2,249 research outputs found
What next for the CMSSM and the NUHM: Improved prospects for superpartner and dark matter detection
We present an updated analysis of the CMSSM and the NUHM using the latest
experimental data and numerical tools. We map out favored regions of Bayesian
posterior probability in light of data from the LHC, flavor observables, the
relic density and dark matter searches. We present some updated features with
respect to our previous analyses: we include the effects of corrections to the
light Higgs mass beyond the 2-loop order using FeynHiggs v2.10.0; we include in
the likelihood the latest limits from direct searches for squarks and gluinos
at ATLAS with ~20/fb; the latest constraints on the spin-independent scattering
cross section of the neutralino from LUX are applied taking into account
uncertainties in the nuclear form factors. We find that in the CMSSM the
posterior distribution now tends to favor smaller values of Msusy than in the
previous analyses. As a consequence, the statistical weight of the A-resonance
region increases to about 30% of the total probability, with interesting new
prospects for the 14 TeV run at the LHC. The most favored region, on the other
hand, still features multi-TeV squarks and gluinos, and ~1TeV higgsino dark
matter whose detection prospects by current and one-tonne detectors look very
promising. The same region is predominant in the NUHM, although the A-resonance
region is also present there as well as a new solution, of neutralino-stau
coannihilation through the channel stau stau -> hh at very large \mu. We derive
the expected sensitivity of the future CTA experiment to ~1 TeV higgsino dark
matter for both models and show that the prospects for probing both models are
realistically good. We comment on the complementarity of this search to planned
direct detection one-tonne experiments.Comment: 37 pages, 15 figures. Appendix added showing the future constraints
on the CMSSM, including an updated calculation of the sensitivity of CTA
presented in arXiv:1411.521
Cumulant mapping as the basis of multi-dimensional spectrometry
Cumulant mapping employs a statistical reconstruction of the whole by
sampling its parts. The theory developed in this work formalises and extends ad
hoc methods of `multi-fold' or `multi-dimensional' covariance mapping. Explicit
formulae have been derived for the expected values of up to the 6th cumulant
and the variance has been calculated for up to the 4th cumulant. A method of
extending these formulae to higher cumulants has been described. The formulae
take into account reduced fragment detection efficiency and a background from
uncorrelated events. Number of samples needed for suppressing the statistical
noise to a required level can be estimated using a Matlab code included in
Supplemental Material. The theory can be used to assess the experimental
feasibility of studying molecular fragmentations induced by femtosecond or
x-ray free-electron lasers. It is also relevant for extending the conventional
mass spectrometry of biomolecules to multiple dimensions.Comment: 13 pages + Popular summary, 6 figure
Blind Spots for Direct Detection with Simplified DM Models and the LHC
Using the existing simplified model framework, we build several dark matter
models which have suppressed spin-independent scattering cross section. We show
that the scattering cross section can vanish due to interference effects with
models obtained by simple combinations of simplified models. For weakly
interacting massive particle (WIMP) masses 10 GeV, collider limits are
usually much weaker than the direct detection limits coming from LUX or
XENON100. However, for our model combinations, LHC analyses are more
competitive for some parts of the parameter space. The regions with direct
detection blind spots can be strongly constrained from the complementary use of
several Large Hadron Collider (LHC) searches like mono-jet, jets + missing
transverse energy, heavy vector resonance searches, etc. We evaluate the
strongest limits for combinations of scalar + vector, "squark" + vector, and
scalar + "squark" mediator, and present the LHC 14 TeV projections.Comment: 9 Pages, Talk presented at the conference "Varying Constants and
Fundamental Cosmology - VARCOSMOFUN'16" (Szczecin, Poland), Published in
Universe (proceedings of VARCOSMOFUN'16
Bayesian Implications of Current LHC Supersymmetry and Dark Matter Detection Searches for the Constrained MSSM
We investigate the impact of recent limits from LHC searches for
supersymmetry and from direct and indirect searches for dark matter on global
Bayesian inferences of the parameter space of the Constrained Minimal
Supersymmetric Standard Model (CMSSM). In particular we apply recent exclusion
limits from the CMS \alpha_T analysis of 1.1/fb of integrated luminosity, the
current direct detection dark matter limit from XENON100, as well as recent
experimental constraints on \gamma-ray fluxes from dwarf spheroidal satellite
galaxies of the Milky Way from the FermiLAT telescope, in addition to updating
values for other non-LHC experimental constraints. We extend the range of
scanned parameters to include a significant fraction of the focus
point/hyperbolic branch region. While we confirm earlier conclusions that at
present LHC limits provide the strongest constraints on the model's parameters,
we also find that when the uncertainties are not treated in an excessively
conservative way, the new bounds from dwarf spheroidal have the power to
significantly constrain the focus point/hyperbolic branch region. Their effect
is then comparable, if not stronger, to that from XENON100. We further analyze
the effects of one-year projected sensitivities on the neutrino flux from the
Sun in the 86-string IceCube+DeepCore configuration at the South Pole. We show
