Athanasios Dedes

The Snowmass points and slopes: Benchmarks for SUSY searches

Abstract. The ”Snowmass Points and Slopes” (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present and future experiments. This set of benchmarks was agreed upon at the 2001 ”Snowmass Workshop on the Future of Particle Physics” as a consensus based on different existing proposals.

Bounds on R -parity violating couplings at the weak scale and at the GUT scale

We analyse bounds on trilinear R-parity violating couplings at the unification scale by renormalising the weak scale bounds. We derive unification scale upper bounds upon the couplings which are broadly independent of the fermion mass texture assumed. The R-parity violating couplings are factors of two to five more severely bounded at the unification scale than at the electroweak scale. In the presence of quark mixing, a few of the bounds are orders of magnitude stronger than their weak scale counterparts due to new R-parity violating operators being induced in the renormalisation between high and low scales. These induced bounds are fermion mass texture dependent. New bounds upon the weak scale couplings are obtained by the requirement of perturbativity between the weak and unification scales. A comprehensive set of the latest limits is included.

On the two-loop Yukawa corrections to the MSSM Higgs boson masses at large tanβ

Abstract We complete the effective potential calculation of the two-loop, top/bottom Yukawa corrections to the Higgs boson masses in the minimal supersymmetric standard model, by computing the O (α t 2 +α t α b +α b 2 ) contributions for arbitrary values of the bottom Yukawa coupling. We also compute the corrections to the minimization conditions of the effective potential at the same perturbative order. Our results extend the existing O (α t 2 ) calculation, and are relevant in regions of the parameter space corresponding to tanβ⪢1. We extend to the Yukawa corrections a convenient renormalization scheme, previously proposed for the O (α b α s ) corrections, that avoids unphysically large threshold effects associated with the bottom mass and absorbs the bulk of the corrections into the one-loop expression. For large values of tanβ, the new contributions can account for a variation of several GeV in the lightest Higgs boson mass.

Correlation of B(s) --> mu(+)mu(-) and (g - 2)(mu) in minimal supergravity.

We analyze the decay mode B(s)-->mu(+)mu(-) in minimal supergravity (mSUGRA). We find that the recently measured excess in (g-2)(mu), if interpreted within mSUGRA, is correlated with a substantial enhancement of the branching ratio Beta(B(s)-->mu(+)mu(-)): if (g-2)(mu) exceeds the standard model prediction by 4 x 10(-9), Beta(B(s)-->mu(+)mu(-)) is larger by a factor of 10-100 and within reach of Run-II of the Tevatron. Thus the search for B(s)-->mu(+)mu(-) is a stringent test of the GUT scale relations of mSUGRA. An observation of B(s)-->mu(+)mu(-) at the Tevatron implies a mass of the lightest SUSY Higgs boson below 120 GeV. B(s)-->mu(+)mu(-) can also significantly probe SO(10) SUSY GUT models.

Correlation of Bs --> µ+µ and (g 2)µ in Minimal Supergravity

Athanasios Dedes, Herbert K. Dreiner and Ulrich Nierste 1 Physikalisches Institut, Universität Bonn, Nußallee 12, D-53115 Bonn, Germany 2 CERN, TH Division, CH-1211 Geneva 23, Switzerland We analyse the rare decay mode Bs → μ+μ− in the minimal supergravity scenario (mSUGRA). We find a strong correlation with the muon anomalous magnetic moment (g − 2)μ. An interpretation of the recently measured excess in (g − 2)μ in terms of mSUGRA corrections implies a substantial supersymmetric enhancement of the branching ratio B(Bs → μ+μ−): if (g−2)μ exceeds the Standard Model prediction by 3 ·10−9, B(Bs → μ+μ−) is larger by a factor of 100 than in the Standard Model and well within reach of Run-II of the Tevatron. Thus an experimental search for Bs → μ+μ− is a stringent test of the mSUGRA GUT scale boundary conditions. If the decay Bs → μ+μ− is observed at Run-II of the Tevatron, then we predict the mass of lightest supersymmetric Higgs boson to be less than 118 GeV. The decay Bs → μ+μ− can also significantly probe the favoured parameter range in SO(10) SUSY GUT models, possibly excluding them.

