Scalar parameters in effective gauge theories

We apply Weinberg's method of effective gauge theories to the study of light scalar masses and coupling constants, in a simplified model with two widely separated mass scales. No improvement of the unnaturalness in the Higgs sector is seen.     

No-scale supersymmetric standard model

We propose a class of supergravity models coupled to matter in which the scales of supersymmetry breaking and of weak gauge symmetry breaking are both fixed by dimensional transmutation, not put in by hand. The models have a flat potential with zero cosmological constant before the evaluation of weak radiative corrections which determine $\text{m}\text{3}\text{2}\text{, m}{}_{\mathrm{<mtext>W</mtext>}}\text{=}\text{exp}\text{[}\text{?O(1)}\text{α}{}_{\mathrm{<mtext>t</mtext>}}\text{]m}{}_{\mathrm{<mtext>p</mtext>}}\text{:α}{}_{\mathrm{<mtext>t</mtext>}}\text{= O(α)}$. These models are consistent with all particle physi cs and cosmological constraints for top quark masses in the range 30 GeV < m_t < 100 GeV.     

Low-energy behaviour of realistic locally-supersymmetric grand unified theories

The recently proposed cosmologically acceptable N=1 supergravity models based on the SU(5) unification group define unambigously the minimal particle content of the theory. This fact allows us to determine quite precisely their low-energy behaviour. The SU(2)×U(1) breaking to U(1)_e.m. is a consequence of radiative corrections of the supergravity induced soft breaking terms. The proposed mechanism (which is model independent) introduces naturally a hierarchy between the M_W and M_X scales. Calculating the low-energy effective potential we shot that a corrects SU(2)×U(1) breaking is obtained without any limit (except the experimental one) on the top-quark mass. The masses of the supersymmetric partners of mater and gauge fermions can be low and consequently accessible experimentally (sleptons, s quarks, gauginos $\text{? 20–50}\text{GeV}$). A neutral Higgs is also predicted wirth a mass $\text{m}{}_{\mathrm{H}}\text{?O(5)}\text{GeV}$. In addition, we show that if m_t?45 GeV, the gravitino and gluino masses are bounded from below by $\text{10}\text{GeV}\text{? m}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{and}\text{15}\text{GeV}\text{? m}{}_{\mathrm{<mtext>gluino</mtext>}}$. The values of sin²θ_W (in the two-loop approximation) and the $\text{m}{}_{\mathrm{<mtext>b</mtext>}}\text{m}{}_{\mathrm{\tau }}$ ratio predicted are in very good agreement with the experimentally measured values.     

On the gauge hierarchy in the SU(5) model

It is explicitly shown that in the SU(5) prototype for grand unified theories, the decoupling of superheavy gauge bosons as well as Higgses from the light gauge particles is complete and therefore a gauge interaction hierarchy is possible.     

Dissipative Liouville cosmology: A case study

We consider solutions of the cosmological equations pertaining to a dissipative, dilaton-driven off-equilibrium Liouville cosmological model, which may describe the effective field theoretic limit of a non-critical string model of the Universe. The non-criticality may be the result of an early-era catastrophic cosmic event, such as a big-bang, brane-world collision, etc. The evolution of the various cosmological parameters of the model are obtained, and the effects of the dilaton and off-shell Liouville terms, including briefly those on relic densities, which distinguish the model from conventional cosmologies, are emphasised.     

Implications of the pseudo-scalar Higgs boson in determining the neutralino dark matter

In the framework of the constrained minimal supersymmetric standard model (CMSSM) we discuss the impact of the pseudo-scalar Higgs boson in delineating regions of the parameters which are consistent with cosmological data and E821 data on the anomalous magnetic moment of the muon. For the large values of the parameter , cosmologically allowed corridors of large are opened, due to the s-channel pseudo-scalar exchange in the pair annihilation of the lightest of the neutralinos to or , which dominates in this region. However, no such corridors are found for values . Combining cosmological and E821 data puts severe upper limits on the sparticle masses. We find that at LHC, but even at a linear collider with center of mass energy GeV, such as TESLA, supersymmetry can be discovered, if it is based on the CMSSM. Received: 22 July 2001 / Revised version: 13 November 2001 / Published online: 18 January 2002     

Impossibility of perturbative restoration of F type spontaneously broken supersymmetry

We prove that higher order corrections cannot restore supersymmetry if it is spontaneously broken at the tree level by an F type mechanism even if not all terms consistent with the symmetries have been included.     

Isospin decomposition of 0+ → 2+ and 0+ → 3− transition matrix elements by Coulomb nuclear interference observed in inelastic α-scattering from the even Zr isotopes

Coulomb-nuclear interference in inelastic scattering of 35.4 MeVα-particles from the stable even Zr isotopes was studied. In the framework of a collective DWBA analysis isoscalar and electromagnetic transition rates for low lying 2⁺ and 3^? states were derived. The experimentalB (E2) values are in good agreement with results obtained by purely electromagnetic methods. The deducedM _n /M _p ratios of the 2 ₁ ⁺ levels exhibit a surprisingly large increase with increasing neutron number.