Lepton Flavor Violation in a Long Baseline Experiment

We evaluate the size of a coupling for a lepton flavor violating interaction with neutrinos (nLFV) in the minimal supersymmetric standard model with right-handed neutrinos (MSSMRN). It is expected that the nLFV interactions are detected in a long baseline neutrino oscillation experiment. We here deal with $\mu^{-} \to e^{-} \bar{\nu}_{e} \nu_{\tau}$ in $\nu_{\mu} \to \nu_{\tau}$ channel at a neutrino factory. First, we show the numerical study on feasibility to observe such interaction and point out that we can search for them with some oscillation channels. Next, we make a numerical calculation for the size of the nLFV coupling in the framework of the MSSMRN. A long baseline experiment is sensitive not only to the lepton mixings in the standard model but also to new physics effect.Comment: 3 pages, 3 figures, to appear in the proceedings of the 6th International Workshop on Neutrino Factory and Superbeams NuFact04, Osaka,Japan, July 26 - August 1, 200

Discovery reach for non-standard interactions in a neutrino factory

We study the discovery reach for Non-Standard Interactions (NSIs) in a neutrino factory experiment. After giving a theoretical, but model-independent, overview of the most relevant classes of NSIs, we present detailed numerical results for some of them. Our simulations take into account matter effects, uncertainties in the neutrino oscillation parameters, systematical errors, parameter correlations, and degeneracies. We perform scans of the parameter space, and show that a neutrino factory has excellent prospects of detecting NSIs originating from new physics at around 1 TeV, which is a scale favored by many extensions of the standard model. It will also turn out that the discovery reach depends strongly on the standard and non-standard CP violating phases in the Lagrangian.Comment: RevTeX 4, 10 pages, 5 figures, extended discussion of systematical errors and of existing bounds, matches published versio

Neutrino factory optimization for non-standard interactions

We study the optimization of a neutrino factory with respect to non-standard neutral current neutrino interactions, and compare the results to those obtained without non-standard interactions. We discuss the muon energy, baselines, and oscillation channels as degrees of freedom. Our conclusions are based on both analytical calculations and on a full numerical simulation of the neutrino factory setup proposed by the international design study (IDS-NF). We consider all possible non-standard parameters, and include their complex phases. We identify the impact of the different parameters on the golden, silver, and disappearance channels. We come to the conclusion that, even in the presence of non-standard interactions, the performance of the neutrino factory hardly profits from a silver channel detector, unless the muon energy is significantly increased compared to the IDS-NF setup. Apart from the dispensable silver channel detector, we demonstrate that the IDS-NF setup is close to optimal even if non-standard interactions are considered. We find that one very long baseline is a key component in the search for non-standard interactions, in particular for |\epsilon^m_{\mu\tau}| and |\epsilon^m_{\tau\tau}|.Comment: LaTeX, 30 pages, 7 figures, 1 tabl

Effective field theory approach to b→sℓℓ(′)b\to s\ell\ell^{(\prime)}, B→K(∗)ννˉB\to K^{(*)}\nu\bar{\nu} and B→D(∗)τνB\to D^{(*)}\tau\nu with third generation couplings

LHCb reported anomalies in $B\to K^* \mu^+\mu^-$, $B_s\to\phi\mu^+\mu^-$ and $R(K)=B\to K \mu^+\mu^-/B\to K e^+e^-$. Furthermore, BaBar, BELLE and LHCb found hints for the violation of lepton flavour universality violation in $R(D^{(*)})=B\to D^{(*)}\tau\nu/B\to D^{(*)}\ell\nu$. In this note we reexamine these decays and their correlations to $B\to K^{(*)}\nu\bar{\nu}$ using gauge invariant dim-6 operators. For the numerical analysis we focus on scenarios in which new physics couples, in the interaction eigenbasis, to third generation quarks and lepton only. We conclude that such a setup can explain the $b\to s\mu^+\mu^-$ data simultaneously with $R(D^{(*)})$ for small mixing angles in the lepton sector (of the order of $\pi/16$) and very small mixing angles in the quark sector (smaller than $V_{cb}$). In these region of parameter space $B\to K^{(*)}\tau\mu$ and $B_s\to \tau\mu$ can be order $10^{-6}$. Possible UV completions are briefly discussed.Comment: 7 pages, 3 figure

Proton decay and light sterile neutrinos

Within the standard model, non-renormalizable operators at dimension six ($d=6$) violate baryon and lepton number by one unit and thus lead to proton decay. Here, we point out that the proton decay mode with a charged pion and missing energy can be a characteristic signature of $d=6$ operators containing a light sterile neutrino, if it is not accompanied by the standard $\pi^0e^+$ final state. We discuss this effect first at the level of effective operators and then provide a concrete model with new physics at the TeV scale, in which the lightness of the active neutrinos and the stability of the proton are related.Comment: 7 pages, 2 figures, published versio