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Register a new userPrecise focus point scenario for a natural Higgs boson in the MSSM
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A small Higgs mass parameter m_{h_u}^2 can be insensitive to various trial heavy stop masses, if a universal soft squared mass is assumed for the chiral superpartners and the Higgs boson at the grand unification (GUT) scale, and a focus point (FP) of m_{h_u}^2 appears around the stop mass scale. The challenges in the FP scenario are (1) a too heavy stop mass (~ 5 TeV) needed for the 126 GeV Higgs mass and (2) the too high gluino mass bound (> 1.4 TeV). For a successful FP scenario, we consider (1) a superheavy right-hand (RH) neutrino and (2) the first and second generations of hierarchically heavier chiral superpartners. The RH neutrino can move a FP in the higher energy direction in the space of (Q, m_{h_u}^2(Q)), where Q denotes the renormalization scale. On the other hand, the hierarchically heavier chiral superpartners can lift up a FP in that space through two-loop gauge interactions. Precise focusing of m_{h_u}^2(Q) is achieved with the RH neutrino mass of ~ 10^{14} GeV together with an order one (0.9-1.2) Dirac Yukawa coupling to the Higgs boson, and the hierarchically heavy masses of 15-20 TeV for the heavier generations of superpartners, when the U(1)_R breaking soft parameters, m_{1/2} and A_0 are set to be 1 TeV at the GUT scale. Those values can naturally explain the small neutrino mass through the seesaw mechanism, and suppress the flavor violating processes in supersymmetric models.
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We study the production of scalar and pseudoscalar Higgs bosons via gluon fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD calculation implemented in the public code SusHi, we provide precise predictions for the Higgs-production cross section in six benchmark scenarios compatible with the LHC searches. We also provide a detailed discussion of the sources of theoretical uncertainty in our calculation. We examine the dependence of the cross section on the renormalization and factorization scales, on the precise definition of the Higgs-bottom coupling and on the choice of PDFs, as well as the uncertainties associated to our incomplete knowledge of the SUSY contributions through NNLO. In particular, a potentially large uncertainty originates from uncomputed higher-order QCD corrections to the bottom-quark contributions to gluon fusion.
State-of-the-art predictions for the mass of the lightest MSSM Higgs boson usually involve the resummation of higher-order logarithmic contributions obtained within an effective-field-theory (EFT) approach, often combined with a fixed-order calculation into a hybrid result. For the phenomenologically interesting case of a significant hierarchy between the gluino mass and the masses of the scalar top quarks the predictions suffer from large theoretical uncertainties related to non-decoupling power-enhanced gluino contributions in the EFT results employing the $overline{text{DR}}$ renormalisation scheme. We demonstrate that the theoretical predictions in the heavy gluino region are vastly improved by the introduction of a suitable renormalisation scheme for the EFT calculation. It is shown that within this scheme a recently proposed resummation of large gluino contributions is absorbed into the model parameters, resulting in reliable and numerically stable predictions in the heavy-gluino gluino region. We also discuss the integration of the results into the public code FeynHiggs.
The analysis of the Higgs search results at LEP showed that a part of the MSSM parameter space with non-zero complex phases could not be excluded, where the lightest neutral Higgs boson, h_1, has a mass of only about 45 GeV and the second lightest neutral Higgs boson, h_2, has a sizable branching fraction into a pair of h_1 states. Full one-loop results for the Higgs cascade decay h_2 --> h_1 h_1 are presented and combined with two-loop Higgs propagator corrections taken from the program FeynHiggs. Using the improved theoretical prediction to analyse the limits on topological cross sections obtained at LEP, the existence of an unexcluded region at low Higgs mass is confirmed. The effect of the genuine vertex corrections on the size and shape of this region is discussed.
The neutral Higgs sector of the minimal supersymmetric standard model (MSSM) in explicit CP violation scenario is investigated at the one-loop level. Within the context of the effective potential formalism, the masses of the neutral Higgs bosons are calculated at the one-loop level by taking into account the contributions of the following loops of ordinary particles and superpartners: top quark, the scalar top quarks, bottom quark, the scalar bottom quarks, tau lepton, the scalar tau leptons, $W$ boson, the charged Higgs boson, the charginos, $Z$ boson, the scalar and pseudoscalar Higgs bosons, and the neutralinos. Our calculation is an improvement in the sense that both the terms which are quartic in the electroweak coupling constants into account, and the pseudoscalar Higgs loop contribution are explicitly included.
Different approaches are used for the calculation of the SM-like Higgs boson mass in the MSSM: the fixed-order diagrammatic approach is accurate for low SUSY scales; the EFT approach,for high SUSY scales. Hybrid approaches, combining fixed-order and EFT calculations, allow to obtain a precise prediction also for intermediary SUSY scales. Here, we briefly discuss the hybrid approach implemented into the code FeynHiggs. In addition, we show how the refined Higgs mass prediction was used to define new MSSM Higgs benchmark scenarios.
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