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
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 = 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.
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
Moriond QCD, Mar., 2007, S.Uehara 4 Reactions at KEKB/Belle The cross sections observable there e + e (4S) BB nb e + e qq (uds) nb e + e cc nb e + e 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)
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 | < MeV/c ) This gives efficient background rejection Two-hadron exclusive final states Meson/baryon Meson/anti-baryon
Moriond QCD, Mar., 2007, S.Uehara 6 K 0 S K 0 S M(K S K S ) |cosθ|<0.6 hep-ex/ Preliminary Selection: - Ks reconstruction from pairs with a detached vertex - p t -balance requirement
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)
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→∞
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 0.05 0.03 Br(K S 0 K S 0 ) / Br(K + K ) 0.49 0.07 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
Moriond QCD, Mar., 2007, S.Uehara 10 ( ))( MvsM )() ( 00 vsMM - Select (X) - Combining (X) c 00 c with unseen hep-ex/ p Ldt= 464fb -1
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 Preliminary BB Br(BB) [eV] Br(BB) PRD 38, 3516 (1988)
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 <
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 – 1.8 keV ss – 0.5 keV KK molecule – 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, (R) (2007) f 0 (980) in 85.9fb -1
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 (no interference) f 0 (980)
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, (2006)
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
Moriond QCD, Mar., 2007, S.Uehara 17 Backup slides
Moriond QCD, Mar., 2007, S.Uehara 18 K 0 S seletion Selection: Ks reconstruction from pairs with a detached vertex
Moriond QCD, Mar., 2007, S.Uehara 19 Fitting formula for f 0 (980)
Moriond QCD, Mar., 2007, S.Uehara 20 Angular distribution Amplitude analysis is now going on. Preliminary
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, (2006) 395fb -1 Spin-0 (dashed) Spin-2, helicity-2 (solid) | p t | distribution
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)