1. Moriond QCD, Mar., 2007, S.Uehara 1 New Results on Two-Photon Physics from Belle S.Uehara (KEK) for the Belle Collaboration Rencontres de Moriond, QCD and Hadron interactions Mar.17-24, 2007

2. Moriond QCD, Mar., 2007, S.Uehara 2 Motivation of Two-Photon Physics 1. Resonance formation hadrons 2. Hard scattering with a quark line Hadron production from two quasi-real photon (|q 2 |<0.001GeV 2, with no-tag condition) Exclusive processes with W  =0.8 - 4.5 GeV at KEKB/Belle Light-quark resonances, Charmonia Perturbative/Non-perturbative QCD, Hadron production mechanism Wide energy region --- Various physics aspects can be studied simultaneously.

3. Moriond QCD, Mar., 2007, S.Uehara 3 KEKB Accelerator and Belle Detector Asymmetric e - e + collider Beam crossing angle: 22mrad Continuous injection Luminosity L max= 1.71x10 34 cm -2 s -1 ∫ Ldt  710 fb -1 (by the end of 2006) 8 GeV e- (HER) x 3.5 GeV e+ (LER)  s=10.58 GeV   (4S) High momentum/energy resolutions CDC+Solenid, CsI Vertex measurement – Si strips Particle identification TOF, Si-aerogel, CDC-dE/dx, RPC for K L /muon

4. Moriond QCD, Mar., 2007, S.Uehara 4 Reactions at KEKB/Belle The cross sections observable there e + e   (4S)  BB --- 1.1 nb e + e   qq (uds) --- 2.1 nb e + e   cc --- 1.2 nb e + e      --- 0.9 nb   hadrons (W  >0.8GeV) --- ~1 nb (within the acceptance) Luminosity Function for quasi-real  collisions d  (in ee) =  (in  ) L  (W) dW Calculated with equivalent-photon approximation E e + e - =10.58GeV Q 2 max =1GeV 2 Luminosity function (1/GeV)

5. Moriond QCD, Mar., 2007, S.Uehara 5 C = + resonances: Peak structure in the invariant mass distribution Test of QCD: c.m.-energy (W) dependence and angular dependence in high energies General Analysis strategy Invariant-mass of hadron pair = W (c.m. energy of  ) Quasi-real two-photon collisions with final state fully reconstructed --- strict transverse momentum balance is required (|  p t | <50 - 200 MeV/c ) This gives efficient background rejection Two-hadron exclusive final states Meson/baryon Meson/anti-baryon

6. Moriond QCD, Mar., 2007, S.Uehara 6  K 0 S K 0 S M(K S K S ) |cosθ|<0.6 hep-ex/0609042 Preliminary Selection: - Ks reconstruction from     pairs with a detached vertex - p t -balance requirement

7. Moriond QCD, Mar., 2007, S.Uehara 7 Angular distribution; comparison with theories - qq  qqqq with wave function --- (M.Benayoun, V.L.Chernyak) - qq w/ hadronic exchange (handbag) --- (M.Diehl, P.Kroll, C.Vogt)  cJ region (check evaluation of angular acceptance) DKV BC Preliminary BC DKV(handbag)

8. Moriond QCD, Mar., 2007, S.Uehara 8 )(/)( 00   KK PLB615,39(2005) = 0.89±0.04±0.15 Cross section; K S 0 K S 0 /K + K  ratio Previous study: W -n dep. Preliminary σ 0 (K S K S )/σ 0 (K + K - ) approaches BC as W→∞

9. Moriond QCD, Mar., 2007, S.Uehara 9  cJ  K S 0 K S 0 decays process  c0  K S 0 K S 0  c2  K S 0 K S 0   Br(K S 0 K S 0 ) (eV)7.00  0.65  0.710.31  0.05  0.03 Br(K S 0 K S 0 ) / Br(K + K  ) 0.49  0.07  0.080.70  0.21  0.12 Consistent with isospin inv. ratio = 0.5 Preliminary Product of two-photon decay width (   ) and branching fraction to K 0 S K 0 S Preliminary

10. Moriond QCD, Mar., 2007, S.Uehara 10     (  ))(  MvsM  )() ( 00  vsMM - Select  (X) - Combining   (X)    c  00  c  with  unseen hep-ex/0609048   p       Ldt= 464fb -1

