This article presents measurements of inclusive <italic>J</italic>/ <italic>&#968;</italic> production at midrapidity (| <italic>y</italic>|&#8239;&lt;&#8239; 1.0) in Au+Au collisions at <math altimg='si1.svg'><mrow><msqrt><msub><mi>s</mi><mtext>NN</mtext></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>54.4</mn></mrow></math> GeV with the STAR detector at the Relativistic Heavy Ion Collider. A suppression of the <italic>J</italic>/ <italic>&#968;</italic> yield, quantified using the nuclear modification factors ( <italic>R</italic> <inf>AA</inf>, <italic>R</italic> <inf>CP</inf>), is observed with respect to the scaled production in <math altimg='si2.svg'><mrow><mi>p</mi><mspace width='0.16em' /><mo linebreak='goodbreak'>+</mo><mspace width='0.16em' /><mi>p</mi></mrow></math> collisions. The dependence of <italic>R</italic> <inf>AA</inf> on collision centrality and <italic>J</italic>/ <italic>&#968;</italic> transverse momentum is measured with improved precision compared to previous measurements at 39 and 62.4&#8239;GeV, while the centrality dependence of <italic>R</italic> <inf>CP</inf> is measured and compared to the same results at 39, 62.4, and 200&#8239;GeV. In central collisions, no significant collision energy dependence of <italic>R</italic> <inf>AA</inf> is found within uncertainties for collision energies between 17.3 and 200&#8239;GeV. Two transport model calculations that include dissociation and regeneration contributions are consistent with the experimental results within uncertainties. Although no significant collision energy dependence of the <italic>J</italic>/ <italic>&#968;</italic> suppression in high energy heavy-ion collisions up to <math altimg='si10.svg'><mrow><msqrt><msub><mi>s</mi><mtext>NN</mtext></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>200</mn></mrow></math> GeV is observed within uncertainties, the newly measured results at 54.4&#8239;GeV Au+Au collisions provide additional constraints on theoretical calculations of the hot medium evolution and cold nuclear matter effects.

United States

B.E. Aboona

Czechia

J. Adam

Poland

L. Adamczyk

India

I. Aggarwal

M.M. Aggarwal

Z. Ahammed

A.K. Alshammri

E.C. Aschenauer

China

S. Aslam

J. Atchison

Chile

V. Bairathi

X. Bao

P. Barik

K. Barish

S. Behera

R. Bellwied

P. Bhagat

A. Bhasin

S. Bhatta

S.R. Bhosale

J. Bielcik

J. Bielcikova

J.D. Brandenburg

C. Broodo

X.Z. Cai

H. Caines

M. Calderón de la Barca Sánchez

D. Cebra

J. Ceska

I. Chakaberia

P. Chaloupka

Y.S. Chang

Z. Chang

A. Chatterjee

D. Chen

J.H. Chen

L. Chen

Q. Chen

W. Chen

Z. Chen

J. Cheng

Y. Cheng

W. Christie

X. Chu

S. Corey

H.J. Crawford

Hungary

M. Csanád

G. Dale-Gau

A. Das

D. De Souza Lemos

Germany

I.M. Deppner

A. Deshpande

A. Dhamija

A. Dimri

P. Dixit

X. Dong

J.L. Drachenberg

E. Duckworth

J.C. Dunlop

Egypt

Y.S. El-Feky

J. Engelage

G. Eppley

Japan

S. Esumi

O. Evdokimov

O. Eyser

B. Fan

Y. Fang

R. Fatemi

Italy

S. Fazio

H. Feng

Y. Feng

E. Finch

Y. Fisyak

F.A. Flor

B. Fu

C. Fu

T. Fu

C.A. Gagliardi

T. Galatyuk

T. Gao

Y. Gao

G. Garcia

F. Geurts

A. Gibson

A. Giri

K. Gopal

X. Gou

D. Grosnick

A. Gu

J. Gu

A. Gupta

A. Hamed

R.J. Hamilton

J. Han

X. Han

S. Harabasz

M.D. Harasty

J.W. Harris

H. Harrison-Smith

L.B. Havener

Measurement of inclusive <italic>J</italic>/ <italic>&#968;</italic> production in Au+Au collisions at <math altimg='si1.svg'><mrow><msqrt><msub><mi>s</mi><mtext>NN</mtext></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>54.4</mn></mrow></math> GeV at STAR

