233 research outputs found
Leptophilic dark matter in gauged model in light of DAMPE cosmic ray excess
Motivated by the very recent cosmic-ray electron+positron excess observed by
DAMPE collaboration, we investigate a Dirac fermion dark matter (DM) in the
gauged model. DM interacts with the electron and muon via the
gauge boson . The model can explain the DAMPE data well.
Although a non-zero DM-nucleon cross section is only generated at one loop
level and there is a partial cancellation between and
couplings, we find that a large portion of mass is ruled out from
direct DM detection limit leaving the allowed mass to be close to two
times of the DM mass. Implications for and , and muon anomaly are also studied.Comment: Discussions added, version accepted by EPJ
Vacuum stability in stau-neutralino coannihilation in MSSM
The stau-neutralino coannihilation provides a feasible way to accommodate the
observed cosmological dark matter (DM) relic density in the minimal
supersymmetric standard model (MSSM). In such a coannihilation mechanism the
stau mass usually has an upper bound since its annihilation rate becomes small
with the increase of DM mass. Inspired by this observation, we examine the
upper limit of stau mass in the parameter space with a large mixing of staus.
We find that the stau pair may dominantly annihilate into dibosons and hence
the upper bound on the stau mass ( GeV) obtained from the
final states can be relaxed. Imposing the DM relic density constraint and
requiring a long lifetime of the present vacuum, we find that the lighter stau
mass can be as heavy as about 1.4 TeV for the stau maximum mixing. However, if
requiring the present vacuum to survive during the thermal history of the
universe, this mass limit will reduce to about 0.9 TeV. We also discuss the
complementarity of vacuum stability and direct detections in probing this stau
coannihilation scenario.Comment: 12 pages, 6 figure
A minimal extension of MSSM in light of the B decay anomaly
Motivated by the and anomalies from B decays, we extend the
minimal supersymmetric model with a non-universal anomaly-free
gauge symmetry, coupling non-universally to the lepton sector as well as the
quark sector. In particular, only the third generation quarks are charged under
this , which can easily evade the dilepton bound from the LHC
searches. An extra singlet is introduced to break this symmetry
allowing for the -term to be generated dynamically. The relevant
constraints of mixing, mixing and the LHC
dilepton searches are considered. We find that in the allowed parameter space
this gauge interaction can accommodate the and
anomalies and weaken considerably the mass limits while remaining
perturbative up to the Planck scale.Comment: 12 pages,2 figure
Probing GeV-scale MSSM neutralino dark matter in collider and direct detection experiments
Given the recent constraints from the dark matter (DM) direct detections, we
examine a light GeV-scale (2-30 GeV) neutralino DM in the alignment limit of
the Minimal Supersymmetric Standard Model (MSSM). In this limit without
decoupling, the heavy CP-even scalar plays the role of the Standard Model
(SM) Higgs boson while the other scalar can be rather light so that the DM
can annihilate through the resonance or into a pair of to achieve the
observed relic density. With the current collider and cosmological constraints,
we find that such a light neutralino DM above 6 GeV can be excluded by the
XENON-1T (2017) limits while the survivied parameter space below 6 GeV can be
fully covered by the future germanium-based light dark matter detections (such
as CDEX), by the Higgs coupling precison measurements or by the production
process at an electron-positron collider (Higgs factory).Comment: 15 pages, 5 figures. Discussions and references added, version
accepted by PL
Narrow line width frequency comb source based on an injection-locked III–V-on-silicon mode-locked laser
In this paper, we report the optical injection locking of an L-band (similar to 1580 nm) 4.7 GHz III-V-on-silicon mode-locked laser with a narrow line width continuous wave (CW) source. This technique allows us to reduce the MHz optical line width of the mode-locked laser longitudinal modes down to the line width of the source used for injection locking, 50 kHz. We show that more than 50 laser lines generated by the mode-locked laser are coherent with the narrow line width CW source. Two locking techniques are explored. In a first approach a hybrid mode-locked laser is injection-locked with a CW source. In a second approach, light from a modulated CW source is injected in a passively mode-locked laser cavity. The realization of such a frequency comb on a chip enables transceivers for high spectral efficiency optical communication. (C) 2016 Optical Society of Americ
Simplified TeV leptophilic dark matter in light of DAMPE data
Using a simplified framework, we attempt to explain the recent DAMPE cosmic
flux excess by leptophilic Dirac fermion dark matter (LDM). The
scalar () and vector () mediator fields connecting LDM and
Standard Model particles are discussed. Under constraints of DM relic density,
gamma-rays, cosmic-rays and Cosmic Microwave Background (CMB), we find that the
couplings , , and can
produce the right bump in flux for a DM mass around 1.5 TeV with a
natural thermal annihilation cross-section today. Among them, coupling is tightly constrained by
PandaX-II data (although LDM-nucleus scattering appears at one-loop level) and
the surviving samples appear in the resonant region, . We also study the related collider signatures, such as dilepton
production , and muon anomaly. Finally,
we present a possible realization for such leptophilic dark matter.Comment: discussions added, version accepted by JHE
Propriété en modulation de laser Fabry-Perot verrouillé en longueur d'onde par injection optique
Session affiches 11 « Amplificateurs et Lasers à semi-conducteurs » [A2.1]National audienceUn laser Fabry-Perot fonctionnant en régime monomode grâce au verrouillage en longueur d'onde par injection optique est caractérisé sous modulation directe. Nous démontrons expérimentalement la dépendance de la réponse en régime petit signal et du facteur de couplage phase-amplitude en fonction de la puissance optique injectée
28 Gb/s direct modulation heterogeneously integrated C-band InP/SOI DFB laser
We demonstrate direct modulation of a heterogeneously integrated C-band DFB laser on SOI at 28 Gb/s with a 2 dB extinction ratio. This is the highest direct modulation bitrate so far reported for a membrane laser coupled to an SOI waveguide. The laser operates single mode with 6 mW output power at 100 mA bias current. The 3 dB modulation bandwidth is 15 GHz. Transmission experiments using a 2 km non zero dispersion shifted single mode fiber were performed at 28 Gb/s bitrate using a 2(7)-1 NRZ-PRBS pattern resulting in a 1 dB power penalty. (C) 2015 Optical Society of Americ
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