R. Olszewski

Pion production by pions in the 16O(π+,π+π−) reaction at Tπ+ = 280 MeV

The results of an experiment of pion-induced pion production on 16O at a laboratory energy of 280 MeV are reported. The four-fold-differential cross section, d4σdΩπ+dΩπ+dEπ+dEπ, was measured, and the missing mass, Mx, for the reaction 16Ofs(π+,π+π−) at laboratory angles of 50°, 80° and 115° for the π−, and from 22° to 128° for the π+ was deduced. The angular and energy distributions of the many-fold differential cross sections are compared with an A(π+,π+π−) model for the reaction. The observed cross sections are reproduced in magnitude and shape when the theoretical calculations consider a proper pion dispersion relation, \gw(q), inside the nuclear medium. The total cross section, deduced by integrating the four-fold differential cross sections, is compared with the available theoretical predictions for the 16O(π+, π+π−) reaction.

Measurement of the 16O

Results from a coincidence measurement of the /sup 16/O(..pi../sup +/,..pi../sup +/..pi../sup -/) reaction at T/sub ..pi..//sub =/ = 280 MeV are reported, the first of this class. The energy- and angular-integrated cross section was found to be 2950 +- 450 ..mu..b and is compared with theoretical predictions. Low-energy positive-pion intensities are found to be much higher than those yielded by a four-body phase-space calculation.

SPIN-TRANSFER MEASUREMENTS OF THE PI DPP REACTION SPANNING THE DELTA RESONANCE

The first spin-transfer observables for the {pi}{bold d}{r arrow}{bold p}{ital p} reaction have been measured at a number of energies spanning the {Delta} resonance in this system. These parameters correspond to {ital K}{sub {ital S}{ital L}} and {ital K}{sub {ital S}{ital S}} of the {ital p}{bold p}{r arrow}{bold d}{pi} reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.

Energy dependence of T20 and τ21 in πd↘ elastic scattering

Angular distributions of the tensor analyzing powers T 2 0 and τ2 1 have been measured for πd↘ elastic scattering, in a single scattering experiment employing a tensor polarized deuteron target. Measurements of T 2 0 were obtained for pion bombarding energies of 134, 151, 180, 220, and 256 MeV. Measurements of τ2 1 were obtained for pion bombarding energies of 134, 180, and 220 MeV. The results are compared with three‐body calculations where effects relating to pion absorption are seen to play an important role.

Spin-transfer measurements of the. pi. rvec d r arrow rvec p p reaction spanning the. Delta. resonance

The first spin-transfer observables for the {pi}{bold d}{r arrow}{bold p}{ital p} reaction have been measured at a number of energies spanning the {Delta} resonance in this system. These parameters correspond to {ital K}{sub {ital S}{ital L}} and {ital K}{sub {ital S}{ital S}} of the {ital p}{bold p}{r arrow}{bold d}{pi} reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.

Spin-transfer measurements of the pi d

The first spin-transfer observables for the {pi}{bold d}{r arrow}{bold p}{ital p} reaction have been measured at a number of energies spanning the {Delta} resonance in this system. These parameters correspond to {ital K}{sub {ital S}{ital L}} and {ital K}{sub {ital S}{ital S}} of the {ital p}{bold p}{r arrow}{bold d}{pi} reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.

Spin-transfer measurements of the πd→→p→preaction spanning the Δ resonance

The first spin-transfer observables for the {pi}{bold d}{r arrow}{bold p}{ital p} reaction have been measured at a number of energies spanning the {Delta} resonance in this system. These parameters correspond to {ital K}{sub {ital S}{ital L}} and {ital K}{sub {ital S}{ital S}} of the {ital p}{bold p}{r arrow}{bold d}{pi} reaction for incident proton energies ranging from 600 to 800 MeV. Such data can provide an important constraint on the determination of the partial-wave amplitudes describing this fundamental reaction. The discrepancies between our data, theoretical predictions, and values calculated from published partial-wave amplitudes demonstrate the need for further work in this area.

Multinucleon pion absorption in the He4(,ppp)n reaction

Three-proton emission cross sections for the {sup 4}He({pi}{sup +},{ital ppp}){ital n} reaction were measured at an incident pion kinetic energy of {ital T}{sub {pi}}{sup +}=165 MeV over a wide angular range in a kinematically complete experiment. Angular correlations, missing momentum distributions, and energy spectra are compared with three- and four-body phase-space Monte Carlo calculations. The results provide strong evidence that most of the three-proton coincidences result from three-nucleon absorption. From phase-space integration the total three-nucleon absorption cross section is estimated to be {sigma}{sup 3{ital N}}=4.8{plus minus}1.0 mb. The cross section involving four nucleons is small and is estimated to be {sigma}{sup 4{ital N}}{lt}2 mb. On the scale of the total absorption cross section in {sup 4}He, multinucleon pion absorption seems to represent only a small fraction.

Multinucleon pion absorption in theHe4(π+,ppp)nreaction

Three-proton emission cross sections for the {sup 4}He({pi}{sup +},{ital ppp}){ital n} reaction were measured at an incident pion kinetic energy of {ital T}{sub {pi}}{sup +}=165 MeV over a wide angular range in a kinematically complete experiment. Angular correlations, missing momentum distributions, and energy spectra are compared with three- and four-body phase-space Monte Carlo calculations. The results provide strong evidence that most of the three-proton coincidences result from three-nucleon absorption. From phase-space integration the total three-nucleon absorption cross section is estimated to be {sigma}{sup 3{ital N}}=4.8{plus minus}1.0 mb. The cross section involving four nucleons is small and is estimated to be {sigma}{sup 4{ital N}}{lt}2 mb. On the scale of the total absorption cross section in {sup 4}He, multinucleon pion absorption seems to represent only a small fraction.

Measurement of the /sup 16/O(. pi. /sup +/,. pi. /sup +/. pi. /sup -/) reaction at T/sub. pi. //sub =/ = 280 MeV

Results from a coincidence measurement of the /sup 16/O(..pi../sup +/,..pi../sup +/..pi../sup -/) reaction at T/sub ..pi..//sub =/ = 280 MeV are reported, the first of this class. The energy- and angular-integrated cross section was found to be 2950 +- 450 ..mu..b and is compared with theoretical predictions. Low-energy positive-pion intensities are found to be much higher than those yielded by a four-body phase-space calculation.