Dark matter interactions from an extra U(1)gauge symmetry with kinetic mixing and Higgs charge

We investigate fermionic dark matter interactions with standard model particles from an additional U(1)X gauge symmetry,assuming kinetic mixing between the U(1)X and U(1)Y gauge fields as well as a nonzero U(1)X charge of the Higgs doublet.To ensure gauge-invariant Yukawa interactions and the cancellation of gauge anomalies,standard model fermions are assigned Y-sequential U(1)X charges proportional to the Higgs charge.Although the Higgs charge should be small owing to collider constraints,it is useful to decrease the effective cross section of dark matter scattering off nucleons by two orders of magnitude to easily evade direct detection bounds.After performing numerical scans in the parameter space,we find that the introduction of the Higgs charge can also enhance the dark matter relic density by at least two orders of magnitude.In the case where the resonance effect is important for dark matter freeze-out,when the observed relic density and direct detection constraints are tangled,the Higgs charge can expand physical windows to some extent by relieving the tension between the relic density and direct detection.

Searches for multi-Z boson productions and anomalous gauge boson couplings at a muon collider

Multi-boson productions can be exploited as novel probes either for standard model precision tests or new physics searches,and have become a popular research topic in ongoing LHC experiments and future collider studies,including those for electron–positron and muon–muon colliders.In this study,we focus on two examples,i.e.,ZZZ direct productions through μ^(+)μ^(-) annihilation at a 1TeV muon collider,and ZZ productions through vector boson scattering(VBS)at a 10TeV muon collider,with an integrated luminosity of 10 ab^(-1).Various channels are considered,including ZZZ→4l2v and ZZZ→4l+2jets.The expected significance on these multi-Z boson production processes is reported based on a detailed Monte Carlo study and signal background analysis.Sensitivities on anomalous gauge boson couplings are also presented.

Translation gauge field theory of gravity in Minkowski spacetime

The gravitational field h_(μν)with spin-2 is introduced naturally by the requirement that the Lagrangian is locally translation invariant in Minkowski spacetime.The interactions between the h_(μν)and spin-1/2,0,1 matter fields are obtained along with the Lagrangian for the gravitational field including self-interactions.The deflection angle of light when it passes through the sun is calculated with different gauge conditions as an example.Our leading-order result is the same as that from general relativity,although the basic ideas are different.It is interesting that gravity can be described in a similar way to other fundamental interactions in Minkowski spacetime,and it may provide a new scenario for the Universe.

Spontaneous decoherence of coupled harmonic oscillators confined in a ring

We study the spontaneous decoherence of coupled harmonic oscillators confined in a ring container, where the nearest-neighbor harmonic potentials are taken into consideration. Without any external symmetry-breaking field or surrounding environment, the quantum superposition state prepared in the relative degrees of freedom gradually loses its quantum coherence spontaneously.This spontaneous decoherence is interpreted by the gauge couplings between the center-of-mass and the relative degrees of freedoms, which actually originate from the symmetries of the ring geometry and the corresponding nontrivial boundary conditions.In particular, such spontaneous decoherence does not occur at all at the thermodynamic limit because the nontrivial boundary conditions become the trivial Born-von Karman boundary conditions when the perimeter of the ring container tends to infinity.Our investigation shows that a thermal macroscopic object with certain symmetries has a chance for its quantum properties to degrade even without applying an external symmetry-breaking field or surrounding environment.