Organizers:
Zohreh Davoudi
MIT
davoudi@mit.edu
William Detmold
MIT
wdetmold@mit.edu
Amy Nicholson
University of California, Berkeley
anicholson@berkeley.edu
Martin J. Savage
Institute for Nuclear Theory
mjs5@uw.edu
Program Coordinator:
Kimberlee Choe
jy24@uw.edu
(206) 6853509
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INT Workshop INT1767W
Lattice QCD Input for Neutrinoless Doubleβ Decay
July 6  7, 2017
Our ability to constrain nonperturbative properties of multinucleon 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 multinucleon 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 nuclearphysics contribution to the rate of the important neutrinoless doubleβ decay
process is a problem where LQCD physicists aim to make significant contributions to, in particular
by providing fewnucleon constraints for manybody 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 manybody physicists, aims to introduce and specify the LQCD input to this program. Among
the questions to be addressed in this focused twoday meeting are:

What are the relevant matrix elements to be calculated with LQCD, within various newphysics
scenarios that incorporate the leptonnumber violation? Are there common features in terms of
LQCD techniques and formalism for each of these matrix elements, in particular within shortrange
and longrange scenarios?
Is there any value in a direct evaluation of the simplest (neutrinoless) doubleβ decay amplitude
that can be studied with LQCD, namely nn → ppee, beyond providing constraints on twonucleon
effective field theory couplings to the external currents? What are the smallest nuclear
systems where independent LQCD and manybody calculations of the relevant matrix elements
will enable a diagnostic of manybody 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) doubleβ 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 fewnucleon 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) doubleβ decay in heavy nuclei, and given the limitations of the current nuclear
manybody techniques?
We encourage all the interested scientists in the LQCD, effective field theory and nuclear manybody
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.
