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SUMMARY:Controlling Excited-State Contributions to Nucleon Isovector Charg
es using Distillation
DTSTART;VALUE=DATE-TIME:20180725T194000Z
DTEND;VALUE=DATE-TIME:20180725T200000Z
DTSTAMP;VALUE=DATE-TIME:20211015T203042Z
UID:indico-contribution-34950@indico.fnal.gov
DESCRIPTION:Speakers: Colin Egerer (William and Mary)\nAs all lattice calc
ulations are subject to a trade-off between excited-state contamination at
short Euclidean times and an increased signal-to-noise ratio at large Euc
lidean times\, the need for reduced or removed excited-state effects is pa
ramount. Perhaps the most notable in lattice calculations is that of the a
xial charge of the nucleon\, wherein calculations have historically differ
ed from the world average by roughly 10%. Widely used methods to tame the
impact of excited states on lattice n-point functions include the Jacobi a
nd Wuppertal smearing techniques\, and the variational method. An alternat
ive smearing algorithm called Distillation has garnered much attention in
spectroscopy calculations for its utility in efficiently identifying a ple
thora of hadronic states across a wide range of quantum numbers\, includin
g some of hybrid nature. Distillation provides several advantages includin
g explicit momentum projection at source and sink\, and the correlation of
arbitrarily complicated interpolators once a single set of modified quark
propagators have been computed. That said\, Distillation has as of yet se
en little use in structure calculations. In this presentation we discuss t
he implementation of Distillation in the calculation of the nucleon isovec
tor charges $g_A$\, $g_S$ and $g_T$. Rather than seek precise determinatio
ns of said charges\, we instead highlight the demonstrable improvements ac
hieved in calculated matrix elements by combining Distillation with the va
riational method. By employing a basis of several Distilled interpolators\
, including some of hybrid character\, we demonstrate an earlier onset of
a plateau region in calculated nucleon matrix elements and stability of sa
id plateaus under variations of the source/sink interpolator separation. W
hen compared to Jacobi smeared interpolators used in previous variational
analyses\, Distillation appears to afford greater statistical precision in
extracted matrix elements as reliable estimates are attainable at much sh
orter Euclidean times. Comparisons are also made to other recent strategie
s seeking to control excited-state effects\, and prospects are sketched fo
r the potential efficacy of Distillation in future structure calculations\
, such as the many works seeking to calculate parton distribution function
s.\n\nhttps://indico.fnal.gov/event/15949/contributions/34950/
LOCATION:Kellogg Hotel and Conference Center 105
URL:https://indico.fnal.gov/event/15949/contributions/34950/
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