共查询到10条相似文献,搜索用时 93 毫秒
1.
The theoretical mechanisms for the decays ψ′ → ψπ0 and ψ′ → ψη, which violate SU2 and SU3, respectively discussed. It is argued that symmetry breaking in the decay amplitudes may be as important as π0 −η −η′ mixing. The π0 −η mechanism ψ′ → ψν → ψπ0 leads to Γ(ψ′ → ψπ0) = (3.3±1.0) × 10−3 Γ(ψ′ → ψν), but this number may be enhanced by a factor as large as 12 by π0−η′ mixing and isospin violation in the decay amplitude. The related decays ψ → ηγ and ψ → η′γ are also discussed. 相似文献
2.
A very recently reported measurement of the transition rate of Σ− → Γeν shows a 4 to 5 standard deviation discrepancy from the prediction of the Cabibbo theory. It could be attributed to symmetry breaking effects. 相似文献
3.
About ScienceDirect 《Physics letters. [Part B]》1977,70(4):487-490
The anomalous eμ and 2-prong μx events produced in e+e− annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/c2; the mass of the associated neutrino, ντ, is less than 0.6 GeV/c2 with 95% confidence; V - A coupling is favored over V + A coupling for the τ − ντ current; and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic. 相似文献
4.
JADE Collaboration W. Bartel L. Becker D. Cords R. Felst D. Haidt H. Junge G. Knies H. Krehbiel P. Laurikainen R. Meinke B. Naroska J. Olsson D. Schmidt D. Steffen 《Physics letters. [Part B]》1985,160(6):421-429
The radiative width of the η meson has been measured at PETRA in photon-photon collisions. The resulting value is Γη→γγ = 0.53±0.04±0.04 keV. 相似文献
5.
H. Burkhardt 《Nuclear Physics A》1985,440(4):653-658
A recent result for the branching ratio for the decay of the kaonic hydrogen atom to Λγ is used to derive a value for the transition moment for the decay Λ(1405) → Λγ. Two solutions are found, −0.29 < κ < −0.07 and 0.60 < κ < 0.81 proton magnetons, giving decay widths of Γ(Λ(1405) → Λγ) = 6 ± 6 and 74 ± 22 keV, respectively. 相似文献
6.
The similarity between the weak interactions of electron and muon is extended to the principle that all e and μ interactions in gauge models are invariant under e ↔ μ exchange. This necessitates the existence of two Higgs doublets φe and φμ, and an extended e ↔ μ permutation invariance. After symmetry-breaking, a multiplicatively conserved “permutation parity” π = ± 1 for all particles naturally emerges, with πμ = −πe = 1. The model forbids μ → eγ but predicts e−e− → μ−μ− mediated by π = −1 Higgs bosons at 10−11 times the rate of typical weak cross sections. 相似文献
7.
We study semileptonic decays B→η(′)lν, taking into account the flavor-singlet contribution (Fsinglet+) to the B→η(′) form factors, which arises from the two-gluon emission in a decaying B meson. It has been recently pointed out that, in addition to large weak annihilation effects, the unknown value of Fsinglet+ prevents accurate theoretical estimates in the analysis of B→η′K decays in QCD factorization. We present a certain method to determine Fsinglet+ with a reasonable accuracy, using B→η(′)lν and B→πlν decays. We also investigate the possible effect of Fsinglet+ on the estimated branching ratios (BRs) for B→η(′)lν and find that the BR for B→η′lν is particularly sensitive to the effect of Fsinglet+. 相似文献
8.
We study the contribution of Bc mesons to the search for B → τντ decays. We find that at LEP the contributions from Bu and Bc mesons can be comparable. This observation can have a relevant impact on the extraction of constraints on new physics (such as charged-Higgs contributions) from current LEP limits on B → τν final states. Inclusion of the Bc contribution can reduce the current L3 limit on tan β/MH from 0.38 GeV−1 (90% CL) down to 0.27 GeV−1 (90% CL). 相似文献
9.
S. N. Biswas S. R. Choudhury Ashok Goyal J. N. Passi 《Physics letters. [Part B]》1979,80(4-5):393-395
We argue that the presence of second-class neutral currents can be tested from the observations of
and electron polarisation in η→π0e+e-. Consequences of this model in η→π±eνe,τ±→ηπ±ντ and τ±→ωπ±ντ decays which would establish second-class charged currents are also discussed. 相似文献
10.
《Physics letters. [Part B]》2004,590(3-4):161-169
Coherent Λπ− production on Pb of 600 GeV Σ− hyperons has been studied with the SELEX facility at Fermilab. Using the Primakoff formalism, we set a 90% CL upper limit on the radiative decay width Γ[Σ(1385)−→Σ−γ]<9.5 keV, and estimate the cross section for γΣ−→Λπ− at
GeV to be 56±16 μb. 相似文献