Radiative signal for supersymmetric particle production in photon-electron collisions

We discuss the production of gauginos and selectrons accompanied by photon emission in high energy scattering of real photons off electrons.     

Search for supersymmetric particles in light gravitino scenarios and sleptons NLSP

A search for sleptons, neutralinos, charginos, sgoldstinos and heavy stable charged sleptons in the context of scenarios where the lightest supersymmetric particle is the gravitino, is presented. Data collected during 2000 with the DELPHI detector at centre-of-mass energies from 204 to 208 GeV were analysed and combined with all the data collected from 1995 to 1999 at lower energies. No evidence for the production of sleptons, neutralinos and charginos has been found, therefore new limits on the mass of these supersymmetric particles and on the model parameter space are set. The search for heavy stable charged sleptons also updates the stable sleptons mass limit. The absence of evidence for sgoldstino production allows limits to be set on its mass and on the scale of supersymmetry breaking. Received: 6 November 2002 / Published online: 14 February 2003     

The reconstruction of supersymmetric theories at high energy scales

The reconstruction of fundamental parameters in supersymmetric theories requires the evolution to high scales, where the characteristic regularities in mechanisms of supersymmetry breaking become manifest. We have studied a set of representative examples in this context: minimal supergravity and a left-right symmetric extension; gauge mediated supersymmetry breaking; and superstring effective field theories. Through the evolution of the parameters from the electroweak scale the regularities in different scenarios at the high scales can be unravelled if precision analyses of the supersymmetric particle sector at e ⁺ e ^- linear colliders are combined with analyses at the LHC. Received: 25 November 2002 / Published online: 31 January 2003     

Energy spectrum of electron pairs in a high energy photon-electron cascade

The energy spectrum of electron pairs generated in a high energy photon-electron cascade up to a depth of 1·5 c. u. was measured and the possible influence of the medium on the shape of the spectrum according to Landau-Pomeranuk-Ter Mikaelyan and Migdal was investigated. Two procedures were used for the analysis; no significant deviation from the Bethe-Heitler spectrum could be observed. Different ways of estimating the primary energy were applied; the resulting value, 2×10¹²eV, was accepted as the primary energy.

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The authors wish to thank Dr. Lanius for kindly lending them the necessary plate from the Berlin part of the I-stack.     

Search for magnetic monopoles in proton-antiproton interactions at 540 GeV cm energy

A search for magnetic monopoles hass beenpursued at the proton-antiproton collider at CERN, with plastic detectors. No candidates were found. Limits for the production cross section of such objects are given.     

Search for supersymmetric particles in scenarios with a gravitino LSP and stau NLSP

Sleptons, neutralinos and charginos were searched for in the context of scenarios where the lightest supersymmetric particle is the gravitino. It was assumed that the stau is the next-to-lightest supersymmetric particle. Data collected with the DELPHI detector at a centre-of-mass energy near 189 GeV were analysed combining the methods developed in previous searches at lower energies. No evidence for the production of these supersymmetric particles was found. Hence, limits were derived at 95% confidence level. Received: 3 February 2000 / Revised version: 3 March 2000 / Published online: 8 May 2000     

Clan structure and intermittency in proton-nucleus interactions at high energy

In this paper we examine the similarity between clan structure and self-similar cascading in high energy proton-nucleus interactions at 70 GeV/c in emulsion. The investigation shows that the negative bionomial fitting parameterk can be used for the evaluation of factorial moments in intermittency studies and that these exhibit similar behaviour with those derived from nonstatistical procedure. The results of our study signify compatibility between clan cascading and self-similar cascading in soft hadroization processes.     

Search for correlated neutral strange particles and muon production in π−p interactions at 225 GeV

A measurement is made of the production correlation between neutral strange particles V and muons. The interactions originated in a streamer chamber containing a Lucite target bombarded by 225 GeV π^? mesons. The experiment has a sensitivity of 10 events per nanobarn and yields no evidence for new particles.     

Experimental study of proton-emulsion nuclei interactions at high energy

Proton-emulsion nuclei interactions at 200 and 400 GeV have been studied. The results on the energy dependence of <n _s(n _s-1)> and <n _s>/D, multiplicity scaling, multiplicity density scaling in the central region, integral angular distribution, rapidity dispersion and maximum rapidity gap are presented and compared with those of proton-nucleon interactions at the corresponding energies.     

Cascade particles,nuclear evaporation,and residual nuclei in high energy hadron-nucleus interactions

Based on a Monte Carlo realization of the Dual Parton Model we study the production of target associated particles and of nuclear fragments in high energy hadronnucleus interactions. A formation zone intranuclear cascade of low energy secondaries inside the target nucleus is discussed. We calculate excitation energies of residual nuclei left after the intranuclear cascade process and treat their fürther disintegration by introducing models for the evaporation of protons, neutrons, and light fragments, high energy fission, and by applying a Fermi Break-up model to light nuclear fragments. The results are compared to data on target associated particle production. We fürthermore calculate cross sections for the production of nuclear fragments.     

Signals for intrinsic charm in high energy interactions

The prospects to test the hypothesis of intrinsic charm quarks in the proton are investigated. We consider how this component can be directly or indirectly probed in deep inelastic scattering at HERA and in fixed target experiments and find that an overlooked signal might be present in existing NMC data. Applying the intrinsic charm model to hadron collisions we compare the resulting charm production cross-sections with those based on standard perturbative QCD and available data. Extrapolating to higher energies we obtain predictions for charm production at the Tevatron and LHC.     

Hadron weak interactions at high energy and the parton model

It is shown that, within the parton picture, weak (P-odd) effects increase with energy and momentum transfer. The presence of an effctive current with ΔS = 0 and 1 due to constituent interchange or annihilation is expected in the parton picture of hadron-hadron weak interactions. A typical value of P-odd effects, nucleon or hyperon polarization or asymmetry in quasi two-body reactions is about 10^?4 at E_lab ～ 10³ GeV and 10^?3 in large angle (t ～ s) scattering in the conventional current × current scheme of weak interactions. A principal possibility to clear up quark statistics is pointed out.     

The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

Mass gain and loss of non-relativistic electrons in photon-electron interactions

It is shown that the electrons gain mass as their non-relativistic velocities increase. This process is realized by the absorption of photons in the colliding process. In an inverse manner, they loss their mass when they radiate photons. The related equations are derived by using the relativistic mass equation and independently by considering the non-relativistic energy relation. The Compton scattering and photon emission phenomena are revisited with the new theory.     

Strangeness exchange in high energy interactions

The average strangeness transfer computed for the K^±p interactions on the basis of the existing experimental data does not change appreciably in the 4 to 16 GeV/c beam momentum range, being negative for K⁺p and positive for K^?p interactions. Comparison with the electric charge transfer is made.