Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session S04: Implications of the Isobar RunInvited Live Streamed
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Sponsoring Units: GHP DNP Chair: Rosi Reed, Lehigh University Room: Salon 2 |
Monday, April 11, 2022 1:30PM - 2:06PM |
S04.00001: Most Wanted: Chiral Magnetic Effect Invited Speaker: Jinfeng Liao Gauge fields provide the fundamental interactions in the Standard Model of particle physics. Gauge field configurations with nontrivial topological windings are known to play crucial roles in many important phenomena, from matter-anti-matter asymmetry of today's universe and the permanent quark confinement to topological phases in condensed matter. Their presence is however elusive for direct detection in experiments. It turns out that measurements of the so-called chiral magnetic effect (CME) in heavy ion collisions can be used to access and manifest gauge field topology. The CME is a nontrivial macroscopic transport process arising from microscopic quantum anomaly of underlying chiral fermions in a chiral material (e.g. a Dirac/Weyl semimetal or a quark-gluon plasma), which has been in the spotlight lately across disciplines of physics. Potential discovery of CME in heavy ion collisions is of utmost significance, with extensive experimental searches carried out over the past decade. Some twelve years after the first hint of a possible CME signal, excitement has been mounting on a key experiment: the isobar collisions at the Relativistic Heavy Ion Collider (RHIC). With the first isobar run analysis results just released, this talk will evaluate the key implications of this initial message for the CME search and discuss important issues to be further addressed with near-term theoretical/experimental efforts in order to draw a convincing interpretation from the rich isobar dataset. |
Monday, April 11, 2022 2:06PM - 2:42PM |
S04.00002: Overview of the Experimental Results on the CME signal Invited Speaker: Aihong Tang The chiral magnetic effect (CME) is predicted to occur as a consequence of local parity violation of the strong interaction under a strong electro-magnetic field generated in relativistic heavy-ion collisions. The existence of CME would be the manifestation of a fundamental structure of QCD vacuum --- its topological fluctuation. The experimental signal for CME involves a separation of positively and negatively charged hadrons along the direction of the magnetic field. The search for the CME in relativistic heavy ion collisions has been carried out over the past decade, and is usually complicated by various backgrounds which also contribute to the charge separation. To better control the influence of signal and backgrounds, the STAR collaboration at RHIC performed a highly anticipated analysis of isobar collisions. In this talk I will review previous measurements at both RHIC and LHC, and in particular I will discuss the result from isobar collisions that was recently reported by the STAR collaboration. I will also discuss the implication of our current results on future search efforts. |
Monday, April 11, 2022 2:42PM - 3:18PM |
S04.00003: Results on charge correlations with respect to the reaction plane from STAR Invited Speaker: Prithwish Tribedy The quantum fluctuations in the early stages of relativistic heavy ion collisions amidst strong electromagnetic fields can lead to violation of local P and CP symmetries of strong interaction. As a consequence of such extreme conditions one expects to observe novel phenomena such as the Chiral Magnetic Effect (CME). Previous measurements of the CME remain inconclusive because of large background contributions. In order to better control the influence of signal and backgrounds, the STAR collaboration has recently performed a blind analysis on a large data sample of approximately 3.8 billion isobar Ru+Ru and Zr+Zr collisions at the center of mass energy of 200 GeV at the Relativistic Heavy Ion Collider. In this talk I will briefly introduce the history of the CME search in HICs and discuss the findings from the isobar blind analysis. With the CME search narrowed down by the isobar program, where do we go from here? Several promising directions have been identified. High statistics data from the second phase of RHIC beam energy scan program and new detector upgrades of STAR provide a unique opportunity for CME search at low energy collisions. Also, the anticipated run of RHIC in the year 2023-25 with novel analysis techniques provide an opportunity to extract upper limits on the observability in Au+Au collisions. I will briefly review these initiatives in the context of future CME search in heavy ion collisions. |
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