Strange-Particle Production by1.7−GeVcπ+on Protons

Abstract

The Princeton-Pennsylvania accelerator 15-in. hydrogen bubble chamber was used to investigate r+p associated production a t 1.7 GeV/c. Approximately 4000 events were found; about half of these were in the Z+Kf channel. The AKf?r+ channel dominates the remaining half of the data. We find evidence for the existence of a T = 1 hyperon resonance a t 1475f 15 MeV with a width of 3 0 f 15 MeV in the AK+r+, Z+K+7r0, Z°K+?r+, and ~~+ z " c h a n n e l s .The cross sections of the strange-particle channels and the branching ratios of various resonances are also presented.

Production of the “ K − pp ”-like structure in the d ( π + , K + ) reaction at 1.69 GeV/ c

“…The production cross-sections in the forward angles of the p(π + , K + )Σ + at 1.58 and 1.69 GeV/c and p(π + , K + )Σ(1385) + were compared with the previous measurements, and we confirmed they were consistent within the large statistical errors in the old measurements [34]. We made an attempt to reproduce the double differential cross-section d 2 σ/dΩdM with a Monte Carlo simulation by using the differential cross-sections dσ/dΩ of each elementary reaction obtained in past experiments [31,35,36] with a smearing by the nucleon Fermi motion in a deuteron. Here we used the cross-sections of the π − p → K 0 X reaction assuming isospin symmetry for the π + n → K + X reaction.…”

“…Exceptions are the cases for π + p → K + Σ + and π + p → K + Σ(1385) + : we performed the fits to the data in Ref. [35,36]. In the case of three-body reactions such as π + n → K + Λπ, final state particles are distributed in a three-body phase space.…”

Search for exotic baryons in double radiative capture on pionic hydrogen

“…The catalyst for the original work was the difficulty of the multiplet assignment for the Σ(1480). Azimov suggested identifying the strangeness S = −1 Σ(1480) [11,12], the strangeness S = −1 Λ(1330) [13,14], and strangeness S = −2 Ξ(1620) [15], as three members of a new low-lying exotic baryon octet. 1 Azimov then used the Gell-Mann-Okubo mass formula to estimate the mass of the lowest-lying non-strange member of the multiplet to be roughly 1100 MeV/c 2 .…”

Status of K−pp Search Experiments

“…5, the missing-mass spectrum of the d(π + , K + ) reaction at 1.69 GeV/c is shown. As expected, we can find three major structures: quasi-free Λ production, quasi-free Σ + and Σ 0 productions, and Based on the available cross section data [17,21,22] on these elementary processes, we carried out a simulation of these quasi-free processes taking account of deuteron Fermi motion. The result is also shown in Fig.…”