Simultaneous exposures have been made of Ilford Gr.5 emulsion to magnetically analyzed mesons as well as to hydrogen and helium nuclei of various velocities. Measurements of the particle ranges have been made for equivalent proton energies of 1.295 MeV to 700 MeV. Individual particle momenta were known to better than one part in a thousand. Especial care was taken to maintain the emulsion density at an accurately measured value. Curves and formulae used for converting particle ranges to their proton equivalents at other emulsion densities are given. Detailed procedures for correcting ranges of particles that traverse gaps between pellicles are described. Various effects that influence range measurements are discussed. Comparisons with existing data are made. Good agreement is found to exist only when the emulsion densities are known, and a correct procedure is employed to adjust the measured ranges to standard conditions. An empirical correction of the Vigneron range table is made.

/pdf/the-range-energy-relation-in-emulsion-1gtwzh346u.pdf

The Range-energy relation in emulsion

Some 3 300 K-meson decay events have been studied in a large stack exposed to the positive K-beam at the Berkeley 6 GeV Bevatron. The events have been selected in an unbiassed way and have been used to yield preliminary information concerning the shape of the energy spectrum of the charged particle emitted in the rarer 3-body decay-modes Τ′, κ (KΜ3) and KΒ. The relative abundance of the, decaymodes has been estimated the results being summarized in the Table

	
Mode
	
τ
	
τ′
	
Kμ2
	
χ(Kμ2)
	
ϰ(Kμ3)
	
Kβ


Abundance (%)
	
6.77±0.45
	
2.15±0.42
	
57.0±2.6
	
23.2±2.2
	
5.9±1.3
	
5.1±1.3
	


. The number of interactions observed over the first 4 cm from decay of the π-mesons secondary to κ-decay yields the surprisingly short estimate of the interaction M.F.P. of (11.1 ± 2.4) cm. This appears to be in significant disagreement with that found for artificial π+-mesons by other workers, namely 27 cm in the same energy region, (109 ÷ 82) MeV.

The relative frequencies of the decay modes of positive k-mesons and the decay spectra of modes KΜ3, Τ′ and KΒ

The decay of τ and θ particles is discussed on the hypothesis that the amplitude for an isotopic spin change of ΔT in τ and θ decay to pions should decrease with increasing ΔT, the transition ΔT = ½ being dominant. Assuming zero spin for τ and θ, the large difference between θ0 and θ+ lifetimes and the τ' τ branching ratio (predicted as 0.32) both agree well with this hypothesis.

https://iopscience.iop.org/article/10.1088/0370-1298/69/7/304/pdf

Isotopic Spin Changes in τ and θ Decay

This article surveys our empirical knowledge of the production processes, the nuclear interactions and the decay processes of K particles and hyperons, as this appeared at the close of 1956, and interprets these phenomena within the framework of the charge-independent classification scheme proposed by Gell-Mann and by Nishijima for these `strange particles'. The assignment of a `strangeness' quantum number to each strongly interacting particle is a deep-lying aspect of this scheme, and the main qualitative features of the empirical data allow a direct interpretation in terms of a law of conservation of strangeness through all strong interactions. Where appropriate, more detailed analyses of the phenomena are made on the assumption that charge independence holds for these strong interactions. The evidence on decay processes for K particles and hyperons is discussed in some detail. These processes violate the strangeness conservation law and also involve changes in the total isotopic spin for those cases where this quantity is relevant for the final particles. The success of Gell-Mann's ?T = ? rule in accounting for certain aspects of the decay data is considered for each of the latter cases; this rule is given a simple origin in Schwinger's model for strange particle decay processes, which is discussed briefly. The implications of symmetry between particle and antiparticle, as pointed out by Gell-Mann and Pais for the neutral K particles and their decay modes, is also discussed in some detail, together with an account of the experimental data on long-lived K? particles and anomalous K? decay modes. Indications in the data which bear on the spin and parity values for K particles and hyperons are stressed, especially for the decay modes associated with ? and ? particles. Although it is shown that the products of ? and ? decay necessarily differ in spin or in parity, a great similarity has been found concerning all other properties of the ? and ? particles, and the proposals which have been made to account for this situation are surveyed. For the ?? particle, observations on bound ?? hypernuclei provide much information relevant to the ??-nucleon interaction and the ?? spin and parity, and this is also discussed in some detail. A section is devoted to discussion of `anomalous events' for which no interpretation is known in terms of the interactions of the well-established particles. These events and the possibility that heavier unstable particles or perhaps resonance states may exist have an obvious importance, of special relevance for attempts to construct a theoretical foundation leading naturally to the Gell-Mann-Nishijima scheme. A brief discussion of the preliminary attempts to establish such a foundation is given. An appendix has been added in proof to discuss the recent observations on the failure of parity conservation and of charge conjugation invariance in certain weak decay processes, and the effects which a failure of these symmetry properties also for strange particle decays would have on the arguments made and the conclusions reached in this survey.

