877 research outputs found
Search for B0 →τ±∓ (ℓ=e, μ) with a hadronic tagging method at Belle
We present a search for the lepton-flavor-violating decays B0→τ±∓, where ℓ=(e,μ), using the full data sample of 772×106 BB¯ pairs recorded by the Belle detector at the KEKB asymmetric-energy e+e- collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode. The τ± lepton is reconstructed indirectly using the momentum of the reconstructed B and that of the ∓ from the signal decay. We find no evidence for B0→τ±∓ decays and set upper limits on their branching fractions at 90% confidence level of B(B0→τ±μ∓)<1.5×10-5 and B(B0→τ±e∓)<1.6×10-5. © 2021 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3
Measurement of the branching fractions of the B+ -> eta l(+)nu(l) and B+ -> eta ' l(+)nu(l) decays with signal-side only reconstruction in the full q(2) range
The branching fractions of the decays B+ -> eta l(+)nu(l) and B+ -> eta'l(+)nu(l) are measured, where l is either an electron or a muon, using a data sample of 711 fb(-1) containing 772 x 10(6)B (B) over bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. To reduce the dependence of the result on the form factor model, the measurement is performed over the entire q(2) range. The resulting branching fractions are B(B+ -> eta l(+)nu(l)) = (2.83 +/- 0.55((stat.)) +/- 0.34((syst.))) x 10(-5) and B(B+ -> eta'l(+)nu(l)) = (2.79 +/- 1.29((stat.)) +/- 0.30((syst.))) x 10(-5).journal articl
Study of pair production in single-tag two-photon collisions
We report a measurement of the differential cross section of pair
production in single-tag two-photon collisions, , in scattering. The cross section is measured for up to
30 GeV, where is the negative of the invariant mass squared of the
tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and < 1.0 for the total energy and pion scattering angle, respectively,
in the center-of-mass system. The results are based on a data
sample of 759 fb collected with the Belle detector at the KEKB
asymmetric-energy collider. The transition form factor of the
and that of the with the helicity-0, -1, and -2
components separately are measured for the first time and are compared with
theoretical calculations.Comment: 36 pages, 37 figures, 11 tables, Belle Preprint 2015-15, KEK Preprint
2015-2
Observation of
We report the first observation of the decays . The data sample of fb used in this analysis corresponds
to million pairs, collected at the resonance by
the Belle detector at the KEKB asymmetric-energy collider. We
observe and excesses of events for the two decay
modes and measure the branching fractions of and to be
and ,
respectively, where the first uncertainties are statistical and the second are
systematic. These results are not compatible with the predictions based on the
generalized factorization approach. In addition, a threshold enhancement in the
di-baryon () system is observed, consistent with that observed
in similar decays.Comment: 16 pages, 3 figures and 3 tables, submitted to PR
Inclusive study of bottomonium production in association with an meson in annihilations near
We study bottomonium production in association with an meson in
annihilations near the , at a center of mass energy of
GeV. The results are based on the fb data
sample collected by the Belle experiment at the asymmetric energy KEKB
collider. Only the meson is reconstructed and the missing-mass spectrum
of candidates is investigated. We observe the
process and find evidence for the
process, while no significant signals of
, , nor are found. Cross sections for the
studied processes are reported.Comment: Submitted to EPJ-
Measurement of branching fraction and direct asymmetry in charmless decays at Belle
We report a study of the charmless hadronic decay of the charged meson to
the three-body final state . The results are based on a data
sample that contains pairs collected at the
resonance with the Belle detector at the KEKB asymmetric-energy
collider. The measured inclusive branching fraction and the direct
asymmetry are and
, respectively, where the first uncertainties are
statistical and the second are systematic. The invariant mass
distribution of the signal candidates shows an excess in the region below
GeV/, which is consistent with the previous studies from BaBar and LHCb.
In addition, strong evidence of a large direct asymmetry is found in the
low-invariant-mass region.Comment: 7 pages, 3 figure
Energy scan of the cross sections and evidence for decays into charged bottomonium-like states
Using data collected with the Belle detector at the KEKB asymmetric-energy
collider, we measure the energy dependence of the cross sections from thresholds up to GeV.
We find clear and peaks with little or no
continuum contribution. We study the resonant substructure of the
transitions and find evidence that they
proceed entirely via the intermediate isovector states and
. The relative fraction of these states is loosely constrained by
the current data: the hypothesis that only is produced is excluded
at the level of 3.3 standard deviations, while the hypothesis that only
is produced is not excluded at a significant level.Comment: 8 pages, 4 figures, submitted to Physical Review Letter
Measurement of eta_c(1S), eta_c(2S) and non-resonant eta' pi+ pi- production via two-photon collisions
We report the measurement of gamma gamma to eta_c(1S), eta_c(2S) to eta' pi+
pi- with eta' decays to gamma rho and eta pi+ pi- using 941 fb^{-1} of data
collected with the Belle detector at the KEKB asymmetric-energy e+e- collider.
The eta_c(1S) mass and width are measured to be M = [2984.6\pm0.7 (stat.)\pm2.2
(syst.)] MeV/c^{2} and \Gamma = [30.8^{+2.3}_{-2.2}~(stat.) \pm 2.5~(syst.)]
MeV, respectively. First observation of eta_c(2S) to eta' pi+ pi- with a
significance of 5.5sigma including systematic error is obtained, and the
eta_c(2S) mass is measured to be M = [3635.1\pm3.7~(stat.)\pm2.9~(syst.)]
MeV/c^{2}. The products of the two-photon decay width and branching fraction
(B) of decays to eta'pi+ pi- are determined to be \Gamma_{gamma gamma}B =
[65.4\pm2.6~(stat.)\pm6.9~(syst.)] eV for eta_c(1S) and
[5.6^{+1.2}_{-1.1}~(stat.)\pm1.1~(syst.)] eV for eta_c(2S). A new decay mode
for the eta_c(1S) to eta'f_0(2080) with f_0(2080) to pi+ pi- is observed with a
statistical significance of 20sigma. The f_0(2080) mass and width are
determined to be M = [2083^{+63}_{-66}~(stat.)\pm 32~(syst.)] MeV/c^{2} and
\Gamma = [178^{+60}_{-178}~(stat.) \pm 55~(syst.)] MeV. The cross sections for
gamma gamma to eta' pi+ pi- and eta'f_{2}(1270) are measured for the first
time.Comment: 19 pages, 14 figure
Measurement of the Branching Fraction of the Decay in Fully Reconstructed Events at Belle
We present an analysis of the exclusive
decay, where represents an
electron or a muon, with the assumption of charge-conjugation symmetry and
lepton universality. The analysis uses the full data sample
collected by the Belle detector, corresponding to 711 fb of integrated
luminosity. We select the events by fully reconstructing one meson in
hadronic decay modes, subsequently determining the properties of the other
meson. We extract the signal yields using a binned maximum-likelihood fit to
the missing-mass squared distribution in bins of the invariant mass of the two
pions or the momentum transfer squared. We measure a total branching fraction
of , where the
uncertainties are statistical and systematic, respectively. This result is the
first reported measurement of this decay.Comment: 23 pages, 19 figure
First observation of the hadronic transition and new measurement of the and parameters
Using a sample of decays collected by
the Belle experiment at the KEKB collider, we observe for the first
time the transition with the branching fraction
and we measure the mass MeV/, corresponding to the hyperfine splitting MeV/. Using the transition , we measure the mass MeV/, corresponding to MeV/, the width
MeV/ and the branching
fraction .Comment: 7 pages, 2 figures, submitted to Phys. Rev. Let
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