The Effective Theory of the Light Stop Scenario
Marcela Carena, Germano Nardini, Mariano Quiros, Carlos E. M. Wagner
TL;DR
The paper addresses realizing electroweak baryogenesis within the MSSM via the light stop scenario, where heavy scalar superpartners necessitate a careful Higgs-mass calculation. It builds a renormalization-group-improved LE EFT below the heavy scale $\tilde{m}$, with run-and-match at $\tilde{m}$ (and gluino thresholds) to resum large logarithms. A two-loop analysis under gauge-coupling unification and EWBG-consistent assumptions yields predictions for the heavy-scalar scale $\tilde{m}$ in the range $[3\,\mathrm{TeV}, 6\times 10^{2}\,\mathrm{TeV}]$ and Higgs-mass bounds $m_h \lesssim 150\,\mathrm{GeV}$, tightened to $\lesssim 129\,\mathrm{GeV}$ for EWBG-allowed regions. The work also discusses collider phenomenology and dark matter implications, providing benchmarks for experimental tests.
Abstract
Electroweak baryogenesis in the minimal supersymmetric extension of the Standard Model may be realized within the light stop scenario, where the right-handed stop mass remains close to the top-quark mass to allow for a sufficiently strong first order electroweak phase transition. All other supersymmetric scalars are much heavier to comply with the present bounds on the Higgs mass and the electron and neutron electric dipole moments. Heavy third generation scalars render it necessary to resum large logarithm contributions to perform a trustable Higgs mass calculation. We have studied the one--loop RGE improved effective theory below the heavy scalar mass scale and obtained reliable values of the Higgs mass. Moreover, assuming a common mass $\tilde m$ for all heavy scalar particles, and values of all gaugino masses and the Higgsino mass parameter about the weak scale, and imposing gauge coupling unification, a two-loop calculation yields values of the mass $\tilde m$ in the interval between three TeV and six hundred TeV. Furthermore for a stop mass around the top quark mass, this translates into an upper bound on the Higgs mass of about 150 GeV. The Higgs mass bound becomes even stronger, of about 129 GeV, for the range of stop and gaugino masses consistent with electroweak baryogenesis. The collider phenomenology implications of this scenario are discussed in some detail.