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Remarks on the Standard Model predictions for R(D) and R(D*)
Kim, C. S.,Lopez-Castro, G.,Tostado, S. L.,Vicente, A. American Physical Society 2017 Physical review. D Vol.95 No.1
<P>Semileptonic b -> c transitions, and in particular the ratios R(D-(*())) = Gamma(B -> D-(*())tau nu)/Gamma(B -> D-(*())l nu), can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for R(D*) is found to be more robust, because possible pollutions from B* contributions turn out to be negligibly small; this indicates that R(D) is a promising observable for searches of new physics.</P>
Evaluation of CKM matrix elements from exclusive Pℓ4 decays
Kim, C. S.,Ló,pez Castro, G.,Tostado, S. L. American Physical Society 2017 Physical Review D Vol.95 No.7
<P>We consider the exclusive P-l4 decays, P -> (P1P2)(V)lv(l), where the subindex V means that the invariant mass of the pseudoscalar pair is taken within a small window around the mass of the vector meson V. Pole contributions beyond the dominant P -> V(P1P2)lv(l) amplitude of P-l4 decays are identified, which, in turn, affect the determination of the CKM matrix elements broken vertical bar V-qq'broken vertical bar. We evaluate the effects of those contributions in the extraction of bottom and charm quark mixings. An application to B -> (pi pi)(rho)lv(l) data from the Belle Collaboration shows an increase in the extracted value of broken vertical bar V-ub broken vertical bar in better agreement with determinations based on B -> pi lv(l) decays. The effect of the rho and D* pole contributions in the determination of broken vertical bar V-cd broken vertical bar from the decay D ->pi pi l(-)($) over bar (l) has also been investigated.</P>
Thermoluminescence of NaCl:Cu Sintered Phosphors Exposed to Beta Irradiation
R. Bernal,C. Cruz-Vázquez,F. Brown,W. Tostado-García,R. Pérez-Salas,V.M. Castaño 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4
NaCl:Cu pellet-shaped phosphors were synthesized through a sintering process. Some samples were exposed to beta irradiation in order to investigate their thermoluminescence properties and capabilities to be used in detecting and measuring ionizing radiation. The glow curves reveal at least four thermoluminescence peaks below 250°C, and a main one above 300°C when a 5°C/s heating rate is used. The lowest temperature peak vanishes in less than 3 min after irradiation, giving rise to an intense afterglow luminescence, potentially useful for in situ non-thermoluminescence dosimetry, and the next remains for about 3 h, but the high temperature one exhibits no important changes after that time. The thermoluminescence intensity increased as the radiation dose increased in the 0.417 - 25.0 Gy dose range. Because the position and the remarkable stability of the higher temperature peak, besides the strong afterglow produced by the fast decaying of the lower temperature peak, it is concluded that these phosphors are very suitable candidates to be used in both thermoluminescence and non thermoluminescence dosimetry of ionizing radiation, having advantages over monocrystals of similar composition. The synthesis route here followed can be reproduced in standard college laboratories, and thermoluminescence be measured in home-made systems, allowing design practices for interdisciplinary physics, chemistry electronics, and materials science students.