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June 16-20, 2005 北京 1 Atsushi Hosaka (RCNP, Osaka Univ) Decay and production of + hep-ph/0409102, PRD71: 074021 (2005) A. H., M. Oka and T. Shinozaki hep-ph/0502093, PRD71: 054017 (2005) T. Hyodo and A. H. hep-ph/0505134, hep-ph/0503149 to appear PRD S.I. Nam, A.H. and H.-Ch. Kim Decay and production mechanism for + (J P ) with renewed interest in (1520)
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June 16-20, 2005 北京 2 Facts ~ very narrow width ・ In production experiments, << 20 MeV ・ In KN scattering 1 MeV or less T. Nakano et al. PRL, 91, 012002 (2003) A.Sibirtsev et al, PLB599 (2004) 230-235 = 1, 5, 10, 20 MeV More data from Nakano in this conference
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June 16-20, 2005 北京 3 Outline 1. Decay of + General remark Fall-apart in the quark model 2. Possibility of spin 3/2 - Phenomenological analysis 3. Photoproduction reconsidered pn asymmetry n -> K - + vs. p -> K 0 + [ + or (1520)]
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June 16-20, 2005 北京 4 1. Decay of +
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June 16-20, 2005 北京 5 1/2 + P-wave coupling M* = 1540 MeV, g KN ~ 10 1/2 – S-wave coupling = 5 GeV Effect of entrifugal barrier ~ 50 ! Empirical fact: g mNN* < 10 ( NN or NN) = 100 MeV Simple estimate
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June 16-20, 2005 北京 6 Fall apart decay Expected to be a dominant process in a constituent QM Fall apart, or diossociate 5q 4q 3q ~ 5q 2q 5q ~ Other mechanisms? N i = N f N i < N f
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June 16-20, 2005 北京 7 Amplitude Rearranged ++ K N S-factor Intereaction N-like K-like V T ~ V fi We consider fall apart in the quark model
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June 16-20, 2005 北京 8 Mqq of Yukawa type Interaction ~ V fi for Useful as a reference for further studies
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June 16-20, 2005 北京 9 Negative parity ground state (0s) 5 Unique ~ AS KN state g KN ~ 3 => ~ 0.5 - 1 GeV S-factor S-factor ~ p s (0s) 5 Carlson et al, PLB 573, 101 (2003) AH et al,
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June 16-20, 2005 北京 10 Positive parity More complicated than s-wave due to p-wave excitation (1) Minimize Spin-Flavor interaction (2) Minimize Spin-Color (3) Diquark correlation of JW p s (0s) 4 0p We consider
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June 16-20, 2005 北京 11 Spectroscopic factors SF SC JW > > Carlson et al, PRD70, 037501 (2004), hep-ph/0312325, Jennings-Maltman, PRD 69, 094020 (2004), hep-ph/0308286
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June 16-20, 2005 北京 12 Results (1/2 - ) >> (1/2 + )
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June 16-20, 2005 北京 13 We have seen: ・ Natural width of Pentaquarks 1/2 − ~ GeV 1/2 + < 100 MeV <= Centrifugal force ・ Quark model values are consistent with them (0s) 5 1/2 – : as dominated by KN => can not be a narrow resonance 1/2 + with JW-diquark correlation -> 10 MeV (or could be less) Spatial correlation can reduce ~ 1 MeV? dynamical question
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June 16-20, 2005 北京 14 Other possibility Could it be (0s) 5 3/2 ー Decay into KN is suppressed due to d-wave K * (1 ー )N dominant but no decay into this channel No spin partner of 1/2 – …. Too broad to see
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June 16-20, 2005 北京 15 2. Phenomenology of 3/2 - baryons Hyodo-Hosaka, hep-ph/0502093, PRD71:054017 (2005)
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June 16-20, 2005 北京 16 with 8-10 mixing N SU(3) description +, N 1, N 2, 6 parameters
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June 16-20, 2005 北京 17 Choose suitable baryons of J P = 1/2 + -, 3/2 + -, adding + -> 6 baryons are enough Fitting into the SU(3) scheme with 8-10 mixing 1/2 + 3/2 - We can fix the mixing angle
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June 16-20, 2005 北京 18 Coupling constants g 8 and g 10 N can be fixed by masses Two nucleon decay widths determine g 8 and g 10 The resulting g 10 determines (MeV) Decay widths
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June 16-20, 2005 北京 19 3. Photoproductions
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June 16-20, 2005 北京 20 This is serious, but showing absence of + ? p -> n K + K 0 New data from J-Lab p n K+K+ K0K0 ++ Teken from DeVita’s talk at spring APS meeting
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June 16-20, 2005 北京 21 Theoretical study Effective Lagrangian method hep-ph/0505134 Nam-Hosaka-Kim appears only for n-target
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June 16-20, 2005 北京 22 Prior to this n -> K - (1520) and p -> K 0 (1520) was studied and large pn asymmetry was found Nam-Hosaka-Kim, hep-ph/0503149 to appear PRD The role of the contact term (Kroll-Ruderman type) was emphasized
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June 16-20, 2005 北京 23 Total Angular dist Log-scale Theta production, J P = 3/2 -
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June 16-20, 2005 北京 24 The role of the contact term is more important for J P = 3/2 - than 1/2 +
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June 16-20, 2005 北京 25 Predictions We see a large asymmetry between pn targets Cross section for proton ~ few nb is consistent with the upper limit estimated by CLAS
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June 16-20, 2005 北京 26 Summary Fall-apart decay in the quark model 1/2 – ~ GeV 1/2 + Several tens MeV could be 10 MeV or less for JW 3/2 – ~ zero or strongly suppressed SU(3) analysis 3/2 – is a natural candidate Photoproduction, revised There is a large pn asymmetry, especially for J = 3/2 No signal from the CLAS does not lead immediately to the absence of + For (1520), consistent with recent observation of LEPS New data from LEPS is interesting and important => Talk by Takashi Nakano
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June 16-20, 2005 北京 27 Comments (1) A related work Melokov, Simula and Stech, PLB 594 (2004) 265 Claimed that ~ 150 MeV for the JW wf In the quark model, there is no pole (h A ) term ==> Can not be applied to the quark model Assumption
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June 16-20, 2005 北京 28 (2) 5-body calculation Confined state KN Scattering state + +... Recent calculation by Hiyama Gaussian Expansion Method Coupling to other channels including KN changes the nature of the confined state drastically Fall apart when R→∞
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June 16-20, 2005 北京 29 1/2 – 1/2 + KN-like JW-type (0s) 5 1/2 –, (0s) 4 0p 1/2 + can no longer survive
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