Quantum mechanics of baryogenesis

The cosmological baryon asymmetry can be explained as remnant of heavy Majorana neutrino decays in the early universe. We study this out-of-equilibrium process by means of Kadanoff-Baym equations which are solved in a perturbative expansion. To leading order the problem is reduced to solving a set of Boltzmann equations for distribution functions.Comment: 12 pages, 2 figures, typos corrected. To be published in Physics Letter

Anarchy and Leptogenesis

We study if leptogenesis works successfully together with the neutrino mass anarchy hypothesis. We find that the predicted neutrino mass spectrum is sensitive to the reheating temperature or the inflaton mass, while the distributions of the neutrino mixing angles and CP violation phases remain intact as determined by the invariant Haar measure of U(3). In the case of thermal leptogenesis, the light neutrino mass distribution agrees well with the observations if the reheating temperature is O(10^{9-11}) GeV. The mass spectrum of the right-handed neutrinos and the neutrino Yukawa matrix exhibit a certain pattern, as a result of the competition between random matrices with elements of order unity and the wash-out effect. Non-thermal leptogenesis is consistent with observation only if the inflaton mass is larger than or comparable to the typical right-handed neutrino mass scale. Cosmological implications are discussed in connection with the 125GeV Higgs boson mass.Comment: 29 pages, 6 figures. v2: figures and references added. v3: published in JHE

Leptogenesis in the type III seesaw mechanism

It is shown that the type III seesaw mechanism proposed recently can have certain advantages over the conventional (or type I) seesaw mechanism for leptogenesis. In particular a resonant enhancement of leptogenesis via heavy quasi-Dirac right-handed neutrino pairs can occur without a special flavor form or "texture" of the mass matrices being assumed. Some of the requirements for neutrino mixing and leptogenesis are effectively decoupled.Comment: 12 pages including one figure, several references adde

A New Tool for the Lamb Shift Calculation

We solve the Bethe-Salpeter equation for hydrogenic bound states by choosing an appropriate interaction kernel $K_c$. We want to use our solution to calculate up to a higher order the hydrogen Lamb-shift, and as a first application we present up to order \left(\aa / \pi\right)(\za)^7 the contribution of the lowest order self-energy graph, calculated {\it exactly}. The basic formalism is a natural extension to the hydrogenic bound states of the one previously presented by R. Barbieri and E. Remiddi and used in the case of positronium.Comment: 21 pages, Latex, Preprint DFUB-94-0

The Singlet Majoron Model with Hidden Scale Invariance

We investigate an extension of the Singlet Majoron Model in which the breaking of dilatation symmetry by the mass parameters of the scalar potential is removed by means of a dilaton field. Starting from the one-loop renormalization group improved potential, we discuss the ground state of the theory. The flat direction in the classical potential is lifted by quantum corrections and the true vacua are found. Studying the finite temperature potential, we analyze the cosmological consequences of a Jordan-Brans-Dicke dilaton and show that the lepton number is spontaneously broken after the electroweak phase transition, thus avoiding any constraint coming from the requirement of the preservation of the baryon asymmetry in the early Universe. We also find that, contrary to the Standard Model case, the dilaton cosmology does not impose any upper bound on the scale of the spontaneous breaking of scale invariance.Comment: 22 pages, SISSA-5/93/A and DFPD/93/TH/0

The Neutrino Magnetic Moment Induced by Leptoquarks

Allowing leptoquarks to interact with both right-handed and left-handed neutrinos (i.e., ``non-chiral'' leptoquarks), we show that a non-zero neutrino magnetic moment can arise naturally. Although the mass of the non-chiral vector leptoquark that couples to the first generation fermions is constrained severely by universality of the $\pi^+$ leptonic decays and is found to be greater than 50 TeV, the masses of the second and third generation non-chiral vector leptoquarks may evade such constraint and may in general be in the range of $1\sim 100$ TeV. With reasonable input mass and coupling values, we find that the neutrino magnetic moment due to the second generation leptoquarks is of the order of $10^{-12}\sim 10^{-16} \mu_{\rm B}$ while that caused by the third generation leptoquarks, being enhanced significantly by the large top quark mass, is in the range of $10^{-10}\sim 10^{-14} \mu_{\rm B}$.Comment: 11 pages, 3 eps figures, uses revte

Lepton Flavor Violation and Cosmological Constraints on R-parity Violation

In supersymmetric standard models R-parity violating couplings are severely constrained, since otherwise they would erase the existing baryon asymmetry before the electroweak transition. It is often claimed that this cosmological constraint can be circumvented if the baryon number and one of the lepton flavor numbers are sufficiently conserved in these R-parity violating couplings, because B/3-L_i for each lepton flavor is separately conserved by the sphaleron process. We discuss the effect of lepton flavor violation on the B-L conservation, and show that even tiny slepton mixing angles \theta_{12} \gsim {\cal O}(10^{-4}) and \theta_{23}, \theta_{13}\gsim {\cal O}(10^{-5}) will spoil the separate B/3-L_i conservation. In particular, if lepton flavor violations are observed in experiments such as MEG and B-factories, it will imply that all the R-parity violating couplings must be suppressed to avoid the B-L erasure. We also discuss the implication for the decay of the lightest MSSM particle at the LHC.Comment: 21 pages, 7 figures. v2: minor change

B-physics constraints on baryon number violating couplings: grand unification or R-parity violation

We investigate the role that baryon number violating interactions may play in $B$ phenomenology. Present in various grand unified theories, supersymmetric theories with R-parity violation and composite models, a diquark state could be quite light. Using the data on B decays as well as $B - {\bar B}$ mixing, we find strong constraints on the couplings that such a light diquark state may have with the Standard Model quarks.Comment: 19 pages, latex, no figures, 13 tables include

Spectroscopy of doubly charmed baryons: Ξcc+\Xi_{cc}^{+} and Ξcc++\Xi_{cc}^{++}

Using the quark-diquark approximation in the framework of Buchm\" uller-Tye potential model, we investigate the spectroscopy of doubly charmed baryons: $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$. Our results include the masses, parameters of radial wave functions of states with the different excitations of both diquark and light quark-diquark system. We calculate the values of fine and hyperfine splittings of these levels and discuss some new features, connected to the identity of heavy quarks, in the dynamics of hadronic and radiative transitions between the states of these baryons.Comment: 10 pages, Latex file, 1 fig, corrected some typo

Confinement, Crossing Symmetry, and Glueballs

We suggest that the quark-confining force is related by crossing symmetry to a color-singlet glueball ${\cal G}$ which is well described as a loop of one quantum of color magnetic flux. Electron pair annihilation as high as $\approx 2 GeV$ above the $\Upsilon$ mass could produce $\Upsilon \rightarrow \ell^+\ell^-$ accompanied by ${\cal G}$ or one of its excited states.Comment: LaTeX, 12 pages, no figures, Los Alamos preprint LA-UR-94-263