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Title: Ab initio calculation of the $$np \to d ³$$ radiative capture process

In this study, lattice QCD calculations of two-nucleon systems are used to isolate the short-distance two-body electromagnetic contributions to the radiative capture process $$np \to d\gamma$$, and the photo-disintegration processes $$\gamma^{(\ast)} d \to np$$. 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 $$m_\pi \sim 450$$ and 806 MeV, and are combined with pionless nuclear effective field theory to determine these low-energy inelastic processes. Extrapolating to the physical pion mass, a cross section of $$\sigma^{lqcd}(np\to d\gamma)=332.4({\tiny \begin{array}{l}+5.4 \\ - 4.7\end{array}})\ mb$$ is obtained at an incident neutron speed of $$v=2,200\ m/s$$, consistent with the experimental value of $$\sigma^{expt}(np \to d\gamma) = 334.2(0.5)\ mb$$.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [5]
  1. Univ. of Washington, Seattle, WA (United States)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  3. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  4. Univ. of Barcelona, Barcelona (Spain)
  5. The City College of New York, New York, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
OSTI Identifier:
1221536
Report Number(s):
JLAB-THY--15-2045; DOE/OR/23177--3346; arXiv:1505.02422
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
OCI-1053575; PHY1206498; PHY12-05778; AC02-05CH11231; DOE DE-SC0013477; SC0010337-ER42045; FG02-04ER41302; FG02-00ER41132; AC05-00OR22725; SC0010495; AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 115; Journal Issue: 13; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE
Contributing Orgs:
NPLQCD Collaboration
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS