arXiv subjects

Emmanuel A. Paschos

Publications and source records attributed to Emmanuel A. Paschos.

15 recordsLinked to original sources

arXiv2016

Short Wavelength Oscillations with Right-Handed Neutrinos

The standard model is extended with three right-handed, singlet neutrinos with general couplings permitted by the $SU(2)_{L}\times U(1)$ symmetry. The traditional oscillations are accounted for, as usually, by three left-handed neutrinos. The article investigates new structures that develop when the masses of the right-handed states are in the eV range. The new states interfere and oscillate with the standard light neutrinos. New structures appear when the detectors average over short wavelengths. I use these results to present and classify properties of the observed anomalies in the MiniBooNe, reactor and Gallium-detector experiments.

hep-ph↗

arXiv2006

Resonance production by neutrinos: The second resonance region

The article contains new results for spin-3/2 and -1/2 resonances. It specializes to the second resonance region, which includes the $P_{11}(1440)$, $D_{13}(1520)$ and $S_{11}(1535)$ resonances. New data on electroproduction enable us to determine the vector form factors accurately. Estimates for the axial couplings are obtained from decay rates of the resonances with the help of the partially conserved axial current (PCAC) hypothesis. We present cross sections to be compared with the running and future experiments. The article is self--contained and allows the reader to write simple programs for reproducing the cross sections and for obtaining additional differential cross sections.

hep-ph↗

arXiv2005

S_3 Flavor Symmetry and Leptogenesis

We consider leptogenesis in a minimal S_3 extension of the standard model with an additional Z_2 symmetry in the leptonic sector. It is found that the CP phase appearing in the neutrino mixing is the same as that for the CP asymmetries responsible for leptogenesis. Because of the discrete S_3 x Z_2 flavor symmetries, the CP asymmetries are strongly suppressed. We therefore assume that the resonant enhancement of the CP asymmetries takes place to obtain a realistic size of baryon number asymmetry in theuniverse. Three degenerate right-handed neutrino masses of O(10) TeV are theoretically expected in this model.

hep-ph↗

arXiv2005

Resonance production by neutrinos: I. J=3/2 Resonances

The article contains general formulas for the production of J=3/2 resonances by neutrinos and antineutrinos. It specializes to the P_{33}(1232) resonance whose form factors are determined by theory and experiment and then are compared with experimental results at low and high energies. It is shown that the minimum in the low Q^2 region is a consequence of a combined effect from the vanishing of the vector form factors, the muon mass and Pauli blocking. Several improvements for the future investigations are suggested.

hep-ph↗

arXiv2004

Vector Meson Contributions in epsilon'/epsilon

The CP violating parameter epsilon'/epsilon is computed using the low-energy dynamics of a chiral theory supplemented by vector resonances. The divergent contributions coming from strong pi-pi scattering are tamed by vector-meson exchange terms. This amounts to softening the fast growing high-energy behaviour of pi-pi scattering. The final result for epsilon'/epsilon shows a smooth dependence on the cut-off where low energy dynamics is matched with that of QCD.

hep-ph↗

arXiv2003

Neutrino Production of Resonances

We take a fresh look at the analysis of resonance production by neutrinos. We consider three resonances $P_{33}, P_{11}$ and $S_{11}$ with a detailed discussion of their form factors. The article presents results for free proton and neutron targets and discusses the corrections which appear on nuclear targets. The Pauli suppression factor is derived in the Fermi gas model and shown to apply to resonance production. The importance of the various resonances is demonstrated with numerical calculations. The $Δ$-resonance is described by two formfactors and its differential cross sections are compared with experimental data. The article is self-contained and could be helpful to readers who wish to reproduce and use these cross sections.

hep-ph↗

arXiv2002

Antineutrino-neutrino and antineutrino-electron resonant annihilation through rho and other vector mesons

The \bar{nu}e^- --> pi^- pi^0 and nu e^+ --> pi^+ pi^0 reaction have a resonant structure whenever the energy of the s--channel equals the mass of a J^P=1^- vector meson. The resonant cross sections are of the order 10^{-38} cm^2 and correspond to cosmic ray antineutrino energies in the range 0.2 to 2 TeV. A similar structure occurs in the annihilation of cosmic ray antineutrinos with a relic (background) neutrino. For m_{nu} <= 10^{-3} eV the resonant energy is above GZK limit and their decay products include multiple gamma--rays. Possible detection schemes are discussed, especially those which rely on Cherenkov radiation.

