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Phi-Psi, Feb.-Mar., 2006, S.Uehara1 Experimental studies of charmonia in two-photon collisions at Belle S.Uehara (KEK) for the Belle Collaboration e +

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Presentation on theme: "Phi-Psi, Feb.-Mar., 2006, S.Uehara1 Experimental studies of charmonia in two-photon collisions at Belle S.Uehara (KEK) for the Belle Collaboration e +"— Presentation transcript:

1 Phi-Psi, Feb.-Mar., 2006, S.Uehara1 Experimental studies of charmonia in two-photon collisions at Belle S.Uehara (KEK) for the Belle Collaboration e + e  From phi to psi, Feb.27-Mar.2, 2006, BINP, Novosibirsk

2 Phi-Psi, Feb.-Mar., 2006, S.Uehara2 Two-photon formation of a single resonance Collision of two quasi-real photons (Q 2 <0.001GeV 2 ) Kinematics: |  p t |  (  E/E’)  Q 2 < ~ 100 MeV/c Exclusive detections in W  =0.8 - 4.5 GeV QCD, Light-quark resonances and Charmonia Can detect the internal quarks a meson with [Q=0, C=+]

3 Phi-Psi, Feb.-Mar., 2006, S.Uehara3 Physics of two-photon “single-meson formation”  Spin-parity determination conservation rules: C=+, J P = (even)  or (odd) + and J  1 dynamic properties: (J=2, =2) and/or low-L state of qq are favored  Measurement of Two-photon partial decay width  R  B  R  final state  Identify “concrete candidates” for the sequential qq mesons, if their two-photon decay widths are appropriately large.  Study of decay branches detecting “Just exclusively” --- combinatorial backgrounds are minimized Charmonia observed : 0  :  c  1S  c (2S)  0    c0  2   c2 (1P),  c2 (2P)?  2  : None observed

4 Phi-Psi, Feb.-Mar., 2006, S.Uehara4 The KEKB/Belle Experiment The KEKB Accelerator e + e  collisions at  s  10.6 GeV (asymmetric 3.5 on 8 GeV) The world-highest luminosity 1.62  10 34 cm -2 s -1 and integrated luminosity >550 fb -1 (as of Feb.,2006) The Belle Detector Excellent energy/momentum resolutions and particle-separation capabilities 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)

5 Phi-Psi, Feb.-Mar., 2006, S.Uehara5 New charmonium in DD production Search for radial excitation states,  ’ cJ (   cJ (2P)) (J= 0 or 2) predicted in 3.8 – 4.0 GeV mass region. DD candidates are selected in four combinations of decays in 395fb -1 data. A D-meson is tagged at the opposite side Belle hep-ex/0512035, to appear in PRL

6 Phi-Psi, Feb.-Mar., 2006, S.Uehara6 Resonance( Z(3930) )parameters: M=3929  5  2 MeV  = 29  10  2 MeV Yield = 64  18 events Stat. Significance: 5.3  |  p t | < 50 MeV/c Fit function : 3.8 – 4.2 GeV Breit-Wigner + M  Invariant-mass distributions Major systematic-error sources Tracking eff. 7% Selection eff. 8% Kaon ID 4% Fit of M(DD) 5% Luminosity func. 5% BR in D decays 9% Others / 17% in total

7 Phi-Psi, Feb.-Mar., 2006, S.Uehara7 Properties of Z(3930) – a candidate of  ’ c2  B(Z(3930)  DD) =0.18  0.05  0.03 keV B(Z(3930)  D + D - )/B(Z(3930)  D 0 D 0 )= 0.74  0.43  0.16 (isospin invariance) All the properties show this is a  ’ c2 candidate |  p t | distribution of the events in the peak region consistent with exclusive DD decays Angular distribution is consistent with J=2 (D-wave decay), helicity=2 spin-2 spin-0 sideband

8 Phi-Psi, Feb.-Mar., 2006, S.Uehara8  cJ in     and  K  K  Study of QCD at 2.4 0.8GeV/c) Reject  -inclusive events p t -balance: 50(100)MeV/c for  (KK) Rejection of   X decays Particle identification Rejection of e + e ,    , pp K/  separation, Correction for  background using MC Belle PLB 615, 39 (2005)

