1 / 47

Recent Results from Belle

Recent Results from Belle. S. Hou / National Taiwan University for the Belle Collaboration. IX International Conference on Hadron Spectroscopy August 25-September 1, 2001 Protvino, Russia. The Belle Collaboration. A World-Wide Activity Involving ~300 people from 48 Institutions.

dalia
Download Presentation

Recent Results from Belle

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. Recent Results from Belle S. Hou / National Taiwan University for the Belle Collaboration IX International Conference on Hadron Spectroscopy August 25-September 1, 2001 Protvino, Russia

  2. The Belle Collaboration A World-Wide Activity Involving ~300 people from 48 Institutions Australia Austria China Germany India Korea Japan Philippines Poland Russia Switzerland Taiwan USA Recent results from Belle

  3. Outline • KEKB / Belle performance • Two-photon resonance • K+K,KSKSfinal state • p+pp0final state • c2production • Charm studies • Charmed meson lifetimes andD0D0mixing • D0 decays toKLp0,Ksp0 • Prompt J/, (2S)production • Charmed baryon (by R. Chistov) • Rare B decay • Charmless B decay (by A. Bondar) • Electromagnetic penguin • Color suppressed Most results are preliminary ! Recent results from Belle

  4. KEKB Collider • Asymmetric e+e collider CM energy: 10.58GeV at(4S) e:8 GeV,e+:3.5 GeV 11 mrad beam crossing angle • High luminosity target: 1034cm-2s-1 • Small beam size less then 1 Amp in each beam y~ 3m;x~ 100m • No bending magnet near the IR fewer spent electrons into Belle synchrotron X-rays easily expelled Recent results from Belle

  5. KEKB Performance • Recorded peak: 225 pb-1/day L= 3.5X1033cm-2s-1 L= 4.5X1033cm-2s-1 • Total accumulated luminosity: 32.8 fb-1 225 pb-1/day  3.5x1033/cm2s  Recent results from Belle

  6. Belle Detector Recent results from Belle

  7. Detector Performance • Silicon Vertex Detector • s~ 55 m for 1 GeV @ 90o • Central Drift Chamber • p/p ~ 0.35%@ 1 GeV • sp (dE/dx)~7% • K IDup toplab= 3.5GeV • Time-of-Flight(~95 ps) • Aerogel (n = 1.01 ~ 1.03) • , ewith CsI crystals • E/E ~ 1.5% @ 1 GeV • KLand with KLM (RPCs) • : efficiency > 90% ~2% fakes Recent results from Belle

  8. Particle Identification K/pseparation • dE/dx: Central Drift Chamber • ToF: time-of-flight • ACC: Aerogel Cherenkov Wide momentum coverage Recent results from Belle

  9. K/p separation • K/pseparation : dE/dx + ToF + ACC Combined into likelihood • Calibrated by: • D*+ →D0p+ • D0 →K-p+ ~1 for K ~0 forp K track (eff.) ptrack (fake) Recent results from Belle

  10.   K+K– • Exclusive two-track events of collisions : |p|<6 GeV; |pt|<0.1GeV in thee+e–CM frame • Kaons selected for pt>0.4 GeV, ToF>-0.6 ns andK/pID(dE/dx + ToF + ACC) |pt| in e+e– CM frame K ID vs m(KK)  Belle-note456 Recent results from Belle

  11.   K+K– cross section • Cross section of |cos*|<0.6 in theCM frame • Efficiency estimated by MC • MC generator: TREPS(luminosity function) • Angular dependence: normalized to cos*distributions of data  Recent results from Belle

  12.   K+K– resonances m(K+K–)spectrum fit to • f2-a2 interference • f’2(1525) • a resonance at 1750 MeV • a resonance at 2000 MeV 2/ndf = 41.8/34 Preliminary Recent results from Belle

  13.   K+K– angular distribution Differential cross section: = partial wave amplitude for spin J, helicity  Fittingcos* spectra in W=0.06GeV intervals parameters: 00, 20, 22, phase angle between (J,)=(0,0), (2,0) Resonances at1750, 2000 MeV is in favor of J=2wave Recent results from Belle

  14.   KSKS • Select 4-track events with KS  +– • events: |p|<6 GeV; |pt|2<0.1 GeV2in the e+e–CM frame m(KSKS) vs|pt|2 KS mass resolution: 2.6 MeV  Belle Note416 Recent results from Belle

  15.   KsKs resonance • m(KSKS) spectrum fit to • f2-a2 interference • f’2(1525) • a resonance at 1750 MeV  (fJ)(2220)xB(fJKSKS) <1.2 eV Preliminary Recent results from Belle

  16.   KsKs angular distribution Differential cross section: = partial wave amplitude for spin J, helicity • Fittingcos* spectra in W=0.06 GeV intervals • extract 00 20 22 • Significant J=0 wave in the 1750 MeV region Recent results from Belle