K Mesons and Hyperons their strong and weak interactions

A number of independent accurate measurements of the masses of light mesons are critically reviewed. Assuming the positive-and negative-charged mesons to have equal masses, best values for the pion and muon masses can be calculated. It is found that the negative π- and μ-mesic X-ray energies measured by K absorption edges can be combined with the mass difference between the positive pion and muon to give a result with a standard deviation approximately one third of the assigned errors of the best previous measurement. All the results are in satisfactory agreement and can be combined in the usual way. The mass results are as follows:Mμ=(206.86±0.11) me;Mπ==(273.27±0.11) me. Experimental data on the mean lives, spins, parities, and decay modes are also reviewed and the results are given. The measurements of the masses of the various K-mesons are obtained in several ways:MKπ2=(966.0±1.5) me;MKπ2=(965.3±1.9) me;MΣ=(966.8±0.4) me. There is at present no evidence for a difference in the masses to a precision of 1 ÷ 2 me. Results on the Σ+-Σ− and τ+ masses and lifetimes and the analysis of τ+ decay are discussed. At present the experimental equality of these particles seems to be contradictory to assigning a spin of less than 2. The cosmic-ray data on the ϑ0 lifetime are reviewed and recent results on artificially-produced ϑ0’s are discussed. The hyperon mass data are reviewed.MΔδ=(2181.74±0.35) me;MΣδ=(2 327.4±1.0) me. The latest data on a Σ+ − Σ− mass difference and their mean lives are presented.

The masses of light mesons, K-mesons and hypersons in 1956

A large emulsion stack, exposed at high altitude, has been used to study the decaymodes of K-particles which produce a single charged secondary. The 5 decay modes, K
 μ
 , χ, ϰ and τ′ have been recognized from the nature and energy of the charged secondary. The masses of the parent particles of the two-body decay modes, K
 μ
 and χ found from the mean range of the charged secondary are (976±7) me and (969±3) me respectively. Independent values derived from measurements of the scattering of the secondary track near the decay point are (954±17) me and (972±15) me respectively. The reliability of these mass values is discussed. An examination of the relative frequency of the decay modes in these experimental conditions indicates that the K
 μ
 -and χ-modes constitute respectively about 67 % and 20 % of all the K-particle decays: the Kβ, ϰ- and τ′-modes being present to about 9 %, 3 %, and 1 % respectively.

On the masses and modes of decay of heavy mesons produced by cosmic radiation

The results from the analysis of 75 stopped τ-meson decays, found in a stack of emulsions exposed to the Berkeley Bevatron, are discussed. Special attention is paid to the effects of the finite dimensions of the stack, and a brief analysis of the problem is given. The experimental results are compared with those from other laboratories, and the authors conclude that there is no good evidence that the spectrum of the π-mesons from τ-decay is in accord with either of those which have been predicted for the two lowest spin-parity combinations: 0- and 1+.

Remarks on the analysis of τ-meson experiments

A Τ-decay with a secondary of extremely low energy

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On the masses and modes of decay of heavy mesons produced by cosmic radiation

Remarks on the analysis of τ-meson experiments

A Τ-decay with a secondary of extremely low energy