39 research outputs found
Probing the Dark Sector through Mono-Z Boson Leptonic Decays
Collider search for dark matter production has been performed over the years
based on high pT standard model signatures balanced by large missing transverse
energy. The mono-Z boson production with leptonic decay has a clean signature
with the advantage that the decaying electrons and muons can be precisely
measured. This signature not only enables reconstruction of the Z boson rest
frame, but also makes possible recovery of the underlying production dynamics
through the decaying lepton angular distribution. In this work, we exploit full
information carried by the leptonic Z boson decays to set limits on coupling
strength parameters of the dark sector. We study simplified dark sector models
with scalar, vector, and tensor mediators and observe among them different
signatures in the distribution of angular coefficients.Specifically, we show
that angular coefficients can be used to distinguish different scenarios of the
spin-0 and spin-1 models, including the ones with parity-odd and charge
conjugation parity-odd operators. To maximize the statistical power, we perform
a matrix element method study with a dynamic construction of event likelihood
function. We parametrize the test statistic such that sensitivity from the
matrix element is quantified through a term measuring the shape difference. Our
results show that the shape differences provide significant improvements in the
limits, especially for the scalar mediator models. We also present an example
application of a matrix-element-kinematic-discriminator, an easier approach
that is applicable for experimental data.Comment: 26 pages, 16 figure
Direct detection of freeze-in inelastic dark matter
We show that the current sensitivities of direct detection experiments have
already reached the interesting parameter space of freeze-in dark matter models
if the dark sector is in the inelastic dark matter framework and the excited
dark matter state is cosmologically stable. Using results recently presented by
the XENON1T experiment, we present constraints on these models. We also show
that these models can explain the reported excess in the electron recoil
signals if the mass gap between the ground state and the excited state is at
keV scale.Comment: 7 pages, 7 figure
The CERN LHC Sensitivity on measuring WZGamma Production and Anomalous WWZGamma Coupling
In this paper we present for the first time a detailed Monte Carlo study of
measuring WZGamma production with pure leptonic decays and probing anomalous
quartic gauge-boson WWZGamma couplings at the sqrt(s) = 14 TeV LHC, with parton
shower and detector simulation effects taken into account. We find that with an
integrated luminosity of 100 fb-1 and proper selection cuts, the Standard Model
WZGamma signal significance can be improved to as much as 3 sigma. After
reviewing previous parametrization on anomalous WWZGamma couplings (see
e.g.an/Lambda^2 or k2m/Lambda^2 as shown in Ref. [17]), we propose a more
general parametrization scheme with 4 free inputs leading only to genuine
WWZGamma aQGC couplings. Finally, our numerical results show that one can reach
constraints at 95% confidence level of -5.7 * 10^{-5} GeV^{-2} < k2m/Lambda^2 <
5.5 * 10^{-5} GeV^{-2} and -2.2 x 10^{-5} GeV^{-2} < an/Lambda^2 < 2.4 *
10^{-5} GeV^{-2}, which are more stringent than LEP's results by three orders
of magnitude.Comment: 15 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1211.164
Probing Triple-W Production and Anomalous WWWW Coupling at the CERN LHC and future 100TeV proton-proton collider
Triple gauge boson production at the LHC can be used to test the robustness
of the Standard Model and provide useful information for VBF di-boson
scattering measurement. Especially, any derivations from SM prediction will
indicate possible new physics. In this paper we present a detailed Monte Carlo
study on measuring WWW production in pure leptonic and semileptonic decays, and
probing anomalous quartic gauge WWWW couplings at the CERN LHC and future
hadron collider, with parton shower and detector simulation effects taken into
account. Apart from cut-based method, multivariate boosted decision tree method
has been exploited for possible improvement. For the leptonic decay channel,
our results show that at the sqrt{s}=8(14)[100] TeV pp collider with integrated
luminosity of 20(100)[3000] fb-1, one can reach a significance of
0.4(1.2)[10]sigma to observe the SM WWW production. For the semileptonic decay
channel, one can have 0.5(2)[14]sigma to observe the SM WWW production. We also
give constraints on relevant Dim-8 anomalous WWWW coupling parameters.Comment: Accepted version by JHE
The impact of baryonic potentials on the gravothermal evolution of self-interacting dark matter haloes
The presence of a central baryonic potential can have a significant impact on
the gravothermal evolution of self-interacting dark matter (SIDM) haloes. We
extend a semi-analytical fluid model to incorporate the influence of a static
baryonic potential and calibrate it using controlled N-body simulations. We
construct benchmark scenarios with varying baryon concentrations and different
SIDM models, including constant and velocity-dependent self-interacting cross
sections. The presence of the baryonic potential induces changes in SIDM halo
properties, including central density, core size, and velocity dispersion, and
it accelerates the halo's evolution in both expansion and collapse phases.
Furthermore, we observe a quasi-universality in the gravothermal evolution of
SIDM haloes with the baryonic potential, resembling a previously known feature
in the absence of the baryons. By appropriately rescaling the physical
quantities that characterize the SIDM haloes, the evolution of all our
benchmark cases exhibits remarkable similarity. Our findings offer a framework
for testing SIDM predictions using observations of galactic systems where
baryons play a significant dynamical role.Comment: 9 pages + references + appendices, 10 figures, 3 tables; v3: as
published in MNRA
Strong Dark Matter Self-interactions Diversify Halo Populations Within and Surrounding the Milky Way
We perform a high-resolution cosmological zoom-in simulation of a Milky Way
(MW)-like system, which includes a realistic Large Magellanic Cloud analog,
using a large differential elastic dark matter self-interaction cross section
that reaches at relative
velocities of , motivated by observational
features of dwarf galaxies within and surrounding the MW. We explore the
effects of dark matter self-interactions on satellite, splashback, and isolated
halos through their abundance, central densities, maximum circular velocities,
orbital parameters, and correlations between these variables. We use an
effective constant cross section model to analytically predict the stages of
our simulated halos' gravothermal evolution, demonstrating that deviations from
the collisionless -- relation can be used to select
deeply core-collapsed halos, where is a halo's maximum circular
velocity and is the radius at which it occurs. We predict that a
sizable fraction () of subhalos with masses down to are deeply core-collapsed in our SIDM model. Core-collapsed
systems form of the total isolated halo population down to the
same mass; these isolated, core-collapsed halos would host faint dwarf galaxies
in the field with extremely steep central density profiles reminiscent of the
Tucana dwarf galaxy. Finally, most halos with masses above are core-forming in our simulation. Our study thus demonstrates
how self-interactions diversify halo populations in an
environmentally-dependent fashion within and surrounding MW-mass hosts,
providing a compelling avenue to address the diverse dark matter distributions
of observed dwarf galaxies.Comment: 28 pages, 17 figure