Di-Higgs production in the 4b channel and gravitational wave complementarity

Abstract

We present a complementarity study of gravitational waves and double Higgs production in the 4b channel, exploring the gauge singlet scalar extension of the SM. This new physics extension serves as a simplified benchmark model that realizes a strongly first-order electroweak phase transition necessary to generate the observed baryon asymmetry in the universe. In calculating the signal-to-noise ratio of the gravitational waves, we incorporate the effect of the recently discovered significant suppression of the gravitational wave signals from sound waves for strong phase transitions, make sure that supercooled phase transitions do complete and adopt a bubble wall velocity that is consistent with a successful electroweak baryogenesis by solving the velocity profiles of the plasma. The high-luminosity LHC sensitivity to the singlet scalar extension of the SM is estimated using a shape-based analysis of the invariant 4b mass distribution. We find that while the region of parameter space giving detectable gravitational waves is shrunk due to the new gravitational wave simulations, the qualitative complementary role of gravitational waves and collider searches remain unchanged.

A fresh look at the gravitational-wave signal from cosmological phase transitions

“…As a consequence, most of the parameter points in our scan describe phase transitions of the detonation type. For lower velocities, which typically result in sub-or supersonic deflagrations and which are relevant in the context of electroweak baryogenesis [37], the GW signal from sound waves can be significantly suppressed [74].…”

“…In this paper, we will illustrate our idea by constructing the signal region for a particularly simple BSM model, namely, the real-scalar-singlet extension of the SM (xSM) [40][41][42][43][44][45][46], which supplements the SM Higgs sector by an additional real gauge-singlet scalar, S, that also obtains a nonzero vacuum expectation value (VEV) during the electroweak phase transition [47][48][49][50][51][52][53]. The GW phenomenology of the xSM has been studied before [14,22,37,[54][55][56][57]; however, in our analysis, we are going to look at the GW signal in this model from a new perspective by projecting the results of our parameter scan into the space of peak frequencies and peak amplitudes. This results in sensitivity plots for future space-based GW experiments that are reminiscent of similar plots in the field of DM direct-detection experiments.…”

Gravitational wave and collider searches for electroweak symmetry breaking patterns

“…To deal with this conundrum, we follow Refs. [9,42,73,74] by taking the plasma hydrodynamics into account and distinguish v w from the velocity used in EWBG calculations. This is due to the existence of three modes of fluid velocity profiles around the bubble wall: deflagration, detonation, and supersonic deflagration (see [65] for a recent combined analysis).…”

A fragmentation-based study of heavy quark production

“…While initial-state collinear logarithms have been studied in details in above-mentioned literature, the situation is much less clear for processes in which final-state (timelike) splittings into heavy quarks contribute significantly to the process. Processes of this kind include bbW production [18,19,[43][44][45][46][47][48], the top-mediated contribution to bbH produc-tion [49], ttbb production [50][51][52][53][54][55] and multi-b final states [56,57] (mostly relevant for dior triple-Higgs searches [58][59][60]). While the importance of the resummation of collinear logarithms has been partially investigated for Q → Qg splittings [35,61,62], no assessment of the impact of the logarithms of M m exists to date, as far as the g → QQ splittings are concerned.…”