281 research outputs found

### Z boson decay to photon plus Kaluza-Klein graviton in large extra dimensions

In the large extra dimensional ADD scenario, Z bosons undergo a one-loop
decay into a photon and Kaluza-Klein towers of gravitons/gravi-scalars. We
calculate such a decay width, extending previous arguments about the general
form of the four-dimensional on-shell amplitude. The amplitudes calculated are
relevant to processes in other extra dimensional models where the Standard
Model fields are confined to a 4-brane.Comment: 47 pages, uses feynmp for diagrams. v2: typographical corrections for
letter-sized paper and to correct feynmf parsing error. v3: minor error in
polarisation averaging and reference corrected. v4: reflects changes for
published version; arithmetic error corrected and reference updated; section
on transversality conditions not present in published version retaine

### Resonant slepton production at the LHC in models with an ultralight gravitino

We examine resonant slepton production at the LHC with gravitinos in the
final state. The slepton undergoes gauge decay into a neutralino and a lepton,
the neutralino decays into a photon and a gravitino. By measuring the
transverse masses of the gamma- G and the l-gamma- G subsystems it is possible
to accurately reconstruct both the slepton and neutralino masses. In some
regions of parameter space the slepton decays directly into a lepton and
gravitino, giving an identical experimental topology to W production (l missing
E_T). We present the novel matrix element squared for lepton-gravitino
production. A peak in the tail of the lepton-missing momentum transverse mass
distribution of the W provides a signature for the process and an accurate
measurement of the slepton mass. We display the search reach for the LHC and
300 fb^{-1} of integrated luminosity.Comment: 13 pages. Minor changes in v

### Requirements on collider data to match the precision of WMAP on supersymmetric dark matter

If future colliders discover supersymmetric particles and probe their
properties, one could predict the dark matter density of the Universe and would
constrain cosmology with the help of precision data provided by WMAP and
PLANCK.
We investigate how well the relic density can be predicted in minimal
supergravity (mSUGRA), with and without the assumption of mSUGRA when analysing
data. We determine the parameters to which the relic density is most sensitive,
and quantify the collider accuracy needed. Theoretical errors in the prediction
are investigated in some detail.Comment: 42 pages, 16 figures. v2 incorporates referee's comments: minor
corrections/clarifications with additional figures to show regions of m12-m0
plane considere

### Including R-parity violation in the numerical computation of the spectrum of the minimal supersymmetric standard model: SOFTSUSY

Current publicly available computer programs calculate the spectrum and
couplings of the minimal supersymmetric standard model under the assumption of
R-parity conservation. Here, we describe an extension to the SOFTSUSY program
which includes R-parity violating effects. The user provides a theoretical
boundary condition upon the high-scale supersymmetry breaking R-parity
violating couplings. Successful radiative electroweak symmetry breaking,
electroweak and CKM matrix data are used as weak-scale boundary conditions. The
renormalisation group equations are solved numerically between the weak scale
and a high energy scale using a nested iterative algorithm. This paper serves
as a manual to the R-parity violating mode of the program, detailing the
approximations and conventions used.Comment: Updated to SOFTSUSY3.3.3. Program may be downloaded from
http://projects.hepforge.org/softsusy/ and future manuals will be distributed
with the cod

### Two Graviton Production at $e^+e^-$ and Hadron Hadron Colliders in the Randall-Sundrum Model

We compute the pair production cross section of two Kaluza Klein modes in the
Randall-Sundrum model at $e^+e^-$ and hadron hadron colliders. These processes
are interesting because they get dominant contribution from the graviton
interaction at next to leading order. Hence they provide a nontrivial test of
the low scale gravity models. All the Feynman rules at next to leading order
are also presented. These rules may be useful for many phenomenological
applications including the computation of higher order loop corrections.Comment: 24 pages, 11 figures, some typos correcte

