50,362 research outputs found

### Simplified dark matter models in the light of AMS-02 antiproton data

In this work we perform an analysis of the recent AMS-02 antiproton flux and
the antiproton-to-proton ratio in the framework of simplified dark matter
models. To predict the AMS-02 observables we adopt the propagation and
injection parameters determined by the observed fluxes of nuclei. We assume
that the dark matter particle is a Dirac fermionic dark matter, with
leptophobic pseudoscalar or axialvector mediator that couples only to Standard
Model quarks and dark matter particles. We find that the AMS-02 observations
are consistent with the dark matter hypothesis within the uncertainties. The
antiproton data prefer a dark matter (mediator) mass in the 700 GeV--5 TeV
region for the annihilation with pseudoscalar mediator and greater than 700 GeV
(200 GeV--1 TeV) for the annihilation with axialvector mediator, respectively,
at about 68% confidence level. The AMS-02 data require an effective dark matter
annihilation cross section in the region of 1x10^{-25} -- 1x10^{-24}
(1x10^{-25} -- 4x10^{-24}) cm^3/s for the simplified model with pseudoscalar
(axialvector) mediator. The constraints from the LHC and Fermi-LAT are also
discussed.Comment: 16 pages, 6 figures, 1 table. arXiv admin note: text overlap with
arXiv:1509.0221

### Decoupling MSSM Higgs Sector and Heavy Higgs Decay

The decoupling limit in the MSSM Higgs sector is the most likely scenario in
light of the Higgs discovery. This scenario is further constrained by MSSM
Higgs search bounds and flavor observables. We perform a comprehensive scan of
MSSM parameters and update the constraints on the decoupling MSSM Higgs sector
in terms of 8 TeV LHC data. We highlight the effect of light SUSY spectrum in
the heavy neutral Higgs decay in the decoupling limit. We find that the
chargino and neutralino decay mode can reach at most 40% and 20% branching
ratio, respectively. In particular, the invisible decay mode BR(H^0(A^0) ->
\tilde{\chi}^0_1\tilde{\chi}^0_1) increases with increasing Bino LSP mass and
is between 10%-15% (20%) for 30<m_{\tilde{\chi}^0_1}<100 GeV. The leading
branching fraction of heavy Higgses decay into sfermions can be as large as 80%
for H^0 -> \tilde{t}_1\tilde{t}_1^\ast and 60% for H^0/A^0 ->
\tilde{\tau}_1\tilde{\tau}_2^\ast+\tilde{\tau}_1^\ast\tilde{\tau}_2. The
branching fractions are less than 10% for H^0 -> h^0h^0 and 1% for A^0 -> h^0Z
for m_A>400 GeV. The charged Higgs decays to neutralino plus chargino and
sfermions with branching ratio as large as 40% and 60%, respectively. Moreover,
the exclusion limit of leading MSSM Higgs search channel, namely gg,b\bar{b} ->
H^0, A^0 -> tau^+ tau^-, is extrapolated to 14 TeV LHC with high luminosities.
It turns out that the tau tau mode can essentially exclude regime with
tan\beta>20 for L=300 fb^{-1} and tan\beta>15 for L=3000 fb^{-1}.Comment: 20 pages, 14 figure

### Revisiting simplified dark matter models in terms of AMS-02 and Fermi-LAT

We perform an analysis of the simplified dark matter models in the light of
cosmic ray observables by AMS-02 and Fermi-LAT. We assume fermion, scalar or
vector dark matter particle with a leptophobic spin-0 mediator that couples
only to Standard Model quarks and dark matter via scalar and/or pseudo-scalar
bilinear. The propagation and injection parameters of cosmic rays are
determined by the observed fluxes of nuclei from AMS-02. We find that the
AMS-02 observations are consistent with the dark matter framework within the
uncertainties. The AMS-02 antiproton data prefer 30 (50) GeV - 5 TeV dark
matter mass and require an effective annihilation cross section in the region
of 4x10^{-27} (7x10^{-27}) - 4x10^{-24} cm^3/s for the simplified fermion
(scalar and vector) dark matter models. The cross sections below 2x10^{-26}
cm^3/s can evade the constraint from Fermi-LAT dwarf galaxies for about 100 GeV
dark matter mass.Comment: 20 pages, 8 figures, 2 tables. arXiv admin note: text overlap with
arXiv:1612.0950

### Type II Seesaw and tau lepton at the HL-LHC, HE-LHC and FCC-hh

The tau lepton plays important role in distinguishing neutrino mass patterns
and determining the chirality nature in heavy scalar mediated neutrino mass
models, in the light of the neutrino oscillation experiments and its
polarization measurement. We investigate the lepton flavor signatures with tau
lepton at LHC upgrades, i.e. HL-LHC, HE-LHC and FCC-hh, through leptonic
processes from doubly charged Higgs in the Type II Seesaw. We find that for the
channel with one tau lepton in final states, the accessible doubly charged
Higgs mass at HL-LHC can reach 655 GeV and 695 GeV for the neutrino mass
patterns of normal hierarchy (NH) and inverted hierarchy (IH) respectively,
with the luminosity of 3000 fb$^{-1}$. Higher masses, 975-1930 GeV for NH and
1035-2070 GeV for IH, can be achieved at HE-LHC and FCC-hh.Comment: 18 pages, 9 figures, 4 table

### Gradient Hard Thresholding Pursuit for Sparsity-Constrained Optimization

Hard Thresholding Pursuit (HTP) is an iterative greedy selection procedure
for finding sparse solutions of underdetermined linear systems. This method has
been shown to have strong theoretical guarantee and impressive numerical
performance. In this paper, we generalize HTP from compressive sensing to a
generic problem setup of sparsity-constrained convex optimization. The proposed
algorithm iterates between a standard gradient descent step and a hard
thresholding step with or without debiasing. We prove that our method enjoys
the strong guarantees analogous to HTP in terms of rate of convergence and
parameter estimation accuracy. Numerical evidences show that our method is
superior to the state-of-the-art greedy selection methods in sparse logistic
regression and sparse precision matrix estimation tasks

### Simulation based selection of competing structural econometric models

This paper proposes a formal model selection test for choosing between two competing structural econometric models. The procedure is based on a novel lack-of-fit criterion, namely, the simulated mean squared error of predictions (SMSEP), taking into account the complexity of structural econometric models. It is asymptotically valid for any fixed number of simulations, and allows for any estimator which has a vn asymptotic normality or is superconsistent with a rate at n. The test is bi-directional and applicable to non-nested models which are both possibly misspecified. The asymptotic distribution of the test statistic is derived. The proposed test is general regardless of whether the optimization criteria for estimation of competing models are the same as the SMSEP criterion used for model selection. An empirical application using timber auction data from Oregon is used to illustrate the usefulness and generality of the proposed testing procedure.Lack-of-fit, Model selection tests, Non-nested models, Simulated mean squared error of predictions

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