The self-coupling of weak lepton currents in high energy neutrino and muon reactions

The transverse momentum distribution of the muons in the reaction $\text{ν + (z) → ν + μ +}\text{μ}\text{+ (z)}$ is discussed. The lower end of the energy spectrum of the muons in the previous study is also modified by using an improved interpolation formula.     

Observation of muon pairs in neutrino interactions at Serpukhov 70 GeV accelarator

A search for dimuons produced in a spark chamber experiment in neutrino and antineutrino beams of the Serpukhov accelerator is reported. The clear dimuon signal has been observed in vN interactions. R_v = N(2ω)/N(1ω)? (6.2 ± 1.7) × 10^?3 in the energy interval 7.5 ÷ 30 GeV. From antineutrino data we conclude that in the same energy range $\text{R}{}_{\mathrm{<mtext>v</mtext>}}\text{? 1.1. × 10}{}^{\mathrm{?2}}\text{(90\% C.L.)}$.     

Stronger neutrino interactions at extremely high energies and the muon anomalous magnetic moment

A specific model of parity-conserving lepton substructure is considered. We show that a positive-definite contribution to the muon at the possible level of about can be related to a significant increase in the interaction cross section for cosmic-ray neutrinos with energies above about eV. The additional cross section at eV is calculated to be cm, which is about 100 times the standard weak-interaction cross section. The model involves an extremely massive, neutral lepton, with GeV fixed by the new contribution to . Received: 28 May 2001 / Revised version: 13 November 2001 / Published online: 11 January 2002     

Nonconservation of muon number in a model of lepton structure

We speculate on a possible primary structure for leptons similar to the quark structure for hadrons, and thus propose a new possible approach to the study of these particles. A suppression mechanism is provided for the effects of the new interaction upon the muon anomalous magnetic moment and in the decay amplitude for μ → eγ.     

Charged lepton and neutrino oscillations

Problems long present in the conventional formalism employed for neutrino oscillations are discussed. We here develop a more satisfactory framework based on the Dirac equation and its propagators. When 4-momentum conservation is strictly enforced, there will be induced oscillations in space (but not between generations) for the charged leptons, e.g. and , produced in association with the neutrinos. The oscillations are computed explicitly for the pion decay . Leptonic decays of the are also briefly discussed. Received: 15 October 1996 / Revised version: 15 June 1997 / Published online: 20 February 1998     

Observation of neutrino-like interactions without muon or electron in the gargamelle neutrino experiment

Events induced by neutral particles and producing hadrons, but no muon or electron, have been observed in the CERN neutrino experiment. These events behave as expected if they arise from neutral current induced processes. The rates relative to the corresponding charged current processes are evaluated.     

Nucleon structure functions from high energy neutrino interactions

Structure functions obtained from high energy neutrino and antineutrino scattering from an iron target are presented. These were extracted from the combined data of Fermilab experiments E616 and E701; these utilized narrow band beam runs between 1979–1982. The structure functions are used to test the validity of quarkparton model (QPM) predictions and to extract the QCD scale parameter Λ from fits to the Altarelli-Parisi equations.     

Theoretical study of lepton events in the atmospheric neutrino experiments at SuperK

Super-Kamiokande has reported the results for the lepton events in the atmospheric neutrino experiment. These results have been presented for a 22.5kT water fiducial mass on an exposure of 1489 days, and the events are divided into sub-GeV, multi-GeV and PC events. We present a study of nuclear medium effects in the sub-GeV energy region of atmospheric neutrino events for the quasielastic scattering, incoherent and coherent pion production processes, as they give the most dominant contribution to the lepton events in this energy region. We have used the atmospheric neutrino flux given by Honda et al. These calculations have been done in the local density approximation. We take into account the effects of Pauli blocking, Fermi motion, Coulomb effect, renormalization of weak transition strengths in the nuclear medium in the case of the quasielastic reactions. The inelastic reactions leading to production of leptons along with pions is calculated in a $ \Delta$ -dominance model by taking into account the renormalization of $ \Delta$ properties in the nuclear medium and the final-state interaction effects of the outgoing pions with the residual nucleus. We present the results for the lepton events obtained in our model with and without nuclear medium effects, and compare them with the Monte Carlo predictions used in the simulation and the experimentally observed events reported by the Super-Kamiokande Collaboration.     

