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Anti-hypernuclei production and search for P-odd domain formation at RHIC

Anti-hypernuclei production and search for P-odd domain formation at RHIC. Gang Wang ( for the STAR Collaboration ) UCLA. A colored and flavored system in collision. S. Z. N. Outline. Exotic particle. Exotic phenomenon. What is a hypernucleus?.

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Anti-hypernuclei production and search for P-odd domain formation at RHIC

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  1. Anti-hypernuclei production and search for P-odd domain formation at RHIC Gang Wang(for the STAR Collaboration) UCLA A colored and flavored system in collision ...

  2. S Z N Outline Exotic particle Exotic phenomenon

  3. What is a hypernucleus? A nucleus containing at least one hyperon in addition to nucleons. Hypernuclei of lowest A No one has ever observed any anti-hypernucleus before us (STAR).   p +  - (64%);   n +  0(36%) The first hypernucleus was discovered by Danysz and Pniewski in 1952, formed in a cosmic ray interaction in a balloon-flown emulsion plate. M. Danysz and J. Pniewski, Phil. Mag. 44 (1953) 348

  4. Hypernuclei: ideal lab for YN and YY interaction – Baryon-baryon interaction with strangeness sector – Input for theory describing the nature of neutron stars Coalescence mechanism for production: depends on overlapping wave functions of Y+N at final stage Anti-hypernuclei and hypernuclei ratios: sensitive to anti-matter and matterprofiles in HIC Extension of the nuclear chart into anti-matter with S [1] Why (anti-)hypernuclei? [1] W. Greiner, Int. J. Mod. Phys. E 5 (1995) 1

  5. PANDA at FAIR • 2012~ • Anti-proton beam • Double -hypernuclei • -ray spectroscopy • SPHERE at JINR • Heavy ion beams • Single -hypernuclei • HypHI at GSI/FAIR • Heavy ion beams • Single -hypernuclei at • extreme isospins • Magnetic moments • MAMI C • 2007~ • Electro-production • Single -hypernuclei • -wavefunction • JLab • 2000~ • Electro-production • Single -hypernuclei • -wavefunction • FINUDA at DANE • e+e- collider • Stopped-K- reaction • Single -hypernuclei • -ray spectroscopy • (2012~) • J-PARC • 2009~ • Intense K- beam • Single and double -hypernuclei • -ray spectroscopy  • BNL • Heavy ion beams • Anti-hypernuclei • Single -hypernuclei • Double L-hypernuclei International Hyper-nuclear network

  6. Relativistic Heavy Ion Collider (RHIC) RHIC PHENIX STAR AGS TANDEMS Animation M. Lisa

  7. initial stage QGP and hydrodynamic expansion pre-equilibrium hadronization and freeze-out Relativistic Heavy-ion Collisions • New state of matter: QGP RHIC creates hot and dense matter, containing equilibrium in phase space population of u, d and s: ideal source of hypernuclei about equal numbers of q and anti-q: ideal source of anti-nuclei RHIC white paper: Nucl. Phys. A 757

  8. STAR Detector STAR consists of a complex set of various detectors, a wide range of measurements and a broad coverage of different physics topics.

  9. Event display STAR TPC: an effectively 3-D ionization camera with over 50 million pixels.

  10. Data-set and track selection • 3LH mesonic decay, m=2.991 GeV/c2, B.R. 0.25 • Data-set used, Au+Au 200 GeV • ~67M year 2007 minimum-bias • ~22M year 2004 minimum-bias • ~23M year 2004 central, • |VZ|<30cm • Tracks level: standard STAR quality cuts, i.e. , not near edges of acceptance, good momentum & dE/dx resolution. Secondary vertex finding technique DCA of v0 to PV < 1.2 cm DCA of p to PV > 0.8 cm DCA of p to 3He < 1.0 cm Decay length > 2.4 cm QM09 proceeding: arXiv:0907.4147

  11. 3He & anti-3He selection Theory curve: Phys. Lett. B 667 (2008) 1 • Select pure 3He sample: 3He: 5810 counts • anti-3He: 2168 counts • condition: -0.2 < z < 0.2 & dca < 1.0 cm & p > 2 GeV/c …

  12. signal from the data STAR Collaboration, Science 328 (2010) 58 Signal observed from the data (bin-by-bin counting): 157 ± 30 Mass: 2.989 ± 0.001 ± 0.002 GeV; Width (fixed): 0.0025 GeV. Projection on anti-hypertriton yield: =157*2168/5810= 59 ± 11

  13. signal from the data STAR Collaboration, Science 328 (2010) 58 Projection on anti-hypertriton yield: 59 ± 11 Signal observed from the data (bin-by-bin counting): 70 ± 17 Mass: 2.991 ± 0.001 ± 0.002 GeV; Width (fixed): 0.0025 GeV.

