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Baryon Strangeness correlatons : signals of a de-confined antecedent

This research paper explores the fluctuations of conserved quantities in heavy-ion collisions and the correlation between baryon and strangeness fluctuations as indicators of a de-confined state of matter. It compares different paradigms such as quasi-particle QGP, hadron gas, bound states, and event generators. The paper concludes with insights from lattice calculations and speculations about the nature of the primordial matter.

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Baryon Strangeness correlatons : signals of a de-confined antecedent

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  1. Abhijit Majumder Nuclear theory group, Lawrence Berkeley National Lab. Baryon Strangeness correlatons : signals of a de-confined antecedent In collaboration with Volker Koch and Jorgen Randrup

  2. OUTLINE Conserved quantities in HIC Fluctuations of conserved quantities The BS of QGP Differentiating the different paradigms: Quasi-particle QGP, Hadron gas, Bound states, Event Generators Conclusions.. Lattice

  3. The general picture in a Heavy-ion collision What do we know ? Rapid longitudinal expansion… 2) Early thermalization, v2, radial flow… 3) High density matter jet quenching, Bjorken estimates 4) No first order phase transition !

  4. - + - - + - - - + + + - + + + + - - - - - - - - + - + + - + + + + + + + - + - + - + - Imagine a conserved charge carried by a particle in the plasma Net charge conserved in a chosen rapidity interval + + + If nothing drastic happens during hadronization

  5. The BS of the QGP! Quantum numbers conserved in Heavy ion collisions: • Baryon number B (exactly) • Charge Q (exactly) • Strangeness S (almost!) • Combinations are also conserved : BS, QS, BQ etc. • Fluctuations of B,Q,S conserved • Fluctuations of products conserved • Should be conserved in a wide rapidity bin!

  6. BS is carried by  Strangeness carriers  Canonical QGP vs. Hadron gas • BS is carried by s, s • Strangeness carriers s, s B and S locked together in a QGP, But not in a hadron gas, x(-3) as quarks have B=1/3, and S=-1 Correlation in B & S Fluctuations of S

  7. The observable Experimentally: measured in the final state, after freezeout with only final state hadrons... Theoretically: calculated in the initial state, when fluctuations set in, using prevalent degrees of freedom...

  8. Say the fluctuations are set in by independent mobile species Assuming Poisson statistics, s2=<n>, G.C. ensemble To calculate replace event average by average over states... Experimentally, have to use method with no Approx.. BS->p + K

  9. Simple estimates In hadron gas phase • In a QGP phase CBS = 1 At T=170MeV, =0 R = 0.66 Almost 50% rise in CBS from hadron gas to QGP

  10. Hadron gas estimate sensitiveto chemical potential and temperature. Estimate along the freeze-out line Increasing the baryon chemical potential, increases baryons. At large m, S is carried by Kaons and –S by L+S

  11. Estimates from the Lattice Need off-diagonal susceptibilities …’s in unquenched QCD Calculated by R.V. Gavai, S. Gupta, Phys.Rev.D66:094510,2002, But in the quenched approximation At T = 1.5 Tc Off-Diagonal susceptibilities are very small compared to diagonal susceptibilities, CBS = 1+ 0.00(3)/0.53(1)

  12. Full QCD, but with 2 flavors, gives similar insight! From C.R. Alton et. al. Phys.Rev.D71:054508,2005

  13. Estimates from a Bound-State-QGP! E. Shuryak, I. Zahed,Phys.Rev.C70:021901,2004;Phys.Rev.D70:054507,2004. QGP is strongly coupled Large scattering cross-sections Multitude of binary bound states And heavy quasi-particle states of quarks and gluons, m~gT Say fluctuations are set in at 1.5Tc qq is not bound at this temperature Contributing states:

  14. Heavy quark, antiquark quasiparticle have C=1 • Quark-antiquark states: 8  like, 24  like (They have no Baryon number) u s + d s + s u + s d These states have C = 0 • Quark gluon states in triplet color representation 36 states, have C = 1 • Quark gluon states in hexaplet color representation considered unbound at T=1.5Tc All together at T=1.5Tc, CBS = 0.61 Similar to Hadron gas estimate…

  15. Estimate from string fragmentation • Very strongly interacting system • Fluctuations set in by string degrees of freedom • Single string fragmentation: JETSET • Heavy-ion collision : HIJING • Study effect of varying acceptance range in rapidity

  16. Final results, from 4 approaches ! At ymax<y<ymin C = 0 All events have B=0 CBS rises and stabilizes at Smaller range of y Still much smaller than Hadron gas estimate Hadron gas, SZ plasma smaller than naïve QGP or Lattice estimate CBS: discerning experimental observable RQMD from S. Huang

  17. Conclusions/problems • Bulk fluctuations of conserved charges can determine the degrees of freedom • E-by-E measurement of CBS can give insight into the primordial matter. • Strangeness and baryonic degrees of freedom are quasi-particulate • No light meson like bound states! • Experimentally, hard to estimate baryon number: neutrons! • Phase transition causes reshuffling of B & S • Contamination by weak decays from heavier states

  18. Speculations! A) Its still hydro-dynamic i) The dynamics is driven by gluons ii) Quark quasi-particles go along for the ride iii) Need alternative means to determine the existence of bound states! B) Its not hydro-dynamic i) Everything is quasi-particulate, ii) Submerged in a repulsive mean field, iii) Expansion driven by mean field !! ?? A. Peshier, B. Kampfer and G. Soff, Phys.Rev. D66:094003,2002. J. P. Blaizot, E. Iancu and A. Rebhan, Phys.Rev. D63:065003,2001.

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