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Register a new userDark Side of the Standard Model: Dormant New Physics Awaken
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We find that the nonperturbative physics of the standard-model Higgs Lagrangian provides a dark matter candidate, dormant skyrmion in the standard model, the same type of the skyrmion, a soliton, as in the hadron physics. It is stabilized by another nonperturbative object in the standard model, the dynamical gauge boson of the hidden local symmetry, which is also an analogue of the rho meson.
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Assuming dark matter is absolutely stable due to unbroken dark gauge symmetry and singlet operators are portals to the dark sector, we present a simple extension of the standard seesaw model that can accommodate all the cosmological observations as well as terrestrial experiments available as of now, including leptogenesis, extra dark radiation of $sim 0.08$ (resulting in $N_{rm eff} = 3.130$ the effective number of neutrino species), Higgs inflation, small and large scale structure formation, and current relic density of scalar DM ($X$). The Higgs signal strength is equal to one as in the SM for unbroken $U(1)_X$ case with a scalar dark matter, but it could be less than one independent of decay channels if the dark matter is a dark sector fermion or if $U(1)_X$ is spontaneously broken, because of a mixing with a new neutral scalar boson in the models.
The proposed LDMX experiment would provide roughly a meter-long region of instrumented tracking and calorimetry that acts as a beam stop for multi-GeV electrons in which each electron is tagged and its evolution measured. This would offer an unprecedented opportunity to access both collider-invisible and ultra-short lifetime decays of new particles produced in electron (or muon)-nuclear fixed-target collisions. In this paper, we show that the missing momentum channel and displaced decay signals in such an experiment could provide world-leading sensitivity to sub-GeV dark matter, millicharged particles, and visibly or invisibly decaying axions, scalars, dark photons, and a range of other new physics scenarios.
The Fermi effective theory of the weak interaction helped identify the structure of the electroweak sector of the Standard Model, and the chiral effective Lagrangian pointed towards QCD as the theory of the strong interactions. The Standard Model Effective Field Theory (SMEFT) is a systematic and model-independent framework for characterizing experimental deviations from the predictions of the Standard Model and pointing towards the structures of its possible extensions that is complementary to direct searches for new physics beyond the Standard Model. This talk summarizes results from the first global fit to data from LHC Run 2 and earlier experiments including dimension-6 SMEFT operators, and gives examples how it can be used to constrain scenarios for new physics beyond the Standard Model. In addition, some windows for probing dimension-8 SMEFT operators are also mentioned.
In presence of non-standard neutrino interactions the neutrino flavor evolution equation is affected by a degeneracy which leads to the so-called LMA-Dark solution. It requires a solar mixing angle in the second octant and implies an ambiguity in the neutrino mass ordering. Non-oscillation experiments are required to break this degeneracy. We perform a combined analysis of data from oscillation experiments with the neutrino scattering experiments CHARM and NuTeV. We find that the degeneracy can be lifted if the non-standard neutrino interactions take place with down quarks, but it remains for up quarks. However, CHARM and NuTeV constraints apply only if the new interactions take place through mediators not much lighter than the electroweak scale. For light mediators we consider the possibility to resolve the degeneracy by using data from future coherent neutrino-nucleus scattering experiments. We find that, for an experiment using a stopped-pion neutrino source, the LMA-Dark degeneracy will either be resolved, or the presence of new interactions in the neutrino sector will be established with high significance.
The lack of confirmation for the existence of supersymmetric particles and Weakly Interacting Massive Particles (WIMPs) appeals to extension of the field of studies of the physical nature of dark matter, involving non-supersymmetric and non-WIMP solutions. We briefly discuss some examples of such candidates in their relationship with extension of particle symmetry and pattern of symmetry breaking. We specify in the example of axion-like particles nontrivial features of cosmological reflection of the structure and pattern of Peccei-Quinn-like symmetry breaking. The puzzles of direct and indiect dark matter searches can find solution in the approach of composite dark matter. The advantages and open problems of this approach are specified. We note that detailed analysis of cosmological consequences of any extension of particle model that provides candidates for dark matter inevitably leads to nonstandard features in the corresponding cosmological scenario. It makes possible to use methods of cosmoparticle physics to study physical nature of the dark matter in the combination of its physical, astrophysical and cosmological signatures.
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