The THDMa Revisited

The THDMa is a new physics model that extends the scalar sector of the Standard Model by an additional doublet as well as a pseudoscalar singlet and allows for mixing between all possible scalar states. In the gauge-eigenbasis, the additional pseudoscalar serves as a portal to the dark sector, with a priori any dark matter spins states. The option where dark matter is fermionic is currently one of the standard benchmarks for the experimental collaborations, and several searches at the LHC constrain the corresponding parameter space. However, most current studies constrain regions in parameter space by setting all but 2 of the 12 free parameters to fixed values. In this work, we performed a generic scan on this model, allowing all parameters to float. We applied all current theoretical and experimental constraints, including bounds from current searches, recent results from B-physics, in particular Bs→Xsγ, as well as bounds from astroparticle physics. We identify regions in the parameter space which are still allowed after these were applied and which might be interesting for an investigation of current and future collider machines.

Testing the $$R_{D^{(*)}}$$ anomaly at the LHeC

B-Physics anomalies have recently raised renewed interest in leptoquarks, predicted in several theoretical frameworks. Under simplifying but conservative assumptions, we show that the current limits from LHC searches together with the requirement to explain the observed value for $$R_{D^{(*)}}$$ R D ( ∗ ) constrain the $$R_2$$ R 2 leptoquark mass to be in the range of $$800 \le m_{R_2} \le 1000$$ 800 ≤ m R 2 ≤ 1000 GeV. We study the search for $$R_2$$ R 2 at the LHeC via its resonance in the $$b\tau $$ b τ final state by performing a cut-and-count analysis of the signal and the dominant Standard Model backgrounds. We find that the LHeC has an excellent discovery potential for the $$R_2$$ R 2 leptoquark even for couplings to the first generation as small as $${\mathcal {O}}(10^{-2})$$ O ( 10 - 2 ) .

Gluino-SUGRA scenarios in light of FNAL muon g – 2 anomaly

Gluino-SUGRA ($$ \overset{\sim }{g} $$ g ~ SUGRA), which is an economical extension of the predictive mSUGRA, adopts much heavier gluino mass parameter than other gauginos mass parameters and universal scalar mass parameter at the unification scale. It can elegantly reconcile the experimental results on the Higgs boson mass, the muon g − 2, the null results in search for supersymmetry at the LHC and the results from B-physics. In this work, we propose several new ways to generate large gaugino hierarchy (i.e. M3 » M1, M2) for $$ \overset{\sim }{g} $$ g ~ SUGRA model building and then discuss in detail the implications of the new muon g − 2 results with the updated LHC constraints on such $$ \overset{\sim }{g} $$ g ~ SUGRA scenarios. We obtain the following observations: (i) for the most interesting M1 = M2 case at the GUT scale with a viable bino-like dark matter, the $$ \overset{\sim }{g} $$ g ~ SUGRA can explain the muon g − 2 anomaly at 1σ level and be consistent with the updated LHC constraints for 6 ≤ M3/M1 ≤ 9 at the GUT scale; (ii) For M1 : M2 = 5 : 1 at the GUT scale with wino-like dark matter, the $$ \overset{\sim }{g} $$ g ~ SUGRA model can explain the muon g − 2 anomaly at 2σ level and be consistent with the updated LHC constraints for 3 ≤ M3/M1 ≤ 3.2 at the GUT scale; (iii) For M1 : M2 = 3 : 2 at the GUT scale with mixed bino-wino dark matter, the $$ \overset{\sim }{g} $$ g ~ SUGRA model can explain the muon g − 2 anomaly at 1σ level and be consistent with the updated LHC constraints for 6.9 ≤ M3/M1 ≤ 7.5 at the GUT scale. Although the choice of heavy gluino will always increase the FT involved, some of the 1σ/2σ survived points of $$ \Delta {a}_{\mu}^{\mathrm{combine}} $$ ∆ a μ combine can still allow low EWFT of order several hundreds and be fairly natural. Constraints from (dimension-five operator induced) proton decay are also discussed.

Collider signatures of coannihilating dark matter in light of the B-physics anomalies

Motivated by UV explanations of the B-physics anomalies, we study a dark sector containing a Majorana dark matter candidate and a coloured coannihilation partner, connected to the Standard Model predominantly via a U1 vector leptoquark. A TeV scale U1 leptoquark, which couples mostly to third generation fermions, is the only successful single-mediator description of the B-physics anomalies. After calculating the dark matter relic surface, we focus on the most promising experimental avenue: LHC searches for the coloured coannihilation partner. We find that the coloured partner hadronizes and forms meson-like bound states leading to resonant signatures at colliders reminiscent of the quarkonia decay modes in the Standard Model. By recasting existing dilepton and monojet searches we exclude coannihilation partner masses less than 280 GeV and 400 GeV, respectively. Since other existing collider searches do not significantly probe the parameter space, we propose a new dedicated search strategy for pair production of the coloured partner decaying into bbττ final states and dark matter particles. This search is expected to probe the model up to dark matter masses around 600 GeV with current luminosity.

Radiative lepton mass and muon g − 2 with suppressed lepton flavor and CP violations

The recent experimental status, including the confirmation of the muon g − 2 anomaly at Fermilab, indicates a Beyond Standard Model (BSM) satisfying the following properties: 1) it enhances the g − 2 2) suppresses flavor violations, such as μ → eγ, 3) suppresses CP violations, such as the electron electric dipole moment (EDM). In this letter, I show that the eigenbasis of the mass matrix and higher dimensional photon operators can be automatically aligned if the masses of heavy leptons are generated radiatively together with the g − 2. As a result, the muon g − 2 is enhanced but the EDM of the electron and μ → eγ rate are naturally suppressed. Phenomenology and applications of the mechanism to the B-physics anomalies are argued.