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In a stack of striped emulsions three cases of K-meson decays have been found. K2 and K3 have a mass of 915±130 m3e; the secondaries cannot be identified. The mass of K1-meson is 1020±270 me (scattering-range) and 1165±130 me (ionization-range); its secondary is a light meson withpβ= 104±24 MeV/c.

A considerable number of electromagnetic cascades have been analyzed to determine the increase of the multiplicity with the primary energy, the spectrum of the energies of the secondaries and the trident production. No appreciable discrepancy from the theory has been remarked.

529 tracks of heavy primaries in the cosmic radiation have been studied. Charge measurements have been carried out on all tracks with a photometric method, and independent checks with gap counting have been performed on Boron and Carbon tracks. All tracks have been followed through and a total of 331 nuclear collisions observed. From the analysis of these interactions, the interaction mean free paths and fragmentation probabilities in emulsion and in air have been determined. The results are in good agreement with those of other workers and have been used to extrapolate the charge distribution at the top of the atmosphere: the ratios of light nuclei and of heavy nuclei to medium nuclei, at the top of the atmosphere, are 0.30 ±0.09 and 0.51 ±0.11 respectively. Results of energy determination on 275 tracks give a value 1.541-0.130.16 for the exponent of the integral energy spectrum. Some difficulties in the application of Peters’ relation between the energy of primary and the angles of emission of the fragmentation products are discussed.

This work follows a previous study of the interactions of long lived neutral K-mesons, already published. The increased statistics allows us to check the results previously obtained and to determine the cross section for charge exchange of the θ20 particles in the eigenstate of strangeness-1.

From a star observed in a stack of stripped emulsions, a K-meson and a neutral particle decaying in flight are emitted. The V-event can be interpreted either as a Λ0 decay (Q=36−16+67 MeV) or as a θ0-decay (Q=216−55+150 MeV).

Results of our investigations into the cosmic-ray heavy primary charge and energy spectra at Neepawa, Canada (geomagnetic latitude 61° N), during a time of high solar activity (August 1958) are presented. The total heavy-primary differential energy spectrum is shown to have the same shape as the contemporaneous α-particle spectrum but theL/M ratio shows an increase from (0.28±0.05) at kinetic energies over 1.5 GeV/nucleon to (0.43 ± 0.07) at energies less than 1.0 GeV/nucleon.

Detailed experimental data on two events consisting of a narrow shower of pairs of charged particles are reported. An analysis of the common features of the events points out some difficulties in the explanation of the phenomenon as an ordinary cascade shower. Other possible interpretations are suggested.

The energy distribution of Λ0 coming from K capture stars has been obtained measuring Λ0 found by area scanning in two emulsion stacks. This distribution, compared to a theoretical one obtained with an optical model calculation, gives indication that the percentage of multi-nucleon captures in nuclear emulsions of the order of 30%. To the same conclusion we are led by the detailed study of 103 capture stars correlated to Λ0 decay. From the study of the missing energy in K- capture stars we deduce that the probability for a π0 of being absorbed in nuclear matter is very low. There is evidence that the probability for the emission of a Λ0 is not strongly dependent on the atomic weight of the nucleus in which the K- was absorbed. The upper limit for the cryptofragment formation is 15%. A search for the formation of Y1*- in the reaction\(K^ - + 2n \to Y_1^{ * - } + n\) at rest in the emulsion nuclei gives no conclusive result due to the low statistics.

We describe here the esperimental apparatus which has been used to study the angular distribution of γ-rays from positrons annihilation. The results of measurements carried out on various forms of silica and on aqueous solutions of several salts are discussed.

We determined thepβ of the secondaries of a high energy jet from scattering measurements. We calculated the angular and momentum distribution in the centre of mass system and we found a good agreement with Heisenberg’s and Wataghin’s theories. We give also the value of the percentage of K-mesons emitted in the nuclear interaction and an estimate of the mean free path for nuclear interactions of the charged π-mesons.

T h e m e a s u r e m e n t of c i rcu la r p o l a r i z a t i o n of ~,-rays is of i n t e r e s t in c o n n e c t i o n w i t h t h e new ideas on p a r i t y n o n c o n s e r v a t i o n in ~-decay (~,~). F o r t h i s p u r p o s e we h a v e b u i l t a ~-c i rcu la r p o l a r i m e t e r b a s e d on C o m p t o n b a c k s c a t t e r i n g f r o m i ron m a g n e t i z e d para l l e l a n d a n t i p a r a l l e l t o t h e i n c i d e n t r a d i a t i o n . Th i s des ign p r e s e n t s two a d v a n t a g e s ove r p o l a r i m e t e r s p r e v i o u s l y desc r ibed (3): i t m a k e s use of t h e m a x i m u m p e r c e n t a g e di f ference for t h e two d i r e c t i o n s of po la r i za t ion , a n d can be e m p l o y e d a t r e l a t i v e l y low energy . T h e C o m p t o n cross sec t ion , as a f u n c t i o n of t h e m o m e n t a k o a n d ]~ of t h e i n c i d e n t a n d s c a t t e r e d ~/-ray, is g i v e n b y (4)

The non-conservation of parity is shown through the observation of right circular polarization of internal bremsstrahlung using a low-energy circular polarimeter with a Ge/sup 71/ source. (W.D.M.)