  14. Combined the signal STAR Collaboration, Science 328 (2010) 58 Combined hyperT and anti-hyperT signal : 225 ± 35 It provides a >6s significance for discovery.

  15. Measure the lifetime STAR Collaboration, Science 328 (2010) 58 We measure tL = 267 ± 5 ps PDG value tL = 263 ± 2 ps ps PDG: Phys. Lett. B 667 (2008) 1

  16. Production rate Tabulated ratios favor coalescence Coalescence => 0.45 ~ 0.77*0.77*0.77

  17. A case for energy scan STAR Collaboration, Science 328 (2010) 58 Phase diagram plot: arXiv:0906.0630 Baryon-strangeness correlation: PRL 95 (2005) 182301, PRC 74 (2006) 054901, PRD 73 (2006) 014004. RHIC is carrying out Beam Energy Scan as we speak. Baryon-strangeness correlation via hypernuclei: a viable experimental signal to search for the onset of deconfinement. model calculation: S. Zhang et al, Phys. Lett. B684, 224(2010)

  18. Summary I has been observed for first time; 70 candidates, with significance ~4s. Consistency check has been done on analysis; 157 candidates, with significance better than 5s. The measured lifetime is ps, consistent with free L lifetime (263 ps) within uncertainty. The / ratio is measured as 0.49 ± 0.18 ± 0.07, and 3He / 3He is 0.45 ± 0.02 ± 0.04, favoring coalescence. RHIC is the best anti-matter machine ever built!

  19. Outlook Lifetime: • –10 times more data within this year Production rate: –baryon-strangeness correlation –a case for energy scan –establish a trend from AGS-SPS-RHIC-LHC 3LHd+p+p channel measurement: d-identification via ToF. Search for other hypernucleus: 4LH, 4LHe, 4LLH, 3XH, Search for anti-α AGS-E906, Phys. Rev. Lett. 87, 132504 (2001)

  20. Parity violation Looking into a mirror, you see someone else… It’s a parity violation?! Parity transformation: A spatial inversion of the coordinates. Origins of parity violation: • Global parity violation Occurs in weak interactions • Confirmed • Local parity violation Predicted in strong interactions • we are working on it… Kharzeev, PLB 633 260 (2006) [hep-ph/0406125]; Kharzeev, McLerran, Warringa, NPA 803 227 (2008); Kharzeev, Zhitnitsky, NPA 797 67 (2007); Fukushima, Kharzeev, Waringa, PRD 78, 074033.

  21. Local P violation in strong interactions P/CP invariance are (globally) preserved in strong interactions: neutron EDM (electric dipole moment) experiments: Θ<10−11 Pospelov, Ritz, PRL83:2526 (1999) Baker et al., PRL97:131801 (2006) In heavy-ion collisions, the formation of (local) meta-stable P-odd domains is not forbidden. The strong magnetic field (B~1015 T) could induce electric field (E~θB), and manifest the P-odd domains with charge separation w.r.tReac.plane. Kharzeev, PLB633:260 (2006) Kharzeev, McLerran, Warringa, NPA803:227 (2008)

  22. S. Voloshin, PRC 70 (2004) 057901 Non-flow/non-parity effects: largely cancel out P-even quantity: still sensitive to charge separation Directed flow: vanishes if measured in a symmetric rapidity range Charge separation in strong interactions A direct measurement ofthe P-odd quantity “a” should yield zero.

  23. S. Voloshin, PRC 70 (2004) 057901 Factorization If the event plane or the third particle has non-flow correlations with the first two particles, we can NOT safely factorize the above equation.

  24. STAR ZDC-SMD • New knowledge of the direction of the impact parameter vector • Minimal, if any, non-flow/non-parity effects • Worse resolution than from TPC… can be overcome with statistics SMD is 8 horizontal slats & 7 vertical slats located at 1/3 of the depth of the ZDC ZDC side view Transverse plane of ZDC Scintillator slats ofShower Max Detector

  25. Approach With the EP from ZDC,the3-particle non-flow/non-parity correlations (independent of the reaction plane) will be basically eliminated as a source of background. As a systematic check, I also calculate directly The results on the following slides are based on Au+Au collisions at 200 GeV, taken in RHIC run2007, except otherwise specified.

