3,476 research outputs found
Bulk Majorons at Colliders
Lepton number violation may arise via the spontaneous breakdown of a global
symmetry. In extra dimensions, spontaneous lepton number violation in the bulk
implies the existence of a Goldstone boson, the majoron J^(0), as well as an
accompanying tower of Kaluza-Klein (KK) excitations, J^(n). Even if the
zero-mode majoron is very weakly interacting, so that detection in low-energy
processes is difficult, the sum over the tower of KK modes may partially
compensate in processes of relevance at high-energy colliders. Here we consider
the inclusive differential and total cross sections for e^- e^- --> W^- W^- J,
where J represents a sum over KK modes. We show that allowed parameter choices
exist for which this process may be accessible to a TeV-scale electron
collider.Comment: 11 pages LaTeX, 3 eps figures (references added
Unifiable Supersymmetric Left-Right Model with E_6 Particle Content
A new supersymmetric gauge model is proposed with particle content chosen
only from the 27 and 27* representations of E_6. The gauge symmetry SU(3) X
SU(2)_L X SU(2)_R X U(1) is realized at the TeV energy scale and the gauge
couplings converge to a single value at around 10^{16} GeV. A discrete Z_4 X
Z_2 symmetry leads to a generalized definition of lepton number and ensures the
absence of tree-level flavor-changing neutral-current interactions at the
electroweak energy scale.Comment: 12 pages (1 figure not included), UCRHEP-T129 (July 1994
Neutron/proton ratio of nucleon emissions as a probe of neutron skin
The dependence between neutron-to-proton yield ratio () and neutron
skin thickness () in neutron-rich projectile induced reactions is
investigated within the framework of the Isospin-Dependent Quantum Molecular
Dynamics (IQMD) model. The density distribution of the Droplet model is
embedded in the initialization of the neutron and proton densities in the
present IQMD model. By adjusting the diffuseness parameter of neutron density
in the Droplet model for the projectile, the relationship between the neutron
skin thickness and the corresponding in the collisions is obtained.
The results show strong linear correlation between and
for neutron-rich Ca and Ni isotopes. It is suggested that may be used
as an experimental observable to extract for neutron-rich nuclei,
which is very significant to the study of the nuclear structure of exotic
nuclei and the equation of state (EOS) of asymmetric nuclear matter.Comment: 7 pages, 5 figures; accepted by Phys. Lett.
Isospin dependence of nucleon effective mass in Dirac Brueckner-Hartree-Fock approach
The isospin dependence of the nucleon effective mass is investigated in the
framework of the Dirac Brueckner-Hartree-Fock (DBHF) approach. The definition
of nucleon scalar and vector effective masses in the relativistic approach is
clarified. Only the vector effective mass is the quantity related to the
empirical value extracted from the analysis in the nonrelatiistic shell and
optical potentials. In the relativistic mean field theory, where the nucleon
scalar and vector potentials are both energy independent, the neutron vector
potential is stronger than that of proton in the neutron rich nuclear matter,
which produces a smaller neutron vector effective mass than that of proton. It
is pointed out that the energy dependence of nucleon potentials has to be
considered in the analysis of the isospin dependence of the nucleon effective
mass. In the DBHF the neutron vector effective mass is larger than that of
proton once the energy dependence of nucleon potentials is considered. The
results are consistent with the analysis of phenomenological isospin dependent
optical potentials.Comment: 4 pages, 3 Postscript figure
Probing the mechanism of EWSB with a rho parameter defined in terms of Higgs couplings
A definition of the rho parameter based on the Higgs couplings with the gauge
bosons, rho_h= g_{hWW}}/c^2_W g_{hZZ}, is proposed as a new probe into the
origin of the mechanism of electroweak symmetry breaking. While
holds in the SM, deviations from one are predicted in models with extended
Higgs sector.
We derive a general expresion of rho_h for a model with arbitrary Higgs
multiplets, and discuss its size within the context of specific models with
Higgs triplets, including the ``Little Higgs'' models recently proposed. We
find the even for Higgs models that incorporate the custodial symmetry to make
rho=1, one could have rho_h\neq 1, which could be tested at the level of a few
percent, with the precision Higgs meassurements expected at the NLC.Comment: 12 pages, 2 figure
Heavy Majorana Neutrinos in the Effective Lagrangian Description: Application to Hadron Colliders
We consider the effects of heavy Majorana neutrinos N with sub-TeV masses. We
argue that the mere presence of these particles would be a signal of physics
beyond the minimal seesaw mechanism and their interactions are, therefore, best
described using an effective Lagrangian. We then consider the complete set of
leading effective operators (up to dimension 6) involving the N and Standard
Model fields and show that these interactions can be relatively easy to track
at high-energy colliders. For example, we find that an exchange of a TeV-scale
heavy vector field can yield thousands of characteristic same-sign lepton
number violating l^+ l^+ j j events (j=light jet) at the LHC if m_N < 600 GeV,
which can also have a distinctive forward-backward asymmetry signal; even the
Tevatron has good prospects for this signature if m_N < 300 GeV.Comment: 4 pages, 1 figur
Parity in left-right symmetric models
We considered parity breaking in some left-right symmetric models. We studied
spontaneous and explicit parity violation in two cases with doublet and triplet
Higgs scalars. The minimization condition in these two cases differ
significantly. A comparative study of these models is presented emphasizing
their phenomenological consequences.Comment: 14 pages latex file; corrected and rewritten introductio
Testing Higgs Triplet Model and Neutrino Mass Patterns
The observed neutrino oscillation data might be explained by new physics at a
TeV scale, which is testable in the future experiments. Among various
possibilities, the low-energy Higgs triplet model is a prime candidate of such
new physics since it predicts clean signatures of lepton flavor violating
processes directly related to the neutrino masses and mixing. It is discussed
how various neutrino mass patterns can be discriminated by examining the lepton
flavor violating decays of charged leptons as well as the collider signatures
of a doubly charged Higgs boson in the model.Comment: 13 pages, revte
The Production of Associated With Photons or Jets as a Probe of New Gauge Boson Couplings
We examine the production of a new gauge boson in association with
photons or jets at future hadron supercolliders as a probe of its couplings to
fermions. Associated jet production is found to be rather insensitive to these
couplings and suffers from large uncertainties as well as substantial
backgrounds. On the other hand, the ratio of rates for associated photon
production to that of conventional production has a rather clean signature
(once appropriate cuts are made), and is found to be quite sensitive to the
choice of extended electroweak model, while being simultaneously insensitive to
structure function uncertainties and QCD corrections. Rates at both the SSC and
LHC are significant for masses in the 1 TeV range.Comment: 14pp, 6 figs(not included), LaTex, ANL-HEP-PR-92-5
Soft Leptogenesis in Higgs Triplet Model
We consider the minimal supersymmetric triplet seesaw model as the origin of
neutrino masses and mixing as well as of the baryon asymmetry of the Universe,
which is generated through soft leptogenesis employing a CP violating phase and
a resonant behavior in the supersymmetry breaking sector. We calculate the full
gauge--annihilation cross section for the Higgs triplets, including all
relevant supersymmetric intermediate and final states, as well as
coannihilations with the fermionic superpartners of the triplets. We find that
these gauge annihilation processes strongly suppress the resulting lepton
asymmetry. As a consequence of this, successful leptogenesis can occur only for
a triplet mass at the TeV scale, where the contribution of soft supersymmetry
breaking terms enhances the CP and lepton asymmetry. This opens up an
interesting opportunity for testing the model in future colliders.Comment: 17 pages, 5 figures; version accepted for publicatio
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