Improved Measurement of the π→eν Branching Ratio.
نویسندگان
چکیده
A new measurement of the branching ratio R_{e/μ}=Γ(π^{+}→e^{+}ν+π^{+}→e^{+}νγ)/Γ(π^{+}→μ^{+}ν+π^{+}→μ^{+}νγ) resulted in R_{e/μ}^{exp}=[1.2344±0.0023(stat)±0.0019(syst)]×10^{-4}. This is in agreement with the standard model prediction and improves the test of electron-muon universality to the level of 0.1%.
منابع مشابه
N ov 2 00 3 A new evaluation of the pion weak form factors
We have used the PIBETA large acceptance detector for a precise measurement of the π + → e + νγ radiative decay at rest, with broad phase space coverage. Using the CVC value for the pion vector form factor, F V = 0.0259(5), we have obtained a new value of the pion axial-vector form factor γ = F A /F V = 0.429(14). However, significant deviations from the SM predictions are evident in our data. ...
متن کامل2008 / 09 23 5 Testing lepton universality , the π → eν / π → μ ν branching ratio
Determinations of Re/μ are based on observing final states with positrons emerging from a stopped π beam. Decays π → eν(γ) result in positrons appearing with the pion lifetime (26 ns) and with an energy distribution peaking at Ee+ = mπc/2. Decays π → μν(γ) result in positrons too, through the subsequent decay μ → eνν. The latter process leads to a time distribution first rising with the pion li...
متن کاملFinal State Interaction Effects in B+→J/ψ π+ Decay
In this research the exclusive decay of is calculated by QCD factorization (QCDF) method and final state interaction (FSI). First, the decay is calculated via QCDF method. The result that is found by using the QCDF method is less than the experimental result. So FSI is considered to solve the decay. For this decay, via the exchange of mesons are chosen for the intermedi...
متن کاملMeasurement of the Dalitz-decay branching ratio of the π
The ratio B = Γ (π → eeγ)/Γ (π → γγ) is measured by comparing the production rates of the π in the two decay channels. The analysis is based on approximately four million hadronic decays of the Z boson recorded by the ALEPH detector in the years 1991 to 1995. The value of B is determined to be (1.140 ± 0.041)%. A recalculation of the Particle Data Group world average gives rise to a slightly im...
متن کاملForm Factors in D Meson Decays
We study the dΓ/dq spectra and the branching fractions of the D meson exclusive semileptonic decays with the lepton mass effects into consideration. We investigate their sensitivity to form factor models, and find that the decays to a pseudoscalar meson and a lepton pair are sensitive to the property of the form factor F1(q ), and those to a vector meson and a lepton pair to the form factor A1(...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review letters
دوره 115 7 شماره
صفحات -
تاریخ انتشار 2015