The Parity Partner of the Nucleon in Quenched QCD With Domain Wall Fermions Page: 2 of 3
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.
2
1.6
preliminary
1.5
) N* (exp.)
1.4 - N (exp.)
1.3
1.2
1.1 -
1.0 x
0.9 -
0.8
0.7
. -x B1+ (nucleon)
0.6 - B1-
0.5 -' B2
I I I I I I0.00 0.02 0.04 0.06
1.8
1.6
1.4
1.2
1.0
0.0.08 0.10 0.12 0.14
m: quark mass
0.2 0.4 0.6
MPs / MyFigure 1. N (x) and N* (0 and O) masses versus
the quark mass. The corresponding experimental
values for N and N* are marked with stars. The
N-N* mass splitting is clearly observed.
negative-parity contributions [9]. This means
that there is contamination from the oppo-
site parity state propagating backwards in time.
Thus, to extract parity-eigenstate signals we use
a linear combination of quark propagators, one
obtained with periodic and another with anti-
periodic boundary conditions in the time direc-
tion.
We use seven values for the valence quark mass
m in the range of 0.02 < m < 0.125, corre-
sponding to the Grp meson mass ratios mr/mP ~
0.59 - 0.90. Quark propagators are calculated
with wall source and point sink, and two different
source positions are used for each gauge configu-
ration.
Definite plateaus are seen in the effective mass
plots for Bi, Bi and B2 operators. In Fig-
ure 1, we present our estimates of the nucleon
(N) and its parity partner (N*) mass values ob-
tained by taking a weighted average of the ef-
fective mass in appropriate time ranges. The
nucleon mass is extracted from the Bt opera-
tor. N* mass estimates from Bi and B2 opera-Figure 2. Mass ratio of the negative-parity
excited-state and positive-parity ground-state
baryons versus mass ratio of the pseudoscalar me-
son and vector meson.
tors agree within errors in the whole quark mass
range, as expected from their common quantum
numbers. An important feature is that the N-N*
mass splitting is observed in the whole range and
even for light valence quark mass values. Another
is that the splitting grows as the valence quark
mass decreases, suggesting that the large split-
ting observed in nature indeed comes from the
spontaneous breaking of chiral symmetry. Lin-
ear extrapolation in valence quark mass gives us
mN=0.56(2) and mN. =0.77(2) in lattice units for
values in the chiral limit which are consistent with
the experimental value (a-1 ~ 1.9 GeV from the
p-meson mass [6]). In Figure 2, we compare two
mass ratios, one from the baryon parity partners
MN. /mN and the other from pseudo-scalar and
vector mesons m,/mP. Experimental points are
marked with stars, corresponding to non-strange
(left) and strange (right) sectors. In the strange
sector we use E and E(1750) as baryon parity
partners and K and K* for mesons [1]. We find
the baryon mass ratio grows with decreasing me-
son mass ratio, toward reproducing the experi-0
apreliminary
- Bi-
o Bp
* experimental0.8 1.0
0
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Sasaki, S. The Parity Partner of the Nucleon in Quenched QCD With Domain Wall Fermions, article, July 12, 2000; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc719787/m1/2/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.