Search results for "Lepton"
showing 10 items of 1512 documents
Search for Electron Antineutrino Appearance at theΔm2∼1 eV2Scale
2009
The MiniBooNE Collaboration reports initial results from a search for nu{sub m}u->nu{sub e} oscillations. A signal-blind analysis was performed using a data sample corresponding to 3.39x10{sup 20} protons on target. The data are consistent with background prediction across the full range of neutrino energy reconstructed assuming quasielastic scattering, 200<E{sub n}u{sup QE}<3000 MeV: 144 electronlike events have been observed in this energy range, compared to an expectation of 139.2+-17.6 events. No significant excess of events has been observed, both at low energy, 200-475 MeV, and at high energy, 475-1250 MeV. The data are inconclusive with respect to antineutrino oscillations suggested …
Measurement of the B0→D*−π+π−π+ branching fraction
2016
Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x 10^-3, where the first uncertainty is statistical and the second is systematic. Our measurement will be helpful in studies of lepton universality by measuring B(B^0 -> D^*- tau^+ nu_tau) using tau^+ -> pi^+ pi^- pi^+ nu-bar_tau decays, normalized to B(B^0 -> D^*- pi^+ pi^- pi^+.
Kaon Physics at CERN – Recent Results from the NA48/2 and NA62 Experiments
2012
This letter presents recent results from the kaon experiments NA48/2 and its successor NA62 at CERN. With samples of 2.5 × 106 K µ 3 ± and 4.0 × 106 K e 3 ± events collected by NA48/2 in 2004, precise measurements of the form factors were performed. The Chiral Perturbation Theory was tested through a new study of K ± → π± γγ decays based on data taken with minimal trigger conditions. Using the beam line and detector of NA48/2 in the years 2007-2008, NA62 performed a precison measurement of the helicitysuppressed ratio of the charged kaon leptonic decay rates K ± → e+ ν and K ± → μ + ν Using the full data set, which is about ten times larger than the previous world data sample, the total unc…
Analysis of the Lepton Mixing Matrix from Neutrino Oscillation Experiments
1988
An analysis of experimental results in the framework of simultaneous oscillations of three neutrino flavours is used, in a combined fit, to constrain the elements of the 3×3 unitary lepton mixing matrix and to obtain limits on the three lepton mixing angles αeμ αeτ and αμτ. No evidence for mixing is found.
Lepton-hadron correlations to $$\mathcal{O}(\alpha _s^2 )$$ in (2+1) jet production at electron-proton colliders
1992
We present one-loop corrected\(\mathcal{O}(\alpha _s^2 )\) results on the four parity-conserving structure functions that describe deep inelastic (2+1)-jet production at high energy electron-proton colliders.
Present Knowledge of the Lepton Mixing Matrix from Neutrino Oscillation Experiments
1986
An analysis of experimental results in the framework of simultaneous oscillations of three neutrino flavours is used, in a combined fit, to constrain the elements of the 3 × 3 unitary lepton mixing matrix and to obtain limits on the three lepton mixing angles αeμ, αe τ and αμτ.
Positron-Electron Angular Correlations in Heavy Ion Collisions
1987
Recent measurements of positrons in coincidence with electrons emitted in U+Th collisions near the Coulomb barrier show sharp line structures in the sum and difference energy spectra of the two leptons (ref. 1). A possible method to clarify the origin of these lines is to study the angular correlation of the leptons. In this short contribution we want to report on a positron-electron coincidence test measurement performed with the TORI spectrometer. This apparatus offers the possibility to measure positrons in coincidence with electrons emitted into the same and opposite hemisphere as well.
Observation of the Semileptonic Decay D0→a0(980)−e+νe and Evidence for D+→a0(980)0e+νe
2018
Using an e(+)e(-) collision data sample of 2.93 fb(-1) collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D-0 -> a(0)(980)(-)e(+)nu( ...
QCD formulation of the tau decay and determination of Lambda (MS)
1988
Abstract We present a simple formulation of the inclusive and exclusive semi-hadronic decays of the tau lepton using QCD-duality finite energy sum rules (FESRs). We find that the tau decay is a good laboratory for measuring the QCD scaleΛ. Within the present experimental accuracy, we obtain Λ M S ¯ ⋍ 100–200 MeV to four loops. This prediction can be sensibly improved once the experimental situation has been clarified.
Leptons and QCD
2015
Three important QCD-related aspects of the τ and μ dynamics are reviewed: the determination of the strong coupling from the hadronic tau decay width, leading to the updated value αs(mτ2)=0.331±0.013; the measurement of |Vus| through the Cabibbo-suppressed decays of the τ, and the Standard Model prediction for the muon anomalous magnetic moment.