265 research outputs found
Radiative Electroweak Breaking with Pseudogoldstone Higgs Doublets
We consider a realistic example of supersymmetric grand unification based on
in which the electroweak (EW) higgs
doublets are `light' as a consequence of the `pseudogoldstone' mechanism. We
discuss radiative EW breaking in this model, exploring in particular the
`small' (order unity) and `large' regions by
studying the variations of , where
are the well known MSSM parameters evaluated at the GUT scale.
For sufficiently close to unity the quantity can be of order
unity, but the converse is not always true.Comment: 18 pages plain LaTeX (to be run twice) and 11 figures available
separately from uuencoded file
Research News: Direct observation of neutrino oscillations at the Sudbury Neutrino Observatory
A brief description of the path-breaking evidence for the observation of neutrino oscillations at the Sudbury Neutrino Observatory is presented and the experimental principles and theory thereof are briefly discussed
Infrared Fixed Point Structure in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation
We study in detail the renomalization group evolution of Yukawa couplings and
soft supersymmetry breaking trilinear couplings in the minimal supersymmetric
standard model with baryon and lepton number violation. We obtain the exact
solutions of these equations in a closed form, and then depict the infrared
fixed point structure of the third generation Yukawa couplings and the highest
generation baryon and lepton number violating couplings. Approximate analytical
solutions for these Yukawa couplings and baryon and lepton number violating
couplings, and the soft supersymmetry breaking couplings are obtained in terms
of their initial values at the unification scale. We then numerically study the
infrared fixed surfaces of the model, and illustrate the approach to the fixed
points.Comment: 16 pages REVTeX, figures embedded as epsfigs, replaced with version
to appear in Physical Review D, minor typographical errors eliminated and
references reordered, figures correcte
Forward dispersion relations and Roy equations in pi-pi scattering
We review results of an analysis of pipi interactions in S, P and D waves for
two-pion effective mass from threshold to about 1.4 GeV. In particular we show
a recent improvement of this analysis above the K anti-K threshold using more
data for phase shifts and including the S0 wave inelasticity from pipi -> K
anti-K. In addition, we have improved the fit to the f2(1270) resonance and
used a more flexible P wave parametrization above the K anti-K threshold and
included an estimation of the D2 wave inelasticity. The better accuracy thus
achieved also required a refinement of the Regge analysis above 1.42 GeV. We
have checked that the pipi scattering amplitudes obtained in this approach
satisfy remarkably well forward dispersion relations and Roy's equations.Comment: 6 pages, invited talk to the IV International Conference on Quarks
and Nuclear Physics QNP06, Madrid 5th-10th June 200
Review of chiral perturbation theory
A review of chiral perturbation theory and that of recent developments on the
comparison of its predictions with experiment is presented. Some interesting
topics with scope for further elaboration are touched upon.Comment: 7 pages in revtex, Invited talk at the workshop, QCD2002, Indian
Institute of Technology, Kanpur, November 18-22, 2002, to appear in the
proceeding
Infrared regularization with spin-3/2 fields
We present a Lorentz-invariant formulation of baryon chiral perturbation
theory including spin-3/2 fields. Particular attention is paid to the
projection on the spin-3/2 components of the delta fields. We also discuss the
nucleon mass and the pion-nucleon sigma term.Comment: 9 pp, 1 fi
Zeroing In On the Top Quark, LSP and Scalar Higgs Masses
We estimate the top quark, lightest sparticle (LSP) and scalar higgs masses
within a supersymmetric grand unified framework in which and the electroweak symmetry is radiatively broken. The requirement
that the calculated quark mass lie close to its measured value, together
with the cosmological constraint , fixes the top quark
mass to be . The LSP (of bino purity
has mass . In the scalar
higgs sector the CP-odd scalar mass . With
, as suggested by the decay , we find and .Comment: 14 pages in plain LaTeX, BA-93-25, PRL-TH-93/
Model independent bounds on the modulus of the pion form factor on the unitarity cut below the threshold
We calculate upper and lower bounds on the modulus of the pion electro
magnetic form factor on the unitarity cut below the inelastic
threshold, using as input the phase in the elastic region known via the
Fermi-Watson theorem from the -wave phase shift, and a suitably
weighted integral of the modulus squared above the inelastic threshold. The
normalization at , the pion charge radius and experimental values at
spacelike momenta are used as additional input information. The bounds are
model independent, in the sense that they do not rely on specific
parametrizations and do not require assumptions on the phase of the form factor
above the inelastic threshold. The results provide nontrivial consistencychecks
on the recent experimental data on the modulus available below the
threshold from annihilation and -decay experiments. In
particular, at low energies the calculated bounds offer a more precise
description of the modulus than the experimental data.Comment: 12 pages, 23 figures, prepared using EPJ style files; v2 corresponds
to proofs version to appear in European Physical Journal C; extended
discussion compared to v
The isospin symmetry breaking effects in decays
The Fermi-Watson theorem is generalized to the case of two coupled channels
with different masses and applied to final state interaction in
decays. The impact of considered effect on the phase of the scattering
is estimated and shown that it can be crucial for scattering lengths extraction
from experimental data on decays
Low energy consequences from supersymmetric models with left-right symmetry
We consider several low energy consequences arising from a class of
supersymmetric models based on the gauge groups and in which the gauge
hierarchy and problems have been resolved. There are important
constraints on the MSSM parameters , and
, and we discuss how they are reconciled with radiative electroweak
breaking. We also consider the ensuing sparticle and Higgs spectroscopy, as
well as the decays and . The latter process
may be amenable to experimental tests through an order of magnitude increase in
sensitivity.Comment: 17 pages, latex2
- …