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Zebo Tang University of Science and Technology of China (USTC)

Hypernucleus production at RHIC. Introduction and Motivation Evidence for first antihypernucleus and signal ( for discovery ) Mass and lifetime measurement Production rate and ratios Yields as a measure of correlation ( coordinate and momentum space)

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Zebo Tang University of Science and Technology of China (USTC)

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  1. Hypernucleus production at RHIC • Introduction and Motivation • Evidence for first antihypernucleus • and signal (for discovery) • Mass and lifetime measurement • Production rate and ratios • Yields as a measure of correlation (coordinate and momentum space) • A case of low energy scan • Conclusion and Outlook Zebo Tang University of Science and Technology of China (USTC) CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  2. What are hypernuclei（超核）? Nucleus which contains at least one hyperon in addition to nucleons. Hypernuclei of lowest A • Y-N interaction: a good window to understand the baryon potential • Binding energy and lifetime are very sensitive to Y-N interactions • Hypertriton: DB=130±50 KeV; r~10fm • Production rate via coalescence at RHIC depends on overlapping wave functions of n+p+Lin final state • Important first step for searching for other exotic hypernuclei (double-L) The first hypernucleus was discovered by Danysz and Pniewski in 1952. It was formed in a cosmic ray interaction in a balloon-flown emulsion plate. M. Danysz and J. Pniewski, Phil. Mag. 44 (1953) 348 No one has ever observed anyantihypernucleus CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  3. S=-2 S=-1 S=-0 From Hypernuclei to Neutron Stars • hypernuclei L-B Interaction Neutron Stars Saito, HYP06 Several possible configurations of Neutron Stars • Kaon condensate, hyperons, strange quark matter Singleand doublehypernuclei in the laboratory: • study thestrange sectorof the baryon-baryon interaction • provide info on EOS of neutron stars J.M. Lattimer and M. Prakash, "The Physics of Neutron Stars", Science 304, 536 (2004) J. Schaffner and I. Mishustin, Phys. Rev. C 53 (1996): Hyperon-rich matter in neutron stars CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  4. Can we observe hypernuclei at RHIC? • Low energy and cosmic ray experiments (wikipedia): • hypernucleus production via • L or Kcapture by nuclei • the direct strangeness exchange reaction hypernuclei observed • energetic but delayed decay, • measure momentum of the K and p mesons • In high energy heavy-ion collisions: • nucleus production by coalescence, characterized by penalty factor. • AGS data[1] indicated that hypernucleus production will be further suppressed. • What’s the case at RHIC? [1] AGS-E864, Phys. Rev. C70,024902 (2004) CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  5. STAR Detector MTD (BNL LDRD) EMC barrel MRPC ToF barrel 100% for run 10 EMC End Cap FMS FPD TPC Only TPC for this analysis PMD Complete Ongoing DAQ1000 Take data HFT FGT R&D CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  6. Light nuclei at STAR STAR, arXiv:0909.0566 Clearly identified using dE/dx (TPC) Plentiful of light (especially anti)-nuclei RHIC: the best antimatter machine! CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  7. Hyperon at STAR Spatial resolution w/o silicon (TPC only): Primary vertex: few hundred mm in Au+Au Secondary vertex: few mm Secondary vertex finding technique STAR PRL 89 (2002) 132301 Excellent capability for strange particle reconstruction CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  8. Data-set and track selection 3LH mesonic decay, m=2.991 GeV, B.R. 25%; • Track quality cuts, global track • nFitsPts > 25 nFitsPts/Max > 0.52 • nHitsdEdx > 15 • Pt > 0.20, |h| < 1.0 • Pion n-sigma (-2.0, 2.0) • 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 • Data-set used, Au+Au 200 GeV • ~67M Run7 MB, • ~23M Run4 central, • ~22M Run4 MB, • |VZ| < 30cm CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  9. 