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We have investigated $\ensuremath{\eta}$ production in the reaction ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}p\ensuremath{\eta}$ at 1050 and 1170 MeV/c, and in the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\eta}$ at 1170 MeV/c. We obtain the following partial cross sections for the reaction ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\eta}$ followed by the charged decay $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}:9.5\ifmmode\pm\else\textpm\fi{}1.5$ \ensuremath{\mu}b for 1050-MeV/c incident ${\ensuremath{\pi}}^{+}$; 53.3\ifmmode\pm\else\textpm\fi{}5.0 \ensuremath{\mu}b for 1170-MeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}$; 15.9\ifmmode\pm\else\textpm\fi{}1.9 \ensuremath{\mu}b for 1170-MeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}$. From our ${\ensuremath{\pi}}^{+}$ data we find that we need four $I=\frac{3}{2}$ amplitudes in order to obtain good agreement with our mass and angular distributions and to reproduce the threshold behavior of the cross section. We find the dominating amplitude to be that representing the reaction ${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\Delta}(1238)$, $\ensuremath{\Delta}(1238)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}p$, where the $\ensuremath{\eta}$ and the $\ensuremath{\Delta}(1238)$ are produced in $s$ wave. The four amplitudes are extrapolated to higher energies where the predicted mass and angular distributions and cross sections are compared with the available data. From our ${\ensuremath{\pi}}^{\ensuremath{-}}$ data we find that in addition to the four $I=\frac{3}{2}$ amplitudes (determined from the ${\ensuremath{\pi}}^{+}$ data), one $I=\frac{1}{2}$ amplitude is required: the amplitude in which all particles are in relative $S$ states. We find that this $I=\frac{1}{2}$ amplitude in fact dominates the ${\ensuremath{\pi}}^{\ensuremath{-}}$ reaction. We see no evidence for production of an ${N}^{*}(1550)\ensuremath{\rightarrow}\ensuremath{\eta}p$ resonance. We are able to parametrize the cross sections for $\ensuremath{\pi}p\ensuremath{\rightarrow}\ensuremath{\pi}p\ensuremath{\eta}$ from threshold to 4 BeV/c.

We have measured the differential and total cross sections of the reaction π−p→Σ−K+ with 1170−MeVc pions incident on the Alvarez 72-in. hydrogen bubble chamber. Using 1338 events, we find the coefficients in the Legendre expansion of the differential cross section dσdΩ=A0P0+A1P1+A2P2 to be A0=18.38±0.50 μb/sr, A1=7.54±0.96 μb/sr, and A2=11.10±1.21 μb/sr, corresponding to a total cross section σ=231±6 μb. No polynomials higher than P2 are needed. The decay asymmetry α−P− of the decay Σ−→nπ− is consistent with zero. Using previously reported results for the differential cross sections of the reactions π−p→Σ0K0 and π+p→Σ+K+ at 1170−MeVc incident pion momentum, we have compared the results with the predictions of the hypothesis of charge independence. We have found no significant violations of that hypothesis. We have compared the measured polarization of the Σ0 with the prediction from the charge-independence hypothesis, using the measured differential cross sections of the three production reactions and the polarization of the Σ+, as determined in the decay Σ+→pπ0. The results agree with the prediction.

We have studied the time distributions of 242 leptonic decays of neutral $K$ mesons produced in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\overline{K}}^{0}+n$. For the $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ parameter $x$ we find $\mathrm{Re}(x)={0.22}_{\ensuremath{-}0.09}^{+0.07}$, $\mathrm{Im}(x)=\ensuremath{-}0.88\ifmmode\pm\else\textpm\fi{}0.08$.

In the course ot studying a large number of decays of hyperons, produced in a hydrogen bubble chamber by 1.23 Bev/c pious, an uanambiguous case or a LAMBDA undergotng beta decay was found. Tbe events at the various vertices in the photograph are analyzed. (W.D.M.)

In this letter the author describes a measurement of the absolute decay rate {Gamma}{sub 2}({+-}0) {approx_equal} {Gamma}(K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}). The result is based on 16 events of the type {pi}{sup -} p {yields} {Lambda}K{sup 0} followed by {Lambda} {yields} p{pi}{sup -} and K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, and 2608 double-vec events {pi}{sup -} p {yields} {Lambda}K{sup 0} with {Lambda} {yields} p{pi}{sup -} and K{sub 1}{sup 0} {yields} {pi}{sup +}{pi}{sup -}.

The experimental procedures and cutoffs that were applied to a sample were given in detail and the results compared with theoretical predictions. (C.E.S.)

