51 research outputs found
One-Loop MSSM predictions for at low tan
No full textOne of the most promising signals of new physics at colliders is the rare decay B(^0_s) â μ+μ(^-).The LHC will be the first experiment to directly probe this loop- and helicity- suppressed decay channel down to the Standard Model prediction. Deviations from the predicted branching ratio are a signature of new particles in the loops. In particular, it is well known that the MSSM prediction scales as tan(^6) β due to the supersymmetric Higgs penguin diagrams, making this a fertile testing ground for SUSY. In this study we analyse the MSSM prediction for the general B(_s,d) â â+â in the hertofore unexplored low tan beta region of the MSSM parameter space where interference with the box and Z-penguin diagrams could cause the branching ratio to dip below the Standard Model prediction. This decay is particularly important since it could be the first unambigious signal of new physics at the LHC and also guide the future LHCb upgrade
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AdS Opacity, Soft Bombs, and Exotic Forces
No full textEffective field theory is arguably one of the most powerful theoretical tools that we have at our disposal as physicists. It enables us to describe the low-energy physics of a wide range of models with relatively few operators. In this thesis, we show how so-called "irrelevant" (higher-dimension) EFT operators lead to a number of novel, yet under-appreciated properties, both in flat and negatively-curved Anti de-Sitter spacetime.
In flat space, higher-dimension EFT operators give rise to spin-dependent quantum forces which arise at loop level. We determine these forces and show how they can be used to probe specific models of dark matter. We point out that the oft-discussed spin-dependent Yukawa forces have specific properties and are not representative of the behavior of generic potentials. Quantum forces from irrelevant EFT operators can and should serve as complimentary benchmark cases when discussing potential bounds from various fifth-force experiments. We discuss how the neutrino force, a famous example of a quantum force, can be used to determine the Dirac/Majorana origin of the neutrino mass.In (4+1)-dimensional Anti de-Sitter spacetime, we show how the presence of higher-dimension EFT operators implies a number of novel properties for bulk particles. These include soft, high multiplicity cascade decays known as soft bombs and the merging of spectral resonances into a continuum at high energies. The negative curvature of AdS warps momentum scales, leading to a puzzle where particles created in one part of the space can appear to be outside the region of EFT invalidity in another part of the space. We provide the resolution to this puzzle and demonstrate the self-consistency of the EFT
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New Directions in Dark Sector Model Building: From Flat to Warped Spacetime
No full textWe present four dark sector models with novel phenomena beyond the weakly-interacting massive particle paradigm. We present a model of spin-1 dark matter charged under a U1) gauge symmetry, resulting from the spontaneous symmetry breaking of an SU(2) dark sector. The dark matter is subject thermal freeze out and direct detection constraints while simultaneously meeting self-interaction targets for small scale structure anomalies. We present a model of pseudo-Goldstone boson dark matter based of the same symmetry structure. The pseudo-Goldstone boson dark matter satisfies thermal freeze out and direct detection constraints while satisfying self-interaction targets as well. We expand the self-interacting dark matter framework to the case of a continuum of mediators and present a model of continuum-mediated self-interacting dark matter. The model is described holographically by brane localized dark matter interacting with a bulk scalar in a slice of 5D anti-de Sitter space. The long-range scattering potential follows a non-integer power law, resulting in a self-scattering cross section that depends on a non-integer power of the dark matter relative velocity as well as Sommerfeld enhancement which exhibits a pattern of resonances determined by the non-integer power. The novel power laws introduced by the continuum mediator present new possibilities self-interacting dark matter phenomenology. We expand the dark photon framework to the case where the dark photon is a continuum of states, modeled as a bulk spin-1 field interacting with brane-localized matter in a 5D slice of anti-de Sitter space. We derive a simple formula for recasting existing dark photon bounds for our model. We consider a model of brane-localized dark matter which freezes out by annihilating into holographic dark photons, and present targets for the dark matter mass and coupling to the holographic dark photon. We conclude that even though a definitive signal for dark matter remains unseen, there are several possibilities for model building and future study which may provide further insight into the microscopic nature of dark matter
Erratum: Dark photons from captured inelastic dark matter annihilation: Charged particle signatures [Phys. Rev. D <b>95</b> , 075015 (2017)]
No full textDark photons from captured inelastic dark matter annihilation: Charged particle signatures
No full textDynamics of 3D SUSY gauge theories with antisymmetric matter
No full textWe investigate the IR dynamics of N = 2 SUSY gauge theories in 3D with antisymmetric matter. The presence of the antisymmetric fields leads to further splitting of the Coulomb branch. Counting zero modes in the instanton background suggests that more than a single direction along the Coulomb branch may remain unlifted. We examine the case of SU(4) with one or two antisymmetric fields and various flavors in detail. Using the results for the corresponding 4D theories, we find the IR dynamics of the 3D cases via compactification and a real mass deformation. We find that for the s-confining case with two antisymmetric fields, a second unlifted Coulomb branch direction indeed appears in the low-energy dynamics. We present several non-trivial consistency checks to establish the validity of these results. We also comment on the expected structure of general s-confining theories in 3D, which might involve several unlifted Coulomb branch directions. © 2014 The Author(s)
Beyond the Standard Model
No full textWe introduce aspects of physics beyond the Standard Model focusing on supersymmetry, extra dimensions, and a composite Higgs as solutions to the Hierarchy problem. Lectures given at the 2013 European School of High Energy Physics, Parádfürdo, Hungary, 5-18 June 2013.We introduce aspects of physics beyond the Standard Model focusing on supersymmetry, extra dimensions, and a composite Higgs as solutions to the Hierarchy problem. Lectures at the European School of High Energy Physics, Par\'adf\"urd\H{o}, Hungary, 5-18 June 2013
Efficient sampling of constrained high-dimensional theoretical spaces with machine learning
No full textModels of physics beyond the Standard Model often contain a large number of
parameters. These form a high-dimensional space that is computationally
intractable to fully explore. Experimental constraints project onto a subspace
of viable parameters, but mapping these constraints to the underlying
parameters is also typically intractable. Instead, physicists often resort to
scanning small subsets of the full parameter space and testing for experimental
consistency. We propose an alternative approach that uses generative models to
significantly improve the computational efficiency of sampling high-dimensional
parameter spaces. To demonstrate this, we sample the constrained and
phenomenological Minimal Supersymmetric Standard Models subject to the
requirement that the sampled points are consistent with the measured Higgs
boson mass. Our method achieves orders of magnitude improvements in sampling
efficiency compared to a brute force search
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