3He & anti-3He selection • Select pure 3He sample: -0.2<Z<0.2 & dca <1.0cm & p >2 GeV • 3He: 2931(MB07) + 2008(central04) + 871(MB04) = 5810 • Anti-3He: 1105(MB07) + 735(central04) + 328(MB04) = 2168 CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  10. A candidate event at STAR Run4 (2004) 200 GeV Au+Au collision CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  11. signal from the data STAR Preliminary • background shape determined from rotated background analysis; • Signal observed from the data (bin-by-bin counting): 157 ± 30 ; • Projection on antihypertriton yields: constraint on antihypertriton yields without direct observation CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  12. signal from the data STAR Preliminary • Signal observed from the data (bin-by-bin counting): 70±17; • Mass: 2.991±0.001 GeV; Width (fixed): 0.0025 GeV; CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  13. Combined signals Combine hypertriton and antihypertriton signal: 225±35 STAR Preliminary This provides a >6s signal for discovery CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  14. Lifetime STAR Preliminary STAR Preliminary • Our data: • Consistency check on L lifetime yields t(L)=267±5 ps [PDG: 263 ps]. CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  15. Comparison to world data STAR Preliminary • Lifetime related to binding energy • Theory input: the L is lightly bound in the hypertriton [1] R. H. Dalitz, Nuclear Interactions of the Hyperons (Oxford Uni. Press, London, 1965). [2] R.H. Dalitz and G. Rajasekharan, Phys. Letts. 1, 58 (1962). [3] H. Kamada, W. Glockle at al., Phys. Rev. C 57, 1595(1998). CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  16. STAR Preliminary Measured invariant yields and ratios In a coalescence picture: 0.45 ~ (0.77)3 CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  17. uud 3LH uds 3He t udd Yields/ratios as a measure of correlation Wave function overlaping Coalescence Yield depends on the correlation in both coordinate and momentum space (3He, t, 3LH)(u, d, s)+4u+4d A simple and perfect system! • 3LH/3He ratio  Lambda-nucleon correlation • 3He/t ratio  charge-baryon correlation uud uud udu udd udd udd CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  18. Yields/ratios as a measure of correlation STAR Preliminary measurements related to local (strangeness, baryon) - baryon correlation Lattice Simulations of (all strangeness) - (all baryon) correlation at zero chemical potential CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  19. Search for onset of deconfinement (string melting) AMPT (default) S. Zhang et al., arXiv:0908.3357 [nucl-ex] Hypertriton only STAR: DAQ1000+TOF CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  20. The / ratio is measured as 0.49±0.18, and 3He / 3He is 0.45±0.02, favoring the coalescence picture. • The / 3He ratio is determined to be 0.89 ± 0.28, and Conclusions • has been observed for 1st time; significance ~4s. • Consistency check has been done on analysis; significance is ~5s • The lifetime is measured to be / 3He is 0.82 ± 0.16. No extra penalty factor observed for hypertritons at RHIC. Strangeness phase space equilibrium CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  21. Outlook Lifetime: • –data samples with larger statistics (~factor 10 more within a few years) Production rate: –baryon-strangeness correlation – a case for energy scan – establish 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-a RHIC: best antimatter machine ever built CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  22. Extend to the sector of strangeness and antimatter CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  23. Hypernucleus at CSR energy Song Zhang (SINAP), ART + Coalescence 100 in 100M Ca+Ca @ 1 GeV (~ Au+Au @ RHIC top energy) But in few seconds Basic detectors: Dipole, tracking, TOF and neutron wall CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  24. Hypernucleus at higher energy Smaller penalty factor, higher strangeness production rate A. Andronic, P. Braun-Munzinger, J. Stachel, Nucl. Phys. A 772 (2006) 167. P. Braun-Munzinger, J. Stachel, J. Phys. G 21 (1995) L17 A. Andronic: SQM09 CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  25. International Hyper-nuclear network • PANDA at FAIR • 2012~ • Anti-proton beam • Double -hypernuclei • -ray spectroscopy • SPHERE at JINR • Heavy ion beams • Single -hypernuclei CBM? • HypHI at GSI/FAIR • Heavy ion beams • Single -hypernuclei at • extreme isospins • Magnetic moments • MAMI C • 2007~ • Electro-production • Single -hypernuclei • -wavefunction CSR? • 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 Basic map from Saito, HYP06 CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

  26. Thank my STAR Collaborators for providing the perfect detectors and exciting results! Acknowledgement CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009

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