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Fall-apart decay of Q +

Fall-apart decay of Q +. Atsushi Hosaka (RCNP, Osaka Univ) Feb. 16 (2005) Chiral05 RIKEN. Based on hep-ph/0409102 A. H., M. Oka and T. Shinozaki. Widths & a possible quark model state for Q +. Outline. Fall apart Quark model calculation Comments Possibility of spin 3/2 - Conclusion.

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Fall-apart decay of Q +

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  1. Fall-apart decay of Q+ Atsushi Hosaka (RCNP, Osaka Univ) Feb. 16 (2005) Chiral05 RIKEN Based on hep-ph/0409102 A. H., M. Oka and T. Shinozaki Widths & a possible quark model state for Q+ Chiral05, RIKEN

  2. Outline • Fall apart • Quark model calculation • Comments • Possibility of spin 3/2- • Conclusion Chiral05, RIKEN

  3. Facts ・In production experiments, G << 20 MeV ・In KN scattering 1 MeV or less G = 1, 5, 10, 20 MeV Sibirtsev et al, PLB599 (2004) 230-235 T. Nakano et al. PRL, 91, 012002 (2003) Chiral05, RIKEN

  4. K-like N-like N N* Q+ N Fall apart Expected to be a dominant decay mechanism of Q+ K Q+ Rearranged V N S-factor Intereaction q-qbar annihilation Chiral05, RIKEN

  5. 1/2– S-wave coupling G = 5 GeV Effect of entrifugal barrier ~ 50 ! Simple estimate 1/2+ P-wave coupling M* = 1540 MeV, gKNQ ~ 10 G = 100 MeV Empirical fact: gmNN* < 10 (pNN or sNN) Chiral05, RIKEN

  6. Quark model calculation Mqq interaction for Chiral05, RIKEN

  7. (0s)5 p s Negative parity SU(6) WF for (l=0)5~ ground state Unique for the antidecuplet Fall apart: form qq(K)+qqq(N) conf. => KN Spectroscopic factor gKNQ ~ 3 G ~ 500 MeV Chiral05, RIKEN

  8. (0s)40p p s Positive parity More complicated than s-wave due to p-wave excitation MinimizeSpin-Flavor interaction MinimizeSpin-Color (3) Diquark correlation of JW Chiral05, RIKEN

  9. Other cases > > JW SC SF (1) Most attractive channel for sf interaction qqqq Chiral05, RIKEN

  10. Results (0s)5 1/2ーis dominated by the KN scattering states Chiral05, RIKEN

  11. What we have learned: ・Natural width of Pentaquarks 1/2− ~ GeV <= (0s)5 is expanded by KN 1/2＋ < 100 MeV <= Centrifugal force ・Quark model values are consistent with them Most likely (0s)51/2– can not be a narrow resonance 1/2＋JW-diquark correlation -> 10 MeV For 1 MeV width, we need more (spatial corr.) Chiral05, RIKEN

  12. Comments A related work Melokov, Simula and Stech, PLB 594 (2004) 265 Claimed that G ~ 150 MeV for the JW wf Assumption In the quark model, there is no pole (hA) term ==> Improper use of chiral symmetry Chiral05, RIKEN

  13. (2) QCD sum rule Five quark operator Rearranged (Fierz) as Should be subtracted in the sum rule Kondo-Morimatsu-Nishikawa (KEK) Ambiguities in the Fierz rearrangement Chiral05, RIKEN

  14. Application of the soft kaon method Proportional to fK Chiral05, RIKEN

  15. (3) 5-body calculation Recent calculation by Hiyama Gaussian Expansion Method + + . . . KN Scattering state Confined state Fall apart when R→∞ Coupling to other channels including KN changes the nature of the confined state drastically (0s)5 1/2– (0s)40p 1/2+ could no longer survive neither Chiral05, RIKEN

  16. Other possibility Could it be(0s)5 3/2ー • Decay into KN is suppressed due to d-wave • K*(1ー)N dominante but no decay into this channel • No spin partner of 1/2– …. Too broad to see Chiral05, RIKEN

  17. N S Phenomenology of 3/2- baryons Hyodo-Hosaka, hep-ph/0502093 8-10 mixing Chiral05, RIKEN

  18. • Pick up known resonances of JP = 1/2+ -, 3/2+ - together with Q+ • Fitting into 8-10 mixing 1/2+ 3/2- Chiral05, RIKEN

  19. Coupling constants • qN can be fixed by masses • Two nucleon decay widths determine g8 and g10 • The resulting g10 determines GQ GQ (MeV) Chiral05, RIKEN

  20. SummaryWe have studied the fall-apart decay of Q+ • Naive quark model values (consistent with natural widths) 1/2+ Several tens MeV 1/2– ~ order of GeV 3/2– ~ zero or strongly suppressed • CSF config. far from KN may provide a narrow width 1 MeV width needs more explanation of spatial corr. • Full 5-body calculation could change the naïve results • In the quark model, 3/2– is a natural candidate Chiral05, RIKEN

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