From a mass and amplitude determination (using matrixfit) the
pseudoscalar decay constant is determined for the case of Osterwalder Seiler
(OS) fermions from the AS and SS amplitude (in the twisted basis), ZA and
the OS pion mass.
computefpsOS(mfit, Kappa = sqrt(0.5), normalisation = "cmi",
boot.fit = TRUE, ZA = 1, ZAboot, dZA)An object of type matrixfit generated with
matrixfit. The correlation matrix (SS, SA, AS, AA) must have
been analysed, where the correlators are in the twisted basis.
The \(\kappa\)-value of the run, needed only if
normalisation="cmi".
normalisation of the correlators. If set to "cmi" the \(\kappa\) value must be specified.
If set to FALSE, the computation is not bootstrapped,
even if the matrixfit or gevp.amplitude contain bootstrap
samples. This is a useful time-saver if error information is not strictly
necessary. Of course, this affects the return values related to the
bootstrap, which are set to NA.
The value of the renormalisation constant \(Z_A\).
Bootstrap samples for \(Z_A\). If they are provided,
they are used for computing fps, if not, bootstrap samples are generated
from dZA. If both are missing, the error of \(Z_A\) is not
taken into account.
The value of the (normally distributed) error of the renormalisation constant \(Z_A\).
If mfit is available, this object will be returned but with
additional objects added: fpsOS, fpsOS.tsboot,
normalistaion, ZA, ZAboot and kappa if
applicable.
The pseudoscalar decay constant is computed from
$$f_\mathrm{PS}^\mathrm{OS} = Z_A \sqrt{2}\kappa\frac{\langle 0|
A|\pi\rangle}{m_\mathrm{PS}}$$ for
normalisation="cmi" or $$f_\mathrm{PS}^\mathrm{OS} = Z_A
\frac{\langle 0| A|\pi\rangle}{m_\mathrm{PS}}$$
expecting physical normalisation of the amplitudes.