The n-n S-wave scattering length from the neutron spectra of the reaction π− +d → 2n+γ

Pion-Nucleus Interactions

“…The analysis is actually simplifi ed because the final state contains one zero-mass photon and two equal-mass neutrons, and the photon energy is uniquely related to the nn relative momentum (50,51). Because of resolution difficulties, three early measurements of the pho ton spectrum (52-54) each yielded sizeable uncertainties in the extracted value of ann' The kinematically complete measurement of Haddock et al (55,56) led to an estimate of ann = -16.7 ± 1.3 fm , where the quoted uncertainty is essentially statistical. The innovative Lausanne experiment (57-59) used the radiative nucleon capture reaction with a monoenergetic line at 129.404 MeV to provide the required stable energy scale and response function of the spectrometer.…”

Radiative pion capture in H2 , He3 , and Golak1, Skibiński2, Topolnicki3 et al. 2018Phys. Rev. C

“…As early as in 1951 Watson and Stuart [13] showed with quite simple dynamics that the corresponding photon spectrum very strongly depends on the properties of the nn interaction. Since then many theoretical efforts [14][15][16][17][18][19][20][21] combined with more and more precise measurements [22][23][24][25][26][27][28][29][30][31][32] have contributed decisively to our present day knowledge about a nn . Detailed information about this rich field can be found in the review by Šlaus, Akaishi, and Tanaka [33] and in the more recent review by Gårdestig [34], where also complementary efforts [35,36] to determine a nn from the 2 H(n, np)n reaction were reported.…”

Radiative pion capture in 2H, 3He and 3H

“…As early as in 1951 Watson and Stuart [13] showed with quite simple dynamics that the corresponding photon spectrum very strongly depends on the properties of the nn interaction. Since then many theoretical efforts [14][15][16][17][18][19][20][21] combined with more and more precise measurements [22][23][24][25][26][27][28][29][30][31][32], have contributed decisively to our present day knowledge about a nn . Detailed information about this rich field can be found in the review by Šlaus, Akaishi, and Tanaka [33] and in the more recent review by Gårdestig [34], where also complementary efforts [35,36] to determine a nn from the 2 H(n, np)n reaction were reported.…”