524 research outputs found
Gluon Fragmentation to Gluonium
The fragmentation of gluons to gluonium states is analyzed qualitatively in
the non-perturbative region. The convolution of this mechanism with
perturbative gluon radiation leaves us with a hard component in the
fragmentation of gluon to gluonium.Comment: 6 pages with 2 figures, LaTe
Chargino Pair Production at Colliders with Polarized Beams
The chargino system can be reconstructed completely
in collisions. By measuring the total cross sections and the
asymmetries with polarized beams in , the chargino masses and the gaugino-higgsino mixing angles of these
states can be determined very accurately. If only the lightest charginos
are kinematically accessible, transverse beam polarization
is needed to determine the mixing angles unambiguously. From these observables
the fundamental SUSY parameters can be derived: the SU(2) gaugino mass ,
the modulus and the cosine of the CP-violating phase of the higgsino mass
parameter , and , the ratio of the vacuum expectation
values of the two neutral Higgs doublet fields. [The remaining two-fold
ambiguity of the phase can be resolved by measuring the normal polarization of
the charginos.]Comment: 19 pages including 4 figure
Two-Photon Decay Widths of Higgs Particles
Two--photon decays of Higgs bosons are important channels for the search of
these particles in the intermediate mass range at the colliders LHC and
SSC. Dynamical aspects of the Higgs coupling to two photons can also be studied
by means of the fusion of Higgs particles at high--energy
ee linear colliders. Extending earlier analyses which had been
restricted to the Standard Model, we present in this note the QCD radiative
corrections to the decay widths of scalar and pseudoscalar
Higgs particles in multi--doublet extensions of the Higgs sector, as realized
for instance in supersymmetric theories.Comment: 8pages + 3figures (not included, a hard copy is available from A.D.
upon request), Prep. DESY 92-170 (to appear in Phys. Lett. B
Measuring the Spin of the Higgs Boson
By studying the threshold dependence of the excitation curve and the angular
distribution in Higgs-strahlung at e+e- colliders, e+e- -> HZ, the spin of the
Higgs boson in the Standard Model and related extensions can be determined
unambiguously in a model-independent way.Comment: 10 pages, 1 Postscript figure, sign typo correcte
SUSY Decays of Higgs Particles
Among the possible decay modes of Higgs particles into supersymmetric states,
neutralino and chargino decays play a prominent r\^ole. The experimental
opportunities of observing such decay modes at LEP2 and at future e+e- linear
colliders are analyzed within the frame of the Minimal Supersymmetric extension
of the Standard Model. For heavy Higgs particles, the chargino/neutralino decay
modes can be very important, while only a small window is open for the lightest
CP-even Higgs particle. If charginos/neutralinos are found at LEP2, such decay
modes can be searched for in a small area of the parameter space, and invisible
decays may reduce the exclusion limits of the lightest CP-even Higgs particle
slightly; if charginos/neutralinos are not found at LEP2 in direct searches,
the Higgs search will not be affected by the SUSY particle sector.Comment: 13 pages including 4 figures, uses latex and (e)psfig.st
Analysis of the neutralino system in supersymmetric theories
Charginos [(c)\tilde]± and neutralinos [(c)\tilde]0 in supersymmetric theories can be produced copiously at e+e- colliders and their properties can be measured with high accuracy. Consecutively to the chargino system, in which the SU(2) gaugino parameter M2, the higgsino mass parameter m and tanb can be determined, the remaining fundamental supersymmetry parameter in the gaugino/higgsino sector of the minimal supersymmetric extension of the Standard Model, the U(1) gaugino mass M1, can be analyzed in the neutralino system, including its modulus and its phase in CP-noninvariant theories. The CP properties of the neutralino system are characterized by unitarity quadrangles. Analytical solutions for the neutralino mass eigenvalues and the mixing matrix are presented for CP-noninvariant theories in general. They can be written in compact form for large supersymmetric mass parameters. The closure of the neutralino and chargino systems can be studied by exploiting sum rules for the pair-production processes in e+e- collisions. Thus the picture of the non-colored gaugino and higgsino complex in supersymmetric theories can comprehensively be reconstructed in these experiments
Production of Charginos/Neutralinos and Sleptons at Hadron Colliders
We analyse the production of charginos/neutralinos and sleptons at the hadron colliders Tevatron and LHC in the direct channels: p\bar{p}/pp \to \tilde{\chi}_i \tilde{\chi}_j + X\tilde{\ell} \bar{\tilde{\ell}'} +X$. The cross sections for these reactions are given in next-to-leading order SUSY QCD. By including the higher-order corrections, the predictions become theoretically stable, being nearly independent of the factorization and renormalization scales. Since the corrections increase the cross sections, the discovery range for these particles is extended in the refined analysis
Gluon Radiation Off Scalar Stop Particles
We present the distributions for gluon radiation off stop-antistop particles
produced in annihilation: . For
high energies the splitting functions of the fragmentation processes and are derived; they are
universal and apply also to high-energy stop particles produced at hadron
colliders.Comment: 9 pages, 2 figures as uuencoded ps files, Latex, uses epsfig,
complete postscript version at
ftp://x4u2.desy.de/pub/preprints/desy/1994/desy94-235.p
Deep Inelastic e-gamma Scattering at High Q2
The electromagnetic and weak structure functions of the photon can be studied
in the deep inelastic electron-photon processes e+gamma -> e+X and e+gamma ->
nu+X. While at low energies only virtual photon exchange is operative in the
neutral-current process, additional Z-exchange becomes relevant for high Q2 of
order MZ^2 at e+e- linear colliders. Likewise the charged-current process can
be observed at these high energy colliders. By measuring the electroweak
neutral- and charged-current structure functions, the up- and down-type quark
content of the photon can be determined separately.Comment: 8 pages, 5 eps-figures included. The complete paper is also available
via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp99/ttp99-35/ or
via www at http://www-ttp.physik.uni-karlsruhe.de/Preprints
Decays of W Bosons to Charginos and Neutralinos
The region of the supersymmetry parameter space, in which charginos decay
predominantly into sneutrinos and leptons: chi+ -> \tilde{\nu} + l+, is not
excluded experimentally for small mass differences between charginos and
sneutrinos. The decay sneutrinos are invisible in R-parity conserving theories
since they are either the lightest supersymmetric particles or they decay
primarily into the channel: neutrino + lightest neutralino. If the energy of
the decay leptons is so small that they escape detection, chargino events e+e-
-> chi+chi- in e+e- collisions remain invisible, eroding the excluded chargino
mass range at LEP. This region of the supersymmetry parameter space can partly
be covered by searching for single W events in e+e- -> W+W-$, with one W boson
decaying to leptons or quark jets, but the second W boson decaying to
(undetected) charginos and neutralinos.Comment: 11 pages, 3 figures, uses epsfig.st
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