Measurements of inclusive D⁰-meson production in Ru+Ru and Zr+Zr collisions at √s_NN = 200 GeV

PAs: Yuan Su, Yifei Zhang, Xiaolong Chen

Target Journal: European Physical Journal C (EPJ C)

Abstract:

We report the first measurements of D⁰-meson production at mid-rapidity (|y| < 1) in isobar collisions (⁹⁶Ru+⁹⁶Ru and ⁹⁶Zr+⁹⁶Zr) at √s_NN = 200 GeV with the STAR experiment. D⁰ p_T differential invariant yield with transverse momentum p_T < 8 GeV/c are reported in 0-10%, 10-40% and 40-80% centrality. The D⁰ production cross section follows the number of binary collisions scaling within systematic uncertainties between isobar and Au+Au collisions at 200 GeV. The strong suppression D⁰ nuclear modification factor R_AA is also observed for p_T > 3 GeV/c in the central isobar collisions, demonstrating that charm quarks suffer significant energy loss in the bulk QCD medium. And model calculations reproduce the feature of R_AA measured at 200 GeV.

GPC:

Chairperson: Daniel Kikola

Member(s) at large: Guannan Xie

Member for English/Grammar QA: Helen Caines

Member for Code QA: Diptanil Roy

PWG representative: Isaac Mooney

PA representative(s): Yuan Su

1st GPC meetings:

Wednesday, Jul 31, 2024 09:00 EST

Zoom Meeting ID: 617 6534 2307

GPC v1 comments: https://drupal.star.bnl.gov/STAR/system/files/1st_GPC_response_D0_RAA_isobar.pdf

2nd GPC meetings:

Wednesday, Oct 16, 2024 09:00 EST

Zoom Meeting ID: 637 6850 5612

GPC v2 comments: https://drupal.star.bnl.gov/STAR/system/files/GPC_3_RAA_Npart_check.pdf

Paper draft:

• https://drupal.star.bnl.gov/STAR/system/files/European%20Physical%20Journal%20C%20%28EPJ%20C%29%2020241205.pdf (---New---)

• https://drupal.star.bnl.gov/STAR/system/files/diff_24.pdf

• https://drupal.star.bnl.gov/STAR/system/files/European_Physical_Journal_C__EPJ_C__20240825.pdf

• https://drupal.star.bnl.gov/STAR/system/files/European_Physical_Journal_C__EPJ_C__05162024.pdf

Comments on previous drafts:

Yi: https://drupal.star.bnl.gov/STAR/system/files/PWC_response_Yi.pdf

Isaac: https://drupal.star.bnl.gov/STAR/system/files/PWC_response_Isaac.pdf

Nihar: https://drupal.star.bnl.gov/STAR/system/files/PWC_response_Nihar.pdf

Paper code directory:

https://www.star.bnl.gov/cgi-bin/protected/viewvc.cgi/cvsroot/offline/paper/psn0835/

Analysis note:

• https://drupal.star.bnl.gov/STAR/system/files/D0_RAA_in_Isobar_Ana_Note_20240825.pdf (---New---)

• https://drupal.star.bnl.gov/STAR/system/files/D0_RAA_in_Isobar_Ana_Note_0.pdf

Paper proposal talk:

https://drupal.star.bnl.gov/STAR/system/files/Paper_Proposal_04192023.pdf

Figures:

Figure 1. The K, π invariant mass distribution with centrality 0-80% and pT range 0-8 GeV/c at mid-rapidity. In figure (a), the black solid circles depict the unlike-sign distribution under the same event, the red line shows that the mix-event method can well reproduce the combination background and the open blue circles represent the invariant mass distribution after removing the combination background. In figure (b), a Gaussian and quadratic polynomial combination function fitting (blue dash line) is applied to extract D0 raw yield. The signal significance is 28.9 for pT range 0-8 GeV/c within 0-80% centrality.

Figure 2. D0 signal at 0-10% (a), 10-40% (b), 40-80% (c) centrality with transverse momentum range 0-8 GeV/c at mid-rapidity. On the top panel, the solid points show the invariant mass distribution after removing the combination background, and the red line represents a Gaussian and quadratic polynomial combination function fitting. On the bottom panel, the solid points show the D0 signal after the redundant background is removed, and the red line is a Gaussian function fitting to the signal.