A precision measurement of the <italic>K</italic> &#8270;0 meson yield is reported in Au+Au collisions at <math altimg='si5.svg'><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>7.7</mn><mo>,</mo><mspace width='0.28em' /><mn>11.5</mn><mo>,</mo><mspace width='0.28em' /><mn>14.6</mn><mo>,</mo><mspace width='0.28em' /><mn>19.6</mn><mo>,</mo></mrow></math> and 27&#8201;GeV using the high-statistics data sample collected by the STAR experiment during the Beam Energy Scan II (BES-II) program at RHIC. The transeverse momentum ( <italic>p<inf>T</inf></italic>)-integrated yield ratios <math altimg='si6.svg'><mrow><mrow><mo>(</mo><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup><mo linebreak='badbreak'>+</mo><mover><mrow><msup><mi>K</mi><mrow><mo>*</mo><mn>0</mn></mrow></msup></mrow><mo stretchy='true'>&#8254;</mo></mover><mo>)</mo></mrow><mo linebreak='goodbreak'>/</mo><mrow><mo>(</mo><msup><mi>K</mi><mo>+</mo></msup><mo linebreak='badbreak'>+</mo><msup><mi>K</mi><mo>&#8722;</mo></msup><mo>)</mo></mrow></mrow></math> in central collisions show a suppression relative to peripheral collisions at the (1.7&#8211;3.6)&#8201; <italic>&#963;</italic> level, while a thermal model without final-stage rescattering overpredicts this ratio with a deviation of (6.9&#8211;8.2)&#8201; <italic>&#963;</italic>. These results indicate a loss of the measured <italic>K</italic> &#8270;0 signal in central collisions due to re-scattering of its hadronic decay products in the hadronic phase. The <italic>p<inf>T</inf></italic>-integrated yield of charged kaons exhibits an approximate scaling with charged-particle multiplicity, independent of collision energy and system size. A similar trend is observed for the short-lived <italic>K</italic> &#8270;0 resonance, although significant deviations emerge at lower energies. At BES energies, the <italic>K</italic> &#8270;0/ <italic>K</italic> ratio shows stronger suppression than at the highest RHIC and LHC energies within a given multiplicity bin, particularly in central and mid-central collisions. This behavior is consistent with changes in the effective hadronic interaction cross section and is supported by transport model calculations, which indicate dominant meson&#8211;baryon interactions at lower energies and meson&#8211;meson interactions at higher energies.

JINR

G. Agakishiev

A. Aitbayev

I. Alekseev

E. Alpatov

A. Aparin

G.S. Averichev

I.G. Bordyuzhin

A.V. Brandin

T.G. Dedovich

A.A. Derevschikov

X.H. He

Probing late-stage hadronic interactions at high baryon density via <italic>K</italic> &#8270;0 production in the RHIC beam energy scan program

The correlation between the mean transverse momentum, [ <italic>p</italic> <inf>T</inf>], and the squared anisotropic flow, <math altimg='si8.svg'><msubsup><mi>v</mi><mi>n</mi><mn>2</mn></msubsup></math>, on an event-by-event basis has been suggested to be influenced by the initial conditions in heavy-ion collisions. We present measurements of the variances and covariance of [ <italic>p</italic> <inf>T</inf>] and <math altimg='si8.svg'><msubsup><mi>v</mi><mi>n</mi><mn>2</mn></msubsup></math>, along with their dimensionless ratio, for Au+Au collisions at various beam energies: <math altimg='si9.svg'><msqrt><msub><mi mathvariant='italic'>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math> = 14.6, 19.6, 27, 54.4, and 200 GeV. Our measurements reveal a distinct energy-dependent behavior in the variances and covariances. In addition, the dimensionless ratio displays a similar behavior across different beam energies. We compare our measurements with hydrodynamic models and similar measurements from Pb+Pb collisions at the Large Hadron Collider (LHC). These findings provide valuable insights into the beam energy dependence of the specific shear viscosity ( <italic>&#951;</italic>/ <italic>s</italic>) and initial-state effects, allowing for differentiating between different initial-state models.

