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We describe a possible search for muonic radioactivity from lead nuclei using the base elements (bricks composed by lead and nuclear emulsion sheets) of the long-baseline OPERA neutrino experiment. We present the results of a Monte Carlo simulation concerning the expected event topologies and estimates of the background events. Using few bricks, we could reach a good sensitivity level.
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A search for an exotic natural radioactivity of lead nuclei, using nuclear emulsion sheets as detector, is described. We discuss the experimental set-up of a test performed at the Gran Sasso National Laboratory (Italy), the event simulation, data analysis and preliminary results.
Lepton family number violation is tested by searching for $mu^+to e^+X^0$ decays among the 5.8$times 10^8$ positive muon decay events analyzed by the TWIST collaboration. Limits are set on the production of both massless and massive $X^0$ bosons. The large angular acceptance of this experiment allows limits to be placed on anisotropic $mu^+to e^+X^0$ decays, which can arise from interactions violating both lepton flavor and parity conservation. Branching ratio limits of order $10^{-5}$ are obtained for bosons with masses of 13 - 80 MeV/c$^2$ and with different decay asymmetries. For bosons with masses less than 13 MeV/c$^{2}$ the asymmetry dependence is much stronger and the 90% limit on the branching ratio varies up to $5.8 times 10^{-5}$. This is the first study that explicitly evaluates the limits for anisotropic two body muon decays.
The possible occurence of highly deformed configurations is investigated in the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si + $^{12}$C and $^{28}$Si + $^{28}$Si reactions, respectively, by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments (A $geq$ 6) and their associated light charged particles (p, d, t, and $alpha$-particles) have been collected at the IReS Strasbourg VIVITRON Tandem facility with two bombarding energies $E_{lab}(^{28}$Si) = 112 and 180 MeV by using the ICARE charged particle multidetector array, which consists of nearly 40 telescopes. The measured energy spectra, velocity distributions, in-plane and out-of-plane angular correlations are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Although significant deformation effects at high spin are needed, the remaining disagreement observed in the $^{28}$Si + $^{12}$C reaction for the S evaporation residue suggests an unexpected large unstable $^{8}$Be cluster emission of a binary nature.
Data from the MINOS experiment has been used to search for mixing between muon neutrinos and muon antineutrinos using a time-independent Lorentz-violating formalism derived from the Standard-Model Extension (SME). MINOS is uniquely capable of searching for muon neutrino-antineutrino mixing given its long baseline and ability to distinguish between neutrinos and antineutrinos on an event-by-event basis. Neutrino and antineutrino interactions were observed in the MINOS Near and Far Detectors from an exposure of 10.56$times10^{20}$ protons-on-target from the NuMI neutrino-optimized beam. No evidence was found for such transitions and new, highly stringent limits were placed on the SME coefficients governing them. We place the first limits on the SME parameters $(c_{L})^{TT}_{mumu} $ and $(c_{L})^{TT}_{tautau}$ at $-8.4times10^{-23} < (c_{L})^{TT}_{mumu} < 8.0times10^{-23}$ and $-8.0times10^{-23} < (c_{L})^{TT}_{tautau} < 8.4times10^{-23}$, and the worlds best limits on the $tilde{g}^{ZT}_{muoverline{mu}}$ and $tilde{g}^{ZT}_{tauoverline{tau}}$ parameters at $|tilde{g}^{ZT}_{muoverline{mu}}| < 3.3times 10^{-23}$ and $|tilde{g}^{ZT}_{tauoverline{tau}}| < 3.3times 10^{-23}$, all limits quoted at $3sigma$.
We report results of a search for oscillations involving a light sterile neutrino over distances of 1.04 and $735,mathrm{km}$ in a $ u_{mu}$-dominated beam with a peak energy of $3,mathrm{GeV}$. The data, from an exposure of $10.56times 10^{20},textrm{protons on target}$, are analyzed using a phenomenological model with one sterile neutrino. We constrain the mixing parameters $theta_{24}$ and $Delta m^{2}_{41}$ and set limits on parameters of the four-dimensional Pontecorvo-Maki-Nakagawa-Sakata matrix, $|U_{mu 4}|^{2}$ and $|U_{tau 4}|^{2}$, under the assumption that mixing between $ u_{e}$ and $ u_{s}$ is negligible ($|U_{e4}|^{2}=0$). No evidence for $ u_{mu} to u_{s}$ transitions is found and we set a world-leading limit on $theta_{24}$ for values of $Delta m^{2}_{41} lesssim 1,mathrm{eV}^{2}$.
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