Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME)-an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable (Delta gamma) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy (v(2)). We report here differential measurements of the correlator as a function of the pair invariant mass (m(inv)) in 20-50% centrality Au + Au collisions at root s(NN) = 200 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider. Strong resonance background contributions to Delta gamma. are observed. At large m(inv) where this background is significantly reduced, the Delta gamma. value is found to be significantly smaller. An event-shape-engineering technique is deployed to determine the v(2) background shape as a function of m(inv). We extract a v(2)-independent and m(inv)-averaged signal Delta gamma(sig) = (0.03 +/- 0.06 +/- 0.08) x 10(-4), or (2 +/- 4 +/- 5)% of the inclusive Delta gamma (m(inv) > 0.4 GeV/c(2)) = (1.58 +/- 0.02 +/- 0.02) x 10(-4), within pion p(T) = 0.2-0.8 GeV/c and averaged over pseudorapidity ranges of -1 < eta < -0.05 and 0.05 < eta < 1. This represents an upper limit of 0.23 x 10(-4), or 15% of the inclusive result, at 95% confidence level for the m(inv)-integrated CME contribution.
Adam, J., et al. "Pair Invariant Mass to Isolate Background in the Search for the Chiral Magnetic Effect in Au+Au Collisions at √sNN = 200 GeV." Physical Review. C. Nuclear Physics, vol. 106, no. 3, Sep. 2022. https://doi.org/10.1103/PhysRevC.106.034908
Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Agakishiev, G., Aggarwal, M. M., Ahammed, Z, Alekseev, I., Anderson, D. M., Aparin, A., Spinka, H. M., Underwood, D. G., & Zurek, M. (2022). Pair Invariant Mass to Isolate Background in the Search for the Chiral Magnetic Effect in Au+Au Collisions at √sNN = 200 GeV. Physical Review. C. Nuclear Physics, 106(3). https://doi.org/10.1103/PhysRevC.106.034908
Adam, J., Adamczyk, L., Adams, J. R., et al., "Pair Invariant Mass to Isolate Background in the Search for the Chiral Magnetic Effect in Au+Au Collisions at √sNN = 200 GeV," Physical Review. C. Nuclear Physics 106, no. 3 (2022), https://doi.org/10.1103/PhysRevC.106.034908
@article{osti_1991573,
author = {Adam, J. and Adamczyk, L. and Adams, J. R. and Adkins, J. K. and Agakishiev, G. and Aggarwal, M. M. and Ahammed, Z and Alekseev, I. and Anderson, D. M. and Aparin, A. and others},
title = {Pair Invariant Mass to Isolate Background in the Search for the Chiral Magnetic Effect in Au+Au Collisions at √sNN = 200 GeV},
annote = {Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME)-an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable (Delta gamma) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy (v(2)). We report here differential measurements of the correlator as a function of the pair invariant mass (m(inv)) in 20-50% centrality Au + Au collisions at root s(NN) = 200 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider. Strong resonance background contributions to Delta gamma. are observed. At large m(inv) where this background is significantly reduced, the Delta gamma. value is found to be significantly smaller. An event-shape-engineering technique is deployed to determine the v(2) background shape as a function of m(inv). We extract a v(2)-independent and m(inv)-averaged signal Delta gamma(sig) = (0.03 +/- 0.06 +/- 0.08) x 10(-4), or (2 +/- 4 +/- 5)% of the inclusive Delta gamma (m(inv) > 0.4 GeV/c(2)) = (1.58 +/- 0.02 +/- 0.02) x 10(-4), within pion p(T) = 0.2-0.8 GeV/c and averaged over pseudorapidity ranges of -1 < eta < -0.05 and 0.05 < eta < 1. This represents an upper limit of 0.23 x 10(-4), or 15% of the inclusive result, at 95% confidence level for the m(inv)-integrated CME contribution.},
doi = {10.1103/PhysRevC.106.034908},
url = {https://www.osti.gov/biblio/1991573},
journal = {Physical Review. C. Nuclear Physics},
issn = {ISSN 0556-2813},
number = {3},
volume = {106},
place = {United States},
year = {2022},
month = {09}}
National Science Foundation (NSF); Russian Federation - Ministry of Education and Science; National Natural Science Foundation of China (NSFC); Chinese Academy of Sciences (CAS); Ministry of Education of the People's Republic of China; National Research Foundation (NRF) of Korea; Czech Science Foundation (GA CR); Government of India - Department of Atomic Energy; Government of India - Department of Science and Technology; National Science Centre (Poland) (NSC); Croatian Ministry of Science, Education and Sports; Rosatom State Atomic Energy Corporation; Bundesministerium für Bildung und Forschung (BMBF); Helmholtz Association of German Research Centres; Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan; Japan Society for the Promotion of Science (JSPS); USDOE Office of Science - Office of Nuclear Physics
DOE Contract Number:
AC02-06CH11357;
OSTI ID:
1991573
Journal Information:
Physical Review. C. Nuclear Physics, Journal Name: Physical Review. C. Nuclear Physics Journal Issue: 3 Vol. 106; ISSN 0556-2813
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