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G. Sanchez-Colon

Publications and source records attributed to G. Sanchez-Colon.

At least 19 recordsLinked to original sources
arXiv2010

Vus and neutron beta decay

We discuss the effect of the recent change of $V_{\rm us}$ by three standard deviations on the standard model predictions for neutron beta decay observables. We also discuss the effect the experimental error bars of $V_{\rm us}$ have on such predictions. Refined precision tests of the standard model will be made by a combined effort to improve measurements in neutron beta decay and in strangeness-changing decays. By itself the former will yield very precise measurements of $V_{\rm ud}$ and make also very precise predictions for $V_{\rm us}$.

hep-ph↗
arXiv2010

Evidence against manifest right-handed currents in neutron beta decay

Bounds and presence of manifest right handed currents in neutron beta decay are reviewed. Assuming the unitarity of the Cabibbo-Kobayashi-Maskawa matrix, current experimental situation imposes very stringent limits on the mixing angle, $-0.00077<ζ<0.00089$, and on the mass eigenstate, $M_2({\rm GeV})\in(291.4,439.9)$, in contradiction with the established lower bound on $M_2$.

hep-ph↗
arXiv2008

Bounds on quark mass matrices elements due to measured properties of the mixing matrix and present values of the quark masses

We obtain constraints on possible structures of mass matrices in the quark sector by using as experimental restrictions the determined values of the quark masses at the $M_Z$ energy scale, the magnitudes of the quark mixing matrix elements $V_{\rm ud}$, $V_{\rm us}$, $V_{\rm cd}$, and $V_{\rm cs}$, and the Jarlskog invariant $J(V)$. Different cases of specific mass matrices are examined in detail. The quality of the fits for the Fritzsch and Stech type mass matrices is about the same with $χ^2/{\rm dof}=4.23/3=1.41$ and $χ^2/{\rm dof}=9.10/4=2.28$, respectively. The fit for a simple generalization (one extra parameter) of the Fritzsch type matrices, in the physical basis, is much better with $χ^2/{\rm dof}=1.89/4=0.47$. For comparison we also include the results using the quark masses at the 2 GeV energy scale. The fits obtained at this energy scale are similar to that at $M_Z$ energy scale, implying that our results are unaffected by the evolution of the quark masses from 2 to 91 GeV.

hep-ph↗
arXiv2004

Mirror matter admixtures in K_L \to γγ

Based on possible albeit tiny, admixtures of mirror matter in ordinary mesons we study the K_L \to γγtransition. We find that this process can be described with a small SU(3) symmetry breaking of only 3%. We also determine the eta-eta' mixing angle and the pseudoscalar decay constants. The results for these parameters are consistent with some obtained in the literature. They favor two recent determinations; one based on two analytical constraints, and another one based on next-to-leading order power corrections.

hep-ph↗
arXiv2003

Mirror matter admixtures and isospin breaking in the ΔI=1/2 rule in Ω^- two body non-leptonic decays

We discuss a description of Ω^- two body non-leptonic decays based on possible, albeit tiny, admixtures of mirror matter in ordinary hadrons. The ΔI=1/2 rule enhancement is obtained as a result of isospin symmetry and, more importantly, the rather large observed deviations from this rule result from small isospin breaking. This analysis lends support to the possibility that the enhancement phenomenon observed in low energy weak interactions may be systematically described by mirror matter admixtures in ordinary hadrons.

hep-ph↗
arXiv2001

A priori mixed hadrons, hyperon non-leptonic decays, and the |ΔI|=1/2 rule

The |ΔI|=1/2 rule in non-leptonic decays of hyperons can be naturally understood by postulating a priori mixed physical hadrons, along with the isospin invariance of the responsible transition operator. It is shown that this operator can be identified with the strong interaction Yukawa hamiltonian.

hep-ph↗
arXiv2001

Flavor symmetry breaking, baryons magnetic moments, and low energy phenomenology of hadrons

A priori mixings of eigenstates in physical states are quantum mechanical effects well known in several realms of physics. The possibility that such effects are also present in particle physics, in the form of mixings that break flavor and parity symmetries, is studied. Applications to non-leptonic and weak radiative decays of hyperons are discussed. The results are very encouraging but should be improved by eventually including the W and Z contributions, assumed small (non-enhanced) in this work.

