Unquenched determination of the kaon parameter B_K from improved staggered fermions

Abstract

The use of improved staggered actions (HYP, Asqtad) has been proved to reduce the scaling corrections that affected previous calculations of B_K with unimproved (standard) staggered fermions in the quenched approximation. This improved behaviour allows us to perform a reliable calculation of B_K including quark vacuum polarization effects, using the MILC configurations with n_f=2+1 flavours of sea fermions. We perform such a calculation for a single lattice spacing, a=0.125 fm, and with kaons made up of degenerate quarks with m_s/2. The valence strange quark mass m_s is fixed to its physical value and we use two different values of the light sea quark masses. After a chiral extrapolation of the results to the physical value of the sea quark masses, we find \hat B_K = 0.83+-0.18, where the error is dominated by the uncertainty in the lattice to continuum matching at O(α_s^2). The matching will need to be improved to get the precision needed to make full use of the experimental data on ε_K to constrain the unitarity triangle.

arXiv comment15 pages, 6 figures

References in corpus (40)

• Weak Decays Beyond Leading Logarithms
• CP Violation and the CKM Matrix: Assessing the Impact of the Asymmetric B Factories
• Flavor Symmetry and the Static Potential with Hypercubic Blocking
• The QCD spectrum with three quark flavors
• High-Precision Lattice QCD Confronts Experiment
• Light hadrons with improved staggered quarks: approaching the continuum limit
• Variants of fattening and flavor symmetry restoration
• The 2004 UTfit Collaboration Report on the Status of the Unitarity Triangle in the Standard Model
• Waiting for the Top Quark Mass, K^+ --> π^+ ν\barν, B_s^0-\bar{B}_s^0 Mixing and CP Asymmetries in B-Decays
• Flavor-Symmetry Restoration and Symanzik Improvement for Staggered Quarks
• Pion and Kaon masses in Staggered Chiral Perturbation Theory
• Lattice QCD on Small Computers
• The Upsilon spectrum and m_b from full lattice QCD
• Partial Flavor Symmetry Restoration for Chiral Staggered Fermions
• Staggered eigenvalue mimicry
• Accurate Determinations of ${\alpha }_s$ from Realistic Lattice QCD
• Scaling tests of the improved Kogut-Susskind quark action
• The Index Theorem and Universality Properties of the Low-lying Eigenvalues of Improved Staggered Quarks
• K0-anti-K0 mixing in the 1/Nc expansion
• Lattice QCD with two dynamical flavors of domain wall quarks
• Improving the Chiral Properties of Lattice Fermions
• Kaon B parameter from quenched Lattice QCD
• The $B_K$ Parameter in the $1/N_c$ Expansion
• Calculation of the K^0-\bar{K}^0 mixing parameter via the QCD sum rules at finite energies
• Perturbative Corrections for Staggered Four-Fermion Operators
• One-loop matching coefficients for improved staggered bilinears
• Chiral Perturbation Theory and Weak Matrix Elements
• Long-distance dimension-eight operators in B_K
• Perturbative matching of staggered four-fermion operators with hypercubic fat links
• Scheme Dependence of Weak Matrix Elements in the $1/N_c$ Expansion
• One-Loop Matching of the Heavy-Light A_0 and V_0 Currents with NRQCD Heavy and Improved Naive Light Quarks
• B_K in Staggered Chiral Perturbation Theory
• Systematics of Staggered Fermion Spectral Properties and Topology
• Perturbative renormalization factors for bilinear and four-quark operators for Kogut-Susskind fermions on the lattice
• $B_K$ and Explicit Chiral Symmetry Breaking
• Sea quark effects in B_K from N_f=2 clover-improved Wilson fermions
• Testing improved staggered fermions with $m_s$ and $B_K$
• Status of Lattice Flavor Physics
• One-loop matching of Delta S=2 four-quark operators with improved staggered fermions
• B_K from improved staggered quarks

Cited by in corpus (27)

• FLAG Review 2019
• Full nonperturbative QCD simulations with 2+1 flavors of improved staggered quarks
• Review of lattice results concerning low energy particle physics
• Flavor Physics in the Quark Sector
• Anatomy of New Physics in B-Bbar mixing
• Correlations among new CP violating effects in Delta F = 2 observables
• Lattice QCD inputs to the CKM unitarity triangle analysis
• B, D and K decays
• Possible evidence for the breakdown of the CKM-paradigm of CP-violation
• The B -> D* l nu form factor at zero recoil from three-flavor lattice QCD: A model independent determination of |V_cb|
• Neutral kaon mixing from 2+1 flavor Domain Wall QCD
• The neutral kaon mixing parameter B_K from unquenched mixed-action lattice QCD
• $B_K$ using HYP-smeared staggered fermions in $N_f=2+1$ unquenched QCD
• On the consistency between the observed amount of CP violation in the K- and Bd-systems within minimal flavor violation
• Natural SUSY and Kaon Mixing in view of recent results from Lattice QCD
• Kaon physics: a lattice perspective
• Unitarity Triangle Without Semileptonic Decays
• Phenomenological aspects of the exotic $T$ quark in 331 models
• Constraints on economical 331 models from mixing of K, Bd and Bs neutral mesons
• Flavour constraints on scenarios with two or three heavy squark generations
• The Kaon B-parameter in Mixed Action Chiral Perturbation Theory
• Progress in Kaon Physics on the Lattice
• Recent Progress in Lattice QCD
• Progress in kaon physics on the lattice
• K0-K0bar on the Lattice
• Quantum chromodynamics with advanced computing
• Lattice Kaon Physics