1 / 24

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).

vilmos
Télécharger la présentation

Strangeness in the Proton and N*(1535)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related