arXiv subjects
Publications and source records attributed to L. Clavelli.
We deduce the gluino contribution to the three-loop QCD quark mass anomalous dimension function within the minimal supersymmetric Standard Model (MSSM) from its standard QCD expression. This work is a continuation of the program of computation of MSSM renormalization group functions.
Depending on their masses, Supersymmetric particles can affect various measurements in Z decay. Among these are the total width (or consequent extracted value of $α_s$), enhancement or suppression of various flavors, and left-right and forward-backward asymmetries. The latter depend on squark mass splittings and are, therefore, a possible test of the Supergravity related predictions. We calculate leading order corrections for these quantities considering in particular the case of light photino and gluino where the SUSY effects are enhanced. In this limit the effect on $α_s$ is appreciable, the effect on $R_b$ is small, and the effect on the asymmetries is extremely small.
The Fermilab top quark analysis is heavily dependent on the assumption of standard model backgrounds only. In the light gluino scenario, the stop quarks lie near the top in mass and their decays can influence the resulting top quark mass by an amount that is not small relative to the currently quoted errors. Several slight anomalies in the top quark analysis find a natural explanation in the light gluino case.
In the light gluino scenario, squarks in the 100 GeV mass region can be copiously produced at the Tevatron without a second heavy particle. Their subsequent dijet decay into quark plus gluino leads to non-scaling structure in the inclusive jet X_T distribution. The expected behavior is similar to recent observations.
We deduce the gluino contribution to the three-loop QCD βfunction within the minimal supersymmetric Standard Model (MSSM) from its standard QCD expression. The result is a first step in the computation of the full MSSM three-loop βfunction. In addition, in the case of a light gluino it provides the strong three-loop SUSY correction to the extrapolation of the strong coupling constant from the low energy regime to the Z region and up to the squark threshold.
In the light gluino variant of the minimal supersymmetric model gluino pairs can be readily produced in collider experiments even if the squarks are arbitrarily heavy. This enhances the jet transverse energy distributions. In addition the slower running of the strong coupling constant in the presence of light gluinos leads to a further enhancement at higher transverse energies relative to the standard $QCD$ expectations. Finally, the enhanced squark gluino production would lead to a Jacobian peak in the $E_T$ distribution at about $M_{\tilde Q}/2$. These effects are of about the right magnitude to explain anomalies observed by the $CDF$ and $D0$ collaborations.
We consider single squark production in $p\overline{p}$ collisions at $\sqrt{s}=1800$ Gev in the light gluino scenario, where production is dominated by the parton subprocess $qg\rightarrow \tilde{q}\tilde{g}\rightarrow q\tilde{g}\tilde{g}$. Computed are the total production cross-sections as well as the contribution of such production to the dijet mass distribution. We compare our cross-sections to the experimental data from the CDF collaboration with integrated luminosity of $19 pb^{-1}$.
Flavor changing interactions of the gluino allow the $b$ quark to decay into the strange quark plus a gluino pair if the gluino is in the ultra low mass window below 1 GeV. In this case the enhancement of the nonleptonic $b$ decay could explain the anomalous semileptonic branching ratio.
Going beyond the theta function approximation we discuss supersymmetric unification of gauge couplings with exact decoupling of light and heavy particles at energy scales below their masses. We find that the Minimal SUSY model is strongly disfavored while the Missing Doublet Model survives with GUT scale masses rising into the $10^{18}$ GeV region.
We discuss the case for a light gluino and the mutual impact of this possibility with the Fermilab top quark candidates
We discuss the anomaly in the $b$ branching ratio of the $Z$ in the context of the light gluino scenario.
We investigate correlations among various parameters in the solution space of minimal supersymmetric grand unification. In particular the extent to which the top quark Yukawa coupling exhibits fixed point behavior is discussed and we compare various analytic approximations to its value at the top mass with its exact value in numerical solutions.\\ $^*$ Talk presented at the Workshop on Yukawa Couplings and the Origin of Mass, Gainesville, Florida, Feb. 11-13, 1994\\
We analyze the implications of the light gluino scenario for the unification of gauge and Yukawa couplings within the minimal supersymmetric standard model. Within this scheme all fermionic supersymmetric particles are naturally light, while the scalar partners of quarks and leptons, together with the heavy Higgs doublet may be heavy. This implies both a bound on $\tanβ< 2.3$, in order to fulfill the experimental constraints on the chargino masses, and a strong correlation between $\sin^2θ_W(M_Z)$ and $α_3(M_Z)$, due to the suppression of the supersymmetric threshold corrections to the low energy values of the gauge couplings. Assuming the scalar sparticles to be lighter than 10 TeV, the physical top quark mass is constrained to be 145 GeV $< M_T <$ 210 GeV for $\tanβ>1$, while the strong gauge coupling values, $0.122\leqα_3(M_Z) \leq 0.133$, are in good agreement with the measured LEP ones. We also show that a relaxation of some of the conventional assumptions is necessary in order to achieve radiative breaking of the electroweak symmetry within the grand unification scheme.
The relation of the strong coupling constant as measured in tau decay to other low energy determinations is considered with special attention to its impact on the question of the possible existence of light gluinos.
The impact of the new tau decay data on the various $τ$ puzzles and on the possibility of approximate supersymmetry is discussed. The most economical solution of the problems in $τ$ decay and that favored by recent new data supports the existence of gluinos below one GeV.
We investigate the possibility that the difference between the measurements of $α_3(M_Z)$ from the hadronic branching ratio of the $Z^0$ and the world average of other measurements is due to the decay of the $Z^0$ into quark, anti-squark, and gluino. Consequences for supersymmetry breaking models are discussed.
Assuming that perturbative QCD is the dominant explanation for the narrowness of the vector quarkonia, we perform a $χ^2$ minimization analysis of their hadronic decays as a function of two parameters, the mass of the gluino and the value of $α_3(M_Z)$. A value below 1 GeV for the gluino mass is strongly preferred. Consequences for SUSY breaking scenarios are discussed.