R-Parity-violating supersymmetry

http://cds.cern.ch/record/704268/files/0312378.pdf

The Soft supersymmetry breaking Lagrangian: Theory and applications

In the most general two-Higgs-doublet model (2HDM), unitary transformations between the two Higgs fields do not change the functional form of the Lagrangian. All physical observables of the model must therefore be independent of such transformations (i.e., independent of the Lagrangian basis choice for the Higgs fields). We exhibit a set of basis-independent quantities that determine all tree-level Higgs couplings and masses. Some examples of the basis-independent treatment of 2HDM discrete symmetries are presented. We also note that the ratio of the neutral Higgs field vacuum expectation values, tan β, is not a meaningful parameter in general, as it is basis-dependent. Implications for the more specialized 2HDMs (e.g., the Higgs sector of the MSSM and the so-called Type-I and Type-II 2HDMs) are explored.

Basis-independent methods for the two-Higgs-doublet model

We extend previous combinations of LEP and cosmological relic density constraints on the parameter space of the constrained MSSM, with universal input supersymmetry-breaking parameters, to large tan beta. We take account of the possibility that the lightest Higgs boson might weigh about 115 GeV, but also retain the possibility that it might be heavier. We include the most recent implementation of the b to s gamma constraint at large tan beta. We refine previous relic density calculations at large tan beta by combining a careful treatment of the direct-channel Higgs poles in annihilation of pairs of neutralinos chi with a complete treatment of chi - stau coannihilation, and discuss carefully uncertainties associated with the mass of the b quark. We find that coannihilation and pole annihilations allow the CMSSM to yield an acceptable relic density at large tan beta, but it is consistent with all the constraints only if m_chi > 140 (180) GeV for mu > 0 (mu < 0) for our default choices m_b(m_b) = 4.25 GeV, m_t = 175 GeV, and A_0 = 0.

The CMSSM Parameter Space at Large tan beta

We re-examine the parameter space of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), taking account of the restricted range of \Omega_{CDM} h^2 consistent with the WMAP data. This provides a significantly reduced upper limit on the mass of the lightest supersymmetric particle LSP: m_\chi 0, or \tan \beta < 30 and \mu < 0, thereby improving the prospects for measuring supersymmetry at the LHC, and increasing the likelihood that a 1-TeV linear e^+ e^- collider would be able to measure the properties of some supersymmetric particles.

Supersymmetric Dark Matter in Light of WMAP

It has recently been pointed out that viable sparticle mass spectra can be generated in Yukawa unified SO(10) supersymmetric grand unified models consistent with radiative breaking of electroweak symmetry. Model solutions are obtained only if tan{beta}{approx}50, {mu}<0 and positive D-term contributions to scalar masses from SO(10) gauge symmetry breaking are used. In this paper, we attempt to systematize the parameter space regions where solutions are obtained. We go on to calculate the relic density of neutralinos as a function of parameter space. No regions of the parameter space explored were actually cosmologically excluded, and very reasonable relic densities were found in much of parameter space. Direct neutralino detection rates could exceed 1 event/kg/day fora{sup 73}Ge detector, for low values of GUT scale gaugino mass m{sub 1/2}. We also calculate the branching fraction for b{yields}s{gamma} decays, and find that it is beyond the 95% C.L. experimental limits in much, but not all, of the parameter space regions explored. For the Fermilab Tevatron collider, significant regions of parameter space can be explored via b{bar B}A and b{bar B}H searches. There also exist some limited regions of parameter space where a trilepton signal can be seen at TeV33. Finally, there exist significant regionsmore » of parameter space where direct detection of bottom squark pair production can be made, especially for large negative values of the GUT parameter A{sub 0}.« less

Yukawa unified supersymmetric SO(10) model: Cosmology, rare decays and collider searches

We present an updated assessment of the viability of t−b−τ Yukawa coupling unification in supersymmetric models. For the superpotential Higgs mass parameter μ > 0, we find unification to less than 1% is possible, but only for GUT scale scalar mass parameter m 16 ~ 8−20 TeV, and small values of gaugino mass m 1/2400 GeV. Such models require that a GUT scale mass splitting exists amongst Higgs scalars with m H u 2 < m H d 2 . Viable solutions lead to a radiatively generated inverted scalar mass hierarchy, with third generation and Higgs scalars being lighter than other sfermions. These models have very heavy sfermions, so that unwanted flavor changing and CP violating SUSY processes are suppressed, but may suffer from some fine-tuning requirements. While the generated spectra satisfy b→sγ and (g−2)μ constraints, there exists tension with the dark matter relic density unless m 163 TeV. These models offer prospects for a SUSY discovery at the Fermilab Tevatron collider via the search for 12→3l events, or via gluino pair production. If μ < 0, Yukawa coupling unification to less than 5% can occur for m 16 and m 1/21−2 TeV. Consistency of negative μ Yukawa unified models with b→sγ, (g−2)μ , and relic density Ωh 2 all imply very large values of m 1/2 typically greater than about 2.5 TeV, in which case direct detection of sparticles may be a challenge even at the LHC.

http://cds.cern.ch/record/605997/files/0302155.pdf

Yukawa coupling unification in supersymmetric models

We present an updated assessment of the viability of t-b-tau Yukawa coupling unification in supersymmetric models. For the superpotential Higgs mass parameter mu>0, we find unification to less than 1% is possible, but only for GUT scale scalar mass parameter m_{16}~8-20 TeV, and small values of gaugino mass m_{1/2} s gamma and (g-2)_mu constraints, there exists tension with the dark matter relic density unless m_{16} 3 leptons events, or via gluino pair production. If mu 1-2 TeV. Consistency of negative mu Yukawa unified models with b->s gamma, (g-2)_mu, and relic density all imply very large values of m_{1/2} typically greater than about 2.5 TeV, in which case direct detection of sparticles may be a challenge even at the LHC.

Yukawa Coupling Unification in Supersymmetric Models

Supersymmetric grand unified models based on $\mathrm{SO}(10)$ gauge symmetry have many desirable features, including the unification of Yukawa couplings. Including $D$-term contributions to scalar masses arising from the breakdown of $\mathrm{SO}(10)$, Yukawa coupling unification only to $30%$ can be achieved in models with a positive superpotential Higgs mass. The superparticle mass spectrum is highly constrained and yields relatively light top squarks and charginos. Surprisingly, the pattern of grand unified theory scale soft supersymmetry breaking masses are close to those found in the context of inverted hierarchy models.

Javier Ferrandis

Papers

Yukawa unified supersymmetric SO(10) model: Cosmology, rare decays and collider searches

Yukawa coupling unification in supersymmetric models

Yukawa Coupling Unification in Supersymmetric Models

Supersymmetric SO(10) grand unified models with Yukawa unification and a positive mu term.

Charged Higgs boson and stau phenomenology in the simplest R-parity breaking model