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Title: Ab initio Calculation of the np→dγ Radiative Capture Process
Author: Beane, Silas R.
Chang, Emmanuel
Detmold, William
Orginos, Kostas
Parreño García, Assumpta
Savage, Martin J.
Tiburzi, Brian C.
NPLQCD Collaboration
Keywords: Física de partícules
Particle physics
Issue Date: 24-Sep-2015
Publisher: American Physical Society
Abstract: Lattice QCD calculations of two-nucleon systems are used to isolate the short-distance two-body electromagnetic contributions to the radiative capture process n p → d γ , and the photo-disintegration processes γ ( * ) d → n p . In nuclear potential models, such contributions are described by phenomenological meson-exchange currents, while in the present work, they are determined directly from the quark and gluon interactions of QCD. Calculations of neutron-proton energy levels in multiple background magnetic fields are performed at two values of the quark masses, corresponding to pion masses of m π ∼ 450 and 806 MeV, and are combined with pionless nuclear effective field theory to determine the amplitudes for these low-energy inelastic processes. At m π ∼ 806     MeV , using only lattice QCD inputs, a cross section σ 806     MeV ∼ 17     mb is found at an incident neutron speed of v = 2 , 200     m / s . Extrapolating the short-distance contribution to the physical pion mass and combining the result with phenomenological scattering information and one-body couplings, a cross section of σ lqcd ( n p → d γ ) = 334.9 ( + 5.2 − 5.4 )     mb is obtained at the same incident neutron speed, consistent with the experimental value of σ expt ( n p → d γ ) = 334.2 ( 0.5 )     mb .
Note: Reproducció del document publicat a:
It is part of: Physical Review Letters, 2015, vol. 115, num. 13, p. 132001
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ISSN: 0031-9007
Appears in Collections:Articles publicats en revistes (Física Quàntica i Astrofísica)
Articles publicats en revistes (Institut de Ciències del Cosmos (ICCUB))

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