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Khosa, C. K., & Sanz, V. (2022). On the Impact of the LHC Run 2 Data on General Composite Higgs Scenarios. Adv. High. Energy Phys., 2022, 8970837–13pp.
Abstract: We study the impact of Run 2 LHC data on general composite Higgs scenarios, where nonlinear effects, mixing with additional scalars, and new fermionic degrees of freedom could simultaneously contribute to the modification of Higgs properties. We obtain new experimental limits on the scale of compositeness, the mixing with singlets and doublets with the Higgs, and the mass and mixing angle of top-partners. We also show that for scenarios where new fermionic degrees of freedom are involved in electroweak symmetry breaking, there is an interesting interplay among Higgs coupling measurements, boosted Higgs properties, SMEFT global analyses, and direct searches for single and double production of vector-like quarks.
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Oldengott, I. M., Barenboim, G., Kahlen, S., Salvado, J., & Schwarz, D. J. (2019). How to relax the cosmological neutrino mass bound. J. Cosmol. Astropart. Phys., 04(4), 049–18pp.
Abstract: We study the impact of non-standard momentum distributions of cosmic neutrinos on the anisotropy spectrum of the cosmic microwave background and the matter power spectrum of the large scale structure. We show that the neutrino distribution has almost no unique observable imprint, as it is almost entirely degenerate with the effective number of neutrino flavours, N-eff, and the neutrino mass, m(nu). Performing a Markov chain Monte Carlo analysis with current cosmological data, we demonstrate that the neutrino mass bound heavily depends on the assumed momentum distribution of relic neutrinos. The message of this work is simple and has to our knowledge not been pointed out clearly before: cosmology allows that neutrinos have larger masses if their average momentum is larger than that of a perfectly thermal distribution. Here we provide an example in which the mass limits are relaxed by a factor of two.
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Middeldorf-Wygas, M. M., Oldengott, I. M., Bödeker, D., & Schwarz, D. J. (2022). Cosmic QCD transition for large lepton flavor asymmetries. Phys. Rev. D, 105, 123533–10pp.
Abstract: We study the impact of large lepton flavor asymmetries on the cosmic QCD transition. Scenarios of unequal lepton flavor asymmetries are observationally almost unconstrained and therefore open up a whole new parameter space for the cosmic QCD transition. We find that for large asymmetries, the formation of a Bose-Einstein condensate of pions can occur and identify the corresponding parameter space. In the vicinity of the QCD transition scale, we express the pressure in terms of a Taylor expansion with respect to the complete set of chemical potentials. The Taylor coefficients rely on input from lattice QCD calculations from the literature. The domain of applicability of this method is discussed.
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Doring, C., Centelles Chulia, S., Lindner, M., Schaefer, B. M., & Bartelmann, M. (2022). Gravitational wave induced baryon acoustic oscillations. SciPost Phys., 12(3), 114–47pp.
Abstract: We study the impact of gravitational waves originating from a first order phase transition on structure formation. To do so, we perform a second order perturbation analysis in the 1 + 3 covariant framework and derive a wave equation in which second order, adiabatic density perturbations of the photon-baryon fluid are sourced by the gravitational wave energy density during radiation domination and on sub-horizon scales. The scale on which such waves affect the energy density perturbation spectrum is found to be proportional to the horizon size at the time of the phase transition times its inverse duration. Consequently, structure of the size of galaxies and bigger can only be affected in this way by relatively late phase transitions at >= 10(6) s. Using cosmic variance as a bound we derive limits on the strength a and the relative duration (beta/H-*)(-1) of phase transitions as functions of the time of their occurrence which results in a new exclusion region for the energy density in gravitational waves today. We find that the cosmic variance bound forbids only relative long lasting phase transitions, e.g. beta/H-* less than or similar to 6.8 for t(*) approximate to 5 x 10(11 )s, which exhibit a substantial amount of supercooling alpha > 20 to affect the matter power spectrum.
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Caputo, A., Sberna, L., Toubiana, A., Babak, S., Barausse, E., Marsat, S., et al. (2020). Gravitational-wave Detection and Parameter Estimation for Accreting Black-hole Binaries and Their Electromagnetic Counterpart. Astrophys. J., 892(2), 90–13pp.
Abstract: We study the impact of gas accretion on the orbital evolution of black-hole binaries initially at large separation in the band of the planned Laser Interferometer Space Antenna (LISA). We focus on two sources: (i).stellar-origin black-hole binaries.(SOBHBs) that can migrate from the LISA band to the band of ground-based gravitational-wave (GW) observatories within weeks/months; and (ii) intermediate-mass black-hole binaries.(IMBHBs) in the LISA band only. Because of the large number of observable GW cycles, the phase evolution of these systems needs to be modeled to great accuracy to avoid biasing the estimation of the source parameters. Accretion affects the GW phase at negative (-4) post-Newtonian order, being thus dominant for binaries at large separations. Accretion at the Eddington or at super-Eddington rate will leave a detectable imprint on the dynamics of SOBHBs. For super-Eddington rates and a 10 yr mission, a multiwavelength strategy with LISA and a ground-based interferometer can detect about 10 (a few) SOBHB events for which the accretion rate can be measured at 50% (10%) level. In all cases, the sky position can be identified within much less than 0.4 deg(2) uncertainty. Likewise, accretion at greater than or similar to 100% of the Eddington rate can be measured in IMBHBs up to redshift z approximate to 0.1, and the position of these sources can be identified within less than 0.01 deg(2) uncertainty. Altogether, a detection of SOBHBs or IMBHBs would allow for targeted searches of electromagnetic counterparts to black-hole mergers in gas-rich environments with future X-ray detectors (such as Athena) and/or radio observatories (such as SKA).
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