hep-ph↗
arXiv2000

An estimate of a lower bound on the masses of mirror baryons

We consider the most favorable conditions to indirectly observe the mixing of ordinary and mirror hadrons in non-leptonic and weak radiative decays of hyperons. This allows us to set a lower bound on the masses of mirror baryons. This bound turns out to be impressively high, of the order of $10^6$GeV.

hep-ph↗
arXiv1999

A priori mixing of mesons and the |Delta I|=1/2 rule in K\toππ

We consider the hypothesis of a priori mixings in the mass eigenstates of mesons to obtain the |Delta I|=1/2 rule in K\toππ. The Hamiltonian responsible for the transition is the strong interacting one. The experimental data are described using the isospin symmetry relations between the strong coupling constants.

hep-ph↗
arXiv1998

A Priori Mixed Hadrons, Weak Radiative and Non-leptonic Decays of Hyperons

A priori mixings of eigenstates in physical states are quantum mechanical effects well known in several realms of physics. The possibility that such effects are also present in particle physics, in the form of flavor and parity mixings, is studied. Applications to weak radiative and non-leptonic decays of hyperons are discussed.

hep-ph↗
arXiv1998

On the universality of the a priori mixing angles in weak radiative decays of hyperons

Strong-flavor and parity a priori mixing in hadrons are shown to describe well the experimental evidence on weak radiative decays of hyperons. An independent determination of the a priori mixing angles is performed. The values obtained for them are seen to have a universality-like property, when compared to their values in non-leptonic decays of hyperons.

hep-ph↗
arXiv1998

Effective operator contributions to the oblique parameters

We present a model and process independent study of the contributions from non-Standard Model physics to the oblique parameters S, T and U. We show that within an effective lagrangian parameterization the expressions for the oblique parameters in terms of observables are consistent, while those in terms of the vector-boson vacuum polarization tensors are ambiguous. We obtain the constraints on the scale of new physics derived from current data on S, T and U and note that deviations in U from its Standard Model value would favor a scenario where the underlying physics does not decouple.

hep-ph↗
arXiv1998

A detailed determination of the a priori mixing angles in non-leptonic decays of hyperons

Non-leptonic Decays of Hyperons can provide a detailed determination of the a priori mixing angles that appear in physical hadrons in the approach in which non-perturbative flavor and parity violations are present in tiny pieces of the hadron mass operator. The determination of such angles in these decays will provide a bench mark to test their necessary universality-like property in other types of decays. Our main result is that the magnitudes of the a priori mixing angles can be determined quite accurately.

hep-ph↗
arXiv1998

Hyperon Non-leptonic Decays, the |Delta I|=1/2 Rule, and A Priori Mixed Hadrons

The $|ΔI|=1/2$ rule in non-leptonic decays of hyperons can be naturally understood by postulating a priori mixed physical hadrons, along with the isospin invariance of the responsible transition operator. It is shown that this operator can be identified with the strong interaction Yukawa hamiltonian. The experimental amplitudes are well reproduced.

hep-ph↗
arXiv1998

Masses, Magnetic Moments, and Semileptonic Decays of Spin 1/2 Baryons with Sea Contribution

The spin 1/2 baryons are pictured as a composite system made out of a "core" of three valence quarks (as in the simple quark model) surrounded by a "sea" (of gluon and $q\bar{q}$ pairs) which is specified by its total quantum numbers. We assume the sea is a SU(3) flavor octet with spin 0 or 1 but no color. This model, considered earlier, is used to obtain simultaneous fits for masses, magnetic moments and $G_A/G_V$ for semileptonic decays. These fits give predictions for nucleon spin distributions in reasonable agreement with experiment.

hep-ph↗
arXiv1998

Quark Mixing Possibilities in Extensions of the Standard Model and the Electromagnetic Current

The existence of new quarks may lead to their mixing with ordinary quarks. We are particularly interested in studying the consequences such mixings could have upon the electromagnetic current. We find that new strong flavor and parity violating electromagnetic interactions may exist. To be specific, for our analysis we work with the model: $SU_2 \otimes U_1 \otimes \hat{SU}_2 \otimes \hat{U}_1$, which doubles the standard electroweak sector, both in gauge bosons and in quarks.

hep-ph↗