107 research outputs found
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
Precision measurement of charged pion and kaon differential cross sections in electron-positron annihilation at Q = 10.52 GeV
Measurements of inclusive differential cross sections for charged pion and
kaon production in electron-positron annihilation have been carried out at a
center-of-mass energy of Q = 10.52 GeV. The measurements were performed with
the Belle detector at the KEKB electron-positron collider using a data sample
containing 113 million e+e- -> qqbar events, where q={u,d,s,c}. We present
charge-integrated differential cross sections d\sigma_h+-/dz for h+- = pi+-,
K+- as a function of the relative hadron energy z = 2*E_h / sqrt{s} from 0.2 to
0.98. The combined statistical and systematic uncertainties for pi+- (K+-) are
4% (4%) at z ~ 0.6 and 15% (24%) at z ~ 0.9. The cross sections are the first
measurements of the z-dependence of pion and kaon production for z > 0.7 as
well as the first precision cross section measurements at a center-of-mass
energy far below the Z^0 resonance used by the experiments at LEP and SLC.Comment: 7 pages, 3 figures. Ancillary file including all cross section and
uncertainty values with 10 pages, 5 figure
Search for CP violation in D^0 -> pi^0 pi^0 decays
We search for CP violation in neutral charm meson decays using a data sample
with an integrated luminosity of 966 fb^-1 collected with the Belle detector at
the KEKB e+e- asymmetric-energy collider. The asymmetry obtained in the rate of
D^0 and D^0-bar decays to the pi^0 pi^0 final state,
[-0.03+-0.64(stat)+-0.10(syst)]%, is consistent with no CP violation. This
constitutes an order of magnitude improvement over the existing result. We also
present an updated measurement of the CP asymmetry in the D^0 -> K_S pi^0
decay: A_{CP}(D^0 -> K_S pi^0) = [-0.21+-0.16(stat)+-0.07(syst)]%
Study of B^0 -> rho^0 rho^0 decays, implications for the CKM angle phi_2 and search for other B^0 decay modes with a four-pion final state
We present a study of the branching fraction of the decay B^0->rho0rho0 and
the fraction of longitudinally polarized rho0 mesons in this decay. The results
are obtained from the final data sample containing 772 million BBbar pairs
collected at the Y(4S) resonance with the Belle detector at the KEKB
asymmetric-energy e+e- collider. We find 166 +- 59 B^0 -> rho0 rho0 events
(including systematic uncertainties), corresponding to a branching fraction of
B(B^0->rho0rho0) = (1.02 +- 0.30 (stat) +- 0.15 (syst)) x 10^{-6} with a
significance of 3.4 standard deviations and a longitudinal polarization
fraction fL = 0.21^{+0.18}_{-0.22} (stat) +- 0.15 (syst). We use the
longitudinal polarization fraction to determine the Cabibbo-Kobayashi-Maskawa
matrix angle phi_2 = (84.9 +- 13.5) degrees through an isospin analysis in the
B->rhorho system. We furthermore find 149 +- 49 B^0->f0rho0 events,
corresponding to B(B^0->f0rho0) x B(f0->pi+pi-) = (0.78 +- 0.22 (stat) +- 0.11
(syst)) x 10^{-6}, with a significance of 3.1 standard deviations. We find no
other significant contribution with the same final state, and set upper limits
at 90% confidence level on the (product) branching fractions,
B(B^0->pi+pi-pi+pi-)rho0pi+pi-)<12.0 x 10^{-6},
B(B^0->f0pi+pi-) x B(f0->pi+pi-) f0f0) x
B(f0->pi+pi-)^{2} < 0.2 x 10^{-6}.Comment: 21 pages, 20 figures, conference paper for the 2012th CKM workshop,
submitted to PR
Search for CP Violation in the Decay
We search for CP violation in the decay using a
data sample with an integrated luminosity of 977 fb collected with the
Belle detector at the KEKB asymmetric-energy collider. No CP violation
has been observed and the CP asymmetry in decay is
measured to be , which is the most sensitive
measurement to date. After subtracting CP violation due to
mixing, the CP asymmetry in decay is found to be
.Comment: 15 pages, 4 figures, 1 table. Published in JHE
Observation of a new charged charmoniumlike state in B -> J/psi K pi decays
We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+
decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is
observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+
are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the
preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find
evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data
sample collected by the Belle detector at the asymmetric-energy e+ e- collider
KEKB.Comment: 14 pages, 13 figure
Measurement of the CP Violation Parameters in B0 -> pi+ pi- Decays
We present a measurement of the time-dependent charge-parity (CP) violation
parameters in B0 -> pi+ pi- decays. The results are obtained from the final
data sample containing 772 million BBbar pairs collected at the Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We obtain the CP violation parameters Acp = +0.33 +/- 0.06 (stat) +/- 0.03
(syst) and Scp = -0.64 +/- 0.08 (stat) +/- 0.03 (syst), where Acp and Scp
represent the direct and mixing-induced CP asymmetry, respectively. Using an
isospin analysis including results from other Belle measurements, we find 23.8
< phi2 < 66.8 degrees is disfavored at the 1 sigma level, where phi2 is one of
the three interior angles of the CKM unitarity triangle related to B_{u,d}
decays.Comment: 16 pages, 5 figures, CKM2012 conference paper, Submitted to PR
Observation of Mixing in Collisions
We observe mixing in the decay
using a data sample of integrated luminosity 976 fb collected with the
Belle detector at the KEKB asymmetric-energy collider. We measure the
mixing parameters and and the ratio of doubly Cabibbo-suppressed to
Cabibbo-favored decay rates , where the
uncertainties are statistical and systematic combined. Our measurement excludes
the no-mixing hypothesis at the 5.1 standard deviation level.Comment: 6 pages, 4 figure
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