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Strangeness in the Proton and N*(1535)

Strangeness in the Proton and N*(1535). Bing-Song Zou Institute of High Energy Physics Beijing. Collaborators: D.O.Riska, C.S.An, B.C.Liu. Outline. Introduction Strangeness in the proton Strangeness in N*(1535) and its ½- partners Summary. △ -. △ 0. △ +. △ ++. s. (uuu). (ddd).

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Strangeness in the Proton and N*(1535)

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  1. Strangeness in the Proton and N*(1535) Bing-Song Zou Institute of High Energy Physics Beijing Collaborators: D.O.Riska, C.S.An, B.C.Liu

  2. Outline • Introduction • Strangeness in the proton • Strangeness in N*(1535) and its ½- partners • Summary

  3. △- △0 △+ △++ s (uuu) (ddd) n(udd) p(uud) (udd) (uud) 0 *- *+ (uus) (dds) (uds) 0(uds) +(uus) -(dds) I3 0 *- *0 (uss) (dss) -(dss) 0(uss) - (sss) • Introduction SU(3) 3q-quark model for baryons 1/2 + spin-parity 3/2+ Successful for spatial ground states ! Prediction m- 1670 MeV experiment m- 1672.45 0.29 MeV

  4. Outstanding problems for the classical 3q model • Mass order reverse problem for the lowest excited baryons • uud (L=1) ½ - ~ N*(1535) should be the lowest • uud (n=1) ½ + ~ N*(1440) • uds (L=1) ½ - ~ L*(1405) • harmonic oscillator ( 2n + L + 3/2 ) hw • The number of observed states is much less than predicted • “missing” baryon states : non-existence / to be observed ? • Flavor asymmetry of light quarks in the proton • `d –`u ~ 0.12 • Garvey&Peng, Prog. Part. Nucl. Phys.47, 203 (2001)

  5. What are effective degrees of freedom ? • (a) 3q (b) hybrid (c) diquark (d) meson-cloud • Meson cloud picture: Thomas, Speth, Weise, Oset, Brodsky, Ma, … • | p > ~ | uud > + e1 | n ( udd ) p+ (`du ) > • + e2 | D++ ( uuu ) p- (`ud ) > + e’ | L (uds) K+ (`su ) > … • `d >`u , `s / s asymmetry • N*(1535) as K L-KS state, L*(1405) as KN state

  6. 2. Strangeness in the proton neutrino DIS sizable charm production (NuTeV) Longitudinal momentum , pN s-term, large OZI violating f-production from`pp annihilations See reviews by Ellis, Beck, … Question remained : symmetric`ss fluctuation from sea ?

  7. `s / s asymmetrymeson cloud model : • | p > ~ | uud > + e1 | n ( udd ) p+ (`du ) > + e2 | D++ ( uuu ) p- (`ud ) > • + e’ | L (uds) K+ (`su ) > + … • Predictions for the proton: • Strange spin : Ds < 0 • Strange magnetic moment : ms < 0 • Strange radii : rs < 0 • The most recent analysis of data for strange spin •  Ds = -0.05 ~ -0.1 • D. de Florian et al., Phys. Rev. D71 (2005) 094018

  8. Models - a non-exhaustive list for ms and rs: kaon loops, vector dominance, Skyrme model, chiral quark model, dispersion relations, NJL model, quark-meson coupling model, chiral bag model, HBChPT, chiral hyperbag, QCD equalities, Heavy quark, … e.g.,Geiger & Isgur, PRD55, 299 (1997) :K* cloud => ms > 0 Carvalho-Navarra-Nielsen, PRC72, 068202 (2005) • Some recent theoretical attempts with closer relation to QCD : • D. Leinweber et al., Phys. Rev. Lett. 94, 212001 (2005) • Negative ms • X. D. Ji, D.Toublan, hep-ph/0605055 • Positive ms possibly

  9. The strange magnetic moment ms and radii rsfrom parity violating electron scattering G0,HAPPEX/CEBAF, SAMPLE/MIT-Bates, A4/MAMI • HAPPEX/CEBAF, Phys.Rev.Lett. 96 (2006) 022003 • G0/CEBAF, Phys.Rev.Lett. 95 (2005) 092001 • A4/MAMI, Phys.Rev.Lett. 94 (2005) 152001 • SAMPLE/MIT-Bates: Phys.Lett.B583 (2004) 79

  10. Theory vs experiment for ms and rs Our results Zou&Riska, PRL95(2005)072001; Riska&Zou, PLB636 (2006) 265 An-Riska-Zou, PRC73 (2006) 035207

