# Presentation: 563581

## Overview of Exotic Strange Quark Matter Search Experiments

- Symposium on Fundamental Issues in
- Elementary Matter
- 25-29 September 2000
- Physikzentrum Bad Honef

- James Nagle

## =

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- q

- QCD allows for bound states of quarks in color-singlet configurations
- Nuclei are not single hadrons, but bound states of individual nucleons
- Quark matter composed of up and down quarks for (A>1) is known
- to be unstable, otherwise normal nuclei would decay into such
- quark matter.

## What is Strange Quark Matter?

- Strange quark matter composed of up, down and strange quarks may be meta-stable or even stable in bulk.
- States have a reduced Fermi energy, reduced Coulomb, no fission.
- Thus SQM states could range in size from A=2 to A > 106.
- Witten proposed SQM could even be the ground state of nuclear matter and could exist in bulk as remnants of the Big Bang.

- u

- d

- u

- d

- s

- Energy Level

- Strange Quark Mass

_**Quark Matter**_**    **_**Strange Quark Matter**_

## Where to findStrange Quark Matter?

**1.  Remnants from the early universe**
**2.  Core of dense stars**
**3.  Created by coalescence of multiple strange baryons**
**4.  Created via a quark-gluon plasma formed in **
**	****relativistic heavy ion collisions**

## Cosmological and Astrophysical SQM

- 	SQM left over from the Big Bang
- 	could be seen in cosmic rays and
- 	may have a 10-7 concentration by mass
- 	in the Earth’s crust.
- 	Many searches with _null _results.

**Cosmological and Astrophysical SQM**

**2.  Core of Dense Stars**
- 	Neutron stars may have quark matter core which could be SQM

- E. Witten, Phys. Rev. D 30, 272 (1984).
- A. DeRujula and S.L. Glashow, Nature 312, 20 (1984).
- J.D. Bjorken and L.D. McLerran, Phys. Rev. D 20, 2353 (1979).

- N. Glendenning and J. Scahffer-Bielich, Phys. Rev. C 58, 1298 (1998).

## 3.  Coalescence of SQM

- A. Baltz, C. Dover et al., Phys. Lett. B, 325, 7 (1994).

- In p + p, p + A, A + A collisions, at freeze-out baryons and strange         baryons can coalesce to form nuclei and hypernuclei.

- If strange quark matter states are more stable than these hypernuclei, then the state can make a transition to form SQM.

## 4.  Quark-Gluon Plasma 

- H. Liu and G.L. Shaw, Phys. Rev. D 30, 1137 (1984), C.Greiner *et al.* Phys. Rev. Lett. 58 (1987) 1825.
- C.Greiner and H. Stocker, Phys. Rev. D 44 (1991) 3517.

- Cools by hadron emission
- at the surface

- p

- Preferential emission of
- anti-strange quarks

- Once cooled down, remaining quarks form a
- meta-stable state of SQM with:
- 				        (**A= 2-100 and |S|=1-100**).

**4.  Quark-Gluon Plasma **

## H-dibaryon

- The H-dibaryon is a six-quark color singlet hadron.
- It would be the lightest strange quark matter state, and
- there is no theoretical consensus about its mass.

******p********-**

****

**********p , ********0****n**

******n**

**nn**

- Very deeply bound, only S=2 decay, long lifetime > 105 seconds

- Unbound, possibly a resonance similar to d* in proton-proton interactions

- Very loosely bound, unclear distinction between H and  bound state
- 	- possibly very short lifetime ~ 1/2 

- Bound H state, with lifetime ~ 10-8 seconds > 

- “For all H masses except those near the  threshold, we expect a true six-quark bound state.”
- 						Donoghue et al., Phys. Rev. D 34, 3434 (1986).

- H Mass Threshold

## What do we know about the H?

- 1.  Carroll *et al.,* Phys. Rev. Lett. 41, 777 (1978).		p + p   K K H
- 2.  Gustafson *et al., *Phys. Rev. Lett. 37, 474 (1976).	p + A  H X
- 3.  Shahbazian *et al.,* Z. Phys. C39, 151 (1988).		p + A  HX
- 4.  Alekseev *et al.,* Yad. Fiz. 52, 1612 (1990).		n + A  HX
- 5.  Bawolff *et al.,* Ann. Physik Leipzig 43, 407 (1986).	 + A HX
- 6.  Condo et al., Phys. Lett. 144B, 27 (1984).		p + A HX
-      .............

- A.  **E836****	****BNL-AGS**
**      ****E224****	****KEK**
- B.  **E888****	****BNL-AGS**
**      ****KTeV****	****FNAL**
-       E910	BNL-AGS
- C.  E810 	BNL-AGS
-       E896	BNL-AGS

- K-  +  3He       K+  +  (  +  p)  +  n
-                        K+  +      +  n

- p   +     A        (  +  )   + X
-                              H        + X

- A   +     A        (  +  )   + X
-                               H         + X

## Best Limits to Date

- “To conclude, in the context of published models, our [KTeV] result .... in conjunction with the result from experiment E888, rules out the [H dibaryon] model proposed by Donoghue *et al.* for all S=1 transitions.”
- A. Alavi-Harati *et al*., Phys. Rev. Lett. 84, 2593 (2000).

