0000000000994480
AUTHOR
Thomas Gutsche
showing 19 related works from this author
Physical observables in the decay Λb→Λc(→Λ+π)+τ−+ν̄τ
2015
We analyze the tauonic semileptonic baryon decays [Formula: see text] with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization components of the [Formula: see text] and the [Formula: see text], and the lepton-side forward-backward asymmetries. We use the covariant confined quark model to provide numerical results on these observables.
Semileptonic decaysΛc+→Λℓ+νℓ(ℓ=e,μ)in the covariant quark model and comparison with the new absolute branching fraction measurements of Belle and BES…
2016
We present precise theoretical predictions for the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}(\ensuremath{\ell}=e,\ensuremath{\mu})$ decays in the covariant confined quark model. This study is motivated by two recent and accurate measurements of the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{e}^{+}{\ensuremath{\nu}}_{e}$ by the Belle Collaboration at the KE…
Ab initio three-loop calculation of the W -exchange contribution to nonleptonic decays of double charm baryons
2019
We have made an ab initio three-loop quark model calculation of the $W$-exchange contribution to the nonleptonic two-body decays of the doubly charmed baryons $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. The $W$-exchange contributions appear in addition to the factorizable tree graph contributions and are not suppressed in general. We make use of the covariant confined quark model previously developed by us to calculate the tree graph as well as the $W$-exchange contribution. We calculate helicity amplitudes and quantitatively compare the tree graph and $W$-exchange contributions. Finally, we compare the calculated decay widths with those from other theoretical approaches when they are available.
Relativistic constituent quark model with infrared confinement
2009
We refine the relativistic constituent quark model developed in our previous papers to include the confinement of quarks. It is done, first, by introducing the scale integration in the space of alpha-parameters, and, second, by cutting this scale integration on the upper limit which corresponds to an infrared cutoff. In this manner one removes all possible thresholds presented in the initial quark diagram. The cutoff parameter is taken to be the same for all physical processes. We adjust other model parameters by fitting the calculated quantities of the basic physical processes to available experimental data. As an application, we calculate the electromagnetic form factors of the pion and t…
Decay chain information on the newly discovered double charm baryon state $\Xi_{cc}^{++}$
2017
We interprete the new double charm baryon state found by the LHCb Collaboration in the invariant mass distribution of the set of final state particles $(\Lambda_c^+\,K^-\,\pi^+\,\pi^+)$ as being at the origin of the decay chain $\Xi_{cc}^{++} \to \Sigma_c^{++} (\to \Lambda_c^+ \pi^+) +\bar K^{*0} (\to K^- \pi^+)$. The nonleptonic decay $\Xi_{cc}^{++} \to \Sigma_c^{++} + \bar K^{*0}$ belongs to a class of decays where the quark flavor composition is such that the decay proceeds solely via the factorizing contribution precluding a contamination from internal $W$-exchange. We use the covariant confined quark model previously developed by us to calculate the four helicity amplitudes that descri…
Heavy-to-light semileptonic decays ofΛbandΛcbaryons in the covariant confined quark model
2014
We present a detailed analysis of the heavy-to-light semileptonic decays of theb andc baryons �b → pl ¯ νl andc → nl + νl in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters.
Analysis of the semileptonic and nonleptonic two-body decays of the double heavy charm baryon states Ξcc++,Ξcc+ and Ωcc+
2019
We calculate the semileptonic and a subclass of sixteen nonleptonic two-body decays of the double charm baryon ground states Ξcc++,Ξcc+ and Ωcc+ where we concentrate on the nonleptonic decay modes. We identify those nonleptonic decay channels in which the decay proceeds solely via the factorizing contribution precluding a contamination from W exchange. We use the covariant confined quark model previously developed by us to calculate the various helicity amplitudes which describe the dynamics of the 1/2+→1/2+ and 1/2+→3/2+ transitions induced by the Cabibbo-favored effective (c→s) and (d→u) currents. We then proceed to calculate the rates of the decays as well as polarization effects and ang…
Rare baryon decaysΛb→Λℓ+ℓ−(ℓ=e,μ,τ) andΛb→Λγ: Differential and total rates, lepton- and hadron-side forward-backward asymmetries
2013
Using the covariant constituent quark model previously developed by us, we calculate the differential rate and the forward-backward asymmetries on the lepton and hadron side for the rare baryon decays ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$) and ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma}$. We use helicity methods to write down a threefold joint angular decay distribution for the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\…
Zb(10610) and Zb′(10650) decays in a covariant quark model
2017
We present a calculation of the strong decays of the exotic states ${Z}_{b}(10610)$ and ${Z}_{b}^{\ensuremath{'}}(10650)$ using a covariant quark model. We use a molecular-type four-quark current for the coupling of the ${Z}_{b}(10610)$ and ${Z}_{b}^{\ensuremath{'}}(10650)$ to the constituent heavy and light quarks.
