688 research outputs found
Towards Higgs boson production in gluon fusion to NNLO in the MSSM
We consider the Higgs boson production in the gluon-fusion channel to
next-to-next-to-leading order within the Minimal Supersymmetric Standard Model.
In particular, we present analytical results for the matching coefficient of
the effective theory and study its influence on the total production cross
section in the limit where the masses of all MSSM particles coincide. For
supersymmetric masses below 500 GeV it is possible to find parameters leading
to a significant enhancement of the Standard Model cross section, the
-factors, however, change only marginally.Comment: 20 pages; v2: modification of discussion of numerical effect, version
to appear in EPJC; v3: eq.(18) corrected, minor correction
NLO corrections to differential cross sections for pseudo-scalar Higgs boson production
We have computed the full next-to-leading (NLO) QCD corrections to the
differential distributions for pseudo-scalar Higgs (A)
production at large hadron colliders. This calculation has been carried out
using the effective Lagrangian approach which is valid as long as the mass of
the pseudo-scalar Higgs boson and its transverse momentum do
not exceed the top-quark mass . The shape of the distributions hardly
differ from those obtained for scalar Higgs (H) production because, apart from
the overall coupling constant and mass, there are only small differences
between the partonic differential distributions for scalar and pseudo-scalar
production. Therefore there are only differences in the magnitudes of the
hadronic differential distributions which can be mainly attributed to the
unknown mixing angle describing the pseudo-scalar Higgs coupling to the
top quarks.Comment: 9 pages, LaTeX, 3 Postscript figures In the previous version we have
forgotten to include contributions which arrise from interferences between
graphs containing vertices corresponding to the operator in Eq. (3)
with graphs originating from the operator . These interferences occur
because of the prescription for the Levi-Civita tensor given in our paper.
These extra contributions are added to Eqs. (19) and (20). Numerically they
are completely negligible so that the figures are not altere
Polarization in Top Quark Production and Decay near Threshold
Theoretical results are presented for top quarks produced in annihilation of
polarized electrons on positrons. Polarization studies for pairs near
threshold are free from hadronization ambiguities. This is due to the short
lifetime of the top quark. Semileptonic decays are discussed as well as their
applications in studying polarization dependent processes involving top quarks.
The Green function formalism is applied to production at future
colliders with polarized beams. Lippmann--Schwinger equation is solved
numerically for the QCD chromostatic potential given by the two-loop formula at
large momentum transfers and Richardson ansatz at intermediate and small ones.
The polarization dependent momentum distributions of top quarks and their decay
products are calculated.Comment: 6 pages, LaTex (uses epsf.sty, 2 figures appended as uuencoded ps
files). The complete paper, including figures, is also available via
anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as
/ttp94-24/ttp94-24.ps, or via www at
http://ttpux2.physik.uni-karlsruhe.de/preprints.html
Exploiting the WH/ZH symmetry in the search for New Physics
We suggest to isolate the loop-induced gluon-initiated component ()
for associated production by using the similarity of the Drell-Yan-like
component for production to the process. We argue that the
cross-section ratio of the latter two processes can be predicted with high
theoretical accuracy. Comparing it to the experimental cross-section
ratio should allow to probe for New Physics in the component at the
HL-LHC. We consider typical BSM scenarios in order to exemplify the effect they
would have on the proposed observable.Comment: 22 pages, 10 figures. v2: Minor changes; matches published versio
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