9 Phi-Psi, Feb.-Mar., 2006, S.Uehara9 Invariant mass distribution Charmonia  c0,  c2 seen in both     and K + K - (first observation in this process) in 87.7 fb -1 data Consistent with  B measurements in other decay modes

10 Phi-Psi, Feb.-Mar., 2006, S.Uehara10 Preliminary Almost background-free K S K S signal samples Continuum component:   K 0 K 0 <<   K + K -   (  c0 )B(  c0  K S K S ) = 7.07  0.61  0.62eV   (  c2 )B(  c2  K S K S ) = 0.30  0.05  0.03eV consistent to K + K   isospin invariance  K S K S :K + K - = 1:2)  c0 (161  41 events)  c2 (44  7 events) (first observation in this process)  cJ in  K 0 S K 0 S A preliminary analysis of

11 Phi-Psi, Feb.-Mar., 2006, S.Uehara11  c  in   pp Belle PLB 621, 41 (2005) Studies of baryon-pair production mechanism, QCD and  c production Selection criteria Two tracks: proton and anti-proton (particle-identification, TOF, dE/dx, Aerogel Cherenkov) p t balance < 0.2 GeV/c  c seen in 89fb -1 data (first observation in this process) cc J/  background

12 Phi-Psi, Feb.-Mar., 2006, S.Uehara12 Measurement of  c production our measurement:  B(  c  pp) = 7.20  1.53  0.67 eV (first observation in this process) 0.75 Comparison to previous pp-incident Experiments at FermiLab also consistent with previous  B(  c  K S K  ) and BF measurements. pp   c      c  pp

13 Phi-Psi, Feb.-Mar., 2006, S.Uehara13  c2 measurement in  J/  mode Belle measurement in 2002 = 13.5  1.5  1.1 eV Previous inconsistency issue between  and pp experiments solved (using a recent value of B(  c2   J/  ) ) A recent CLEO measurement of the same process gives a consistent result. Helicity-2 dominance in production supported Belle PLB 540, 33 (2002) hel.=0 hel.=2 (32.6fb -1 )

14 Phi-Psi, Feb.-Mar., 2006, S.Uehara14   c          ”4  ”  c0 K + K       ”2K2  ”  c2 K + K - K + K -   ”4K”   c (2S)  (with  Ldt=280fb -1 ) Event Selection Two-photon  Exclusive 4-prong event p t -balance -- p t < 0.1 GeV/c in the e + e - CM frame (Exclusive requirement)  /K separation - combined information from (CDC+ACC+TOF) Charmonium production in four-meson decay modes A preliminary analysis of

15 Phi-Psi, Feb.-Mar., 2006, S.Uehara15 Distributions of four-meson invariant masses  c  c0, and  c2 seen in all the modes,  c   c0  c2 44 2K2  4K misidentified  (2S) Preliminary

16 Phi-Psi, Feb.-Mar., 2006, S.Uehara16 Resonance signals in decay products Uppers: crosses: signal region, histogram: sideband regions Lowers: after sideband subtraction =charmonium contribution K* 0  K  in  c2  2K2  KK in  c0  4K M(K  ) (GeV)  0 f 2 (1270)  in  c  4  M(  ) (GeV)

17 Phi-Psi, Feb.-Mar., 2006, S.Uehara17 Results of G    B (each decay mode) Upper limits – 95%CL obtained by the  2 fits Indirect: G indir (R  X) = G(R  A)  Br(R  X)/Br(R  A) R  A - normalization process G/B(  c  KsK  ), G/B(  c0  ), G/B(  c2  J  ) ( ) Preliminary Process Present G(eV) previous (PDG2004) direct indirect

18 Phi-Psi, Feb.-Mar., 2006, S.Uehara18 Search for  c (2S) in four-meson decay modes Rejection of  (2S) is applied Preliminary Upper limits – 95%CL obtained by the  2 fits No peak seen at  c (2S) mass in these channels Lines corresponds to the upper limit   c (2S)  K S K  has been observed by CLEO and BaBar experiments. M(  c (2S)) --- float in 3.63-3.67GeV/c 2  (  c (2S)) --- float in 10 – 40 MeV

19 Phi-Psi, Feb.-Mar., 2006, S.Uehara19 Summary  We have observed a  ’ c2 (2 3 P 2 ) candidate at 3.93GeV/c 2 in the  DD process  and measured a number of new reactions and decay modes.  c0 /  c2     /K + K - /K S K S,  c  pp,  c  4 .  c  f 2 f 2,  c2  K*K*  The measured  c0 and  c2 production rates are consistent with previously measured  ’s and BFs.   c  pp is consistent with previous measurements. In  c  four mesons, we find some deviations from previous measurements of  B and BF.