  26. STAR Preliminary Results with different event planes Lost in the medium? The correlator using ZDC event plane is consistent with that using TPC event plane.

  27. STAR Preliminary Different charge combinations The + + and – – combinations are consistent with each other.

  28. Dilution effect In the quark-gluon medium, there could be multiple P-odd domains. The net effect is like a random walk,but one-dimensional. What do we know about the position Rn after n steps? Rnfollows a Gaussian distribution:mean = 0, and rms= Our measurement of PV is like Rn2, expected to be n. Compared with going in one fixed direction, where Rn2 = n2, the "random-walk"measurement is diluted by a factor ~ n ~ Nch.

  29. Dilution effect Non-zero Radial flow? Weaker B field STAR Preliminary Thin medium The factor Npart is used to compensate for dilution effect.

  30. STAR Preliminary STAR Preliminary Systematic check: v1{ZDC-SMD} S. Voloshin, PRC 70 (2004) 057901 If v1 (η) is not anti-symmetric around η= 0, then this term won’t vanish. v1 (η) crosses zero for both charges in the TPC region.

  31. STAR Preliminary Systematic check: a1{ZDC-SMD} S. Voloshin, PRC 70 (2004) 057901 The average magnitude of <a1> is ~ 10-4. Its corresponding contribution to the correlator, <a1><a1>, will be safely negligible.

  32. Systematic check: ηgap STAR Preliminary The same-sign correlation approaches zero when the η gap increases.

  33. STAR Preliminary Systematic check: pTgap The non-zero same-sign correlator for pT gap > 200 MeV/c indicates that we are safe from HBT or Coulomb effects.

  34. More checks from TPC EP STAR Collaboration, arXiv:0909.1717 We have looked at lower beam energy (62 GeV) and/or smaller system (Cu+Cu), to see qualitatively similar results.

  35. Summary II The formation of (local) meta-stable P-odd domainsin heavy-ion collisions is predicted to lead to charge separation w.r.t the reaction plane. P-even correlator has been measured with event planes from both STAR TPC and ZDC; and the results are consistent! The gross feature of the correlator meets the expectation for the picture of local Parity Violation: charge separation, suppression of OS by opacity, weaker OS signal in central collisions, OS&LS symmetry in peripheral collisions ... STAR has checked the possible effects on v1, a1,η gap, and pTgap.

  36. + Interpretations + ΨRP ΨRP Interpretation 1: Interpretation 2: Out-of-Plane Charge Separation Flowing “structures” - - X X X X X X X = unknown structure Implies Local P-violation of strong interactions Does Not Imply P violation of the strong interactions

  37. Scenario 2: charge conservation/cluster + v1 symmetry fluctuation + - ΨRP + - + - Need some investigation Interpretation 2 Scenario 1: charge conservation/cluster + v2 + - ΨRP + - STAR Collaboration, PRL103 (2009)251601

  38. Alternative measurements These observables contain all possible (mixed) harmonic terms, while the correlator observables previously shown contain only one. Charge asymmetry correlation

  39. No real reaction plane here! STAR preliminary d+Au Alternative measurements Oppo-sign: - aligned (‹A+A-› > 0) - local charge conservation? - ‹A+A-›UD>‹A+A-›LR - contradicts LPV expectation? - not dominantly RP-related Same-sign: - δ‹A2›UD>δ‹A2›LR - meets LPV expectation- δ‹A2› < 0 in central collisions Different observables have different sensitivities to the charge separation, and suffer different backgrounds.

  40. With zero net charge, the neutral particles are expected to be much less affected by the electric field. Beam Energy Scan η→π+π-et al. Neodymium(144,60)-Samarium(144,62)et al. Beam energy below QGP threshold CP-violating decays Isobaric couple of spherical nuclei : different magnetic fields: Deformed nuclei can provide the collisions with zero magnetic field and large v2 to test the theory. Λ, Ks0et al. body-body U+U collisions Outlook R. Millo and E. V. Shuryak, arXiv:0912.4894

  41. Back-up

  42. Systematic check: EP resolution

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