Russia

M. Calderón De La Barca Sánchez

Beam-energy dependence of correlations between mean transverse momentum and anisotropic flow of charged particles in Au+Au collisions at RHIC

Rapidity-odd directed flow <italic>v</italic> <inf>1</inf> measurements are presented for <italic>K</italic> &#8239;&#177;&#8239; and <math altimg='si4.svg'><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup></math> in Au + Au collisions for <math altimg='si5.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math> from 3.0 to 3.9&#8239;GeV with the STAR experiment. For comparison, <italic>v</italic> <inf>1</inf> of <italic>&#960;</italic> &#8239;&#177;&#8239;, protons, and &#923; from the same collisions are also discussed. The mid-rapidity <italic>v</italic> <inf>1</inf> slope <math altimg='si9.svg'><mrow><mtext>d</mtext><msub><mi>v</mi><mn>1</mn></msub><msub><mrow><mo>/</mo><mtext>d</mtext><mi>y</mi><mo>|</mo></mrow><mrow><mi>y</mi><mo>=</mo><mn>0</mn></mrow></msub></mrow></math> for protons and &#923; is positive in these collisions. On the other hand, <italic>v</italic> <inf>1</inf> slope of kaons exhibits a strong <math altimg='si8.svg'><msub><mi>p</mi><mtext>T</mtext></msub></math> dependence: negative at <math altimg='si19.svg'><mrow><msub><mi>p</mi><mtext>T</mtext></msub><mo linebreak='goodbreak'>&lt;</mo></mrow></math> 0.6&#8239;GeV/ <italic>c</italic> and positive at higher <math altimg='si8.svg'><msub><mi>p</mi><mtext>T</mtext></msub></math>. A similar <math altimg='si8.svg'><msub><mi>p</mi><mtext>T</mtext></msub></math> dependence is also evident for the <italic>v</italic> <inf>1</inf> slope of charged pions. Compared to the spectator-removed calculations in Au+Au collisions at <math altimg='si20.svg'><mrow><msqrt><msub><mi>s</mi><mtext>NN</mtext></msub></msqrt><mo linebreak='goodbreak'>=</mo></mrow></math> 3.0&#8211;3.9&#8239;GeV, the JAM model demonstrates a pronounced shift of the <italic>v</italic> <inf>1</inf> slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low <math altimg='si8.svg'><msub><mi>p</mi><mtext>T</mtext></msub></math> in the high baryon density region of non-central collisions.

Measurement of kaon directed flow in Au+Au collisions in the high baryon density region

The STAR experiment reports new, high-precision measurements of the transverse single-spin asymmetries for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mo>±</mo></msup></math> within jets, namely the Collins asymmetries, from transversely polarized <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>p</mi><mo stretchy="false">↑</mo></msup><mi>p</mi></math> collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>510</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. The energy-scaled distribution of jet transverse momentum, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>x</mi></mrow><mrow><mi mathvariant="normal">T</mi></mrow></msub><mo>=</mo><mn>2</mn><msub><mrow><mi>p</mi></mrow><mrow><mi mathvariant="normal">T</mi><mo>,</mo><mtext>jet</mtext></mrow></msub><mo>/</mo><msqrt><mrow><mi>s</mi></mrow></msqrt></mrow></math>, shows a remarkable consistency for Collins asymmetries of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>π</mi><mo>±</mo></msup></math> in jets between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and 510 GeV. This indicates that the Collins asymmetries are nearly energy independent, with, at most, a very weak scale dependence in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>p</mi><mo stretchy="false">↑</mo></msup><mi>p</mi></math> collisions. These results extend to high-momentum scales (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>≤</mo><mn>3400</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>GeV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>) and enable unique tests of evolution and universality in the transverse-momentum-dependent formalism, thus providing important constraints for the Collins fragmentation functions.

W. Guryn

Y. He

Energy Independence of the Collins Asymmetry in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>p</mi></mrow><mrow><mo stretchy="false">↑</mo></mrow></msup><mi>p</mi></mrow></math> Collisions

