arXiv subjects

S. Pokorski

Publications and source records attributed to S. Pokorski.

60 records · Page 4Linked to original sources

arXiv1993

Radiative Electroweak Symmetry Breaking and the Infrared Fixed Point of the Top Quark Mass

The infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model explains in a natural way large values of the top quark mass and appears as a prediction in many interesting theoretical schemes. Moreover, as has been recently pointed out, for moderate values of $\tanβ$, in order to achieve gauge and bottom-tau Yukawa coupling unification, the top quark mass must be within $10 \%$ of its fixed point value. In this work we show that the convergence of the top quark mass to its fixed point value has relevant consequences for the (assumed) universal soft supersymmetry breaking parameters at the grand unification scale. In particular, we show that the low energy parameters do not depend on $A_0$ and $B_0$ but on the combination $δ= B_0 - A_0/2$. Hence, there is a reduction in the number of independent parameters. Most interesting, the radiative $SU(2)_L \times U(1)_Y$ breaking condition implies strong correlations between the supersymmetric mass parameter $μ$ and the supersymmetry breaking parameters $δ$ and $M_{1/2}$ or $m_0$. These correlations, which become stronger for $\tanβ< 2$, may have some fundamental origin, which would imply the need of a reformulation of the naive fine tuning criteria.

hep-ph↗

arXiv1993

Infrared Fixed Point Solution for the Top Quark Mass and Unification of Couplings in the MSSM

We analyze the implications of the infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model. This solution could explain in a natural way the relatively large value of the top quark mass and, if confirmed experimentally, may be suggestive of the onset of nonperturbative physics at very high energy scales. In the framework of grand unification, the expected bottom quark - tau lepton Yukawa coupling unification is very sensitive to the fixed point structure of the top quark mass. For the presently allowed values of the electroweak parameters and the bottom quark mass, the Yukawa coupling unification implies that the top quark mass must be within ten percent of its fixed point values.

hep-ph↗

arXiv1993

Phase Transitions in NJL and super-NJL models

An elementary method of determination of the character of the hot phase transition in 4d four-fermion NJL-type models is applied to non-supersymmetric and supersymmetric versions of simple NJL model. We find that in the non-susy case the transition is usually of the second order. It is weakly first order only in the region of parameters which correspond to fermion masses comparable to the cut-off. In the supersymmetric case both kinds of phase transitions are possible. For sufficiently strong coupling and sufficiently large susy-breaking scale the transition is always of the first order.

hep-th↗

arXiv1993

Complete On-Shell Renormalization Scheme for the Minimal Supersymmetric Higgs Sector

Systematic on-shell renormalization programme is carried out for the Higgs and gauge boson sectors of the Minimal Supersymmetric Standard Model. Complete 1-loop results for the 2- and 3-point Green's functions are explicitly given. The Higgs boson masses and the cross sections for the neutral scalar production in the $e^+e^-$ colliders are calculated.

hep-ph↗

arXiv1993

Bottom-Up Approach to Uniefied Supergravity Models

A new approach is proposed to phenomenological study of a generic unified supergravity model, which reduces to the minimal supersymmetric standard model. The model is effectively parametrized in terms of five low energy observables. In consequence, it is easy to investigate systematically the parameter space of the model, allowed by the requirement of radiative electroweak symmetry breaking and by the present experimental limits. Radiative corrections due to large Yukawa couplings and particle--sparticle mass splitting are included into the analysis and found to have important effects, in particular on the degree of fine tuning in the model. In this framework there are presented the predictions of the model for various low energy physical observables and their dependence on the values of the top quark mass and $\tanβ$ is discussed. Results are also given for the large $\tanβ$ scenario, $\tanβ\approx m_t/m_b$. Our approach can be easily extended to non--minimal supergravity models, which do not assume the universality of the soft breaking parameters at the unification scale $M_X$. Such an extension will be particularly useful once the masses of some sparticles are known, allowing for a model independent study of the parameter space at $M_X$.

hep-ph↗

arXiv1993

On the Unification of Couplings in the Minimal Supersymmetric Standard Model

The unification of gauge and Yukawa couplings within the minimal supersymmetric standard model is studied at the two loop level. We derive an expression for the effective scale, $T_{SUSY}$, which characterizes the supersymmetric particle threshold corrections to the gauge couplings, and demonstrate that $T_{SUSY}$ is only slightly dependent on the squark and slepton masses, and strongly dependent on the Higgsino masses as well as on the mass ratio of the gauginos of the strong and weak interactions. Moreover, the value of the top quark Yukawa coupling necessary to achieve the unification of bottom and tau Yukawa couplings is also governed by $T_{SUSY}$, and it yields predictions for the top quark mass which are close to the quasi infrared fixed point results associated with the triviality bounds on this quantity. From the requirement of perturbative consistency of the top quark Yukawa sector of the theory, we obtain constraints on the allowed splitting of the supersymmetric spectrum, which, for certain values of the running bottom quark mass, are stronger than those ones coming from the experimental constraints on the strong gauge coupling.

hep-ph↗