Yu.D. Prokoshkin

Radiative capture of stopped negative pions by nuclei

Abstract Experiments aiming at the radiative capture of stopped π − mesons by nuclei are described. The probability of the process detected is 2 · 10 −2 and depends weakly upon nuclear charge and mass. The energy spectrum of γ -quanta emitted in the capture turned out to be “hard”. The mean γ -energy was about 80 MeV.

On the charge exchange of stopped negative pions on complex nuclei

Abstract It is shown that stopped π−-meson charge exchange on complex nuclei is sharply suppressed.

π0-meson production by protons on complex nuclei

Abstract The angular distribution of γ-quanta from the decay of π0-mesons produced in proton-nucleus collisions has been measured with a γ-telescope. The values of the π0-meson production cross section and the energy dependence of the carbon cross section in the 175–665 MeV region have been obtained.

Pion absorption in hydrogenous substances

SummaryThe transfer process from hydrogen to other nuclei for negative pions stopped in hydrogenous substances is investigated. The intensity of this transfer is sharply increased with, theZ value of the atom chemically bound with hydrogen.RiassuntoSi analizza il processo di trasferimento dall‘idrogeno agli altri nuclei dei pioni negativi che si arrestano in sostanze idrogenate. L‘intensità di questo trasferimento aumenta nettamente col valore diZ dell‘atomo legato chimicamente all‘idrogeno.

Measurements of stopped π- meson absorption probability by bound hydrogen nuclei

SummaryThe probability of stopped π-meson absorption by hydrogen nuclei in polythene (CH2) has been measured by the relative method when comparing υ-quantum yields from hydrogen and polythene targets with the same dimensions and stopping powers.RiassuntoSi è misurata, col metodo relativo di comparazione delia produzione di quanti y da bersagli di idrogeno e politene delia stessa dimensione e potere d’arresto, la probabilità di assorbimento dei mesoni π- arrestati dai nuclei di idrogeno nel politene (CH2).

gp−Star detector

Abstract A scintillation detector possessing the selective sensitivity to π -mesons is described. The detector records the stars due to π -mesons coming to rest.

π+-Meson decay curve in the region of large lifetimes

Abstract π+-meson decay curve (π+→μ++v) has been measured by means of a scintillation counter system and a high-speed multi-ray oscilloscope. The trap for positrons being used, the background resulting from the μ+→e+ decay was reduced to the level 3 sx 10-6. The decay curve has been followed up to 167τ (where τ is the main lifetime of π+-meson), no deviation from the exponential law was observed.

Angular correlation of gamma-quanta produced by negative pions stopping in hydrogen

Abstract The angular correlation of gamma-quanta emitted in the capture of stopped π − mesons in hydrogen is measured. The measurements were performed by using scintillation and gas-discharge counter hodoscopes. The value of the mass differences between charged and neutral π mesons was found to be 4.6034±0.0052 MeV/ c 2 . An upper probability limit for the production of a second neutral π meson, which has the mass in the range of 135 – 138 MeV/ c 2 has been determined.

MASS DIFFERENCE ON THE NEGATIVE AND NEUTRAL PIONS

The angular correlation of gamma-quanta emitted in the capture of stopping π--mesons by protons was measured. Measurements were made with a hodoscope of scintillation and gas discharge counters. The mass difference of the negative and neutral pions turned out to be (4.6034±0.0052) MeV/c2.

Experimental evaluation of the π+→π0+e++ν decay probability

SummaryBy means of γ-γ coincidences it has been shown that the probability of positive pion β-decay does not exceed 7·10−8 of the probability of muon decay of pion. For the constant G which determines the intensity of this process in the case of vector current conservation the following evaluation has been obtained:G < 2.5Gβ, whereGβ is the constant of weak vector β-interaction.RiassuntoA mezzo di coincidenze γ-γ si è dimostrato che la probabilità del decadimento β del pione positivo non supera 7·10−8 volte la probabilità del decadimento del pione in un muone. Per la costanteG, che determina l’intensità di questo processo nel caso della conservazione della corrente vettoriale, si è ottenuto il seguente valore: G < 2.5Gβ, in cuiGβ è la costante della interazione β vettoriale debole.