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Precision measurement of net-proton-number gluctuations in Au+Au collisions at RHIC

We report precision measurements on cumulants (𝐶𝑛) and factorial cumulants (𝜅𝑛) of (net) proton number distributions up to fourth order in Au+Au collisions over center-of-mass energies √𝑠𝑁⁢𝑁=7.7-27 GeV from phase II of the Beam Energy Scan program at RHIC. (Anti)protons are selected at midrapidity (...

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Bibliographic Details
Main Authors: Aboona, Bassam (Author) , Deppner, Ingo Martin (Author) , Herrmann, Norbert (Author) , Leung, Yue (Author) , Söhngen, Yannick (Author)
Corporate Author: STAR Collaboration (Author)
Format: Article (Journal)
Language:English
Published: 29 September 2025
In: Physical review letters
Year: 2025, Volume: 135, Issue: 14, Pages: 1-8
ISSN:1079-7114
DOI:10.1103/9l69-2d7p
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1103/9l69-2d7p
Verlag, lizenzpflichtig, Volltext: https://link.aps.org/doi/10.1103/9l69-2d7p
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Author Notes:STAR Collaboration*
Description
Summary:We report precision measurements on cumulants (𝐶𝑛) and factorial cumulants (𝜅𝑛) of (net) proton number distributions up to fourth order in Au+Au collisions over center-of-mass energies √𝑠𝑁⁢𝑁=7.7-27 GeV from phase II of the Beam Energy Scan program at RHIC. (Anti)protons are selected at midrapidity (|𝑦| <0.5) within a transverse momentum range of 0.4<𝑝𝑇<2.0 GeV/𝑐. Relative to various noncritical-point model calculations and peripheral collision 70%-80% data, the net proton 𝐶4/𝐶2 measurement in 0%-5% collisions shows a minimum around 19.6 GeV for significance of deviation at ∼2-5⁢𝜎. A minimum in 𝐶4/𝐶2 with respect to a noncritical baseline is expected to be a characteristic feature of the signature associated with a critical point in the QCD phase diagram. In addition, deviations from noncritical baselines around the same collision energy region are also seen in proton factorial cumulant ratios, especially in 𝜅2/𝜅1 and 𝜅3/𝜅1. Dynamical model calculations including a critical point are called for in order to understand these precision measurements.
Item Description:Veröffentlicht: 29. September 2025
*STAR Collaboration: B.E. Aboona, I.M. Deppner, N. Herrmann, Y.H. Leung, Y. Söhngen [und 367 weitere Personen]
Gesehen am 20.02.2026
Physical Description:Online Resource
ISSN:1079-7114
DOI:10.1103/9l69-2d7p

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