Top (S)Partners And The Higgs Mass

This thesis explores the interplay between the Higgs potential, partners to the top quark, and LHC data. Due to the intimate connection between the top quark and the Higgs, top partners play a special role in any theories designed to resolve the hierarchy problem of the Standard Model using symmetries to protect the Higgs from large quantum corrections. We begin by reviewing the general framework of top partners and the hierarchy problem, and the way in which symmetries can impose cancellations between quadratically divergent diagrams contributing to the Higgs mass. Following this, we discuss an interpretation in terms of stops of an anomaly in an ATLAS search for SUSY in events with a leptonically decaying Z, jets and MET. We argue that this excess can be understood as resulting from pair produced heavy stops decaying into lighter stops and Z bosons, ̃t2 → ̃t1Z, with masses in the range m ̃t ' 300–500 GeV. While such light stops are natural in terms of the hierarchy problem, they place the MSSM in great tension with the measured mass of the Higgs boson. We therefore explore the possibility that this tension is resolved by new non-decoupling D-term contributions to the Higgs mass associated with a new SU(2)R gauge symmetry broken at ∼ few TeV. In particular, we consider the possibility that the W ′ associated with such a gauge symmetry is responsible for another ATLAS excess in a search for diboson resonances, while remaining consistent with a 125 GeV Higgs. We finish our tour of supersymmetric theories with a discussion of the prospects for discovering top partners of spin-1 at a future collider. The second half of the thesis discusses some new phenomenology of spin-1/2 top partners. We construct models in which the collider phenomenology and impli- cations for the Higgs mass differ markedly from generic top partners. By imposing an approximate or exact discrete symmetry on the new states, it is possible to mimic final states that are reminiscent of R-parity conserving or violating SUSY, and we explore the limits that searches for these scenarios impose on the spin-1/2 scenario. Finally, we discuss how Yukawa structures that can be found in these theories can provide significant radiative enhancements for the Higgs mass.

Supersymmetry
Hierarchy problem
Top partners
supersymmetry: hierarchy
Higgs particle: mass

References(200)

Figures(0)

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