scholarly journals Search for Heavy Neutrinos in \(\pi ^{ + } \to \mu ^{ + }\nu \) Decay and Status of Lepton Universality Test in the PIENU Experiment

Author(s):  
S. Ito ◽  
A. Aguilar-Arevalo ◽  
M. Aoki ◽  
M. Blecher ◽  
D. I. Britton ◽  
...  
Keyword(s):  
2019 ◽  
Vol 218 ◽  
pp. 02012
Author(s):  
Graziano Venanzoni

I will report on the recent measurement of the fine structure constant below 1 GeV with the KLOE detector. It represents the first measurement of the running of α(s) in this energy region. Our results show a more than 5σ significance of the hadronic contribution to the running of α(s), which is the strongest direct evidence both in time-and space-like regions achieved in a single measurement. From a fit of the real part of Δα(s) and assuming the lepton universality the branching ratio BR(ω → µ+µ−) = (6.6 ± 1.4stat ± 1.7syst) · 10−5 has been determined


2021 ◽  
Author(s):  
Athanasios Karozas ◽  
◽  
George K. Leontaris ◽  
Ilias Tavellaris ◽  
Nicholas D. Vlachos ◽  
...  
Keyword(s):  

2017 ◽  
Vol 32 (07) ◽  
pp. 1730006 ◽  
Author(s):  
Diego Guadagnoli

The [Formula: see text] measurement by LHCb suggests nonstandard Lepton-Universality Violation (LUV) to occur in [Formula: see text] decays with effects in muons rather than electrons. It is intriguing that a number of other measurements of [Formula: see text] transitions by LHCb and B-factories are consistent in magnitude and sign with the [Formula: see text] effect, and fit a coherent effective-theory picture. Further indications of nonstandard LUV are provided by the long-standing discrepancies in [Formula: see text] transitions via the ratios [Formula: see text] and [Formula: see text]. We review in detail the experimental situation and its rich outlook, the theoretical efforts — and their challenges — towards convincing dynamics beyond the effective-theory level, and discuss the many directions of further investigation that propagate from the current situation.


Particles ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 164-168
Author(s):  
Mădălina Mihaela Miloi ◽  

For clarifying the validity of the Lepton Universality hypothesis, one of the fundamental statements of the Standard Model, the interaction cross section for all three flavors of leptons have to be known with high precision. In neutrino sector, for electron and muon neutrinos, the interaction cross section is known fairly well, but for tau neutrino only poor estimations exist. In particular, the most direct measurement by the DONuT experiment was performed with rather poor accuracy due to low statistics and an uncertainty of the tau neutrino flux. The DsTau experiment proposes to study tau-neutrino production process and thus to improve significantly the accuracy of calculations of tau neutrino flux for neutrino accelerator experiments. To study reactions providing most of tau neutrinos, the experiment uses a setup based on high resolution nuclear emulsions, capable to register short lived particle decays created in proton-nucleus interactions. The present report is an overview of the DsTau experiment together with some of the preliminary results from the pilot run.


Sign in / Sign up

Export Citation Format

Share Document