Search

We investigate the prospects for resonant di-Higgs and heavy Higgs production searches at the 14 TeV HL-LHC in the combination of $bb\gamma\gamma$ and $4l$ channels, as a probe of a possible first order electroweak phase transition in real singlet scalar extension of the Standard Model. Event selection follows those utilized in the $bb\gamma\gamma$ and $4l$ searches by the ATLAS Collaboration, applied to simulation using benchmark parameters that realize a strong first order electroweak phase transition. The output of discriminant analysis is implemented by numerical calculation, optimised by the joint restriction from the two channels. The prospective reach for $bb\gamma\gamma$/$4l$ channel could be more competitive in probing the electroweak phase transition at lower/higher resonance masses. With 3 $ab^{-1}$ integrated luminosity, the combination of the $bb\gamma\gamma$ and $4l$ channels can discover/exclude a significant portion of %\mrmC{isn't it more accurate to say "a significant portion of" ?} of the viable parameter space that realizes a strong first order phase transition when the resonance mass is heavier than 500 GeV.

We formulate a procedure to obtain a gauge-invariant tunneling rate at zero temperature using the recently developed tunneling potential approach. This procedure relies on a consistent power counting in gauge coupling and a derivative expansion. The tunneling potential approach, while numerically more efficient than the standard bounce solution method, inherits the gauge-dependence of the latter when naively implemented. Using the Abelian Higgs model, we show how to obtain a tunneling rate whose residual gauge-dependence arises solely from the polynomial approximations adopted in the tunneling potential computation., Comment: 12 pages, 8 figures; typos corrected

We describe electroweak monopoles within the Born-Infeld extension of $SU(2)_L\times U(1)_Y$ electroweak theory. We argue for topological stability of these monopoles and computed their mass in terms of the Born-Infeld mass parameters. We then propose a new mechanism for electroweak baryogenesis which takes advantage of the following salient features of the electroweak monopoles: (i) monopoles support extra CP violation in the topological sector of the electroweak theory; (ii) they mediate unsuppressed baryon number violating interactions; (iii) non-thermal production of monopoles during the electroweak phase transitions generates departure from thermal equilibrium. We demonstrate that the observed baryon asymmetry of the universe can be explained in our theory in the presence of electroweak monopoles of mass $M\sim 10^{4}$ TeV.

We argue that quantum electrodynamics combined with quantum gravity results in a new source of CP violation, anomalous non-conservation of chiral charge and quantisation of electric charge. Further phenomenological and cosmological implications of this observation are briefly discussed within the standard model of particle physics and cosmology, Comment: v2: reference added

We discuss a cosmological phase transition within the Standard Model which incorporates spontaneously broken scale invariance as a low-energy theory. In addition to the Standard Model fields, the minimal model involves a light dilaton, which acquires a large vacuum expectation value (VEV) through the mechanism of dimensional transmutation. Under the assumption of the cancellation of the vacuum energy, the dilaton develops a very small mass at 2-loop order. As a result, a flat direction is present in the classical dilaton-Higgs potential at zero temperature while the quantum potential admits two (almost) degenerate local minima with unbroken and broken eletroweak symmetry. We found that the cosmological electroweak phase transition in this model can only be triggered by a QCD chiral symmetry breaking phase transition at low temperatures, $T\lesssim 132$ MeV. Furthermore, unlike the standard case, the universe settles into the chiral symmetry breaking vacuum via a first-order phase transition which gives rise to a stochastic gravitational background with a peak frequency $\sim 10^{-8}$ Hz as well as triggers the production of approximately solar mass primordial black holes. The observation of these signatures of cosmological phase transitions together with the detection of a light dilaton would provide a strong hint of the fundamental role of scale invariance in particle physics.

We consider an isolated electroweak monopole solution within the Standard Model with a non-linear Born-Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born-Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the electroweak phase transition and make it more strongly first order for monopole masses $M\gtrsim 9.3\cdot 10^3$ TeV, while the nucleosynthesis constraints on the abundance of relic monopoles impose the bound $M\lesssim 2.3\cdot 10^4$ TeV. The monopoles with a mass in this shallow range may be responsible for the dynamical generation of the matter-antimatter asymmetry during the electroweak phase transition., Comment: 11 pages, 1 figure

This paper investigates the symmetry reduction of the regularised n-body problem. The three body problem, regularised through quaternions, is examined in detail. We show that for a suitably chosen symmetry group action the space of quadratic invariants is closed and the Hamiltonian can be written in terms of the quadratic invariants. The corresponding Lie-Poisson structure is isomorphic to the Lie algebra u(3,3). Finally, we generalise this result to the n-body problem for n>3.