Helmut Eberl

A bstract: In this work we explore the possibility of new light fermionic particles with millicharge or electromagnetic form factor interactions and their underground production via an electron beam in the 100 MeV range and their subsequent detection using a CCD-sensor. We evaluate the S-matrix elements and the phase spaces for production analytically, and then calculate the corresponding cross sections numerically. For millicharged fermions this set-up could be able to probe a window in parameter space, yet unconstrained by direct detection experiments. The electric or magnetic dipole moment of a light fermion could feasibly be probed with enough beam time or an increased beam energy.

We study the C P -even neutral Higgs boson decays h 0 → c c ¯ , b b ¯ , b s ¯ , γ γ , g g in the minimal supersymmetric standard model (MSSM) with a general quark flavor violation (QFV) due to squark generation mixings, identifying the h 0 as the Higgs boson with a mass of 125 GeV. We compute the widths of the h 0 decays to c c ¯ , b b ¯ , b s ¯ at the full one-loop level. For the h 0 decays to γ γ and g g , we compute the widths at NLO QCD level. , we perform a systematic MSSM parameter scan for these widths, respecting all the relevant theoretical and experimental constraints, such as those from B-meson data, and the 125 GeV Higgs boson data from recent LHC experiments, as well as the limits on supersymmetric (SUSY) particle (sparticle) masses from the LHC experiments. We also take into account the expected sparticle mass limits from the future HL-LHC experiment in our analysis. the usual studies in the MSSM with minimal flavor violation (MFV), we find that the deviations of these MSSM decay widths from the Standard Model (SM) values can be quite sizable and that there are significant correlations among these deviations. All of these sizable deviations in the h 0 decays are mainly due to large scharm-stop mixing and large sstrange-sbottom mixing. Such sizable deviations from the SM can be observed at high signal significance in future lepton colliders such as ILC, CLIC, CEPC, FCC-ee, and muon collider the failure of SUSY particle discovery at the HL-LHC. In case the deviation pattern shown here is really observed at the lepton colliders, then it would strongly suggest the discovery of QFV SUSY (the MSSM with general QFV).

We present a full one-loop calculation of the gravitino thermal production rate, beyond the so-called hard thermal loop approximation, using the corresponding thermal spectral functions in numerical form on both sides of the light cone. This framework requires a full numerical evaluation. We interpret our results within the framework of a general supergravity-based model, remaining agnostic about the specifics of supersymmetry breaking. In this context, assuming that gravitinos constitute the entirety of the dark matter in the Universe imposes strict constraints on the reheating temperature. For example, with a gluino mass at the current LHC limit, a maximum reheating temperature of T _reh ≃ 10⁹ GeV is compatible with a gravitino mass of m _3/2 ≃ 1 TeV. Additionally, with a reheating temperature an order of magnitude lower at T _reh ≃ 10⁸ GeV, the common gaugino mass M _1/2 can range from 2 to 4 TeV within the same gravitino mass range. For much higher values of M _1/2, which are favored by current accelerator and cosmological data in the context of supersymmetric models, such as M _1/2 = 10 TeV, and for m _3/2 ≃ 1 TeV the reheating temperature compatible with the gravitino dark matter scenario is 10⁷ GeV. If other dark matter particles are considered, the reheating temperature could be much lower.

We calculate the gravitino production rate, computing its one-loop thermal self-energy. Gravitino production processes that do not result through thermal cuts of its self-energy, have been identified and taken into account. Correcting analytical errors and numerical approximations in the previous calculations, we present our result. This deviates from the latest estimation by almost 10%. More importantly, we provide a convenient formula, for calculating the gravitino production rate and its thermal abundance, as a function of the reheating temperature of the Universe.

We calculate the gravitino production rate, computing its one-loop thermal self-energy. Gravitino production processes that do not result through thermal cuts of its self-energy, have been identified and taken into account. Correcting analytical errors and numerical approximations in the previous calculations, we present our result. This deviates from the latest estimation by almost 10%. More importantly, we provide a convenient formula, for calculating the gravitino production rate and its thermal abundance, as a function of the reheating temperature of the Universe.