  11. B.S.Zou, D.O.Riska, Phys. Rev. Lett. 95 (2005) 072001 New picture for strangeness in the proton: `s in S-state, uuds in [31]x[22]F[22]S = 1/4 s in P-state including diquark configuration`s [su][ud] , instead of meson cloud L (uds) K+ (`su ) ! | p > ~ | uud > + e1| [ud][ud]`d > + e2 | [ud][us]`s > + … `S u S u `S S u u d d Diquark-cluster vs Meson Cloud

  12. g s `s Strange magnetic form factor Riska & Zou, PLB636 (2006) 265 important & `ss compact, radius ~ 0.2fm

  13. 3. Strangeness in N*(1535) and its ½- partners Baryon spectroscopy from J/y decaysat BES/BEPC Ideal isospin filter

  14. vs • N*(1440): M = 1358+ 17 • G = 179 + 56 • N*(2050): M = 2068+15-40 • G = 165+ 42 pN invariant mass / MC phase space BES, Phys. Rev. Lett. 97 (2006) 062001 “Observation of two new N* peaks …”

  15. The nature of the lowest ½- resonance N*(1535) BES Collaboration, H.B.Li, B.S.Zou, H.C.Chiang, G.X.Peng, J.X.Wang, J.J.Zhu, Phys. Lett. B510 (2001) 75

  16. Nx Nx Events/10MeV (Arbitrary normalization) PS, eff. corrected Nx BES, Int. J. Mod. Phys. A20 (2005) N*(1535) in J/y p K-`L + c.c.

  17. B.C.Liu, B.S.Zou, Phys. Rev. Lett. 96 (2006) 042002 From relative branching ratios of J/y p`N*  p (K-`L) / p (`ph) gN*KL /gN*ph /gN*pp ~ (1.3+0.3) : 1 : 0.6 Smaller N*(1535) BW mass

  18. Mass of N*(1535) (1) (2) (3)

  19. Total cross section and theoretical results with N*(1535), N*(1650), N*(1710), N*(1720) pp  p K+L Tsushima,Sibirtsev,Thomas, PRC59 (1999) 369, without including N*(1535)

  20. A.Zhang, Y. Liu, P. Huang, W. Deng, X.Chen, S.L. Zhu, hep-ph/0403210 : 1/2- and 1/2+ octet N* pentaquarks have similar masses in Jaffe-Wilczek diquark model `q ½ - [ud] [us] u `q ½+ [ud] [ud] u S d `q `q }L=0 }L=1 u d u d N*(1535) ~ uud (L=1) + e [ud][us]`s + … N*(1440) ~ uud (n=1) + x [ud][ud]`d + … L*(1405) ~ uds (L=1) + e [ud][su]`u + … Larger [ud][us]`s component in N*(1535) makes it coupling stronger to Nh & KL, weaker to Np & KS, and heavier ! B.C.Liu, B.S.Zou, PRL 96(2006)042002

  21. The new picture for the ½ - octet predicts: L* [us][ds]`s ~ 1575 MeV S* [us][du]`d ~ 1360 MeV X* [us][ds]`u ~ 1520 MeV MpL L*(1570) ½- ? H.X.Yang, Ph.D thesis (IHEP,2001) S*(1360)1/2- ?

  22. J/y decay branching ratio * 104 `p D(1232)+ 3/2+ < 1 `S- S(1385)+ 3.1  0.5 `X+ X(1520)- 5.9  1.5 `p N*(1535)+ 1/2- 10  3 `S- S(1360)+ ? `X+ X(1530)- ? It is very important to check whether under the S(1385) and X(1520) peaks there are ½- components ? } SU(3) breaking } SU(3) allowed

  23. (ssq) - Baryon Spectroscopy Capstick&Isgur PRD34(1986)2809 Zhu S L’s prediction of pentaquark state Theory is totally not challenged due to lack of data ! BESIII@BEPC2 & Kaon@JPARC

  24. 4. Summary • Predictions for the strangeness in the proton: • meson cloud : Ds < 0 , ms < 0 , rs < 0 • diquark cluster : Ds < 0 , ms > 0 , rs > 0 • 5-quark components in baryons are important • The diquark cluster picture reproduces naturally • the mass pattern forN*(1535) ,N*(1440), L*(1405) • and the strange decay pattern ofN*(1535) • Predictions of the diquark cluster picture for • N*(1535)’s ½- can be checked by BES, JPARC, CLAS, … • ex. :g p -> K S*(1360) with S*(1360) -> L p

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