A. Donini

The silver channel at the neutrino factory

Abstract We notice that looking for ν e → ν τ at the same time as ν e → ν μ oscillations could significantly help to reduce the errors in the leptonic CP-violating phase δ measurement. We show how the ν e → ν μ (“golden”) and ν e → ν τ (“silver”) transitions observed at an OPERA-like 2 kton lead-emulsion detector at L =732xa0km, in combination with the ν e → ν μ transitions observed at a 40xa0kton magnetized iron detector with a baseline of L =3000xa0km, strongly reduce the so-called ( θ 13 , δ ) ambiguity. We also show how a moderate increase in the OPERA-like detector mass (4xa0kton instead of 2xa0kton) completely eliminates the clone regions even for small values of θ 13 .

Non-Perturbative Renormalization of Lattice Four-Fermion Operators without Power Subtractions

Abstract. A general nonperturbative analysis of the renormalization properties of

B-parameters for Delta S=2 supersymmetric operators

Delta I=3/2

Renormalization group invariant matrix elements of ΔS=2 and ΔI=3/2 four-fermion operators without quark masses

four-fermion operators in the framework of lattice regularization with Wilson fermions is presented. We discuss the nonperturbative determination of the operator renormalization constants in the lattice regularization independent (RI or MOM) scheme. We also discuss the determination of the finite lattice subtraction coefficients from Ward identities. We prove that, at large external virtualities, the determination of the lattice mixing coefficients, obtained using the RI renormalization scheme, is equivalent to that based on Ward identities, in the continuum and chiral limits. As a feasibility study of our method, we compute the mixing matrix at several renormalization scales, for three values of the lattice coupling

Towards N =1 Super-Yang{Mills on the Lattice

beta

Instantons and the A (2) condensate

, using the Wilson and tree-level improved SW-Clover actions.

Lattice B-parameters for ΔS=2 and ΔI=3/2 operators

Abstract We present a calculation of the matrix elements of the most general set of ΔS =2 dimension-six four-fermion operators. The values of the matrix elements are given in terms of the corresponding B -parameters. Our results can be used in many phenomenological applications, since the operators considered here give important contributions to K 0 – K 0 mixing in several extensions of the Standard Model (supersymmetry, left-right symmetric models, multi-Higgs models etc.). The determination of the matrix elements improves the accuracy of the phenomenological analyses intended to put bounds on basic parameters of the different models, as for example the pattern of the sfermion mass matrices. The calculation has been performed on the lattice, using the tree-level improved Clover action at two different values of the strong coupling constant ( β =6/ g 0 2 ( a )=6.0 and 6.2, corresponding to a −1 =2.1 and 2.7 GeV respectively), in the quenched approximation. The renormalization constants and mixing coefficients of the lattice operators have been obtained non-perturbatively.

The 2+2 and 3+1 Four-Family Neutrino Mixing at the Neutrino Factory

Abstract We introduce a new parameterization of four-fermion operator matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties. In order to simplify the matching between lattice and continuum renormalization schemes, we express our results in terms of renormalization group invariant B -parameters which are renormalization-scheme and scale independent. As an application of our proposal, matrix elements of ΔI =3/2 and SUSY ΔS =2 operators have been computed. The calculations have been performed using the tree-level improved Clover lattice action at two different values of the strong coupling constant ( β =6/ g 2 =6.0 and 6.2), in the quenched approximation. Renormalization constants and mixing coefficients of lattice operators have been obtained non-perturbatively. Using lowest order χ PT, we also obtain 〈 ππ | O 7 | K 〉 NDR I =2 =(0.11±0.02) GeV 4 and 〈 ππ | O 8 | K 〉 NDR I =2 =(0.51±0.05) GeV 4 at μ =2 GeV.

Non-perturbative renormalisation of the lattice ΔS = 2 four-fermion operator

Abstract We consider the lattice regularization of N = 1 supersymmetric Yang-Mills theory with Wilson fermions. This formulation breaks supersymmetry at any finite lattice spacing; we discuss how Ward identities can be used to define a supersymmetric continuum limit, which coincides with the point where the gluino becomes massless. As a first step towards the understanding of the zero gluino-mass limit, we present results on the quenched low-lying spectrum of SU(2) N = 1 super-Yang-Mills, at β = 2.6 on a V = 16 3 × 32 lattice, in the OZI approximation. Our results, in spite of the quenched and OZI approximations, are in remarkable agreement with theoretical predictions in the supersymmetric theory, for the states with masses which are not expected to get a large contribution from fermion loops.

Telling three from four neutrinos at the neutrino factory

We argue that the