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Register a new userComparing and contrasting the $ u_{mu} to u_{tau}$ and $ u_{mu} to u_s$ solutions to the atmospheric neutrino problem with SuperKamiokande data
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The $ u_{mu} to u_{tau}$ and $ u_{mu} to u_s$ solutions to the atmospheric neutrino problem are compared with SuperKamiokande data. The differences between these solutions due to matter effects in the Earth are calculated for the ratio of $mu$-like to $e$-like events and for up-down flux asymmetries. These quantities are chosen because they are relatively insensitive to theoretical uncertainties in the overall neutrino flux normalisation and detection cross-sections and efficiencies. A $chi^2$ analysis using these quantities is performed yielding $3sigma$ ranges which are approximately given by $(0.725 - 1.0, 4 times 10^{-4} - 2 times 10^{-2} eV^2)$ and $(0.74 - 1.0, 1 times 10^{-3} - 2 times 10^{-2} eV^2)$ for $(sin^2 2theta,Delta m^2)$ for the $ u_{mu} to u_{tau}$ and $ u_{mu} to u_s$ solutions, respectively. Values of $Delta m^2$ smaller than about $2 times 10^{-3}$ eV$^2$ are disfavoured for the $ u_{mu} to u_s$ solution, suggesting that future long baseline experiments should see a positive signal if this scenario is the correct one.
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Neutrino oscillation scenarios involving large angle $ u_{mu} to u_e$ oscillations are disfavoured in the parameter range $Delta m^2/eV^2 >~ 10^{-3}$ by recent results from the CHOOZ reactor-based $bar{ u}_e$ disappearance experiment. For this reason we extend our previous work on up-down asymmetries for various oscillation scenarios by computing up-down asymmetries and the R ratio for the entire conceivable range $10^{-4} - 10^{-1} eV^2$ of $Delta m^2$. Matter effects in the Earth play a crucial role. We perform a $chi^2$ fit to the data. We find that, because of the matter effect, the three-flavour maximal mixing model provides a reasonable fit to SuperKamiokande and CHOOZ data provided that the relevant $Delta m^2$ is in the range $4 times 10^{-4} ~< Delta m^2/eV^2 ~< 1.5 times 10^{-3}$.
We study lepton flavour-violating interactions which could result in the $tau$-lepton production in the $ u_{mu}N$ scattering or in $mu to tau$ conversion on nucleons at high energies. Phenomenological bounds on the strength of $bar{tau} u_{mu}bar{q}q^{}$ interactions are extracted from the combined result of the NOMAD and CHORUS experiments on searching for $ u_{mu} - u_{tau}$ oscillations. Some of these bounds supersede limits from rare decays. We also propose a ``missing energy type experiment searching for $mu - tau$ conversion on nucleons. The experiment can be performed at a present accelerator or at a future neutrino factory.
The potential of performing a combined analysis of the strangeness-changing decays $tau^{-}to K_{S}pi^{-} u_{tau}$ and $tau^{-}to K^{-}eta u_{tau}$ for unveiling the $K^{*}(1410)$ resonance pole parameters is illustrated. Our study is carried out within the framework of Chiral Perturbation Theory, including resonances as explicit degrees of freedom. Resummation of final state interactions are considered through a dispersive parameterization of the required form factors. A considerable improvement in the determination of the pole position with mass $M_{K^{*}(1410)}=1304pm17$ MeV and width $Gamma_{K^{*}(1410)}=171pm62$ MeV is obtained.
We report on a new analysis of neutrino oscillations in MINOS using the complete set of accelerator and atmospheric data. The analysis combines the $ u_{mu}$ disappearance and $ u_{e}$ appearance data using the three-flavor formalism. We measure $|Delta m^{2}_{32}|=[2.28-2.46]times10^{-3}mbox{,eV}^{2}$ (68% C.L.) and $sin^{2}theta_{23}=0.35-0.65$ (90% C.L.) in the normal hierarchy, and $|Delta m^{2}_{32}|=[2.32-2.53]times10^{-3}mbox{,eV}^{2}$ (68% C.L.) and $sin^{2}theta_{23}=0.34-0.67$ (90% C.L.) in the inverted hierarchy. The data also constrain $delta_{CP}$, the $theta_{23}$ octant degeneracy and the mass hierarchy; we disfavor 36% (11%) of this three-parameter space at 68% (90%) C.L.
We observe a net beam-excess of $8.7 pm 6.3$ (stat) $pm 2.4$ (syst) events, above 160 MeV, resulting from the charged-current reaction of $ u_{mu}$ and/or $bar u_{mu}$ on C and H in the LSND detector. No beam related muon background is expected in this energy regime. Within an analysis framework of $pi^0 to u_{mu}bar u_{mu}$, we set a direct upper limit for this branching ratio of $Gamma(pi^0 to u_mu bar u_mu) / Gamma(pi^0 to all) < 1.6 times 10^{-6}$ at 90% confidence level.
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