1,720,973 research outputs found
The supercooling window at weak and strong coupling
Full text linkSupercooled first order phase transitions are typical of theories where conformal symmetry is predominantly spontaneously broken. In these theories the fate of the flat scalar direction is highly sensitive to the size and the scaling dimension of the explicit breaking deformations. For a given deformation, the coupling must lie in a particular region to realize a supercooled first order phase transition. We identify the supercooling window in weakly coupled theories and derive a fully analytical understanding of its boundaries. Mapping these boundaries allows us to identify the deformations enlarging the supercooling window and to characterize their dynamics analytically. For completeness we also discuss strongly coupled conformal field theories with an holographic dual, where the complete characterization of the supercooling window is challenged by calculability issues
The ultraviolet landscape of two-Higgs doublet models
No full textWe study the predictions of generic ultraviolet completions of two-Higgs doublet models. We assume that at the matching scale between the two-Higgs doublet model and an ultraviolet complete theory – which can be anywhere between the TeV and the Planck scale – arbitrary but perturbative values for the quartic couplings are present. We evaluate the couplings down from the matching scale to the weak scale and study the predictions for the scalar mass spectrum. In particular, we show the importance of radiative corrections which are essential for both an accurate Higgs mass calculation as well as determining the stability of the electroweak vacuum. We study the relation between the mass splitting of the heavy Higgs states and the size of the quartic couplings at the matching scale, finding that only a small class of models exhibit sizeable mass splittings between the heavy scalars at the weak scale. Moreover, we find a clear correlation between the maximal size of the couplings and the considered matching scale
Spontaneous charge breaking in the NMSSM: dangerous or not?
No full textWe investigate the impact of charge-breaking minima on the vacuum stability of the NMSSM. We concentrate on the case of vanishing A-terms in the sfermion sector, i.e. the only potentially dangerous sources of charge breaking are vacuum expectation values of the charged Higgs fields. We find that, in contrast to Two-Higgs-Doublet Models like the MSSM, at both tree and loop level there exist global charge-breaking minima. Consequently, many regions of parameter space are rendered metastable, which otherwise would have been considered stable if these charge-breaking minima were neglected. However, the inclusion of these new scalar field directions has little impact on otherwise metastable vacuum configurations
Magnetic moments of astrophysical neutrinos
No full textWe study the impact of neutrino magnetic moments on astrophysical neutrinos, in particular supernova neutrinos and ultra-high energy neutrinos from extragalactic sources. We show that magnetic moment-induced conversion of Dirac neutrinos from left-handed states into unobservable right-handed singlet states can substantially change the flux and flavour composition of these neutrinos at Earth. Notably, neutrinos from a supernova's neutronisation burst, whose flux can be predicted with O(10%) accuracy, offer a discovery reach to neutrino magnetic moments ∼ few × 10-13 μB , up to one order of magnitude below current limits. For high-energy neutrinos from distant sources, for which no robust flux prediction exists, we show how the flavour composition at Earth can be used as a handle to establish the presence of non-negligible magnetic moments, potentially down to few× 10-17 μB if the measurement can be performed on neutrinos from a single source. In both cases, the sensitivity strongly depends on the galactic (intergalactic) magnetic field profiles along the line of sight. Therefore, while a discovery is possible down to very small values of the magnetic moment, the absence of a discovery does not imply an equally strong limit. We also comment on the dependence of our results on the right-handed neutrino mass, paying special attention to the transition from coherent deflection by a classical magnetic field to incoherent scattering on individual scattering targets. Finally, we show that a measurement of Standard Model Dirac neutrino magnetic moments, of order 10-19 μB , could be possible under rather optimistic, but not completely outrageous, assumptions using flavour ratios of high-energy astrophysical neutrinos
Dark matter, destroyer of worlds: Neutrino, thermal, and existential signatures from black holes in the Sun and Earth
No full textDark matter can be captured by celestial objects and accumulate at their centers, forming a core of dark matter that can collapse to a small black hole, provided that the annihilation rate is small or zero. If the nascent black hole is big enough, it will grow to consume the star or planet. We calculate the rate of dark matter accumulation in the Sun and Earth, and use their continued existence to place novel constraints on high mass asymmetric dark matter interactions. We also identify and detail less destructive signatures: a newly-formed black hole can be small enough to evaporate via Hawking radiation, resulting in an anomalous heat flow emanating from Earth, or in a flux of high-energy neutrinos from the Sun observable at IceCube. The latter signature is entirely new, and we find that it may cover large regions of parameter space that are not probed by any other method
Soft gamma rays from heavy WIMPs
No full textWe propose an explanation of the galactic center gamma ray excess by supersymmetric WIMPs as heavy as 500 GeV. The lightest neutralino annihilates into vector-like leptons or quarks which cascade decay through intermediate Higgs bosons. Due to the long decay chains, the gamma ray spectrum is much softer than naively expected and peaks at GeV energies. The model predicts correlated diboson and dijet signatures to be tested at the LHC
