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SUMMARY:Estimating excited-state contamination in nucleon correlators usin
g experimental data
DTSTART;VALUE=DATE-TIME:20160729T132000Z
DTEND;VALUE=DATE-TIME:20160729T134000Z
DTSTAMP;VALUE=DATE-TIME:20191212T120858Z
UID:indico-contribution-2583@conference.ippp.dur.ac.uk
DESCRIPTION:Speakers: Maxwell Hansen (University of Mainz)\nExcited-state
contamination is one of the dominant uncertainties in lattice calculations
of nucleon charges and form factors. To estimate this uncertainty one nee
ds the finite-volume energy spectrum as well as the finite-volume matrix e
lements that determine the coefficients of excited state exponentials. In
this work we use experimental data\, supplemented by chiral perturbation t
heory (ChPT)\, to estimate these quantities. We first use the Lüscher qua
ntization condition\, extended to spin-half particles\, to calculate finit
e-volume $N \\pi$ states from $N \\pi$ scattering phase shifts. We then st
udy the excited state coefficients using an extension of the Lellouch-Lüs
cher formalism. This gives a relation between finite- and infinite-volume
matrix elements. Both matrix elements of the axial current and the nucleon
interpolating fields arise. While the former can be constrained experimen
tally\, the latter are generally unknown and depend on the details of the
lattice calculation. We examine various scenarios and find that excited-st
ate contamination can be larger than previous ChPT studies suggest.\n\nhtt
ps://conference.ippp.dur.ac.uk/event/470/contributions/2583/
LOCATION:Highfield Campus\, University of Southampton Building B2a Room 20
77
URL:https://conference.ippp.dur.ac.uk/event/470/contributions/2583/
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