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Qiang Zhao Theory Division Institute of High Energy Physics Chinese Academy of Sciences

Institute of High Energy Physics, CAS. Search for Z(4430) in meson photoproduction. Qiang Zhao Theory Division Institute of High Energy Physics Chinese Academy of Sciences. X.-H. Liu, Q.Z. and F.E. Close, PRD in press; arXiv:0802.2648[hep-ph]. 第十届全国粒子物理学术会议，南京， 2008 年 4 月 26-29 日. Outline.

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Qiang Zhao Theory Division Institute of High Energy Physics Chinese Academy of Sciences

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  1. Institute of High Energy Physics, CAS Search for Z(4430) in meson photoproduction Qiang Zhao Theory Division Institute of High Energy Physics Chinese Academy of Sciences X.-H. Liu, Q.Z. and F.E. Close, PRD in press; arXiv:0802.2648[hep-ph] 第十届全国粒子物理学术会议，南京，2008年4月26-29日

  2. Outline • Motivation initiated by Belle results • Photoproduction of Z(4430) • Summary

  3. Belle results K0 s d b W d B+ Z+(4430) c c u u d c  Z+(4430) c c c u d  u Belle Collaboration, PRL(2008); arXiv:0708.1790[hep-ex]

  4. First charmonium with isospin I=1 ! Tetraquark state? (Ebert etal; Rosner; Maiani et al; Lee) Molecular state of D*D1? (Bugg; Liu et al) Subthreshold effects due to D*D1? (Bugg; Chao et al) Baryonium? (Qiao) …… Why not seen in J/ ? Can it couple to c? Where are its flavor partners? …… Strong coupling for Z(4430)

  5. Why care exotics? QCD does not eliminate the existence of hadrons beyond simple (qq) or (qqq) as a color-singlet system. qq Glueball Hybrid Tetraquark Molecule state • How confinement manifests itself at large distances? • What leads to the chiral symmetry spontaneous breaking? • What are the proper effective degrees of freedom for a hadron? • … …

  6. `qq tensor nonet puzzling scalar nonet `qq , `q2q2 , meson molecule ? a0(980) `uu -`dd , [`us`su -`ds`sd ] f’2(1525) `ss f0(980) `ss , [`su`us +`sd`ds ] K2(1430) `sd k(800) `sd , [`su`ud ] a2(1320) `uu -`dd f2(1270) `uu +`dd f0(600) `uu +`dd , [`ud`du ] Low-lying scalar nonet Difficult to distinguish a hidden ss from excited qq. Jaffe, PRD(1977); Slide from B.S. Zou

  7. Photoproduction mechanism Implication of the strong Z coupling d c  Z+(4430) c c c u d  u  *    Z+ Z+(4430)    p n

  8. Quantum numbers A vector (1) and pseudoscalar (0) can make a Z of JP= 1, 0, 1, 2in a relative S or P wave. , 1 Z+(4430) L = 0, 1  , 0

  9. Approach with effective Lagrangians   Z+  p n with Form factor for pion exchange:

  10. Vector meson dominance model   e+ e+ * * V (, , , J/,  …) =   e- e- EM field in terms of vector meson fields: e+ *  e- V* effective coupling:

  11. pion-nucleon coupling  p n Form factor for pion-nucleon coupling: Transition amplitude:

  12. Other mechanism   Z+ a0 p n

  13. Numerical results 1 1  a0 • Forward peaking due to pion exchange • Threshold enhancement similar to charged  production • Negligibly small a0 exchange • Other quantum numbers 1 and 0 are also investigated (X.-H. Liu, Q.Z. and F.E. Close, PRD in press; arXiv:0802.2648[hep-ph] )

  14. H1 at DESY Peak area for Z(4430)

  15. Background contributions Experimentally, one looks at  n as final particles in the detector. (I) Signal transitions are as below: (II) Background contributions due to diffractive  production: Vacuum Pomeron exchange

  16. Contributions from J/ Define: With and the cross sections are still sizeable.

  17. Dalitz plot Z(4430) band Total xsection for p  + n Z(4430), if exists, will stand out of the background in photoproduction.

  18. Perspective • Z(4430) could be the first indisputable exotic meson, a hidden charm system with isospin I=1. • If it is a genuine resonance, its photoproduction will be favored in n channel. A search for it at H1 and ZEUS might help clarifying this issue. • A search for Z(4430) and its partners is necessary.

  19. Thanks !

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