Abstract We study a scenario in which the expansion of Early Universe is driven by hot hidden sector (HS) with an initial temperature T ' that significantly higher than visible (VS), ≫ . The latter assumed to be made Standard Model (SM) particles and our main focus on possibility dark matter (DM) part dominant HS its abundance set secluded freeze-out. In particular, we subsequent evolution fate DM companion particle after freeze-out all way toward reheating VS. To make this more concrete,...

We consider simultaneous explanations of the electron and muon $g-2$ anomalies through a single $Z'$ $U(1)'$ extension to Standard Model (SM). first perform model-independent analysis viable flavour-dependent couplings leptons, which are subject various strict experimental constraints. show that only narrow region parameter space with an MeV-scale can account for two anomalies. Following conclusions this analysis, we then explore ability different classes models realise these couplings,...

The clockwork mechanism is a novel method for generating large separation between the dynamical scale and interaction of theory. We demonstrate how can arise from sequence strongly-coupled sectors. This framework avoids elementary scalar fields as well ad hoc continuous global symmetries, both which are subject to serious stability issues. factor, q, determined by consistency strong dynamics. preserved U(1) appears an accidental symmetry, resulting discrete or gauge it spontaneously broken...

In the absence of direct evidence new physics, any ultraviolet theory can be reduced to its specific set low-energy effective operators. As a case study, we derive field for seesaw extension Standard Model, with sterile neutrinos mass $M>m_W$. We systematically compute all Wilson coefficients generated at one loop. Hence, it becomes straightforward (i) identify parameters compatible smallness neutrino masses; (ii) precision lepton observables, which may sensitive scales as large $M\sim 10^3$...

Abstract We investigate new-physics contributions to $$b\rightarrow s \ell $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>b</mml:mi><mml:mo>→</mml:mo><mml:mi>s</mml:mi><mml:mi>ℓ</mml:mi><mml:mi>ℓ</mml:mi></mml:mrow></mml:math> transitions in the context of an effective field theory extension Standard Model, including operator mixing at one loop. identify few scenarios where a single Wilson coefficient, $$C/\Lambda ^2 \sim 1/\mathrm{TeV}^2$$...

New physics in the lepton sector may account for neutrino masses, affect electroweak precision observables, induce charged-lepton flavour violation, and shift dipole moments. The low-energy predictions of different models are most conveniently compared within formalism effective field theory. To illustrate benefits this approach, we derive Wilson coefficients a set representative models: fermionic seesaw mechanisms (type I III), Zee model, minimal leptoquark model. In each case, Weinberg...

In this article we show that in the usual type-I seesaw framework, augmented solely by a neutrino portal interaction, dark matter (DM) relic density can be created through freeze-in, manner fully determined interactions and DM particle mass. This simple freeze-in scenario, where is not state, proceeds slow, seesaw-induced decays of Higgs $W$ $Z$ bosons. We identify two scenarios, one which predicts existence an observable line.

We consider, in general terms, the possible parameter space of thermal dark matter candidates. assume that particle is fundamental and was equilibrium a hidden sector with temperature ${T}^{\ensuremath{'}}$, which may differ from Standard Model temperature, $T$. The candidates lie region ${T}^{\ensuremath{'}}/T$ vs. ${m}_{\mathrm{dm}}$ plane, bounded by both model-independent theoretical considerations observational constraints. former consists limits decoupled when relativistic (the floor)...

If the stability of dark matter (DM) particle is due to an accidental symmetry, nothing prevents UV physics from destabilising it by inducing DM decays suppressed powers scale. The seesaw physics, presumably at origin neutrino mass, could induce such a decay. We show that if scale lies around usual Weinberg operator scale, induced decay generically lead lines whose intensity order present sensitivity telescopes. illustrate this possibility with models in which made gauge boson(s) abelian or...

We consider the light $Z'$ explanation of muon $g-2$ anomaly. Even if such a has no tree-level coupling to electrons, in general one will be induced at loop-level. show that future beam dump experiments are powerful enough place stringent constraints on$-$or discover$-$a with loop-suppressed couplings electrons. Such bounds avoided only large interaction neutrinos, which case scenario bounded by ongoing neutrino scattering experiments. The complementarity between and therefore indicates...

Abstract In an earlier work [1], we showed that in very simple neutrino portal-like extensions of the Standard Model it is possible to achieve a one-to-one correspondence between dark matter physics and seesaw parameters controlling genesis masses. Notably, this can occur both when produced via freeze-in relativistic freeze-out. article, carry out detailed phenomenological study such scenarios. Specifically, find allowed regions for portal coupling within which valid. We further constrain...

The Sommerfeld enhancement plays an important role in dark matter (DM) physics, and can significantly enhance the annihilation cross section of non-relativistic DM particles. In this paper, we study effect neutrino forces, which are generated by exchange a pair light neutrinos, on enhancement. We demonstrate that certain cases, force cause significant correction to Models realise DM-neutrino interactions sizeable also briefly discussed, together with impacts phenomenology forces.

Abstract A sterile neutrino with a keV-scale mass is compelling dark matter candidate. We propose new production mechanism involving the decay and annihilation of complex scalar singlet Higgs portal coupling which develops vacuum expectation value. The interactions resulting pseudo Nambu-Goldstone boson may thermalise sector. determine region parameter space where sector thermalisation reached discuss most relevant cosmological observables. scenario can be considered as combination freeze-in...

A bstract weak-doublet with hypercharge −3 / 2 is one of only a handful fermions which has renormalisable interaction Standard Model fields. This should make it worthy attention, but thus far received little consideration in the literature. In this paper, we perform thorough investigation phenomenology results from introduction field, F . After expressing model terms its effective field theory at dimension-6, compute range electroweak and leptonic observables, most stringent probe up to M ~...

A weak-doublet with hypercharge $-3/2$ is one of only a handful fermions which has renormalisable interaction Standard Model fields. This should make it worthy attention, but thus far received little consideration in the literature. In this paper, we perform thorough investigation phenomenology results from introduction field, $F$. After expressing model terms its effective field theory at dimension-6, compute range electroweak and leptonic observables, most stringent probe up to $M_F \sim...

A sterile neutrino with a keV-scale mass is compelling dark matter candidate. We propose new production mechanism involving the decay and annihilation of complex scalar singlet Higgs portal coupling which develops vacuum expectation value. The interactions resulting pseudo Nambu-Goldstone boson may thermalise sector. determine region parameter space where sector thermalisation reached discuss most relevant cosmological observables. scenario can be considered as combination freeze-in followed...

In an earlier work, we showed that in very simple neutrino portal-like extensions of the Standard Model it is possible to achieve a one-to-one correspondence between dark matter physics and seesaw parameters controlling genesis masses. Notably, this can occur both when produced via freeze-in relativistic freeze-out. article, carry out detailed phenomenological study such scenarios. Specifically, find allowed regions for portal coupling within which valid. We further constrain parameter space...