SU(2) and SU(3) chiral perturbation theory analysis of meson and baryon masses in 2+1 flavor lattice QCD. Lattice 2008 @ College of William and Mary Center for Computational Sciences, University of Tsukuba
Lattice 2008 @ College of William and Mary
Center for Computational Sciences,
University of Tsukuba
Daisuke Kadoh for PACS-CS collaboration
Recent PACS-CS result : arXiv:0807.1661v1 [hep-lat]
- Determination of physical points with ChPT fit
- Examination of signals for chiral logarithms expected from ChPT
- O(a)-improved Wilson quark and Iwasaki gauge action
- Lattice size
More details were given in talks by
Naoya Ukita (Mon, 6:20-), Ken-Ichi Ishikawa (Wed, 11:20- )
Wilson chiral perturbation theory
pseudoscalar meson mass and decay constants in terms of AWI quark mass
・ “ WChPT(NLO, AWI quark mass)is equivalent to continuum ChPT(NLO) ”
and can be absorbed into redefinitions of and .
Therefore, hereafter we concentrate on the continuum ChPT
up to NLO.
for our lightest point
From NLO ChPT,
Contribution of FSE is 4% for
1-2% for , almost 0% for
at physical point.
PACS-CS (●○ )
CP-PACS/JLQCD (● )
- CP-PACS/JLQCD data and PACS-CS ones are connected smoothly.
- Typical behavior of chiral logarithm appears.
- fit range
4 data points
- simultaneous fit to .
(1) Low energy constants
6 unknown parameters for
in SU(3) ChPT up to NLO.
All and are compatible.
On the other hand, and show discrepancies.
Phenomenological values for LECs are taken from
G. Amoros, J. Bijnens and P. Talavera, Nucl. Phys. B 602, 87 (2001)
Large discrepancies are observed between data and fit result
around . This causes a large value of .
NLO contributions are almost 10% for .
However, they are significant for decay constants,
10-40% for and 40-50% for in our fit range.
SU(3) ChPT(NLO) fit gives reasonable values for the low energy constants.
But, we do not determine the physical point from the fit,
a rather large value of
bad convergence for and .
Alternative choices for chiral analysis
(1) SU(3) ChPT up to NNLO
(2) SU(2) ChPT up to NLO with analytic expansion
of strange quark mass around the physical point
“It is difficult to determine all LECs at NNLO without increasing data points.
On the other hand, our strange quark mass is close enough to the physical
value. Therefore, we employ SU(2) ChPT analysis ”
- simultaneous fit to .
( is independently fitted.)
8 unknown parameters for
in SU(2) ChPT with ms-linear expansion.
Fit results are in good agreement with data points.
This corresponds reasonable values of . .
Convergence of SU(2) ChPT becomes better than one of SU(3) ChPT.
- Pseudoscalar meson decay constants
(*) We use perturbative renormalization factors, ZA and ZP
to calculate renormalized quark mass and pseudoscalar decay constants
Non-perturbative renormalization factors are now calculating.
Talk by Yusuke Taniguchi (Fri, 5:40-)
Nucleon mass up to
We set some LECs to physical values,
and two possibilities for
We choose two data region,
range-I : 4 points
range-II : 5 points
- Convergence of SU(2) BChPT for Nucleon
LO and NLO terms cancel each other.
The convergence is not obvious in large pion mass region.
More drastic cancellation are needed for SU(3) BChPT and NNLO would be so large due to strange quark mass.
Probably, for 2+1 flavor QCD, it is difficult to obtain the hadron spectrum by
performing chiral extrapolation based on vector meson ChPT and baryon ChPT
with good convergences. Simulation at physical point