University of California, Berkeley
Martin J. Savage
Institute for Nuclear Theory
Friends of the INT
Obtain an INT preprint number
INT Workshop INT-17-67W
Lattice QCD Input for Neutrinoless Double-β Decay
July 6 - 7, 2017
Our ability to constrain nonperturbative properties of multi-nucleon systems through the method
of Lattice Quantum Chromodynamics (LQCD) has increased by orders of magnitude compared with
the past, both in complexity and in precision, and suggest that more challenging problems in realm of
nuclear physics are not far from being amenable to the method of LQCD. While it is only recently that
LQCD has been applied to multi-nucleon systems, significant progress has already been made. Light
nuclei and hypernuclei have been shown to naturally emerge from the QCD degrees of freedom, and
some of their structure properties have been studied directly from QCD at unphysical quark masses.
Fast progress toward the physical point is anticipated in upcoming years with the deployment of Exascale
computing capabilities. Electroweak nuclear reactions from LQCD have recently become a reality
in light nuclei, an achievement that opens up the door to further LQCD studies of nuclear environments
when probed by external currents.
Studying the nuclear-physics contribution to the rate of the important neutrinoless double-β decay
process is a problem where LQCD physicists aim to make significant contributions to, in particular
by providing few-nucleon constraints for many-body methods. Extensive consideration has been given
to this problem in recent years and a few preliminary calculations are underway. Some exciting first
results in matching the QCD matrix elements to nucleonic matrix elements will appear in the upcoming
year, with challenges to be overcome, and a roadmap to be built to relate the LQCD matrix elements
in light nuclei to those relevant for planned experiments. This INT workshop, which is purposefully
embedded in a larger program on the topic with the involvement of nuclear effective field theorists and
nuclear many-body physicists, aims to introduce and specify the LQCD input to this program. Among
the questions to be addressed in this focused two-day meeting are:
What are the relevant matrix elements to be calculated with LQCD, within various new-physics
scenarios that incorporate the lepton-number violation? Are there common features in terms of
LQCD techniques and formalism for each of these matrix elements, in particular within short-range
and long-range scenarios?
Is there any value in a direct evaluation of the simplest (neutrinoless) double-β decay amplitude
that can be studied with LQCD, namely nn → ppee, beyond providing constraints on two-nucleon
effective field theory couplings to the external currents? What are the smallest nuclear
systems where independent LQCD and many-body calculations of the relevant matrix elements
will enable a diagnostic of many-body assumptions and limitations?
Are there other nuclear quantities that once constrained directly with LQCD, could help constraining
indirectly the matrix elements relevant to the (neutrinoless) double-β decay in realistic
nuclei? Are there alternative methods to the direct matrix element evaluation, such as the successfully
tested background field techniques, that by demanding less computational resources,
could expedite the matching program in the few-nucleon sector?
What formulation of the nuclear effective field theories is superior in providing the framework
to match QCD results to the nuclear matrix elements, given the energy scales involved in a
(neutrinoless) double-β decay in heavy nuclei, and given the limitations of the current nuclear
We encourage all the interested scientists in the LQCD, effective field theory and nuclear many-body
subfields to apply. This is a new program with fewer ideas and more challenges at present, and
new perspectives on this problem are extremely welcome.
There will be a $15 registration fee to attend the workshop. The registration fee includes participation in the workshop, lectures, and coffee breaks.