646 research outputs found
Supersymmetry in the shadow of photini
Additional neutral gauge fermions -- "photini" -- arise in string
compactifications as superpartners of U(1) gauge fields. Unlike their vector
counterparts, the photini can acquire weak-scale masses from soft SUSY breaking
and lead to observable signatures at the LHC through mass mixing with the bino.
In this work we investigate the collider consequences of adding photini to the
neutralino sector of the MSSM. Relatively large mixing of one or more photini
with the bino can lead to prompt decays of the lightest ordinary supersymmetric
particle; these extra cascades transfer most of the energy of SUSY decay chains
into Standard Model particles, diminishing the power of missing energy as an
experimental handle for signal discrimination. We demonstrate that the missing
energy in SUSY events with photini is reduced dramatically for supersymmetric
spectra with MSSM neutralinos near the weak scale, and study the effects on
limits set by the leading hadronic SUSY searches at ATLAS and CMS. We find that
in the presence of even one light photino the limits on squark masses from
hadronic searches can be reduced by 400 GeV, with comparable (though more
modest) reduction of gluino mass limits. We also consider potential discovery
channels such as dilepton and multilepton searches, which remain sensitive to
SUSY spectra with photini and can provide an unexpected route to the discovery
of supersymmetry. Although presented in the context of photini, our results
apply in general to theories in which additional light neutral fermions mix
with MSSM gauginos.Comment: 23 pages, 8 figures, references adde
Dark Force Detection in Low Energy e-p Collisions
We study the prospects for detecting a light boson X with mass m_X < 100 MeV
at a low energy electron-proton collider. We focus on the case where X
dominantly decays to e+ e- as motivated by recent "dark force" models. In order
to evade direct and indirect constraints, X must have small couplings to the
standard model (alpha_X 10 MeV).
By comparing the signal and background cross sections for the e- p e+ e- final
state, we conclude that dark force detection requires an integrated luminosity
of around 1 inverse attobarn, achievable with a forthcoming JLab proposal.Comment: 38 pages, 19 figures; v2, references adde
Complementarity of Galactic radio and collider data in constraining WIMP dark matter models
In this work we confront dark matter models to constraints that may be
derived from radio synchrotron radiation from the Galaxy, taking into account
the astrophysical uncertainties and we compare these to bounds set by
accelerator and complementary indirect dark matter searches. Specifically we
apply our analysis to three popular particle physics models. First, a generic
effective operator approach, in which case we set bounds on the corresponding
mass scale, and then, two specific UV completions, the Z' and Higgs portals. We
show that for many candidates, the radio synchrotron limits are competitive
with the other searches, and could even give the strongest constraints (as of
today) with some reasonable assumptions regarding the astrophysical
uncertainties.Comment: 22 pages, 12 figure
Low-Energy Signals from Kinetic Mixing with a Warped Abelian Hidden Sector
We investigate the detailed phenomenology of a light Abelian hidden sector in
the Randall-Sundrum framework. Relative to other works with light hidden
sectors, the main new feature is a tower of hidden Kaluza-Klein vectors that
kinetically mix with the Standard Model photon and Z. We investigate the decay
properties of the hidden sector fields in some detail, and develop an approach
for calculating processes initiated on the ultraviolet brane of a warped space
with large injection momentum relative to the infrared scale. Using these
results, we determine the detailed bounds on the light warped hidden sector
from precision electroweak measurements and low-energy experiments. We find
viable regions of parameter space that lead to significant production rates for
several of the hidden Kaluza-Klein vectors in meson factories and fixed-target
experiments. This offers the possibility of exploring the structure of an extra
spacetime dimension with lower-energy probes.Comment: (1+32) Pages, 13 Figures. v2: JHEP version (minor modifications,
results unchanged
The ZZ' kinetic mixing in the light of the recent direct and indirect dark matter searches
Several constructions, of stringy origins or not, generate abelian gauge
extensions of the Standard Model (SM). Even if the particles of the SM are not
charged under this extra , one cannot avoid the presence of a kinetic
