Conveners
Standard Model Parameters and Renormalization
- Francesco Knechtli
Standard Model Parameters and Renormalization
- Stefan Schaefer
Standard Model Parameters and Renormalization: with Hadron Spectroscopy and Interactions
- Patrick Fritzsch
Standard Model Parameters and Renormalization
- Stefan Sint
Stefan Sint
(Trinity College Dublin)
14/07/2015, 14:00
Standard Model Parameters and Renormalization
Talk
The ALPHA collaboration has set itself the goal to determine alpha_s(m_Z) with a total error substantially below the percent level. A further step towards this goal can be taken by combining results from the recent simulations of 2+1 flavour QCD by the CLS initiative with a number of tools developed over the years: renormalized couplings in finite volume schemes, recursive finite size...
Dr
Patrick Fritzsch
(Instituto de Física Teoríca UAM/CSIC)
14/07/2015, 14:20
Standard Model Parameters and Renormalization
Talk
We present the current status of a revised strategy to compute the running of renormalized quark masses in QCD with three flavours of massless O(a) improved Wilson quarks. The strategy employed uses the standard finite-size scaling method in the Schroedinger functional and accommodates for the non-perturbative scheme-switch which becomes necessary at intermediate renormalized couplings as...
Mr
David Preti
(Instituto de Física Teoríca UAM/CSIC)
14/07/2015, 14:40
Standard Model Parameters and Renormalization
Talk
We present preliminary results for the non-perturbative renormalization of the tensor current in QCD for $N_f=0,2$, as well as an ongoing extension to $N_f=2+1$. The renormalization group running is computed in the continuum limit for a wide range of scales, using various Schrodinger Functional (SF) schemes and finite volume recursive techniques. In all these schemes, we have also computed the...
Stefan Schaefer
(NIC, DESY)
14/07/2015, 15:00
Standard Model Parameters and Renormalization
Talk
During the last two years, the CLS effort has generated ensembles with 2+1 dynamical flavors of non-perturbatively improved Wilson fermions at lattice spacings between 0.05fm and 0.09fm. Most of these ensembles are along lines of constant sum of bare sea quark masses tr(M). We give an overview of these simulations and describe our scale setting procedure using the pseudoscalar decay constants....
Dr
Pol Vilaseca Mainar
(Instituto Nazionale de Fisica Nucleare)
14/07/2015, 15:20
Standard Model Parameters and Renormalization
Talk
The chirally rotated Schrödinger functional (χSF) is a renormalization scheme which renders the mechanism of automatic O(a) improvement compatible with the Schrödinger functional (SF) formulation.
Here we define a family of renormalization schemes based on the χSF for a complete basis of ∆S = 2 parity-odd four-fermion operators.
We compute the scale-dependant renormalization constants of...
Dr
Mattia Dalla Brida
(DESY - Zeuthen)
14/07/2015, 15:40
Standard Model Parameters and Renormalization
Talk
The chirally rotated Schrödinger functional has proven to be a powerful tool in addressing non-perturbative renormalization problems in lattice QCD with Wilson-type fermions. In this contribution we consider two novel applications of the method. Firstly, we investigate the renormalization of a complete basis of ΔS=2 four-quark operators relevant for searches of Beyond the Standard Model...
Dr
Piotr Korcyl
(University of Regensburg)
14/07/2015, 16:30
Standard Model Parameters and Renormalization
Talk
We report on progress to renormalize non-perturbatively the static heavy quark theory on the lattice. In particular, we present first results for position-space renormalization scheme for heavy-light bilinears. We test our approach on RBC's 16^3 x 32 lattice ensemble with pion mass of 420 MeV, Iwasaki gauge action and domain wall light fermions.
Mr
Christian Wittemeier
(University of Muenster, Germany)
14/07/2015, 16:50
Standard Model Parameters and Renormalization
Talk
We outline our strategy to non-perturbatively match all components of the heavy-light axial and vector currents in Heavy Quark Effective Theory (HQET) at O(1/m) to finite-volume lattice QCD. Based on a tree-level study, we propose a set of matching conditions between suitable observables defined in QCD and HQET to fix the parameters of the effective theory, which are required to absorb the...
Prof.
Francesco Knechtli
(University of Wuppertal)
14/07/2015, 17:10
Standard Model Parameters and Renormalization
Talk
We simulate a theory with N_f=2 heavy quarks of mass M. At energies much
smaller than M the heavy quarks decouple and the theory can be described
by an effective theory which is a pure gauge theory to leading order in 1/M. We present results for the mass dependence of ratios such as t_0(M)/t_0(0). We compute these ratios from simulations and compare them to the perturbative prediction. The...
225.
Nonperturbative renormalization in the RI-SMOM scheme and Gribov copies for staggered bilinears
Mr
Sungwoo Park
(Seoul National University)
14/07/2015, 17:30
Standard Model Parameters and Renormalization
Talk
We present renormalization factors for the bilinear operators obtained using the nonperturbative renormalization method (NPR) in RI-SMOM scheme for improved staggered fermions on the MILC asqtad lattice (Nf=2+1). We compare the RI-SMOM result to the RI-MOM scheme result and the one-loop perturbative result. Since the NPR requires Landau gauge fixing, we study related Gribov copy problem in...