- 

- p

- n

- n

**E888**
**KTeV**
**E224**
**E836**

- Plot from Ram Ben-David and D. Ashery

- Let’s look in more detail....

## Experiment 888

- Originally E888 had two possible H candidates, but further studies support the conclusion that they are consistent with known backgrounds.
- Sensitive to:      **H      ******** n****   **and**  ****H      ********0**** n**

**********   ****< 60 nb**
- E888 sensitivity
**********   ****~ 1.0 ********b**
- model prediction

- J. Belz et al., Phys. Rev. Lett. 76, 3277 (1996).
- J. Belz et al., Phys. Rev. C 56, 1164 (1997).
- Cousins et al., Phys. Rev. D 56, 1673 (1997)

## Experiment 888:  Part II

- E888 limit of ******H**** < 60 nb** assumed H production peaked at midrapidity (like p+p).
- Using transport model RQMDv2.3 shows an H distribution shifted towards target rapidity as suggested by Cole *et al*.  This reduces the acceptance substantially and yields a limit of ******H** **< 1.2 ********b**.

- However, the predicted yield using a p + p type model for coalescence is ******H**** ~ 2 ********b**.
- In p + Pt collisions, there is significant strangeness enhancement and even greater enhancement of nearby baryons.  The predicted yield should be ******H**** ~ 40 ********b**.
- Thus the ratio (limit/prediction) is still roughly the same.

- Nagle *et al*., Phys. Rev. C 53, 367 (1996).
- Cole *et al*., Phys. Lett. B 350, 147 (1995).

## E910 Lambda Distribution

- nucl-ex/0003010 31 March 2000

****** ****distribution is shifted towards target rapidity.  **

- p  +  Au   at 18 GeV

**Increasing number of**
**collisions by the **
**incoming proton**

## E799-II KTeV Result

- No candidates.
- Sensitive to:      **H      ******** p**********

- A. Alavi-Harati *et al*., Phys. Rev. Lett. 84, 2593 (2000).

**********   ****< 12 pb**
- KTeV sensitivity

## Checking the Calculations

**Checking the Calculations**

- Rapidity

- Invariant Yield (a.u.)

****

********

**p + Be at 800 GeV/c**

- Original Model Calculation by Frank Rotondo.
-      F. Rotondo, Phys. Rev. D 47, 3871 (1993).
- Re-checked using transport model RQMD and coalescence.  Agrees with previous prediction within a factor of 2.

**********   ****< 12 pb**
- KTeV sensitivity
**********   ****~ 1.2 ********b**
- model prediction

**KTeV acceptance**

## E906 - Hypernuclei

**E906 - Hypernuclei**

- If one observes a double-lambda hypernucleus that decays by sequential weak decay, then it rules out all but the most weakly bound H dibaryon.
- There are three isolated previous candidates - but the results are not consistent.

- Recently E906 at the BNL-AGS reports a clear signal above background in the region where one expects to find the ******4****H**.
- Look for these results in the near future, and an upgrade proposal
- (Adam Rusek/Robert Chrien/Tomokazu Fukuda).

## Double Lambda Hypernuclei

**K****-**** +  (p)      ********-    ****+  K****+**

******-  ****+  (p)       ********  +  ******

******  ****+  ********    +   A         ********4****H  +  X**

******4****H      ********-**** + ********4****He**

******4****He       ****3****He + p + ********-**** **

## Beyond the H (|S| >2)

- Larger states of SQM can only be created with relativistic heavy ion collisions.
- However, there are some issues:
- 	**Too hot** (higher energy)
- 		- difficult to get multiple baryons close enough to fuse
- 	**Too cool** (lower energy)
- 		- not enough strangeness production

- AGS energies may be optimal, but there is still a large penalty for coalescence 1/48.  Also, replacing a baryon unit with a strange baryon unit was predicted to be another ~ 1/5.

- E864

## Search for SQM with new Z/A

- NA52 Experiment at CERN-SPS

## No Evidence for SQM

- No remaining candidates and thus set upper limits.
**E886  (AGS)** Adam Rusek
**E878  (AGS)** Mike Bennett
**E864  (AGS)** K.Barish, M.Munhoz, 	                  S.Coe, JN
**E864  (AGS)** Z.Xu, G.V.Buren,
-                                       R. Hoverstein
**NA52(CERN)** R. Klingenberg, 		  K.Pretzel

**Lifetimes > 50 ns**

- T.A.Armstrong et al., Phys. Rev. Lett. 79, 3612 (1997)
- T.A.Armstrong et al., Nucl. Phys A 625, 494 (1997)
- D. Beavis et al., Phys. Rev. Lett. 75, 3078 (1995)
- A. Rusek et al., Phys. Rev. C 54, R15 (1996).
- R. Klingenberg et al., Nucl. Phys. A, 306c (1996).

