R. Arthur
University of Edinburgh
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Featured researches published by R. Arthur.
Physical Review D | 2011
Yasumichi Aoki; R. Arthur; Thomas Blum; Peter A. Boyle; Dirk Brömmel; Norman H. Christ; C. Dawson; Jonathan M. Flynn; Taku Izubuchi; X-Y. Jin; Chulwoo Jung; C. Kelly; M. Li; A. Lichtl; M. Lightman; Meifeng Lin; Robert D. Mawhinney; C.M. Maynard; Shigemi Ohta; Brian Pendleton; Christopher T. Sachrajda; E. E. Scholz; Amarjit Soni; J. Wennekers; James Zanotti; R. Zhou
We present physical results obtained from simulations usin g 2+1 flavors of domain wall quarks and the Iwasaki gauge action at two values of the lattice spac ing a, (a−1= 1.73 (3) GeV and a−1= 2.28 (3) GeV). On the coarser lattice, with 24 3×64×16 points (where the 16 corresponds to Ls, the extent of the 5 th dimension inherent in the domain wall fermion (DWF) formula tion
Physical Review D | 2010
Yasumichi Aoki; Amarjit Soni; M. Lightman; R. Arthur; C. Sturm; Chulwoo Jung; R.D. Kenway; Taku Izubuchi; E. E. Scholz; Shigemi Ohta; Robert D. Mawhinney; Thomas Blum; D. Brömmel; C. Dawson; Norman H. Christ; C. Kelly; C.T. Sachrajda; J. Wennekers; R. Zhou; Peter A. Boyle
We determine the neutral kaon mixing matrix element BK in the continuum limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action at two different lattice spacings. These lattice fermions have near exact chiral symmetry and therefore avoid artificial lattice operator mixing. We introduce a significant improvement to the conventional nonperturbative renormalization (NPR) method in which the bare matrix elements are renormalized nonperturbatively in the regularization invariant momentum scheme (RI-MOM) and are then converted into the MS? scheme using continuum perturbation theory. In addition to RI-MOM, we introduce and implement four nonexceptional intermediate momentum schemes that suppress infrared nonperturbative uncertainties in the renormalization procedure. We compute the conversion factors relating the matrix elements in this family of regularization invariant symmetric momentum schemes (RI-SMOM) and MS? at one-loop order. Comparison of the results obtained using these different intermediate schemes allows for a more reliable estimate of the unknown higher-order contributions and hence for a correspondingly more robust estimate of the systematic error. We also apply a recently proposed approach in which twisted boundary conditions are used to control the Symanzik expansion for off-shell vertex functions leading to a better control of the renormalization in the continuum limit. We control chiral extrapolation errors by considering both the next-to-leading order SU(2) chiral effective theory, and an analytic mass expansion. We obtain BKMS? (3??GeV)=0.529(5)stat(15)?(2)FV(11)NPR. This corresponds to B?KRGI? =0.749(7)stat(21)?(3)FV(15)NPR. Adding all sources of error in quadrature, we obtain B?KRGI? =0.749(27)combined, with an overall combined error of 3.6%.
Physical Review D | 2011
R. Arthur; Peter A. Boyle; Dirk Brömmel; Donnellan; Jonathan M. Flynn; A. Juettner; Thomas Rae; C.T. Sachrajda
As part of the UKQCD and RBC collaborations’ Nf=2+1 domain-wall fermion phenomenology programme, we calculate the first two moments of the light-cone distribution amplitudes of the pseudoscalar mesons ? and K and the (longitudinally polarized) vector mesons ?, K*, and ?. We obtain the desired quantities with good precision and are able to discern the expected quark-mass dependence of SU(3)-flavor breaking effects. An important ingredient of the calculation is the nonperturbative renormalization of lattice operators using a regularization-independent momentum scheme
Physical Review D | 2011
Yasumichi Aoki; R. Arthur; Thomas Blum; Peter A. Boyle; D. Brömmel; Norman H. Christ; C. Dawson; Taku Izubuchi; Chulwoo Jung; C. Kelly; R.D. Kenway; M. Lightman; Robert D. Mawhinney; Shigemi Ohta; C.T. Sachrajda; E. E. Scholz; Amarjit Soni; C. Sturm; J. Wennekers; R. Zhou
