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Frank Cuypers

Publications and source records attributed to Frank Cuypers.

32 records · Page 2Linked to original sources
arXiv1995

Physics with Like-Sign Muon Beams

We point out that both the specific lepton number content and the high energies potentially attainable with muon-muon colliders make it advisable to consider the technical feasibility of including an option of like-sign incoming beams in the studies towards a proposal to build a muon-muon collider with center-of-mass energies in the TeV region. This capability will add some unique physics capabilities to the project. Special attention will have to be paid to polarization retention for the muons.

hep-ph↗
arXiv1994

Production of Heavy Selectrons in Electron-Photon Collisions

We study the production and decay of heavy selectrons in the electron-photon mode of a linear collider of the next generation. The standard model backgrounds can be substantially reduced by appropriate kinematical cuts. As a consequence, selectrons far heavier than the kinematical threshold for pair production are shown to be easily discoverable for large portions of the supersymmetry parameter space. We also describe a model-independent kinematical measurement of the mass of the lightest neutralino.

hep-ph↗
arXiv1994

Top Quarks and $CP$ Violation in Polarized $e^+e^-$ Collisions

Electroweak dipole moments of the top quark are conjectured and their effect in polarized $e^+e^-$ collisions is examined for the expectation values of two different $CP$-odd observables. One of these observables probes the real part of the dipole moments whereas the other probes their imaginary part. It turns out that varying the polarization of the electron beam substantially enhances the resolving power of the experiment. PostScript version: preprints/mpi9454.ps from gluon.hep.physik.uni-muenchen.de

hep-ph↗
arXiv1994

Standard Model Predictions for Weak Boson Pair Production in E-E- Scattering

We study polarized $e^-e^-$ scattering into $\WW$, $\WZ$ and $\ZZ$ final states within the framework of the standard model of electroweak interactions. These mechanisms for producing pairs of weak gauge bosons are potential backgrounds to new reactions beyond the realm of the standard model. At a centre-of-mass energy of 500 GeV the total cross sections are calculated to be 2.5, 9.4 and 1.0 fb, respectively, for unpolarized beams. The energy behaviour of the cross sections as well as particularly interesting differential distributions are presented and the topology of the final states is discussed.

hep-ph↗
arXiv1994

Electron-Electron Scattering as a Probe of Anomalous Gauge Couplings

The effect of anomalous gauge couplings on polarized $e^- e^-$ scattering cross sections is examined. It turns out that different combinations of beam polarizations provide constraints that are complementary to each other and to those obtained from other experiments, such as $e^+ e^-$, $e^- γ$ and $γγ$ collisions.

hep-ph↗
arXiv1993

Testing Anomalous $W$ Couplings in $e^- e^-$ Collisions

We analyze the influence of anomalous gauge couplings in the reaction $e^- \: e^- \longrightarrow e^- \: W^- \: ν_e$ at a 500 GeV linear collider. The limits imposed by this process on deviations from the standard model of electro-weak interaction, are competitive with those inferred from other high energy experiments. Furthermore, the allowed domain in the parameter space is quite different, and hence such an experiment would more than complement the other direct searches.

hep-ph↗
arXiv1993

Light Gluinos at LEP

We study the production and decay of \lgl s in \ep\ collisions. We suggest a signature which suffers little from backgrounds and argue that the \lgl\ window can already be closed with the existing LEP data, provided the gluino lifetime is such that it decays within the detectors.

hep-ph↗
arXiv1993

Discovering Supersymmetry with Electron and Photon Beams

Linear collider designs are optimized for \ep\ collisions. However, from the physics point of view, \lc s may also be advantageously operated in an \ee, \eg\ or \pp\ mode. These options, which have not been available up to now, will provide unique tests of the \sm\ and of physics beyond it. As an example, we review the prospects for discovering and studying \susy\ at linear colliders in \ee, \eg\ and \pp\ collisions. In particular, we argue that \ee\ scattering is much better suited than \ep\ annihilation for discovering \sel s or \co s.

hep-ph↗
arXiv1993

Hadron Multiplicities in the Presence of Light Gluinos

We consider the effect of a massless gluino on the evolution of a parton shower. The hadron multiplicity distribution is predicted to evolve as a function of the collider energy in the same way as in the absence of gluinos, except for a slower running of $α_s$. A comparison of the predicted average hadron multiplicity with experimental data is presented as a fit constraining the values of the strong coupling constant at the $Z^0$ peak $α_s(m_Z)$ and the scale of the onset of hadronization $m_0$. It appears that \lgl s are unlikely to be detected this way with less than 500 GeV of \cm\ energy.

hep-ph↗
arXiv1993

Supersymmetric Signals in $e^-e^-$ Collisions

We consider the production and decay of selectrons and charginos in $e^-e^-$ collisions. The advantage over usual $e^+e^-$ collisions is the very low level of standard model backgrounds which should make the discovery of selectrons or charginos relatively straightforward. The use of polarized beams provides an additional powerful tool to determine the supersymmetry parameters.

hep-ph↗
arXiv1993

$\order(Γ)$ Corrections to $W$ pair production in $e^+e^-$ and $γγ$ collisions

Several schemes to introduce finite width effects to reactions involving unstable elementary particles are given and the differences between them are investigated. The effects of the different schemes is investigated numerically for $W$ pair production. In $e^+e^-\to W^+W^-$ we find that the effect of the non-resonant graphs cannot be neglected for $\sqrt{s}\geq400\GeV$. There is no difference between the various schemes to add these to the resonant graphs away from threshold, although some violate gauge invariance. On the other hand, in the reaction $γγ\to W^+W^-$ the effect of the non-resonant graphs is large everywhere, due to the $t$-channel pole. However, even requiring that the outgoing lepton is observable ($p_\perp > .02\sqrt{s}$) reduces the contribution to about 1\%. Again, the scheme dependence is negligible here.

hep-ph↗
arXiv1993

Supersymmetric Signals in $γγ$ Collisions

We study the occurrence of final states with only an electron-positron pair and missing transverse momentum as a signal of \susy\ in photon-photon collisions. Suitable high energy photon beams may be provided at linear colliders by back-scattering laser beams on electron beams. The final states considered represent a typical signature for the production and decay of selctron and chargino pairs within the \mssm. We show that, away from the kinematical threshold, selctrons produce this signal far more abundantly than charginos. The standard model background is dominated by W-pair production. We propose a series of kinematical cuts which reduce this background to an acceptable level. With a 1 TeV collider operated in the $γγ$-mode, we find that interesting and complementary tests of \susic\ models can be performed for selctron masses up to 350 GeV.

hep-ph↗
arXiv1992

Supersymmetric Signals in Electron-Photon Collision

Associated selectron-neutralino production in the process $e^-γ\to\tilde e^-\tildeχ^0$ provides a striking supersymmetric signal: events with a single high $p_\perp$ electron and otherwise only invisible particles. For $e^-γ$ collisions obtained at high energy linear colliders through back-scattering of a laser beam, this reaction is shown to be complementary to selectron pair production in the processes $e^+e^-\to\tilde e^+\tilde e^-$ and $e^-e^-\to\tilde e^-\tilde e^-$, and to be a probe of heavy selectrons beyond the kinematical limit of pair production. The standard model background from $e^-γ\to e^-Z^0$ and $W^-ν$ is studied and substantially reduced by rapidity and transverse momentum cuts. The minimum required integrated luminosities for observing this \susic\ signal are given as functions of several model parameters and collider energies.

hep-ph↗