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 e+e−e^+e^- Colliders with Polarized Beams

The chargino $\tilde{\chi}^\pm_{1,2}$ system can be reconstructed completely in $e^+e^-$ collisions. By measuring the total cross sections and the asymmetries with polarized beams in $e^+e^-\to\tilde{\chi}_i^+ \tilde{\chi}_j^- [i,j=1,2]$, the chargino masses and the gaugino-higgsino mixing angles of these states can be determined very accurately. If only the lightest charginos $\tilde{\chi}_1^\pm$ 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 $M_2$, the modulus and the cosine of the CP-violating phase of the higgsino mass parameter $\mu$, and $\tan\beta = v_2/v_1$, 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 $pp$ colliders LHC and SSC. Dynamical aspects of the Higgs coupling to two photons can also be studied by means of the $\gamma \gamma$ fusion of Higgs particles at high--energy e$^+$e$^-$ linear colliders. Extending earlier analyses which had been restricted to the Standard Model, we present in this note the QCD radiative corrections to the $\gamma \gamma$ 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: $p\bar{p}/pp \to The cross sections for these reactions are given in next-to-leading order SUSY QCD. By including the higher-order corrections, the predictions become theoretically stable, being nearly independent of the factorization and renormalization scales. Since the corrections increase the cross sections, the discovery range for these particles is extended in the refined analysis.We analyse the production of charginos/neutralinos and sleptons at the hadron colliders Tevatron and LHC in the direct channels:$p\bar{p}/pp \to \tilde{\chi}_i \tilde{\chi}_j + X$and$\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 $e^+e^-$ annihilation: $e^+e^- \to \tilde t \bar{\tilde t} g$. For high energies the splitting functions of the fragmentation processes $\tilde t \to \tilde t g$ and $g \to \tilde t \bar{\tilde t}$ 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