Overview of Exotic Strange Quark Matter

Search Experiments

Overview of Exotic Strange Quark Matter

Search Experiments

James NagleColumbia University

CIPANP 2000

What is Quark Matter?What is Quark Matter?

q q qq

q

qq

qq

q

q

qq

qq

q

q

qq

q

qq

q

qq

q

qq

qq

q

q

qq

qq

q

q

qq

q

qq

q

qq

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 knownto be unstable, otherwise normal nuclei would decay into such quark matter.

What is Strange 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 du d s

Ene

rgy

Lev

el

Strange Quark Mass

Quark Matter Strange Quark Matter

Where to findStrange Quark Matter?

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

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.

Cosmological and Astrophysical SQM

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 SQM3. Coalescence of SQM

n

nn p

p

A. Baltz et al., Phys. Lett. B, 325, 7 (1994).J.L. Nagle et al., Phys. Rev. C 53, 367 (1996).

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.

qq

qq

q

q

qq

qq

q

q

qq

q

qq

q

qq

q

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.

Cools by hadron emissionat the surface

Hot Plasma

K+

p +

)( suK ssPreferential 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 4. Quark-Gluon Plasma

H-dibaryonH-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 , 0n

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 >

d

dsu

u s

“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?What do we know about the H?

1. Carroll et al., Phys. Rev. Lett. 41, 777 (1978). p + p K K H2. Gustafson et al., Phys. Rev. Lett. 37, 474 (1976). p + A H X3. Shahbazian et al., Z. Phys. C39, 151 (1988). p + A HX 4. Alekseev et al., Yad. Fiz. 52, 1612 (1990). n + A HX5. Bawolff et al., Ann. Physik Leipzig 43, 407 (1986). + A HX6. 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 DateBest 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).

pnn

E888KTeVE224E836

Plot from Ram Ben-David and D. Ashery

Let’s look in more detail….

Experiment 888Experiment 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 nbE888 sensitivity

~ 1.0 bmodel 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 IIExperiment 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.

Rapidity

dN/d

y (a

.u.)

p + pp + Pt

E888 acceptance

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).

E799-II KTeV ResultE799-II KTeV Result

No candidates.

Sensitive to: H p

< 12 pbKTeV sensitivity

~ 1.2 bmodel prediction

A. Alavi-Harati et al., Phys. Rev. Lett. 84, 2593 (2000). F. Rotondo, Phys. Rev. D 47, 3871 (1993).

E906 - HypernucleiE906 - 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

4H.

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

Beyond the H (|S| >2)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

Search for SQM with new Z/ASearch for SQM with new Z/A

NA52 Experiment at CERN-SPS

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 SQMNo Evidence for SQM

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).

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 SensitivitySQM Sensitivity

• 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 for a weakly bound H

dibaryon or 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 (?)

Conclusions and FutureConclusions and Future

Lower Transition Rate ?

Check transition rate by measuring ingredients and resulting states.

E891E864

Compare:

In same region in phase space.

np

H3

npp

He

3= 0.162 0.088

Preliminary

E910 Lambda DistributionE910 Lambda Distribution

nucl-ex/0003010 31 March 2000

Lambda rapidity distribution is shifted towards target rapidity.

This trend increases with the number of struck target

nucleons

p + Au at 18 GeV

K- + (p) - + K+

- + (p) +

+ + A 4H + X

4H - + 4He

4He 3He + p + -

Double Lambda HypernucleiDouble Lambda Hypernuclei

Good DiscussionsGood Discussions

I want to acknowledge useful and fun discussions in preparing forthis talk with

Frank RotondoAdam RusekBill ZajcSebastian WhiteBob CousinsJosh KleinRam Ben-DavidJurgen Schaffner-BielichJack Sandweiss

and many others……..

How does coalescence work?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.

p n

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