  17.   + – 0 • Events with two-tracks and two final state photons: |p|+E< 5 GeV; |pt|2<0.0002 GeVin thee+e–CM frame • -track pt>0.3 GeV; photon E>150 MeV |pt|2in the mass region fora2(1320) fora2(1750) consist with the-poleMC m(0)resolution:5 MeV  BELLE-CONF-0117 Recent results from Belle

  18.   + – 0 efficiency • Estimated by MC fora2(1320)  a2(1750)   + f2 • Generator:gglu • (luminosity functionegl3 • spin-parity angular-dependence) + – 0 events 2-track + energy triggers  Recent results from Belle

  19.   + – 0 resonance • Mass = 1740  10  10 MeV • Width = 290  30  20 MeV • -width = 0.27  0.02  0.04 keV (assuming pure JP=2+,=2 state) • m() spectrum fit to • a2(1320) fixed • a2(1750) • Side-band constraint for background Preliminary Recent results from Belle

  20.   + – 0 angular distribution • cos of final state pions in a2(1320), 1750 MeVregions • consist withJP=2+, =2 a2(1320)region1.55-2.0 GeV 1.55-2.0 GeV region JP=2+ =0 JP=2+ =2 Recent results from Belle

  21. a2(1750)  , f2interference |(BW()T()) + ei (BW(f2)T(f2))|2 •  enhance f2mass peak •  shift ,f2 peak position • 2tests to full MC spectra  = 0.9  0.1  0.2  = 125 5 10 degree Recent results from Belle

  22.   c2l+l– • Two-track events with one final state , E> 200 MeV |pt (l+l–)|<0.2 GeV; |pt (l+l–)|>0.1 GeV in thee+e–CM frame • Leptons with pt>0.4 GeV; E/p<0.4 for +–; E/p>0.8 for e+e– • c2 J/  l+l– m(l+l–) m(l+l–) – m(l+l–)  Belle Note443 Recent results from Belle

  23.   c2l+l– (cont.) • Comparison with MC • Generator: TREPS (luminosity function)  l+l– back-to-back angle |Pt*tot|Pt of l+l– cos inthe l+l– CM frame cos+ l+inthe l+l– CM frame Recent results from Belle

  24.   c2 cross section • Event observed: 15114 • -width:  = 0.840.08(stat.)0.07(syst.)0.07(Br.) keV Preliminary Recent results from Belle

  25. Charmed meson reconstruction Ground state D-mesons in leading decay modes • D0 K–+ • D0 K–K+ • D+ K–+ + • D+ + (  K–K+) • Ds+ + (  K–K+) • Ds+ K*0K+ (K*0 K–+ ) • K/ ID by dE/dx, ToF, ACC combined likelihood • pD> 2.5 GeVto eliminate B-daughters • Decay angle cuts against random pions • Helicity angle |cosH|>0.4for V-daughters  BELLE-CONF-0131 Recent results from Belle

  26. Charmed meson spectra D0 K–K+ D0 K–+ D++ D*D+0, D+ K–+ + Ds++ Ds+ K*0K+ Recent results from Belle

  27. Charmed meson lifetime fit Unbinned maximum likelihood fit: Parameters set for Signal and Background Event-by-event proper time errorst Signal fraction f iSIGset from the D mass spectra  Recent results from Belle

  28. Lifetime fit D0 D+ DS+ Signal |M|3 D0 D+ DS+ Sideband 3|M|6 Recent results from Belle

  29. Lifetime fit results D meson lifetime Systematic errors Lifetime ratios Preliminary Recent results from Belle

  30. D0-D0 mixing: ycp D1 : CP even D2: CP odd Given: CP eigenstate: CP mixed: Define: Fitting D0 K–+ and D0 K–K+simultaneously Performed with a data sample of 23.4 fb-1  Recent results from Belle

  31. D0-D0 mixing: ycp fit ycp = 0.5 ±1.0 % corresponding to -2.1% < ycp < 3.1% at 95% confidence level Consistent withycp=0 +0.8 -0.9 D0 K–+ D0 K–K+ Signal |M|3 Sideband 3|M|6 Recent results from Belle

  32. D0-D0 mixing by D0KS,L 0 Access toD0-D0 mixingparameters D0 K00 is Cabibbo favored(CF) D0 K00 is doubly Cabibbo suppressed(DCS) Effect is at the 5% levelO(tan2c)  BELLE-CONF-0129 Recent results from Belle

  33. D0KS,L 0reconstruction (a) KS Select events ofD*±D0±, D0KS,LX • Signal: D0KS,L0 • Normalization sample: D0K* KS,L+– • Divide the number of events in selected bins to cancel out systematic effects (b) (KS) • Select • KS byKS +– • KL byKLM neutral cluster (a)/(b) pK(lab) Recent results from Belle

