32 research outputs found
Precise measurement of hadronic tau-decays with an eta meson
We have studied hadronic tau decay modes involving an eta meson using 490
fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The following branching fractions have been measured: B(tau- ->
K- eta nu)=(1.58 +- 0.05 +- 0.09)x 10^{-4}, B(tau- -> K- pi0 eta nu)=(4.6 +-
1.1 +- 0.4)x 10^{-5}, B(tau- -> pi- pi0 eta nu)=(1.35 +- 0.03 +- 0.07)x
10^{-3}, B(tau- -> pi- KS eta nu)=(4.4 +- 0.7 +- 0.2)x 10^{-5}, and B(tau- ->
K^{*-} eta nu)=(1.34 +- 0.12 +- 0.09)x 10^{-4}. These results are substantially
more precise than previous measurements. The new measurements are compared with
theoretical calculations based on the CVC hypothesis or the chiral perturbation
theory. We also set upper limits on branching fractions for tau decays into K-
KS eta nu, pi- KS pi0 eta nu, K- eta eta nu, pi- eta eta nu and non-resonant K-
pi^0 eta nu final states.Comment: 24 pages, 7 figure
Search for Lepton-Flavor-Violating tau Decays into a Lepton and an f0(980) Meson
We search for lepton-flavor-violating tau decays into a lepton (electron or
muon) and an f0(980) meson using 671 fb-1 of data collected with the Belle
detector at the KEKB asymmetric-energy e+e- collider. No events are observed
and we set the following 90% C.L. upper limits on the branching fraction
products: B(tau- -> e-f0(980))*B(f0(980)->pi+pi-)
mu-f0(980))*B(f0(980) -> pi+pi-)<3.4x10^-8. This is the first search performed
for these modes.Comment: 10 pages, 4 figures, submitted to Phys. Lett.
Search for B+ -> D*+ pi0 decay
We report on a search for the doubly Cabibbo suppressed decay B+ -> D*+ pi0,
based on a data sample of 657 million BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider.
We find no significant signal and set an upper limit of Br(B+ -> D*+ pi0) < 3.6
x 10^-6 at the 90% confidence level. This limit can be used to constrain the
ratio between suppressed and favored B -> D* pi decay amplitudes, r < 0.051, at
the 90% confidence level.Comment: 5pages, 2figures, submitted to PRL (v1); PRL published version (v2:
minor corrections in the text
Measurement of CP asymmetry in Cabibbo suppressed D0 decays
We measure the CP-violating asymmetries in decays to the D0 -> K+K- and D0 ->
pi+pi- CP eigenstates using 540 fb^{-1} of data collected with the Belle
detector at or near the Upsilon(4S) resonance. Cabibbo-favored D0 -> K-pi+
decays are used to correct for systematic detector effects. The results,
A_{CP}^{KK} = (-0.43 +- 0.30 +- 0.11)% and A_{CP}^{pipi} = (+0.43 +- 0.52 +-
0.12)%, are consistent with no CP violation.Comment: Submitted to Phys. Lett.
Study of Decays
We report on a study of decays using
29.1 fb of annihilation data recorded at the
resonance with the Belle detector at the KEKB storage ring. Making no
assumptions about the intermediate mechanism, the branching fractions for
and are
determined to be and respectively. An analysis of candidates yields to the first observation of the color-suppressed
hadronic decay with the branching fraction . We measure the ratio of branching fractions
= 1.6 0.8.Comment: 13 pages, LaTex, 4 figures, submitted to Phys. Lett.
Observation of B_s0->D_s*- pi+, B_s0->D_s(*)- rho+ Decays and Measurement of B_s0->D_s*- rho+ Polarization
First observations of the B_s0->D_s*- pi+, B_s0->D_s- rho+ and B_s0->D_s*-
rho+ decays are reported together with measurements of their branching
fractions: B(B_s0->D_s*- pi+)=(2.4 +0.5-0.4(stat.) +-0.3(syst.)
+-0.4(fs))x10^(-3), B(Bs->D_s- rho+)=(8.5 +1.3-1.2(stat.) +-1.1(syst.)
+-1.3(fs))x10^(-3) and B(Bs->D_s*- rho+)=(11.8 +2.2-2.0(stat.) +-1.7(syst.)
+-1.8(fs))x10^(-3) (f_s=N(B_s(*)B_s(*)-bar)/N(b b-bar)). From helicity-angle
distributions, we measured the longitudinal polarization fraction in
B_s0->D_s*- rho+ decays to be f_L(Bs->D_s*- rho+)=1.05 +0.08-0.10(stat.)
+0.03-0.04(syst.). These results are based on a 23.6 /fb data sample collected
at the Y(5S) resonance with the Belle detector at the KEKB e+e- collider.Comment: 6 pages, 2 figures; submitted to Phys. Rev. Lett
Search for
We report a search for the decay , using a sample of 657
pairs collected with the Belle detector at the
resonance. No statistically significant signal is found and an
upper limit for the branching fraction is determined to be at 90% confidence level.Comment: 5 pages, 2 figures, 3 tables, submitted to PRD(RC
Evidence for Neutral B Meson Decays to wK*0
We present the results of a study of the charmless vector-vector decay
B0->wK*0 with 657x10^6 BB(bar) pairs collected with the Belle detector at the
KEKB e+e- collider. We measure the branching fraction to be
B(B0->wK*0)=[1.8+/-0.7(stat)+/-0.3(syst)]x10^-6 with 3.0sigma significance. We
also perform a helicity analysis of the w and K*0 vector mesons, and obtain the
longitudinal polarization fraction
fL(B0->wK*0)=0.56+/-0.29(stat)+0.18-0.08(syst). Finally, we measure a large
non-resonant branching fraction B[B->wK+pi-; M(Kpi)\in(0.755,1.250)
GeV/c^2]=[5.1+/-0.7(stat)+/-0.7(syst)]x10^-6 with a significance of 9.5sigma.Comment: 6 pages, 3 figures (7 figure files
Search for Lepton-Flavor-Violating tau Decays into a Lepton and a Vector Meson
We search for lepton-flavor-violating tau-> ell V^0 decays, where ell is an
electron or muon and V^0 is one of the vector mesons rho^0, phi, omega, K*0 and
K*0-bar. We use 854 fb^{-1} of data collected with the Belle detector at the
KEKB asymmetric-energy e^+e^- collider. No evidence for a signal is found in
any decay mode, and we obtain 90% confidence level upper limits on the
individual branching fractions in the range (1.2-8.4)*10^{-8}.Comment: 13 pages, 5 figures, submitted to Phys. Lett.