Event-By-Event Correlations Between Lambda Hyperon and the Chiral Magnetic Effect Observables in Au+Au Collisions at 27 Gev from

Yicheng Feng, Purdue University

Abstract

Spin-orbit interactions cause a global polarization (P) of Λ (Λ¯) with the vorticity (or total angular momentum) in the participant collision zone. The strong magnetic field mainly created by the spectator protons would split the Λ and Λ¯ global polarization (∆P = PΛ −PΛ¯ < 0). Quantum chromodynamics (QCD) predicts topological charge fluctuation in vacuum, resulting in a chirality imbalance, or parity violation in a local domain. This would give rise to an imbalanced left- and right-handed Λ (Λ¯), ∆n = NL−NR /‹NL+NR› 6≠ 0, as well as a charge separation along the magnetic field, referred to as the chiral magnetic effect (CME). The latter can be characterized by the parity-even ∆γ and parity-odd ∆a1 observables. While measurements of the individual ∆P [1, 2], ∆γ, and ∆a1 have not led to affirmative conclusions on the CME or the magnetic field, correlations among these observables may reveal new insights [3, 4]. We report exploratory measurements of event-by-event correlations between ∆P and ∆γ, and between ∆n and ∆a1, by the STAR experiment in Au+Au collisions at √ snn= 27 GeV. No correlations have been observed beyond statistical fluctuations. Future endeavor would be to extract an upper limit from the data as well as to apply the correlation analysis to other data samples.

Degree

Ph.D.

Advisors

Wang, Purdue University.

Subject Area

Particle physics|Atomic physics|Electromagnetics|Physics

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