  34. D0KS,L 0results KL0 KS0 =0.880.09(stat.) 0.09(syst.) (KS) (KL) =0.060.05(stat.) 0.05(syst.) Preliminary Recent results from Belle

  35. Prompt charmonium production • Prompt J/ and (2S) production • Dominated by color-singlet processes at (4S) • NRQCD, short and long distance effect • Color singlet vs color octet production • Tevatron: high rate explained by color octet but polarization is not • HERA,LEP: no need for a large color octet contribution  BELLE-CONF-0128 Recent results from Belle

  36. Charmonium selection • SelectJ/  e+e–and+– (2S)  J/ + – • Muon:by KLM hits • Electron:by CDC dE/dx, ECL shower • J/ from B decay: momentump*<1.73 GeV/c, • Require CM momentum p*(J/), p*((2S)) > 2 GeV for data taken at(4S) (4S) data e+e– +– continuum +– e+e–  Recent results from Belle

  37. Charmonium momentum Mass difference of m(J/+–) – m(J/) (4S) data Momentum spectrum No rise in production at higher momentum as suggested by color octete+e–  J/ g process (expectation for 1pb cross section) Recent results from Belle

  38. Charmonium production angle • J/production angle • to the Beam direction in • three momentum intervals • Fit to 1+Acos2 • Helicity angle of l+ • to the J/direction in • three momentum intervals • Fit to 1+cos2 2.0<p*<2.6 GeV 2.0<p*<2.6 GeV 2.6<p*<3.4 GeV 2.6<p*<3.4 GeV 3.4<p*<5 GeV 3.4<p*<5 GeV No significant momentum dependent, as expected by color octet of NRQCD Recent results from Belle

  39. Charmonium cross section • Efficiency by MC (Lund model): e+e–  J/ qq • Checked withe+e–  J/gcolor octet generator embedded in PYTHIA • Systematic errors • Initial state radiation (ISR) e+e–   J/,e+e–  (2S) • estimated to be less than4% • Unknown true event topology: deviate cc contents in MC • 10%in efficiency for 25% cc deviation • Selection cuts: 20% (e+e–  J/X) = 1.57± 0.13 (stat.) ± 0.35 (syst.) pb ((2S)X)/ (J/X) = 0.55 ± 0.11 ± 0.07 B((4S)  J/X) < 1.9 X 10-4 at 90% CL Preliminary Recent results from Belle

  40. Radiative B decays • Penguin loop for non-SM particles • Probe for new physics • Electroweak Penguin : b s  • Indirect limit on the charged Higgs Inclusive B  Xs  (PLB 511, 151 ) one energetic photon E> 2 GeV Xs : oneK or KS plus 1 to 4 pions mB m(Xs) Data, background Bkgd subtracted  BELLE-CONF-0135 Recent results from Belle

  41. Radiative B decays (cont.) B0 K*(892)  B+ K*+(892)  B0 K*2(1430) , K*2 K+– K*2(1430)  K*(1410)   Belle Note396 Recent results from Belle

  42. Radiative B decays (cont.) B+ K*0+ B+ K*+0 Recent results from Belle

  43. Electroweek B XS l+l– decays B XS +– B XS e+e– 2.7  XS=(K+ or KS) + n +3.7 –3.1 9.5 events 4.8  B+  K++– B0 KS +– Combined  BELLE-CONF-0110 Recent results from Belle

  44. Branching fraction Preliminary BELLE-CONF-0109 BELLE-CONF-0110 BELLE-CONF-0135 KEK preprint 2001-13 Belle Note 396 Recent results from Belle

  45. Color suppressed B decays B0 D(*)0 X0 • X0 = light neutral mesons:0, ,  • use D0 K+0, K-+0, K-+-+ D*0 D00 • Final state interaction, factorization Select event with beam constrained mass energy difference First observation 128±18 events 7.9  B0 D00  5.272<Mbc<5.288 BELLE-CONF-0107 Recent results from Belle

  46. Color suppressed B decays (cont.) First observations 30.2±8.6events 4.7  17.7±6.5events 4.3  B0 D*0 B0 D0 Branching fractions & upper limits Preliminary Recent results from Belle

  47. Summary • Two-photon resonance: • High-mass resonancesseen in the K+K–, KSKS, + – 0, l+l– final states • Charm studies: • D-lifetimes and ycp are competitive to world average • D0-D0mixing is investigated by D0KS,L0 • Prompt charmonium production shows little difference for higher momentum, not in favor of color-octet • Rare B-decays: • new observations for penguin decays • color-suppressed B decays higher then predictions Recent results from Belle

More Related