### Naturalness Priors and Fits to the Constrained Minimal Supersymmetric Standard Model

We examine the effect of a prior that favours low values of fine-tuning on
Bayesian multi-dimensional fits of the constrained minimal supersymmetric
standard model (CMSSM or mSUGRA) to current data. The dark matter relic
density, the anomalous magnetic moment of the muon and the branching ratio of
b->s gamma are all used to constrain the model via a Markov Chain Monte Carlo
sampler. As a result of the naturalness prior, posterior probability
distributions skew towards lighter higgs and sparticle masses, the effect being
most pronounced in the gaugino sector. Interestingly, slepton masses are an
exception and skew towards heavier masses. The lightest CP-even Higgs h^0-pole
region becomes allowed at the 2 sigma level for the latest combination of
measurements of m_t=172.7+/-2.9 GeV, provided we allow for a theoretical error
in the prediction of its mass m_{h^0}. m_{h^0} is constrained to be less than
120 GeV at the 95% C.L. Probing the branching ratio of B_s->mu^+ mu^- to the
level of 2 x 10^{-8}, as might be achieved by the Tevatron experiments, would
cover 32% of the probability density, irrespective of which of the two priors
is used.Comment: 15 pages, 5 figures. Ref adde

### SOFTSUSY: a program for calculating supersymmetric spectra

SOFTSUSY is a program which accurately calculates the spectrum of
superparticles in the CP-conserving Minimal Supersymmetric Standard Model
(MSSM), with a full flavour mixing structure. The program solves the
renormalisation group equations with theoretical constraints on soft
supersymmetry breaking terms provided by the user. Weak-scale gauge coupling
and fermion mass data (including one-loop finite MSSM corrections) are used as
a boundary condition, as well as successful radiative electroweak symmetry
breaking. The program can also calculate a measure of fine-tuning. The program
structure has been designed to easily generalise to extensions of the MSSM.
This article serves as a self-contained guide to prospective users, and
indicates the conventions and approximations used.Comment: Updated for SOFTSUSY3.3.3. Can be downloaded from
http://projects.hepforge.org/softsusy/ Further updated versions of the manual
will be distributed with the cod

### Study of the Growth of Entropy Modes in MSSM Flat Directions Decay: Constraints on the Parameter Space

We study how the resonant decay of moduli fields arising in the Minimal
Supersymmetric Standard Model (MSSM) could affect large scale curvature
perturbations in the early universe. It has been known for some time that the
presence of entropy perturbations in a multi-component system can act as seeds
for the curvature perturbations on all scales. These entropy perturbations
could be amplified exponentially if one of the moduli decays via stochastic
resonance, affecting the curvature power spectrum in the process. By imposing
the COBE normalization on this power spectrum, one could put constraints on the
masses and couplings of the underlying particle physics model without having to
rely on collider experiments. We discuss in detail the case of the MSSM but
this method could be applied to other theories beyond the Standard Model.Comment: 6 pages, 1 figure, revtex4, comments added in section II, 1 reference
adde

### Naturalness Reach of the Large Hadron Collider in Minimal Supergravity

We re-analyse the prospects of discovering supersymmetry at the LHC, in order to re-express coverage in terms of a fine-tuning parameter and to extend the analysis to scalar masses (m_0) above 2 TeV. We use minimal supergravity (mSUGRA) unification assumptions for the SUSY breaking parameters. Such high values of m_0 have recently been found to have a focus point, leading to relatively low fine-tuning. In addition, improvements in the simulations since the last study mean that this region no longer lacks radiative electroweak symmetry breaking. The best fine tuning reach is found in a mono-leptonic channel, where for mu>0, A_0=0 and tan beta=10 (corresponding to the focus point), all points in mSUGRA with m_0 < 4000 GeV, with a fine tuning measure up to 300 (570) are covered by the search, where the definition of fine-tuning excludes (includes) the contribution from the top Yukawa coupling. Even for arbitrarily high m_0, mSUGRA does not evade detection provided the gaugino mass parameter M_{1/2} < 460 GeV

### SUSY Parameter Analysis at TeV and Planck Scales

Coherent analyses at future LHC and LC experiments can be used to explore the
breaking mechanism of supersymmetry and to reconstruct the fundamental theory
at high energies, in particular at the grand unification scale. This will be
exemplified for minimal supergravity.Comment: 7 pages, 3 figures, uses espcrc2.sty (included), Proceedings, Loops
and Legs 2004, Zinnowitz on Usedo

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