Measurements of the chiral magnetic effect with background isolation in 200 GeV Au+Au collisions at STAR

0502950 - ÚJF 2020 RIV NL eng J - Journal Article
Zhao, J. - Adam, J. - Adamczyk, L. - Adams, J. R. - Adkins, J. K. - Agakishiev, G. - Bielčík, J. - Bielčíková, Jana - Chaloupka, P. - Federič, Pavol - Harlenderová, A. - Holub, L. - Kocan, M. - Kosarzewski, L. K. - Kramárik, L. - Kvapil, J. - Lidrych, J. - Líčeník, R. - Matonoha, O. - Moravcová, Z. - Rusňák, Jan - Rusňáková, O. - Šimko, Miroslav - Šumbera, Michal - Vaněk, Jan … Total 349 authors
Measurements of the chiral magnetic effect with background isolation in 200 GeV Au+Au collisions at STAR.
Nuclear Physics. A. Roč. 982, č. 2 (2019), s. 535-538. ISSN 0375-9474. E-ISSN 1873-1554.
[27th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018). Venice, 13.05.2018-19.05.2018]
Institutional support: RVO:61389005
Keywords : STAR collaboration * heavy ion collisions * chiral magnetic effect
OECD category: Nuclear physics
Impact factor: 1.695, year: 2019
Method of publishing: Open access
https://doi.org/10.1016/j.nuclphysa.2018.08.035

Using two novel methods, pair invariant mass (m(inv)) and comparative measurements with respect to reaction plane (Psi(RP)) and participant plane (Psi(PP)), we isolate the possible chiral magnetic effect (CME) from backgrounds in 200 GeV Au+Au collisions at STAR. The invariant mass method identifies the resonance background contributions, coupled with the elliptic flow (v(2)), to the charge correlator CME observable (Delta gamma). At high mass (m(inv) > 1.5 GeV/c(2)) where resonance contribution is small, we obtain the average Delta gamma magnitude. In the low mass region (m(inv) < 1.5 GeV/c(2)), resonance peaks are observed in Delta gamma(m(inv)). An event shape engineering (ESE) method is used to model the background shape in m(inv) to extract the potential CME signal at low m(inv). In the comparative method, the Psi(RP) is assessed by spectator neutrons measured by the ZDCs, and the Psi(PP) by the 2nd-harmonic event plane measured by the TPC. The v(2) is stronger along Psi(PP) and weaker along Psi(RP), in contrast, the magnetic field, mainly from spectator protons, is weaker along Psi(PP) and stronger along Psi(RP). As a result, the Delta gamma measured with respect to Psi(RP) and Psi(PP) contain different amounts of CME and background, and can thus determine these two contributions. It is found that the possible CME signals with background isolation by these two novel methods are small, on the order of a few percent of the inclusive Delta gamma measurements.
Permanent Link: http://hdl.handle.net/11104/0294790