T. N. Rengarajan

Study of hyperfragments

SummaryFrom a sample of 553 hyperfragments produced in 23 GeV/c proton interactions with emulsion nuclei, the hyperfragments of range ≥ 10 μm, have been studied. In order to understand the nature of these short-range hyperfragments, the emission of short tracks (R≤ 10 μm) and8Li fragments from interactions of 23 GeV/c protons and 3.5 GeV/c pions with emulsion nuclei have also been studied; for this 5968Li fragments have been used. From these studies it has been concluded that i) the effective Coulomb barrier for the emission of8Li fragments is smaller by a factor of ∼ 3 than the classical one; ii) a broad mass spectrum of nuclei is required to understand the range distribution of short tracks; this conclusion also follows from the Nh distribution of the parent stars; and iii) among the hyperfragments of range (0 ÷ 5) μm and (5÷10) μm, at least 34% and 74% respectively have mass numbers ≲ 50.RiassuntoIn un campione di 553 iperframmenti prodotti nelle interazioni di protoni di 23 GeV/o con nuclei delle emulsioni, si sono studiati gli iperframmenti con peroorso ≤ 10 μm. Per individuare la natura di questi iperframmenti di breve percorso, si è studiata anche l’emissione di oorte tracce (R≤ 10 μrn) e di frammenti8Li nelle interazioni di protoni di 23 GeV/c e di pioni di 3.5 GeV/c con i nuclei delle emulsioni; a questo scopo si sono utilizzati 596 frammenti8Li. Da questi studi si è concluso ehe i) la barriera di Coulomb effettiva per l’emissione di frammenti8Li è più piccola per un fattore di ∼ 3 di quella classica; ii) è necessario un largo spettro di massa dei nuclei per capire la distribuzione dei percorsi nelle tracoe corte; questa conclusione segue anche dalla distribuzione degliNhdelle stelle generatrici; e iii) degli iperframmenti di percorso (0/5) μm e (5/10) jim, almeno 34% e 74% rispettivamente hanno numero di massa ≲50.

Pulsars and the origin of cosmic rays

The capabilities and limitations of pulsars as sources of cosmic rays are reviewed in the light of experimental observations. Pulsars can supply the cosmic ray power if they have rotational velocities in excess of 700 rad s−1 at birth. Though this is theoretically possible, there is no experimental proof for the same. Pulsars can accelerate particles to the highest energies of 1020 eV, but in general, the spectra on simple considerations, turn out to be flatter than the observed cosmic ray spectrum. At the highest energies, absorption processes due to fragmentation and photodisintegration dominate for heavy nuclei. The existence of a steady flux of cosmic rays of energy greater than 1017 eV demands acceleration of particles to last over fifty years, the time interval between supernovae outbursts, whereas the expected period of activity is less than a few years. Finally, the problem of anisotropy with relevance to pulsars as sources and the possibility of observing pulsar accelerated particles from galactic clusters is considered.

A Pulsed magnetic study of the properties of surviving baryons in 25 GeV/c proton interactions

SummaryA study of particles emitted within a forward angle of 5° in collisions of 25 GeV/c protons with emulsion nuclei has been made with a stack exposed in a pulsed magnetic field of 200 kG-. The momenta and the sign of charge for the secondary particles have been determined by a measurement of magnetic curvature, after correcting for distortion. There is a large positive excess amongst the secondaries within this angular interval and it increases with increasing secondary energy. The elasticity distribution of the surviving protons has been obtained and it is found that = 0.41 ±0.05. The average transverse momentum of protons is found to be ∼ (400±50) MeV/c. By using the variation of grain density with momentum, it has been possible to identify the secondaries, and in this way the limit on the production of Σ- relative to all baryons is obtained as (2±1.5)%. The correlation between the multiplicityof an interaction and the energy given to the most energetic particle is also studied.RiassuntoSi è fatto uno studio delle particelle emesse entro un angolo in avanti di 5° nella collisione di protoni di 25 G-eV/c con i nuclei dell’emulsione, in una pila esposta in un campo magnetico pulsato di 200 kGr. Si sono determinati gli impulsi ed il segno della carica delle particelle secondarie, misurando la curvatura magnetica, dopo le correzioni per la distorsione. Entro questo intervallo angolare c’è un forte eccesso positivo fra i secondari che cresce al crescere dell’energia dei secondari. Si è ottenuta la distribuzione dell’elasticità dei protoni che sopravvivono e si è trovato che = 0.41 ±0.05. Si è trovato che l’impulso trasversale medio dei protoni è ∼ (400 ±50) MeV/c. Servendosi della varazione della densità dei grani coll’impulso, è stato possibile identificare i secondari e così si è ottenuto (2 ±1.5)%come limite per la produzione di Σ- relativamente a tutti i barioni. Si è anche studiata la correlazione fra la molteplicità di un’interazione e l’energia conferita alia più energetica particella.

Path length distribution of cosmic rays from pulsar nebula complexes

Particles accelerated in the vicinity of pulsars have to traverse the nebular matter surrounding pulsars. Using the variation of pulsar luminosity and nebular expansion, the path length distribution for the particle radiation is deduced and compared with that obtained from experimental observation. It is found that a significant amount of matter traversed by cosmic rays can be in the source itself; but it is not possible to simultaneously account for the production of secondary electrons and secondary nuclei with the same set of parameters.

Infra-red emission from galactic nuclei.

It has been suggested by several authors that the infra-red emission from galactic nuclei is due to synchrotron process from compact objects or due to thermal processes. We have examined here the coherent and incoherent synchrotron mechanisms from compact objects and find that these are unlikely to explain the observed emission.

The nature of radio emission from pulsars

It is shown that radio emission from pulsars is unlikely to be of coherent synchrotron origin if the surface magnetic field of the central neutron star is greater than 108 G.

TRANSIENT GAMMA-RAY SOURCES.

Gamma-ray production by particles escaping from a pulsar into the surrounding nebula is considered. The gamma-ray emission decreases with time and such pulsar-nebula complexes will be observed as transient sources.