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The complex Busemann-Petty problem asks whether origin symmetric convex bodies in $\C^n$ with smaller central hyperplane sections necessarily have smaller volume. We prove that the answer is affirmative if $n\le 3$ and negative if $n\ge 4.$, Comment: 18 pages

We present a detailed and complete calculation of the gluino and scalar quarks contribution to the flavour-changing top quark decay into a charm quark and a photon, gluon, or a Z boson within the minimal supersymmetric standard model including flavour changing gluino-quarks-scalar quarks couplings in the right-handed sector. We compare the results with the ones presented in an earlier paper where we considered flavour changing couplings only in the left-handed sector. We show that these new couplings have important consequences leading to a large enhancement when the mixing of the scalar partners of the left- and right-handed top quark is included. Furthermore CP violation in the flavour changing top quark decay will occur when a SUSY phase is taken into account., Comment: 14 pages, latex, 3 figures

We present a detailed and complete calculation of the doubly charged Higgsino contribution to the decays mu--> e photon and mu--> 3e and to the anomalous magnetic moment of the muon within the left-right supersymmetric model. We include the mixing of the scalar partners of the left and right handed leptons, and show that it leads to a strong enhancement of the decay modes in certain scenarios. We find that the contribution of the doubly charged Higgsino can be close to the known experimental values and are reachable by future experiments., Comment: 13 pages, latex, 1 figure

We present an overview of the loop corrections to the mass difference $\Delta m_{B_d^0}/ m_{B_d^0}$ within the minimal supersymmetric standard model. We include the complete mixing matrices of the charginos and neutralinos as well as of the scalar partners of the left and right handed third generation quarks. We show that the SUSY contribution to the mass difference in the $B_d^0$ system is comparable to the Standard Model one and can be even larger for the charged Higgs contribution and for a certain supersymmetric parameter space., Comment: 5 pages, Latex, 3 figures included, uses espcrc2.sty (Talk presented by H. K\"onig at the 2nd International Conference on Hyperons, Charm and Beauty Hadrons, Montr\'eal, Qu\'ebec, Canada, 27-30 August 1996.)

The possibility of studying superstring inspired \mbox{${\rm E}_6$} phenomenology at high energy hadron colliders is investigated. A very simple low energy rank-5 Supersymmetric (N=1) model is considered, which consists of three scalar-Higgses, $H^0_{i=1,2,3}\,$, two charged-Higgses, $H^\pm\,$, one pseudo-scalar-Higgses, $P^0\,$, and an extra vector boson, the $Z^\prime$. The production of charged heavy leptons pairs, $L^+L^-\,$, by gluon-gluon fusion and Drell-Yan mechanisms is discussed. For gluon-gluon fusion an enhancement in the parton level cross-section is expected due to the heavy (s)fermion loops which couple to the gluons. This mechanism is expected to dominate over Drell-Yan for $L^+L^-$ invariant masses above the $Z^\prime$ mass., Comment: 65 pages, LaTeX file, 26 figures, also available at http://www.physics.carleton.ca/~boyce/papers/prd96.ps

We investigate the possibility of studying E$_6$ phenomenology at high energy hadron colliders. The production of heavy leptons pairs {\it via} a gluon-gluon fusion mechanism is discussed. An enhancement in the parton level cross-section is expected due to the heavy (s)fermion loops which couple to the gluons., Comment: MRST96 Conf. Proc., 10 pages, LaTeX type, macros sprocl.tex included, copy available at http://www.physics.carleton.ca/~boyce/papers/mrst96.ps

We present a detailed and complete calculation of the neutralino contribution to the mass difference $\Delta m_{B_d^0}/m_{B_d^0}$\ within the MSSM. We include the complete mixing matrices of the neutralinos and of the scalar partners of the left and right handed bottom quark. We find that the neutralino contribution is generally small but can be of the same order of the chargino contribution and much larger than that of the gluino over a small range of $m_S$, given $m_{g_2}$ and $\mu$ and for $\tan\beta\sim 50$., Comment: 8 pages, plain tex, 2 figures, not included, available under request

