48 research outputs found
Improved Measurements of Partial Rate Asymmetry in B -> h h Decays
We report improved measurements of the partial rate asymmetry (Acp) in B -> h
h decays with 140fb^-1 of data collected with the Belle detector at the KEKB
e+e- collider. Here h stands for a charged or neutral pion or kaon and in total
five decay modes are included: K-+ pi+-, K0s pi-+, K-+ pi0, pi-+ pi0 and K0s
pi0. The flavor of the last decay mode is determined from the accompanying B
meson. Using a data sample 4.7 times larger than that of our previous
measurement, we find Acp(K-+ pi+-) -0.088+-0.035+-0.013, 2.4 sigma from zero.
Results for other decay modes are also presented.Comment: 9 pages, 1 figur
Study of the decays B->D_s1(2536)+ anti-D(*)
We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*)
is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at
the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0,
B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of
D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4,
(2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.Comment: 6 pages, 2 figues, submitted to PRD (RC
Evidence for B- -> tau- nu_bar with a Semileptonic Tagging Method
We present a measurement of the decay B- -> tau- nu_bar using a data sample
containing 657 million BB_bar pairs collected at the Upsilon(4S) resonance with
the Belle detector at the KEKB asymmetric-energy e+e- collider. A sample of
BB_bar pairs are tagged by reconstructing one B meson decaying
semileptonically. We detect the B- -> tau- nu_bar candidate in the recoil. We
obtain a signal with a significance of 3.6 standard deviations including
systematic uncertainties, and measure the branching fraction to be Br(B- ->
tau- nu_bar) = [1.54+0.38-0.37(stat)+0.29-0.31(syst)]*10^-4. This result
confirms the evidence for B- -> tau- nu_bar obtained in a previous Belle
measurement that used a hadronic B tagging method.Comment: 7 pages, 3 figures, corrected references, to appear in PRD-R
Search for CP violation in the decay B0->D*+-D-+
We report a search for CP-violating asymmetry in B0 -> D*+- D-+ decays. The
analysis employs two methods of B0 reconstruction: full and partial. In the
full reconstruction method all daughter particles of the B0 are required to be
detected; the partial reconstruction technique requires a fully reconstructed
D- and only a slow pion from the D*+ -> D0 pi_slow+ decay. From a fit to the
distribution of the time interval corresponding to the distance between two B
meson decay points we calculate the CP-violating parameters and find the
significance of nonzero CP asymmetry to be 2.7 standard deviations.Comment: 4 pages, 3 figure
Measurements of the branching fraction and polarization in B+->rho K-+(*0) decays
We present the results of a study of the charmless vector-vector decay B+->rho K-+(*0), based on 253 fb(-1) of data collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We obtain the branching fraction B(B+->rho K-+(*0))=[8.9 +/- 1.7(stat)+/- 1.2(syst)]x10(-6). We also perform a helicity analysis of the rho and K-* vector mesons, and obtain the longitudinal polarization fraction f(L)(B+->rho K-+(*0))=0.43 +/- 0.11(stat)(-0.02)(+0.05)(syst)
Search for D-0-D-0(-) mixing in D-0 -> K+pi(-) decays and measurement of the doubly-Cabibbo-suppressed decay rate
We have searched for mixing in the Ddegrees-(D) over cap (0) D-0 system by measuring the decay-time distribution of D0 ! K(+)pi(-) decays. The analysis uses 90 fb(-1) of data collected by the Belle detector at the KEKB e(+) e(-) collider. We fit the decay-time distribution for the mixing parameters x(1) and y(1) and also for the parameter R-D, which is the ratio of the rate for the doubly-Cabibbo-suppressed decay D-0--> K(+)pi(-) to that for the Cabibbo-favored decay D-0 --> K- pi(+). We do these fits both assuming CP conservation and allowing for CP violation. We use a frequentist method to obtain a 95% C. L. region in the x(J2)- y(l) plane. Assuming no mixing, we measure R-D=(0: 381 +/- 0: 017 (+) (0.008)(-0.016))%
Measurements of B decays to two kaons
We report measurements of B meson decays to two kaons using 253 fb(-1) of data collected with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We find evidence for signals in B+->(K) over bar K-0(+) and B-0-> K-0(K) over bar (0) with significances of 3.0 sigma and 3.5 sigma, respectively. (Charge-conjugate modes are included.) The corresponding branching fractions are measured to be B(B+->(K) over bar K-0(+))=(1.0 +/- 0.4 +/- 0.1)x10(-6) and B(B-0-> K-0(K) over bar (0))=(0.8 +/- 0.3 +/- 0.1)x10(-6). These decay modes are examples of hadronic b -> d transitions. No signal is observed in the decay B-0-> K+K-, and we set an upper limit of 3.7x10(-7) at 90% confidence level
Observation of large CP violation and evidence for direct CP violation in B0+p- decays
We report the first observation of CP violation in B0+p- decays based on 152x106 U(4S)B (B) over bar decays collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct a B0+p- CP eigenstate and identify the flavor of the accompanying B meson from its decay products. From the distribution of the time intervals between the two B meson decay points, we obtain App=+0.580.15(stat)0.07(syst) and Spp=-1.000.21(stat)0.07(syst). We rule out the CP-conserving case, App=Spp=0, at a level of 5.2 standard deviations. We also find evidence for direct CP violation with a significance at or greater than 3.2 standard deviations for any Spp value
Measurement of polarization and triple-product correlations in B -> phi K-* decays
We present measurements of decay amplitudes and triple-product correlations in B ->phi K-* decays based on 253 fb(-1) of data recorded at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. The decay amplitudes for the three different helicity states are determined from the angular distributions of final-state particles. The longitudinal polarization amplitudes are found to be 0.45 +/- 0.05 +/- 0.02 for B-0->phi K-*0 and 0.52 +/- 0.08 +/- 0.03 for B+->phi K*+ decays. CP- and T-odd CP-violating triple-product asymmetries are measured to be consistent with zero
Search for Lepton-number-violating B+->D-l+l'+ Decays
We perform the first search for lepton-number-violating B+->D-l+l'+ decays,
where l and l' stand for e or mu, using 772 x 10^6 BB-bar pairs accumulated at
the Upsilon(4S) resonance with the Belle detector at the KEKB e^+e^- collider.
No evidence for these decays has been found. Assuming uniform three-body phase
space distributions for the D-l+l+ decays, we set the following upper limits on
the branching fractions at 90% confidence level: Br(B+ -> D-e+e+) < 2.6x10^-6,
Br(B+ -> D-e+mu+) D-mu+mu+) < 1.0x10^-6.Comment: 7 pages, 2 figure