780 research outputs found
Supersymmetric virtual effects in heavy quark pair production at LHC
We consider the production of heavy () quark pairs at proton colliders
in the theoretical framework of the MSSM. Under the assumption of a
"moderately" light SUSY scenario, we first compute the leading logarithmic MSSM
contributions at one loop for the elementary processes of production from a
quark and from a gluon pair in the 1 TeV c.m. energy region. We show that in
the initial gluon pair case (dominant in the chosen situation at LHC energies)
the electroweak and the strong SUSY contributions concur to produce an enhanced
effect whose relative value in the cross sections could reach the twenty
percent size for large values in the realistic proton-proton LHC
process.Comment: 19 pages and 8 figures; version to appear in Phys. Rev.
Supersymmetry Tests from a Combined Analysis of Chargino and Charged Higgs Boson Pair Production at a 1 TeV Linear Collider
We consider the production of chargino and charged Higgs boson pairs at
future linear colliders for c.m. energies in the one TeV range. Working in the
MSSM under the assumption of a "moderately" light SUSY scenario, we compute the
leading (double) and next-to leading (linear) supersymmetric logarithmic terms
of the so-called "Sudakov expansion" at one loop. We show that a combined
analysis of the slopes of the chargino and of the charged Higgs production
cross sections would offer a simple possibility for determining for
large () values and an allowed strip in the () plane. This
could provide a strong consistency test of the considered supersymmetric model.Comment: 4 pages, 4 Encapsulated PostScript Figure
Weak Interaction Sum Rules for Polarized top-antitop Production at LHC
We consider two polarization asymmetries in the process of top-antitop
production at LHC. We show that the theoretical predictions for these two
quantities, at the strong and electroweak partonic one-loop level, are free of
QCD and QED effects. At this perturbative level we derive two sum rules, that
relate measurable quantities of top-antitop production to genuinely weak
inputs. This would allow to perform two independent tests of the candidate
theoretical model, with a precision that will be fixed by the future
experimental accuracies of the different polarization measurements. A tentative
quantitative illustration of this statement for a specific MSSM scenario is
enclosed, and a generalization to include two other future realistic
measurements is also proposed.Comment: 13 pages, 3 figures, local report number adde
Logarithmic Fingerprints of Virtual Supersymmetry
We consider the high energy behaviour of the amplitudes for production of
leptons, quarks, Higgs bosons, sleptons, squarks, gauge bosons, charginos,
neutralinos. We concentrate our discussion on the universal (process
independent) logarithmic terms which factorize the Born amplitude and which are
typically of the form [a ln(s/m^2)-ln^2(s/m^2)]. We perform a systematic
determination of the coefficient "a" for the various final states and we
emphasize the striking features which differentiate the SM and the MSSM cases.
We show that a comparison with experiments at future colliders should provide a
clean way to test the gauge and Higgs structures of the electroweak
interactions owing to the presence of sizeable (visible) virtual logarithmic
supersymmetric contributions.Comment: 11 pages e-mail: [email protected]
Complete electroweak one loop contributions to the pair production cross section of MSSM charged and neutral Higgs bosons in e+e- collisions
In this paper, we review the production cross section for charged and neutral
Higgs bosons pairs in collisions beyond the tree level, in the
framework of the Minimal Supersymmetric Standard Model (MSSM). A complete list
of formulas for all electroweak contributions at the one loop level is given. A
numerical code has been developed in order to compute them accurately and, in
turn, to compare the MSSM Higgs bosons pair production cross sections at tree
level and at the one loop level.Comment: 58 pages, 3 eps figure
Top quark production at future lepton colliders in the asymptotic regime
The production of a tt(bar) pair from lepton-antilepton annihilation is
considered for values of the center of mass energy much larger than the top
mass, typically of the few TeV size. In this regime a number of simplifications
occurs that allows to derive the leading asymptotic terms of various
observables using the same theoretical description that was used for light
quark production. Explicit examples are shown for the Standard Model and the
Minimal Supersymmetric Standard Model cases.Comment: 20 pages and 13 figures. e-mail: [email protected]
The relevance of virtual electroweak effects in the overall -channel single top production at LHC
We compute the complete one loop electroweak effects in the MSSM for the
eight processes of single top (and single antitop) production in the
-channel at hadron colliders, generalizing a previous analysis performed for
the dominant final state. The results are quite similar for all processes,
showing an impressively large Standard Model effect and a generally modest
genuine SUSY contribution in the mSUGRA scenario. The one loop effect on the
total rate is shown and the possibility of measuring it at LHC is discussed.Comment: 15 pages, 7 eps figure
Charged Higgs Production in the 1 TeV Domain as a Probe of Supersymmetric Models
We consider the production, at future lepton colliders, of charged Higgs
pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and
working in the MSSM, we show that, for c.m. energies in the one TeV range, a
one-loop logarithmic Sudakov expansion that includes an "effective" next-to
subleading order term is adequate to the expected level of experimental
accuracy. We consider then the coefficient of the linear (subleading) SUSY
Sudakov logarithm and the SUSY next to subleading term of the expansion and
show that their dependence on the supersymmetric parameters of the model is
drastically different. In particular the coefficient of the SUSY logarithm is
only dependent on while the next to subleading term depends on a
larger set of SUSY parameters. This would allow to extract from the data
separate informations and tests of the model.Comment: 18 pages and 13 figures e-mail: [email protected]
The role of universal and non universal Sudakov logarithms in four fermion processes at TeV energies: the one-loop approximation revisited
We consider the separate effects on four fermion processes, in the TeV energy
range, produced at one loop by Sudakov logarithms of universal and not
universal kind, working in the 't Hooft xi=1 gauge. Summing the various vertex
and box contributions allows to isolate two quite different terms.The first one
is a combination of vertex and box quadratic and linear logarithms that are
partially universal and partially not universal and independent of the
scattering angle theta. The second one is theta-dependent, not universal,
linearly logarithmic and only produced by weak boxes. We show that for several
observables, measurable at future linear e+e- colliders (LC, CLIC), the role of
the latter term is dominant and we discuss the implications of this fact for
what concerns the reliability of a one-loop approximation.Comment: 22 pages and 13 figures; version to appear in Phys.Rev.D. e-mail:
[email protected]
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