arXiv subjects

Seonghee Kim

Publications and source records attributed to Seonghee Kim.

5 recordsLinked to original sources

arXiv2014

Calculation of BSM Kaon B-parameters using Staggered Quarks

We present updated results for kaon B-parameters for operators arising in models of new physics. We use HYP-smeared staggered quarks on the $N_f = 2+1$ MILC asqtad lattices. During the last year we have added new ensembles, which has necessitated chiral-continuum fitting with more elaborate fitting functions. We have also corrected an error in a two-loop anomalous dimension used to evolve results between different scales. Our results for the beyond-the-Standard-Model B-parameters have total errors of $5-10$\%. We find that the discrepancy observed last year between our results and those of the RBC/UKQCD and ETM collaborations for some of the B-parameters has been reduced from $4\!-\!5\,σ$ to $2\!-\!3\,σ$.

hep-lat↗

arXiv2013

Update on $B_K$ and $\varepsilon_K$ with staggered quarks

We update our results for $B_K$ obtained using HYP-smeared staggered valence quarks on the MILC asqtad lattices. In the last year, we have added 5 new measurments on the fine ($a\approx 0.09\;$fm) ensembles, and 2 new measurements on the superfine ($a\approx 0.06\;$fm) ensembles. These allow a simultaneous extrapolation in $a^2$ and sea quark masses, reducing the corresponding systematic error significantly. Our updated result is $\hat{B}_K = 0.738 \pm 0.005 (\text{stat}) \pm 0.034 (\text{sys})$.

hep-lat↗

arXiv2013

Beyond the Standard Model B-parameters with improved staggered fermions in $N_f=2+1$ QCD

We calculate the kaon mixing B-parameters for operators arising generically in theories of physics beyond the standard model. We use HYP-smeared improved staggered fermions on the $N_f = 2+1$ MILC asqtad lattices. Operator matching is done perturbatively at one-loop order. Chiral extrapolations are done using "golden combinations" in which one-loop chiral logarithms are absent. For the combined sea-quark mass and continuum extrapolation, we use three lattice spacings: $a \approx 0.045, 0.06$ and $0.09 \text{fm}$. Our results have a total error of 5-6%, which is dominated by the systematic error from matching and continuum extrapolation. For two of the BSM $B$-parameters, we agree with results obtained using domain-wall and twisted-mass dynamical fermions, but we disagree by $(4-5)σ$ for the other two.

hep-lat↗

arXiv2012

Recent progress in calculation of $B_K$ using staggered fermions

We report on recent progress in the calculation of $B_K$ using HYP-smeared improved staggered fermions on the MILC asqtad lattices. We have added measurements on fine ($a\sim 0.09 $fm) and superfine ($a\sim 0.06 $fm) ensembles at different values of the light sea quark mass ($a m_\ell$), as well as increased the statistics on some other ensembles. We find that the results on the fine lattices show a significantly stronger $am_\ell$ dependence than those on the superfine and coarse ($a\sim 0.12 $fm) lattices. We discuss different methods for accounting for these new results when doing the $a m_\ell$ and continuum extrapolations.

hep-lat↗

arXiv2012

Beyond the Standard Model corrections to $K^0-\bar{K}^0$ mixing

We calculate the B-parameters for operators arising in theories of new physics beyond the standard model (BSM) using HYP-smeared improved staggered fermions on the MILC asqtad lattices with N_f = 2+1 flavors. We use three different lattice spacings (a ~ 0.045, 0.06 and 0.09 fm) at a fixed ratio of light to strange quarks, m_l/m_s = 1/5, to obtain the continuum results. Operator matching is done using perturbative matching at one-loop order, and results are run to 2 or 3 GeV using two-loop running in the MS-bar scheme. For the chiral and continuum extrapolations, we use SU(2) staggered chiral perturbation theory. We present preliminary results with only statistical errors.

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