Phenomenology of a new minimal supersymmetric extension of the standard model

We study the phenomenology of a new minimally extended supersymmetric standard model (nMSSM) where a gauge singlet superfield is added to the MSSM spectrum. The superpotential of this model contains no dimensionful parameters, thus solving the ? problem of the MSSM. A global discrete R symmetry, forbidding the cubic singlet self-interaction, imposed on the complete theory, guarantees its stability with respect to generated higher-order tadpoles of the singlet and solves both the domain wall and Peccei-Quinn axion problems. We give the free parameters of the model and display some general constraints on them. Particular attention is devoted to the neutralino sector where a (quasipure) singlino appears to be always the LSP of the model, leading to additional cascades, involving the NLSP ? LSP transition, compared with the MSSM. We then present the upper bounds on the masses of the lightest and next-to-lightest—when the lightest is an invisible singlet—CP-even Higgs bosons, including the full one-loop and dominant two-loop corrections. These bounds are found to be much higher than the equivalent ones in the MSSM. Finally, we discuss some phenomenological implications for the Higgs sector of the nMSSM in Higgs boson production at future hadron colliders.

Two-loop corrections to radiative electroweak symmetry breaking in the MSSM

Abstract We study the O (α t α s +α t 2 ) two-loop corrections to the minimization conditions of the MSSM effective potential, providing compact analytical formulae for the Higgs tadpoles. We connect these results with the renormalization group running of the MSSM parameters from the grand unification scale down to the weak scale, and discuss the corrections to the Higgs mixing parameter μ and to the running CP-odd Higgs mass mA in various scenarios of gravity-mediated SUSY breaking. We find that the O (α t α s ) and O (α t 2 ) contributions partially cancel each other in the minimization conditions. In comparison with the full one-loop corrections, the O (α t α s +α t 2 ) two-loop corrections significantly weaken the dependence of the parameters μ and mA on the renormalization scale at which the effective potential is minimized. The residual two-loop and higher-order corrections to μ and mA are estimated to be at most 1% in the considered scenarios.

SUSY_FLAVOR: A computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY FLAVOR version 2 — a Fortran 77 program that calculates low-energy flavor observables in the general R-parity conserving MSSM. For a set of MSSM parameters as input, the code gives predictions for: 1. Electric dipole moments of the leptons and the neutron. 2. Anomalous magnetic moments (i.e. g − 2) of the leptons. 3. Radiative lepton decays (μ → eγ and τ → μγ, eγ). 4. Rare Kaon decays (K0 L → π0ν̄ν and K+ → π+ν̄ν). 5. Leptonic B decays (Bs,d → l+l−, B → τν and B → Dτν). 6. Radiative B decays (B → X̄sγ). 7. ∆F = 2 processes (K̄0–K0, D̄–D, B̄d–Bd and B̄s–Bs mixing). Comparing to SUSY FLAVOR v1, where the matching conditions were calculated strictly at one-loop level, SUSY FLAVOR v2 performs the resummation of all chirally enhanced corrections, i.e. takes into account the enhanced effects from tan β and/or large trilinear soft mixing terms to all orders in perturbation theory. Also, in SUSY FLAVOR v2 new routines calculating of B → (D)τν, g− 2, radiative lepton decays and Br(l → lγ) were added. All calculations are done using exact diagonalization of the sfermion mass matrices. The program can be obtained from http://www.fuw.edu.pl/susy flavor.

Higgs-mediated Bs,d0→μτ,eτ and τ→3μ,eμμ decays in supersymmetric seesaw models

We study the rates allowed for the Higgs-mediated decays

THE HIGGS PENGUIN AND ITS APPLICATIONS: AN OVERVIEW

B_{s,d}^0\to\mu\tau, e\tau