that data on neutrinos from the Sun, expected for the next few months at
IceCube and DeepCore, have the potential to further constrain the same region
of parameter space independently of the LHC and can yield additional
investigating power for the model.Comment: 27 pages, 7 figures, version published in PR
Fuzzy sets predict flexural strength and density of silicon nitride ceramics
In this work, we utilize fuzzy sets theory to evaluate and make predictions of flexural strength and density of NASA 6Y silicon nitride ceramic. Processing variables of milling time, sintering time, and sintering nitrogen pressure are used as an input to the fuzzy system. Flexural strength and density are the output parameters of the system. Data from 273 Si3N4 modulus of rupture bars tested at room temperature and 135 bars tested at 1370 C are used in this study. Generalized mean operator and Hamming distance are utilized to build the fuzzy predictive model. The maximum test error for density does not exceed 3.3 percent, and for flexural strength 7.1 percent, as compared with the errors of 1.72 percent and 11.34 percent obtained by using neural networks, respectively. These results demonstrate that fuzzy sets theory can be incorporated into the process of designing materials, such as ceramics, especially for assessing more complex relationships between the processing variables and parameters, like strength, which are governed by randomness of manufacturing processes
Ge-substitutional defects and the r3xr3 <--> 3x3 transition in alpha--SnGe(111)
The structure and energetics of Ge substitutional defects on the
alpha-Sn/Ge(111) surface are analyzed using Density Functional Theory (DFT)
molecular dynamics (MD) simulations. An isolated Ge defect induces a very local
distortion of the 3x3 reconstruction, confined to a significant downwards
displacement (-0.31 A) at the defect site and a modest upward displacement
(0.05 A) of the three Sn nearest neighbours with partially occupied dangling
bonds. Dynamical fluctuations between the two degenerate ground states yield
the six-fold symmetry observed around a defect in the experiments at room
temperature. Defect-defect interactions are controlled by the energetics of the
deformation of the 3x3 structure: They are negligible for defects on the
honeycomb lattice and quite large for a third defect on the hexagonal lattice,
explaining the low temperature defect ordering.Comment: 4 pages, Revtex, 7 Encapsulated Postscript figures, uses epsf.sty.
Submitted to Phys. Rev. Let
Error representation of the time-marching DPG scheme
In this article, we introduce an error representation function to perform adaptivity in time of the recently developed time-marching Discontinuous Petrov–Galerkin (DPG) scheme. We first provide an analytical expression for the error that is the Riesz representation of the residual. Then, we approximate the error by enriching the test space in such a way that it contains the optimal test functions. The local error contributions can be efficiently computed by adding a few equations to the time-marching scheme. We analyze the quality of such approximation by constructing a Fortin operator and providing an a posteriori error estimate. The time-marching scheme proposed in this article provides an optimal solution along with a set of efficient and reliable local error contributions to perform adaptivity. We validate our method for both parabolic and hyperbolic problems
Ground state energy of the modified Nambu-Goto string
We calculate, using zeta function regularization method, semiclassical energy
of the Nambu-Goto string supplemented with the boundary, Gauss-Bonnet term in
the action and discuss the tachyonic ground state problem.Comment: 10 pages, LaTeX, 2 figure
Prospects for dark matter searches in the pMSSM
We investigate the prospects for detection of neutralino dark matter in the
19-parameter phenomenological MSSM (pMSSM). We explore very wide ranges of the
pMSSM parameters but pay particular attention to the higgsino-like neutralino
at the ~ 1 TeV scale, which has been shown to be a well motivated solution in
many constrained supersymmetric models, as well as to a wino-dominated solution
with the mass in the range of 2-3 TeV. After summarising the present bounds on
the parameter space from direct and indirect detection experiments, we focus on
prospects for detection of the Cherenkov Telescope Array (CTA). To this end, we
derive a realistic assessment of the sensitivity of CTA to photon fluxes from
dark matter annihilation by means of a binned likelihood analysis for the
Einasto and Navarro-Frenk-White halo profiles. We use the most up to date
instrument response functions and background simulation model provided by the
CTA Collaboration. We find that, with 500 hours of observation, under the
Einasto profile CTA is bound to exclude at the 95% C.L. almost all of the ~ 1
TeV higgsino region of the pMSSM, effectively closing the window for heavy
supersymmetric dark matter in many realistic models. CTA will be able to probe
the vast majority of cases corresponding to a spin-independent scattering cross
section below the reach of 1-tonne underground detector searches for dark
matter, in fact even well below the irreducible neutrino background for direct
detection. On the other hand, many points lying beyond the sensitivity of CTA
will be within the reach of 1-tonne detectors, and some within collider reach.
Altogether, CTA will provide a highly sensitive way of searching for dark
matter that will be partially overlapping and partially complementary with
1-tonne detector and collider searches, thus being instrumental to effectively
explore the nearly full parameter space of the pMSSM.Comment: 35 pages, 14 figures, minor corrections and citations added, version
to appear in JHE
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