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

CBM-China Meeting, Tsinghua U., Nov. 2-5, 2009 1Zebo Tang, USTC

Zebo TangUniversity 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) A case of low energy scan

Conclusion and Outlook

H3Λ H3

Λ


The first hypernucleus was discovered by Danysz The first hypernucleus was discovered by Danysz and Pniewski in 1952. It was formed in a cosmic and Pniewski in 1952. It was formed in a cosmic ray interaction in a balloon-flown emulsion plate. ray interaction in a balloon-flown emulsion plate. M. Danysz and J. Pniewski, M. Danysz and J. Pniewski, Phil. Mag. 44 (1953) 348Phil. Mag. 44 (1953) 348

What are hypernuclei（超核） ?

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: B=130±50 KeV; r~10fm

• Production rate via coalescence at RHIC depends on overlapping wave functions of n+p+in final state

• Important first step for searching for other exotic hypernuclei (double-)

No one has ever observed any antihypernucleus

Nucleus which contains at least one hyperon in addition to nucleons.

)(

)(3

3

pnH

pnH


From Hypernuclei to Neutron Stars

hypernuclei -B Interaction Neutron Stars

S=-1

S=-2

S=-0

Several possible configurations of Several possible configurations of Neutron StarsNeutron Stars– Kaon condensate, hyperons, strange quark matterKaon condensate, hyperons, strange quark matter

SingleSingle and and doubledouble hypernuclei in the laboratory: hypernuclei in the laboratory: – study thestudy the strange sectorstrange sector of the baryon-baryon interactionof the baryon-baryon interaction– provide info on EOS of neutron starsprovide 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

Saito, HYP06


Can we observe hypernuclei at RHIC?

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?

Low energy and cosmic ray experiments (wikipedia): hypernucleus production via

– or K capture by nuclei

– the direct strangeness exchange reaction

hypernuclei observed – energetic but delayed decay,– measure momentum of the K and mesons

[1] AGS-E864, Phys. Rev. C70,024902 (2004)


STAR Detector

MRPC ToF barrelMRPC ToF barrel100% for run 10100% for run 10

PMD

FPD

FMS

EMC barrel

EMC End Cap

DAQ1000DAQ1000

Take data FGT

Complete

Ongoing

MTD (BNL LDRD)

R&DHFT

TPC

Only TPC for this analysis


Light nuclei at STARSTAR, arXiv:0909.0566

Clearly identified using dE/dx (TPC)Plentiful of light (especially anti)-nuclei

RHIC: the best antimatter machine!)(5.0/

)(10/

10/

33

333

1133

RHICHeeH

SPSHeeH

HeeH


Hyperon at STAR

STAR PRL 89 (2002) 132301

Secondary vertex finding technique

Spatial resolution w/o silicon (TPC only):Primary vertex: few hundred m in Au+AuSecondary vertex: few mm

Excellent capability for strange particle reconstruction


Data-set and track selection

Data-set used, Au+Au 200 GeV

~67M Run7 MB,

~23M Run4 central,

~22M Run4 MB,

|VZ| < 30cm

Track quality cuts, global track

nFitsPts > 25

nFitsPts/Max > 0.52

nHitsdEdx > 15

Pt > 0.20, || < 1.0

Pion n-sigma (-2.0, 2.0)

DCA of v0 to PV < 1.2 cm

DCA of to PV > 0.8 cm

DCA of to 3He < 1.0 cm

Decay length > 2.4 cm

3H mesonic decay, m=2.991 GeV, B.R. 25%;

HeH

eHH33

33


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

)/

/ln( Bichsel

dxdE

dxdEZ


A candidate event at STARRun4 (2004) 200 GeV Au+Au collision


signal from the data

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

H3Λ

11595810/2168*157He/HeH*H 333Λ

3Λ

STAR Preliminary


Signal observed from the data (bin-by-bin counting): 70±17;

Mass: 2.991±0.001 GeV; Width (fixed): 0.0025 GeV;

signal from the dataH3Λ

STAR Preliminary


Combine hypertriton and antihypertriton signal: 225±35

Combined signals

STAR Preliminary

This provides a >6 signal for discovery


Lifetime

ps27182 8945 Our data:

Consistency check on lifetime yields ()=267±5 ps [PDG: 263 ps].

STAR Preliminary

STAR Preliminary


Comparison to world data

Lifetime related to binding energy Theory input: the 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).

STAR Preliminary


Measured invariant yields and ratios

)/()/(/

)/)(/)(/(/233

33

nnppHeeH

nnppHH

In a coalescence picture:

0.45 ~ (0.77)3

STAR Preliminary


Yields/ratios as a measure of correlation

uud

uddudu

uud

uddudd

uud

udduds3He t 3

H

Wave function overlaping CoalescenceYield depends on the correlation in both coordinate and momentum space

(3He, t, 3H)(u, d, s)+4u+4d

A simple and perfect system!

3H/3He ratio Lambda-nucleon correlation

3He/t ratio charge-baryon correlation


Yields/ratios as a measure of correlation

measurements related to local (strangeness, baryon) - baryon

correlation

Lattice Simulations of (all strangeness) - (all baryon) correlation

at zero chemical potential

STAR Preliminary


Search for onset of deconfinement

Hypertriton onlySTAR: DAQ1000+TOF

Beam energy 200(30—200) GeV ~17 (10—30)GeV

~5 (5-10) GeV

Minbias events# (5)

300M ~10—100M ~1—10M

Penalty factor 1448 368 48

3He invariant yields 1.6x10-6 2x10-4 0.01

3H/3He assumed 1.0 0.3 0.05

S. Zhang et al., arXiv:0908.3357 [nucl-ex]

AMPT (string melting)

(default)


/ 3He is 0.82 ± 0.16. No extra penalty factor observed for hypertritons at RHIC. Strangeness phase space equilibrium

The / 3He ratio is determined to be 0.89 ± 0.28, and

The lifetime is measured to be

Consistency check has been done on analysis; significance is ~5

has been observed for 1st time; significance ~4.

Conclusions

H3Λ

H3Λ

H3Λ H3

Λ

H3Λ

H3Λ

The / ratio is measured as 0.49±0.18, and

3He / 3He is 0.45±0.02, favoring the coalescence picture.

ps27182 8945


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

3Hd+p+ channel measurement: d-identification via TOF.

Search for other hypernucleus: 4H, 4

He, 4H, 3

H,

Search for anti-

RHIC: best antimatter machine ever built


Extend to the sector of strangeness and antimatter


Hypernucleus at CSR energy

C+C

1 GeV

C+C

2 GeV

Ca+Ca

1 GeV

Ca+Ca

2 GeV

p 11.986 11.692 39.940 37.758

0.0001 0.0079 0.0012 0.03993He 0.01 0.01 0.15 0.113H 3e-8 7e-7 1e-6 1e-5

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


Hypernucleus at higher energy

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

Smaller penalty factor, higher strangeness production rate


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 DANE• 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

Basic map from Saito, HYP06

International Hyper-nuclear network

BNL• Heavy ion beams• Anti-hypernuclei • Single -hypernuclei• Double -hypernuclei

CBM?

CSR?


Acknowledgement

Thank my STAR Collaborators for providing the perfect detectors and exciting results!

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

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