CME Search Before Isobar Collisions and Blind Analysis From STAR Prithwish Tribedy for the STAR collaboration The 36th Winter Workshop on Nuclear Dynamics 1-7th March, 2020, Puerto Vallarta, Mexico In part supported by Introduction Solenoidal Tracker at RHIC (STAR) RHIC has collided multiple ion species; year 2018 was dedicated to search for effects driven by strong electromagnetic fields by STAR Isobars: Ru+Ru, Zr+Zr @ 200GeV (2018) Low energy: Au+Au 27 GeV (2018) Large systems : U+U, Au+Au @ 200 GeV P.Tribedy, WWND 2 The Chiral Magnetic Effect (Cartoon Picture) Quarks Quarks randomly aligned oriented along B antiquarks I II III IV More More right left handed handed quarks quarks J || B J || -B CME converts chiral imbalance to observable electric current P.Tribedy, WWND 2020 3 New Theory Guidance : Complexity Of An Event Magnetic field map Pb+Pb @ 2.76 TeV Axial charge profile b=11.4 fm, Npart=56 Pb+Pb 2.76 TeV, b=11.4 fm, dN5/dxT [a.u.] 0.3 6 uR>uL 0.2 4 uR<uL 0.1 2 0 0 y [fm] -2 -0.1 -4 -0.2 -6 -0.3 -6 -4 -2 0 2 4 6 x [fm] Based on: Chatterjee, Tribedy, Phys. Rev. C 92, Based on: Lappi, Schlichting, Phys. Rev. D 97, 011902 (2015) 034034 (2018) Going beyond cartoon picture: 1) Fluctuations dominate e-by-e physics, 2) B-field & domain size of axial-charge change with √s P.Tribedy, WWND 2020 4 New Theory Guidance : Complexity Of An Event Pb+Pb @ 2.76 TeV Magnetic field b=11.4 fm, N Axial charge profile Pb+Pb 2.76 TeV, b=11.4 fm, dN5/dxT [a.u.] 0.3 6 u 0.2 4 u 0.1 2 0 0 y [fm] -2 -0.1 -4 -0.2 -6 -0.3 -6 -4 -2 0 2 4 6 x [fm] Based on: Chatterjee, Tribedy, Based on: Lappi, Schlichting, 011902 (2015) 034034 (2018) Going beyond cartoon picture: 1) Fluctuations dominate e-by-e physics, 2) B-field & domain size of axial-charge change with √s P.Tribedy, WWND 2020 5 New Theory Guidance : Complexity Of An Event Pb+Pb @ 2.76 TeV b=11.4 fm, N More Left than Right _+ _+ More Right but B-field _+ downwards More Right than Left Based on: Chatterjee, Tribedy, Based on: Lappi, Schlichting, 011902 (2015) 034034 (2018) Going beyond cartoon picture: 1) Fluctuations dominate e-by-e physics, 2) B-field & domain size of axial-charge change with √s P.Tribedy, WWND 2020 6 #3: PresenceNew ofTheory strong Guidance magnetic : Complexity field Of An Event 18 Magnetic field map Pb+Pb @ 2.76 TeV Axial charge profile b=11.4 fm, Npart=56 Strong B-fields ~10 Gauss are generated18 in non-central heavy ion collisions The BEM field – 10 gauss at the peak y Pb+Pb 2.76 TeV, b=11.4 fm, dN5/dxT [a.u.] McLerran, Skokov, 1305.0774 0.3 • The B field is strong z=0 and short duration due 6 uR>uL Electro-Magnetic fields in heavy ion collisions to the velocity of the 0.2 Electro-Magnetic fields in heavy ionpassing collisions ions 4 uR<uL 18 + + – MRI uses 104 gauss Strong B-fields ~10 Gauss are generated in non-central18 heavy ion+ collisions + + Strong B-fields ~10 Gauss+ are generated in non-central heavy ion collisions 0.1 y + – 1000x MagnetoStar 2 + + y+ z=0 + + + B-field B z=0 • MagnetoB + + + + 0 0 + ++ ++ + ++ hydrodynamic+ + + effects + x lifetimey [fm] + + + + ++ + + + ++ +++ ++in the+ + QGP extend the + + + + + + + + + + + x + x + + + + + + + ++ + ++ lifetime+ of the B field -2 + + + + + + + + -0.1 – aka Lenz’s Law B B B B – Finite conductivity -4 B✕ ✕ B ⦿ ⦿ -0.2 • Recent calculations B-field direction → perpendicular to collision plane -6 2 B B-field direction → perpendicularB-field to collision magnitude plane → ~Z , ~ γ suggest the lifetime is 2 B-field magnitude → ~Z , ~ γ B-field magnitude → ~ 1/γ , conductivity of the extendedmedium in a plasma -0.3 B-field magnitudeKharzeev, → ~ 1/γ , conductivity McLerran, of the medium and Warringa 0711.0950,but the magnitude is -6 -4 -2 0 2 4 6 Skokov, Illarionov,P Tribedy, RutgersToneev Nuclear Physics 0907.1396 Seminars, Feb 12, 2018reduced x50 36from the P Tribedy, Rutgers Nuclear Physics Seminars, Feb 12, 2018 36 peak at the relevant L. McLerran, V. Skokov, Nucl.Phys. A929 (2014) 814-190 x [fm] Basedtime on: scaleChatterjee, Tribedy, Phys. Rev. C 92, Based on: Lappi, Schlichting, Phys. Rev. D 97, B-field directionJim → Thomas perpendicular011902 (2015) to collision plane 4 034034 (2018) 2 B-field magnitudeGoing → ~Z beyond, ~ γ cartoon picture: 1) Fluctuations dominate e-by-e B-field lifetime →physics, ~ 1/γ , conductivity 2) B-field & of domain the medium size of axial-charge change with √s B-field strength Motivations: → decrease