Dark, cold, and noisy: Constraining secluded hidden sectors with gravitational waves
No full textWe explore gravitational wave signals arising from first-order phase transitions occurring in a secluded hidden sector, allowing for the possibility that the hidden sector may have a different temperature than the Standard Model sector. We present the sensitivity to such scenarios for both current and future gravitational wave detectors in a model-independent fashion. Since secluded hidden sectors are of particular interest for dark matter models at the MeV scale or below, we pay special attention to the reach of pulsar timing arrays. Cosmological constraints on light degrees of freedom restrict the number of sub-MeV particles in a hidden sector, as well as the hidden sector temperature. Nevertheless, we find that observable first-order phase transitions can occur. To illustrate our results, we consider two minimal benchmark models: a model with two gauge singlet scalars and a model with a spontaneously broken U(1) gauge symmetry in the hidden sector
Lepton PDFs and multipurpose single-lepton searches at the LHC
Full text linkA final state consisting of one charged lepton, at least one jet, and little missing transverse energy can be a very promising signature of new physics at the LHC across a wide range of models. However, it has received only limited attention so far. In this work we discuss the potential sensitivity of this channel to various new physics scenarios. To demonstrate our point, we consider its application to lepton parton distribution functions (PDFs) at the LHC in the context of supersymmetry. These lepton PDFs can lead to resonant squark production (similar to leptoquarks) via lepton number violating couplings present in R-parity violating supersymmetry (RPV-SUSY). Unlike leptoquarks, in RPV-SUSY there are many possible decay modes leading to a wide range of signatures. We propose two generic search regions: (a) a single first or second generation charged lepton, exactly 1 jet and low missing transverse energy, and (b) a single first or second generation charged lepton, at least 3 jets, and low missing transverse energy. We demonstrate that together these cover a large range of RPV-SUSY signatures, and have the potential to perform better than existing low-energy bounds, while being general enough to extend to a wide range of possible models hitherto not explored at the LHC
Lattice simulations of non-minimally coupled scalar fields in the Jordan frame
Full text linkThe presence of scalar fields with non-minimal gravitational interactions of the form ξ|φ|2R may have important implications for the physics of the early universe. We propose a procedure to solve the dynamics of non-minimally coupled scalar fields directly in the Jordan frame, where the non-minimal couplings are maintained explicitly. Our algorithm can be applied to lattice simulations that include minimally coupled fields and an arbitrary number of non-minimally coupled scalars, with the expansion of the universe sourced by all fields present. This includes situations when the dynamics become fully inhomogeneous, fully non-linear (due to e.g. backreaction or mode rescattering effects), and/or when the expansion of the universe is dominated by non-minimally coupled species. As an example, we study geometric preheating with a non-minimally coupled scalar spectator field when the inflaton oscillates following the end of inflation
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Probing Muonic Forces with Neutron Stars Binaries
Full text linkWe show that gravitational wave emission from neutron star binaries can be used to discover any generic long-ranged muonic force due to the large inevitable abundance of muons inside neutron stars. As a minimal consistent example, we focus on a gauged U(1)Lμ-Lτ symmetry. In pulsar binaries, such U(1)Lμ-Lτ vectors induce an anomalously fast decay of the orbital period through the emission of dipole radiation. We study a range of different pulsar binaries, finding the most powerful constraints for vector masses below O(10-18 eV). For merging binaries, the presence of muons in neutron stars can result in dipole radiation as well as a modification of the chirp mass during the inspiral phase. We make projections for a prospective search using both the GW170817 and S190814bv events and find that current data can discover light vectors with masses below O(10-10 eV). In both cases, the limits attainable with neutron stars reach gauge coupling g′≲10-20, which are many orders of magnitude stronger than previous constraints. We also show projections for next generation experiments, such as Einstein Telescope and Cosmic Explorer.We show that gravitational wave emission from neutron star binaries can be used to discover any generic long-ranged muonic force due to the large inevitable abundance of muons inside neutron stars. As a minimal consistent example, we focus on a gauged U(1) symmetry. In pulsar binaries, such U(1) vectors induce an anomalously fast decay of the orbital period through the emission of dipole radiation. We study a range of different pulsar binaries, finding the most powerful constraints for vector masses below . For merging binaries the presence of muons in neutron stars can result in dipole radiation as well as a modification of the chirp mass during the inspiral phase. We make projections for a prospective search using both the GW170817 and S190814bv events and find that current data can discover light vectors with masses below . In both cases, the limits attainable with neutron stars reach gauge coupling , which are many orders of magnitude stronger than previous constraints. We also show projections for next generation experiments, such as Einstein Telescope and Cosmic Explorer
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