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Paper proposal: Observation of global spin alignment of K*0 vector mesons in Au+Au collisions using the STAR detector at RHIC

Updated on Thu, 2022-06-09 01:01. Originally created by subhash on 2020-06-17 03:34.

 


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The K* spin alignment paper is being combined with phi meson spin alignment:
https://drupal.star.bnl.gov/STAR/blog/sunxuhit/phi-meson-global-spin-alignment-paper-proposal-webpage
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K* Analysis Note:
1. AnalysisNote_ver7.pdf (Latest version)

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NOTE: The results in the following older versions (version1 to 4) of analysis note has self-correlation bug.
The erratum on K* analysis note is here: Eratum_Note.pdf
FCV PWG Presentation: FCV_Kstar_Spin_Align_Subhash_June_2021.pdf

2. AnalysisNote_ver4.pdf 
3. version-3c:AnalysisNote_ver3c.pdf
4. version-3: AnalysisNote_ver3.pdf 
5. version-2c: AnalysisNote_ver2c.pdf 
6. version-2b: AnalysisNote_ver2b.pdf 
7. version-2a: AnalysisNote_ver2a.pdf 

7. version-2: AnalysisNote_ver2.pdf (Released to GPC 1st round)
8. version-1: https://drupal.star.bnl.gov/STAR/system/files/AnalysisNote_ver1.pdf (AT PWGC)


Comments from Nature: Google doc

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 Title: Observation of global spin alignment of K*0 vector mesons in Au+Au collisions using the STAR detector at RHIC

PAs: Subhash Singha, Declan Keane

Target journal: Phys. Rev. Lett / Phys. Lett. B (merged with phi mesons for Nature)

Abstract:

We report global spin alignment (ρ00) for K∗0 vector mesons near mid-rapidity (|y| < 0.5) in Au+Au collisions at √sNN = 11.5 – 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). Results include the dependence of ρ00 on transverse momentum, collision centrality and beam energy. At low pT (pT < 1.5 GeV/c) and in mid-central collisions (20-60%), the K∗0 ρ00 is found to be smaller than 1/3 with a significance of 2.6 - 3.8 σ across seven beam energies. The deviation of ρ00 is qualitatively consistent with the presence of polarized quarks and subsequent hadronization by a coalescence mechanism. We observe a monotonic increase in the deviation of K∗0 ρ00 from 1/3 with decreasing beam energy. In contrast, ρ00 for another vector meson, φ, is observed to be larger than 1/3, but with a qualitatively similar monotonic increase in deviation with decreasing beam energy. These data pose a challenge to the current theoretical understanding and offer new insights on the spin dynamics of the QCD medium 

Proposed Figures::
Fig. 1:
https://drupal.star.bnl.gov/STAR/system/files/Fig1_fourPanel_PWGC_ver1.pdf

Fig. 2:
https://drupal.star.bnl.gov/STAR/system/files/KStar_Rho00_Cent_BES_wRndm_PWGC.pdf


Fig. 3:
https://drupal.star.bnl.gov/STAR/system/files/KStar_Rho00_pT_allsNN_PWGC_0.pdf

Fig. 4: 
https://drupal.star.bnl.gov/STAR/system/files/Rho00_vs_sNN_wFit_wALICE_wPhiFlipped_PWGC_ver1.pdf



Summary:

In summary, we present the first evidence of global spin alignment of K∗0 vector meson near mid-rapidity (|y| < 0.5) in Au + Au collisions at √sNN = 11.5 – 200 GeV at RHIC. In these mid-central collisions at pT < 1.5 GeV/c, the ρ00 is smaller than 1/3 with significance within 2.6 - 3.8σ across seven beam energies. The deviation increases monotonically with the decrease in beam energy, and is qualitatively consistent with a theoretical picture in which polarized quarks are present in the initial stages of the collision process, with subsequent hadronization by the coalescence mechanism.  Theory indicates that the vector meson ρ00 can depend on multiple physics scenarios: initial conditions (e.g., angular momentum, electro-magnetic field), vorticity, vector meson field, mechanism of hadronization and late stage hadronic re-scattering. Quantitative agreement between models and and the present results is substantially lacking so far. In contrast to the current K*0 measurements, the global spin alignment ρ00 for φ vector meson is observed to be larger than 1/3,  while there is a striking similarity in the monotonic increase of deviation of ρ00 for φ  with decreasing beam-energy. The difference between K∗0 and φ may be attributed to different in-medium interactions due to the factor of ten difference in lifetime, or due to different responses to the vector meson field. The measurements presented here pose a significant challenge to the current understanding of spin polarization in heavy-ion collisions and will facilitate new theoretical developments related to spin dynamics of the QCD medium.


Analysis Note:
1. version-1: https://drupal.star.bnl.gov/STAR/system/files/AnalysisNote_ver1.pdf
2. version-2: AnalysisNote_ver2.pdf (Latest version)

Paper draft: (outdated, draft is now merged with phi mesons)
Overleaf link : https://www.overleaf.com/read/jqdfywkknsyf
1. version-1: https://drupal.star.bnl.gov/STAR/system/files/draft_Kstar_alignment_ver1.pdf

PWGC preview presentation:
https://drupal.star.bnl.gov/STAR/system/files/Paper_proposal_PWGC_ver2.pdf 
 


Supporting documents:
Presentations within STAR collaboration:
1. https://www.star.bnl.gov/protected/bulkcorr/subhash/rsn/spin/ForQM/Status_Kstar_Rho00_BES.pdf
2. https://www.star.bnl.gov/protected/bulkcorr/subhash/rsn/spin/ForQM/Status_Kstar_Rho00_BES_BulkCorr_25April.pdf
3. https://drupal.star.bnl.gov/STAR/system/files/KStar_SpinAlign_BulkCorr_12Jun_2019.pdf
4. https://drupal.star.bnl.gov/STAR/system/files/KStar_SpinAlign_BulkCorr_2Oct_2019.pdf
5. https://drupal.star.bnl.gov/STAR/system/files/KStar_SpinAlign_BulkCorr_09Oct_2019.pdf
6. https://drupal.star.bnl.gov/STAR/system/files/KStar_SpinAlign_QM2019_ver3_1.pdf
7. https://drupal.star.bnl.gov/STAR/system/files/KStar_SpinAlign_QM2019_ver5_0.pdf
8. https://drupal.star.bnl.gov/STAR/system/files/KStar_Spin_BES_STARCollab_Mar2020_SINGHA.pdf
9 https://drupal.star.bnl.gov/STAR/system/files/KStar_Spin_Align_BulkCorr_Update_May20_2020.pdf

Quark Matter presentation and proceedings:
QM-18 presentation:
https://indico.cern.ch/event/656452/contributions/2869774/attachments/1650217/2638893/chensheng_qm2018.pdf
QM-19 presentation: 
https://indico.cern.ch/event/792436/contributions/3535685/attachments/1939114/3214562/KStar_SpinAlign_QM2019_final_SINGHA.pdf
QM-19 proceedings: 
https://arxiv.org/abs/2002.07427

K* and phi spin alignment paper webpage 2005 :
https://www.star.bnl.gov/protected/spectra/jhchen/phi200/spin/data/Proposal/Vector-mesons-Spin-Alignment-Proposal.htm

 

 
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