Charge Asymmetry Dependence of π/K Anisotropic Flow in UU and AuAu Collisions at RHIC
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Charge Asymmetry Dependence of /K Anisotropic Flowin UU and AuAu Collisions at RHICQiYe Shou (for the STAR Collaboration)

Charge Separation in HICCharge asymmetry w.r.t. reaction plane as a signature of Local Parity ViolationCharge separation is believed as a consequence of chiral magnetic effectD. E. Kharzeev, L. D. McLerran, and H. J. Warringa, Nuclear Physics A 803, 227 (2008)B. Abelev et al. Phys. Rev. Lett. 103, 251601 (2009)

Chiral Magnetic Wave (CMW)Y. Burnier, D. E. Kharzeev, J. Liao and HU Yee, Phys. Rev. Lett. 107, 052303 (2011)Hongwei Ke (for the Star Collaboration) 2012 J. Phys.: Conf. Ser. 389 012035Measurements consistent with the expectation of CMW

CMW Draw Lots of Theoretical AttentionExpanding QCD
Signal is very small, but can be enhanced if early asymmetries in the axial charge distribution existsHydro calculation
The intercept, instead of the slope, is sensitive to anomalous transport effects (CMW)Freezeout condition is important. CMW effect is not small if calculated realistically

One Possible ExplanationLocal Charge ConservationA. Bzdak, P. Bozek, Physics Letters B 726 (2013) 239243Hydro model + Local charge conservation at freezeout
slope(v2) / slope(v3) ~ 3
The window depedence

What This Study Provides ...Y. Burnier, D. E. Kharzeev, J. Liao and HU Yee, Phys. Rev. Lett. 107, 052303 (2011)Ingredients for various consistency checks:The measurement in UU collisionsdifferent geometry setup
The slope of v2(Ach) for kaonsother particle species with different v2
The measurement of v3() as a function of Achtest for Hydro + Local charge conservation at freezeout

RHICSTARTPC and ToF are used for particle idenification

Data AnalysisFlow CalculationA. Bilandzic, R. Snellings and S. Voloshin, Phys. Rev. C 83, 044913 (2011)Qcumulant method
between two correlated particles should be larger than 0.3 to suppress nonflow effect

Data AnalysisCharge AsymmetryEach bin has the same number of eventsApply the same cuts in MonteCarlo and real data calculation

Data AnalysisSlope Parameterv3 vs AchSlope(v3) < slope(v2) in midcentrality

Resultv2() Slope vs. Centrality (Au vs. U)
Slope in UU collisions is consistent with that in AuAu collisions

Resultv2(K) Slope vs. CentralitySlope of v2 vs Ach for kaons could be different from slope for pions (flow difference are likely to be masked or reversed)
Slope ()2.920.10 %Slope (K)1.650.44 %

Resultv2(), v3() Slope vs. CentralityIn midcentrality bins, the slope of v3() is much smaller than that of v2()

ResultComparison between slope(v2) and slope(v3)Combining 2060% centrality bins, slope(v3) value is 3.2 away from 1/3 of slope(v2)v2v3
slope(v2)2.920.10 %slope(v3)0.070.28 %

Resultv2(), v3() Slope vs. Centrality (Narrow )Results do not show dependence

SummaryThe same linear relationship between v2() and Ach has been observed in both minimum bias AuAu and UU collisions
The first attempt to study the slope for v2(K)v2(K) results show consistency with CMW expectations
v3() as a function of Ach studied in AuAu and UU collisionsIn midcentral collisions, the ratio of slope of v3(Ach) to that of v2(Ach), is 3.2 below the predicted value (1/3) from hydro + local charge conservation at freezeout. This indicates that it is unlikely that such effect can have a significant contribution to the splitting of v2() as a function of Ach
Both v3(Ach) and v2(Ach) measurements do not show dependence Thank you for your attention!

Backup

Data AnalysisEvent, Track SelectionEvent
Run10 AuAu 200GeV~328M MinBias Run11 AuAu 200GeV~555M MinBiasRun12 UU 193GeV~643M MinBias
Vz < 30 cmVr < 2 cmCharge Asymmetry
All charged particles excluding (anti)proton with pT < 0.4 GeV/c
0.15 < pT < 12 GeV/c < 1Flow
Primary TracksDCA < 1 cmPion PID n

Data AnalysisFlow Calculation  1A. Bilandzic, R. Snellings and S. Voloshin, Phys. Rev. C 83, 044913 (2011)

Data AnalysisFlow Calculation  2 between two correlated particles should be larger than 0.3 to subtract nonflow effect
Divide a given event into two subgroups according to to guarantee the gapYadav Pandit (for the Star Collaboration) 2013 J. Phys.: Conf. Ser. 420 012038