Heavy Flavor Measurements at STAR

AbstractWe present a selection of recent heavy flavor results from the STAR experiment. Measurements of D0 and D* meson production in s=200 and 500 GeV p+p, as well as in sNN=200 GeV d+Au, Au+Au and 193 GeV U+U collisions are presented and implications on the production mechanism are discussed. We report on the production and elliptic flow of electrons from semi-leptonic decays of heavy flavor hadrons in sNN=39, 62.4 and 200 GeV Au+Au collisions. Nuclear modification of J/ψ production in sNN=39, 62.4 and 200 GeV Au+Au, and 193 GeV U+U, and of ϒ in 200 GeV d+Au, Au+Au, and 193 GeV U+U collisions are compared to theoretical models. Finally we discuss the prospects of heavy flavor measurements with the recent detector upgrades

Multiplicity Dependence of the Jet Structures in pp Collisions at LHC Energies

We study the event multiplicity dependence of the jet structure in pp collisions. We present evidence for jet shape modification due to multi-parton interactions using PYTHIA and HIJING++ Monte Carlo (MC) event generators as an input to our analysis. We introduce a characteristic jet size measure which is independent of the choice of the simulation parameters, parton distribution functions, jet reconstruction algorithms and even of the presence or absence of multi-parton interactions. We also investigate heavy-flavor jets and show the sensitivity of the multiplicity-differential jet structure to flavor-dependent fragmentation.Comment: Presented at Hot Quarks 2018 -- Workshop for young scientists on the physics of ultrarelativistic nucleus-nucleus collisions, Texel, The Netherlands, September 7-14 2018. Submitted to MDPI Proceeding

Latest results on Upsilon production in heavy-ion collisions from the STAR experiment

We report on the latest measurements of the production of Upsilon mesons in heavy-ion collisions from the STAR experiment at RHIC. New measurements of the nuclear modification factors of the Upsilon(1S+2S+3S) and Upsilon(1S) states in U+U collisions at sqrt{s_{NN}}=193 GeV are presented as a function of the number of participants (N(part)) in the collisions. In addition, the suppression of Upsilon(1S) and Upsilon(2S+2S) is presented versus the quark-antiquark binding energy. Preliminary results on ϒ suppression in Au+Au collisions at sqrt{s_{NN}}=200 GeV, reconstructed via the dimuon channel, are also reported

The role of the underlying event in the charm-baryon enhancement observed in pp collisions at LHC energies

We study the enhanced production of $\Lambda_c$ charmed baryons relative to that of charmed $D^0$ mesons in proton-proton collisions at LHC energies. We simulated collision events with the enhanced color-reconnection model in PYTHIA 8 MC generator and propose measurements based on the comparative use of different event-activity classifiers to identify the source of the charmed-baryon enhancement. We demonstrate that in this enhanced color-reconnection scenario the excess production is primarily linked to the underlying event and not to the production of high-momentum jets

Event-activity dependent production of strange and non-strange charmed baryons in the enhanced color-reconnection scheme

We investigated the production of charmed baryons with different isospin and strangeness content, compared to both charmed $D^0$ mesons and to the $\Lambda_c^+$ baryon in proton--proton collisions at LHC energies. We used the PYTHIA 8 Monte Carlo event generator with color-reconnection beyond leading color approximation and proposed methods based on event-activity classifiers to probe the source of the charm baryon enhancement. We conclude that in the considered model class, the isospin of the charmed baryon state has a strong impact on the enhancement pattern. Using the observables we propose, upcoming high-precision experimental data will be able to differentiate between mechanisms of strangeness and charm enhancement

Correlation of Heavy and Light Flavors in Simulations

The ALICE experiment at the Large Hadron Collider (LHC) ring is designed to study the strongly interacting matter at extreme energy densities created in high-energy heavy-ion collisions. In this paper we investigate correlations of heavy and light flavors in simulations at LHC energies at mid-rapidity, with the primary purpose of proposing experimental applications of these methods. Our studies have shown that investigating the correlation images can aid the experimental separation of heavy quarks and help understanding the physics that create them. The shape of the correlation peaks can be used to separate the electrons stemming from b quarks. This could be a method of identification that, combined with identification in silicon vertex detectors, may provide much better sample purity for examining the secondary vertex shift. Based on a correlation picture it is also possible to distinguish between prompt and late contributions to D meson yields

Modification of jet structure in high-multiplicity pp collisions due to multiple-parton interactions and observing a multiplicity-independent characteristic jet size

We study the multiplicity dependence of jet structures in pp collisions using Monte Carlo event generators. We give predictions for multiplicity-differential jet structures and present evidence for a nontrivial jet shape dependence on charged hadron event multiplicity that can be used as a sensitive tool to experimentally differentiate between equally well-preforming simulation tunes. We also propose a way to validate the presence and extent of effects such as multiple-parton interactions (MPI) or color reconnection (CR), based on the detection of nontrivial jet shape modification in high-multiplicity events at high pT. Using multiplicity-dependent jet structure observables in various pT windows might also help understanding the interplay between jet particles and the underlying event (UE). We introduce a multiplicity-independent characteristic jet size measure and use a simplistic model to aid its physical interpretation

Multicopy metrology with many-particle quantum states

We consider quantum metrology with several copies of bipartite and multipartite quantum states. We characterize the metrological usefulness by determining how much the state outperforms separable states. We identify a large class of entangled states that become maximally useful for metrology in the limit of infinite number of copies. The maximally achievable metrological usefulness is attained exponentially fast in the number of copies. We show that, on the other hand, pure entangled states with even a small amount of white noise do not become maximally useful even in the limit of infinite number of copies. We also make general statements about the usefulness of a single copy of pure entangled states. We show that the multiqubit states presented in Hyllus et al. [Phys. Rev. A 82, 012337 (2010)], which are not useful, become useful if we embed the qubits locally in qutrits. We discuss the relation of our scheme to error correction, and possible use for quantum information processing in a noisy environment.Comment: 7 pages including 3 figures + 5-page supplement including 2 figures, revtex4.

Activation of metrologically useful genuine multipartite entanglement

We consider quantum metrology with several copies of bipartite and multipartite quantum states. We characterize the metrological usefulness by determining how much the state outperforms separable states. We identify a large class of entangled states that become maximally useful for metrology in the limit of large number of copies, even if the state is weakly entangled and not even more useful than separable states. This way we activate metrologically useful genuine multipartite entanglement. Remarkably, not only that the maximally achievable metrological usefulness is attained exponentially fast in the number of copies, but it can be achieved by the measurement of few simple correlation observables. We also make general statements about the usefulness of a single copy of pure entangled states. We surprisingly find that the multiqubit states presented in Hyllus et al (2010 Phys. Rev. A 82 012337), which are not useful, become useful if we embed the qubits locally in qutrits. We discuss the relation of our scheme to error correction, and its possible use for quantum metrology in a noisy environment