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Title: Kaon BSM B -parameters using improved staggered fermions from Nf=2+1 unquenched QCD

In this paper, we present results for the matrix elements of the additional ΔS = 2 operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM B -parameters. Combined with experimental results for ΔMK and εK, these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and Nf = 2 + 1 flavors of “asqtad” sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: a ≈ 0.09 , 0.06 and 0.045 fm. Valence light-quark masses range down to ≈ m$$phys\atop{s}$$ /13 while the light sea-quark masses range down to ≈ m$$phys\atop{s}$$ / 20 . Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, μ = 2 and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM B-parameters (B2 and B$$SUSY\atop{3}$$ ). The other two (B4 and B5) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.
  1. Seoul National Univ. (Korea, Republic of). Lattice Gauge Theory Research Center, FPRD, and CTP, Department of Physics and Astronomy. et al.
Publication Date:
Report Number(s):
Journal ID: ISSN 2470-0010; KB0301020
Grant/Contract Number:
SC00112704; AC02-98CH10886; FG02-96ER40956; SC0011637
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal Issue: 1; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
SWME Collaboration
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; fermions; lattice; SM; quarks; flavor; BSM
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1236402