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Measurement of psi(2S) production in Ru+Ru and Zr+Zr collisions at 200 GeV

Updated on Fri, 2024-03-29 04:10. Originally created by wy157543 on 2024-03-29 03:18.

Measurement of psi(2S) production in Ru+Ru and Zr+Zr collisions at √sNN = 200 GeV with STAR experiment

PAs: Rongrong Ma, Kaifeng Shen, Zebo Tang,Yan Wang, Qian Yang, Wangmei Zha

Target Journal: Phys. Rev. Lett.

Abstract:

We report on measurements of charmonium sequential suppression in Ru+Ru and Zr+Zr collisions at √sNN  with the STAR detector at the Relativistic Heavy Ion Collider (RHIC) via the dielectron channel. The inclusive psi(2S) to J/psi yield ratio is reported as a function of collision centrality and transverse momentum. The results are compared with the corresponding measurements in p+p and p+A collisions. In the 0-80% centrality class, the inclusive psi(2S) to J/psi double ratio is significantly lower than one at a significance level of 5.7 standard deviations. This provides experimental evidence that the psi(2S) is significantly more suppressed than the J/psi at RHIC. These measurements are compared with those observed at the Large Hadron Collider or Super Proton Synchrotron.  

Figures:

 

Fig.1
Figure 1. Invariant mass distributions of psi(2S) and J/psi candidates for pT < 8.0 GeV/c reconstructed via the di-electron channel within |y| < 1. The black open circles are unlike sign from same event. Combinatorial background from like-sign and mix-event are shown as full and open triangle, respectively. Solid black lines are fitted to the black full circles, di-electron signal with the combinatorial background subtracted, while lines of other styles represent individual components included in the fit. The signal shape from embedding with additional momentum smearing is used to describe the psi(2S) and J/psi signal shape.

 

Fig.2
Figure 2. psi(2S) and J/psi significance as a function of BDT cut. The black full circles are true psi(2S) and J/psi significance. The solid black lines represent the expected significance which is based on BDT output distribution and initial data shown as black open squares.

 

Fig.3
Figure 3. Inclusive psi(2S) to J/psi double ratio as a function of Npart. For measurements from heavy-ion collisions, the error bars indicate statistical uncertainties, while the boxes denote systematic uncertainties. Other results only display total errors. First observation of charmonium sequential suppression in heavy ion collisions at RHIC (5.7sigma, 0-80%). psi(2S) over J/psi double ratio is smaller than that in p+A collisions. Hint of double ratio decreases towards central collisions. The trend of the double ratio seems more akin to SPS measurements than that at the LHC.

 

Fig.4
Figure 4. pT dependence of the psi(2S) to J/psi yield ratio in p+p, p+A, and A+A collisions. The bar and box indicate the statistical and systematic uncertainty, respectively. Hint of increasing trend with pT in isobaric collisions. Significantly lower than that in p+p and p+A collisions at pT < 2 GeV/c.

 

Summary:

   In summary, we report the first measurements of psi(2S) production in Ru+Ru and Zr+Zr collisions at √sNN = 200 GeV with the STAR detector at RHIC.

  • The results integrated over centrality and pT are consistent with the sequential suppression pattern at a significance level of 5.4 standard deviations, namely that the psi(2S) is significantly more suppressed than the J/psi.
  • The double ratio is smaller than that in p+A collisions and shows a hint of decreasing trend from peripheral to central collisions.
  • A hint of increasing trend with pT is observed for the inclusive psi(2S) to J/psi yield ratio.
  • The yield ratio significantly lower than that in p+p and p+A collisions at pT < 2 GeV/c with a significance level of 3.7 standard deviations.

Related presentations:

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

  • https://drupal.star.bnl.gov/STAR/system/files/psi2s%20raw%20yield%20in%20isobar%20collisions_0.pdf
  • https://drupal.star.bnl.gov/STAR/system/files/psi%282s%29_embedding_requst_v3.pdf
  • https://drupal.star.bnl.gov/STAR/system/files/psi%282s%29_analysis_pwg_v2.pdf
  • https://drupal.star.bnl.gov/STAR/system/files/psi%282s%29_analysis_preliminary_v2_0.pdf
  • https://drupal.star.bnl.gov/STAR/system/files/psi2s_pp_pA_ref_v1_0.pdf
  • https://drupal.star.bnl.gov/STAR/system/files/PWG_20240314_Yan.pdf
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