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Register a new userCollider signatures of dark CP-violation
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We study an extension of the Standard Model (SM) in which two copies of the SM-Higgs doublet which do not acquire a vacuum expectation value, and hence are {it inert}, are added to the scalar sector. The lightest particle from the inert sector, which is protected from decaying to SM particles through the conservation of a $Z_2$ symmetry, is a viable dark matter candidate. We allow for CP-violation in this extended dark sector and evaluate the $ZZZ$ vertex and its CP-violating form factor in several benchmark scenarios. We provide collider signatures of this dark CP-violation in the form of potentially observable asymmetries and cross sections for the $fbar fto Z^*to ZZ$ process at both leptonic and hadronic machines.
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We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are added to the scalar sector. These extra doublets do not develop a vacuum expectation value, hence, they are textit{inert}. This essentially leads to a 3-Higgs Doublet Model (3HDM) with 2 inert and 1 active scalar doublets, which we denote as I(2+1)HDM. We allow for CP-violation in the textit{inert} sector, where the lightest textit{inert} state is protected from decaying to SM particles through the conservation of a $Z_2$ symmetry, so that it is a Dark Matter (DM) candidate. For this scenario, we identify a smoking gun signature of dark CP-violation in the form of production thresholds of pairs of textit{inert} neutral Higgs bosons at an $e^+e^-$ collider.
We consider flavor constraints on, and collider signatures of, Asymmetric Dark Matter (ADM) via higher dimension operators. In the supersymmetric models we consider, R-parity violating (RPV) operators carrying B-L interact with n dark matter (DM) particles X through an interaction of the form W = X^n O_{B-L}, where O_{B-L} = q l d^c, u^c d^c d^c, l l e^c. This interaction ensures that the lightest ordinary supersymmetric particle (LOSP) is unstable to decay into the X sector, leading to a higher multiplicity of final state particles and reduced missing energy at a collider. Flavor-violating processes place constraints on the scale of the higher dimension operator, impacting whether the LOSP decays promptly. While the strongest limitations on RPV from n-bar{n} oscillations and proton decay do not apply to ADM, we analyze the constraints from meson mixing, mu-e conversion, mu -> 3 e and b -> s l^+ l^-. We show that these flavor constraints, even in the absence of flavor symmetries, allow parameter space for prompt decay to the X sector, with additional jets and leptons in exotic flavor combinations. We study the constraints from existing 8 TeV LHC SUSY searches with (i) 2-6 jets plus missing energy, and (ii) 1-2 leptons, 3-6 jets plus missing energy, comparing the constraints on ADM-extended supersymmetry with the usual supersymmetric simplified models.
Three possibilities for the origin of CP violation are discussed: (1) the Standard Model in which all CP violation is due to one parameter in the CKM matrix, (2) the superweak model in which all CP violation is due to new physics and (3) the Standard Model plus new physics. A major goal of B physics is to distinguish these possibilities. CP violation implies time reversal violation (TRV) but direct evidence for TRV is difficult to obtain.
We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1)_ell$ gauge symmetry with an associated $Z^prime$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $chi$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^prime$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $chi$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^prime$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1)_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.
Solutions of the Strong CP Problem based on the spontaneous breaking of CP must feature a non-generic structure and simultaneously explain a coincidence between a priori unrelated CP-even and CP-odd mass scales. We show that these properties can emerge from gauge invariance and a CP-conserving, but otherwise generic, physics at the Planck scale. In our scenarios no fundamental scalar is introduced beyond the Standard Model Higgs doublet, and CP is broken at naturally small scales by a confining non-abelian dynamics. This approach is remarkably predictive: robustness against uncontrollable UV corrections to the QCD topological angle requires one or more families of vector-like quarks below a few $10$s of TeV, hence potentially accessible at colliders. Because CP violation is communicated to the SM at these super-soft scales, our solution of the Strong CP Problem is not spoiled by the presence of heavy new states motivated by other puzzles in physics beyond the Standard Model. In addition, these models generically predict a dark sector that may lead to interesting cosmological signatures.
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