Looking for Delta I=5/2 amplitude components in B ->pi pi and B ->rho rho experiments

We discuss how experiments measuring B -> pi pi and B -> rho rho may be used to search for a Delta I = 5/2 amplitude component. This component could be the explanation for a recent (albeit very tentative) hint from B(Bbar) -> rho rho decays that the isospin triangles do not close.

D-0-(D-0)over-bar mixing in the weak-gauged U(4)(L)circle times U(4)(R) chiral Lagrangian model

The D-0- mixing is analyzed in a weak gauged U(4)(L) x U(4)(R) chiral lagrangian model where the electroweak interaction is introduced as a gauge theory over the meson degrees of freedom. This model allows a particular realization of the G.I.M. mechanism and then could be useful in the study of processes where G.I.M. suppression is effective. As a test of the model we have also analyzed the K-0- mixing. We find am, in good agreement with the experimental result and we show that the D-0- mixing is very much suppressed in agreement with previous estimates in the Heavy Quark expansion framework.

Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays

When studying B decays within the Standard Model, it is customary to use the unitarity of the CKM matrix in order to write the decay amplitudes in terms of only two of the three weak phases which appear in the various diagrams. Occasionally, it is mentioned that those two weak phases can be used in order to describe any decay amplitude, even beyond the Standard Model. Here we point out that, when describing a generic decay amplitude, the two weak phases can be chosen completely at will, and we study the behavior of the decay amplitudes under changes in the two weak phases chosen as a basis. Of course, physical observables cannot depend on such reparametrizations. This has an impact in discu…

Measurements of new physics in B -> pi pi decays

If new physics (NP) is present in B -> pi pi decays, it can affect the isospin I=2 or I=0 channels. In this paper, we discuss various methods for detecting and measuring this NP. The techniques have increasing amounts of theoretical hadronic input. If NP is eventually detected in B -> pi pi -- there is no evidence for it at present -- one will be able to distinguish I=2 and I=0, and measure its parameters, using these methods.

Epsilon-Type contribution to baryon asymmetry from colored higgs triplets

In scenarios where the cosmological baryon asymmetry is generated in the decay of heavy colored Higgs triplets at the one-loop level (at least two triplets are needed), it is shown that in addition to the conventional triangle loop (ε'-type effect), a new kind of diagram must be considered. This new type of diagram has its origin in the mixing of the two Higgs fields (ε-type effect). The mixing of the two Higgs fields violates CP provided they have at least two common decay channels. For small mixing angles, the new contribution can be bigger than the conventional one.

Neutrino magnetic moment and the process neutrino e ---> neutrino e gamma

The contribution of a neutrino magnetic moment mu(nu) to the cross section of the process ve(-) --> ve(-)gamma has been calculated and compared with the Standard Electroweak one. The radiative process allows to reach low enough values of Q(2) without the need to operate at very small energies of recoil electrons. Regions in the phase space which are more favourable to set bounds on mu(v) are suggested.

Análisis de la estructura de corrientes Cargadas y Neutras a partir de procesos Nucleares Semileptonicos

The size of X arg(-V-ts V-tb(*) V-cs(*) V-cb) and physics beyond the standard model

We analyse the allowed range of values of chi, both in the Standard Model and in models with New Physics, pointing out that a relatively large value of chi, e.g. of order lambda, is only possible in models where the unitarity of the 3x3 Cabibbo-Kobayashi-Maskawa matrix is violated through the introduction of extra Q=2/3 quarks. We study the interesting case where the extra quark is an isosinglet, determining the allowed range for chi and the effect of a large chi on various low-energy observables, such as CP asymmetries in B meson decays. We also discuss the correlated effects which would be observable at high energy colliders, like decays t -> cZ, modifications of the cross section and for…

Can one detect new physics in I=0 and/or I=2 contributions to the decays B ->pi pi

We study the effects of new-physics contributions to B --> pi pi decays, which can be parametrized as four new complex quantities. A simple analysis is provided by utilizing the reparametrization invariance of the decay amplitudes. We find that six quantities can be reabsorbed into the definitions of Standard Model-like parameters. As a result, the usual isospin analysis provides only two constraints on new physics which are independent of estimates for the Standard Model contributions. In particular, we show that one is not sensitive to new physics affecting the I=0 amplitudes. On the other hand, I=2 new physics can be detected, and its parameters can be measured by using independent deter…

Algunas consideraciones sobre la masa (o masa no hay más que una)

This article presents sorne reasoned arguments against relativistic mass as a basic concept in Theory of Special Relativity. Relativistic mass limitations are examined and invariant mass is defended as the only one. Finally, a didactic proposal, consistent with the use of invariable mass, is presented in order to introducing rnass and energy concepts at Bachillerato.

Bounds on gamma from CP violation measurements in B ->pi(+)pi(-) and B ->psi K-S

We study the determination of gamma from CP-violating observables in B -> pi+ pi- and B -> psi K_S. This determination requires theoretical input to one combination of hadronic parameters. We show that a mild assumption about this quantity may allow bounds to be placed on gamma, but we stress the pernicious effects that an eightfold discrete ambiguity has on such an analysis. The bounds are discussed as a function of the direct (C) and interference (S) CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and their behavior in the presence of new physics effects in B-Bbar mixing is studied. (V2: Misprints corrected. Slightly improved discussion.)

Small violations of unitarity, the phase in B-s(0) and visible t-> cZ decays at the LHC

We show that it is possible to accommodate the observed size of the phase in B-s(0) - (B) over bar (0)(s) mixing in the framework of a model with violation of 3 x 3 unitarity. This violation is associated to the presence of a new Q = 2/3 isosinglet quark T, which mixes both with t and c and has a mass not exceeding 500 GeV. The crucial point is the fact that this framework allows for chi equivalent to arg(-VtsVcbVtb*V-cs*) of order lambda, to be contrasted with the situation in the standard model, where chi is constrained to be of order lambda(2). We point out that this scenario implies rare top decays t -> cZ at a rate observable at the LHC and vertical bar V-tb vertical bar significantly …