On the Radiative Corrections to the Pseudo-scalar Higgs Boson Mass

We reexamine the one-loop corrections to the mass of the pseudo-scalar Higgs boson, using the effective potential. In the absence of the chargino and neutralino contributions its mass exhibits a large scale dependence in the large $M_{1/2}$ regime, especially for values of $\tan \beta>20$. Thus, although of electroweak origin, the heaviness of the $M_{1/2}$, in conjunction with the largeness of $\tan \beta$, makes these corrections very important for establishing a scale independent result and an unambiguous determination of the pseudo-scalar mass in this region of the parameter space

Collective treatment of High Energy Thresholds in SUSY - GUTs

Supersymmetric GUTs are the most natural extension of the Standard model unifying electroweak and strong forces. Despite their indubitable virtues, among these the gauge coupling unification and the quantization of the electric charge, one of their shortcomings is the large number of parameters used to describe the high energy thresholds (HET), which are hard to handle. We present a new method according to which the effects of the HET, in any GUT model, can be described by fewer parameters that are randomly produced from the original set of the parameters of the model. In this way, regions favoured by the experimental data are easier to locate, avoiding a detailed and time consuming exploration of the parameter space, which is multidimensional even in the most economic unifying schemes. To check the efficiency of this method, we directly apply it to a SUSY SO(10) GUT model in which the doublet-triplet splitting is realized through the Dimopoulos-Wilczek mechanism. We show that the demand of gauge coupling unification, in conjunction with precision data, locates regions of the parameter space in which values of the strong coupling \astrong are within the experimental limits, along with a suppressed nucleon decay, mediated by a higgsino driven dimension five operators, yielding lifetimes that are comfortably above the current experimental bounds. These regions open up for values of the SUSY breaking parameters m_0, M_1/2 < 1 TeV being therefore accessible to LHC.Comment: 21 pages, 8 figures, UA-NPPS/BSM-10/02 (added

On the Higgs Mass in the CMSSM

We estimate the mass of the lightest neutral Higgs boson h in the minimal supersymmetric extension of the Standard Model with universal soft supersymmetry-breaking masses (CMSSM), subject to the available accelerator and astrophysical constraints. For m_t = 174.3 GeV, we find that 114 GeV < m_h < 127 GeV and a peak in the tan beta distribution simeq 55. We observe two distinct peaks in the distribution of m_h values, corresponding to two different regions of the CMSSM parameter space. Values of m_h < 119 GeV correspond to small values of the gaugino mass m_{1/2} and the soft trilinear supersymmetry-breaking parameter A_0, lying along coannihilation strips, and most of the allowed parameter sets are consistent with a supersymmetric interpretation of the possibly discrepancy in g_mu - 2. On the other hand, values of m_h > 119 GeV may correspond to much larger values of m_{1/2} and A_0, lying in rapid-annihilation funnels. The favoured ranges of m_h vary with m_t, the two peaks being more clearly separated for m_t = 178 GeV and merging for m_t = 172.7 GeV. If the g_mu - 2 constraint is imposed, the mode of the m_h distribution is quite stable, being sim 117 GeV for all the studied values of m_t.Comment: 14 pages, 12 figure

On the Interpretation of B_s to mu^+ mu^- in the CMSSM

We discuss the interpretation of present and possible future experimental constraints on B_s to mu^+ mu^- decay in the context of the constrained minimal extension of the Standard Model (CMSSM) with universal scalar masses. We emphasize the importance of including theoretical and other experimental uncertainties in calculating the likelihood function, which can affect significantly the inferred 95% confidence-level limit on the CMSSM parameters. The principal uncertainties are the B_s meson decay constant, m_t and m_b. The latter induce uncertainties in the mass of the charged Higgs boson that dominates the B_s to mu^+ mu^- decay amplitude at large tan beta, reducing the CMSSM region excluded by present and possible future limits from the Fermilab Tevatron collider and the LHC.Comment: 19 pages, 12 eps figures, as appears in Phys. Lett.

Collective treatment of high energy thresholds in SUSY GUTs

Supersymmetric GUT&apos;s are the most natural extension of the Standard Model unifying electroweak and strong forces. Despite their indubitable virtues, among these the gauge coupling unification and the quantization of the electric charge, one of their shortcomings is the large number of parameters used to describe the high energy thresholds, which are hard to handle. We present a new method according to which the effects of the high energy thresholds, in any GUT model, can be described by fewer parameters that are randomly produced from the original set of the parameters of the model. In this way, regions favored by the experimental data are easier to locate, avoiding a detailed and time-consuming exploration of the parameter space, which is multidimensional even in the most economic unifying schemes. To check the efficiency of this method, we directly apply it to a SUSY SO(10) GUT model in which the doublettriplet splitting is realized through the DimopoulosWilczek mechanism. We show that the demand of gauge coupling unification, in conjunction with precision data, locates regions of the parameter space in which values of the strong coupling αstrong are within the experimental limits, along with a suppressed nucleon decay, mediated by a higgsino driven dimension five operators, yielding lifetimes that are comfortably above the current experimental bounds. These regions open up for values of the SUSY breaking parameters m0, M1/2 &amp;lt; 1 TeV being therefore accessible to LHC. © 2011 World Scientific Publishing Company