Phenomenology of CP-even ALP

Abstract

Axion or axion-like particle (ALP) has been usually considered as a CP-odd Nambu-Goldstone boson (NGB) from the spontaneous breakdown of a global U(1) symmetry. In this paper, we point out that the NGB behaves as a CP-even particle coupled to the SM particles in a large class of simple (or perhaps the simplest) renormalizable models. We provide a first study of the collider phenomenology and cosmology of the CP-even ALP. In a natural parameter region, the CP-even ALP can be produced from the Higgs boson decay in colliders. When the mass is not very light, the signals will be Higgs exotic decays, Higgs decay to displaced vertex ×2, Higgs decay to displaced vertex + missing energy. The signal can be discriminated from other models, e.g. hidden photon, by measuring the decay length and the decay products of the light new particle. In addition, when m a MeV, in which case the Higgs boson invisible decay may be probed in the colliders, the CP-even ALP is a nice Dark matter (DM) candidate. The DM can be probed by 21cm line measurement, the future measurement of the Milky way mass halo function in the Vera Rubin Observatory, as well as X-or γ-ray observations. The DM production mechanisms are discussed.

Dedicated Triggers for Displaced Jets using Timing Information from Electromagnetic Calorimeter at HL-LHC

“…Several phenomenological studies explore the possibilities of LLP searches covering a wide range of models and signatures, such as those in Refs. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Collaborations of two major general purpose detectors at LHC, CMS and ATLAS, have also been actively performing several BSM studies involving various LLP signatures.…”

Singlet extensions and W boson mass in the light of the CDF II result

“…to be dark matter, we need to suppress the CP violation of the explicit breaking of U (1) or the mixing between the dark gauge boson with the photon [47], since otherwise a is not long-lived enough to be dark matter. 6 Due to the additional contribution, it corresponds to n = 3 but not −1.…”

“…Therefore we need to consider the low-reheating temperature for it being the cold dark matter with m a 20 keV e.g. [47].…”

“…In the numerical estimation, we take account of the branching fraction of the Higgs boson to b b 4. A slight modification of the model has been studied in the context of axion/dark photon dark matter production via the phase transition[46], the UV model of a CP-even ALP[47], WIMP[48- 50][36, 51-54], electroweak baryogenesis[37,48] and collider physics[36,38,47,53,55,56] 5. If the axion potential has a non-trivial domain wall number, it may cause a serious domain wall problem.…”