We determine the neutral kaon mixing matrix element BK in the continuum limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action at two different lattice spacings. These lattice fermions have near exact chiral symmetry and therefore avoid artificial lattice operator mixing. We introduce a significant improvement to the conventional nonperturbative renormalization (NPR) method in which the bare matrix elements are renormalized nonperturbatively in the regularization invariant momentum scheme (RI-MOM) and are then converted into the MS? scheme using continuum perturbation theory. In addition to RI-MOM, we introduce and implement four nonexceptional intermediate momentum schemes that suppress infrared nonperturbative uncertainties in the renormalization procedure. We compute the conversion factors relating the matrix elements in this family of regularization invariant symmetric momentum schemes (RI-SMOM) and MS? at one-loop order. Comparison of the results obtained using these different intermediate schemes allows for a more reliable estimate of the unknown higher-order contributions and hence for a correspondingly more robust estimate of the systematic error. We also apply a recently proposed approach in which twisted boundary conditions are used to control the Symanzik expansion for off-shell vertex functions leading to a better control of the renormalization in the continuum limit. We control chiral extrapolation errors by considering both the next-to-leading order SU(2) chiral effective theory, and an analytic mass expansion. We obtain BKMS? (3??GeV)=0.529(5)stat(15)?(2)FV(11)NPR. This corresponds to B?KRGI? =0.749(7)stat(21)?(3)FV(15)NPR. Adding all sources of error in quadrature, we obtain B?KRGI? =0.749(27)combined, with an overall combined error of 3.6%.
Physical Review D | 2011
R. Arthur; Peter A. Boyle
A method for computing renormalization constants in the Rome Southampton scheme with volume sources and arbitrary momenta is described. This new method is found to enable controlled and precise continuum extrapolations and opens the way to compute the running of operators nonperturbatively in the Rome Southampton scheme. We describe this in detail and exhibit several examples of lattice step scaling functions.
Physical Review D | 2015
Eigo Shintani; R. Arthur; T. Blum; Taku Izubuchi; Chulwoo Jung; Christoph Lehner
We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in
Physical Review D | 2016
R. Arthur; Ari Hietanen; Martin Rasmus Lundquist Hansen; Claudio Pica; Francesco Sannino; Vincent Drach
N_f=2+1
arXiv: High Energy Physics - Lattice | 2015
R. Arthur; Drach; Martin Ejnar Hansen; Ari Hietanen; Claudio Pica; Francesco Sannino
lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.
arXiv: High Energy Physics - Lattice | 2015
R. Arthur; Vincent Drach; Martin Rasmus Lundquist Hansen; Ari Hietanen; Randy Lewis; Claudio Pica; Francesco Sannino
We investigate the continuum spectrum of the SU(2) gauge theory with Nf = 2 flavours of fermions in the fundamental representation. This model provides a minimal template which is ideal for a wide class of Standard Model extensions featuring novel strong dynamics that range from composite (Goldstone) Higgs theories to several intriguing types of dark matter candidates, such as the SIMPs. We improve our previous lattice analysis [1] by adding more data at light quark masses, at two additional lattice spacings, by determining the lattice cutoff via a Wilson flow measure of the w0 parameter, and by measuring the relevant renormalisation constants non-perturbatively in the RI’-MOM scheme. Our results for the lightest isovector states in the vector and axial channels, in units of the pseudoscalar decay constant, are mV/FPS∼ 13.1(2.2) and mA/FPS∼ 14.5(3.6) (combining statistical and systematic errors). Inthecontextofthecomposite(Goldstone)Higgsmodels,ourresultforthe spin-oneresonances are mV > 3.2(5) TeV and mA> 3.6(9) TeV, which are above the current LHC constraints. In the
Proceedings of The 32nd International Symposium on Lattice Field Theory — PoS(LATTICE2014) | 2015
Jonathan M. Flynn; R. Arthur; Peter A. Boyle; Dirk Brömmel; Andreas Jüttner; Christopher T. Sachrajda; Thomas Rae
We investigate non perturbatively scattering properties of Goldstone Bosons in an SU(2) gauge theory with two Wilson fermions in the fundamental representation. Such a theory can be used to build extensions of the Standard Model that unifies Technicolor and pseudo Goldstone composite Higgs models. The leading order contribution to the scattering amplitude of Goldstone bosons at low energy is given by the scattering lengths. In the context of technicolor extensions of the Standard Model the scattering lengths are constrained by WW scattering measurements. We first describe our setup and in particular the expected chiral symmetry breaking pattern. We then discuss how to compute them on the lattice and give preliminary results using finite size methods.