Leading E1 and M1 contributions to radiative neutron capture on lithium-7

Abstract

Abstract. Using halo effective field theory, we provide a model-independent calculation of the radiative neutron capture on lithium-7 over an energy range where the contribution from the 3 + resonance becomes important. We also present power counting arguments that establish a hierarchy for electromagnetic oneand two-body currents. One finds that a satisfactory description of the capture reaction, in the present single-particle approximation, requires a resonance width about three times larger than the experimentally quoted value.

Combiningab initiocalculations and low-energy effective field theory for halo nuclear systems: The case of7Li+n→8Li+γ

“…The degrees of freedom in our calculation are the neutron together with the ground and first-excited states of the 7 Li core. Halo-EFT has previously been applied to this system [11,12], but, in contrast to those works we use ANCs from ab initio calculations to fix most EFT parameters.…”

“…The 3 + resonance could be added as an additional dynamical degree of freedom in the EFT, as was done in Ref. [12].…”

“…The radiative capture of neutrons on 7 Li [denoted 7 Li(n, γ) 8 Li] has been studied both experimentally [1][2][3][4][5][6][7] and theoretically [8][9][10][11][12][13][14][15][16] for many years. The reaction could be important for the r-process in neutrino-driven winds, as part of a path around the A = 5 and A = 8 stability gaps [17], although most contemporary interest focuses on the use of 7 Li(n, γ) 8 Li to constrain models of the isospin mirror process 7 Be(p, γ) 8 B 1 .…”

The 7Li (n,γ)8Li radiative capture at astrophysical energies

“…Similar results were achieved in more recent works [37,38], where a correct description of the total capture cross sections based on the E1 process for nonresonance energies. As far as we know, based on model independent methods, results with an acceptable description of the resonance at 0.25 MeV were only obtained recently [39].…”

Few-Body Universality in Halo Nuclei

“…Halo EFT has recently been applied to describe the structure and reactions of many known and predicted one-and two-neutron halo systems. For oneneutron halos it essentially reproduces the effective range expansion, but their electromagnetic structure and reactions can be predicted [15][16][17][18][19][20]. Moreover, the natural accuracy limits of cluster models can be estimated from the order at which local gauge invariant couplings to the currents appear.…”