6 research outputs found
The Flavor of QCD Axion Dark Matter
We argue that demanding a consistent cosmological history, including the
absence of domain walls and strongly interacting relics at the Peccei-Quinn
scale, singles out two concrete realizations of hadronic QCD axions as viable
dark matter models. These realizations generally feature flavor-violating axion
couplings to Standard Model quarks that are unsuppressed at low energies. As a
consequence, experiments looking for flavor-violating hadronic processes
involving the axion can be sensitive probes of QCD axion dark matter models. In
particular, we show that the NA62 and KOTO experiments could detect the
decay for axions consistent with the observed dark matter
abundance via the post-inflationary misalignment mechanism.Comment: 11 pages, 4 figure
Nonabelian Kinetic Mixing in a Confining Phase
Dark matter from a hidden sector with SU() gauge symmetry can have a
nonabelian kinetic mixing portal with the standard model. The dark photon
becomes massive in the confining phase without the need for spontaneous
symmetry breaking. Depending on the particle content of the dark sector, there
can be two or more composite vectors that get kinetic mixing through a heavy
mediator particle . This provides a model of composite dark photons giving a
portal for direct detection of dark baryons. Avoiding exotic charged relics
requires additional couplings allowing to decay to dark quarks and standard
model fields, leading to further portals between the dark matter and the
standard model. We comprehensively study the constraints on such models from
colliders, rare decays, direct detection, and big bang nucleosynthesis.Comment: 14 pages, 12 figures, comments welcom
Nonabelian kinetic mixing in a confining phase: a framework for composite dark photons
Abstract Dark matter from a hidden sector with SU(N) gauge symmetry can have a nonabelian kinetic mixing portal with the standard model. The dark photon becomes massive in the confining phase without the need for spontaneous symmetry breaking. Depending on the particle content of the dark sector, there can be two or more composite vectors that get kinetic mixing through a heavy mediator particle X. This provides a model of composite dark photons giving a portal for direct detection of dark baryons. Avoiding exotic charged relics requires additional couplings allowing X to decay to dark quarks and standard model fields, leading to further portals between the dark matter and the standard model. We comprehensively study the constraints on such models from colliders, rare decays, direct detection, and big bang nucleosynthesis
High Stability LED-Pumped Nd:YVO<sub>4</sub> Laser with a Cr:YAG for Passive Q-Switching
With improvements in light-emitting diode (LED) performance and a sharp decline in price, a light source with the irradiance of a laser and the cost of an LED is worthy of further study. We demonstrated a LED-pumped Nd:YVO4 laser in quasi-continuous-wave (QCW) and passively Q-switched (PQS) regime. With an incident pump energy of 6.28 mJ (150 μs pulses at 1 Hz), the Nd:YVO4 laser has an energy of 206 μJ at 1064 nm in the QCW regime. The optical conversion efficiency of the system is 4.1%, and the slope efficiency is 9.0%. A pulsed energy of 2.5 μJ was obtained with a duration of 897 ns (FWHM) in the PQS regime, which means the peak power is 2.79 W. The output energy stability is 97.54%