We report the final results of a study of the time distribution of decays of neutral $K$ mesons produced in the reaction ${K}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\overline{K}}^{0}+n$. We present independent results based on 81 electronic and 38 muonic decays. Combining these with 133 ambiguous events, we find for the $\ensuremath{\Delta}S=\ensuremath{-}\ensuremath{\Delta}Q$ parameter $x$ the value $\mathrm{Re}(x)={{0.25}_{\ensuremath{-}0.09}}^{+0.07}$, $\mathrm{Im}(x)=0.00\ifmmode\pm\else\textpm\fi{}0.08$. This value lies about 2.5 standard deviations away from the point $x=0$, and to this extent our experiment suggests a violation of the $\ensuremath{\Delta}S=\ensuremath{\Delta}Q$ rule. In the course of an investigation of background processes, we identify and measure the rate of the radiative decay ${K}_{S}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$.

Author(s): Crawford, Frank S.; Cresti, Marcello; Good, Myron L.; Gottstein, Klaus.; Lyman, Ernest M.; Solmitz, Frank T.; Stevenson, M. Lynn; Ticho, Harold.

Author(s): Crawford, Frank S.; Cresti, Marcello; Good, Myron L.; Solmitz, Frank T.; Stevenson, M.Lynn.

We have measured the absolute differential cross section $\frac{d\ensuremath{\sigma}}{\mathrm{dK}}$ for production of delta-ray electrons by 1.12-Bev/c negative pions incident on a 10-in. liquid hydrogen bubble chamber, for values of the $\ensuremath{\delta}$-ray kinetic energy $K$ between 32 Mev and the kinematical upper limit of 62 Mev. The results are in agreement with the theoretical prediction of Bhabha. We find an integrated cross section $\ensuremath{\sigma}(Kg32 \mathrm{Mev})=1.37\ifmmode\pm\else\textpm\fi{}0.17 \mathrm{mb}.$ This exceeds the theoretical prediction of 1.17 mb by a factor 1.17\ifmmode\pm\else\textpm\fi{}0.15.The monoenergetic electron contamination of the pion beam has been determined by counting electron-induced $\ensuremath{\delta}$ rays. The monoenergetic and non-monoenergetic contributions to the muon contamination have both been determined by combining a determination of the number of muon-induced $\ensuremath{\delta}$ rays with a measurement of the curvature distribution of beam tracks. The method is described in detail.

Six cases of DELTA hyperons interacting with protons in a liquid hydrogen bubble chamber were found. The classes of DELTA interactions were DELTA + p yields DELTA + p (4 events) and DELTA + p yields SIGMA /sup +/ + n (2 events). No examples of the DELTA + p yields delta /sup 0/ + p reaction were found. The cross sections are computed for the reactions and for the inverse reactions. (W.D.M.)

The method recently proposed by Lee and Yang for determining the spin of the LAMBDA hyperon is applied to 614 decays of the type LAMBDA yields pi - + p. The A's were produced in a 10-inch liquid hydrogen bubble chamber via the reaction pi - + p yields K/ deg + LAMBDA . The method makes possible an absolute determination of the A spin without assumptions other than that angular momentum is conserved in the decay. It is concluded that the LAMBDA spin is 1/ 2. (W.D. M.)

The charge symmetry of K/sup +/ and K/sup 0/ mesons was tested by comparing e (as Fe/sup 59 /sup +/ and e (as Fe/sup 59 /sup -/ interactions at 1.23 Bev/c in the 72-in. deuterium bubble chamber. About 350 events of the type e (as Fe/sup 59 /sup +/ + d and up to st r K/sup +/ + in each case). (or / occurred in pu /sup 0/) + p and appeevents of the type e (as Fe/sup 59 /sup -/ + d and up to st r K/sup 0/ + in each case). (or /occurred in pu /sup 0ppared. Total cross sections, angular distributions, momentum spectra, and lambda decay asymmetries show no deviations from charge symmetry. Details on anglemomentum distributions and decay asymmetries are given. (auth)

The decay reaction LAMBDA yields p + pi /sup -/ was studied, and it is concluded that the degree of nonconservation of parity is very large and that charge conjugation invariance is also violated. (L.T.W.)

Information is reported on the analysis of 185 events of the type pi - + p -- LAMBDA /sup o/ +K/sup o and LAMBDA /sup o/ > p+ pi /sup -, produced by pions of 1.23 bev/c, leading to 375 Mev/c LAMBDA 's in the c.m. system. (J.H.M.)