arXiv subjects

Francisco J. Botella

Publications and source records attributed to Francisco J. Botella.

22 records · Page 2Linked to original sources

arXiv2016

Genuine T, CP, CPT asymmetry parameters for the entangled $\boldsymbol{B_d}$ system

The precise connection between the theoretical T, CP, CPT asymmetries, in terms of transition probabilities between the filtered neutral meson $B_d$ states and the experimental asymmetries between the double decay rate intensities for Flavour-CP eigenstate decay products in a B-factory of entangled states, is established. This allows the identification of genuine Asymmetry Parameters in the time distribution of the asymmetries and their measurability by disentangling genuine and possible fake terms. We express the nine asymmetry parameters -- three different observables for each one of the three symmetries -- in terms of the ingredients of the Weisskopf-Wigner dynamical description of the entangled $B_d$-meson states and we obtain a global fit to their values from the BaBar collaboration experimental results. The possible fake terms are all compatible with zero and the information content of the nine asymmetry parameters is indeed different. The non-vanishing $Δ\mathscr S_c^{\rm T} =-0.687\pm 0.020 $ and $Δ\mathscr S_c^{\rm CP}=-0.680\pm 0.021$ are impressive separate direct evidence of Time-Reversal-violation and CP-violation in these transitions and compatible with Standard Model expectations. An intriguing 2$σ$ effect for the Re($θ$) parameter responsible of CPT-Violation appears which, interpreted as an upper limit, leads to $|M_{\bar B^0\bar B^0}-M_{B^0B^0}| < 4.0\times 10^{-5}$ eV at 95\% C.L. for the diagonal flavour terms of the mass matrix. It contributes to the CP-violating $Δ\mathscr C_c^{\rm CP}$ asymmetry parameter in an unorthodox manner -- in its $\cos(ΔM\,t)$ time dependence --, and it is accessible in facilities with non-entangled $B_d$'s, like the LHCb experiment.

hep-ph↗

arXiv2013

Novel T-Violation observable open to any pair of decay channels at meson factories

Quantum Entanglement between the two neutral mesons produced in meson factories has allowed the first indisputable direct observation of Time Reversal Violation in the time evolution of the neutral meson between the two decays. The exceptional meson transitions are directly connected to semileptonic and CP-eigenstate decay channels. The possibility of extending the observable asymmetries to more decay channels confronts the problem of the "orthogonality condition", which can be stated with this tongue-twister: Given a decay channel $f$, Which is the decay channel $f'$ such that the meson state not decaying to $f'$ is orthogonal to the meson state not decaying to $f$? In this paper we propose an alternative $T$-Violation Asymmetry at meson factories which allows its opening to any pair of decay channels. Instead of searching which is the pair of decay channels associated to the $T$-reverse meson transition, we build an asymmetry which tags the initial states of both the Reference and the $T$-reverse meson transitions. This observable filters the appropriate final states by means of two measurable survival probabilities. We discuss the methodology to be followed in the analysis of the new observable and the results expected in specific examples.

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arXiv2008

Small violations of unitarity, the phase in Bs mixing and visible t->cZ decays at the LHC

We show that it is possible to accommodate the observed size of the phase in $B^0_s$--$\bar B^0_s$, mixing in the framework of a model with violation of $3\times 3$ 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 $χ\equiv\arg(-V_{ts}V_{cb}V_{tb}^*V_{cs}^*)$ of order $λ$, to be contrasted with the situation in the Standard Model, where $χ$ is constrained to be of order $λ^2$. We point out that this scenario implies rare top decays $t\to cZ$ at a rate observable at the LHC and $|V_{tb}|$ significantly different from unity. In this framework, one may also account for the observed size of $D^0$--$\bar D^0$ mixing without having to invoke long distance contributions. It is also shown that in the present scenario, the observed size of $D^0$--$\bar D^0$ mixing constrains $χ^\prime\equiv\arg(-V_{cd}V_{us}V_{cs}^*V_{ud}^*)$ to be of order $λ^4$, which is significantly smaller than what is allowed in generic models with violations of $3\times 3$ unitarity.

hep-ph↗

arXiv2007

Reparametrization Invariance, the controversial extraction of $α$ from $B\toππ$ and New Physics

The extraction of the weak phase $α$ from $B\toππ$ decays has been controversial from a statistical point of view, as the frequentist vs. bayesian confrontation shows. We analyse several relevant questions which have not deserved full attention and pervade the extraction of $α$. Reparametrization Invariance proves appropriate to understand those issues. We show that some Standard Model inspired parametrizations can be senseless or inadequate if they go beyond the minimal Gronau and London assumptions: the single weak phase $α$ just in the $ΔI=3/2$ amplitudes, the isospin relations and experimental data. Beside those analyses, we extract $α$ through the use of several adequate parametrizations, showing that there is no relevant discrepancy between frequentist and bayesian results. The most relevant information, in terms of $α$, is the exclusion of values around $α\sim π/4$; this result is valid in the presence of arbitrary New Physics contributions to the $ΔI=1/2$ piece.

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