arXiv subjects

M. Nebot

Publications and source records attributed to M. Nebot.

23 records · Page 2Linked to original sources

arXiv2006

Invariant approach to flavour-dependent CP-violating phases in the MSSM

We use a new weak basis invariant approach to classify all the observable phases in any extension of the Standard Model (SM). We apply this formalism to determine the invariant CP phases in a simplified version of the Minimal Supersymmetric SM with only three non-trivial flavour structures. We propose four experimental measures to fix completely all the observable phases in the model. After these phases have been determined from experiment, we are able to make predictions on any other CP-violating observable in the theory, much in the same way as in the Standard Model all CP-violation observables are proportional to the Jarlskog invariant.

hep-ph↗

arXiv2005

New Physics and Evidence for a Complex CKM

We carefully analyse the present experimental evidence for a complex CKM matrix, even allowing for New Physics contributions to $ε_{K}$, $a_{J/ΨK_S}$, $ΔM_{B_{d}}$, $ΔM_{B_{s}}$, and the $ΔI=1/2$ piece of $B\toρρ$ and $B\toρπ$. We emphasize the crucial r\^ ole played by the angle $γ$ in both providing irrefutable evidence for a complex CKM matrix and placing constraints on the size of NP contributions. It is shown that even if one allows for New Physics a real CKM matrix is excluded at a 99.92% C.L., and the probability for the phase $γ$ to be in the interval $[-170^\circ;-10^\circ]\cup [10^\circ;170^\circ]$ is 99.7%.

hep-ph↗

arXiv2004

The size of chi = arg (-Vts Vtb* Vcs* Vcb) 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 forward-backward asymmetry in e+ e- -> ttbar and the direct production of a new quark.

hep-ph↗

arXiv2004

CPT violation in entangled B0-B0bar states and the demise of flavour tagging

We discuss the demise of flavour tagging due to the loss of the particle-antiparticle identity of neutral B-mesons in the Einstein-Podolsky-Rosen correlated states. Such a situation occurs in cases where the CPT operator is ill-defined, as happens, for example, in quantum gravity models with induced decoherence in the matter sector. The time evolution of the perturbed B0-B0bar initial state, as produced in B-factories, is sufficient to generate new two-body states. For flavour specific decays at equal times, we discuss two definite tests of the two body entanglement: (i) search for the would-be forbidden B0 B0 and B0bar B0bar states; (ii) deviations from the indistinguishable probability between the permuted states B0bar B0 and B0 B0bar.

hep-ph↗

arXiv2002

Unitarity Triangles and the Search for New Physics

Assuming that the Kobayashi-Maskawa mechanism gives the dominant contribution to CP violation at low energies, we propose a novel way of testing the flavour sector of the Standard Model which has the potencial for discovering New Physics. Using 3 x 3 unitarity of the V_{CKM} matrix and choosing a complete set of rephasing invariant phases, we derive a set of exact relations in terms of measurable quantities, namely moduli of V_{CKM} and arguments of rephasing invariant quartets. These tests complement the usual analysis in the ρ, ηplane and, if there is New Physics, may reveal its source.

hep-ph↗