Low-energy supersymmetry

We discuss the problem of constructing a model in which supersymmetry is unbroken down to low energies. It is suggested that the scalar partners of quarks and leptons may get their masses through radiative corrections and that the breaking of the weak interactions also occurs through radiative corrections. A toy model is constructed which illustrates these ideas.     

Low-energy baryosynthesis

We consider general constraints on baryosynthesis in low-energy SU(3) × SU(2) × U(1) theories. We find in general that phenomenologically acceptable models exist, which are unifiable at higher energies-but which all require exotic fermion content.     

Low-energy pion-nucleon scattering

Several topics in pion-nucleon scattering at low energies are addressed. First, we review the predictions of chiral symmetry for the near-threshold region. The pion-nucleon scattering lengths and the Cheng-Dashen theorem with the related issue of the strangeness content of the nucleon are discussed in some detail. Finally, the status of the scalar mesons and the relevance of the pomeron and the concept of duality for pion-nucleon dynamics is pointed out.Lecture given at the 8th Summer School on Intermediate Energy Physics: Hadron Dynamics at Low and Intermediate Energies, Prague, July 10–14, 1995.I would like to thank the organizers of the Praha Indian-summer school for inviting me to this beautiful city. I am indebted to Th. Rijken and J. J. de Swart for discussions about the pomeron, the scalar mesons, and partial-wave analysis, and to U. van Kolck and J. Friar for discussions about chiral symmetry. This work was included in the research program of the Stichting voor Fundamenteel Onderzoek der Materie (FOM) with financial support from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO).     

Low-energy neutrino measurements

Low-energy solar neutrino detection plays a fundamental role in understanding both solar astrophysics and particle physics. After introducing the open questions on both fields, we review here the major results of the last two years and expectations for the near future from Borexino, Super-Kamiokande, SNO and KamLAND experiments as well as from upcoming (SNO+) and planned (LENA) experiments. Scintillator neutrino detectors are also powerful antineutrino detectors which can detect neutrinos emitted by the Earth crust and mantle. First measurements of geoneutrinos have occurred which can bring fundamental contribution in understanding the geophysics of the planet.     

Low-energy proton-proton scattering

The discrepancies which have been reported in experimental data for low-energy proton-proton scattering can be partly explained by various relativistic, radiative and finite proton size effects.     

Low-energy weak-interaction studies

An overview is given of the present status of low-energy tests of the Standard Model in nuclear beta-decay and neutron decay, covering the unitarity problem, searches for right-handed currents, scalar- and tensor-type currents, tests of time-reversal violation, as well as experiments to set the neutrino mass scale. In view of the large amount of ongoing and planned experiments in this sector, many new results can be expected in the coming decade. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: nathal.severijns@fys.kuleuven.ac.be     

Low-energy antiproton-neon interaction

By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and K_s⁰ in the p̄-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic p̄-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the p̄-n and the p̄-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei.     

Low-energy resonances in C

Simple shell-model calculations and single-particle widths suggest that the apparent width for the lowest-energy resonance in ¹⁷C, observed in ¹⁷C(p,p^′) and ¹⁴C(¹²C, ⁹C), must be the result of two or three unresolved narrow states, and not the natural width of either. I offer suggestions for Jπ and give limits on expected widths.     

Low-energy pion-nucleus optical potentials

We discuss the local and non-local pion-nucleus optical potentials. We find that the local potential becomes non-local when two-nucleon correlations are included. The two potentials (including correlations) can be made local through a transformation on the wave function. The new local potentials agree up to quadratic terms when expanded in powers of the density. The influence of finite-range correlations and off-shell pion-nucleon form factors is also investigated.     

Low-energy electron beam source

Experimental results of research into a ferroelectric-plasma-source-assisted hollow anode (HA) discharge as a source of low-energy electron beams are presented. To generate electron beams, the HA auto-bias negative voltage was achieved by the discharge current flowing through the resistor connecting the HA and the grounded electrode. It is shown that this method allows reliable and reproducible generation of low-energy electron beams with electron energy of several hundreds of eV, electron current density up to several A/cm² and pulse duration of several tens of microseconds.     

