We report the first predictions of elliptic flow (<math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math>) of identified hadrons at mid-rapidity (<math><mo>|</mo><mi>y</mi><mo>|</mo><mo>&lt;</mo></math> 1.0) in Au+Au collisions at <math><msub><mrow><mi>E</mi></mrow><mrow><mi>l</mi><mi>a</mi><mi>b</mi></mrow></msub><mo>=</mo><mn>6.7</mn><mo>,</mo><mspace width="0.25em"></mspace><mn>8</mn><mo>,</mo><mspace width="0.25em"></mspace><mn>11</mn><mo>,</mo><mspace width="0.25em"></mspace><mrow><mi>and 25 A GeV</mi></mrow></math> using the Parton Hadron String Dynamics (PHSD) model. The transverse momentum (<math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math>) dependence of identified hadron <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math> in different centrality intervals (0-10%, 10-40%, and 40-80%) is shown. A clear centrality dependence of <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>)</mo></math> is observed for particles at <math><msub><mrow><mi>E</mi></mrow><mrow><mi>l</mi><mi>a</mi><mi>b</mi></mrow></msub><mo>=</mo><mn>6.7</mn><mo>,</mo><mspace width="0.25em"></mspace><mn>8</mn><mo>,</mo><mspace width="0.25em"></mspace><mn>11</mn><mo>,</mo><mspace width="0.25em"></mspace><mrow><mi>and 25 A GeV</mi></mrow></math>. Within the PHSD model, the number of constituent quark (NCQ) scaling of <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math> approximately follows in Au+Au collisions at all beam energies. A collision energy (<math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt></math>) dependence of π, K, and p <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math> is studied in comparison with available published experimental data in the beam energy range of 6-25 A GeV. These predictions will help in interpreting the data from the forthcoming Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR) and Multi-Purpose Detector (MPD) at the Nuclotron-based Ion Collider facility (NICA).

India

Towseef Bhat

M. Farooq Mir

Chile

Vipul Bairathi

Waseem Bhat

Sonia Kabana

Shabir Bhat

Collision energy dependence of elliptic flow of identified hadrons in heavy-ion collisions using the PHSD model

Observables in heavy-ion collisions are generally categorized into centralities, which reflect an average over events within a range of impact parameters including a wide variety of initial-state configurations. A multiple binning method using spectator neutrons within each centrality has been shown to provide access to events with rare initial-state conditions. This work suggests an improvement in quantifying the difference between standard centrality and spectator neutron binning towards accessing the initial-state properties. A selection of events with higher initial-state density at a fixed participating nucleon number was observed to result in larger final-state particle production and smaller elliptic flow. The relative difference between observables in centrality and spectator binning shows reduced sensitivity for the observables dominated by impact parameter fluctuations in the initial state, such as triangular flow. This property renders the spectator binning method a good candidate for separating geometric contributions from random fluctuations in the initial state towards final-state observables.

United States

Somadutta Bhatta

An improved method to access initial states in relativistic heavy-ion collisions

There is event by event geometric as well as quantum fluctuations in the initial condition of heavy-ion collisions. The standard technique of analysing heavy-ion collisions in bins of centrality obtained from final state multiplicity averages out the various initial configurations and thus restricts the study to only a limited range of initial conditions. In this paper, we propose an additional binning in terms of total spectator neutrons in an event. This offers us a key control parameter to probe events with broader range of initial conditions providing us an opportunity to peep into events with rarer initial conditions which otherwise get masked when analysed by centrality binning alone. We find that the inclusion of spectator binning allows one to vary ε2 and ε3 independently. We observe that the standard scaling relation between v2/ε2 and 1SdNchdη exhibited by centrality bins is strongly broken by the spectator neutron bins. Further, the acoustic scaling relation between ln⁡(vn/εn) and transverse system size is also broken- the strength of the breaking being sensitive to the binning procedure. The introduction of the spectator binning allows us to tune over a wide range viscosity driven effects for events with varying initial states but similar final state multiplicity.

Sandeep Chatterjee

Md. Rihan Haque

Bedangadas Mohanty

Probing Pb + Pb collisions at SNN=2760Â GeV with spectators

The main aim of the relativistic heavy-ion experiment is to create extremely hot and dense matter and study the QCD phase structure. With this motivation, experimental program started in the early 1990s at the Brookhaven Alternating Gradient Synchrotron (AGS) and the CERN Super Proton Synchrotron (SPS) followed by Relativistic Heavy Ion Collider (RHIC) at Brookhaven and recently at Large Hadron Collider (LHC) at CERN. These experiments allowed us to study the QCD matter from center-of-mass energies (<math id="M1"><mrow><msqrt><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></mrow></math>) 4.75 GeV to 2.76 TeV. The ϕ meson, due to its unique properties, is considered as a good probe to study the QCD matter created in relativistic collisions. In this paper we present a review on the measurements of ϕ meson production in heavy-ion experiments. Mainly, we discuss the energy dependence of ϕ meson invariant yield and the production mechanism, strangeness enhancement, parton energy loss, and partonic collectivity in nucleus-nucleus collisions. Effect of later stage hadronic rescattering on elliptic flow (<math id="M2"><mrow><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math>) of proton is also discussed relative to corresponding effect on ϕ meson <math id="M3"><mrow><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math>.

Md. Nasim

Mukesh Kumar Sharma

Anju Bhasin

A Review on ϕ Meson Production in Heavy-Ion Collision