hep-ph↗

arXiv1999

Constraining Leptogenesis from Laboratory Experiments

The presently available information on neutrino oscillations can be used to tightly constrain the light neutrino mass matrix $m_\n$ under the assumption that the three known neutrinos provide explanation of the solar and atmospheric anomalies. We exploit left right symmetry and the seesaw model to establish direct correlation between this constrained $m_\n$ and the mass matrix $M_R$ for the right handed (RH) neutrinos. Using this correlation, one could directly relate the lepton asymmetry $\e$ generated in the decay of the lightest RH neutrino to experimentally determined mixing angles of the light neutrinos. It is found that the parameters required to understand neutrino anomalies also give rise to the $\e$ in the range required to reproduce the correct baryon asymmetry in the leptogenesis scenario. Specifically, the small angle MSW or the the vacuum oscillation explanation of the solar anomaly can lead to correct $\e$ for maximal value of the CP violating phases. In contrast, the large angle MSW solution needs some suppression in CP violating phases in order to generate the right $\e$.

hep-ph↗

arXiv1998

Further Considerations on the CP Asymmetry in Heavy Majorana Neutrino Decays

We work out the thermodynamic equations for the decays and scatterings of heavy Majorana neutrinos including the constraints from unitarity. The Boltzmann equations depend on the CP asymmetry parameter which contains both, a self-energy and a vertex correction. At thermal equilibrium there is no net lepton asymmetry due to the CPT theorem and the unitarity constraint. We show explicitly that deviations from thermal equilibrium create the lepton asymmetry.

hep-ph↗

arXiv1997

Momentum Distribution in the Decay B-->J/psi+X

We combine the NRQCD formalism for the inclusive color singlet and octet production of charmonium states with the parton and the ACCMM model, respectively, and calculate the momentum distribution in the decay B-->J/psi+X. Neglecting the kinematics of soft gluon radiation, we find that the motion of the b quark in the bound state can account, to a large extent, for the observed spectrum. The parton model gives a satisfactory presentation of the data, provided that the heavy quark momentum distribution is taken to be soft. To be explicit, we obtain epsilon_p=O(0.008-0.012) for the parameter of the Peterson et al. distribution function. The ACCMM model can account for the data more accurately. The preferred Fermi momentum p_F=O(0.57 GeV) is in good agreement with recent studies of the heavy quark's kinetic energy.

hep-ph↗

arXiv1997

Radiatively Corrected Semileptonic Spectra in B Meson Decays

We show how radiative QCD corrections calculated in terms of quarks can be incorporated at the hadron level in inclusive semileptonic B-meson decays. The bound state effects are described by a momentum distribution function of the $b$ quark. The summation over the final states and the averaging over the momentum distribution of the decaying quark render the radiative corrections finite. With this coherent formalism we investigate the shape of the electron spectra for $b\to u$ and $b\to c$ decays as a function of the parameters of the theory. The resultant $b\to c$ electron energy spectrum is in agreement with the experimental data.

hep-ph↗

arXiv1996

Baryogenesis Through Mixing of Heavy Majorana Neutrinos

A mechanism is presented, in which the mixing of right handed heavy Majorana neutrinos creates a $CP-$asymmetric universe. When these Majorana neutrinos subsequently decay more leptons than anti-leptons are produced. The lepton asymmetry created by this new mechanism can exceed by a few orders of magnitude any lepton asymmetry originating from direct decays. The asymmetry is finally converted into a baryon asymmetry during the electroweak phase transition.

hep-ph↗

arXiv1995

Baryon and Lepton Number Assignment in $E_6$ Models

In $E_6$ models there are new particles whose baryon number is not uniquely assigned. We point out that the baryon and lepton number assignment to these particles can change the baryogenesis scenario significantly. We consider left-right symmetric extension of the standard model in which $(B-L)$ quantum number is gauged. The identification of $(B-L)$ with a generator of $E_6$ is used to define the baryon and lepton numbers for the exotic particles in a way that the electroweak baryon and lepton number anomaly corresponding to the $SU(2)_L$ group vanishes, {\it i.e.}, there is no non-perturbative baryon or lepton number violation during the electroweak phase transition. We study some consequences of the new assignment.

hep-ph↗

arXiv1994

Baryogenesis from a Lepton Asymmetric Universe

We demonstrate that $CP-$violation in the Majorana mass matrices of the heavy neutrinos can generate a $CP-$asymmetric universe. The subsequent decay of the Majorana particles generates a lepton number asymmetry. During the electroweak phase transition the lepton asymmetry is converted into a baryon asymmetry, which survives down to this time.

hep-ph↗

arXiv1994

CP violation in the time evolution of the decay K0 -> Pi0 e+ e-

We examine the possibility of extracting CP-violating terms in the decay K0 -> Pi0 e+ e- by studying the time evolution of a K0 beam. We focus on the interference region and search for clear effects. We find that experiments which average over the electron and positron momenta can detect CP violation as an oscillation in the decay rate. The branching ratio is ( 3 - 5 ) * 10^(-12) and direct CP violation dominates over a wide range of the parameters.

hep-ph↗