Radiative decays of double heavy baryons in a relativistic constituent three-quark model including hyperfine mixing
2010
We study flavor-conserving radiative decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit. We discuss in some detail hyperfine mixing effects.
Analyzing lepton flavor universality in the decays Λb→Λc(*)(12±,32−)+ℓν¯ℓ
2018
Lepton flavor universality can be tested in the semileptonic decays Λb→Λc(*), where Λc(*) denotes either the ground state Λc(2286) (with JP=1/2+) or its orbital excitations Λc(2595) (with JP=1/2−) and Λc(2625) (with JP=3/2−). We calculate the differential decay rates as well as the branching fractions of these decays for both tauonic and muonic modes with form factors obtained from a covariant confined quark model previously developed by us. We present results for the rate ratios of the tauonic and muonic modes which provide important tests of lepton flavor universality in forthcoming experiments.
Polarization effects in the cascade decayΛb→Λ(→pπ−)+J/ψ(→ℓ+ℓ−)in the covariant confined quark model
2013
We calculate the invariant and helicity amplitudes for the nonleptonic decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)$ in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)(\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}})$ and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from th…
Theoretical description of the decays Λb→Λ(*)(12±,32±)+J/ψ
2017
We calculate the invariant and helicity amplitudes for the transitions ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})+J/\ensuremath{\psi}$, where the ${\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})$ are $\mathrm{\ensuremath{\Lambda}}(sud)$-type ground and excited states with ${J}^{P}$ quantum numbers ${J}^{P}={\frac{1}{2}}^{\ifmmode\pm\else\textpm\fi{}}$, ${\frac{3}{2}}^{\ifmmode\pm\else\textpm\fi{}}$. The calculations are performed in the framework of a covariant confined quark model previously developed by us. We find that the values of the helicity amplitudes for the ${\mathrm{\ensuremath{\Lambda}}}^{*}(1520,{\frac{3}{2}}^{\ensu…
Semileptonic decays of the lightJP=1/2+ground state baryon octet
2008
We calculate the semileptonic baryon octet-octet transition form factors using a manifestly Lorentz covariant quark model approach based on the factorization of the contribution of valence quarks and chiral effects. We perform a detailed analysis of SU(3)-breaking corrections to the hyperon semileptonic decay form factors. We present complete results on decay rates and asymmetry parameters including lepton mass effects for the rates.
Light baryons and their electromagnetic interactions in the covariant constituent quark model
2012
We extend the confined covariant constituent quark model that was previously developed by us for mesons to the baryon sector. In our numerical calculation we use the same values for the constituent quark masses and the infrared cutoff as have been previously used in the meson sector. In a first application we describe the static properties of the proton and neutron, and the $\Lambda$-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers. We discuss in some detail the conservation of gauge invariance of the electromagnetic transition matrix elements in the presence of a nonlocal coupling of the baryons to the three constituent quar…
Semileptonic decays of double heavy baryons in a relativistic constituent three-quark model
2009
We study the semileptonic decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. We present complete results on transition form factors between double-heavy baryons for finite values of the heavy quark/baryon masses and in the heavy quark symmetry limit which is valid at and close to zero recoil. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit.
Hyperon forward spin polarizability gamma0 in baryon chiral perturbation theory
2015
We present the calculation of the hyperon forward spin polarizability gamma0 using manifestly Lorentz covariant baryon chiral perturbation theory including the intermediate contribution of the spin 3/2 states. As at the considered order the extraction of gamma0 is a pure prediction of chiral perturbation theory, the obtained values are a good test for this theory. After including explicitly the decuplet states, our SU(2) results have a very good agreement with the experimental data and we extend our framework to SU(3) to give predictions to the hyperons' gamma0 values. Prominent are the Sigma^- and Xi^- baryons as their photon transition to the decuplet is forbidden in SU(3) symmetry and th…
Bounds on rare decays of η and η′ mesons from the neutron EDM
2019
We provide model-independent bounds on the rates of rare decays $\ensuremath{\eta}({\ensuremath{\eta}}^{\ensuremath{'}})\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ based on experimental limits on the neutron electric dipole moment (nEDM). Starting from phenomenological $\ensuremath{\eta}({\ensuremath{\eta}}^{\ensuremath{'}})\ensuremath{\pi}\ensuremath{\pi}$ couplings, the nEDM arises at the two-loop level. The leading-order relativistic chiral perturbation theory calculation with the minimal photon coupling to charged pions and a proton inside the loops leads to a finite, counterterm-free result. This is an improvement upon previous estimates which used approximations in evalu…
Covariant ChPT calculation of the hyperon forward spin polarizability
2015
We predict the values for baryon forward spin polarizabilities in fully covariant ChPT and including the virtual contributions of the spin-3/2 states. As the nucleon results are in good agreement with the experimental data and they do not depend on renormalization schemes, we extend the calculations to the hyperon sector.