Bibhushan Shakya

XENON100 implications for naturalness in the MSSM, NMSSM, and

In a recent paper arXiv:1107.5048, we discussed the correlation between the elastic neutralino-nucleon scattering cross section, constrained by dark matter direct detection experiments, and fine-tuning at tree-level in the electroweak symmetry breaking sector of the Minimal Supersymmetric Standard Model (MSSM). Here, we show that the correlation persists in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), and its variant, lambda-SUSY. Both models are strongly motivated by the recent discovery of a 125 GeV Higgs-like particle. We also discuss the implications of the recently published bound on the direct detection cross section from 225 live days of XENON100 experiment. In both the MSSM and the NMSSM, most of the parameter space with fine-tuning less than 10% is inconsistent with the XENON100 bound. In lambda-SUSY, on the other hand, large regions of completely natural electroweak symmetry breaking are still allowed, primarily due to a parametric suppression of fine-tuning with large \lambda. The upcoming XENON1T experiment will be able to probe most of the parameter space with less than 1% fine-tuning in all three models.

\lambda

A bstractWe calculate contributions to the photon and gluon magnetic dipole operators that mediate b → sγ and b → dγ transitions in the Randall-Sundrum model of a warped extra dimension with anarchic bulk fermions and a brane localized Higgs. Unlike the Standard Model, there are large contributions to the left-handed b quark decays, parameterized by the Wilson coefficient

-supersymmetry model

C_7^{\prime }

The Birds and the Bs in RS: The

, due to the pattern of bulk fermion localization, and sizable contributions from the gluonic penguins,

b to s \gamma

C_8^{{\left( \prime \right)}}

penguin in a warped extra dimension

, through renormalization group mixing. Further, unlike the Randall-Sundrum result for μ → eγ, the unprimed Wilson coefficients receive non-negligible contributions from the misalignment of the bulk fermion spectrum with the Standard Model flavor sector. We compare the size of effects and the constraints imposed by the branching ratios Br(B → Xsγ) and 〈Br(B → Xdγ)〉 within the minimal and the custodial model. Within the custodial framework, we study the effect on a number of benchmark observables and find that Br(B → Xsμ+μ−) and the forward-backward asymmetry in B → K*μ+μ− remain close to their Standard Model predictions. On the other hand, there can be large enhancements of the time-dependent CP asymmetry in B → K*γ and the transverse asymmetry

Spacetime Dynamics of a Higgs Vacuum Instability During Inflation

A_T^{{(2)}}

Higgs Couplings and Naturalness in

.

\lambda

A remarkable prediction of the Standard Model is that, in the absence of corrections lifting the energy density, the Higgs potential becomes negative at large field values. If the Higgs field samples this part of the potential during inflation, the negative energy density may locally destabilize the spacetime. We use numerical simulations of the Einstein equations to study the evolution of inflation-induced Higgs fluctuations as they grow towards the true (negative-energy) minimum. These simulations show that forming a single patch of true vacuum in our past light cone during inflation is incompatible with the existence of our Universe; the boundary of the true vacuum region grows outward in a causally disconnected manner from the crunching interior, which forms a black hole. We also find that these black hole horizons may be arbitrarily elongated—even forming black strings—in violation of the hoop conjecture. By extending the numerical solution of the Fokker-Planck equation to the exponentially suppressed tails of the field distribution at large field values, we derive a rigorous correlation between a future measurement of the tensor-to-scalar ratio and the scale at which the Higgs potential must receive stabilizing corrections in order for the Universe to have survived inflation until today.

-SUSY

A bstractWe study Higgs boson couplings in the large-λ version of the Next-to-Minimal Supersymmetric Standard Model, known as λ-SUSY. We find that the predicted deviations from the Standard Model (SM) in these couplings are inversely correlated with the amount of fine-tuning needed to accommodate a 126 GeV Higgs. In the most natural regions of parameter space, the 126 GeV Higgs has large admixtures of both the SM-singlet and the non-SM Higgs doublet scalars, and such regions are already ruled out by the LHC. Future improvements in the Higgs coupling measurements will either discover deviations from the SM, or put further stress on naturalness in λ-SUSY. We present projections for future experiments and find that HL-LHC and the proposed e+e− Higgs factories can explore regions of parameter space that are fine-tuned at the level of up to 0.1%.