Cosmic-ray muon and atmospheric neutrino fluxes at very high energies

Estimates of cosmic-ray muon and atmospheric neutrino fluxes at TeV energies are obtained taking into account a “prompt” production of muons and neutrinos through charmed-particle decays and a “direct” lepton-pair production through the Drell-Yan mechanism and resonances. It is found that the contribution of charmed particles to the muon flux is equal to that from the conventional sources (pion and kaon decays) at 60 TeV, and the same equality can take place at 10 and 1 TeV for muon and electron neutrinos, respectively (for particles coming to sea level in the vertical direction). This “direct” production contribution to muon and neutrino fluxes is estimated very arbitrarily, but it cannot be excluded that this contribution is equal to that from the conventional source at energies of 0.5 and 0.05 PeV for muons and muon neutrinos, respectively. Currently, the estimates of the “prompt” and the “direct” contributions to cosmic-ray muons and atmospheric neutrinos are only qualitative. This is true especially for the “direct” contribution. Nevertheless, it seems reasonable to attract attention to these potentially important sources of atmospheric muons and neutrinos.     

Search for T-violation in neutrino oscillation with the use of muon polarization at a neutrino factory

A possibility to search for T violation in neutrino oscillation with the use of muon polarization is studied. The sensitivity to T violation is examined with various magnitudes of muon polarization as a function of muon energy and long-baseline distances.     

Probing lepton structure at the SSC

If quarks and leptons are composite objects with common constituents, then there exist two-quark-two-lepton contact interactions which could affect lepton pair production at the SSC. We show that for a range of compositeness scales and lepton pair invariant masses, the contact interaction contributions dominate the standard model contributions to the cross section. In this regime, we show that there should be a measurable and statistically significant front-back asymmetry.     

The potential for neutrino physics at muon colliders and dedicated high current muon storage rings

Conceptual design studies are underway for muon colliders and other high-current muon storage rings that have the potential to become the first true “neutrino factories”. Muon decays in long straight sections of the storage rings would produce precisely characterized beams of electron and muon type neutrinos of unprecedented intensity. This article reviews the prospects for these facilities to greatly extend our capabilities for neutrino experiments, largely emphasizing the physics of neutrino interactions.     

Backward particle production in neutrino neon interactions

Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model.     

Tiny neutrino mass from SUSY and lepton number breaking sector

We suggest a new setup where SUSY breaking spurion F-term possesses lepton number. This setup not only modifies sparticle mass spectra but also realizes several new models, where neutrino mass is naturally induced through radiative corrections. We here suggest two new models; the first one is (i): pseudo-Dirac/Schizophrenic neutrino model, and the second one is (ii): pure Majorana neutrino model. We will also show this setup can naturally apply to the supersymmetric Zee-Babu model.     

Vector-like lepton searches at a muon collider in the context of the 4321 model

A feasibility study is performed on the search for vector-like leptons(VLLs) at a muon collider in the context of the "4321 model",an ultraviolet-complete model with rich collider phenomenology and the potential to explain several recent existing B physics measurements or anomalies.Pair production and decays of VLLs lead to an interesting final state topology with multi-jets and multi-tau leptons.In this study,we perform a Monte Carlo investigation with various machine learning techniques and ex...     

Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam

The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3) eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy.     

Final state interactions in the parton model and massive lepton pair production

A scheme of assignments for the 0⁺ nonet is proposed with the S¹ (1000) effect corresponding to resonance poles both on Sheet II and Sheet III, and with the ? located somewhere above 1100 MeV, e.g. at 1300 MeV. A tentative fit of the decay characteristics of these and the other nonet condidates, δ(970) and κ(～1200) is achieved with the mixing angle given by cos²θ_S～ 0.13 instead of the ‘ideal’ value of $\text{2}\text{3}$.