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

Abstract

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 ΔM_K and ε_K, these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and N_f = 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.

Authors:

Choi, Benjamin J. ^[1]

---

+ Show Author Affiliations

1. Seoul National Univ. (Korea, Republic of). Lattice Gauge Theory Research Center, FPRD, and CTP, Department of Physics and Astronomy. et al.

Publication Date:

Thu Jan 28 00:00:00 EST 2016

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Nuclear Physics (NP)

Contributing Org.:

SWME Collaboration

OSTI Identifier:

1340364

Alternate Identifier(s):

OSTI ID: 1236402

Report Number(s):

BNL-112252-2016-JA
Journal ID: ISSN 2470-0010; KB0301020

Grant/Contract Number:  

SC00112704; AC02-98CH10886; FG02-96ER40956; SC0011637

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review D

Additional Journal Information:

Journal Volume: 93; Journal Issue: 1; Journal ID: ISSN 2470-0010

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; fermions; lattice; SM; quarks; flavor; BSM