Figure 3. D0 invariant yields at mid-rapidity (|y|<1) as a function of pT at 0-10% (black solid circles), 10-40% (red solid squares) and 40-80% (blue solid rhombi) centrality classes in isobar collisions on panel (a). The hollow markers are the result of Au + Au collisions at 200 GeV, which is scaled by a same constant and the ratio of the number of binary collisions between isobar and Au + Au. Levy fits are indicated by the dotted lines. The solid green lines show the p + p reference scaled with the number of binary collisions in isobar system. Panel (b), (c) and (d) respectively show the ratio of data and fitting results at 0-10%,10-40% and 40-80% centrality.

Figure 4. D0 integrated cross section per nucleon-nucleon collision for pT > 0 (top) and pT > 4 GeV/c (bottom) as a function of ⟨Npart⟩. Solid and hollow circles represent isobar and Au + Au collisions, respectively. The error bars represent the statistical uncertainties. The boxes represent the systematic uncertainties.

Figure 5. D0 RAA for 0-10% (top), 10-40% (medium) and 40-80% (bottom) centrality bins in isobar collisions. rhombi are D0 RAA in Au + Au collisions at 200 GeV. The light and dark green boxes on the right depict the normalization uncertainties in determining the Nbin in Au + Au collisions and the total inelastic cross section in p + p collisions, respectively. The dot-dashed lines are model results for isobar collsions.

Figure 6. D0 RAA as a function of ⟨Npart⟩ in isobar collisions (solid circles) and Au + Au collisions (open circles) at 200 GeV. Top and bottom panel are the results of pT > 0 and pT > 4 GeV/c, respectively. The light green boxes on the right depict the normalization uncertainties in determining the Nbin in Au + Au collisions. The blue boxes on the right depict the total uncertainty of inelastic cross section in p + p collisions.

Figure 7. D0 Rcp with the 40-80% spectrum as the reference for 0-10% (a) and 10-40% (b) in isobar collisions at √sNN = 200 GeV compared to corresponding results in Au + Au collisions at 200 GeV. The statistical and systematic uncertainties are shown as error bars and brackets on the data points.

Figure 8. D0 invariant yield at mid-rapidity (|y| < 1) are fitted by mT exponential function for different centrality classes in isobar collisions at √sNN = 200 GeV. The statistical and systematic uncertainties are shown as error bars and brackets on the data points.

Figure 9. Inverse slope parameter Teff obtained from fitting as a function of hadron mass in isobar central collisions (solid red star) and Au + Au central collisions.

Figure 10. The BW fitting (solid lines) and the TBW fitting (dash lines) to D0 transverse momentum distributions at various centrality (left). The red solid circles shows D0 Tkin and < β > from BW fitting in isobar collisions (right). And the results of light (open circles), multi-strangeness (pink rhombi), and heavy (blue triangles) flavor hadrons in Au + Au central collisions at 200 GeV are also presented simultaneously.

 

Summary:

    In summary, we report on measurements of D⁰ meson production in isobar collisions at √s_NN = 200 GeV with the STAR detector at RHIC.

• D⁰-meson productions are firstly measured at mid-rapidity (|y| < 1) in isobar collisions.

• N_bin-scale effect of the D⁰ p_T spectra between isobar and Au + Au collision within uncertainties is firstly observed.

• The strong suppression D⁰ nuclear modification factor R_AA is also observed for p_T > 3 GeV/c in the central isobar collisions.

• No significant systematic dependence of D⁰ kinetic freeze-out properties in central collisions between isobar and Au + Au collisions within uncertainties is observed.

Related presentations:

    Here is a summary of links about related presentations on pwg meeting.

• https://drupal.star.bnl.gov/STAR/system/files/pre_QM_2023_YuanSu.pdf (---New---) 

• https://drupal.star.bnl.gov/STAR/system/files/STAR_Collaboration_Meeting_Spring_2023_Yuan_Su.pdf

• https://drupal.star.bnl.gov/STAR/system/files/Paper_Proposal_11172022_v2.pdf

• https://drupal.star.bnl.gov/STAR/system/files/D0_analysis_isobar.pdf

• https://drupal.star.bnl.gov/STAR/system/files/D0_issues_check_07212022.pdf

• https://drupal.star.bnl.gov/STAR/system/files/D0_production_07142022_YuanSu.pdf

• https://drupal.star.bnl.gov/STAR/system/files/D0_Raa_05262022_0.pdf