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Title: Proton-Proton Fusion and Tritium β Decay from Lattice Quantum Chromodynamics

The nuclear matrix element determining the $$pp\to d e^+ \nu$$ fusion cross section and the Gamow-Teller matrix element contributing to tritium $$\beta$$-decay are calculated with lattice Quantum Chromodynamics (QCD) for the first time. Using a new implementation of the background field method, these quantities are calculated at the SU(3)-flavor-symmetric value of the quark masses, corresponding to a pion mass of $$m_\pi$$ ~ 806 MeV. The Gamow-Teller matrix element in tritium is found to be 0.979(03)(10) at these quark masses, which is within $$2\sigma$$ of the experimental value. Assuming that the short-distance correlated two-nucleon contributions to the matrix element (meson-exchange currents) depend only mildly on the quark masses, as seen for the analogous magnetic interactions, the calculated $$pp\to d e^+ \nu$$ transition matrix element leads to a fusion cross section at the physical quark masses that is consistent with its currently accepted value. Moreover, the leading two-nucleon axial counterterm of pionless effective field theory is determined to be $$L_{1,A}=3.9(0.1)(1.0)(0.3)(0.9)\ {\rm fm}^3$$ at a renormalization scale set by the physical pion mass, also in agreement with the accepted phenomenological range. This work concretely demonstrates that weak transition amplitudes in few-nucleon systems can be studied directly from the fundamental quark and gluon degrees of freedom and opens the way for subsequent investigations of many important quantities in nuclear physics.
Authors:
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Publication Date:
Report Number(s):
JLAB-THY-16-2362; DOE/OR/23177-3961; arXiv:1610.04545
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1702835
Grant/Contract Number:
NSF PHY11-25915; PHY1206498; PHY15-15738; AC02-05CH11231; AC05-00OR22725; SC001347; SC00-10337; FG02-00ER41132; SC0010495; SC0011090; FG02-04ER41302; AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 119; Journal Issue: 6; 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
OSTI Identifier:
1393535
Alternate Identifier(s):
OSTI ID: 1374773