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The hypernuclei program at RHIC-STAR

The hypernuclei program at RHIC-STAR. Jinhui Chen for the STAR Collaboration Shanghai Institute of Applied Physics, CAS. The 11 th International Conference on Hypernuclear and Strange Particle Physics " HYP2012 " October 1 - 5, 2012 Barcelona, Spain. Outline.

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The hypernuclei program at RHIC-STAR

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  1. The hypernuclei program at RHIC-STAR Jinhui Chenfor the STAR Collaboration Shanghai Institute of Applied Physics, CAS The 11th International Conference on Hypernuclear and Strange Particle Physics " HYP2012 " October 1 - 5, 2012 Barcelona, Spain

  2. Outline Introduction& Motivation Our measurement • Hypertriton invariant yield • Lifetime measurement • H-dibaryon search Conclusion

  3. Introduction & Motivation Hypernuclei: ideal lab for YN and YY interaction – Baryon-baryon interaction with strangeness sector – Input for theory describing the nature of neutron stars Binding energy and lifetime are sensitive to the Y-N interaction Previous measurement on hypertriton lifetime shows large statistical uncertainties Search for H-dibaryon via L-L correlation, provide sensitive constrains on Y-Y interaction

  4. Hypertriton lifetime measurement Previous measurement (before 1973) Use nuclear emulsion or bubble chamber Accepted events: less than 80 STAR 2010 Measurement STAR 2012 Measurement Previous measurement STAR Collaboration, Science 328 (2010)58 It is promising to obtain an improved lifetime measurement using the new data

  5. initial stage QGP and hydrodynamic expansion pre-equilibrium hadronization and freeze-out Relativistic heavy-ion collisions • Initial condition of collisions • New state of matter : QGP • Hadronization and hadronic interaction RHIC creates hot and dense matter, containing dozens of hyperons in central events : ideal source of hypernuclei studies. RHIC white paper: Nucl. Phys. A 757

  6. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS Relativistic Heavy Ion Collider (RHIC)

  7. STAR Detector TPC: effectively 3-D ionization camera with over 50 million pixels. STAR: a complex set of various detectors, a wide range of measurements and a broad coverage of different physics topics. STAR-TPC: NIMA 499 (2003) 659 STAR-detector: NIMA 499 (2003) 624

  8. Event display A beautiful event in the STAR TPC that includes the production and decay of a antihypertriton candidate. (Data taken from Run4 Au+Au 200GeV MB collision)

  9. Datasets and track selection Datasets and event statistics • Analysis method: secondary vertex finding technique • Identify 3He and p candidate • Find the V0 position from daughters pairing • Plot the invariant mass dis. of daughters • Combinatorial background analysis

  10. Daughters identification STAR preliminary Clean p (<0.65GeV) and 3He (>2GeV) identification from TPC

  11. signal from the data Statistics: Run7+Run10+Run11 MB+Central, ~610M events bin width 2MeV bin width 4MeV STAR preliminary STAR preliminary Signal observed from the data (bin-by-bin counting [2.986,2.996]GeV): 602±63, significance:9.6s Background estimation: rotated background

  12. Signal in BES(1) Hypertriton signal from STAR BES at =7.7, 11.5, 19.6GeV STAR preliminary STAR preliminary Details in the analysis

  13. Signal in BES(2) Hypertriton signal from STAR BES at =27, 39, 200GeV STAR preliminary STAR preliminary Details in the analysis

  14. Measure the lifetime STAR preliminary STAR preliminary STAR preliminary Measure the hypertriton signal in different L/βγ bins: 2-5-8-11-41cm Combined datasets: run10 7.7,11.5,39,200GeV MB, run10 200GeV central, run11 19.6, 27GeV MB STAR preliminary

  15. New hypertriton lifetime result STAR preliminary STAR preliminary STAR 2012 preliminary result: STAR 2010+2012 combined fit:

  16. L-L correlation function Correlation functions for 0-40% Au+Au collisions at = 200GeV • Type of ΛΛ interaction: • Meson exchange models: Nijmegen model D, F, Soft Core (89, 97) • Quark cluster model interaction: fss2 • Phenomenological model: Ehime •  interaction  attractive • Inclusive  correlations: feed down contributions included in theoretical models. STAR preliminary Shah IV Mon.

  17. L-L correlation function A. Ohnishi, HHI workshop 2012/2 Scattering length (a0) is negative in most fits Current fit from different potential models to data gives indication towards non-existence of bound H-dibaryon Shah IV Mon.

  18. Conclusion Over 600 hypertriton and antihypertriton particles are reconstructed in heavy-ion collisions at RHIC, with a significance of 9.6s The hypertriton and antihypertriton signals are reconstructed for each RHIC BES energy A statistically improved lifetime ps is obtained The H-dibaryon search: current fit from different potential models to data gives no indication towards the existence of bound H-dibaryon

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