20 Phi-Psi, Feb.-Mar., 2006, S.Uehara20 Backup slides

21 Phi-Psi, Feb.-Mar., 2006, S.Uehara21 Meson observations in two-photon reactions Observed mesons in two-photon reactions could be “concrete candidates” for the sequential qq mesons, if their two-photon decay widths are appropriately large. Light-quark mesons: 0  :    ’   0  f 0 (980), f 0 ’s (in 1.3 – 1.8 GeV) region?; a 0 (980)  2  f 2 (1270), f 2 ’(1525), f 2 (2050) …? ; a 2 (1320), a 2 (1700), …  2  :  2 (1860)? Charmonia : 0  :  c  1S  c (2S)  0   c0  2  c2 (1P),  c2 (2P)?  2  : None observed

22 Phi-Psi, Feb.-Mar., 2006, S.Uehara22  K 0 S K 0 S preliminary results Very clean KsKs signal samples (almost background free) ptpt Ks reconstruction

23 Phi-Psi, Feb.-Mar., 2006, S.Uehara23 3.5 GeV(e + ), 8 GeV(e  ) E cm (ee) = 10.6 GeV = m(  (4S)) World-highest luminosity KEKB Accelerator

24 Phi-Psi, Feb.-Mar., 2006, S.Uehara24 Good momentum/energy/vertex resolutions Drift chamber(CDC)+1.5T solenoid, CsI EM calorimeters, Silicon vertex detector Excellent Particle-ID performance CsI calorimeter – Electron identification TOF counter, Aerogel-Cherenkov(ACC), dE/dx -- Excellent performance of  (e,  )/K/p separation in wide momentum range High muon detection efficiency RPC for K L and muon detections (KLM) Belle Detector

25 Phi-Psi, Feb.-Mar., 2006, S.Uehara25  c   c0  c2 Fits of the invariant-mass distributions 44 2K2  4K Fit: background – 2 nd -order polynomial charmonium –  c,  c0 --- finite  and fixed  M  to MC  c2 --- assume  is negligibly small (  ~2MeV  comparing  to  M Preliminary

26 Phi-Psi, Feb.-Mar., 2006, S.Uehara26 Study of two-meson resonances in their decays Searches for resonance components decaying into , K , KK resonances The intervals  c – 50MeV,  c0 – 50 MeV,  c2 – 30MeV  0     f 2 (1270)     K* 0 (892)  K +     K + K  f 2 ’(1525)  K + K  etc. Sideband-subtraction technique Watch distributions in “signal  sideband”

27 27 Two-body decays to two two-meson-resonance combinations M(  )(heavier) (GeV) M(  ) (GeV) c f2f24c f2f24 M( K  )(heavier) (GeV) M( K  )(lighter) (GeV)  c2  K* 0 K* 0  2K2 

28 28 Two-body decays to two two-meson-resonance combinations (cont.)  c0  4K M( K  )(lighter) (GeV) M(KK) (GeV) Number of events after the correction for the sideband-subtraction efficiencies Here, statistical errors only. Upper limits – 95%CL obtained by  2 fits

29 29 Systematic Error Sources Trigger efficiency ---- 4% Track reconstruction ---- 6% K-ID efficiency --- 0%(4  ), 4%(2K2  ), 8%(4K) Neutral pion veto etc. --- 3% Charmonium sideband subtraction ---- 12% (  c ),11% (  c0 ), 3%(  c2 ) MC statistics ---- 2 - 4% Luminosity function ---- 5% Total systematic errors 4  final states: 9 – 15% 2K2  final states: 10 – 16% 4K final states: 13 – 17%


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