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Ruben Flores-Mendieta

Publications and source records attributed to Ruben Flores-Mendieta.

At least 37 records · Page 2Linked to original sources
arXiv2012

Radiative corrections to the Dalitz plot of K_{l3}^\pm decays: Contribution of the four-body region

We calculate the radiative corrections to the Dalitz plot of K_{l3}^\pm decays to order (alpha/pi)(q/M_1), where q is the momentum transfer and M_1 is the mass of the kaon. We restrict the analysis to the so-called four-body region, which arises when no discrimination of real photons is made either kinematically or experimentally. We present our results in two ways: the first one with the triple integration over the photon kinematical variables ready to be performed numerically and the second one in a fully analytical form. Our results can be useful in experimental analyses of the Dalitz plot, by evaluating the model-independent coefficients of the quadratic products of the form factors; we provide some numbers as a case example. We find a small, albeit non-negligible, contribution from the four-body region to the radiative correction to the total decay rate of K_{l3}^\pm decays.

hep-ph↗
arXiv2011

Radiative corrections to the Dalitz plot of K_{l3}^\pm decays

We calculate the model-independent radiative corrections to the Dalitz plot of K_{l3}^\pm decays to order (α/π)(q/M_1), where q is the momentum transfer and M_1 is the mass of the kaon. The final results are presented, first, with the triple integration over the variables of the bremsstrahlung photon ready to be performed numerically and, second, in an analytical form. These two forms are useful to crosscheck on one another and with other calculations. This paper is organized to make it accessible and reliable in the analysis of the Dalitz plot of precision experiments and is not compromised to fixing the form factors at predetermined values. It is assumed that the real photons are kinematically discriminated. Otherwise, our results have a general model-independent applicability.

hep-ph↗
arXiv2009

Baryon magnetic moments in large-N_c chiral perturbation theory

The baryon magnetic and transition magnetic moments are computed in heavy baryon chiral perturbation theory in the large-N_c limit, where N_c is the number of colors. One-loop nonanalytic corrections of orders m_q^{1/2} and m_q ln m_q are incorporated into the analysis, where contributions of both intermediate octet and decuplet baryon states are explicitly included. Expressions are obtained in the limit of vanishing baryon mass differences and compared with the current experimental data. Furthermore, a comparison with conventional heavy baryon chiral perturbation theory is carried out for three light quarks flavors and at the physical value N_c=3.

hep-ph↗
arXiv2008

Radiative corrections to the three-body region of the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons

We have calculated the radiative corrections to the Dalitz plot of baryon semileptonic decays with angular correlation between polarized emitted baryons and charged leptons. This work covers both charged and neutral decaying baryons and is restricted to the so-called three-body region of the Dalitz plot. Also it is specialized at the center-of-mass frame of the emitted baryon. We have considered terms up to order (alpha/pi)(q/M_1)^0, where q is the momentum-transfer and M_1 is the mass of the decaying baryon, and neglected terms of order (alpha/pi)(q/M_1)^n$ for n >= 1. The expressions displayed are ready to obtain numerical results, suitable for model-independent experimental analyses.

hep-ph↗
arXiv2007

Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying baryon and emitted charged lepton: Effects of the four-body region

Analytical radiative corrections of order (alpha/pi)(q/M) are calculated for the four-body region of the Dalitz plot of baryon semileptonic decays when the s1.l correlation is present. Once the final result is available, it is possible to exhibit it in terms of the corresponding final result of the three-body region following a set of simple changes in the latter, except for a few exceptions. We cover two cases, a charged and a neutral polarized decaying baryon.

hep-ph↗
arXiv2007

Baryon semileptonic decays: the Mexican contribution

We give a detailed account of the techniques to compute radiative corrections in baryon semileptonic decays developed over the years by Mexican collaborations. We explain how the method works by obtaining an expression for the Dalitz plot of semileptonic decays of polarized baryons including radiative corrections to order ${\mathcal O}(αq/πM_1)$, where $q$ is the four-momentum transfer and $M_1$ is the mass of the decaying baryon. From here we compute the totally integrated spin angular asymmetry coefficient of the emitted baryon and compare its value with other results.

hep-ph↗
arXiv2006

Renormalization of the baryon axial vector current in large-N_c chiral perturbation theory

The baryon axial vector current is computed at one-loop order in heavy baryon chiral perturbation theory in the large-N_c limit, where N_c is the number of colors. Loop graphs with octet and decuplet intermediate states cancel to various orders in N_c as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. These cancellations are explicitly shown for the general case of N_f flavors of light quarks. In particular, a new generic cancellation is identified in the renormalization of the baryon axial vector current at one-loop order. A comparison with conventional heavy baryon chiral perturbation theory is performed at the physical values N_c=3, N_f=3.

hep-ph↗
arXiv2006

Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted baryons: Effects of the four-body region

Analytical radiative corrections of order (α/π)(q/M_1) are calculated for the four-body region of the Dalitz plot of baryon semileptonic decays when the s_1 \cdot p_2 correlation is present. Once the final result is available, it is possible to exhibit it in terms of the corresponding final result of the three-body region following a set of simple changes in the latter. We cover two cases, a charged and a neutral polarized decaying baryon.

hep-ph↗
arXiv2005

Precision radiative corrections to the Dalitz plot of baryon semileptonic decays including the spin-momentum correlation of the decaying baryon and the emitted charged lepton

