Overview of Exotic Strange Quark Matter Search Experiments

1. Overview of Exotic Strange Quark Matter Search Experiments James Nagle Columbia University CIPANP 2000

2. 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 q q q q What is Quark Matter? 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. q q q q q = q q q

3. 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. Quark MatterStrange Quark Matter u d u d s Energy Level Strange Quark Mass

4. Where to findStrange 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

5. Cosmological and Astrophysical SQM 1. Remnants of the Big Bang 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. 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). 2. Core of Dense Stars Neutron stars may have quark matter core which could be SQM N. Glendenning and J. Scahffer-Bielich, Phys. Rev. C 58, 1298 (1998).

6. q q q q q q q q q q q q q q q q q q q q q p n n L X n L p L 3. Coalescence of SQM 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. A. Baltz et al., Phys. Lett. B, 325, 7 (1994). J.L. Nagle et al., Phys. Rev. C 53, 367 (1996).

7. 4. Quark-Gluon Plasma p Cools by hadron emission at the surface p+ Hot Plasma Preferential emission of anti-strange quarks K+ L Once cooled down, remaining quarks form a meta-stable state of SQM with: (A= 2-100 and |S|=1-100). J. Schaffner et al., J. Phys. G 23, 2107 (1997)., S.A. Chin and A. Kerman, Phys. Rev. Lett. 43, 1292 (1979). 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.

8. u d s s u d 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. H Mass Threshold Unbound, possibly a resonance similar to d* in proton-proton interactions LL Very loosely bound, unclear distinction between H and LL bound state - possibly very short lifetime ~ 1/2 tL Lpp- S-p , S0n Bound H state, with lifetime ~ 10-8 seconds > tL Ln Very deeply bound, only DS=2 decay, long lifetime > 105 seconds nn “For all H masses except those near the LL threshold, we expect a true six-quark bound state.” Donoghue et al., Phys. Rev. D 34, 3434 (1986).

9. What do we know about the H? 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+ + (X- + p) + n K+ + H + n p + A (L + L) + X H + X A + A (L + L) + X H + X 1. Carroll et al., Phys. Rev. Lett. 41, 777 (1978). p + p a K K H 2. Gustafson et al., Phys. Rev. Lett. 37, 474 (1976). p + A a H X 3. Shahbazian et al., Z. Phys. C39, 151 (1988). p + A a HX 4. Alekseev et al., Yad. Fiz. 52, 1612 (1990). n + A a HX 5. Bawolff et al., Ann. Physik Leipzig 43, 407 (1986). p + A a HX 6. Condo et al., Phys. Lett. 144B, 27 (1984). p + A a HX ………….

10. Best Limits to Date Ln Sn Lpp LL “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 DS=1 transitions.” A. Alavi-Harati et al., Phys. Rev. Lett. 84, 2593 (2000). E888 KTeV E224 E836 Let’s look in more detail…. Plot from Ram Ben-David and D. Ashery

11. 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 L nandH S0 n sH < 60 nb E888 sensitivity sH ~ 1.0 mb 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)

12. p + p p + Pt L dN/dy (a.u.) H E888 acceptance Rapidity Experiment 888: Part II E888 limit of sH < 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 sH< 1.2 mb. However, the predicted yield using a p + p type model for coalescence is sH ~ 2 mb. In p + Pt collisions, there is significant strangeness enhancement and even greater enhancement of nearby baryons. The predicted yield should be sH ~ 40 mb. 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).

13. E799-II KTeV Result No candidates. Sensitive to: H L pp- sH < 12 pb KTeV sensitivity sH ~ 1.2 mb model prediction A. Alavi-Harati et al., Phys. Rev. Lett. 84, 2593 (2000). F. Rotondo, Phys. Rev. D 47, 3871 (1993).

14. 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 theLL4H. Look for these results in the near future, and an upgrade proposal (Adam Rusek/Robert Chrien/Tomokazu Fukuda).

15. 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 1/50. Also, replacing a baryon unit with a strange baryon unit is still ~ 1/5. E864

16. Search for SQM with new Z/A NA52 Experiment at CERN-SPS

17. 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).

18. SQM Sensitivity 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 A. Baltz et al., Phys. Lett. B 325, 7 (1994) H. Crawford et al., Phys. Rev. D 45, 857 (1992). H.C. Liu and G.L. Shaw, Phys. Rev. D 30, 1137 (1984).

19. Conclusions and Future • Concept of a deeply bound H dibaryon may be on its last legs. • E906 and other KEK hypernuclei results will play a key role. • There is still a window at around 1/2 tL for a weakly bound H dibaryon or LL bound state. • Or are the productions models really wrong (?) • For A > 2 SQM final limits from fixed target programs available. • In absence of observations, limits of a few 10-9 are reached. • Much harder to find many strange baryons close together than initially predicted. • 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 (?)

20. Lower Transition Rate ? Check transition rate by measuring ingredients and resulting states. Compare: In same region in phase space. Preliminary = 0.162  0.088 E864 E891

21. E910 Lambda Distribution p + Au at 18 GeV Lambda rapidity distribution is shifted towards target rapidity. This trend increases with the number of struck target nucleons nucl-ex/0003010 31 March 2000

22. Double Lambda Hypernuclei • K- + (p) X- + K+ • X- + (p) L + L • L + L + A LL4H + X • LL4H p- + L4He • L4He 3He + p + p-

23. 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 and many others……..

24. n p L L 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 (Dr, Dp) normally adequate to coalescence a deuteron from a proton-neutron pair. Nagle et al., Phys. Rev. C 53, 367 (1996).