Abstract
We perform a lattice computation of the flavour octet contribution to the average quark momentum in the nucleon, $$ {\left\langle x\right\rangle}_{\mu^2=4\kern0.5em {\mathrm{GeV}}^2}^{\left((8)\right.} $$ . In particular, we fully take the disconnected contributions into account in our analysis for which we use a generalization of the technique developed in [1]. We investigate systematic effects with particular emphasis on the excited states contamination. We find that in the renormalization free ratio $$ \frac{{\left\langle x\right\rangle}^{(3)}}{{\left\langle x\right\rangle}^{(8)}} $$ (with 〈x〉(3) the non-singlet moment) the excited state contributions cancel to a large extent making this ratio a promising candidate for a comparison to phenomenological analyses. Our final result for this ratio is in agreement with the phenomenological value and we find, including systematic errors, $$ \frac{{\left\langle x\right\rangle}^{(3)}}{{\left\langle x\right\rangle}^{(8)}}=0.39(1)(4) $$ .
Highlights
(with x (3) the non-singlet moment) the excited state contributions cancel to a large extent making this ratio a promising candidate for a comparison to phenomenological analyses
Our final result for this ratio is in agreement with the phenomenological value and we find, including systematic errors, x x
In this work we have performed a benchmark computation of the flavour octet combination of the first moment of parton distribution functions of the nucleon using Nf = 2 + 1 + 1 twisted mass fermions tuned to maximal twist
Summary
The lattice action used in our simulations includes as active degrees of freedom, besides the gluon field, a mass-degenerate light up and down quark doublet as well as a strange-charm quark pair in the sea, a situation which we refer to as the Nf = 2 + 1 + 1 setup. The quark mass parameters of the heavy flavour pair have been tuned so that in the unitary lattice setup the Kaon and D-meson masses, take approximately their experimental values. In order to fix the notation, we introduce the twisted mass lattice Dirac operator Df,tm for a doublet of mass degenerate quarks: Df,tm[U ] = DW[U ] + iaμf γ5τ 3. Employing the OS Dirac operator in the valence sector for the strange quark leads to a mixed action where the strange OS quark mass has been tuned to match within errors the unitary Kaon mass
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.