Complications in the interpretation of the charge asymmetry dependent $\pi$ flow for the chiral magnetic wave

Abstract

The charge asymmetry ($A_{\mathrm{ch}}$) dependence of the ${\pi }^{-}$ and ${\pi }^{+}$ elliptic flow difference, $\Delta v_2(A_{\mathrm{ch}})$, has been regarded as a sensitive observable for the possible chiral magnetic wave (CMW) in relativistic heavy ion collisions. In this work, we first demonstrate that, due to non-flow backgrounds, the flow measurements by the Q-cumulant method using all charged particles as reference introduce a trivial linear term to $\Delta v_2(A_{\mathrm{ch}})$. The trivial slope can be negative in the triangle flow difference $\Delta v_3(A_{\mathrm{ch}})$ if the non-flow is dominated by back-to-back pairs. After eliminating the trivial term, we find that the non-flow between like-sign pairs gives rise to an additional positive slope to $\Delta v_2(A_{\mathrm{ch}})$ because of the larger dilution effect to ${\pi }^{+}$ (${\pi }^{-}$) at positive (negative) $A_{\mathrm{ch}}$. We further find that the competition between different $\pi$ sources can introduce another non-trivial linear-$A_{\mathrm{ch}}$ term due to their different multiplicity fluctuations and anisotropic flows. We then study the effect of neutral cluster (resonance) decays as a mechanism for local charge conservation on the slope parameter of $\Delta v_2(A_{\mathrm{ch}})$. We find that the slope parameter is sensitive to the kinematics of those neutral clusters. Light resonances give positive slopes while heavy resonances give negative slopes. Local charge conservation from continuum cluster mass distribution can give a positive slope parameter comparable to experimental data. Our studies indicate that many non-CMW physics mechanisms can give rise to a $A_{\mathrm{ch}}$-dependent $\Delta v_2(A_{\mathrm{ch}})$ and the interpretation of $\Delta v_2(A_{\mathrm{ch}})$ in terms of the CMW is delicate.

arXiv comment9 pages and 6 figures

References in corpus (42)

• Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment
• The PHOBOS Perspective on Discoveries at RHIC
• The Chiral Magnetic Effect
• The effects of topological charge change in heavy ion collisions: "Event by event P and CP violation"
• Hydrodynamics with Triangle Anomalies
• Event-by-event generation of electromagnetic fields in heavy-ion collisions
• Event-by-event anisotropic flow in heavy-ion collisions from combined Yang-Mills and viscous fluid dynamics
• Charge separation induced by P-odd bubbles in QCD matter
• Event-by-event fluctuations of magnetic and electric fields in heavy ion collisions
• Flow analysis with cumulants: direct calculations
• First Results from Pb+Pb collisions at the LHC
• Elliptic flow at SPS and RHIC: from kinetic transport to hydrodynamics
• Chiral Magnetic Wave
• Saturation of Elliptic Flow and the Transport Opacity of the Gluon Plasma at RHIC
• Phobos results on charged particle multiplicity and pseudorapidity distributions in Au+Au, Cu+Cu, d+Au, and p+p collisions at ultra-relativistic energies
• Generic framework for anisotropic flow analyses with multi-particle azimuthal correlations
• Triangular flow in event-by-event ideal hydrodynamics in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200A$ GeV
• Effect of flow fluctuations and nonflow on elliptic flow methods
• Observation of charge asymmetry dependence of pion elliptic flow and the possible chiral magnetic wave in heavy-ion collisions
• Collective flow in 2.76 A TeV and 5.02 A TeV Pb+Pb collisions
• Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV from the STAR Experiment
• Electromagnetic field and the chiral magnetic effect in the quark-gluon plasma
• Charge-dependent flow and the search for the Chiral Magnetic Wave in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Axial Ward identity and the Schwinger mechanism -- Applications to the real-time chiral magnetic effect and condensates
• Energy and system-size dependence of two- and four-particle $v_2$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow
• Contributions to the event-by-event charge asymmetry dependence for the elliptic flow of pi^{+} and pi^{-} in heavy-ion collisions
• High order flow harmonics of identified hadrons in 2.76 A TeV Pb+Pb collisions
• Anomalous magnetohydrodynamics with longitudinal boost invariance and chiral magnetic effect
• Isolating the chiral magnetic effect from backgrounds by pair invariant mass
• Elliptic flow difference of charged pions in heavy-ion collisions
• Momentum conservation and correlation analyses in heavy-ion collisions at ultrarelativistic energies
• Will jets reduce the elliptic flow at LHC, while decays of resonances restore the constituent quark scaling?
• Disentangling flow and nonflow correlations via Bayesian unfolding of the event-by-event distributions of harmonic coefficients in ultrarelativistic heavy-ion collisions
• P and CP Violation and New Thermalization Scenario in Heavy Ion Collisions
• Probing the chiral magnetic wave in pPb and PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV using charge-dependent azimuthal anisotropies
• Isolation of Flow and Nonflow Correlations by Two- and Four-Particle Cumulant Measurements of Azimuthal Harmonics in $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 200 GeV Au+Au Collisions
• Decomposition of flow and nonflow in relativistic heavy-ion collisions
• Elliptic flow of thermal dileptons in event-by-event hydrodynamic simulation
• Charge asymmetry dependence of the elliptic flow splitting in relativistic heavy-ion collisions
• Search for the Chiral Magnetic Wave with Anisotropic Flow of Identified Particles at RHIC-STAR

Cited by in corpus (8)

• Anomalous chiral transports and spin polarization in heavy-ion collisions
• Chiral Magnetic Effects in Nuclear Collisions
• Interpreting the charge-dependent flow and constraining the chiral magnetic wave with event shape engineering
• Importance of non-flow background on the chiral magnetic wave search
• Charge-dependent transverse momentum and its impact on the search for the chiral magnetic wave
• Search for the chiral magnetic wave using anisotropic flow of identified particles at RHIC
• Recent developments in chiral and spin polarization effects in heavy-ion collisions
• Experimental review on the chiral magnetic effect in relativistic heavy ion collisions