950 research outputs found
Present day status and future of nature conservation in the Republic of Malawi
When Malawi (formerly Nyasaland) became independent in 1964 the status and future of its game reserves were in jeopardy. The former administration had adopted a policy of benign neglect towards the country's wildlife areas (Anon 1963), and the remnants of the Department of Game, Fish and Tsetse Control had been absorbed by the Forestry Department in 1963. Fortunately the Life President of Malawi, Dr H Kamuzu Banda, took a strong interest in wildlife conservation and it was only his personal intervention, and the advent of independence, that saved the former Lengwe Game Reserve from deproclamation (Hayes 1967) as planned by the colonial administration. With the Life President's encouragement and the dedicated efforts of the staff responsible for wildlife, the tide which had been running strongly against nature conservation was turned, culminating in the establishment of a separate Department of National Parks and Wildlife only a decade after independence
Connections between epsilon'/epsilon and Rare Kaon Decays in Supersymmetry
We analyze the rare kaon decays , , and in conjunction
with the CP violating ratio in a general class of
supersymmetric models in which - and magnetic-penguin contributions can be
substantially larger than in the Standard Model. We point out that radiative
effects relate the double left-right mass insertion to the single left-left
one, and that the phenomenological constraints on the latter reflect into a
stringent bound on the supersymmetric contribution to the penguin. Using
this bound, and those coming from recent data on we find
{\rm BR}(K_L \to \pi^0 \nu \bar \nu)\lsim 1.2\cdot 10^{-10}, {\rm BR}(K^+
\to \pi^+ \nu \bar \nu)\lsim 1.7\cdot 10^{-10}, {\rm BR}(K_L \to \pi^0 e^+
e^-)_{\rm dir}\lsim 2.0\cdot 10^{-11}, assuming the usual determination of the
CKM parameters and neglecting the possibility of cancellations among different
supersymmetric effects in . Larger values are possible, in
principle, but rather unlikely. We stress the importance of a measurement of
these three branching ratios, together with improved data and improved theory
of , in order to shed light on the realization of various
supersymmetric scenarios. We reemphasize that the most natural enhancement of
, within supersymmetric models, comes from chromomagnetic
penguins and show that in this case sizable enhancements of can also be expected.Comment: 40 pages, 5 figure
Supersymmetric models with minimal flavour violation and their running
We revisit the formulation of the principle of minimal flavor violation (MFV)
in the minimal supersymmetric extension of the standard model, both at moderate
and large tan(beta), and with or without new CP-violating phases. We introduce
a counting rule which keeps track of the highly hierarchical structure of the
Yukawa matrices. In this manner, we are able to control systematically which
terms can be discarded in the soft SUSY breaking part of the Lagrangian. We
argue that for the implementation of this counting rule, it is convenient to
introduce a new basis of matrices in which both the squark (and slepton) mass
terms as well as the trilinear couplings can be expanded. We derive the RGE for
the MFV parameters and show that the beta functions also respect the counting
rule. For moderate tan(beta), we provide explicit analytic solutions of these
RGE and illustrate their behaviour by analyzing the neighbourhood (also
switching on new phases) of the SPS-1a benchmark point. We then show that even
in the case of large tan(beta), the RGE remain valid and that the analytic
solutions obtained for moderate tan(beta) still allow us to understand the most
important features of the running of the parameters, as illustrated with the
help of the SPS-4 benchmark point.Comment: plain latex, 38 pages and 5 figures Eq. (12) corrected and one
reference added, conclusions unchanged. Published versio
Uplifted supersymmetric Higgs region
We show that the parameter space of the Minimal Supersymmetric Standard Model
includes a region where the down-type fermion masses are generated by the
loop-induced couplings to the up-type Higgs doublet. In this region the
down-type Higgs doublet does not acquire a vacuum expectation value at tree
level, and has sizable couplings in the superpotential to the tau leptons and
bottom quarks. Besides a light standard-like Higgs boson, the Higgs spectrum
includes the nearly degenerate states of a heavy spin-0 doublet which can be
produced through their couplings to the quark and decay predominantly into
\tau^+\tau^- or \tau\nu.Comment: 14 pages; Signs in Eqns. (3.1) and (4.2) corrected, appendix include
Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2
An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY)
SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in
which the parameter space is restricted by some experimental constraints
including Br(b to s gamma) and muon g-2. The bottom-tau unification can be
accommodated to the measured branching ratio Br(b to s gamma) if superparticle
masses are relatively heavy and higgsino mass parameter \mu is negative. On the
other hand, if we take the latest muon g-2 data to require positive SUSY
contributions, then wrong-sign threshold corrections at SUSY scale upset the
Yukawa unification with more than 20 percent discrepancy. It has to be
compensated by superheavy threshold corrections around the GUT scale, which
constrains models of flavor in SUSY GUT. A pattern of the superparticle masses
preferred by the three requirements is also commented.Comment: 21pages, 6figure
Neutralino Dark Matter, b-tau Yukawa Unification and Non-Universal Sfermion Masses
We study the implications of minimal non-Universal Boundary Conditions in the
sfermion Soft SUSY Breaking (SSB) masses of mSUGRA. We impose asymptotic b-tau
Yukawa coupling Unification and we resort to a parameterization of the
deviation from Universality in the SSB motivated by the multiplet structure of
SU(5) GUT. A set of cosmo-phenomenological constraints, including the recent
results from WMAP, determines the allowed parameter space of the models under
consideration. We highlight a new coannihilation corridor where
neutralino-sbottom and neutralino-tau sneutrino-stau coannihilations
significantly contribute to the reduction of the neutralino relic density.Comment: 38 pages, 27 Figures, Latex; Version accepted for publication in PR
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