Current Approved Experiments (all at IUCF)

E384 - Calibration of the LAMPF/NTOF Neutron Polarimeter at IUCF.

Spokespersons: T. Taddeucci (LANL), J. Rapaport (Ohio U.)

Abstract:

We propose a new technique for calibrating the analyzing power of an intermediate-energy neutron polarimeter over a broad energy range in a relatively short time. The old method involved measuring the 14C(p,n)14N(2.31 MeV) isobaric analog state reaction. The diagonal polarization tranfer coefficients for this state are unity so the outgoing neutrons have the same polarization as the proton beam and can be used for calibration. However, the cross-section for this reaction is rather small. We propose instead to use the fact that assuming parity conservation it is possible, at zero degerees, to show that:

where the "+" sign applies to unnatural-parity transitions, and the "-" sign to natural-parity transitions. Therefore, we can measure both longitudinal and transverse polarization transfer coefficients on a reaction with a large cross section to calibrate the polarimeter.
(approved IUCF PAC XXXVIII, June, 1994)


E385 - Polarization Transfer in Quasifree (p,n) reactions in Nuclei at 200 MeV.

Spokesperson: J. Rapaport (Ohio U.)

Abstract:

We propose to measure differential cross sections and spin transfer observables using the (p,n) reaction on 12C, 40Ca, and 208Pb in the quasielastic region of excitation with a proton beam energy of 200 MeV. The data will complement similar data obtained on these targets using the LAMPF NTOF facilities at 500 MeV. This experiment and the complementary experiment, E387, should provide a complete set of data to test present ideas on how to explain the lack of enhancement of the spin-longitudinal response as observed in the LAMPF data at 500 MeV.
(approved IUCF PAC XXXVIII, June, 1994)


E396 - Isovector Spin-longitudinal Response for Discrete States in 13N.

Spokespersons: E. Sugarbaker (OSU), X. Yang (IUCF)

Abstract:

We propose to measure differntial cross sections and spin transfer observables using the (p,n) reaction at a proton beam energy of 200 MeV to populate discrete states in 13N. The primary motivation of this study is to isolate the weak, but well-resolved 1/2- to 1/2+ transition and to measure the full set of spin transfer obervables. Determination of the spin-longitudinal cross section for this 1/2+ transition provides the means to study "pure" 0- transition strength, of great interest because it carries the pion quantum numbers and as such is sensitive to nuclear modifications to the pion field. It thereby provides a low-q extension fo our studies of the spin-longitudinal response function in quasifree scattering. This approach will circumvent the difficulties which have been encountered trying to measure a 0+ to 0- transition in the 16O(p,n)16F(0-) reaction at intermediate energies. Very precise data defining the spin-longitudinal and spin-tranverse responses for the mixed Fermi and GT 1/2- ground state and for the pure GT 3/2- state would also be obtained. We shall therefore also investigate the poorly understood q- dependence of the form factor for these latter transitions.
(approved IUCF PAC XXXVIII, June, 1994)


E387 - Spin Transfer Measurements of the Quasielastic Region on 2H, 3He and 4He with the (p,n) reaction at 200 MeV.

Spokespersons: M. Palarczyk (Ohio U.), D. Prout (KSU), B. Anderson (KSU)

Abtract:

We propose to investigate the differential cross section and spin trasfer observables using the (p,n) probe on 2H, 3He, and 4He in the quasielastic region and for the final-state interaction region on 2H at an incident energy of 200 MeV. These measurements will allow a decomposition of the data into spin-longitudinal and spin-transverse parts. Recent results from LAMPF have shown that there is no enhancement of the longitudinal response with respect to the transverse response at 500 MeV. This has led to much theoretical interest in these results. The proposed measurements will provide data over a wide range of excitation energy on light nuclei that can be used to test recent theoretical models. This proposal and the parallel proposal for E385 will provide a wide data base including light, medium, and heavy nuclei at 200 MeV. It will complement the data already taken at LAMPF at 500 and 800 MeV and place constraints on models of the spin response in this region. The measurements of the final-state interaction region in the 2H(p,n)2p reaction will provide sensitive tests of impulse approximation and exact 3-body Fadeev calculations. Possible sensitivity to the deuteron d-state contributions will be explored.
(approved IUCF PAC XXXVIII, June, 1994)


E390 (continuation) - Gamow-Teller Strength Functions: Absolute Normalizations.

Spokespersons: C. Goodman (IUCF), M. Palarczyk (Ohio U.)

Abstract:

We ask for time to continue Gamow-Teller strength function measurements previously proposed and approved. We have used part of our approved time to study the energy resolution for 127I and have demonstrated that we can achieve the required energy resolution to carry out the 127I experiment. In this proposal we want to focus on those targets in the original proposal which do not require high energy resolution. These cases are individually interesting for several reasons, but also bear on the general question of the reliabilty of GT strengths extracted from (p,n) measurements. This, of course, is crucial for the 127I experiment. These targets are 40Ar, 26Mg, 59Co, and 208Pb.
(approved IUCF PAC XXXIX, Dec. 1994)


E396 - Gamow-Teller Strength Function for 127-Iodine.

Spokespersons: C. Goodman (IUCF), M. Palarczyk (Ohio U.)

Abstract:

We propose to measure the 127I(p,n) reaction to extract the cross section for the 3/2+ 0.125 keV state in 127Xe and to measure the full GT strength function for this reaction. The information is crucial to proper interpretation of the 7Be solar neutrino absorption in the IODINE detector at the Homestake gold mine, SD, which will go into operation in the early sping of 1996.
(approved IUCF PAC XXXX, Dec., 1995)


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Last modified 3/27/96.