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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...

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2 Outline N Z S Exotic particleExotic phenomenon

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3 No one has ever observed any anti- hypernucleus before us (STAR). 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 M. Danysz and J. Pniewski, Phil. Mag. 44 (1953) 348 p + - (64%); n + 0 (36%) What is a hypernucleus? Hypernuclei of lowest A A nucleus containing at least one hyperon in addition to nucleons.

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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 matter profiles in HIC Extension of the nuclear chart into anti-matter with S [1] [1] W. Greiner, Int. J. Mod. Phys. E 5 (1995) 1 Why (anti-)hypernuclei?

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5 International Hyper-nuclear network PANDA at FAIR 2012~ Anti-proton beam Double -hypernuclei -ray spectroscopy 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 HypHI at GSI/FAIR Heavy ion beams Single -hypernuclei at extreme isospins Magnetic moments SPHERE at JINR Heavy ion beams Single -hypernuclei BNL Heavy ion beams Anti-hypernuclei Single -hypernuclei Double -hypernuclei

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

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7 Relativistic Heavy-ion Collisions initial stage pre-equilibrium QGP and hydrodynamic expansion hadronization and freeze-out 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

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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.

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

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10 3 H mesonic decay, m=2.991 GeV/c 2, 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, |V Z | 0.8 cm DCA of p to 3 He < 1.0 cm Decay length > 2.4 cm QM09 proceeding: arXiv:0907.4147

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11 3 He & anti- 3 He selection Select pure 3 He sample: 3 He: 5810 counts anti- 3 He: 2168 counts condition: -0.2 2 GeV/c Theory curve: Phys. Lett. B 667 (2008) 1

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12 signal from the data 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 STAR Collaboration, Science 328 (2010) 58

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

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

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

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

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17 A case for energy scan 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) Baryon-strangeness correlation: PRL 95 (2005) 182301, PRC 74 (2006) 054901, PRD 73 (2006) 014004. Phase diagram plot: arXiv:0906.0630 STAR Collaboration, Science 328 (2010) 58

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

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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 3 L H d+p+p channel measurement: d-identification via ToF. Search for other hypernucleus: 4 L H, 4 L He, 4 LL H, 3 X H, Search for anti- AGS-E906, Phys. Rev. Lett. 87, 132504 (2001)

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20 Looking into a mirror, you see someone else Its a parity violation?! Parity transformation: A spatial inversion of the coordinates. Origins of parity violation: 1. Global parity violation Occurs in weak interactions Confirmed 2. 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. Parity violation

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21 P/CP invariance are (globally) preserved in strong interactions: neutron EDM (electric dipole moment) experiments:

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

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

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35 Summary II The formation of (local) meta-stable P-odd domains in 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 v 1, a 1, gap, and p T gap.

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36 Interpretations - + RP + - Out-of-Plane Charge Separation Interpretation 1: RP Flowing structures Interpretation 2: 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

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

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

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39 Alternative measurements STAR preliminary d+Au Same-sign: - A 2 UD > A 2 LR - meets LPV expectation - A 2 < 0 in central collisions Oppo-sign: - aligned (A + A - > 0) - local charge conservation? - A + A - UD > A + A - LR - contradicts LPV expectation? - not dominantly RP-related Different observables have different sensitivities to the charge separation, and suffer different backgrounds. No real reaction plane here!

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40 Outlook With zero net charge, the neutral particles are expected to be much less affected by the electric field. , K s 0 et al. Beam energy below QGP threshold Beam Energy Scan Isobaric couple of spherical nuclei : different magnetic fields: Neodymium(144,60)- Samarium(144,62) et al. body-body U+U collisions Deformed nuclei can provide the collisions with zero magnetic field and large v 2 to test the theory. CP-violating decays + - et al. R. Millo and E. V. Shuryak, arXiv:0912.4894

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41 Back-up

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42 Systematic check: EP resolution