We calculate the radiative corrections to the angular correlation between the polarization of the decaying baryon and the direction of the emitted charged lepton in the semileptonic decays of spin one-half baryons to order (α/π)(q/M_1). The final results are presented, first, with the triple integration of the bremsstrahlung photon ready to be performed numerically and, second, in an analytical form. A third presentation of our results in the form of numerical arrays of coefficients to be multiplied on the quadratic products of form factors is discussed. This latter may be the most practical one to use in Monte Carlo simulations. A series of crosschecks is performed. The results are useful in the analysis of the Dalitz plot of precision experiments involving light and heavy quarks and is not compromised to fixing the form factors at predetermined values. It is assumed that the real photons are kinematically discriminated. Otherwise, our results have a general model-independent applicability.

hep-ph↗
arXiv2005

Baryon vector and axial-vector currents in the 1/N_c expansion

The derivation of the 1/N_c expansions for the baryon vector and axial-vector currents, in the SU(3) symmetry limit and including perturbative SU(3) breaking, is reviewed. Symmetry breaking effects in the hyperon semileptonic decay form factors are reanalyzed. Fits to experimental data yield corrections to the leading vector and axial-vector form factors consistent with expectations. The values of the Cabibbo-Kobayashi-Maskawa matrix elements V_{ud} and V_{us} also extracted from the analysis are comparable to the ones recommended by the Particle Data Group.

hep-ph↗
arXiv2004

Numerical precision radiative corrections to the Dalitz plot of light and heavy quark unpolarized baryon semileptonic decays. The cases Xi^0 \to Sigma^+ e \barν and Λ_c^+ \to Λe^+ ν

We propose and discuss a numerical use of our previous precision results for the radiative corrections to unpolarized spin one-half baryon semileptonic decays, which is not compromised to fixing the form factors at prescribed values. We present various crosschecks and comparisons with other results available in the literature of such analytical radiative corrections. Our analysis, however, is general and applies to all charge assignments to the baryons allowed by heavy quarks. The procedure is exemplified with the processes Ξ^0 \to Σ^+ e\barν and Λ_c^+ \to Λe^+ ν.

hep-ph↗
arXiv2004

Numerical precision radiative corrections to the Dalitz plot of baryon semileptonic decays including the spin-momentum correlation of the decaying and emitted baryons

We calculate the radiative corrections to the angular correlation between the polarization of the decaying and the direction of the emitted spin one-half baryons in the semileptonic decay mode. The final results are presented, first, with the triple integration of the bremsstrahlung photon ready to be performed numerically and, second, in an analytical form. A third presentation of our results in the form of numerical arrays of coefficients to be multiplied by the quadratic products of form factors is discussed. This latter may be the most practical one to use in Monte Carlo simulations. A series of crosschecks is performed. Previous results to order (alpha/pi)(q/M_1) for the decays of unpolarized baryons are reviewed, too, where q is the momentum transfer and M_1 is the mass of the decaying baryon. This paper is self-contained and organized to make it accessible and reliable in the analysis of the Dalitz plot of precision experiments involving heavy quarks and is not compromised to fixing the form factors at predetermined values. It is assumed that the real photons are kinematically discriminated. Otherwise, our results have a general model-independent applicability.

hep-ph↗
arXiv2004

V_{us} from hyperon semileptonic decays

A model-independent determination of the CKM matrix element V_{us} from five measured strangeness-changing hyperon semileptonic decays is performed. Flavor SU(3) symmetry breaking effects in the leading vector and axial-vector form factors are analyzed in the framework of the 1/N_c expansion of QCD. A fit to experimental data allows one to extract the value V_{us}=0.2199\pm 0.0026, which is comparable to the one from K_{e3} decays. This reconciliation is achieved through second-order symmetry breaking effects of a few percent in the form factors f_1, which increase their magnitudes over their SU(3) predictions.

hep-ph↗
arXiv2002

Radiative corrections to all charge assignments of heavy quark baryon semileptonic decays

In semileptonic decays of spin-1/2 baryons containing heavy quarks up to six charge assignments for the baryons and lepton are possible. We show that the radiative corrections to four of these possibilities can be directly obtained from the final results of the two possibilities previously studied. There is no need to recalculate integrals over virtual or real photon momentum or any traces.

hep-ph↗
arXiv2002

Topics on heavy baryon chiral perturbation theory in the large N_c limit

We compute nonanalytical pion-loop corrections to baryon masses in a combined expansion in chiral symmetry breaking and 1/N_c, where N_c is the number of colors. Specifically, we compute flavor-27 baryon mass splittings at leading order in chiral perturbation theory. Our results, at the physical value N_c=3, are compared with the expressions obtained in heavy baryon chiral perturbation theory with no 1/N_c expansion.

hep-ph↗
arXiv2001

Radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted hyperons: effects of the four-body region

We obtain a model-independent expression for the complete Dalitz plot of semileptonic decays of polarized hyperons, which includes both the three-body and the four-body regions. We calculate radiative corrections to order alpha, neglecting terms of order alpha q/(pi M_1), where q is the four-momentum transfer and M_1 is the mass of the decaying hyperon. Our results exhibit explicitly the correlation between the emitted hyperon three-momentum and the spin of the decaying hyperon. This allows us to obtain the corresponding radiative corrections to the integrated emitted hyperon spin-asymmetry coefficient. Our formulas are valid for charged as well as for neutral decaying hyperons and are appropriate for model-independent experimental analysis whether the real photon is discriminated or not.

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