893 research outputs found
SUSY-QCD Corrections to Dark Matter Annihilation in the Higgs Funnel
We compute the full O(alpha_s) SUSY-QCD corrections to dark matter
annihilation in the Higgs-funnel, resumming potentially large mu tan beta and
A_b contributions and keeping all finite O(m_b,s,1/tan^2 beta) terms. We
demonstrate numerically that these corrections strongly influence the
extraction of SUSY mass parameters from cosmological data and must therefore be
included in common analysis tools such as DarkSUSY or micrOMEGAs.Comment: 4 pages, 3 (partly color) figures, version to be published in PR
Flavour Violation in Gauge-Mediated Supersymmetry Breaking Models: Experimental Constraints and Phenomenology at the LHC
We present an extensive analysis of gauge-mediated supersymmetry breaking
models with minimal and non-minimal flavour violation. We first demonstrate
that low-energy, precision electroweak, and cosmological constraints exclude
large "collider-friendly" regions of the minimal parameter space. We then
discuss various possibilities how flavour violation, although naturally
suppressed, may still occur in gauge-mediation models. The introduction of
non-minimal flavour violation at the electroweak scale is shown to relax the
stringent experimental constraints, so that benchmark points, that are also
cosmologically viable, can be defined and their phenomenology, i.e. squark and
gaugino production cross sections with flavour violation, at the LHC can be
studied.Comment: 29 pages, 1 table, 27 figures. Minor changes. Version published in
Nucl. Phys.
Slepton production in polarized hadron collisions
We calculate cross sections and asymmetries for slepton pair production
through neutral and charged electroweak currents in polarized hadron collisions
for general slepton masses and including mixing of the left- and right-handed
interaction eigenstates relevant for third generation sleptons. Our analytical
results confirm and extend a previous calculation. Numerically, we show that
measurements of the longitudinal single-spin asymmetry at the existing
polarized pp collider RHIC and at possible polarization upgrades of the
Tevatron or the LHC would allow for a determination of the tau slepton mixing
angle and/or the associated supersymmetry breaking parameters Lambda for gauge
mediation and A0 for minimal supergravity. Furthermore, the Standard Model
background from tau pair production can be clearly distinguished due to the
opposite sign of the associated asymmetry.Comment: 16 pages, 4 figures; Tevatron/LHC polarization and tau identification
discussed, typos correcte
Precision predictions for associated gluino-gaugino production at the LHC
Now that the mass limits for gluinos have been pushed to the few-TeV range,
they might only be visible at the LHC in associated production with lighter
gauginos. We compute the corresponding cross section at next-to-leading
logarithmic (NLL) and next-to-leading order (NLO) precision in the QCD coupling
constant. The resulting expressions are implemented in the public code
RESUMMINO and can be directly used in the corresponding experimental searches.Comment: 5 pages, 4 figures. Proceedings of the EPS Conference on High-Energy
Physics (EPS-HEP 2017), Venice, Ital
Of Donor Coordination, Free-Riding, Darlings, and Orphans: The dependence of bilateral aid commitments on other bilateral giving
Using data from 1988 to 2007, we examine to what extent bilateral aid flows of an individual donor to a country depend on aid flows from all other bilateral and multilateral donors to that country. We thereby want to assess to what extent donor coordination, free-riding, selectivity, and common donor motivations drive bilateral aid allocation as these determinants would point to different dependence structures. Using approaches from spatial econometrics and controlling for endogeneity using an GMM framework, we find that other bilateral flows lead to a significant (but rather small) increase in aid flows from a particular donor. The effects are particularly pronounced for so-called donor 'orphans' who seem to be collectively shunned by bilateral aid donors. This suggests that donor coordination and free-riding are quantitatively less important than common donor interests and selectivity. --
Squark and Gaugino Hadroproduction and Decays in Non-Minimal Flavour Violating Supersymmetry
We present an extensive analysis of squark and gaugino hadroproduction and
decays in non-minimal flavour violating supersymmetry. We employ the so-called
super-CKM basis to define the possible misalignment of quark and squark
rotations, and we use generalized (possibly complex) charges to define the
mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for
all squark-(anti-)squark/gaugino pair and squark-gaugino associated production
processes as well as their decay widths are then given in compact analytic
form. For four different constrained supersymmetry breaking models with
non-minimal flavour violation in the second/third generation squark sector
only, we establish the parameter space regions allowed/favoured by low-energy,
electroweak precision, and cosmological constraints and display the chirality
and flavour decomposition of all up- and down-type squark mass eigenstates.
Finally, we compute numerically the dependence of a representative sample of
production cross sections at the LHC on the off-diagonal mass matrix elements
in the experimentally allowed/favoured ranges.Comment: 35 pages, 29 (partly colour) figures. Some typos corrected, wording
of several paragraphs improved, version accepted by Nucl. Phys.
Detailed Comparison of Next-to-Leading Order Predictions for Jet Photoproduction at HERA
The precision of new HERA data on jet photoproduction opens up the
possibility to discriminate between different models of the photon structure.
This requires equally precise theoretical predictions from perturbative QCD
calculations. In the past years, next-to-leading order calculations for the
photoproduction of jets at HERA have become available. Using the kinematic cuts
of recent ZEUS analyses, we compare the predictions of three calculations for
different dijet and three-jet distributions. We find that in general all three
calculations agree within the statistical accuracy of the Monte Carlo
integration yielding reliable theoretical predictions. In certain restricted
regions of phase space, the calculations differ by up to 5%.Comment: 10 pages, 7 eps-figures. To appear in the Proceedings of the Workshop
on ``Monte Carlo Generators for HERA Physics'', Hamburg 1998/9
Evidence for Factorization Breaking in Diffractive Low-Q^2 Dijet Production
We calculate diffractive dijet production in deep-inelastic scattering at
next-to-leading order of perturbative QCD, including contributions from direct
and resolved photons, and compare our predictions to preliminary data from the
H1 collaboration at HERA. In contrast to recent experimental claims, evidence
for factorization breaking is found only for resolved, and not direct, photon
contributions. No evidence is found for large normalization uncertainties in
diffractive parton densities. The results confirm theoretical expectations for
the (non-)cancellation of soft singularities in diffractive scattering as well
as previous results for (almost) real photoproduction.Comment: 4 pages, 3 figure
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