S) state is suppressed more than if only cold nuclear matter effects were present, and the excited state yields are consistent with a complete suppression. In 2012, STAR also collected 263.4 $\mu$b$^{-1}$ high-energy-electron triggered data in U+U collisions at $\sqrt{s_{NN}}$= 193 GeV. Central U+U collisions, with an estimated 20% higher energy density than in central Au+Au data, extend the $\Upsilon$(1S+2S+3S) and Upsilon(1S) nuclear modification trends observed in Au+Au towards higher number of participant nucleons, and confirm the suppression of the $\Upsilon$(1S) state. We see a hint with 1.8 sigma significance that the $\Upsilon$(2S+3S) excited states are not completely suppressed in U+U collisions. These data support the sequential in-medium quarkonium dissociation picture and favor models with a strong $q\bar{q}$ binding.Comment: Proceedings of the Hard Probes International Conference 2015, Montreal, Canada. 4 pages, 5 figure

Production of Quarkonia at RHIC

The production of different quarkonium states provides unique insight to the hot and cold nuclear matter effects in the strongly interacting medium that is formed in high energy heavy ion collisions. While LHC explores the energy frontier, RHIC has a broad physics program to explore the nuclear modification at different energies in a wide range of systems. Some of the most interesting recent results on $J/\psi$ and $\Upsilon$ production in p+p, d+Au and A+A collisions from PHENIX and STAR are summarized in this work.Comment: Writeup of the talk on the "Joint Wigner-CCNU High-Energy Heavy-Ion Balaton Workshop 2015", Tihany, Hungary. To be published in the Gribov 85 memorial issue "Exploring Quantum Field Theory". 8 pages, 8 figure

Neutral pion production in Au+Au collisions at RHIC

New results from the 2010 RHIC low energy program show a substantial suppression of neutral pions in central Au+Au collisions at both sqrt{s_NN}=39 and 62.4 GeV c.m.s. energies. At high pT the 62.4 GeV and 200 GeV data follow the same suppression pattern. On the other hand, otherwise successful pQCD predictions do not describe the 39 GeV data. These observations indicate that initial state effects may play a dominant role at smaller c.m.s. energies and at lower pT . The azimuthal dependence of the nuclear modification factor R_AA is strongly correlated with the (approximately elliptical) geometry of the overlap region. The dependence of R_AA on the reaction plane, determined up to pT=20 GeV/c from 2007 high-luminosity sqrt{s_NN}=200 GeV Au+Au data provides great selectivity among theories, and favours the ASW scenario with AdS/CFT correspondence over the pQCD-based models.Comment: Accepted for the Proceedings of Hard Probe 2012, Cagliary, Italy (4 pages, 4 figures

In-medium reduction of the \eta' mass in \sqrt{s_NN} = 200 GeV Au+Au collisions

A reduction of the mass of the \eta'(958) meson may indicate the restoration of the UA(1) symmetry in a hot and dense hadronic matter, corresponding to the return of the 9th, "prodigal" Goldstone boson. We report on an analysis of a combined PHENIX and STAR data set on the intercept parameter of the two-pion Bose-Einstein correlation functions, as measuremed in \sqrt{s_NN} = 200 GeV Au+Au collisions at RHIC. To describe this combined PHENIX and STAR dataset, an in-medium \eta' mass reduction of at least 200 MeV is needed, at the 99.9 % confidence level in a broad model class of resonance multiplicities. Energy, system size and centrality dependence of the observed effect is also discussed.Comment: Proceedings of an invited talk of Robert Vertesi at the HCBM 2010 workshop, Budapest, Hungary. Proceedings of an invited talk of Tamas Csorgo at the ISMD 2010 conference, Antwerp, Belgiu

Effects of chain decays, radial flow and UA(1)U_{A}(1) restoration on the low-mass dilepton enhancement in sNN=200\sqrt{s_{NN}}=200 GeV Au+Au reactions

In sqrt(sNN) = 200 GeV Au+Au collisions PHENIX reported a significant enhancement in the low-mass region (0.1 < m_ee < 0.7 GeV) of the dielectron spectrum, which is still not fully understood. Several theoretical works and an indirect measurement suggest that, due to the possible restoration of the U_A(1) part of the chiral symmetry in a hot and dense medium, the mass of the eta' meson may substantially decrease. This work reports on a statistically acceptable description of the PHENIX low-mass dilepton enhancement using a radial flow dominated meson spectra, chain decays of long-lived resonances and an in-medium eta' mass modification

Charm and beauty production and hadronization with the ALICE experiment

This contribution summarizes a selection of recent results from the ALICE experiment. We show the cross-section of beauty jets in pp collisions, as well as the charmed baryon-to-meson production ratios, down to unprecedentedly low momenta, at $\sqrt{s_{\rm NN}} = 5.02$ and 13 TeV collision energies. We present the nuclear modification of ${\rm D}^0$-jets and the $v_2$ of non-prompt ${\rm D}^0$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. We also discuss the implications and constraints from comparing these data to some of the most recent theoretical models.Comment: submitted to Acta Physica Polonica B Proceedings Supplemen

Jet substructure measurements with ALICE

A selection of new jet substructure measurements are reported from the ALICE experiment at the CERN LHC in both proton-proton and heavy-ion collisions. These include the first fully corrected inclusive measurements of the groomed jet momentum fraction and the groomed jet radius, as well as the $N$-subjettiness distribution and the fragmentation distribution of reclustered subjets. We also report on the measurement of several groomed substructure observables of heavy-flavor jets in pp collisions, fragmentation functions and the new measurements of the radial distributions of D$^0$ mesons or $\Lambda^+_c$ baryons in jets. The measurements are compared to theoretical calculations and provide new constraints on the physics underlying parton fragmentation and jet quenching.Comment: Proceedings of the corresponding Nucleus21 talk. Submitted for publication in Physics of Particles and Nucle

Event-shape-dependent analysis of charm-anticharm azimuthal correlations in simulations

In high-energy collisions of small systems, by high-enough final-state multiplicities, a collective behaviour is present that is similar to the flow patterns observed in heavy-ion collisions. Recent studies connect this collectivity to semi-soft vacuum-QCD processes. Here we explore QCD production mechanisms using angular correlations of heavy flavour using simulated proton-proton collisions at $\sqrt{s} = 13$~TeV with the PYTHIA8 Monte Carlo event generator. We demonstrate that the event shape is strongly connected to the production mechanisms. Flattenicity, a novel event descriptor, can be used to separate events containing the final-state radiation from the rest of the events.Comment: Submitted to Universe Zimanyi School Special Issu