TY - JOUR

T1 - Excited-state effects in nucleon structure on the lattice using hybrid interpolators

AU - Green, Jeremy R.

AU - Engelhardt, Michael

AU - Hasan, Nesreen

AU - Krieg, Stefan

AU - Meinel, Stefan

AU - Negele, John W.

AU - Pochinsky, Andrew V.

AU - Syritsyn, Sergey N.

N1 - Publisher Copyright:
© 2019 authors. Published by the American Physical Society.

PY - 2019/10/24

Y1 - 2019/10/24

N2 - It would be very useful to find a way of reducing excited-state effects in lattice QCD calculations of nucleon structure that has a low computational cost. We explore the use of hybrid interpolators, which contain a nontrivial gluonic excitation, in a variational basis together with the standard interpolator with tuned smearing width. Using the clover discretization of the field strength tensor, a calculation using a fixed linear combination of standard and hybrid interpolators can be done using the same number of quark propagators as a standard calculation, making this a cost-effective option. We find that such an interpolator, optimized by solving a generalized eigenvalue problem, reduces excited-state contributions in two-point correlators. However, the effect in three-point correlators, which are needed for computing nucleon matrix elements, is mixed: for some matrix elements such as the tensor charge, excited-state effects are suppressed, whereas for others such as the axial charge, they are enhanced. The results illustrate that the variational method is not guaranteed to reduce the net contribution from excited states except in its asymptotic regime, and suggest that it may be important to use a large basis of interpolators capable of isolating all of the relevant low-lying states.

AB - It would be very useful to find a way of reducing excited-state effects in lattice QCD calculations of nucleon structure that has a low computational cost. We explore the use of hybrid interpolators, which contain a nontrivial gluonic excitation, in a variational basis together with the standard interpolator with tuned smearing width. Using the clover discretization of the field strength tensor, a calculation using a fixed linear combination of standard and hybrid interpolators can be done using the same number of quark propagators as a standard calculation, making this a cost-effective option. We find that such an interpolator, optimized by solving a generalized eigenvalue problem, reduces excited-state contributions in two-point correlators. However, the effect in three-point correlators, which are needed for computing nucleon matrix elements, is mixed: for some matrix elements such as the tensor charge, excited-state effects are suppressed, whereas for others such as the axial charge, they are enhanced. The results illustrate that the variational method is not guaranteed to reduce the net contribution from excited states except in its asymptotic regime, and suggest that it may be important to use a large basis of interpolators capable of isolating all of the relevant low-lying states.

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U2 - 10.1103/PhysRevD.100.074510

DO - 10.1103/PhysRevD.100.074510

M3 - Article

AN - SCOPUS:85074364018

VL - 100

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 7

M1 - 074510

ER -