1,590 research outputs found

### SIMP (Strongly Interacting Massive Particle) Search

We consider laboratory experiments that can detect stable, neutral strongly
interacting massive particles (SIMPs). We explore the SIMP annihilation cross
section from its minimum value (restricted by cosmological bounds) to the barn
range, and vary the mass values from a GeV to a TeV. We also consider the
prospects and problems of detecting such particles at the Tevatron.Comment: Latex. 7 pages, 1 eps figure. Proceedings to the 4th UCLA Symposium
on Dark Matter DM2000, Marina del Rey, CA, USA, Feb. 23-25, 200

### Spontaneous Parity Violation in SUSY Strong Gauge Theory

We suggest simple models of spontaneous parity violation in supersymmetric
strong gauge theory. We focus on left-right symmetric model and investigate
vacuum with spontaneous parity violation. Non-perturbative effects are
calculable in supersymmetric gauge theory, and we suggest two new models. The
first model shows confinement, and the second model has a dual description of
the theory. The left-right symmetry breaking and electroweak symmetry breaking
are simultaneously occurred with the suitable energy scale hierarchy. The
second model also induces spontaneous supersymmetry breaking.Comment: 14 page

### Phenomenological Consequences of sub-leading Terms in See-Saw Formulas

Several aspects of next-to-leading (NLO) order corrections to see-saw
formulas are discussed and phenomenologically relevant situations are
identified. We generalize the formalism to calculate the NLO terms developed
for the type I see-saw to variants like the inverse, double or linear see-saw,
i.e., to cases in which more than two mass scales are present. In the standard
type I case with very heavy fermion singlets the sub-leading terms are
negligible. However, effects in the percent regime are possible when
sub-matrices of the complete neutral fermion mass matrix obey a moderate
hierarchy, e.g. weak scale and TeV scale. Examples are cancellations of large
terms leading to small neutrino masses, or inverse see-saw scenarios. We
furthermore identify situations in which no NLO corrections to certain
observables arise, namely for mu-tau symmetry and cases with a vanishing
neutrino mass. Finally, we emphasize that the unavoidable unitarity violation
in see-saw scenarios with extra fermions can be calculated with the formalism
in a straightforward manner.Comment: 22 pages, matches published versio

### A Sharp Inequality of Markov Type for Polynomials Associated with Laguerre Weight

AbstractThe best possible constant An in an inequality of Markov type [ddx(e−xpn(x))][0, ∞)⩽An‖e−xpn(x)‖[0, ∞), where ‖·‖[0, ∞) denotes the sup-norm on the half real line [0, ∞) and pn is an arbitrary polynomial of degree at most n, is determined in terms of the weighted Chebyshev polynomials associated with the Laguerre weight e−x on [0, ∞)

### Gauged Flavor Group with Left-Right Symmetry

We construct an anomaly-free extension of the left-right symmetric model,
where the maximal flavor group is gauged and anomaly cancellation is guaranteed
by adding new vectorlike fermion states. We address the question of the lowest
allowed flavor symmetry scale consistent with data. Because of the mechanism
recently pointed out by Grinstein et al. tree-level flavor changing neutral
currents turn out to play a very weak constraining role. The same occurs, in
our model, for electroweak precision observables. The main constraint turns out
to come from WR-mediated flavor changing neutral current box diagrams,
primarily K - Kbar mixing. In the case where discrete parity symmetry is
present at the TeV scale, this constraint implies lower bounds on the mass of
vectorlike fermions and flavor bosons of 5 and 10 TeV respectively. However,
these limits are weakened under the condition that only SU(2)_R x U(1)_{B-L} is
restored at the TeV scale, but not parity. For example, assuming the SU(2)
gauge couplings in the ratio gR/gL approx 0.7 allows the above limits to go
down by half for both vectorlike fermions and flavor bosons. Our model provides
a framework for accommodating neutrino masses and, in the parity symmetric
case, provides a solution to the strong CP problem. The bound on the lepton
flavor gauging scale is somewhat stronger, because of Big Bang Nucleosynthesis
constraints. We argue, however, that the applicability of these constraints
depends on the mechanism at work for the generation of neutrino masses.Comment: 1+23 pages, 1 table, 5 figures. v3: some more textual fixes (main
change: discussion of Lepton Flavor Violating observables rephrased). Matches
journal versio

