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This paper presents the results from the BELLE and BaBar experiments at the KEKB asymmetric energy e+e- collider, focusing on B-physics and selected topics of new results. The methods used to extract B-meson signals, as well as the suppression of background and continuum, are discussed.
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Results from BELLE and BaBar Mt. Tsukuba KEKB Belle ~1 km in diameter Gerhard LEDER Hephy Vienna-ÖAW KEK 高エネルギ • Experiments/Tools • B-Physics • Selected topics of new Results
Asymmetric Energy e+e- Collider 590 340
Procedure to extract B Signal Use special Kinematics of Y(4S) Two nearly independent variables MB and DE can be used to select B meson signal: * MB = (Ebeam)2 – (S Pi)2 DE = SEi - Ebeam * Methods to extract B signal yield: 1) Cut on MB and fit to DE 2) Cut on DE and fit to MB 3) Double dimensional fit to MB and DE distribution 4) If B->P1P2P3: cut DEand MB box and look at resonant structures in M(P1P2) mass distribution.
qq e- e+ Other B continuum Y (4S) e+ e- - BB Signal B Continuum Suppression Dominant Background for rare Decays: Continuum e+e-qq “continuum” (~3x BB) Jet-like To suppress: use event shape variables Fox-Wolfram moments Angle between B meson and beam axis direction BB spherical
Unitarity Triangle dsb u Vud Vus Vub c Vcd Vcs Vcb t Vtd Vts Vtb B0->ππ B0->rr B0->J/Ks B0->fKs B0->D(*) D(*) B0-> D*π B0->D*r B->DCPK CKM-Matrix {i=1,k=3}: Vub*Vud+Vcb*Vcd+Vtb*Vtd = 0 Vub*Vud Vcb*Vcd Vtb*Vtd Vcb*Vcd + 1 + = 0 -(rih) -(1-rih) Self-consistent if SM is correct!! rih Unitarity Triangle rih Vtb*Vtd Vcb*Vcd f2 Vub*Vud Vcb*Vcd (a) f3 f1 1 (g) (b) 0
Time-Dependent CP Asymmetry • The CP violationmanifests itself inproper-time differencedistributionsof two B meson decays. • The time-dependent CP asymmetry ACPis: • Standard Model prediction:S(ccs)= sin2f1, A(ccs)= 0S(sss)= sin2f1, A(sss)= small
Principle of Measurement BCP e-: 8.0 GeV e+: 3.5 GeV e- e+ fCP (J/yK0) (4S) bg ~ 0.425 Btag DzcbgtB ~ 200 mm = Flavor tag Dz • Reconstruct BJ/yK0 Decays • proper-time difference: Dt • Get flavor from Btag • Calculate CP Asymmetry from both Dt Distributions
=0.685 ±0.032 Reference Point:precision sin2b 227x106 BB 386x106 BB BaBar 2004: Belle 2005: background
2005 results: Bkg subtracted B+ - projections sin2a sin2F2 B0 tagged B0 tagged p+p− Yield 4s signal for Direct CPV p+p− ACP DE-Mbc 2D fits to individual time intervals Dt (ps) &
2005: Status of B+ - Belle 275M Spp BABAR 227M ~2.3s difference between Belle and BABAR - App (Cpp )
Somov, Schwartz et al hep-ex/0601024 CPV in B+- Measuring F2 (274 106 BB pairs) q=1 q=-1 sin2F2 Results: Low quality tag High quality tag No CPVF2 is near 900
Constraints on 2 (α) B [PRL95,101801(2005)]& combined Fit at 90% CL
* Vud Vub 2(a) * Vtd Vtb 3(g) 1(b) Vcd Vcb * Measuring g(f3) in B → DK In general: need ≥ 2 amplitudes with different weak and strong phases leading to the same final state Critical parameter: Relative amplitude rB, weak phase g and strong phase dB • Use additional dof in D decay to determine simultaneously rB, g, dB • Three methods on the market: • GLW, ADS, D0 Dalitz(GGSZ)
r r “Belle” method for f3: Dalitz Poluektov et al hep-ex/0604054 (subm. PRD) 3) fCOM= D0KSp+p- φ3=53.3 -17.7° +14.8 B+: |A2| |A1| r = Obtain from tagged D0 (D*+ D0p+) Continuum sample WA: CKM-Fitter B-: +13.9 g=59.8 -7.9° B-: CPV: Asymmetry in Dalitz dist.: m+=m(Ksp+), m-=m(Ksp-)
Other Measurements Related to b sin2b in B →J/yp0(bccd) • Color-suppressed tree gives sin2b (no penguin) • b → d penguin pollution (small unless NP) • cos2b in B →J/y K*(KSp0) Time-dependent angular analysis : Itoh et al: PRL 95(2005)091601 cos2f1 hep-ex/0603012 =0.87±0.74±0.12 > 0.
