3,359 research outputs found
The PAMELA excess from neutralino annihilation in the NMSSM
We examine whether the cosmic ray positron excess observed by PAMELA can be
explained by neutralino annihilation in the Next-to-Minimal Supersymmetric
Standard Model (NMSSM). The main dark matter annihilation products are the
lightest CP-even scalar h1 plus the lightest CP-odd scalar a1, with the a1
decaying into two muons. The energetic positrons needed to explain PAMELA are
thus obtained in the NMSSM simply from kinematics. The required large
annihilation cross section is obtained from an s-channel resonance with the
heavier CP-odd scalar a2. Various experiments constrain the PAMELA-favored
NMSSM parameter space, including collider searches for a light a1. These
constraints point to a unique corner of the NMSSM parameter space, having a
lightest neutralino mass around 160 GeV and a very light pseudoscalar mass less
than a GeV. A simple parameterized formula for the charge-dependent solar
modulation effects reconciles the discrepancy between the PAMELA data and the
estimated background at lower energies. We also discuss the electron and gamma
ray spectra from the Fermi LAT observations, and point out the discrepancy
between the NMSSM predictions and Fermi LAT preliminary results and possible
resolution. An NMSSM explanation of PAMELA makes three striking and uniquely
correlated predictions: the rise in the PAMELA positron spectrum will turn over
at around 70 GeV, the dark matter particle mass is less than the top quark
mass, and a light sub-GeV pseudoscalar will be discovered at colliders.Comment: 25 pages, 9 figures; final version for PR
Gauge Unification and Quark Masses in a Pati-Salam Model from Branes
We investigate the phase space of parameters in the Pati-Salam model derived
in the context of D-branes scenarios, requiring low energy string scale. We
find that a non-supersymmetric version complies with a string scale as low as
10 TeV, while in the supersymmetric version the string scale raises up to ~2 x
10^7 TeV. The limited energy region for RGE running demands a large tan(beta)
in order to have experimentally acceptable masses for the top and bottom
quarks.Comment: 11 pages, LaTeX, 7 figures include
Dual Response Models for the Fractional Quantum Hall Effect
It is shown that the Jain mapping between states of integer and fractional
quantum Hall systems can be described dynamically as a perturbative
renormalization of an effective Chern-Simons field theory. The effects of
mirror duality symmetries of toroidally compactified string theory on this
system are studied and it is shown that, when the gauge group is compact, the
mirror map has the same effect as the Jain map. The extrinsic ingredients of
the Jain construction appear naturally as topologically non-trivial field
configurations of the compact gauge theory giving a dynamical origin for the
Jain hierarchy of fractional quantum Hall states.Comment: 8 pages LaTe
Brane Boxes: Bending and Beta Functions
We study the type IIB brane box configurations recently introduced by Hanany
and Zaffaroni. We show that even at finite string coupling, one can construct
smooth configurations of branes with fairly arbitrary gauge and flavor
structure. Limiting our attention to the better understood case where NS-branes
do not intersect over a four dimensional surface gives some restrictions on the
theories, but still permits many examples, both anomalous and non-anomalous. We
give several explicit examples of such configurations and discuss what
constraints can be imposed on brane-box theories from bending considerations.
We also discuss the relation between brane bending and beta-functions for
brane-box configurations.Comment: latex, 18 pages, 8 figure
Gauge Invariant Effective Lagrangian for Kaluza-Klein Modes
We construct a manifestly gauge invariant Lagrangian in 3+1 dimensions for N
Kaluza-Klein modes of an SU(m) gauge theory in the bulk. For example, if the
bulk is 4+1, the effective theory is \Pi_{i=1}^{N+1} SU(m)_i with N chiral
(\bar{m},m) fields connecting the groups sequentially. This can be viewed as a
Wilson action for a transverse lattice in x^5, and is shown explicitly to match
the continuum 4+1 compactifed Lagrangian truncated in momentum space. Scale
dependence of the gauge couplings is described by the standard renormalization
group technique with threshold matching, leading to effective power law
running. We also discuss the unitarity constraints, and chiral fermions.Comment: 21 pages, 4 figure
On High-Energy Behavior of Cross Sections in Theories with Large Extra Dimensions
We discuss the high-energy behavior of cross sections in theories with large
extra dimensions and low-scale quantum gravity, addressing two particular
issues: (i) the tension of the D-branes, and (ii) bounds on the cross section
and their relation to approximations in the mode sum over Kaluza-Klein-graviton
exchanges.Comment: 6 pages, late
Compact Hyperbolic Extra Dimensions: Branes, Kaluza-Klein Modes and Cosmology
We reconsider theories with low gravitational (or string) scale M_* where
Newton's constant is generated via new large-volume spatial dimensions, while
Standard Model states are localized to a 3-brane. Utilizing compact hyperbolic
manifolds (CHM's) we show that the spectrum of Kaluza-Klein (KK) modes is
radically altered. This allows an early universe cosmology with normal
evolution up to substantial temperatures, and completely negates the
constraints on M_* arising from astrophysics. Furthermore, an exponential
hierarchy between the usual Planck scale and the true fundamental scale of
physics can emerge with only order unity coefficients. The linear size of the
internal space remains small. The proposal has striking testable signatures.Comment: 4 pages, no figure
Constrains on non-Newtonian gravity from the experiment on neutron quantum states in the Earth's gravitational field
An upper limit to non-Newtonian attracive forces is obtained from the
measurement of quantum states of neutrons in the Earth's gravitational field.
This limit improves the existing constrains in the nanometer range
AdS/CFT for Four-Point Amplitudes involving Gravitino Exchange
In this paper we compute the tree-level four-point scattering amplitude of
two dilatini and two axion-dilaton fields in type IIB supergravity in AdS5 x
S5. A special feature of this process is that there is an "exotic" channel in
which there are no singleparticle poles. Another novelty is that this process
involves the exchange of a bulk gravitino. The amplitude is interpreted in
terms of N = 4 supersymmetric Yang-Mills theory at large 't Hooft coupling.
Properties of the Operator Product Expansion are used to analyze the various
contributions from single- and double-trace operators in the weak and strongly
coupled regimes, and to determine the anomalous dimensions of semi-short
operators. The analysis is particularly clear in the exotic channel, given the
absence of BPS states.Comment: 32 pages, 1 figure. Published Version. Minor change
Successful Yukawa structures in Warped Extra Dimensions
For a RS model, with SM fields in the bulk and the Higgs boson on the
TeV-brane, we suggest two specific structures for the Yukawa couplings, one
based on a permutation symmetry and the other on the Universal Strength of
Yukawa couplings hypothesis (USY). In USY, all Yukawa couplings have equal
strength and the difference in the Yukawa structure lies in some complex phase.
In both scenarios, all Yukawa couplings are of the same order of magnitude.
Thus, the main features of the fermion hierarchies are explained through the RS
geometrical mechanism, and not because some Yukawa coupling is extremely small.
We find that the RS model is particularly appropriate to incorporate the
suggested Yukawa configurations. Indeed, the RS geometrical mechanism of
fermion locations along the extra dimension, combined with the two Yukawa
scenarios, reproduces all the present experimental data on fermion masses and
mixing angles. It is quite remarkable that in the USY case, only two complex
phases of definite value +-Pi/2 are sufficient to generate the known neutrino
mass differences, while at same time, permitting large leptonic mixing in
agreement with experiment.Comment: 11 page
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