Leptonic CP violating effective action for Dirac and Majorana neutrinos

In the Standard Model minimally extended to include massive neutrinos, we compute the leading CP-violating zero temperature contributions to the one-loop effective action induced by integration of the leptons. Such contributions start at operators of dimension six and they are P even for Dirac neutrinos and P even or odd for Majorana neutrinos. Dimension four operators are allowed in the mixed Dirac-Majorana case. It is verified by explicit calculation that CP can be violated in two generation settings for Majorana neutrinos. Using different neutrino scenarios we give upper bounds for the couplings of the CP-violating operators. As a rule, we find that lepton-induced couplings are suppressed as compared to quark-induced couplings, whenever the latter are allowed, nevertheless, through virtual lepton-number violating mechanisms, Majorana neutrinos induce new CP-violating operators not present in the quark or Dirac-neutrino cases.Comment: 47 pages, 4 figure

Nonminimal non-Abelian quantum vector fields in curved spacetime

ACKNOWLEDGMENTS I thank C. Garcia-Recio for suggestions on the manuscript and A. O. Barvinsky for critical remarks. This work has been partially supported by MCIN/AEI/10.13039/ 501100011033 under Grant No. PID2020–114767GBI00, by the Junta de Andalucía (Grant No. FQM-225), by the FEDER/Junta de Andalucía-Consejería de Economía y Conocimiento 2014-2020 Operational Program under Grant No. A-FQM-178-UGR18, and by the Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía and European Regional Development Fund (ERDF), Ref. SOMM17/6105/UGR.The quantum effective action of nonminimal vector fields with Abelian or non-Abelian gauge degrees of freedom in curved spacetime is studied. The Proca or Yang-Mills fields are coupled to a local masslike term acting in both coordinate and gauge spaces. Pathologies due to gauge invariance in the ultraviolet are avoided through the introduction of a non-Abelian version of the Stueckelberg field. It is found that the breaking of gauge invariance induced by the mass term affects only the tree-level part of the effective action. The ultraviolet divergent part of the effective action to one loop is obtained using the method of covariant symbols and dimensional regularization. Formulas are given valid for any spacetime dimension and explicit results are shown for the two-dimensional case. As already happened for a single vector field, the ultraviolet divergences are local but not of polynomial type.MCIN/AEI/10.13039/ 501100011033 under Grant No. PID2020–114767GBI00Junta de Andalucía (Grant No. FQM-225)FEDER/Junta de Andalucía-Consejería de Economía y Conocimiento 2014-2020 Operational Program under Grant No. A-FQM-178-UGR18Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía and European Regional Development Fund (ERDF), Ref. SOMM17/6105/UG

Renormalization of vector fields with mass-like coupling in curved spacetime

Using the method of covariant symbols we compute the divergent part of the effective action of the Proca field with non-minimal mass term. Specifically a quantum abelian vector field with a non-derivative coupling to an external tensor field in curved spacetime in four dimensions is considered. Relatively explicit expressions are obtained which are manifestly local but non polynomial in the external fields. Our result is shown to reproduce existing ones in all particular cases considered. Internal consistency with Weyl invariance is also verified.This work has been partially supported by the Spanish MINECO (Grant no. FIS2017-85053-C2-1-P) and by the Junta de Andalucía (Grant no. FQM-225). This study has been partially financed by the Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucía and European Regional Development Fund (ERDF), ref. SOMM17/6105/UGR

SU(6) extension of the Weinberg-Tomozawa meson-baryon Lagrangian

A consistent SU(6) extension of the Weinberg-Tomozawa meson-baryon chiral Lagrangian is constructed which incorporates vector meson and baryon decuplet degrees of freedom. The corresponding Bethe-Salpeter approximation predicts the existence of an isoscalar spin-parity 3/2 K(*)N bound state (strangeness +1) with a mass around 1.7-1.8 GeV. It is the highest hypercharge state of an antidecuplet SU(3) representation and it is unstable through K(*) decay. The estimated width of this state (neglecting d-wave KN decay) turns out to be small (Gamma (K) over bar (0)pK(+)pi(-) by looking at the three body pK(+)pi(-) invariant mass

Short range correlations in the pion s-wave self-energy of pionic atoms

We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave πN amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected rescattering term, second order absorptive effects, terms from the interaction of pions with the virtual pion cloud (chiral corrections) and correlation effects. Different off-shell extrapolations for the πN amplitude are used and it is found that, although some individual terms are sensitive to the extrapolation, the sum of them is rather insensitive. The results are compared with empirical values from best fits to the data and are found to be compatible, within theoretical and empirical uncertainties. The results do not rule out further contributions but they put stringent constraints on their strength

Baryonic susceptibilities, quark-diquark models, and quark-hadron duality at finite temperature

Fluctuations of conserved charges such as baryon number, electric charge, and strangeness may provide a test for completeness of states in lattice QCD for three light flavors. We elaborate on the idea that the corresponding susceptibilities can be saturated with excited baryonic states with an underlying quark-diquark structure with a linearly confining interaction. Using Polyakov-loop correlators, we show that in the static limit, the quark-diquark potential coincides with the quark-antiquark potential in marked agreement with recent lattice studies. We thus study in a quark-diquark model the baryonic fluctuations of electric charge, baryon number, and strangeness—χBQ, χBB, and χBS—by considering a realization of the hadron resonance gas model in the light flavor sector of QCD. These results are obtained by using the baryon spectrum computed within a relativistic quark-diquark model, leading to an overall good agreement with the spectrum obtained with other quark models and with lattice data for the fluctuations.This work is supported by the Spanish MINECO and European FEDER funds (Grants No. FIS2014-59386-P and No. FIS2017-85053-C2-1-P), Junta de Andalucía (Grant No. FQM-225), and by the Consejería de Conocimiento, Investigación y Universidad of the Junta de Andalucía and European Regional Development Fund (ERDF) Grant No. SOMM17/6105/UGR. The research of E. M. is also supported by the Ramón y Cajal Program of the Spanish MINECO (Grant No. RYC-2016-20678)