Chronology of Milestone Events in Particle Physics

Chronology of Milestone Events in Particle Physics - ALSTON 1961E

About Contents Introduction Synopsis Search Subject Index Summaries Texts

Nobel prize to L. W. Alvarez awarded in 1968 "for his decisive contribution to elementary particle physics, in particular the discovery of a large number of resonance states, made possible through his development of the hydrogen bubble chamber technique and data analysis''

ALSTON 1961E

Alston, M.H.; Alvarez, L.W.; Eberhard, P.H.; Good, M.L.; Graziano, W.; Ticho, H.K.; Wojcicki, S.G.;
Study of Resonances in the Σ π System
Phys. Rev. Lett. 6 (1961) 698; CERN HEP-62, P. 311 (1962);

Motivation
Recently a T = 1 resonance in the Λ π system, called Y₁^*, has been observed with a mass of 1385 MeV. Two types of resonances have been predicted that might relate this observation to other elementary-particle interactions:

(1): P_3/2 resonances in the Λ π and Σ π systems predicted by global symmetry, corresponding to the (3/2, 3/2) resonance of the π N system,
(2): a spin-1/2 Y π resonance resulting from a bound state in the anti-K N system. The position and the width of the observed Y resonance agree with both theories, but since the spin and parity have not yet been determined, we cannot distinguish between the two theoretical interpretations.

Global symmetry (including a phase-space factor) predicts a branching ratio R = (Y_l^*± → Σ^o π^±)/ (Y₁^*± → Λ π^±) = (Y₁^*± → Σ^± π^o)/(Y₁^*± → Λ π^±) = 1/4(0.225) ~ 5%. The anti-K N bound-state model suggests values of R considerably larger than 5%. However, when nonzero effective ranges are taken into account, R can become quite small, especially if the Σ Λ parity should be odd.
To investigate these possibilities, we have continued our study of K^– p interactions at 1.15 BeV/c in the Lawrence Radiation Laboratory 15-in. hydrogen bubble chamber by studying events in which a Σ is observed. (Extracted from the introductory part of the paper.).

Accelerator LBL Detectors HBC-15IN

Related references
See also
M. H. Alston et al., Phys. Rev. Lett. 5 (1960) 520;
O. Dahl et al., Phys. Rev. Lett. 6 (1961) 142;
P. Bastien, M. Ferro-Luzzi, and A. H. Rosenfeld, Phys. Rev. Lett. 6 (1961) 702;
H. J. Martin, L. B. Leipuner, and W. Chinowsky, Phys. Rev. Lett. 6 (1961) 283;
J. P. Berge et al., Phys. Rev. Lett. 6 (1961) 557;

Reactions

K^– p Σ^o π⁺ π^– 1.15 GeV (P_lab) cs

K^– p Σ⁺ π^– 1.15 GeV (P_lab) cs

K^– p Σ^– π⁺ 1.15 GeV (P_lab) cs

K^– p Σ⁺ π^o π^– 1.15 GeV (P_lab) cs

K^– p Σ^– π⁺ π^o 1.15 GeV (P_lab) cs

K^– p Σ⁺ π⁺ 2π^– 1.15 GeV (P_lab) cs

K^– p Σ^– 2π⁺ π^– 1.15 GeV (P_lab) cs

K^– p Σ⁺ 2π^o π^– 1.15 GeV (P_lab) cs

K^– p Σ^– π⁺ 2π^o 1.15 GeV (P_lab) cs

K^– p Σ^o π⁺ π^o π^– 1.15 GeV (P_lab) mass

K^– p Σ⁺ π⁺ 2π^– 1.15 GeV (P_lab) mass

K^– p Σ^– 2π⁺ π^– 1.15 GeV (P_lab) mass

K^– p Σ(1385 P₁₃)⁺ π^– 1.15 GeV (P_lab)

K^– p Σ(1385 P₁₃)^– π⁺ 1.15 GeV (P_lab)

K^– p Λ(1405 S₀₁) π^o 1.15 GeV (P_lab)

K^– p Σ(1385 P₁₃)^o π^o 1.15 GeV (P_lab)

Particles studied

Λ(1405 S₀₁) ex, mass, qn

Record comments
First evidence for the Λ(1405 S₀₁) resonance.

New Comments List of Comments

About Contents Introduction Synopsis Search Subject Index Summaries Texts