CP angles only cos2b >0. f1~70o Ambiguity removed by i.e.Dalitz analysis of B0D0(Ksp+p-)h0 Krokovny etal hep-ex/0605023(subm PRL) or B0J/yK*(Ksp0) Disfavored >2s f1~70o sin2f1 2-fold ambiguity 2f1 p-2f1 f1~20o f1~20o f1
Sin2beff in b → (qqs) Penguins Searching for New Physics in the loop (2 examples) (r) Look in B0→ (be creative)K0: …and hope Dsin2b ≠ 0 B0r Ks „sin“ 2b= 0.17±0.52± 0.26 First Measurement! B0FK0
Summary of sin(2b) in Penguins Results Representative theory estimates >>all systematically below sin(2b) >>QCD corrections : sin2b(penguin)>sin2b(tree) Naïve2 Average: 0.50 ± 0.06(2.8s) sin2φ1(penguin)-sin2φ1(tree)
How about the CKM triangle’s sides? Dmd & b d g * Vud Vub 2(a) b u ℓ-n & B- ℓ-n Vtd Vtb * 1(b) 3(g) * Vcd Vcb b c l n
Electron energy at endpoint Pth = 1.9 GeV/c Systematic limited Belle Inclusive |Vub| Limosani et al PLB 621, 28 • Hadronic and leptonic • invariant mass (Mx, q2) • Use full recon tag. • P+ also measured. Bizjak et al PRL 95, 141801 • Non-experimental error dominated by errors of shape function parameters. PDG 2002: (3.6 0.7) x 10-3
Inclusive |Vub| Summary Vub=4.45+/-0.20+/-0.26 x 10-3 DVub @7.5%!
First Observation of bd signal qq K*g other B Mohapatra. Nakao, Nishida et al hep-ex/0506079 CDF CDF _ Addresses the same physics issue as Bs- Bs mixing
Current status Constraints from “Loop” Constraints from tree CPV angles only: η=0.321±0.027 =0.193±0.57 sides only: η=0.342±0.02 =0.216±0.06
New physics in EW penguins? FB asymmetry in BK(*)l+l- 2005, L=357fb-1 Bl- B + - l l 3.4 s from 0 K(*) 114±13 ev. Bl- Interference between vector O7 (electromagnetic)+O9(semileptonic) and axialvector O10(semileptonic) operators Wilson coefficients
Signal Remaining energy of signal B in ECL One B (tag) fully reconstructed Ikado et al hep-ex/0604018
Single best measurement of decay constant! c s New: Ds → mn and fDs • Helicity-suppressed leptonic decay: • directly related to decay constant fDs • feeds interpretation of B, Bs mixing • Analysis Method: “D reco” in e+e-→ cc D reco side Signal peak in (normalize to Ds → fp) BaBar (230fb-1): Lattice QCD: BaBar
Finds lots of new mesons :some puzzles Choi et al, PRL 89 112001 Z(3931) cc2’? Choi et al , PRL 91 262001 hc’ X(3872) Uehara et al , PRL 96 082003 Y(3940)wJ/y e+e-cccc Choi et al , PRL 94 182002 ?? Pakhlov et al , hep-ex/0507019 M(wJ/y) MeV
New baryons: c0(2800), c+(2800), c++(2800) observed in c mass spectra Mizuk et al PRL 94,122002(2005) Background subtracted spectra Feed-down from c(2880) c Feed-down from c(2880) c 2005, L=281fb-1 Tentative identification: admixture of c2 & c1 JP=3/2-
288fb-1 Run5! A New Charm Baryon: Λc(2940)+ Observed in e+e-→ cc, Lc(2940)+→ D0p hep-ex/ 0603052 Λc(2880) First observation of Λc(2940)+ Λc(2940) First observation of Λc(2880)+ D0p sidebands
