Proton-Proton Fusion and Tritium β Decay from Lattice Quantum Chromodynamics.

Autor:	Savage MJ; Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550, USA.; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA., Shanahan PE; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA., Tiburzi BC; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Department of Physics, The City College of New York, New York, New York 10031, USA.; Graduate School and University Center, The City University of New York, New York, New York 10016, USA.; RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973, USA., Wagman ML; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195, USA., Winter F; Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA., Beane SR; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195, USA., Chang E; Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550, USA., Davoudi Z; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA., Detmold W; Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA.; Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA., Orginos K; Jefferson Laboratory, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA.; Department of Physics, College of William and Mary, Williamsburg, Virginia 23187-8795, USA.
Jazyk:	angličtina
Zdroj:	Physical review letters [Phys Rev Lett] 2017 Aug 11; Vol. 119 (6), pp. 062002. Date of Electronic Publication: 2017 Aug 10.
DOI:	10.1103/PhysRevLett.119.062002
Abstrakt:	The nuclear matrix element determining the pp→de^{+}ν fusion cross section and the Gamow-Teller matrix element contributing to tritium β decay are calculated with lattice quantum chromodynamics 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_{π}∼806  MeV. The Gamow-Teller matrix element in tritium is found to be 0.979(03)(10) at these quark masses, which is within 2σ 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→de^{+}ν 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(0.2)(1.0)(0.4)(0.9)  fm^{3} at a renormalization scale set by the physical pion mass, also agreeing within 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.
Databáze:	MEDLINE
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