Neutral Kaon mixing beyond the Standard Model

Hudspith, Renwick J.; Garrón, Nicolas; Lytle, Andrew

doi:10.22323/1.251.0327

Cited by 8 publications

(13 citation statements)

References 21 publications

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“…In [1,21], we added another lattice spacing and investigated the origin of the discrepancy. In particular for the non-perturbative renormalisation procedure, in addition to the traditional RI-MOM scheme, we have implemented new intermediate renormalisation schemes, called (γ µ , γ µ ) and (/ q, / q) which satisfy the RI-SMOM condition, and therefore exhibit non-exceptional kinematics.…”

Section: Jhep10(2017)054mentioning

confidence: 99%

Neutral kaon mixing beyond the Standard Model with n f = 2 + 1 chiral fermions. Part 2: non perturbative renormalisation of the ΔF = 2 four-quark operators

Boyle

Garrón

Hudspith

et al. 2017

J. High Energ. Phys.

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We compute the renormalisation factors (Z-matrices) of the ∆F = 2 fourquark operators needed for Beyond the Standard Model (BSM) kaon mixing. We work with n f = 2+1 flavours of Domain-Wall fermions whose chiral-flavour properties are essential to maintain a continuum-like mixing pattern. We introduce new RI-SMOM renormalisation schemes, which we argue are better behaved compared to the commonly-used corresponding RI-MOM one. We find that, once converted to MS, the Z-factors computed through these RI-SMOM schemes are in good agreement but differ significantly from the ones computed through the RI-MOM scheme. The RI-SMOM Z-factors presented here have been used to compute the BSM neutral kaon mixing matrix elements in the companion paper [1]. We argue that the renormalisation procedure is responsible for the discrepancies observed by different collaborations, we will investigate and elucidate the origin of these differences throughout this work.

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Section: Jhep10(2017)054mentioning

confidence: 99%

Neutral kaon mixing beyond the Standard Model with n f = 2 + 1 chiral fermions. Part 2: non perturbative renormalisation of the ΔF = 2 four-quark operators

Boyle

Garrón

Hudspith

et al. 2017

J. High Energ. Phys.

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“…A further motivation for this work is provided by the recent results from the ETM and RBC-UKQCD collaborations, presented in Refs. [3] and at Lattice 2015 [25,26], respectively. The former work (which extends the N f = 2 simulations of Ref.…”

Section: Introductionmentioning

confidence: 99%

Kaon BSMB-parameters using improved staggered fermions fromNf=2+1unquenched QCD

et al. 2016

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We present results for the matrix elements of the additional ∆S = 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 ∆MK and K , these constrain the parameters of BSM models. We use improved staggered fermions, with valence 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 s /13 while the light sea-quark masses range down to ≈ m phys 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 GeV 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 3). The other two (B4 and B5) differ significantly from those obtained using RI-MOM renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD collaboration using RI-SMOM intermediate schemes.

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“…Recent calculations obtained partly consistent results [37,[39][40][41], while a 30-40% tension between calculations of B 4 and B 5 remains (as it was already the case nearly a decade ago [42,43]). For definiteness, we use here the values obtained in ref.…”

Section: Constraints On New Physicsmentioning

confidence: 69%

A new look at the theory uncertainty of ϵ K

Ligeti

Sala

2016

J. High Energ. Phys.

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Abstract:The observable K is sensitive to flavor violation at some of the highest scales. While its experimental uncertainty is at the half percent level, the theoretical one is in the ballpark of 15%. We explore the nontrivial dependence of the theory prediction and uncertainty on various conventions, like the phase of the kaon fields. In particular, we show how such a rephasing allows to make the short-distance contribution of the box diagram with two charm quarks, η cc , purely real. Our results allow to slightly reduce the total theoretical uncertainty of K , while increasing the relative impact of the imaginary part of the long distance contribution, underlining the need to compute it reliably. We also give updated bounds on the new physics operators that contribute to K .

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Neutral Kaon mixing beyond the Standard Model

Abstract: We compute the hadronic matrix elements of the four-quark operators needed for the study of

Cited by 8 publications

References 21 publications

Neutral kaon mixing beyond the Standard Model with n f = 2 + 1 chiral fermions. Part 2: non perturbative renormalisation of the ΔF = 2 four-quark operators

Neutral kaon mixing beyond the Standard Model with n f = 2 + 1 chiral fermions. Part 2: non perturbative renormalisation of the ΔF = 2 four-quark operators

Kaon BSMB-parameters using improved staggered fermions fromNf=2+1unquenched QCD

A new look at the theory uncertainty of ϵ K

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