1,566 research outputs found
Electric Charge Quantization
Experimentally it has been known for a long time that the electric charges of
the observed particles appear to be quantized. An approach to understanding
electric charge quantization that can be used for gauge theories with explicit
factors -- such as the standard model and its variants -- is
pedagogically reviewed and discussed in this article. This approach uses the
allowed invariances of the Lagrangian and their associated anomaly cancellation
equations. We demonstrate that charge may be de-quantized in the
three-generation standard model with massless neutrinos, because differences in
family-lepton--numbers are anomaly-free. We also review the relevant
experimental limits. Our approach to charge quantization suggests that the
minimal standard model should be extended so that family-lepton--number
differences are explicitly broken. We briefly discuss some candidate extensions
(e.g. the minimal standard model augmented by Majorana right-handed neutrinos).Comment: 18 pages, LaTeX, UM-P-92/5
Evidence for mirror dark matter from the CDMS low energy electron recoil spectrum
We point out that mirror dark matter predicts low energy ( keV) electron recoils from mirror electron scattering as
well as nuclear recoils from mirror ion scattering. The former effect is
examined and applied to the recently released low energy electron recoil data
from the CDMS collaboration. We speculate that the sharp rise in electron
recoils seen in CDMS below 2 keV might be due to mirror electron scattering and
show that the parameters suggested by the data are roughly consistent with the
mirror dark matter explanation of the annual modulation signal observed in the
DAMA/Libra and DAMA/NaI experiments. Thus, the CDMS data offer tentative
evidence supporting the mirror dark matter explanation of the DAMA experiments,
which can be more rigorously checked by future low energy electron recoil
measurements.Comment: about 9 pages, comments welcome
Solutions of the atmospheric, solar and LSND neutrino anomalies from TeV scale quark-lepton unification
There is a unique gauge model which
allows quarks and leptons to be unified at the TeV scale. It is already known
that the neutrino masses arise radiatively in the model and are naturally
light. We study the atmospheric, solar and LSND neutrino anomalies within the
framework of this model.Comment: Minor changes, 31 page
On the sign of the neutrino asymmetry induced by active-sterile neutrino oscillations in the early Universe
We deal with the problem of the final sign of the neutrino asymmetry
generated by active-sterile neutrino oscillations in the Early Universe solving
the full momentum dependent quantum kinetic equations. We study the parameter
region . For a large
range of values the sign of the neutrino asymmetry is fixed
and does not oscillate. For values of mixing parameters in the region
, the neutrino asymmetry appears to undergo rapid
oscillations during the period where the exponential growth occurs. Our
numerical results indicate that the oscillations are able to change the
neutrino asymmetry sign. The sensitivity of the solutions and in particular of
the final sign of lepton number to small changes in the initial conditions
depends whether the number of oscillations is high enough. It is however not
possible to conclude whether this effect is induced by the presence of a
numerical error or is an intrinsic feature. As the amplitude of the statistical
fluctuations is much lower than the numerical error, our numerical analysis
cannot demonstrate the possibility of a chaotical generation of lepton domains.
In any case this possibility is confined to a special region in the space of
mixing parameters and it cannot spoil the compatibility of the
solution to the neutrino atmospheric data
obtained assuming a small mixing of the with an
neutrino.Comment: Typo's corrected, accepted for publication in Phys.Rev.
Properties of quasi two-dimensional condensates in highly anisotropic traps
We theoretically investigate some of the observable properties of quasi
two-dimensional condensates. Using a variational model based on a
Gaussian-parabolic trial wavefunction we calculate chemical potential,
condensate size in time-of-flight, release energy and collective excitation
spectrum for varying trap geometries and atom numbers and find good agreement
with recent published experimental results.Comment: 7 pages, 4 figure
Mirror matter admixtures in K_S to gamma gamma
The latest measurement of the K_S to gamma gamma branching ratio clearly
shows an enhancement over the current theoretical prediction. As in other K and
B meson decays, this invites to consider the possibility of the contribution of
new physics. We study a particular form of the latter, which may be referred to
as manifest mirror symmetry. The experimental data are described using
previously determined values for the mixing angles of the admixtures of mirror
matter in ordinary hadrons and by assuming that for pi^0, eta, eta', the mirror
decay amplitudes have the same magnitudes as their ordinary counterparts
Implications of TeV scale SU(4)xSU(2)_LxSU(2)_R quark-lepton unification
The alternative gauge model, which
allows unification of the quarks and leptons at the TeV scale, is studied in
detail. We discuss the implications for nucleon decay, B and K rare meson
decays and neutrino masses. We also explain how this model solves the gauge
hierarchy problem without using supersymmetry or extra large dimensions.Comment: About 12 pages, 3 eps figs, late
Model for a Light Z' Boson
A model of a light boson is constructed and phenomenological bounds are
derived. This boson arises from a very simple extension to the Standard
Model, and it is constrained to be light because the vacuum expectation values
which generate its mass also break the electroweak gauge group. It is difficult
to detect experimentally because it couples exclusively or primarily (depending
on symmetry breaking details) to second and third generation leptons. However,
if the boson is sufficiently light, then there exists the possibility of
the two-body decay occuring. This will provide a
striking signature to test the model.Comment: 20 pages + 5 pages of figures (appended as postscipt files), LaTeX,
OITS-53
Quark-Lepton Quartification
We propose that quarks and leptons are interchangeable entities in the
high-energy limit. This naturally results in the extension of [SU(3)]^3
trinification to [SU(3)]^4 quartification. In addition to the unbroken color
SU(3)_q of quarks, there is now also a color SU(3)_l of leptons which reduces
to an unbroken SU(2)_l. We discuss the natural occurrence of SU(2)_l doublets
at the TeV energy scale, which leads remarkably to the unification of all gauge
couplings without supersymmetry. Proton decay occurs through the exchange of
scalar bosons, with a lifetime in the range 10^{34} - 10^{36} years.Comment: 12 pages, 4 figures. Reference adde
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