arXiv subjects
Publications and source records attributed to E. Truhlik.
The influence of neutrinoless electron to positron conversion on cooling of strongly magnetized iron white dwarfs is studied. It is shown that they can be good candidates for soft gamma-ray repeaters and anomalous X-ray pulsars.
The influence of a neutrinoless electron to positron conversion on a cooling of strongly magnetized iron white dwarfs is studied.
The doublet capture rate of the negative muon capture in deuterium is calculated employing the nuclear wave functions generated from accurate nucleon-nucleon potentials constructed at next-to-next-to-next-to-leading order of heavy-baryon chiral perturbation theory and the weak meson exchange current operator derived within the same formalism. All but one of the low-energy constants that enter the calculation were fixed from pion-nucleon and nucleon-nucleon scattering data. The low-energy constant d^R (c_D), which cannot be determined from the purely two-nucleon data, was extracted recently from the triton beta-decay and the binding energies of the three-nucleon systems. The calculated values of the doublet capture rates show a rather large spread for the used values of the d^R. Precise measurement of the doublet capture rate in the future will not only help to constrain the value of d^R, but also provide a highly nontrivial test of the nuclear chiral EFT framework. Besides, the precise knowledge of the constant d^R will allow for consistent calculations of other two-nucleon weak processes, such as proton-proton fusion and solar neutrino scattering on deuterons, which are important for astrophysics.
We discuss the importance of precise study of muon capture in deuterium for correct understanding of some fundamental astrophysical processes
Model dependence of the capture rates of the negative muon capture in deuterium is studied starting from potential models and the weak two-body meson exchange currents constructed in the tree approximation and also from an effective field theory. The tree one-boson exchange currents are derived from the hard pion chiral Lagrangians of the $N Δπρωa_1$ system. If constructed in conjunction with the one-boson exchange potentials, the capture rates can be calculated consistently. On the other hand, the effective field theory currents, constructed within the heavy baryon chiral perturbation theory, contain a low energy constant $\hat d ^R$ that cannot be extracted from data at the one-particle level nor determined from the first principles. Comparative analysis of the results for the doublet transition rate allows us to extract the constant $\hat d ^R$.
We show that the arguments against our paper raised by B. Davids et al. are either irrelevant or incorrect.
Model dependence of the reaction rates for the weak breakup of deuterons by low energy neutrinos is studied starting from the cross sections derived from potential models and also from pionless effective field theory. Choosing the spread of the reaction yields, caused basically by the different ways the two-body currents are treated, as a measure of the model dependent uncertainty, we conclude that the breakup reactions are $\sim$ 2 - 3 % uncertain, and that even the ratio of the charged to neutral current reaction rates is also $\sim$ 2 % uncertain.
The capture of electrons by the nucleus $^{7}Be$ from the three-body initial state $p+e^{-}+^{7}Be$ in the continuum is studied. On the basis of the expansion of the three-body continuum wave function in the small parameter $ε\approx ({m_e}/{m_p})^{1/2}$ [$m_e$ ($m_p$) is the electron (proton) mass], the role of the protons on the electron capture is considered. The results are compared with the traditional treatment of the electron capture by the nucleus $^{7}Be$. For stars with the density and temperature like in the centre of the Sun the studied mechanism can make non-negligible contribution to the capture rate.
Starting from the axial heavy meson exchange currents, constructed earlier in conjunction with the Bethe--Salpeter equation, we first present the axial $ρ$--, $ω$-- and $a_1$ meson exchange Feynman amplitudes that satisfy the partial conservation of the axial current. Employing these amplitudes, we derive the corresponding weak axial heavy meson exchange currents in the leading order in the 1/M expansion ($M$ is the nucleon mass), suitable for the nuclear physics calculations beyond the threshold energies and with wave functions obtained by solving the Schrödinger equation with one--boson exchange potentials. The constructed currents obey the nuclear form of the partial conservation of the axial current. We apply the space component of these currents in calculations of the cross sections for the disintegration of deuterons by low energy (anti)neutrinos. The deuteron and the final state nucleon--nucleon wave functions are derived (i) from a variant of the OBEPQB potential, and (ii) from the Nijmegen 93 and Nijmegen I nucleon-nucleon interaction. The extracted values of the constant $L_{1, A}$, entering the axial exchange currents of the pionless effective field theory, are in a reasonable agreement with its value predicted by the dimensional analysis.
