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Disentangling Centrality Bias and Final-State Effects in the Production of High- pT Neutral Pions Using Direct Photon in d+Au Collisions at sNN =200 GeV

Abdulameer, N.J. ; Oskarsson, A. LU ; Silvermyr, D. LU orcid and Zou, L. (2025) In Physical Review Letters 134(2).
Abstract
PHENIX presents a simultaneous measurement of the production of direct γ and π0 in d+Au collisions at sNN=200 GeV over a pT range of 7.5 to 18 GeV/c for different event samples selected by event activity, i.e., charged-particle multiplicity detected at forward rapidity. Direct-photon yields are used to empirically estimate the contribution of hard-scattering processes in the different event samples. Using this estimate, the average nuclear-modification factor, RdAu,EXPπ0, is 0.925±0.023(stat)±0.15(scale), consistent with unity for minimum-bias (MB) d+Au collisions. For event classes with low and moderate event activity, RdAu,EXPπ0 is consistent with the MB value within 5% uncertainty. This result confirms that the previously observed... (More)
PHENIX presents a simultaneous measurement of the production of direct γ and π0 in d+Au collisions at sNN=200 GeV over a pT range of 7.5 to 18 GeV/c for different event samples selected by event activity, i.e., charged-particle multiplicity detected at forward rapidity. Direct-photon yields are used to empirically estimate the contribution of hard-scattering processes in the different event samples. Using this estimate, the average nuclear-modification factor, RdAu,EXPπ0, is 0.925±0.023(stat)±0.15(scale), consistent with unity for minimum-bias (MB) d+Au collisions. For event classes with low and moderate event activity, RdAu,EXPπ0 is consistent with the MB value within 5% uncertainty. This result confirms that the previously observed enhancement of high-pT π0 production found in small-system collisions with low event activity is a result of a bias in interpreting event activity within the Glauber framework. In contrast, for the top 5% of events with the highest event activity, RdAu,EXPπ0 is suppressed by 20% relative to the MB value with a significance of 4.5σ, which may be due to final-state effects. This suppression corresponds to a pT shift of δpT=0.213±0.055 Gev/c at 9 Gev/c. © 2025 American Physical Society. (Less)
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Contribution to journal
publication status
published
subject
keywords
Atomic beams, Colliding beam accelerators, Germanium compounds, Hadrons, Linear accelerators, Negative ions, Positive ions, Proportional counters, Charged particle multiplicities, Direct photons, Final-state effects, Forward rapidity, Measurements of, Neutral pions, Nuclear modification factors, Photon yield, Scattering process, Simultaneous measurement, Photons
in
Physical Review Letters
volume
134
issue
2
article number
022302
publisher
American Physical Society
external identifiers
  • scopus:85215390612
  • pmid:39913799
ISSN
0031-9007
DOI
10.1103/PhysRevLett.134.022302
language
English
LU publication?
yes
id
aa85e178-449d-4862-bc7a-6142846f2442
date added to LUP
2025-12-16 15:32:56
date last changed
2025-12-17 03:00:04
@article{aa85e178-449d-4862-bc7a-6142846f2442,
  abstract     = {{PHENIX presents a simultaneous measurement of the production of direct γ and π0 in d+Au collisions at sNN=200 GeV over a pT range of 7.5 to 18 GeV/c for different event samples selected by event activity, i.e., charged-particle multiplicity detected at forward rapidity. Direct-photon yields are used to empirically estimate the contribution of hard-scattering processes in the different event samples. Using this estimate, the average nuclear-modification factor, RdAu,EXPπ0, is 0.925±0.023(stat)±0.15(scale), consistent with unity for minimum-bias (MB) d+Au collisions. For event classes with low and moderate event activity, RdAu,EXPπ0 is consistent with the MB value within 5% uncertainty. This result confirms that the previously observed enhancement of high-pT π0 production found in small-system collisions with low event activity is a result of a bias in interpreting event activity within the Glauber framework. In contrast, for the top 5% of events with the highest event activity, RdAu,EXPπ0 is suppressed by 20% relative to the MB value with a significance of 4.5σ, which may be due to final-state effects. This suppression corresponds to a pT shift of δpT=0.213±0.055 Gev/c at 9 Gev/c. © 2025 American Physical Society.}},
  author       = {{Abdulameer, N.J. and Oskarsson, A. and Silvermyr, D. and Zou, L.}},
  issn         = {{0031-9007}},
  keywords     = {{Atomic beams; Colliding beam accelerators; Germanium compounds; Hadrons; Linear accelerators; Negative ions; Positive ions; Proportional counters; Charged particle multiplicities; Direct photons; Final-state effects; Forward rapidity; Measurements of; Neutral pions; Nuclear modification factors; Photon yield; Scattering process; Simultaneous measurement; Photons}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Letters}},
  title        = {{Disentangling Centrality Bias and Final-State Effects in the Production of High- pT Neutral Pions Using Direct Photon in d+Au Collisions at sNN =200 GeV}},
  url          = {{http://dx.doi.org/10.1103/PhysRevLett.134.022302}},
  doi          = {{10.1103/PhysRevLett.134.022302}},
  volume       = {{134}},
  year         = {{2025}},
}