Positive pion absorption was studied in an almost 4p geometry allowing simultaneous measurements of various charge and neutral multiplicities. Total absorption cross sections and its decomposition into the most important channels is determined. The results are presented for N, Ar and Xe nuclei at incident pion energies of 118, 162 and 239 MeV. The role of multinucleon emission in the absorption process is emphasized.

Unpolarized cross sections and vector target analyzing powers for the 7 (Li) over right arrow(pi (1). pi (+t) p) proton knockout reaction were measured using a vector polarized (LiH)-Li-7 target and a 240 MeV pi (+) beam at the piM 1 channel of PSI. Typical target polarizations were >30% for Li-7. Coincident pi (+)-p data are presented for three emitted pion angles (60 degrees, 85 degrees, and 108 degrees). For each pi (+) angle coincident data with adequate statistics were obtained for three proton angles near the quasifree pi (+)-p angle. The pi (+) angles were chosen to emphasize and isolate contributions to the target analyzing powers from the two-body pi -nucleon interaction with it polarized nucleon whose polarization resulted from either the target polarization or front the distortion-induced effective polarization. The data are compared with factorized-amplitude distorted-wave impulse approximation (DWIA) calculations. The unpolarized cross sections are rather well described by these calculations. However, for all three angles the target analyzing powers are substantially reduced from predictions of conventional DWIA calculations. This result suggests a rather strong spin dependence in the Delta -nucleus spreading potential.

Results from a 4 pi solid angle measurement of the reaction pi(+) + He-4-->ppd at incident pion energies of T-pi+=70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the final states with energetic deuterons (ppd) and (pd)p. The differential cross sections are described by a complete set of five independent variables and various other kinematic variables and compared to cascade and phase space models where deuterons were formed by a semiclassical pickup model. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the (ppd) yield cannot be explained by these mechanisms. The remaining strength is reasonably well reproduced by 3N phase space models followed by pickup.

Results from a 4{pi} solid angle measurement of the reaction {pi}{sup +}+{sup 4}He{yields}ppd at incident pion energies of T{sub {pi}}{sup +}}=70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the final states with energetic deuterons (ppd) and (pd)p. The differential cross sections are described by a complete set of five independent variables and various other kinematic variables and compared to cascade and phase space models where deuterons were formed by a semiclassical pickup model. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the (ppd) yield cannot be explained by these mechanisms. The remaining strength is reasonably well reproduced by 3N phase space models followed by pickup. (c) 2000 The American Physical Society.

The absorption of π+ on Ar was studied at pion energies of 70, 118, 162, 239 and 330MeV, and on N and Xe at 239MeV. Twenty-six absorption reaction channels with at least two energetic charged particles in the final state have been evaluated. Partial cross-sections have been determined according to the number of protons, neutrons and deuterons in the final state.

Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on the toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.

This paper presents a large solid angle measurement of the positive pion absorption cross section on ^4He and its decomposition into partial channels.

This paper presents a large solid angle measurement of the positive pion absorption cross section on ^4He and its decomposition into partial channels.

This paper presents a large solid angle measurement of the positive pion absorption cross section on ^4He and its decomposition into partial channels. A large fraction of the absorption cross section at incident pion kinetic energies of T_π+ =70, 118, 162, 239, and 330 MeV is due to multinucleon channels.

K. Michaelian, 7 T. Petković, M. Planinić, R. P. Redwine, 4 D. Rowntree, 4 N. Šimičević, R. Trezeciak, 2 H. Ullrich, H. J. Weyer, 1,7 M. Wildi, 1 and K. E. Wilson ~LADS Collaboration! University of Basel, CH-4056 Basel, Switzerland University of Karlsruhe, D-76128 Karlsruhe, Germany Los Alamos Meson Physics Facility, Los Alamos, New Mexico 87545 Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 New Mexico State University, Las Cruces, New Mexico 88003 Old Dominion University, Norfolk, Virginia 23529 Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland University of Zagreb, HR-10000 Zagreb, Croatia ~Received 10 December 1998; published 30 June 1999 !

The absorption of positive pions on N and Ar has been studied for Tpi+= 118, 162, and 239 MeV. A precise determination has been made of the total absorption cross section for each energy and target nucleus. Comparisons are made with prior LADS results on H-2, He-3, and He-4. In addition, results are presented for the detected multiplicities of emitted protons, neutrons, and deuterons following pion absorption. [S0556-2813(99)06610-8].

Results from a 4 pi solid angle measurement of the inclusive reaction (pi(+), pi(0)) on H-2, He-3, and He-4 at incident pion energies of Tpi+ = 70, 118, 162, 239, and 330 MeV are presented. The single charge exchange total cross sections were determined, and are compared to previous results and simple models of pi-few-nucleon interactions. On the helium isotopes a strong damping of the cross sections in the Delta(1232) energy region is observed. Total cross sections of the breakup reaction pi(+) + H-2 --> pi(+) pn are also given. [S0556-2813(99)00708-6].

Results from a measurement of the reaction {sup 2}H({pi}{sup +},pp){pi}{degree} at T{sub {pi}{sup +}}=239thinspMeV are presented. Because two protons were detected, the measurement was sensitive to events which involved both nucleons in a substantial way. Differential distributions are compared to the predictions of simple models. An integrated cross section for SCX (single charge exchange), with the emission of two protons each with kinetic energy {gt}25thinspMeV, is presented. {copyright} {ital 1998} {ital The American Physical Society}

This paper presents a large solid angle measurement of the positive pion absorption cross section on He-4 and its decomposition into partial channels. The total absorption cross sections at incident pion kinetic energies of T-pi+=70, 118, 162, and 239 MeV are 35+/-5, 52+/-4, 51+/-5, and 27+/-2 mb, respectively. These values are lower than those reported in some previous experiments. At all pion energies a large fraction of the absorption cross section is due to multinucleon channels.

~LADS Collaboration! University of Basel, CH-4056 Basel, Switzerland University of Karlsruhe, D-76128 Karlsruhe, Germany LAMPF, Los Alamos, New Mexico 87545 University of Maryland, College Park, Maryland 20742 Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 New Mexico State University, Las Cruces, New Mexico 88003 Old Dominion University, Norfolk, Virginia 23529 Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland University of Zagreb, HR-10000 Zagreb, Croatia ~Received 9 June 1998 !

The pion absorption reaction (π+,3 p ) on Ar was studied at pion energies of 70, 118, 162 and 239 MeV, and on N and Xe at 239 MeV. The 3p cross section with a 50 MeV cut on the missing energy is presented. The existence of an initial state interaction (ISI) component to the reaction was investigated. The portion of the 3p cross section assigned to the ISI process is less than one half and at lower energies significantly so.

Results from a measurement of the reaction H-2(pi(+),pp)pi(o) at Tpi+ = 239 MeV are presented. Because two protons were detected, the measurement was sensitive to events which involved both nucleons in a substantial way. Differential distributions are compared to the predictions of simple models. An integrated cross section for SCX (single charge exchange), with the emission of two protons each with kinetic energy >25 MeV, is presented. [S0556-2813(98)06112-3].