1. Spontaneous Parity Violation in Strong Interactions Dhevan Gangadharan (UCLA) On behalf of the STAR Collaboration WWND 2009 1

2. Parity and How it’s Violated Parity transformation – a spatial inversion of a system’s coordinates. Two classes of Parity Violation: 1.Explicit parity violation  Occurs in Weak Interactions ▫Confirmed 2.Spontaneous parity violation  Predicted to occur in Strong Interactions ▫Not yet confirmed (that’s what we are working on) 2

3. Parity Violation in Weak Interactions 3 S e- Co-60 beta decay This is an Explicit parity violation because a parity violating term is explicitly seen in the Weak Lagrangian S e- P transformation Experimentally observedNot Experimentally observed

4. 4 Parity Violation in Strong Interactions First Ingredient: Vacuum Transition N CS = -2 -1 0 1 2 N CS is the Chern-Simons number and it characterizes the particular gluon field configurations we may create at RHIC. The potential energy of the gluon field is periodic in one direction and oscillator-like in all other directions in functional space. Potential Energy of the Gluon Field

5. 5 Parity Violation in Strong Interactions Second Ingredient: An Extremely Large Magnetic Field Spectator nuclei create a very large magnetic field in the QGP region. STAR TPC Magnetic field is only.5 T Largest steady magnetic field created by man ~ 15 T Spectator magnetic field @ (1 fm/c and b=4fm) ~ 10 12 T = 1 Trillion Tesla

6. Parity Violation in Strong Interactions 6 Ingredient 1 + Ingredient 2 -> Electric field E y An E y will then produce charge separation. This is Spontaneous parity violation since the sign of E y goes according to the spontaneously chosen sign of N CS and is not determined by the initial conditions of the collision Kharzeev et al. arXiv : 0406.125v2 0706.1026v2 0711.0950v1 0808.3382v1 The Chiral Magnetic Effect De-confinement is a must!

7. Looking For Charge Separation 7 For this analysis we are particularly interested in a 1

8. Looking for Charge Separation Charge separation is given by a ≠ 0 in However, will vanish when averaged over many events because of the equal presence of +1 and -1 N CS states. 8

9. Looking for Charge Separation Thus, one must use correlation techniques: This correlator is P-even. It is therefore susceptible to non-parity violating processes. 9 S. A. Voloshin, Phys. Rev. C 70, 057901 (2004) Typically we scale this by v 2,c

10. A Theoretical Prediction for AuAu 130 GeV 10 Kharzeev et al. arXiv: 0711.0950v1 This plot represents just one possible experimental result and based on some assumptions such as the magnitude of the: 1.Vacuum transition rate 2.Magnetic field strength Experimental result in 200 GeV AuAu roughly obeys this trend and order of magnitude

11. Cuts Applied to Data -30 cm < Primary Vertex Z < 30 cm -1 < eta < 1 P t >.15 GeV/c P t < 2 GeV/c for P t integrated plots At least 15 TPC hit points required #hit points/#possible hit points >.52 11 There are many independent STAR analyses on this subject which are consistent with each other. The work presented here represents only a small selection of our results

12. Other Contributions to our Correlator P-even processes may make a Contribution Flowing Resonances ▫A resonance may be flowing elliptically (in-plane) and decay into 2 charged particles which may exhibit charge separation. Jets ▫Since they are clusters of correlated charged particles, jets may fake a signal. Acceptance Effects may make a Contribution Re-Centering ▫The effect of this type of acceptance correction will be demonstrated in this talk. 12

13. We take the contribution from flowing resonances to our correlator to be We estimate the average over resonances from an upper estimate of non- flow azimuthal correlations in 200 GeV AuAu data from. And the total contribution is found to be less than 1% of a 1 Background Contributions 13 1. Flowing Resonances may fake a signal Too small to fake a signal STAR Collaboration, J. Adams et al., Phys. Rev. Lett. 92, 062301 (2004). f res represents the fraction of charged particles coming from a resonance.

14. We take the contribution from jets to our correlator to be We estimate the first term from distributions in 200 GeV AuAu data. And the total contribution is found to be ≈10 -7 Background Contributions 14 2.Jets may fake a signal Too small to fake a signal

15. Our Correlator in Simulated Data 15 Preliminary result None of these models incorporate correlations generated by the Chiral Magnetic Effect! Study done by : Evan Finch (Yale), Ilya Selyuzhenkov (Indiana), Sergei Voloshin (Wayne State)

16. Acceptance Correction Study in Simulated Data 16 Before Re-CenteringAfter Re-Centering The act of Re-Centering, i.e., does not remove the signal Centrality Bin Study done by Alexei Chikanian (Yale) Preliminary result

17. Acceptance Correction Study with Identified Pions in AuAu200 17 Electrons Rejected Study done by Jim Thomas(LBNL) Before Corrections After Corrections Preliminary result

18. Conclusions Heavy Ion Collisions at RHIC might produce spontaneous parity violation of the strong interactions. The magnitude and gross features of a theoretical prediction have been presented. However, more theoretical calculations of the expected signal would be very helpful. So far, no P-even processes which could masquerade as the result we see have been identified. 18

19. The STAR parity-v group Indiana: I. Selyuzhenkov BNL: V.Dzhordzhadze, R. Longacre, Y. Semertzidis, P. Sorensen LBNL: J. Thomas Yale: J. Sandweiss, E. Finch, A. Chikanian, R. Majka UCLA: G. Wang, D. Gangadharan Wayne State: S. Voloshin 19 More information about this analysis can be found in Sergei Voloshin’s QM08 Poster “Probe for the (Strong Interaction) parity violation effects in heavy ion collisions with three particle correlations”