We calculate the contribution of second generation scalar leptoquarks to the anomalous magnetic moment of the muon (AMMM). In the near future, E-821 at Brookhaven will reduce the experimental error on this parameter to $\Delta a_\mu^{\rm exp}<4\times 10^{-10}$, an improvement of 20 over its current value. With this new experimental limit we obtain a lower mass limit of $m_{\Phi_L}>186$\ GeV for the second generation scalar leptoquark, when its Yukawa-like coupling $\lambda_{\Phi_L}$\ to quarks and leptons is taken to be of the order of the electroweak coupling $g_2$., Comment: 5 pages, plain tex, 1 figure (not included available under request)

We present a detailed and complete calculation of the loop corrections to the mass difference $\Delta m_{B_d^0}/m_{B_d^0}$. We include charginos and scalar up quarks as well as gluinos and scalar down quarks on the relevant loop diagrams. We include the mixings of the charginos and of the scalar partners of the left and right handed quarks. We find that the gluino contribution to this quantity is important with respect to the chargino contribution only in a small part of phase space: mainly when the gluino mass is small ($\sim$ 100 GeV) and the symmetry-breaking parameter $m_S$ is below 300 GeV. This contribution is also important for very large values of $\tan\beta$ ($\sim$ 50) irrespective of the other parameters. Otherwise, the chargino contribution dominates vastly and can be roughly as large as that of the Standard Model. We also present the contribution of the charged Higgs to the mass difference $\Delta m_{B_d^0}/m_{B_d^0}$\ in the case $m_b\tan\beta\ll m_t\cot\beta$. This last contribution can be larger than the Standard Model contribution for small values of the Higgs mass and small values of $\tan\beta$., Comment: 9 pages, plain tex, 4 figures (not included, available under request)

We present a detailed calculation of the contributions of charginos, scalar quarks, and charged Higgs boson to the $K^+\rightarrow \pi^+\nu\overline\nu$\ and $K^0_L\rightarrow\mu^+\mu^-$\ decays. We include mixings: that of charginos and that of the scalar partners of the left and right handed top quark. We find that the box contribution to the amplitudes is much smaller than the penguin contribution, which can be $\sim$10\% of the Standard Model contribution, even for relatively large SUSY masses. The charged Higgs contribution can be as large as 25\% of the SM contribution in the first decay and as much as 40\% of the SM contribution in the second decay., Comment: 10 pages plain tex, 8 figures (not included available under request).

We present the results of the gluino and scalar quarks contribution to the flavour changing top quark decay into a charm quark and a photon, gluon or a $Z^0$\ boson within the minimal supersymmetric standard model. We include the mixing of the scalar partners of the left and right handed top quark. This mixing has several effects, the most important of which are to greatly enhance the c Z decay mode for large values of the soft SUSY breaking scalar mass $m_S$\ and to give rise to a GIM--like suppresion in the c $\gamma$\ mode for certain combinations of parameters., Comment: UQAM-PHE-94/08, plain tex, 7 pages, 5 figures not included, available under request via mail or fax

Using effective-lagrangian techniques we perform a systematic survey of the lowest-dimension effective interactions through which heavy physics might manifest itself in present experiments. We do not restrict ourselves to special classes of effective interactions (such as `oblique' corrections). We compute the effects of these operators on all currently well-measured electroweak observables, both at low energies and at the $Z$ resonance, and perform a global fit to their coefficients. Despite the fact that a great many operators arise in our survey, we find that most are quite strongly bounded by the current data. We use our survey to systematically identify those effective interactions which are {\it not} well-bounded by the data -- these could very well include large new-physics contributions. Our results may also be used to efficiently confront specific models for new physics with the data, as we illustrate with an example., Comment: plain TeX, 68 pages, 2 figures (postscript files appended), McGill-93/12, NEIPH-93-008, OCIP/C-93-6, UQAM-PHE-93/08, UdeM-LPN-TH-93-155

We calculate supersymmetric QCD corrections (squark/gluino loops) to quark pair production in e+ e- annihilation, allowing for mixing between left- and right-handed squarks and taking into account the effects of nonzero quark masses. Corrections to the Z boson partial widths are generally small and positive, except in the case of large b-squark mixing, where they become negative. At high-energy e+ e- colliders, larger corrections to the total cross sections are possible. Corrections to forward-backward asymmetries are negligible except possibly for top quarks, where they are sensitive to t-squark mixing. We also comment on the possibility that the gluino mass is only a few GeV., Comment: 17 pages, LaTeX with EQUATION.STY, 4 figures available on request; MAD/PH/754