mixing between and the hypercharge . In this work, we
constraint drastically this kinetic mixing, taking into account the recent
experimental data from accelerator physics, direct detection and indirect
detection of dark matter. We show that the region respecting WMAP and
experimental constraints is now very narrowed along the pole line where
, being the gauge boson associated to the extra
.Comment: 9 pages, 3 figures, final version to appear in JCA
Low-Energy Probes of a Warped Extra Dimension
We investigate a natural realization of a light Abelian hidden sector in an
extended Randall-Sundrum (RS) model. In addition to the usual RS bulk we
consider a second warped space containing a bulk U(1)_x gauge theory with a
characteristic IR scale of order a GeV. This Abelian hidden sector can couple
to the standard model via gauge kinetic mixing on a common UV brane. We show
that if such a coupling induces significant mixing between the lightest U(1)_x
gauge mode and the standard model photon and Z, it can also induce significant
mixing with the heavier U(1)_x Kaluza-Klein (KK) modes. As a result it might be
possible to probe several KK modes in upcoming fixed-target experiments and
meson factories, thereby offering a new way to investigate the structure of an
extra spacetime dimension.Comment: 26 pages, 1 figure, added references, corrected minor typos, same as
journal versio
Validation of techniques to mitigate copper surface contamination in CUORE
In this article we describe the background challenges for the CUORE
experiment posed by surface contamination of inert detector materials such as
copper, and present three techniques explored to mitigate these backgrounds.
Using data from a dedicated test apparatus constructed to validate and compare
these techniques we demonstrate that copper surface contamination levels better
than 10E-07 - 10E-08 Bq/cm2 are achieved for 238U and 232Th. If these levels
are reproduced in the final CUORE apparatus the projected 90% C.L. upper limit
on the number of background counts in the region of interest is 0.02-0.03
counts/keV/kg/y depending on the adopted mitigation technique.Comment: 10 pages, 6 figures, 6 table
The low energy spectrum of TeO2 bolometers: results and dark matter perspectives for the CUORE-0 and CUORE experiments
We collected 19.4 days of data from four 750 g TeO2 bolometers, and in three
of them we were able to set the energy threshold around 3 keV using a new
analysis technique. We found a background rate ranging from 25 cpd/keV/kg at 3
keV to 2 cpd/keV/kg at 25 keV, and a peak at 4.7 keV. The origin of this peak
is presently unknown, but its presence is confirmed by a reanalysis of 62.7
kg.days of data from the finished CUORICINO experiment. Finally, we report the
expected sensitivities of the CUORE0 (52 bolometers) and CUORE (988 bolometers)
experiments to a WIMP annual modulation signal.Comment: 9 pages, 10 figure
Using multimedia and peer assessment to promote collaborative e-learning
Collaborative e-learning is increasingly appealing as a pedagogical approach that can positively affect student learning. We propose a didactical model that integrates multimedia with collaborative tools and peer assessment to foster collaborative e-learning. In this paper, we explain it and present the results of its application to the “International Seminars on Materials Science” online course. The proposed didactical model consists of five educational activities. In the first three, students review the multimedia resources proposed by the teacher in collaboration with their classmates. Then, in the last two activities, they create their own multimedia resources and assess those created by their classmates. These activities foster communication and collaboration among students and their ability to use and create multimedia resources. Our purpose is to encourage the creativity, motivation, and dynamism of the learning process for both teachers and students
A precision study of the fine tuning in the DiracNMSSM
Recently the DiracNMSSM has been proposed as a possible solution to reduce
the fine tuning in supersymmetry. We determine the degree of fine tuning needed
in the DiracNMSSM with and without non-universal gaugino masses and compare it
with the fine tuning in the GNMSSM. To apply reasonable cuts on the allowed
parameter regions we perform a precise calculation of the Higgs mass. In
addition, we include the limits from direct SUSY searches and dark matter
abundance. We find that both models are comparable in terms of fine tuning,
with the minimal fine tuning in the GNMSSM slightly smaller.Comment: 20 pages + appendices, 10 figure
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