e±e^\pm Excesses in the Cosmic Ray Spectrum and Possible Interpretations

The data collected by ATIC, PPB-BETS, FERMI-LAT and HESS all indicate that there is an electron/positron excess in the cosmic ray energy spectrum above $\sim$ 100 GeV, although different instrumental teams do not agree on the detailed spectral shape. PAMELA also reported a clear excess feature of the positron fraction above several GeV, but no excess in anti-protons. Here we review the observational status and theoretical models of this interesting observational feature. We pay special attention to various physical interpretations proposed in the literature, including modified supernova remnant models for the $e^\pm$ background, new astrophysical sources, and new physics (the dark matter models). We suggest that although most models can make a case to interpret the data, with the current observational constraints the dark matter interpretations, especially those invoking annihilation, require much more exotic assumptions than some astrophysical interpretations. Future observations may present some ``smoking-gun'' observational tests to differentiate among different models and to identify the correct interpretation to the phenomenon.Comment: 48 pages, including 10 figures and 1 tabel. Invited review to be published in IJMP

Dark matter from SU(4) model

The left-right symmetric Pati-Salam model of the unification of quarks and leptons is based on SU(4) and SU(2)xSU(2) groups. These groups are naturally extended to include the classification of families of quarks and leptons. We assume that the family group (the group which unites the families) is also the SU(4) group. The properties of the 4-th generation of fermions are the same as that of the ordinary-matter fermions in first three generations except for the family charge of the SU(4)_F group: F=(1/3,1/3,1/3,-1), where F=1/3 for fermions of ordinary matter and F=-1 for the 4-th generation. The difference in F does not allow the mixing between ordinary and fourth-generation fermions. Because of the conservation of the F charge, the creation of baryons and leptons in the process of electroweak baryogenesis must be accompanied by the creation of fermions of the 4-th generation. As a result the excess n_B of baryons over antibaryons leads to the excess n_{\nu 4}=N-\bar N=n_B of neutrinos over antineutrinos in the 4-th generation. This massive fourth-generation neutrino may form the non-baryonic dark matter. In principle their mass density n_{\nu 4}m_N in the Universe can give the main contribution to the dark matter, since the lower bound on neutrino mass m_N from the data on decay of the Z-bosons is m_N > m_Z/2. The straightforward prediction of this model leads to the amount of cold dark matter relative to baryons, which is an order of magnitude bigger than allowed by observations. This inconsistency may be avoided by non-conservation of the F-charge.Comment: 9 pages, 2 figures, version accepted in JETP Letters, corrected after referee reports, references are adde

Constraints on dark matter particles from theory, galaxy observations and N-body simulations

Mass bounds on dark matter (DM) candidates are obtained for particles decoupling in or out of equilibrium with {\bf arbitrary} isotropic and homogeneous distribution functions. A coarse grained Liouville invariant primordial phase space density $\mathcal D$ is introduced. Combining its value with recent photometric and kinematic data on dwarf spheroidal satellite galaxies in the Milky Way (dShps), the DM density today and $N$-body simulations, yields upper and lower bounds on the mass, primordial phase space densities and velocity dispersion of the DM candidates. The mass of the DM particles is bound in the few keV range. If chemical freeze out occurs before thermal decoupling, light bosonic particles can Bose-condense. Such Bose-Einstein {\it condensate} is studied as a dark matter candidate. Depending on the relation between the critical($T_c$)and decoupling($T_d$)temperatures, a BEC light relic could act as CDM but the decoupling scale must be {\it higher} than the electroweak scale. The condensate tightens the upper bound on the particle's mass. Non-equilibrium scenarios that describe particle production and partial thermalization, sterile neutrinos produced out of equilibrium and other DM models are analyzed in detail obtaining bounds on their mass, primordial phase space density and velocity dispersion. Light thermal relics with $m \sim \mathrm{few} \mathrm{keV}$ and sterile neutrinos lead to a primordial phase space density compatible with {\bf cored} dShps and disfavor cusped satellites. Light Bose condensed DM candidates yield phase space densities consistent with {\bf cores} and if $T_c\gg T_d$ also with cusps. Phase space density bounds from N-body simulations suggest a potential tension for WIMPS with $m \sim 100 \mathrm{GeV},T_d \sim 10 \mathrm{MeV}$.Comment: 27 pages 8 figures. Version to appear in Phys. Rev.