### Mirror Dark Matter

There appear to be three challenges that any theory of dark matter must face:
(i) why is $\Omega_{DM}$ of the same order as $\Omega_{Baryons}$ ? (ii) what
are the near solar mass objects ($\sim 0.5 M_{\odot}$) observed by the MACHO
microlensing project ? and (iii) understanding the shallow core density profile
of the halos of dwarf as well as low surface brightness galaxies. The popular
cold dark matter candidates, the SUSY LSP and the axion fail to meet these
challenges. We argue that in the mirror model suggested recently to explain the
neutrino anomalies, the mirror baryons being 15-20 times heavier than familiar
baryons, can play the role of the cold dark matter and provide reasonable
explanation of all three above properties without extra assumptions.Comment: Latex, 10 pages; Invited talk presented in PASCOS99 workshop, held in
Lake Tahoe, Dec. 1999 and DM2000 workshop held in Los Angeles, February, 200

### Strong Sphalerons and Electroweak Baryogenesis

We analyze the spontaneous baryogenesis and charge transport mechanisms
suggested by Cohen, Kaplan and Nelson for baryon asymmetry generation in
extended versions of electroweak theory. We find that accounting for
non-perturbative chirality-breaking transitions due to strong sphalerons
reduces the baryonic asymmetry by the factor $(m_t/\pi T)^2$ or $\alpha_W$,
provided those processes are in thermal equilibrium.Comment: CERN-TH.7080/9

### S3 as a flavour symmetry for quarks and leptons after the Daya Bay result on \theta 13

We present a model based on the flavour group S3 X Z3 X Z6 to explain the
main features of fermion masses and mixing. In particular, in the neutrino
sector the breaking of the S3 symmetry is responsible for a naturally small
r=\Delta m^2_sol/\Delta m^2_atm and suitable next-to-leading order corrections
bring \theta 13 at the level of ~ 0.13, fully compatible with the recent Daya
Bay result. In the quark sector, the model accommodates the different mass
hierarchies in the up and down quark sectors as well as the Cabibbo angle and
Vcb (or Vub, depending on the charge assignment of the right-handed b-quark) in
the correct range.Comment: 15 pages, 3 figure

### Dynamical R-parity Breaking at the LHC

In a class of extensions of the minimal supersymmetric standard model with
(B-L)/left-right symmetry that explains the neutrino masses, breaking R-parity
symmetry is an essential and dynamical requirement for successful gauge
symmetry breaking. Two consequences of these models are: (i) a new kind of
R-parity breaking interaction that protects proton stability but adds new
contributions to neutrinoless double beta decay and (ii) an upper bound on the
extra gauge and parity symmetry breaking scale which is within the large hadron
collider (LHC) energy range. We point out that an important prediction of such
theories is a potentially large mixing between the right-handed charged lepton
($e^c$) and the superpartner of the right-handed gauge boson ($\widetilde
W_R^+$), which leads to a brand new class of R-parity violating interactions of
type $\widetilde{\mu^c}^\dagger\nu_\mu^c e^c$ and \widetilde{d^c}^\dagger\u^c
e^c. We analyze the relevant constraints on the sparticle mass spectrum and
the LHC signatures for the case with smuon/stau NLSP and gravitino LSP. We note
the "smoking gun" signals for such models to be lepton flavor/number violating
processes: $pp\to \mu^\pm\mu^\pm e^+e^-jj$ (or $\tau^\pm\tau^\pm e^+e^-jj$) and
$pp\to\mu^\pm e^\pm b \bar{b} jj$ (or $\tau^\pm e^\pm b \bar{b} jj$) without
significant missing energy. The predicted multi-lepton final states and the
flavor structure make the model be distinguishable even in the early running of
the LHC.Comment: 30 pages, 13 figures, 6 tables, reference adde

### Two Simple W' Models for the Early LHC

W' gauge bosons are good candidates for early LHC discovery. We define two
reference models, one containing a W'_R and one containing a W'_L, which may
serve as ``simplified models'' for presenting experimental results of W'
searches at the LHC. We present the Tevatron bounds on each model and compute
the constraints from precision electroweak observables. We find that indirect
low-energy constraints on the W'_L are quite strong. However, for a W'_R
coupling to right-handed fermions there exists a sizeable region in parameter
space beyond the bounds from the Tevatron and low-energy precision measurements
where even 50 inverse picobarns of integrated LHC luminosity are sufficient to
discover the W'_R. The most promising final states are two leptons and two
jets, or one lepton recoiling against a ``neutrino jet''. A neutrino jet is a
collimated object consisting of a hard lepton and two jets arising from the
decay of a highly boosted massive neutrino.Comment: 20 pages, 8 figures. v2: references adde

- …