Simon Knapen

A Complete Model of Low-Scale Gauge Mediation

A bstractRecent signs of a Standard Model-like Higgs at 125 GeV point towards large A-terms in the MSSM. This presents special challenges for gauge mediation, which by itself predicts vanishing A-terms at the messenger scale. In this paper, we review the general problems that arise when extending gauge mediation to achieve large A-terms, and the mechanisms that exist to overcome them. Using these mechanisms, we construct weakly-coupled models of low-scale gauge mediation with extended Higgs-messenger couplings that generate large A-terms at the messenger scale and viable μ/Bμ-terms. Our models are simple, economical, and complete realizations of supersymmetry at the weak scale.

The Orbifold Higgs

A bstractWe introduce and systematically study an expansive class of “orbifold Higgs” theories in which the weak scale is protected by accidental symmetries arising from the orbifold reduction of continuous symmetries. The protection mechanism eliminates quadratic sensitivity of the Higgs mass to higher scales at one loop (or more) and does not involve any new states charged under the Standard Model. The structures of the Higgs and top sectors are universal and determined exclusively by group theoretical considerations. The twin Higgs model fits within our framework as the simplest example of an orbifold Higgs. Our models admit UV completions as geometric orbifolds in higher dimensions, and fit naturally within frameworks of low scale gauge coupling unification.

General messenger Higgs mediation

A bstractWe present a general formalism for analyzing supersymmetric models where the Higgs sector directly couples to the messengers of supersymmetry breaking. Such Higgs-messenger interactions are strongly motivated by the discovery of a Higgs boson near 125 GeV, but they also raise the specter of the μ/Bμ and

arXiv : Searching for Long-lived Particles: A Compact Detector for Exotics at LHCb

{A \left/ {{m_H^2}} \right.}

Light dark matter in superfluid helium: Detection with multi-excitation production

problems. Using our formalism, we identify new avenues to solving these problems through strong dynamics in the messenger sector or hidden sector. Although our formalism is entirely general, we show how it reproduces familiar results in two simplifying limits: one where the hidden sector consists of a single spurion, and the other where it is approximately superconformal. In the latter limit, our formalism generalizes and clarifies the scenario of hidden sector sequestering, which we show can solve both the μ/Bμ and

Higgs mediation with strong hidden sector dynamics

{A \left/ {{m_H^2}} \right.}

The Vector-like Twin Higgs

problems uniformly.

125 GeV Higgs from tree-level A-terms

Author(s): Gligorov, VV; Knapen, S; Papucci, M; Robinson, DJ | Abstract:

Gamma-rays from dark showers with twin Higgs models

© 2017 American Physical Society. We examine in depth a recent proposal to utilize superfluid helium for direct detection of sub-MeV mass dark matter. For sub-keV recoil energies, nuclear scattering events in liquid helium primarily deposit energy into long-lived phonon and roton quasiparticle excitations. If the energy thresholds of the detector can be reduced to the meV scale, then dark matter as light as ∼MeV can be reached with ordinary nuclear recoils. If, on the other hand, two or more quasiparticle excitations are directly produced in the dark matter interaction, the kinematics of the scattering allows sensitivity to dark matter as light as ∼keV at the same energy resolution. We present in detail the theoretical framework for describing excitations in superfluid helium, using it to calculate the rate for the leading dark matter scattering interaction, where an off-shell phonon splits into two or more higher-momentum excitations. We validate our analytic results against the measured and simulated dynamic response of superfluid helium. Finally, we apply this formalism to the case of a kinetically mixed hidden photon in the superfluid, both with and without an external electric field to catalyze the processes.

Disentangling Mass and Mixing Hierarchies

A bstractWe present a simple model that achieves mh ≈ 126 GeV in the MSSM with large A-terms and TeV-scale stops through a combination of gauge mediation and Higgs-messenger interactions. The μ/Bμ and A/mH2 problems are both solved by a common mechanism — partial sequestering from strong hidden sector dynamics. Using the frame-work of General Messenger Higgs Mediation, we explicitly calculate the soft masses in terms of the vacuum expectation values, operator dimensions and OPE coefficients of the strongly-coupled hidden sector. Along the way, we also present a general analysis of the various constraints on sequestered Higgs mediation models. The phenomenology of such models is similar to gaugino mediation, but with large A-terms. The NLSP is always long-lived and is either the lightest stau or the Higgsino. The colored states are typically out of reach of the 8 TeV LHC, but may be accessible at 14 TeV, especially if the NLSP is the lightest stau.