N. Katayama

Measurement of the Decay B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +} and Evidence for B{sub s}{sup 0}{yields}D{sub s}{sup {+-}}K{sup {+-}} in e{sup +}e{sup -} Annihilation at {radical}(s){approx_equal}10.87 GeV

We have studied B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +} and B{sub s}{sup 0}{yields}D{sub s}{sup {+-}}K{sup {+-}} decays using 23.6 fb{sup -1} of data collected at the {upsilon}(5S) resonance with the Belle detector at the KEKB e{sup +}e{sup -} collider. This highly pure B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +} sample is used to measure the branching fraction, B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +})=[3.67{sub -0.33}{sup +0.35}(stat){sub -0.42}{sup +0.43}(syst){+-}0.49(f{sub s})]x10{sup -3} (f{sub s}=N{sub B{sub s}{sup (*)}B{sub s}{sup (*)}/N{sub bb}) and the fractions of B{sub s}{sup 0} event types at the {upsilon}(5S) energy, in particular N{sub B{sub s}*B{sub s}*}/N{sub B{sub s}(*)B{sub s}(*)}=(90.1{sub -4.0}{sup +3.8}{+-}0.2)%. We also determine the masses M(B{sub s}{sup 0})=(5364.4{+-}1.3{+-}0.7) MeV/c{sup 2} and M(B{sub s}*)=(5416.4{+-}0.4{+-}0.5) MeV/c{sup 2}. In addition, we observe B{sub s}{sup 0}{yields}D{sub s}{sup {+-}}K{sup {+-}} decays with a significance of 3.5{sigma} and measure B(B{sub s}{sup 0}{yields}D{sub s}{sup {+-}}K{sup {+-}})=[2.4{sub -1.0}{sup +1.2}(stat){+-}0.3(syst){+-}0.3(f{sub s})]x10{sup -4}.

Measurement of Time-Dependent CP-Violating Parameters in B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} Decays

We report a measurement of the CP-violating parameters in B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} decays based on a data sample of 657x10{sup 6} BB pairs collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. In this Letter, one neutral B meson is fully reconstructed in the B{sup 0}{yields}K{sub S}{sup 0}K{sub S}{sup 0} decay mode, and the flavor of the accompanying B meson is identified by its decay products. The CP-violating parameters are measured from the asymmetry in the distributions of the proper-time interval between the two B decays: S{sub K{sub S}{sup 0}}{sub K{sub S}{sup 0}}=-0.38{sub -0.77}{sup +0.69}(stat){+-}0.09(syst) and A{sub K{sub S}{sup 0}}{sub K{sub S}{sup 0}}=-0.38{+-}0.38(stat){+-}0.05(syst)

Measurement of B(D{sub s}{sup +}{yields}{mu}{sup +}{nu}{sub {mu}})

We present a measurement of the branching fraction B(D{sub s}{sup +}{yields}{mu}{sup +}{nu}{sub {mu}}) using a 548 fb{sup -1} data sample collected by the Belle experiment at the KEKB e{sup +}e{sup -} collider. The D{sub s} momentum is determined by reconstruction of the system recoiling against DK{gamma}X in events of the type e{sup +}e{sup -}{yields}D{sub s}*DKX, D{sub s}*{yields}D{sub s}{gamma}, where X represents additional pions or photons from fragmentation. This full-reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that achieved by experiments at the tau-charm factories. We obtain the branching fraction B(D{sub s}{sup +}{yields}{mu}{sup +}{nu}{sub {mu}})=[6.44{+-}0.76(stat){+-}0.57(syst)]x10{sup -3}, implying a D{sub s} decay constant of f{sub D{sub s}}=[275{+-}16(stat){+-}12(syst)] MeV.

Observation of Anomalous {upsilon}(1S){pi}{sup +}{pi}{sup -} and {upsilon}(2S){pi}{sup +}{pi}{sup -} Production near the {upsilon}(5S) Resonance

Reference EPFL-ARTICLE-154550doi:10.1103/PhysRevLett.100.112001View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10

Evidence for CP Violation in B{sup 0}{yields}D{sup +}D{sup -} Decays

We report measurements of the branching fraction and CP violation parameters in B{sup 0}{yields}D{sup +}D{sup -} decays. The results are based on a data sample that contains 535x10{sup 6} BB pairs collected at the {upsilon}(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We obtain [1.97{+-}0.20(stat){+-}0.20(syst)]x10{sup -4} for the branching fraction of B{sup 0}{yields}D{sup +}D{sup -}. The measured values of the CP violation parameters are S=-1.13{+-}0.37{+-}0.09, A=0.91{+-}0.23{+-}0.06, where the first error is statistical and the second is systematic. We find evidence of CP violation in B{sup 0}{yields}D{sup +}D{sup -} at the 4.1{sigma} confidence level. While the value of S is consistent with expectations from other measurements, the value of the parameter A favors large direct CP violation at the 3.2{sigma} confidence level, in contradiction to standard model expectations.

Measurement of the {tau} Lepton Mass and an Upper Limit on the Mass Difference between {tau}{sup +} and {tau}{sup -}

The mass of the τ lepton has been measured in the decay mode τ→3πντ using a pseudomass technique. The result obtained from 414fb-1 of data collected with the Belle detector is Mτ=[1776.61±0. 13(stat)±0.35(sys)]MeV/c2. The upper limit on the relative mass difference between positive and negative τ leptons is |Mτ+-Mτ-|/ Mτ<2.8×10-4 at 90% confidence level.

Observation of B{sup +}{yields}p{lambda}{gamma}

We report the first observation of the radiative hyperonic B decay B+ --> plambdagamma, using a 140 fb(-1) data sample recorded on upsilom(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. The measured branching fraction is [symbol: see text](B+ --> plambdagamma) = (2.16(+0.58)(-0.53) +/- 0.20) x 10(-6). We examine its M(plambda) distribution and observe a peak near threshold. This feature is expected by the short-distance b --> sgamma transition. A search for B+ --> pepsilon0gamma yields no significant signal, and we set a 90% confidence-level upper limit on the branching fraction of [symbol: see textB+ --> pepsilon0gamma <4.6 x 10(-6).