Coset cosmology

The strength of electroweak symmetry breaking may substantially differ in the early Universe compared to the present day value. In the Standard Model, the Higgs vacuum expectation value (vev ) vanishes and electroweak symmetry gets restored at temperatures above ∼ 160 GeV due to the Higgs field interactions with the high-temperature plasma. It was however shown that new light singlet scalar fields may change this behaviour. The key feature is the non-standard dependence on the Higgs vev of the new particles mass which can vanish at large Higgs vev, inducing a negative correction to the Higgs thermal mass, leading to electroweak symmetry non-restoration at high temperature. We show that such an effect can also be induced by new singlet fermions which on the other hand have the advantage of not producing unstable directions in the scalar potential at tree level, nor bringing additional severe hierarchy problems. As temperature drops, such a high-temperature breaking phase may continuously evolve into the zero-temperature breaking phase or the two phases can be separated by a temporary phase of restored symmetry. We discuss how our construction can naturally arise in motivated models of new physics, such as Composite Higgs. This is particularly relevant for baryogenesis, as it opens a whole class of possibilities in which the baryon asymmetry can be produced during a high temperature phase transition, while not being erased later by sphalerons.

Section: Jhep09(2020)012mentioning

confidence: 99%

“…For the same reason we will also not consider the modifications which may be needed to solve the domain wall problem of PNGB Higgs potentials pointed out in ref. [29].…”

Section: Goldstone Higgsmentioning

confidence: 99%

High-temperature electroweak symmetry non-restoration from new fermions and implications for baryogenesis

Matsedonskyi

Servant

2020

“…Scalar dark matter (DM) in the context of composite Higgs models (CHM) [1][2][3] has received important attention in the last years [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The reason is that both the Higgs boson and the DM are composite pseudo Nambu-Goldstone bosons (pNGBs) of the same new strongly interacting sector with global symmetry breaking pattern G/H at a scale f ∼ TeV.…”

Section: Introductionmentioning

confidence: 99%

Composite dark matter phenomenology in the presence of lighter degrees of freedom

Ramos

2020

Scalar singlet dark matter in anomaly-free composite Higgs models is accompanied by exotic particles to which the dark matter annihilates. The latter can therefore freeze out even in the absence of couplings to the Standard Model. In this regime, both current and future direct detection constraints can be avoided. Moreover, due to the different decay modes of the extra particles, the dark matter candidate can even escape indirect detection constraints. Assessing this issue requires dedicated simulations of the gamma ray spectrum, that we provide in the present article in the context of SO(7)/SO(6). For the parameter space region that evades constraints from dark matter experiments, we develop new analyses to be performed at a future 100 TeV collider based on the search of the new particles produced in the decay of heavy vector-like quarks.

“…As shown in ref [31],. the degeneracy between the h = 0 and h = πf vacua can be lifted by a small tilt in the potential.…”

mentioning

confidence: 70%

Composite dynamics in the early Universe

Curtis

Rose

Panico

2019

We study the occurrence of a strong first-order electroweak phase transition in composite Higgs models. Minimal constructions realising this scenario are based on the coset SO(6)/SO(5) which delivers an extended Higgs sector with an additional scalar. In such models, a two-step phase transition can be obtained with the scalar singlet acquiring a vacuum expectation value at intermediate temperatures. A bonus of the Nambu-Goldstone boson nature of the scalar-sector dynamics is the presence of non-renormalisable Higgs interactions that can trigger additional sources of CP violation needed to realise baryogenesis at the electroweak scale. Another interesting aspect of this scenario is the generation of gravitational wave signatures that can be observed at future space-based interferometers.New physics models in which the Higgs boson arises as a pseudo Nambu-Goldstone Boson (NGB) from a strongly interacting theory can provide other natural scenarios in which first-order transitions can be obtained. The simplest models realising the idea of a NGB Higgs, the minimal Composite Higgs Models (CHMs) [21], are based on the symmetry breaking pattern SO(5) → SO(4), which delivers the four real scalar degrees of freedom that build-up a SM-like SU(2) Higgs doublet. In these scenarios the Higgs couplings are modified, but the strong experimental constraints already put an upper bound of order 10% on these deviations [22,23]. Moreover direct and indirect searches exclude additional composite resonances for masses below ∼ 1 TeV [24][25][26]. For these reasons the corrections to the Higgs thermal potential are necessarily small and can not convert the EWPhT into a strong first-order one.Successful CHMs exhibiting a first order EW transition can instead be realised by considering non-minimal symmetry-breaking patterns. A simple possibility, on which we will focus in this work, is provided by the coset SO(6)/SO(5) [27,28], in which the Higgs doublet is accompanied by an extra real scalar η. In this case the effective potential for the scalar fields allows for a much richer phase-transition behaviour. The EW transition may proceed directly from the symmetric phase to the EW-symmetry-breaking (EWSB) one or via some intermediate steps. The latter possibility is particularly interesting. As we will see, in a large part of the parameter space of the model, a two-step EWSB transition can be realised, in which the singlet gets a vacuum expectation value (VEV) at intermediate temperatures. In such case, the presence of a H 2 η 2 portal interaction creates a barrier between the EW vacuum and the intermediate vacuum, giving rise to a first-order transition that can be strong enough to allow for baryogenesis.Another interesting aspect of the composite scenario is the fact that the NGB nature of the Higgs implies the presence of non-renormalisable Higgs interactions that can provide additional sources of CP violation. As we will see, interactions of the form η ht L t R , are naturally there in SO(6)/SO(5) models and can trigger CP-violating effec...