We search for lepton-flavor and lepton-number-violating τ decays into a lepton (ℓ= electron or muon) and two charged mesons (h,h′=π± or K±) using 854 fb−1 of data collected with the Belle detector at ...the KEKB asymmetric-energy e+e− collider. We obtain 90% confidence level upper limits on the τ→ℓhh′ branching fractions in the range (2.0–8.4)×10−8. These results improve upon our previously published upper limits by factors of about 1.8 on average.
We search for lepton-flavor-violating τ→ℓV0 decays, where ℓ is an electron or muon and V0 is one of the vector mesons ρ0, ϕ, ω, K⁎0 and K¯⁎0. 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.
We report the first evidence for the η(b)(2S) using the h(b)(2P)→η(b)(2S)γ transition and the first observation of the h(b)(1P)→η(b)(1S)γ and h(b)(2P)→η(b)(1S)γ transitions. The mass and width of the ...η(b)(1S) and η(b)(2S) are measured to be m(η(b)(1S))=(9402.4±1.5±1.8) MeV/c(2), m(η(b)(2S))=(9999.0±3.5(-1.9)(+2.8)) MeV/c(2), and Γ(η(b)(1S))=(10.8(-3.7-2.0)(+4.0+4.5)) MeV. We also update the h(b)(1P) and h(b)(2P) mass measurements. We use a 133.4 fb(-1) data sample collected at energies near the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider.
Study of τ−→KSπ−ντ decay at Belle Epifanov, D.; Aihara, H.; Aulchenko, V. ...
Physics letters. B,
10/2007, Letnik:
654, Številka:
3-4
Journal Article
Recenzirano
We present a study of the decay τ−→KSπ−ντ using a 351 fb−1 data sample collected with the Belle detector. The analysis is based on 53,110 lepton-tagged signal events. The measured branching fraction ...B(τ−→KSπ−ντ)=(0.404±0.002(stat.)±0.013(syst.))% is consistent with the world average value and has better accuracy. An analysis of the KSπ− invariant mass spectrum reveals contributions from the K∗(892)− as well as other states. For the first time the K∗(892)− mass and width have been measured in τ decay: M(K∗(892)−)=(895.47±0.20(stat.)±0.44(syst.)±0.59(mod.)) MeV/c2, Γ(K∗(892)−)=(46.2±0.6(stat.)±1.0(syst.)±0.7(mod.)) MeV. The K∗(892)− mass is significantly different from the current world average value.
Equal amounts of matter and antimatter are predicted to have been produced in the Big Bang, but our observable Universe is clearly matter-dominated. One of the prerequisites for understanding this ...elimination of antimatter is the nonconservation of charge-parity (CP) symmetry. So far, two types of CP violation have been observed in the neutral K meson (K0) and B meson (B0) systems: CP violation involving the mixing between K0 and its antiparticle (and likewise for B0 and ), and direct CP violation in the decay of each meson. The observed effects for both types of CP violation are substantially larger for the B0 meson system. However, they are still consistent with the standard model of particle physics, which has a unique source of CP violation that is known to be too small to account for the matter-dominated Universe. Here we report that the direct CP violation in charged B±→K± 0 decay is different from that in the neutral B0 counterpart. The direct CP-violating decay rate asymmetry, (that is, the difference between the number of observed B-→K- 0 event versus B+→K+ 0 events, normalized to the sum of these events) is measured to be about +7%, with an uncertainty that is reduced by a factor of 1.7 from a previous measurement. However, the asymmetry for versus B0→K+ - is at the -10% level. Although it is susceptible to strong interaction effects that need further clarification, this large deviation in direct CP violation between charged and neutral B meson decays could be an indication of new sources of CP violation-which would help to explain the dominance of matter in the Universe.
We have studied hadronic τ decay modes involving an η 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(τ−→K−ηντ)=(1.58±0.05±0.09)×10−4, B(τ−→K−π0ηντ)=(4.6±1.1±0.4)×10−5, B(τ−→π−π0ηντ)=(1.35±0.03±0.07)×10−3, B(τ−→π−KS0ηντ)=(4.4±0.7±0.2)×10−5, and B(τ−→K∗−ηντ)=(1.34±0.12±0.09)×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 τ decays into K−KS0ηντ, π−KS0π0ηντ, K−ηηντ, π−ηηντ and non-resonant K−π0ηντ final states.
We search for lepton flavor violating τ decays into three leptons (electron or muon) using 535 fb−1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. No evidence ...for these decays is observed, and we set 90% confidence level upper limits on the branching fractions of (2.0–4.1)×10−8. These results improve upon our previously published upper limits by factors of 4.9 to 10.
We report measurements of the branching fractions and CP asymmetries for B(±)→ηh(±) (h=K or π) and the observation of the decay B(0)→ηK(0) from the final data sample of 772×10(6) B ̅B pairs collected ...with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The measured branching fractions are B(B(±)→ηK(±))=(2.12±0.23±0.11)×10(-6), B(B(±)→ηπ(±))=(4.07±0.26±0.21)×10(-6), and B(B(0)→ηK(0))=(1.27(-0.29)(+0.33)±0.08)×10(-6), where the last decay is observed for the first time with a significance of 5.4 standard deviations (σ). We also find evidence for CP violation in the charged B modes, A(CP)(B(±)→ηK(±))=-0.38±0.11±0.01 and A(CP)(B(±)→ηπ(±))=-0.19±0.06±0.01 with significances of 3.8 σ and 3.0 σ, respectively. For all measurements, the first and second uncertainties are statistical and systematic, respectively.
We report a precise measurement of the masses of the Ξc(2645) and Ξc(2815) baryons using a data sample of 414 fb−1 collected by the Belle Collaboration at the KEKB e+e− collider. The states ...Ξc(2645)0,+ are observed in the Ξc+,0π−,+ decay modes, while the Ξc(2815)0,+ are reconstructed in the Ξc(2645)+,0π−,+ decay modes. The following mass splittings are determined: mΞc(2645)+−mΞc(2645)0=(−0.1±0.3(stat)±0.6(syst)) MeV/c2 and mΞc(2815)+−mΞc(2815)0=(−3.4±1.9(stat)±0.9(syst)) MeV/c2 with a much better precision than the current world averages. We also observe a new decay mode, Ξc(2980)0,+→Ξc(2645)+,0π−,+.
We present a search for the decays B+→μ+νμ and B+→e+νe in a 253 fb−1 data sample collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy B factory. We find no ...significant evidence for a signal and set 90% confidence level upper limits of B(B+→μ+νμ)<1.7×10−6 and B(B+→e+νe)<9.8×10−7.
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