Summary Both experiments show that the CKM-ansatz works extremely well for tree processes Verified with high precision= an „anchor point“ for NP CP-Violation in penguins is a sensitive probe for NP Experimentally and theoretically clean Measuring penguin Bf down to 10-6 with high precision Pure leptonic decays B t n and Ds m n Unexpected discoveries = New mesons and baryons Expect more in the future
Summary f3 error ~100 ?? B+t+n cc2’ X(3940), Y(3940) bd penguins (bdg BKK) DD-mixing (world’s best limit) f2 error~100 |Vub| error <10% Sc* baryon triplet Direct CPV in BK+p- X(3872) BK*ℓ+ℓ- EW penguin D0*0 & D1*0 mesons CPV in B decays hc’ & e+e-cccc
Continuum Suppression • To separate spherical BB events from jet-like continuum events, topological variables are used: • Second Fox-Wolfram moment • Super Fox-Wolfram • (six modified Fox-Wolfram moments, Fisher discriminant) • 3) Angle between B meson and • beam axis direction • 4) Angle between thrusts of • selected B meson particles and all other particles in event • Likelihood ratio includes all info.
Measuring a in B → rr Best mode for a: ~100% longitudinally polarized fL ~ 100% CP » +1 • quasi-two-body approx Ok • no rpp → ignore interference • null search for r0r0 B(r0r0) << B(r+r), B(r+r0) < 1.1 30 6 (26 6 ) x 10-6 New measurement of r+r0: 230 M(BB)
Belle’s measurement of ACP(B0 0 ) Chao, Chang et al, PRL 94 181803 275M BBbar pairs
New Results for the GLW Method (D → fCP) hep-ex/0512067 232 M(BB) 4 observables (ACP+-,RCP+-) to determine rB, g, dB 131 CP+ • Theoretically clean • B → Dp background • Limited statistics 148 CP- New from BaBar: D0 KSw, KSf
Measuring sin(2b+g) in B → D(*)p, Dr Same idea: interference between b → c and b → u But now D flavor known, B flavor unknown→mixing Vcd Suppressed V*ud Interference V*ub Favored Vcb u,c,t u,c,t Time-Dependent CPV Analysis Large rate for favored decay, but small CP asymmetry!
275M BB Neu ACP(B0 K+p-) _ B0 K-p+ B0 K+p- Signal: 2139 53 [submitted to PRL] ACP = -0.101 0.025 0.005 3.9ssignificance [PID efficiency bias correction: dA = -0.01 0.004] Evidenz for DCPV Belle [A(p+p-) 3.2s]
New baryons: cx(3077)+ 2006, L=462 fb-1 Initial motivation: checking SELEX cc(3519)+cK-+ No cc signal observed But Two new excited charm strange baryons found cx(2980)+ wrong-sign c+K+- Preliminary Both cxc K are not identified yet New decays mechanism of charmed baryons: c and s quarks are carried away by different final state particles
p e- D* Breco e+ Bsignal D* X More Studies of DsJ(2317) and DsJ(2460) Hep-ex/0605035 First measurement of absolute BFs Look for resonance structure in B recoil Combine with previous measurements of partial rates to obtain absolute BFs: = 0.70 +- 0.15 (where’s the rest?)