time with forimpact 1) decisive parameter/overlap test, 2) revisit CME search at low √s P Tribedy, Chiral Fluids, July 16-19, 2018P.Tribedy, WWND 2020 8 7 STAR Search For Other B-field Driven Effects “Discovery of Breit-Wheeler Process” STAR, PRL121,132301(2018) STARBreit-Wheeler Collaboration, Process arXiv:1910.12400 e+ Two quasi-real photons colliding to create a see talk by D. Brandenburg real e+-e- pair Tue 3/3 e- 14 eBL ≈ 30 MeV/c, B ~ 10 T, L ~1 fm 2 12 eB > eBC ∼ me ∼ 10 G 9 P.Tribedy, WWND 8 STAR Search For Other B-field Driven Effects “Discovery of Breit-Wheeler Process” STAR, PRL121,132301(2018) STARBreit-Wheeler Collaboration, Process arXiv:1910.12400 e+ Two quasi-real photons colliding to create a see talk by D. Brandenburg real e+-e- pair Tue 3/3 e- 14 eBL ≈ 30 MeV/c, B ~ 10 T, L ~1 fm 2 12 eB > eBC ∼ me ∼ 10 G Polarization of Lambda & Anti-Lambda STAR, J.Adams, QM2019 magnetic 9 spin-orbit STAR Preliminary Independent limits on B-field : important for CME search P.Tribedy, WWND 9 CME Search Using The γ-Correlator Observable + _ Charge separation perpendicular to ΨRP Observables+ for CME search : γ-correlator γα,β = cos(φα + φβ 2Ψ ) + 1 2 RP φφ1− Charge separation across reaction− plane 2 !CME expectation " B + + Voloshin, PRC 70 γ − = cos(π/2 π/2 + 0) = 1 7 (2004) 057901 ++, − γ −− = cos(π/2+π/2 + 0) = 1 -3 -3 C88 (2013) no.6, 064911 ×10 3 ×10 − 〉 〉 ) ) − 1.51 B opposite charge RP Ψ positive charges 1.5 ΨRP 10 , Y7 (ZDC-SMD) Ψ Ψ1 - φ 1 -2 , Y7 (TPC) negative charges × Ψ2 β 1 φ , Y4 (TPC) Ψ " Ψ RP 2 + ) sin( α 〈 STAR collaboration, PRL 103, 251601 0.5 φ 0.5 (2009), PRC 88 (2013) RP Ψ cos( 0 〈 0 2 Charged − -0.5 -0.5 β 2 same charge tracks φ Reaction-plane Ψ , Y7 (ZDC-SMD) + -1 1 + (TPC) -1 φ Ψ2, Y7 2 α 1 Ψ2, Y4 (TPC) φ -1.5 -1.5 _ _ 80 70 60 50 40 30 20 10 0 cos( 80 70 60 50 40 30 20 10 0 _ Centrality (%)φ1− ! Centrality (%) FIG. 4: (Color online) sin(φα Ψ1) for positive and nega-p+AFIG. measurements 5: (Color online) Three-point indicate correlator, the rapid Eq. 1, rise mea- STAR capability⟨ to measure− ⟩ CME using γ-correlator:st nd tive charges versus centrality for Au+Au collisions at √sNN=in peripheralsured with 1 andevents 2 harmonic→ due event to planes background versus centrality Charged200 GeV. Shaded tracks area representsfrom TPC the systematic (-1<η uncertainty<1) for Au+Au collisions at √sNN=200GeV.Shownwithcrosses for both charge types obtained by comparing correlations are our previous results from the 2004 RHIC run (Y4) [9, 10]. Proxyfrom positive for reaction and negative pseudorapidity.planes: event-planes ThefromSTAR Y4 Collaboration, runZDC-SMD, used a second Phys.Lett. harmonicTPC B798 & event (2019) BBC plane. 134975 Y4 and Y7 Ψ2 results are consistent within statistical errors. Shaded P Tribedy, QCD@HighDensity,P.Tribedy, WWND Nov2020areas 12-14, for the Wuhan, 2nd harmonic 2019 points represent the systematic510 The three-point correlator measured with 1st and 2nd uncertainty of the event plane determination. Systematic un- certainties for the 1st harmonic points are negligible compared harmonic event planes is shown in Fig. 5. We find con- to the statistical ones shown. sistency between correlations obtained with both event plane types. As the pseudorapidity gap between the ZDC-SMD(Ψ1) and the TPC(particles α and β) is rather length through the medium. However, when we weight large ( 7 units in η) , we find “direct” three-particle ∼ all azimuthal regions of charge separation equally, as with effects (clusters) to be an unlikely source for the sig- the msc in Fig. 6, we do not recover a magnitude sym- nal. This is an indication that the signal is likely a gen- metry. uine correlation with respect to the reaction plane. Also The two terms of the msc in Eq. 9 are shown in Fig. 7. shown for comparison in Fig. 5 are our previous results We observe that same and opposite charge correlations from the 2004 RHIC run [9, 10] which are consistent with in the ∆N term have very similar magnitudes, but oppo- the current results within statistical errors. site signs for all centrality bins. This feature is expected The modulated sign correlations are compared with from the construction of the ∆N term due to the rela- the three-point correlator in Fig. 6. It is evident that the tively large and approximately equal positive and nega- msc is able to reproduce the same trend as the three-point tive charge multiplicities.