Implications of nano-Hertz gravitational waves on electroweak phase transition in the singlet dark matter model.

Inspired by the recent evidences of nano-Hertz stochastic gravitational waves observed by the pulsar timing array collaborations, we explore their implied supercooled electroweak phase transition in the singlet extension of the standard model. Our findings reveal that by adjusting the model parameter at per milli level, the corresponding percolation temperature can be continuously lowered to 1 GeV. With such a low percolation temperature, the singlet dark matter may freeze out before the electroweak phase transition, and, consequently, the entropy generated during the transition can significantly affect the dark matter relic density.

Low energy SUSY confronted with new measurements of W-boson mass and muon g-2.

The new CDF II measurement of W-boson mass shows a 7σ deviation from the standard model (SM) prediction, while the recent FNAL measurement of the muon g-2 shows a 4.2σ deviation (combined with the BNL result) from the SM. Both of them strongly indicate new physics beyond the SM.

Can the minimal supersymmetric standard model with light bottom squark and light gluino survive Z-peak constraints?

In the framework of the minimal supersymmetric model we examine the Z-peak constraints on the scenario of one light bottom squark (sbottom) ( approximately 2-5.5 GeV) and light gluino (approximately 12-16 GeV), which has been successfully used to explain the excess of bottom quark production in hadron collisions. Such a scenario is found to be severely constrained by the CERN LEP Z-peak observables, especially by R(b), due to the large effect of gluino-sbottom loops.