The polarization of <math altimg='si1.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math>, <math altimg='si6.svg'><mover accent='true'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle><mo>&#175;</mo></mover></math>, <math altimg='si3.svg'><msup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mo>&#8722;</mo></msup></math>, and <math altimg='si16.svg'><msup><mover accent='true'><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mo>&#175;</mo></mover><mo>+</mo></msup></math> hyperons along the angular momentum of the system has been measured in isobar collisions of Ru+Ru and Zr+Zr at <math altimg='si5.svg'><msqrt><msub><mi>s</mi><msub><mrow /><mrow><mrow><mi mathvariant='normal'>N</mi></mrow><mi>N</mi></mrow></msub></msub></msqrt></math> = 200&#8239;GeV with the STAR detector at RHIC. The polarization dependence on collision centrality exhibits an increasing trend in more peripheral collisions. <math altimg='si1.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math> and <math altimg='si6.svg'><mover accent='true'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle><mo>&#175;</mo></mover></math> polarization dependence on the transverse momentum and pseudorapidity have been investigated, but no significant dependence was observed. The polarizations of <math altimg='si1.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math> and <math altimg='si6.svg'><mover accent='true'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle><mo>&#175;</mo></mover></math> are found to be consistent with each other, indicating little contribution of the spin-magnetic coupling to the measured polarization. Comparison to previously measured polarization in Au+Au collisions show no obvious system size dependence. The results are qualitatively consistent with hydrodynamic calculations including contributions from shear-induced polarization and thermal vorticity. For the first time in heavy-ion collisions, the dependence of the global polarization on the hyperon&#8217;s emission azimuthal angle relative to the second-order event plane has been measured, indicating stronger polarization for the in-plane emitted hyperons at the level of 2.4 <math altimg='si17.svg'><mi>&#963;</mi></math> significance in 20&#8211;50 % centrality. The <math altimg='si18.svg'><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle></math> hyperon polarization measurements via polarization transfer analysis yield finite positive values with 2.9 <math altimg='si17.svg'><mi>&#963;</mi></math> significance in 20&#8211;50 % centrality, slightly larger compared to the inclusive <math altimg='si1.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math> polarization.

M. Calderón de La Barca Sánchez

M. Csanad

C. Hu

Q. Hu

Y. Hu

H. Huang

Hyperon global polarization in isobar Ru+Ru and Zr+Zr collisions at <math altimg='si15.svg'><mrow><msqrt><msub><mi>s</mi><msub><mrow /><mrow><mrow><mi mathvariant='normal'>N</mi></mrow><mi>N</mi></mrow></msub></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>200</mn><mrow><mrow><mi mathvariant='normal'>G</mi></mrow><mi>e</mi><mi>V</mi></mrow></mrow></math>

We report on the measurements of directed flow <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> and elliptic flow <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> for hadrons ( <math altimg='si4.svg'><msup><mi>&#960;</mi><mo>&#177;</mo></msup></math>, <math altimg='si5.svg'><msup><mi>K</mi><mo>&#177;</mo></msup></math>, <math altimg='si6.svg'><msubsup><mi>K</mi><mrow><mi>S</mi></mrow><mn>0</mn></msubsup></math>, <math altimg='si15.svg'><mi>p</mi></math>, <math altimg='si7.svg'><mi>&#981;</mi></math>, <math altimg='si2.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math> and <math altimg='si8.svg'><msup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mo>&#8722;</mo></msup></math>) from Au+Au collisions at <math altimg='si16.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math> = 3 GeV and <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> for ( <math altimg='si4.svg'><msup><mi>&#960;</mi><mo>&#177;</mo></msup></math>, <math altimg='si5.svg'><msup><mi>K</mi><mo>&#177;</mo></msup></math>, <math altimg='si15.svg'><mi>p</mi></math> and <math altimg='si17.svg'><mover><mrow><mi>p</mi></mrow><mo stretchy='true'>&#8254;</mo></mover></math>) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the number-of-constituent-quark (NCQ) scaling holds, at 3 GeV the <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> and positive <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> slope at 3 GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.

D. Isenhower

M. Daugherity

L. Fulek

M. Przybycien

R. Sikora

D.N. Svirida

D.G. Underwood

H.M. Spinka

M. Zurek

F.M. Fawzi

M.S. Abdallah

J. Jia

A. Jentsch

A. Kiselev

A. Lebedev

A. Ogawa

A.H. Tang

A.S. Nunes

B.S. Page

F. Videbæk

G. Van Buren

H.W. Ke

J. Lauret

J.C. Webb

J.H. Lee

J.M. Landgraf

K. Kauder

K. Yip

L. Didenko

L. Ruan

P. Sorensen

P. Tribedy

P.V. Shanmuganathan

R. Ma

R. Pak

R.S. Longacre

T. Ljubicic

T. Ullrich

W.B. Schmidke

Z. Tu

Z. Xu

Z. Zhang

C. Perkins

E.G. Judd

J.M. Nelson

B. Kimelman

J.L. Romero

S. Heppelmann

Z.W. Sweger

B.K. Chan

D. Neff

G. Igo

G. Wang

H.Z. Huang

L. Wen

Erratum: Disappearance of partonic collectivity in √ <italic>s</italic> <inf>NN</inf> = 3 GeV Au+Au collisions at RHIC [Phys. Lett. B 827, 137003 (2022)]