**No Evidence for SQM**

## SQM Sensitivity

- H. Crawford *et al.,* Phys. Rev. D 45, 857 (1992).
- H.C. Liu and G.L. Shaw, Phys. Rev. D 30, 1137 (1984).

**Most plasma predictions ****	****	**_**ruled out**_** by data**
**Sensitivity for SQM via coalescence up to states **
**       ****A=6-7 , |S|=2-3**

**Nucleosynthesis Models**

**Quark Plasma Models**

**E864 Upper Limits**

**SQM Sensitivity**

## E864:  Hypernuclei

- If    “SIGNAL”
-      invariant yield  (2.6 _+_ 1.2) 10-4 c2/Gev2
-                           S  =  1/28
-  If  “LIMIT”
-      90% CL sensitivity  2.5 10-4 c2/Gev2
**                          ********S****  <   1/30**

- Sotiria Batsouli, Yale University

-   (2.991 GeV)

- 

- e

- J

- .R.(e)= 25%

**Y(A,|S|) = C x (1/48)****A**** x (********s****)****|S|**

## Unstable Nuclei

**5****Li******** ****4****He + p   **(c ~ 100 fm/c)

**Follows scaling law**

## Finite Size Effects

- Heinz, Scheibl, Phys. Rev. C59,1585 (1998).

-        = 5 fm             B.E.( - 2H) = 0.13 Mev
- e :           = 1.74 fmE. = 8 MeV
- Assume         ( 2H +) with  b =         d   9.8 fm
-                   e    ( 2H +p) with   b =         pd   2.6 fm
- Using R||  , R_ | _   from E917, E895

**Thus, accounting for lower abundance of ********‘s and finite size effects leaves **
**an additional penalty of 0.5**

## Antideuterons

**Corrected for large contribution of antilambdas to measured antiprotons**

- T.A. Armstrong, Phys. Rev. Lett. 85, 2685 (2000).

## E864 Results

- Antideuteron Yields at the AGS and Coalescence Implications, Phys. Rev. Lett. 85, 2685 (2000).
- Measurements of Light Nuclei Production in 11.5A GeV/c Au + Pb heavy-ion collision, Phys.Rev.C61:06490 (2000).
- Mass Dependence of Light-Nucleus Production in Ultrarelativistic Heavy-Ion Collisions, Phys. Rev. Lett 83, 5431 (1999).
- Search for neutral strange quark matter in high energy heavy ion collisions, Phys Rev C 59, R1829 (1999).
- Antinproton production and antideuteron production limits in relativistic heavy ion collisions, Phys Rev C 59, 2699 (1999).
- Measurements of neutrons in 11.5A GeV/c Au + Pb heavy-ion collisions, Phys Rev C 60, 064903 (1999).
- Antiproton Production in 11.5 AGeV/c Au+Pb Nucleus-Nucleus Collisions, Phys Rev Lett 79, 3351 (1997).
- Search for Charged Strange Quark Matter in 11.5 AGeV/c Au+Pb Collisions, Phys Rev Lett 79, 3612 (1997).
- Search for Exotic Strange Quark Matter in High Energy Nuclear Reactions Nucl Phys A625 (1997) 494-512.

## Conclusions and Future

-  E906 and other KEK hypernuclei results will play a key role.
-  There is still a window at around 1/2  for a weakly bound H 	dibaryon or  bound state.
-  Or are the productions models really wrong (?)
-  For A > 2 SQM almost final limits from fixed target programs.
-  In absence of observations, limits of a few **10****-9** are reached.
-  Much harder to find many strange baryons close together than 	initially predicted.  Hypernuclei are also suppressed (?)
-  RHIC is next step for heavy ion physics, but not SQM physics
-  Future experiments looking for _**multi-strange hypernuclei**_ and 	shorter lifetime SQM at Japanese Hadron Facility (?)

**Conclusions and Future**

## Good Discussions

- I want to acknowledge useful and fun discussions in preparing for
- this talk with
- 		Frank Rotondo
- 		Adam Rusek
- 		Bill Zajc
- 		Sebastian White
- 		Bob Cousins
- 		Josh Klein
- 		Ram Ben-David
- 		Jurgen Schaffner-Bielich
- 		Jack Sandweiss
- 		Sotiria Batsouli
- 		     and many others........

## How does coalescence work?

- Deuteron coalescence in p + A collisions
- Deuteron coalescence in A + A collisions

- _Model Predictions for H dibaryon:_
- How often are all the ingredients within the phase space (r, p) normally adequate to coalescence a deuteron from a proton-neutron pair.

- Nagle *et al*., Phys. Rev. C 53, 367 (1996).

## Other Hypernuclei

- e :             = 1.4 fmE. = 29 MeV
-              _Size effects_ _not important_
- But  weakly bound   breaks easily
- 
- ********************
-  strong unstable nucleus
-  (2J + 1) = 4 ,     (2J + 1) = 10
- Then, not much additional penalty for strangeness.

- 

- 

- MeV

- J
- J

-   (3.92 GeV)

- .R.(e)= 50%