2,253 research outputs found
Asymptotic Helicity Conservation in SUSY
We summarize the extensive work started in ref.1, according to which total
helicity is conserved for any two-to-two process, at sqrt{s} larger than
M_{SUSY} and fixed angles, in any SUSY extension of SM. Asymptotically the
theorem is exact. But it may also have important implications at lower energies
sqrt{s} close to M_{SUSY}. Up to now, these have been investigated to 1loop
electroweak (EW) order for the processes ug to d W+, sd_L chi+; as well as the
17 gg to HH', and the 9 gg to VH processes, where H,H' denote Higgs or
Goldstone bosons, and V=Z, W.Comment: 4 pages, 2 figures,Talk presented by GJG at the meeting on the
"Standard Model and beyond and the Standard Cosmology", held at Corfu
(Greece), during August 30 - September 6, 200
About helicity conservation in gauge boson scattering at high energy
We remark that the high energy gauge boson scattering processes involving
two-body initial and final states, satisfy certain selection rules described as
helicity conservation of the \underline{gauge boson} amplitudes (GBHC). These
rules are valid at Born level, as well as at the level of the leading and
sub-leading 1-loop logarithmic corrections, in both the Standard Model (SM) and
the Minimal Supersymmetric Standard Model (MSSM). A "fermionic equivalence"
theorem is also proved, which suggests that GBHC is valid at all orders in MSSM
at sufficiently high energies, where the mass suppressed contributions are
neglected.Comment: 7 pages, 2 figures, version to appear in Phys. Rev. Letter
The processes of gluon fusion producing chargino or neutralino pairs at high energies
According to the helicity conservation (HCns) theorem, the sum of the
helicities should be conserved, in any 2-to-2 processes in MSSM with R-parity
conservation, at high energies; i.e. all amplitudes violating this rule, must
vanish asymptotically. The realization of HCns in gluon-fusion to charginos or
neutralinos is studied, at the one loop electroweak order (EW), and simple high
energy expressions are derived for the non-vanishing helicity conserving (HC)
amplitudes. These are very similar to the corresponding expressions for derived before. Asymptotic relations among
observable unpolarized cross sections for many such processes are then
obtained, some of which may hold at LHC-type energies.Comment: Extended version to appear in International Journal of Modern Physics
A 21 page
Unitarity Constraints for Transverse Gauge Bosons at LEP and Supercolliders
Using asymptotic helicity amplitudes for Vector-Vector, Vector-Higgs and
Higgs-Higgs scattering, we establish the unitarity constraints on the
conserving and depending interactions, which at sufficiently high
energies may create strong forces among the transverse vector boson and Higgs
states. We then derive upper bounds for the couplings of these interactions,
which depend on the high energy scale where unitarity is saturated. If \eg\,
unitarity is saturated at 1TeV, then \lambda_W \lsim 0.12 is obtained. The
implied relations between the present and future LEP results, and the possible
observations of strong effects at supercolliders, are also discussedComment: 11 pages,postscript file of 1 figure appended at the end of the latex
file (e-mail [email protected] PM/93-37 THES-TP 93/1
Tests of Higgs Boson Couplings at a mu+mu- Collider
We investigate the potential of a muon collider for testing the presence of
anomalous Higgs boson couplings. We consider the case of a light (less than
) Higgs boson and study the effects on the Higgs branching ratios and
total width, which could be induced by the non standard couplings created by a
class of dim=6 gauge invariant operators
satisfying the constraints imposed by the present and future hadronic and
colliders. For each operator we give the minimal value of the
integrated luminosity needed for the muon collider () to
improve these constraints. Depending on the operator and the Higgs mass, this
minimal luminosity lies between and .Comment: 18 pages and 4 figures; version to be published in Phys. Rev.D.
e-mail: [email protected]
A Model-independent Description of New Physics effects in e+e- to t tbar
We study the potential of a future collider for the search of
anomalous gamma t t bar and Z t t bar couplings, assuming that CP-invariance
holds. This is done in a model-independent way, considering that all six
possible couplings do appear. Two experimental situations are envisaged, with
and without electron beam polarization. Observability limits in the form of
domains in the 6-dimensional parameter space are established. Illustrations for
specific constrained models are also presented and implications for new physics
searches are discussed.Comment: 26 pages and 5 figures. e-mail: [email protected]
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