Strangeness in Quark Matter 2022 (SQM 2022)

Search for the Chiral Magnetic Wave in Pb–Pb collisions with the ALICE detector

14 Jun 2022, 16:30

20m

GBR1

Talk Bulk matter phenomena, QCD phase diagram, and Critical point PA-Bulk matter phenomena, QCD phase diagram, and Critical point

Speaker

Wenya Wu (Fudan University (CN))

Description

The interplay of the chiral anomaly and the strong magnetic field (~10${}^{15}$ T) created in the off-central heavy-ion collisions could give rise to a collective excitation in the quark-gluon plasma called the Chiral Magnetic Wave (CMW), which can be experimentally sought by the charge asymmetry ($A_{\mathrm{c}\mathrm{h}}$) dependence of elliptic flow $v_2$ of positively and negatively charged hadrons. However, non-CMW mechanisms such as local charge conservation (LCC) intertwined with collective flow can also lead
to a similar dependence of $v_2$ on $A_{\mathrm{c}\mathrm{h}}$. The measurement with triangular flow ($v_3$) thus serves as a reference as it is not expected to be affected by the CMW.

In this talk, we present new ALICE measurements of $v_2$ and $v_3$ of inclusive and identified hadrons as functions of $A_{\mathrm{c}\mathrm{h}}$ in Pb-Pb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 2.76 and 5.02 TeV. The slope parameters of $\mathrm{\Delta }{v}_2$-$A_{\mathrm{c}\mathrm{h}}$ and $\mathrm{\Delta }{v}_3$-$A_{\mathrm{c}\mathrm{h}}$ correlations, where the $\mathrm{\Delta }{v}_n$ are the differences between $v_n$ of positive and negative particles, are normalized and then compared with results from other experiments and models. In addition, the Event Shape Engineering (ESE) technique is adopted for the first time to quantitatively
distinguish the CMW signal and the LCC background. The upper limit of the CMW signal contribution is further extracted. Our measurements reveal that the background effect is dominant in the search for the CMW in heavy-ion collisions.

Presentation materials

SQM22-v6.pdf