Two-photon production of squarks and sleptons

High energy γγ-type reactions are investigated as a means for producing pairs of scalar superpartners of leptons and quarks. We report on the calculation of the cross sections and discuss on the competing background processes.     

The gaugino-higgsino mixing matrix and the ep production of squarks and sleptons

The cross section for ep production of squarks and sleptons is recalculated taking account of the mixing between gauginos and higgsinos. The previous calculations, which neglected this mixing, are found to represent the most optimistic production rates for a given set of particle masses. The possibility of extracting information about the gaugino-higgsino mixing matrix from a measurement of these cross sections is discussed.     

Pair production and optical lasers

Electron-positron pair creation in a standing wave is explored using a parameter-free quantum kinetic equation. Field strengths and frequencies corresponding to modern optical lasers induce a material polarization of the QED vacuum, which may be characterized as a plasma of e+e- quasiparticle pairs with a density of approximately 10(20) cm-3. The plasma vanishes almost completely when the laser field is zero, leaving a very small residual pair density n(r) which is the true manifestation of vacuum decay. The average pair density per period is proportional to the laser intensity but independent of the frequency nu. The density of residual pairs also grows with laser intensity but n(r) proportional to nu(2). With optical lasers at the forefront of the current generation, these dynamical QED vacuum effects can plausibly generate 5-10 observable two-photon annihilation events per laser pulse.     

Pair production and heavy electron

Production of electron positron pairs is analysed with the hypothesis of the heavy electrone ^*. A rough agreement between theory and experiment is found if the coupling constant is suitably chosen as a function of the massm ^* of thee ^*. Comparison with upper limits for this coupling constant taken from inelastic electron proton scattering indicates that a heavy electron withm ^* between 120 MeV and 1 GeV cannot explain observed deviations from pure quantum electrodynamics.     

Pair production of doubly heavy diquarks

The differential and total cross sections for the pair production of doubly heavy diquarks are calculated analytically within the diquark model. The cases of electron-positron and quark-antiquark annihilation are considered. The ratios of the total cross sections to the corresponding cross sections for annihilation into two heavy quarks are estimated numerically.     

Tachyonic squarks in split supersymmetry

The decoupling of scalar particles in split supersymmetry makes the spectrum of squarks irrelevant for low energy processes. Nevertheless, the structure of the vacuum is sensitive to the spectrum of squarks, even when the supersymmetry breaking scale is large. In this Letter, we show that in certain regions of the parameter space, squarks could develop radiatively tachyonic masses, thus breaking electric charge and color. We discuss the constraints that follow from the requirement of charge and color conservation, and we comment on the implications for model building.     

Pair production in time-dependent electric fields

The particle production problem in a general time-dependent electric field is formulated by path integrals. The creation of charged scalar particles and electron-positron pairs is studied in detail for an exponentially decaying electric field. Some other exactly solvable cases are also considered.     

Heavy quarks and squarks fromW-gluon fusion

We discussWg-fusion as a source heavy quark and squark pairs at very high energy hadron colliders. EffectiveW approximation is used to calculate the cross-sections analytically in the forward scattering configuration; good agreement is obtained with exact numerical calculations.W-gluon fusion is found to be not nearly as important a production mechanism of heavy squarks as it is of heavy quarks. This is especially true when the mass-splitting within theSU(2) _L doublet is small.     

Next-to-leading order QCD predictions for associated production of top squarks and charginos at the CERN LHC

We present the calculations of the complete next-to-leading order (NLO) inclusive total cross sections for the associated production processes in the minimal supersymmetric standard model at the CERN Large Hadron Collider. Our calculations show that the total cross sections for the production for the lighter top squark masses in the region 100 GeV 160 GeV can reach 1 pb in the favorable parameter space allowed by the current precise experiments, and in other cases the total cross sections generally vary from 10 fb to several hundred fb except for both 500 GeV and the production channel. Moreover, we find that the NLO QCD corrections in general enhance the leading order total cross sections significantly, and vastly reduce the dependence of the total cross sections on the renormalization/factorization scale, which leads to increased confidence in predictions based on these results.Received: 2 March 2003, Revised: 28 May 2003, Published online: 11 July 2003     

Signatures of gluinos and squarks at proton-proton colliders

We present a detailed study of gluino and squark decays for masses up to 1 TeV. We explore the whole supersymmetry parameter range relevant for LHC and SSC. We calculate the rates for interesting signatures such as the direct transition into the lightest supersymmetric particle, the production of two Z⁰s, and multimuons in the final state.     

A search for leptoquarks and squarks at HERA

A search in the H1 experiment at HERA for scalar and vector leptoquarks, leptogluons and squarks coupling to first generation fermions is presented in a data sample corresponding to an integrated luminosity of 425 nb^–1. For masses ranging up to 275 GeV, no significant evidence for the direct production of such particles is found in various possible decay channels. At high masses and beyond the centre of mass energy of 296 GeV a contact interaction analysis is used to further constrain the couplings and masses of new vector leptoquarks and to set lower limits on compositeness scales.Supported by the Bundesministerium für Forschung und Technologie, FRG under contract numbers 6AC17P, 6AC47P, 6DO571, 6HH17P, 6HH271, 6HD171, 6HD271, 6KH7P, 6MP171, and 6WT87P     

Three-loop anomalous dimensions for squarks in supersymmetric QCD

In this Letter we evaluate the renormalization constants and anomalous dimensions for the squark wave function and mass within supersymmetric QCD. These results complement the ones obtained in Harlander et al. (2009) [1] and thus provide further confirmation on the applicability of dimensional reduction to supersymmetric QCD at three-loop order. The three-loop anomalous dimension constitute important input to precision predictions of the supersymmetric mass spectrum as obtained from the evolution from the GUT to the TeV energy scale.     

Pair production in inhomogeneous electric fields with phase modulation

Electron-positron pair production in spatial inhomogeneous electric fields with sinusoidal phase modulation is studied within the Dirac-Heisenberg-Wigner formalism. The focus is on discussing the effects of the modulation parameters on the momentum spectrum and the reduced particle number at various spatial scales. For the momentum spectrum, the interference effect becomes more and more remarkable with the increase of modulated amplitude or frequency,while the symmetry is severely destroyed with...