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Vol. 15, No. 5 (1959)

1959-03-05
Topics
CONTENT
THE PROPERTIES, PRODUCTION AND DECAY OF STRANGE PARTICLE
HO AN-SHING
1959, 53 (5): 219-229. doi: 10.7498/aps.15.219
Abstract +
The cloud-chamber has a volume 30×30×10 cm3 in a maguetic field of 6200 gauss, which is operated at a 3185m mountain altitude. In a set of 30000 pairs of photographs taken, 105 events of the decay of neutral V particles and 21 of the decay of charged particles wore observed. It is seen that 16 events have been classified as due to the decay of ∧0 particles, 26 as due to the decay of θ10 particles, one as decay of a θ20 particle and 62 as nonclassified. We have studied the following properties of the ∧0 and θ0 particles, the results of which are summamed as follows: 1) Q values Q(Λ0)=(36.2±2.5)Mev, Q(θ10)=(233±11)Mev; 2)mean lifotimes τ(Λ0)=(3.19-0.92+2.42)×10-10sec,τ(θ10)=(1.14-0.27+0.49)×10-10sec; 3) The Momentum distributions found for ∧0 and θ0 particles have no appreciable difference with earlier results;4) N(∧0)/N(θ10)=0.51±0.22 (corrected number in lead);5) The angular distributions of the decay products of the ∧0 and θ0 particles in the rest system have no marked asymmetry;6) The lifetime of one θ20 particle is estimated to be :10-9 sec. in the rest system. The decay mode of this θ20 particle is probably θ20→π-+π++π0 or θ20→π±+μ?+ν.
A STUDY OF Λ0 AND θ0 PARTICLES PRODUCED IN Pb AND Al
Lü MIN, CHENG JEN-CHI, LI HO-NIAN
1959, 53 (5): 230-245. doi: 10.7498/aps.15.230
Abstract +
Two experiments on V0 particles were carried out with a multiplate cloud chamber during 1955-1957. A total of 550 V0 particles have been found. 67 ∧0 and 44 θ0 particles are classified according the a-∈ method. Of them 58 ∧0 and 38 θ0 were produced in Pb, 9 ∧0 and 6 θ0 were produced in Al. The following results have been obtained: (1) The decay angle in the center of mass system, of ∧0 or θ0 is uniformly distributed. The correlation angle between the production plane and the decay plane is distributed also uniformly. No information can be obtained that the spin of the V0particles are larger than 1/2. (2) No asymmetry of angular dis-tribution is seen thus showing nonconservation of parity for the decays of the ∧0 particles produced in Pb. For ∧0 produced in Al some indication of asymmetry is noted. (3) The hyperon tends to go backward in the associated production process from the consideration of the momentum spectrum, and production angular distribution. (4) The following lifetimes are obtained: τ(Λ0)=(3.39-0.440.63)×10-10 sec,τ(θ0)=(0.86-0.160.26)×10-10 sec. (5) N(∧0):N(θ0)=1.4. (6) The total cross section for strange particle production is estimated to be of the order of 0.8 mb/nucleon, both for Pb and Al. (7) The Pb nucleus is more effective than the Al nucleus for producing a V0 particle, when we consider the percentage of the V0 with respect to the total number of secondary particles.
ON THE ANGULAR DISTRIBUTION OF THE DECAY PRODUCTS OF PARTICLE OF ARBITRARY SPIN
CHEN J. M., HO T. H., SAN D. C., TZU H. Y.
1959, 53 (5): 254-261. doi: 10.7498/aps.15.254
Abstract +
The angular distribution of the decay products of particle of arbitrary spin decaying into a particle of spin zero and a particle of spin 1/2 is investigated. The expressions for the expansion coefficients are derived. It is found that coeffieients of terms of even order spherical harmonics are independent of the detailed form of the interaction Hamiltonian inducing the decay process. But the expansion coefficients of terms of odd order spherical harmonics depend on a parameter α, which is a measure of the interference between the parity conserving and the parity nonconserving interaction. The maximum values which can be taken by the various coefficients are given. It is found that the maximum values of the even coefficients increase with the value of the spin of the initial particle, while those of the odd coefficients decrease correspondingly. The expression for the density matrix of the initial particle as a function of these expansion coefficients is also given which can be used to determine the state of polarization of the initial particle and the interference between the parity conserving and parity nonconserving interactions, when the expansion coefficients are known.
THE RADIATIVE CAPTURE OF μ-MESON BY PROTON
DAI Y. B., SAN D. C., HO T. H., TZU H. Y.
1959, 53 (5): 262-268. doi: 10.7498/aps.15.262
Abstract +
The radiative capture of μ-meson by proton is treated by using the renor-malized universal Fermi interaction of V-A type and Zeldowich's theory of μ mesic hydrogen. Contrary to the result of Lee, Huang and Yang, it is found that, if the effect of the strong interaction is neglected, then it is impossible for photon being emitted during the capture. The influence of the strong interaction consists of two respects, namely: the effect of the magnetic moment of the nucleon and the renormalization effect on the universal Fermi weak interaction. The effect of the anomalous magnetic moment is negligible. However, the contribution of proton to the emission of photon is not at all small in comparison with that of the μ-meson duo to the renormalization effect on the universal Fermi weak interaction. As a result, the photons emitted are no longer 100% right hand polarized. It is estimated, that only 80% of the photons has a spin parallel to its momentum. The radiative capture rate of the μ-meson by proton is 1/(1.6×105) of thetotal capture rate.