The structure of the weak axial pion exchange current is discussed in various models. It is shown how the interplay of the chiral invariance and the double counting problem restricts uniquely the form of the pion potential term, in the case when the nuclear dynamics is described by the Schroedinger equation with the static nucleon-nucleon potential.
Starting from chiral Lagrangians, possessing the SU(2)_L x SU(2)_R local chiral symmetry, we derive weak axial one-boson exchange currents in the leading order in the 1/M expansion (M is the nucleon mass). We apply these currents in calculations of the cross sections for the disintegration of the deuterons by the low energy neutrinos. The nuclear wave functions are derived from a variant of the OBEPQB potential and from the Nijmegen 93 and Nijmegen I nucleon-nucleon interactions. The comparison of our cross sections with those obtained within the pionless effective field theory and other potential model calculations shows that the solar neutrino-deuteron cross sections can be calculated within an accuracy of 3.3 %.
The structure of an anomalous Lagrangian of the pi-rho-omega-a_1 system is investigated within the hidden local SU(2)_R x SU(2)_L symmetry approach. The interaction of the external electromagnetic and weak vector and axial-vector fields with the above hadron system is included. The Lagrangian of interest contains the anomalous Wess-Zumino term following from the well known Wess-Zumino-Witten action and six independent homogenous terms. It is characterized by four constants that are to be determined from a fit to the data on various elementary reactions. Present data allows one to extract the constants with a good accuracy. The homogenous part of the Lagrangian has been applied in the study of anomalous processes that could enhance the high energy tail of the spectrum of photons, produced in the radiative muon capture in hydrogen. It should be noted that recently, an intensive search for such enhancement processes has been carried in the literature, in an attempt to resolve the so called "g_P puzzle": an about 50 % difference between the theoretical prediction of the value of the induced pseudoscalar constant g_P and its value extracted from the high energy tail of the photon spectrum, measured in the precision TRIUMF experiment. Here, more details on the studied material are presented and new results, obtained by using the Wess-Zumino term, are provided.
Using the difference between the gauge symmetric and standard pi-N-delta couplings, a contact pi-pi-N-N term, quadratic in the pi-N-delta coupling, is explicitly constructed. Besides, a contribution from the delta excitation mechanism to the photon spectrum for the radiative muon capture in hydrogen is derived from the gauge symmetric pi-N-delta and gamma-N-delta couplings. It is shown for the photon spectrum, studied recently experimentally, that the new spectrum is for the photon momentums k > 60 MeV by 4-10 % smaller than the one obtained from standardly used couplings with the on-shell deltas.
We analyze photon spectra in the radiative muon capture in hydrogen using amplitudes derived from chiral Lagrangians. The model can describe the high energy part of the photon spectra, measured recently at TRIUMF, reasonably well.
We discuss an anomalous Lagrangian of the pi-rho-omega-a_1 system in the presence of external electroweak fields which is suitable for constructing the amplitude for the radiative muon capture by proton.
We analyze amplitudes for the pion electroproduction on proton derived from Lagrangians based on the local chiral SU(2) x SU(2) symmetries. We show that such amplitudes do contain information on the nucleon axial form factor F_A in both soft and hard pion regimes. This result invalidates recent Haberzettl's claim that the pion electroproduction at threshold cannot be used to extract any information regarding F_A.
Comparison of the new data for the negative muon capture in 28^Si with the recent shell model calculations using a full 1s-0d model space and the USD empirical effective interaction and the one-nucleon weak current provides the induced pseudoscalar g_P substantially smaller than the value predicted by PCAC and pion-pole dominance. We find that adding the effect from the one-pion exchange axial charge density and using the same scheme of calculations does not change situation to the value of g_P.
Using modern data, we first refit constants needed to complete an anomalous pi-rho-omega-a_1 Lagrangian obtained within the approach of hidden local symmetries. Then we derive from this Lagrangian electromagnetic isoscalar rho-pi-gamma and rho-a_1-gamma currents needed in calculations of the deuteron electromagnetic form factors at large momentum transfers.