11. Moriond QCD, Mar., 2007, S.Uehara 11 N may be slightly larger than diquark prediction of  c results from the three processes pp (PLB 621,41(2005)) 7.20  1.53  0.67 0.75 Preliminary  BB Br(BB) [eV] Br(BB) PRD 38, 3516 (1988)

12. Moriond QCD, Mar., 2007, S.Uehara 12 < 460/fb Prelim. Energy dependence of the cross sections Preliminary Compatible with L3 but not with CLEO Cross sections of the three processes come close above 3 GeV <  

13. Moriond QCD, Mar., 2007, S.Uehara 13 f 0 (980) – is ordinary qq meson? - an exotic state? - some special theory needed? The two-photon coupling is a crucial key.  Prediction of    uu, dd --- 1.3 – 1.8 keV ss --- 0.3 – 0.5 keV KK molecule --- 0.2 – 0.6keV f 0 (980) appears as a small but statistically significant peak. f 2 (1270) f 0 (980)  separation: by comparing energy deposit in the ECL between data & MC PRD 75, 051101(R) (2007) f 0 (980) in     85.9fb -1

14. Moriond QCD, Mar., 2007, S.Uehara 14 M [MeV/c 2 ]  [MeV]   [eV] Fit of the f 0 (980) line shape No  ’      (P and CP) seen near 958MeV/c 2 New upper limit for Br(  ’     ), Preliminary    (interference with the non-resonant process allowed) < 3.3  10 -4 (no interference) f 0 (980)    

15. Moriond QCD, Mar., 2007, S.Uehara 15 Other  cJ (1P,2P) measurements Nevents64±18(5.3σ) M[MeV/c 2 ]3929±5±2  [MeV] 29±10±2  Br [keV] 0.18±0.05±0.03 Observation of a new charmonium Z(3930)   Br （  c0        Br （  c   K  K   1.6  2.3   Br （  c2      0.14  0.11   Br （  c2      0.44  0.76  0.14   Br （  c2  J  11  9  2 DD Previous two-photon measurements of   (  cJ (1P))Br from Belle (eV) A  c2 (2P) candidate (from ang. distribution) PLB 615, 39 (2005) PLB 540, 33 (2002) PRL 96, 082003 (2006)

16. Moriond QCD, Mar., 2007, S.Uehara 16 Summary Exclusive hadronic final states from two-photon collisions in no-tag mode are measured at Belle. These results are used to study resonances and test QCD models. -K S 0 K S 0 final state above 2.4 GeV much smaller cross section than K + K -  cJ charmonia measured -     preliminary results ---  c seen, comparison with pp -f 0 (980) shows a small peak in     -Charmonia: two-photon decay width and/or ratios among branching fractions are measured for  c,  c0,  c2 and a  c2 (2P) candidate

17. Moriond QCD, Mar., 2007, S.Uehara 17 Backup slides

18. Moriond QCD, Mar., 2007, S.Uehara 18 K 0 S seletion Selection: Ks reconstruction from     pairs with a detached vertex

19. Moriond QCD, Mar., 2007, S.Uehara 19 Fitting formula for f 0 (980)

20. Moriond QCD, Mar., 2007, S.Uehara 20 Angular distribution Amplitude analysis is now going on. Preliminary

21. Moriond QCD, Mar., 2007, S.Uehara 21  c2 (2P) candidate Nevents64±18(5.3σ) Mass[MeV/c 2 ]3929±5±2  [MeV] 29±10±2  B [keV] 0.18±0.05±0.03 Observation of a new charmonium Z(3930) DD A candidate of  c2 (2P) (from angular distr.) PRL 96, 082003 (2006) 395fb -1 Spin-0 (dashed) Spin-2, helicity-2 (solid) |  p t | distribution

22. Moriond QCD, Mar., 2007, S.Uehara 22 Other  cJ (1P) measurements from Belle  r （  c0       Br （  c   K  K   1.6  2.3  Br （  c2      0.14  0.11  Br （  c2      0.44  0.76  0.14  Br （  c2  J  11  9  2 PLB 615, 39 (2005) PLB 540, 33 (2002) 87.7fb -1 Previous two-photon measurements of  (  cJ (1P))B from Belle (eV) M(ll  )-M(ll)