Paper Title :   pt Correlations in Au + Au Collisions in the High Baryon Density Region

  Target Journal : PRL

  PAs : Rutik Manikandhan, Rene Bellwied, Caleb Broodo, Aranya Giri

  PA representative :  Rutik Manikandhan

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 Abstract:

  We present two-particle pt correlations as a function of event centrality for Au+Au collisions from the STAR-FXT program at √sN N = 3.0, 3.2, 3.5, 3.9, 4.5 and 7.7 GeV. The results are compared to previous measurements from STAR BES-I, CERES at the Super Proton Synchrotron and ALICE at the Large Hadron Collider. The data are compared with UrQMD and AMPT model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. In central collisions, the (pT ) correlations show a decrease as a function of collision energy from √sN N = 3.0 GeV to 4.5 GeV and then an increase from √sN N = 7.7 GeV to 200 GeV. By further investigating this non-monotonous behaviour, we aim to deepen our understanding of how the system evolves across different energy regimes, and whether this non-monotonicity could signal the possible existence of a QCD critical point.

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 Paper Figures:

 Fig 1: The efficiency uncorrected density distribution in transverse momentum ($p_{T}$) and particle pseudorapidity ($\eta_{lab}$) in lab frame within 0-5% centrality Au+Au collisions measured with STAR TPC in Au+Au collisions ar $\sqrt{s_{NN}}$ = 
 3.0,3.2,3.5,3.9,7.7 (Fixed-Target and Collider). The dashed blue lines are midrapidity at each energy and the black window is the analysis window.Note that the density distribution is self-normalized in each panel.

  Fig. 2 : The two particle $p_{T}$ correlator as a function of collisions energy $sqrt{s_{NN}}$ in Au+Au 0-5% central collisions. Statistical and systematic uncertainties are shown as bars and gray bands, respectively. Note that for all the measurements the
  charged particles are selected within a $p_{T}$ acceptance of [0.2,2.0] GeV/c and pseudorapidity ($\eta$) acceptance of $|\eta_{cm}|$ < 0.5, where  \eta_{cm} = \eta_{lab} - \eta_{mid}. UrQMD calculations are shown in green, modified AMPT calculations are 
  shown in pink squares and thermal prediction using Boltzmann-Langevin are shown in hollow triangles.

Fig 3 : The relative dynamical correlation $\sqrt{\langle \Delta p_{t,i} \Delta p_{t,j} \rangle}/\langle \langle p_{t} \rangle \rangle$ as a function of $N_{part}$ for six collision energies. Statistical and systematic errors are shown. The solid straight lines represent a power law. All of these measurements are done within the same $p_{T}$ acceptance of [0.2,2.0] GeV/c and pseudorapidity ($\eta$) acceptance of $|\eta_{cm}|$ < 0.5, where  \eta_{cm} = \eta_{lab} - \eta_{mid}.

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Conclusions:
In summary, we presented the two point transverse momentum correlation function scaled with $\rangle}/\langle \langle p_{t} \rangle \rangle$ for all charged particles within a uniform acceptance at $\sqrt{s_{NN}}$ = 3.0, 3.2, 3.5, 3.9, 4.5 & 7.7 GeV. We observe a strong non-monotonous dependence as a function of collision energy in the 0-5 % centrality for our measurements. This non-monotonous dependence could possibly be explained by the existence of a critical point on the QCD phase diagram.

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Presentations:

Presentation at the BES-II Workshop 2024:
https://drupal.star.bnl.gov/STAR/system/files/Rutik_BES-II_WorkshopClosed.pdf
https://drupal.star.bnl.gov/STAR/system/files/Rutik_BES-II_workshop.pdf

Oral Talk at FAIRNess 2024:
https://indico.gsi.de/event/18746/contributions/82724/attachments/48699/70721/FAIRNess%202024%20%284%29.pdf

Oral Talk at CPOD 2024:
https://conferences.lbl.gov/event/1376/contributions/8802/attachments/5149/4966/Rutik_CPOD_Final.pdf

Talks at STAR Collaboration Meetings:

October 2024 : https://drupal.star.bnl.gov/STAR/system/files/STARCollaborationMeeting_0.pdf

March 2024    : https://drupal.star.bnl.gov/STAR/system/files/CollaborationMeeting32923.pdf

Presentations for Preliminary request:

3.0 GeV :
https://drupal.star.bnl.gov/STAR/system/files/Correlationsat3GeV.pdf

3.2 GeV:
https://drupal.star.bnl.gov/STAR/system/files/Preliminary.pdf