arXiv subjects
Publications and source records attributed to Masahiro Kuze.
Neutrino experiments at J-PARC are reviewed. After an introduction to neutrino physics, with emphasis on neutrino oscillation, the T2K experiment at the Main Ring neutrino beam line and its peripheral experiments are introduced. Also future prospects of the Japanese long-baseline oscillation experiments are given. In addition, a new attempt to search for sterile neutrinos at the J-PARC MLF, JSNS$^2$ experiment, is introduced.
Lepton-hadron colliders that use a proton or nucleus beam of current and future hadron colliders and let it collide with an electron beam from a newly built electron accelerator bring attractive physics programs which are strong and complementary to the hadron collider physics. Machine development for Energy Recovery LINAC and physics performance studies of such electron-hadron colliders, specifically the LHeC that uses the existing LHC beam and FCC-eh that is an option of Future Circular Collider program, are ongoing and reviewed in this article.
Recent results on $W$, $Z$ and photon production at the Large Hadron Collider are presented. Inclusive $W$ and $Z$/$γ^*$ production, their production in association with jets and heavy flavors, and prompt photon, $γγ$ and $γ$+jets production are discussed.
Neutrinos exhibit an interesting phenomenon called 'neutrino oscillation', in which a neutrino changes its flavor after traveling some flight length. Many experiments measured the mixing angles and mass differences, but the angle $θ_{13}$ had been unmeasured due to its smallness compared to others. During 2011 and 2012, series of new-generation neutrino experiments reported positive results in $θ_{13}$ search, and its value has been determined to be just below the previous upper limit. The non-zero result of $θ_{13}$ is a very good news for future of neutrino physics, since it opens a possibility of measuring the CP violation phase in the lepton sector. An introduction to neutrino oscillation and latest experimental results are presented. A detail is put on Double Chooz reactor experiment, in which the author is involved.
Double Chooz experiment will search for a disappearance of the reactor neutrinos from Chooz reactor cores in Ardenne, France, in order to detect the yet unknown neutrino oscillation angle θ13. The far detector was completed in 2010 and data-taking has started in spring 2011. Status of data-taking is presented and some performance plots from physics data are shown in this paper for the first time. Also the prospect of experimental sensitivity is presented, in light of recent indication from T2K for a non-zero θ13 value.
Recent results on searches for signals of physics beyond Standard Model at the ep collider HERA are reviewed. Limits obtained for contact interaction models, large extra dimensions and finite quark radius are presented. Searches for excited-fermion resonances yield unique limits on excited electrons and neutrinos. Finally, measurement of W production cross section in ep collision is presented.
A new reactor-neutrino oscillation experiment, KASKA, is proposed to measure the unknown neutrino-mixing angle $θ_{13}$ using the world's most powerful Kashiwazaki-Kariwa nuclear power station. It will measure a very small deficit of reactor-neutrino flux using three identical detectors, two placed just close to the sources and one at a distance of about 1.8km. Its conceptual design and physics reach are discussed.
We study a lepton flavor violating $μN \to τX$ reaction in deep inelastic scattering region in supersymmetric models. The contribution from the Higgs boson mediation could be important for this reaction. For that case, the cross section is constrained by the experimental limit of the pseudo-scalar coupling from $τ\to μη$ decays. We find that at a muon energy ($E_μ$) higher than 50 GeV, the predicted cross section increases significantly due to the contribution from sea $b$-quarks. As a result, with $10^{20}$ muons per year, at most a number of $\mathcal{O}(10^4)$ is expected for $μN \to τX$ events at $E_μ$= 300 GeV, whereas $\mathcal{O}(10^2)$ events are given at $E_μ= 50$ GeV. Furthermore, the $μN \to τX$ phenomenology, in particular that for the signal and backgrounds, is briefly discussed. Another promising possibility to search for the $e N \to τX$ reaction at an electron-positron linear collider is also discussed. Searches for these reactions would be competitive to studies of rare tau decays and have potential to improve sensitivities to lepton flavor violation significantly.
A review of searches for physics beyond the Standard Model carried out at high energy lepton-hadron and hadron-hadron facilities is presented, with emphasis on topics of interest for future data taking at the upgraded Tevatron $p{\bar p}$ and HERA $ep$ colliders. The status and discovery prospects are discussed for leptoquarks, Technicolour and supersymmetry, forbidden lepton and quark flavour-changing processes, extra gauge bosons, excited states of composite fermions, generic contact interactions and extra compactified dimensions.
Recent results from searches for new physics at HERA are reviewed. Exploiting the uniqueness of lepton-hadron collisions at high energy, searches are performed for electron-quark resonant states (leptoquarks or squarks in R-parity-violating supersymmetry) or excited states of fermions. New phenomena at a very high energy scale, manifested at present energies as effective four-fermion contact interaction, are also investigated, including cases with lepton-flavor violation. Finally, the status of events with a high-energy lepton and missing transverse momentum is presented, resulting in the most stringent constraint on the flavor-changing neutral current t-u-γcoupling which could yield single-top production.
The latest status of searches at HERA for physics beyond the Standard Model is summarized on behalf of the H1 and ZEUS collaborations. Emphasis is put on production of resonant particles accessible within the HERA center-of-mass energy, such as leptoquarks, squarks in R-parity-violating supersymmetry or excited fermions. Most of the results presented here are based on the full available statistics of positron-proton collisions, and also preliminary results from very recent electron-proton running are presented. Results which have been updated since this Ringberg '99 Workshop are also included.