IHEP October 15 2004 Heavy Quarkonium in QuarkGluon

IHEP October 15, 2004 Heavy Quarkonium in Quark-Gluon Plasma Cheuk-Yin Wong (黄卓然) Oak Ridge National Laboratory & University of Tennessee • • Introduction Heavy quarkonium in spectral function analysis Heavy quarkonium in potential model Heavy quarkonium bound states in QGP Cross section for g + J/ψ C + C Cross section for C + C g + J/ψ Conclusions C. Y. Wong, hep-ph/0408020

J/ψ suppression as a signature of QGP • J/ψ suppression as a signature of QGP Matsui & Satz, PLB 178, 416 (`86) • J/ψ is bound at T slightly greater than Tc Hansson, Lee, & Zahed, PRD 37, 2672 (`88) • J/ψ suppresion by collisions with nucleons Gerschel and Huefner, PLB 207, 253 (`88) • J/ψ suppresion by collisions with produced particles Vogt, Gavin, Capella, Wong, Barnes, Swanson, Ko, Lin, Lee, Haglin, Blaschke, …… • J/ψ enhancement by recombination Thews & Rafelski, NPA 689, 575 (`02)

J/ψ suppression as a signature of QGP • Lattice gauge results for Fav Digal, Petreczky, Karsch, PRD 64 094015 (`01) • Lattice gauge spectral function analysis Asakawa, Hatsuda, PRL 92, 012001 (`03), Datta, Karsch, Petreczky, J. Phys. G, S 431 (`04) • Lattice gauge calculations of color-singlet Q-Qbar potential Kaczmarek, Karsch, Petreczky, & Zantow, heplat/030912 Petreczky & Petrov, hep-lat/0405009 • Heavy quarkonium bound state calculations Wong, PRC 65, 034902(`02) & J. Phys. G 28, 2349 (`02) • J/ψ suppression and recombination Grandchamp, Rapp, and Brown, J. Phys. G 30, S 1355 (`04) • QGP at T slightly above Tc supports weakly bound meson states Zahed & Shrylak, hep-ph/0307267, hepph/0403127

Spectral function analysis

Lattice gauge spectral analyses in the quenched approximation show that the width of J/ψ remains narrow up to T ≤ 1. 6 TC M. Asakawa, T. Hatsuda, and Y. Nakahara, Nucl. Phys. A 715, 863 (03) P. Petreczky, S. Datta, F. Karsch, and I. Wetzorke, hep-ph/0309012.

Questions: 1. Are there other independent ways to assess the stability of J/ψ in the quarkgluon plasma? 2 What does the potential model say about the stability of J/ψ? 3. What is the binding energy of J/ ψ? 4. How easy is it to dissociate J/ ψ by gluon collisions? 5. How easy is it to recombine C and C to form J/ ψ in QGP?

Kaczmarek, Karsch, Petreczky, Zantow calculated the color -singlet C-C potential in the quenched approximation [heplat/0309121] V 1(r, T) was calculated V in the Coulomb gauge 1

We parameterize the color-singlet Q-Q potential as a screened color-Coulomb potential

Probable reasons for strong coupling αeff(T) just above Tc • • Density of gluons increases substantially above Tc Gluons have a spin (in color space) Spin response is paramagnetic ---- a spin (in color space) tends to align with the imposed color magnetic field, in such a way to enhance the imposed field This enhancement leads to anti-screening There is a competition between anti-screening and disalignment due to thermal motion Magnetic anti-screening wins at T slightly greater than Tc Magnetic anti-screening wins at large T Therefore, there is a strong coupling αs(T) just above Tc. and αs(T) decreases as T increases.

Solve for Q-Q bound states

Dissociation temperatures in quenched QCD Heavy Quarkonium Potential Model Spectral Analysis J/ψ ~ 2. 0 TC ~ 1. 6 TC χ, ψ ' ~ 1. 2 TC ~ 1. 1 TC Υ ~ 4. 5 TC χb, Υ' ~ 2. 0 TC

Why different dissociation temperatures? • Potential model gives the spontaneous dissociation temperature • Heavy quarkonium can dissociate even before reaching spontaneous dissociation temperature by collision with gluons • Spectral analysis includes the interaction of gluons with heavy quarkonium

Quarkonium dissociation process in the potential model

J/ψ dissociation cross section g + J/ψ → c + c

Average dissociation cross section and dissociation width Γdis

Cross section for production of J/ψ by collision of C and C

Rate of J/ψ production

Conclusion • Just above TC, J/ψ and Υ are strongly bound, probably as a result of anti-screening due to free gluons • In the potential model, J/ψ dissociates spontaneously at about 2 TC • Below T=2 TC, J/ψ dissociates by collision with gluons. . Its collision dissociation width is equal to its binding energy at T=1. 2 TC • The potential model and the spectral analysis are qualitatively consistent with each other