Binary systems of neutral mesons in Quantum Field Theory

Quasi-degenerate binary systems of neutral mesons of the kaon type are investigated in Quantum Field Theory (QFT). General constraints cast by analyticity and discrete symmetries P, C, CP, TCP on the propagator (and on its spectral function) are deduced. Its poles are the physical masses; this unambiguously defines the propagating eigenstates. It is diagonalized and its spectrum thoroughly investigated. The role of ``spurious'' states, of zero norm at the poles, is emphasized, in particular for unitarity and for the realization of TCP symmetry. The K_L-K_S mass splitting triggers a tiny difference between their CP violating parameters \epsilon_L and \epsilon_S, without any violation of TCP. A constant mass matrix like used in Quantum Mechanics (QM) can only be introduced in a linear approximation to the inverse propagator, which respects its analyticity and positivity properties; it is however unable to faithfully describe all features of neutral mesons as we determine them in QFT, nor to provide any sensible parameterization of eventual effects of TCP violation. The suitable way to diagonalize the propagator makes use of a bi-orthogonal basis; it is inequivalent to a bi-unitary transformation (unless the propagator is normal, which cannot occur here). Problems linked with the existence of different ``in'' and ``out'' eigenstates are smoothed out. We study phenomenological consequences of the differences between the QFT and QM treatments. The non-vanishing of semi-leptonic asymmetry \delta_S - \delta_L does not signal, unlike usually claimed, TCP violation, while A_TCP keeps vanishing when TCP is realized. We provide expressions invariant by the rephasing of K0 and K0bar.Comment: 44 pages, 2 figures. Version to appear in Int. J. Mod. Phys.

Electroweak Working Group Report

The report summarizes the results of the activities of the Working Group on Precision Calculations for the Z Resonance at CERN during 1994.Comment: 158 Latex, including 37 figures (27 eps figures), 30 tables; The report is part of: D. Bardin, W. Hollik, G. Passarino (eds.), Reports of the working group on precision calculations for the Z resonance, CERN 95-03 (31 March 1995

Moderate Supersymmetric CP Violation

It is well known that supersymmetry (SUSY) gives neutron and electron electric dipole moments ($d_n$ and $d_e$) which are too large by about $10^{3}$. If we assume a SUSY model cannot contain fine-tunings or large mass scales, then one must require that the SUSY breaking mechanism give real soft breaking parameters, in which case the minimal SUSY model has no $CP$ violation other than from the CKM matrix (besides possible strong $CP$ violating effects). We show that in non-minimal SUSY models, a moderate amount of $CP$ violation can be induced through one loop corrections to the scalar potential, giving an effective phase of order $10^{-3}$, and thus implying $d_n$ and $d_e$ can be near their current experimental bounds $naturally$. This moderate amount of SUSY $CP$ violation could also prove important for models of electroweak baryogenesis. We illustrate our results with a specific model.Comment: 19pp plain LATEX, 1 fig (by EMAIL request), TRI-PP-93-86. (Some clarifying comments about renormalizability added--version to appear in Phys. Rev. D

Quarkonium production in SM Higgs decays

We investigate the SM Higgs decays into heavy quarkonia J/\psi and \Upsilon in both color-singlet and color-octet mechanisms. It is found that in J/\psi production the contribution through color-octet processes overwhelm that in color-singlet processes all the intermediate region M_Z<M_{H^0}<2 M_w and the fraction ratio is comparatively large, but in \Upsilon production the contribution through color-octet mechanism is negligible.Comment: 9 pages, LaTex, 4 postscript figures. To appear in Journal of Physics

TeV-scale bileptons, see-saw type II and lepton flavor violation in core-collapse supernova

Electrons and electron neutrinos in the inner core of the core-collapse supernova are highly degenerate and therefore numerous during a few seconds of explosion. In contrast, leptons of other flavors are non-degenerate and therefore relatively scarce. This is due to lepton flavor conservation. If this conservation law is broken by some non-standard interactions, electron neutrinos are converted to muon and tau-neutrinos, and electrons - to muons. This affects the supernova dynamics and the supernova neutrino signal. We consider lepton flavor violating interactions mediated by scalar bileptons, i.e. heavy scalars with lepton number 2. It is shown that in case of TeV-mass bileptons the electron fermi gas is equilibrated with non-electron species inside the inner supernova core at a time-scale of order of (1-100) ms. In particular, a scalar triplet which generates neutrino masses through the see-saw type II mechanism is considered. It is found that supernova core is sensitive to yet unprobed values of masses and couplings of the triplet.Comment: accepted to Eur.Phys.J.