H. B. van der Raay

Global Oscillations at Low Frequency from the SOHO mission (GOLF)

The GOLF experiment on the SOHO mission aims to study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10−7 to 10−2 Hz. Bothp andg mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument employs an extension to space of the proven ground-based technique for measuring the mean line-of-sight velocity of the viewed solar surface. By avoiding the atmospheric disturbances experienced from the ground, and choosing a non-eclipsing orbit, GOLF aims to improve the instrumental sensitivity limit by an order of magnitude to 1 mm s−1 over 20 days for frequencies higher than 2.10−4 Hz. A sodium vapour resonance cell is used in a longitudinal magnetic field to sample the two wings of the solar absorption line. The addition of a small modulating field component enables the slope of the wings to be measured. This provides not only an internal calibration of the instrument sensitivity, but also offers a further possibility to recognise, and correct for, the solar background signal produced by the effects of solar magnetically active regions. The use of an additional rotating polariser enables measurement of the mean solar line-of-sight magnetic field, as a secondary objective.

Elastic n-p charge-exchange scattering at 8 GeV/c

SummaryThe differential cross-section for elastic charge-exchange scattering of neutrons on protons has been measured at 8 GeV/c over forward laboratory scattering angles (0÷90) mrad (square of four-momentum transfer 0<−t<0.5 (GeV/c)2). The method utilized acoustic spark chambers and about 1900 elastic-scattering events were analysed. A value of (dσ/dΩ)lab=(20±6) mb/sr (dσ/dt=(0.93±0.28) mb/(GeV/c)2) was obtained for the forward differential cross-section and an estimated (0.06±0.03) mb for the elastic charge exchange cross-section. Both cross-sections show the decreased values expected from Pomeranchuk’s second theorem (1) when compared with results at lower energies (2). Further comparison shows that the narrow forward peak in the distribution of dσ/dt previously observed for −t<0.05, is still present at 8 GeV/c, varying in shape only slowly, if at all, with energy. For −t>0.1 however, energy dependence is apparent. The results also suggest that the interaction is spin-dependent and/or that the real parts of the scattering amplitudes in the isospin states 0 and 1 are different. Comparisons with the theoretical predictions show good agreement with the value of forward cross-section given by the Regge pole approach ofAhmadzadeh (3). The model ofRingland andPhillips (4) for single-pion exchange with absorption agrees with our results for −t<0.01 but a predicted secondary peak at −t∼0.08 is not observed.RiassuntoSi è misurata la sezione d’urto differenziale per lo scattering di scambio di carica elastico di neutroni su protoni ad 8 GeV/c per angoli di scattering in avanti nel sistema del laboratorio di (0÷90) mrad (quadrato del quadrimomento trasferito 0<−t<0.5 (GeV/c)2). Il metodo faceva uso di camere a scintilla acustiche e si sono analizzati circa 1900 eventi di scattering elastico. Si è ottenuto un valore di (dσ/dΩ)lab=(20±6) mb/sr (dσ/dt=(0.93±0.28) mb/(GeV/c)2) per la sezione d’urto differenziale in avanti e un valore stimato di (0.06±0.03) mb per la sezione d’urto di scambio elastico di carica. Entrambe le sezioni d’urto presentano i valori diminuiti previsti dal secondo teorema diPomeranchuk (1) in confronto con i risultati ad energie minori (2). Un ulteriore confronto mostra che lo stretto picco in avanti nella distribuzione di dσ/dt osservato precedentemente per −t<0.05, è ancora presente a 8 GeV/c, variando di forma con l’energia, se pure solo lentamente. Per −t>0.1 però, la dipendenza dall’energia è solo apparente. I risultati suggeriscono anche che l’interazione dipende dallo spin e/o che le parti reali delle ampiezze di scattering negli stati di isospin 0 ed I sono diverse. Il confronto con le predizioni teoriche mostra il buon accordo col valore della sezione d’urto in avanti dato dal metodo del polo di Regge diAhmadzadeh (3). Il modello diRingland ePhillips (4) per lo scambio di un solo pione con assorbimento concorda con i nostri risultati per −t<0.01 ma non si osserva il secondario previsto a −t∼0.08.

