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Have we seen Local Parity Violation at RHIC?

Have we seen Local Parity Violation at RHIC?. Introduction What the present data tell us Alternative observable. Based on: Adam Bzdak, VK and Jinfeng Liao, PRC81 031901(R) (2010), [arXiv:0912.5050] J. Liao, VK, and Adam Bzdak, in preparation. CPT is in good shape. C.

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Have we seen Local Parity Violation at RHIC?

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  1. Have we seen Local Parity Violation at RHIC? Introduction What the present data tell us Alternative observable Based on: Adam Bzdak, VK and Jinfeng Liao, PRC81 031901(R) (2010), [arXiv:0912.5050] J. Liao, VK, and Adam Bzdak, in preparation

  2. CPT is in good shape C onjecture P ress Release T hink

  3. J. Liao, BNL workshop, April 2010

  4. The basic observable Py (out-of-plane) Y (out-of-plane) B current Px (in-plane) X (in-plane) Momentum space Coordinate space Charge Separation or Electric Dipole in Pt Space (along out-of-plane direction) Complications: • hard to identify direction of magnetic field (reaction plane)P. E-by-E • Direction of dipole either parallel OR anti-parallel to magnetic field → only variance of parity-odd operator can be observed

  5. The STAR measurement(which everybody discusses)

  6. The STAR measurement(a closer look) Concentrate on same sign pairs for the moment Py(out-of-plane) Set + + Px(in-plane) for both configurations Py(out-of-plane) + + Px(in-plane) How to distinguish?

  7. The STAR measurement(which not so many discuss) Add to the mix Py(out-of-plane) + + Px(in-plane) opp. sign. Py(out-of-plane) same sign + + Px(in-plane) Data favor in-plane back-to-back correlation

  8. J. Liao

  9. The bottom line

  10. Using simple math Same Charge out-of-plane STAR measures for same sign pairs in Au+Au: in-plane Therefore: opp. Charge No out-of-plane correlation for same charge pairs Opposite charge: out-of-plane in-plane

  11. Saving the chiral magnetic effect...

  12. Bout, Bin = Background (in and out of plane) P = Parity violating signal The argument in the STAR papers: Thus: The data show Thus existence of CME would require: • “Juuuuust right scenario” a.k.a fine tuning !!! • We need to understand the background • We need differential information on

  13. Do we understand the background NO!

  14. How realistic is the assumption ? Implies: “background” correlations are independent of reaction plane Two particle density: Reaction plane dependence always enters via v2 ! Pt – and eta dependence of v2 needs to be taken into account Prominent example: HBT with respect to the reaction plane Sources discussed in context of CME: Clusters (STAR, F. Wang), Resonances (STAR), .Anomaly (Asakawa et al)...

  15. Pt-dependence Correlated pairs are only moderately harder than thermal pairs

  16. Alternative observable Reaction plane angle Quadrupole moment Charged dipole moment Charged dipole angle

  17. Extract dipole moment and angle

  18. J. Liao

  19. J. Liao

  20. Correlations can lead to similar dipole angel; but reduce magnitude

  21. Summary Data favor in-plane back-to-back correlation for same charge CME predicts out of plane Presence of CME requires fine-tunining: Background = - CME ? Need differential information on Be aware that pt- and eta dependencemay be differernt Alternative observable: measure charge dipole (orientation and magnitude) How about proton-proton???? Py(out-of-plane) + + Px(in-plane)

  22. Conclusion NO definitive evidence for local parity violation! Yet !?

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