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J/ ψ production in N-N collisions at threshold

J/ ψ production in N-N collisions at threshold. Egle Tomasi-Gustafsson DAPNIA/SPhN (Saclay, France). Generalities np versus pp collisions spin structure polarization phenomena cross section Conclusions. in collaboration with Michail P. Rekalo.

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J/ ψ production in N-N collisions at threshold

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  1. J/ψproduction in N-N collisions at threshold Egle Tomasi-Gustafsson DAPNIA/SPhN (Saclay, France) • Generalities • np versus pp collisions • spin structure • polarization phenomena • cross section • Conclusions in collaboration with Michail P. Rekalo Egle Tomasi-Gustafsson

  2. Interest of charmed particle production at threshold • Threshold physics, similar to , , ... production. • Large masses: applicability of pQCD for relatively small W (total energy) ? • General symmetry principles applicable in hot, dense matter? Egle Tomasi-Gustafsson

  3. The reaction N+NN+N+J/ψ • Belongs to N+NN+N+V0, with V0 =w, f, J/ψ… • Near-threshold physics • Signatures for quark-gluon plasma: • J/ψ suppression • strangeness excess • Large isotopic effects • p+pp+p+J/ψ • n+pn+p+J/ψ Egle Tomasi-Gustafsson

  4. Definition of threshold region • N+NN+N+J/ψ : all final particles are in relative S-state: L1=L2=0 J/ψ Egle Tomasi-Gustafsson

  5. The spin structure for pp p + p  p + p + J/ψ 1/2+ 1/2+ 1/2+ 1/2+ 1- L2=0 { { L1=0 Sf=0 Egle Tomasi-Gustafsson

  6. The spin structure for np • n + p  n + p + J/ψ • S: 1/2+ 1/2+ 1/2+ 1/2+ 1- • I: 0,1  0,10 I=1: L1=0, Sf=0 ( as pp : f10 ) I=0: L1=0, Sf=1 ( new : f01 ) Egle Tomasi-Gustafsson

  7. The J/ψ polarization The J/ψ polarization vector U has to be orthogonal to k, therefore the decay products for J/ψm++ m- must have a (1+cos2 q)-dependence. For p+p, n+p, therefore for nucleus-nucleus collisions! Egle Tomasi-Gustafsson

  8. Ratio of cross sections • All observables can be calculated in terms of the two amplitudes • The ratio of unpolarized np- and pp- cross sections Egle Tomasi-Gustafsson

  9. Polarized nucleons • The polarized cross section Egle Tomasi-Gustafsson

  10. Polarization observables • The polarization transfer • p1(pp)=p2(pp)=0 for p+p p+p+V0 Egle Tomasi-Gustafsson

  11. The t-channel dynamics • Four pion exchange diagrams for N+NN+N+J/ψ, as well as for any other meson exchange • All diagrams are important at threshold Egle Tomasi-Gustafsson

  12. The t-channel dynamics (p, h, s- exchanges) • The parameter r characterizes the relative role of p and h-exchangeinp+np+n+J/ψ. A “realistic model” : p+ h-exchange F10(np)=-Ap(1-r) F01(np)=-Ap(3+r) • Generally r is a complex parameter Egle Tomasi-Gustafsson

  13. The reaction N+NN+N+J/ψ where r is the ratio of h+NN+ V0 and p+NN+ V0 threshold amplitudes Egle Tomasi-Gustafsson

  14. Correlation polarization coefficient Egle Tomasi-Gustafsson

  15. Polarization transfer coefficient Egle Tomasi-Gustafsson

  16. The reaction N+NN+N+J/ψ So, in VDM approach: Egle Tomasi-Gustafsson

  17. The reaction N+NN+N+J/ψ Egle Tomasi-Gustafsson

  18. The reaction N+NN+N+J/ψEstimation of cross section σexp(ppppφ) ~ 300 nb at pL=3.67 GeV F. Balestra et al., PRC 63, 024004 (2001) Egle Tomasi-Gustafsson

  19. Conclusions • Spin structure and polarization phenomena for N+N N+N+J/ψ can be predicted in model independent way. • Strong isotopic effects. • Polarization phenomena in np-collisions contain more information than in pp-collisions. • P-parity in charmed particle sector. Egle Tomasi-Gustafsson

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