The real part of the spin-independent forward scattering amplitude in elastic nucleon-nucleon collisions

Abstract Elastic pp and pd scattering in the Coulomb interference region have been studied using a sonic spark chamber technique. Analyses of these data yield α p = 0.10 ± 0.16 and n = −0.50 ± 0.15 at 1.69 GeV/ c in good agreement with dispersion relation calculations, the value of α p = −0.30 ± 0.09 obtained at 1.54 GeV/ c is however not consistent with these calculations.

K+p elastic scattering between 432 and 939 MeV/c and phase shift analysis

Abstract Measurements of K + p elastic scattering have been carried out at 13 momenta between 432 MeV/ c and 939 MeV/ c using spark chambers. The data establish unambiguously the constructive interference of the Coulomb and nuclear amplitudes at 432 MeV/ c . The elastic cross section is found to be independent of momentum through the range covered. The phase shifts for S, P, D and F waves are obtained in an energy dependent analysis in which higher waves are held at theoretical values. The initial behaviour ofthe P, D and F amplitudes is quite close to that predicted by the calculation of the peripheral partial waves. Only the P3 and D5 amplitudes become strikingly different with increasing momentum.

The production of He3 from deuteron interactions at 650 MeV

Abstract The angular distributions of He3 particles produced in association with one pion in the interaction of 650 MeV deuterons (a) with protons and (b) with individual nucleons from deuterium target nuclei have been measured in the forward direction. The differential cross-sections at 0° in the c.m. system were found to be 11.6±0.5 μb·sr−1 and 18.7±1 μb·sr−1, respectively. The interaction of deuterons with deuterons producing He3 particles and neutrons has also been investigated and at 0° yields a cross-section of 78±5 μ b ∔ sr −1 in the c.m. system.

K+n elastic and charge-exchange scattering between 430 and 940 MeV/c

Abstract Elastic and charge-exchange K+n differential cross sections have been measured from K+d interactions from 430 to 940 MeV/c using spark chambers and scintillation counters. The data have been compared with existing results and in an accompanying paper have been included with other measurements in a phase-shift analysis.

The radial velocity of the sun as a star and the solar cycle

Abstract Radial velocity measurements of the sun as a star using a resonant scattering spectrometer have been obtained at Izana (Tenerife) during long observing seasons from 1976 to 1985. Its analysis shows that except for the global oscillations with periods shorter than one day there are stable signals with longer periods: at ∼13 days with mean amplitude of ∼ 3 m/s (it changes with the solar cycle) and another one of ∼ 15 m/s amplitude which shows a temporal variation of various years related to the solar cycle. The first signal has a partial explanation as an effect produced by the passage of active regions through the visible surface of the sun but it does not completely explain the observed signal. The second one, related to the limb shift, is probably due to changes in the convection zone in connection with the solar cycle.

Structure of the 5-minute solar oscillations 1976–1980

The discrete structure in the 5 min velocity oscillations of the solar surface has been confirmed by a re-analysis of data obtained between 1976 and 1979, and in addition a preliminary analysis of 1980 data show excellent consistency of the determined frequencies over the five year period. It is further shown that atmospheric transparency, as measured by the power in the solar intensity fluctuations, shows no correlation with the measured amplitude of the velocity fluctuations, over 2 orders of magnitude.

Measurement of K−p elastic differential cross sections between 610 and 943 MeV/c

Measurements of K−p elastic scattering have been carried out at 14 momenta between 610 MeV/c and 943 MeV/c over the angular range −0.9 < cos θ < 0.9. The results agree well with the best existing data and have significantly smaller errors.

SMALL ANGLE pp SCATTERING IN THE MOMENTUM RANGE 1.3 TO 1.5 GeV/c.

Abstract Elastic pp scattering in the Coulomb interference region has been studied using sonic spark chambers with a magnetic spectrometer. Measurements were made at 1.29, 1.39 and 1.54 GeV/ c and the data were analysed to determine the real part of the spin independent forward scattering amplitude. Disagreement with the predictions of dispersion relation calculations was found.