反传感器低能激光武器

随着光电技术的迅速发展，形形色色的电光传感器在现代军事装置和现代化战争中发挥越来越重要的作用，因而也就成为低能激光武器的重要攻击目标。本文首先描述战场上激光武器攻击传感器的几种主要方式；然后着重讨论了激光能密度在传感器中的增益；从而阐明传感器易受激光武器攻击的机制；最后简单介绍用于攻击不同传感器的激光类型。     

Low-energy antimony implantation in silicon

Abstract

Antimony is known to be a donor in silicon, Low-energy implantations of Sb in Si produce very shallow profiles which have many device applications. Gibbons et al. ¹ calulated the projected ranges of Sb ion-implanted in Si, using the LSS (Lindhard, Scharff, and Schiott) method. Oetzmann et al. ² measured projected ranges and range straggling for several heavy ions in Si, Al, and Ge, using high-resolution backscattering; in the energy region of interest to us, e = 10^?2 to 10^?1, their results were about 30% higher than those reported by Gibbons et al. In the study reported here, we implanted 5 × 10¹⁴ Sb/cm² in Si at 5–60 keV, measured the resulting depth distribution by secondary ion mass spectrometry, and checked the measurements by backscattering. Our results showed the experimental projected ranges to be about halfway between those reported in the earlier studies. The discrepancies between theoretical calculations and experimental results are due not to the electronic stopping cross section, which is negligible in the range of interest here, but to the nuclear stopping power. Using a modified nuclear scattering potential given by Wilson et al.,³ we calculated the projected range distribution according to the method described by Winterbon.⁴ Our results are in very good agreement with the experimental measurements.     

Low-energy theory of disordered graphene

At low values of external doping, graphene displays a wealth of unconventional transport properties. Perhaps most strikingly, it supports a robust "metallic" regime, with universal conductance of the order of the conductance quantum. We here apply a combination of mean-field and bosonization methods to explore the large scale transport properties of the system. We find that, irrespective of the doping level, disordered graphene is subject to the common mechanisms of Anderson localization. However, at low doping a number of renormalization mechanisms conspire to protect the conductivity of the system, to an extend that strong localization may not be seen even at temperatures much smaller than those underlying present experimental work.     

Low-energy photoproduction of \omega-mesons

The photoproduction of the vector meson has been studied between threshold and W = 2.4 GeV with the SAPHIR detector at the Bonn electron stretcher ring ELSA. Besides, the total cross-sections angular distributions in the CMS and decay angular distributions in the helicity and Gottfried-Jackson systems have been measured.Received: 26 February 2003, Revised: 20 May 2003, Published online: 9 October 2003PACS: 14.40.Cs Properties of specific particles: Other mesons with S = C = 0, mass < 2.5 GeVJ. Barth: Part of doctoral thesis [1].W. Braun: No longer working at this experiment.     

Low-energy scattering of composite neutrinos

In composite models neutrinos have electromagnetic form factors if their constituents carry electric charge. It is pointed out that in this case low-energy elastic-electron neutrino-electron scattering experiments which may be carried out within the next few years will be as sensitive to the substructure of the electron neutrino as present (g − 2)_e experiments are to the substructure of the electron.     

Low-energy models with two supersymmetries

Realistic models of low-energy physics with two supersymmetries are constructed. Several mechanisms for providing large mirror fermion masses are given in models with gauge groups SU(3) × SU(2) × U(1) and SU(3) × SU(4) × U(1). It is found that the supersymmetry breaking scale must be significantly larger than the W-boson mass. Although none of the models is fully natural, each predicts that mirror fermions should soon be discovered. While the ordinary and mirror squarks and sleptons tend to be very heavy, some gauginos or mirror gauginos are probably light. The models offer prospects for eventual unification into finite grand unified theories.