Charge asymmetry dependency of $\pi$/K anisotropic flow in U+U and Au+Au collisions at STAR

20 May 2014, 10:00
helium (darmstadtium)



Schlossgraben 1 64283 Darmstadt Germany
Contributed Talk QCD Phase Diagram QCD phase diagram


Qi-Ye Shou (SINAP, BNL)


Theoretical studies [1] indicate that in relativistic heavy collisions a chiral magnetic wave at finite baryon density could induce an electric quadrupole moment, which will lead to a difference in elliptic flow of hadrons with opposite charge. The magnitude of this difference is predicted to be proportional to the charge asymmetry $A_\mathrm{ch}$, defined as $A_\mathrm{ch} \equiv \langle \left (N_{+} -N_{-} \right )/\left ( N_{+} +N_{-} \right ) \rangle$. Charge-asymmetry dependency of the pion elliptic flow has been observed in Au+Au collisions at the STAR experiment. On the other hand, it is argued that the local charge conservation at freeze-out, together with the characteristic shape of $v_{2}(\eta)$ and $v_{2}(p_\mathrm{T})$, may also contribute to elliptic flow splitting as a function of $A_\mathrm{ch}$. This can be manifested by implementing the corresponding measurement for higher flow harmonics $v_{3}$ [2]. Here, we present STAR's measurements of $v_{2}$ and $v_{3}$ for charged pions and kaons at low transverse momentum range (0.15 $< p_\mathrm{T} <$ 0.5 GeV/c), as a function of event charge asymmetry ($A_\mathrm{ch}$) in both U+U collisions at $\sqrt{s_\mathrm{NN}}$ = 193 GeV and Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV. Our measurements for both collision systems serve as important consistency checks for the phenomena suggested as the consequence of the chiral magnetic wave. [1] Burnier Y, Kharzeev D E, Liao J and Yee H U 2011 $\it{Phys. Rev. Lett}$ $\bf{ 107}$ 052303 [2] Bzdak A and Bozek P 2013 $\it{Physics Letters B}$ $\bf{ 726}$ 239-243
On behalf of collaboration: STAR

Primary author

Qi-Ye Shou (SINAP, BNL)

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