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Stronach, C. E.; Lieb, B. J.; Funsten, H.O.; Kossler, W. J.; Plendl, H.S.; Lind, V. G.

doi:10.1103/physrevc.23.2150

Cited by 7 publications

(3 citation statements)

References 22 publications

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“…7 ) In heavy nuclei it has been assumed that the TT' A + ratios for energetic protons from the (TT, 2N) mechanism would approach ~ -n-7 It seems that a more appropriate value for heavy nuclei is -i^; in other words most of the energetic protons produced by TT" cannot be assumed to originate from a simple TT +2N •+2N process. Our result is consistent with the recent observation that the ( TT , 2AT) reaction on 12 C and 32 S does not excite J=0 + , T = 1 states in 10 B or 30 P. 8 We would like to thank Dr. R. R. Whitney and Dr. J. Kallne for their help in connection with the use of the cryogenic target, and Dr. J. Lichtenstadt for carrying out the neutron efficiency calculations. This work was supported in part by the U. S. Department of Energy under Contract No.…”

Section: The Ratios R =Da{tt~ Pn)/do(it* Pp) Insupporting

confidence: 91%

Isospin Dependence of Pion Absorption on a Pair of Nucleons

et al. 1981

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The relative cross sections for the 2N + TT-2iV reactions were determined where the initial two nucleons are in a relative s state, and coupled either to isospin zero or to one. This information is extracted from two-nucleon coincidence measurements of the (7r + , 2p) and the (7r" f pn) reactions on targets of 3 He and 4 He.PACS numbers: 25.80.+f Pion absorption is usually treated as proceeding through the n +2iV-2iV process. Considerable effort 1 has been devoted to understanding the TT + +d -* pp reaction, in which absorption takes place on a T = 0, S =1 nucleon pair. At bombarding energies in the (3,3) resonance region this reaction is believed to be dominated by the intermediate AN configuration with (J 7r ) AAr =2 + and AAT orbital angular momentum 1,^=0. Much less consideration has been given to the analogous process in which the pion is absorbed by two nucleons in a T =1, S =0 state. Such nucleon pairs are present in all nuclei heavier than the deuteron, and understanding absorption on such pairs is important to the understanding of nuclear pion absorption in general. The inverse of this process certainly does play a role in pion production {N A +N B -N c +N D +TT) and is part of the cross sections designated as a ±1 and a 01 in the traditional parametrization. 2 In pion production, however, several partial waves may contribute, and there is no simple way to select the piece of the cross section in which the (N C N D ) pair is restricted to J ,r = 0 + , T =1.If one assumes A dominance in the absorption process then it follows that the reaction TT + 2N -2N can only go through a T = 1 final state. If only isospin is considered, absorption on an initially T =0 nucleon pair is twice as likely as that on an initially T =1 pair. 3 It should be noted, however, that absorption on an initial J 7r = 0 + , T = 1 pair involves intermediate states that are different from the T = 0 case, as may be seen in Table I. In particular, L^^O, which dominates absorption on a deuteron, is not allowed in the T =1 case. Thus more detailed dynamical con-siderations may very well enter in this ratio.In the present work we report on coincidence measurements of the ir + 2N -* 2N process with targets of 4 He and 3 He. We assume 4 He and 3 He to have simple wave functions with all particles in relative s states, so that a comparison of the (TT + 9 2p) and the (n~ ,pn) reactions will be simply related to the isospin cross sections; the former must start with an initial pair of (np) nucleons that could be in either aT=loraT=0 state, while the latter must start with the initial pair of T =1 protons.The experiment was performed with 165-MeV pion beams from the P 3 channel of the Los Alamos Meson Physics Facility. Cryogenic liquid targets were used, with thicknesses of 343 and 629 mg/ cm 2 for 3 He and 4 He, respectively. 4 Protons were detected with a magnetic spectrometer, 5 with a momentum acceptance Ap/p =± 25% and solid angle of 8 msr. Coincident protons and neutrons were TABLE I. Quantum numbers permitted in the A model for n + (2N) {~*...

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Section: The Ratios R =Da{tt~ Pn)/do(it* Pp) Insupporting

confidence: 91%

Isospin Dependence of Pion Absorption on a Pair of Nucleons

et al. 1981

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“…The study of pion absorption on a p-n pair in a T = I state is more complicated because it is hard to determine the isospin of the absorbing pair. Somewhat indirectly, prompt gamma-ray measurements (134) indi cate that T = -1 final states are very weak. A study of the 6 Li(n +, 2p)4He reaction at 31 MeV appears to indicate a signifi cant transition to T = 1 final states, although these states are broad and overlap with T = 0 states (135).…”

Section: Coincidence Quasi�deuteron Studiesmentioning

confidence: 99%

“…For some examples one may look at (149) fo r a survey in s-d shell nuclei, ( 150) and ( 151) fo r studies in the Ni region, (152) fo r a comparison of data on stopped and fa st pions, and (1 34) fo r measurements on lighter targets. For some recent measurements with stopped pions, see fo r instance (134,151,153). The techniques make use of the characteristic prompt gamma rays and radioactivities as signatures of the nuclei that were left behind after the initial phases of fa st nucleon emission fo llowed by the evaporation of neutrons and alpha particles.…”

Section: Studies Of Residual Nucleimentioning

confidence: 99%