Dr
Andrew Lytle
(University of Glasgow)
14/07/2015, 17:50
Standard Model Parameters and Renormalization
Talk
I will report on a calculation of quark bilinear Z-factors for the HISQ action using non-perturbative renormalization techniques. One of the main outputs is the mass renormalization factor Z_m relating bare quark masses to the MSbar scheme. This will provide an independent determination of quark masses in addition to other methods being used by the HPQCD collaboration.
Prof.
Steven Gottlieb
(Indiana University)
14/07/2015, 18:10
Standard Model Parameters and Renormalization
Talk
The MILC Collaboration has completed production running of electromagnetic effects on light mesons using asqtad improved staggered quarks. In these calculations, the photons are quenched using the non-compact formalism. Four lattice spacings from 0.12 fm to 0.045 fm have been used. Finite volume effects with $a=0.12$ fm have been studied with spacial sizes $L_s=12$, 16, 20, 28, 40, and 48. ...
Kim Maltman
(York University)
15/07/2015, 14:00
Standard Model Parameters and Renormalization
Talk
Existing versions of the standard determinations of V_us from flavor-breaking finite energy sum rules with hadronic tau decay data as input yield V_us values 3 sigma or more below the expectations of 3-family unitarity. Slow convergence of the D=2 OPE series employed in these sum rules, however, makes it hard to assess the reliability of the use of the OPE representation. In this paper we use...
134.
Scalar and vector form factors of $D \to \pi \ell \nu$ decays with $N_f=2+1+1$ Twisted fermions
Mr
Paolo Lami
(Università degli Studi Roma Tre & INFN sezione Roma Tre)
15/07/2015, 14:20
Standard Model Parameters and Renormalization
Talk
We present lattice results for the form factors relevant for $D \to \pi \ell \nu$ decays, obtained from simulations performed by the European Twisted Mass Collaboration with $N_f=2+1+1$ flavors of dynamical quarks, at three values of the lattice spacing and pion masses as low as $210$ MeV.
We computed both the vector and the scalar form factors, studied their dependance on the momentum...
Dr
Julien Frison
(University of Edinburgh)
15/07/2015, 14:40
Standard Model Parameters and Renormalization
Talk
The phenomenology of several problems of flavour physics require the renormalisation of four-quark effective operators at the electroweak scale. While some part of the running can be done perturbatively, it is important to perform the non-perturbative renormalisation at a scale as high as possible. We will present results at an energy range where four flavours of quarks are present, and show...
Ms
Vera Guelpers
(University of Mainz)
15/07/2015, 15:00
Standard Model Parameters and Renormalization
Talk
We study the hadronic contribution to the $\gamma$-$Z$ mixing, which determines the leading order hadronic contribution to the running of the electroweak mixing angle $\theta_W$. The required vacuum polarization function $\Pi^{\gamma Z}$ is calculated from the appropriate vector correlation functions in a mixed time-momentum representation. We explicitly calculate the connected and the...
Roger Horsley
(University of Edinburgh)
15/07/2015, 15:20
Hadron Spectroscopy and Interactions
Talk
Numerical lattice QCD simulations determine mass (or other) ratios
but not the scale itself, which has to be determined from experiment.
A hadron mass such as the proton mass or decay constant such as
the pion decay constant are often used for this purpose.
We discuss here the advantages of setting the scale using
a flavour-singlet quantity, which in conjunction with simulations
keeping...
Dr
Bastian Brandt
(University of Regensburg)
15/07/2015, 15:40
Hadron Spectroscopy and Interactions
Talk
We study the change of the QCD spectrum of low-lying mesons in the presence of an external magnetic field using Wilson fermions in the quenched approximation. Motivated by qualitative differences observed in the spectra of overlap and Wilson fermions for large magnetic fields, we investigate the dependence of the additive quark mass renormalisation on the magnetic field. To this purpose we...
Mr
Masaaki Tomii
(SOKENDAI)
15/07/2015, 16:30
Standard Model Parameters and Renormalization
Talk
We investigate correlation functions of light quark flavor non-singlet bilinear operators at short distances, where non-perturbative effects are encoded in the form of Operator Product Expansion (OPE).
Comparing lattice results and continuum perturbation theory, we determine renormalization constants and vacuum expectation values appearing in OPE. We use the lattice data obtained with the...
katsumasa Nakayama
(Nagoya University)
15/07/2015, 16:50
Standard Model Parameters and Renormalization
Talk
We calculate the moments of charmonium current-current correlators with the Mobius domain-wall fermion. Following the method adopted by the HPQCD collaboration, we extract the charm quark mass by matching the results with the corresponding perturbative QCD calculations. We use the recently generated domain-wall fermion ensembles by the JLQCD collaboration at lattice spacings a = 0.083 fm,...
Randy Lewis
(York University)
15/07/2015, 17:10
Standard Model Parameters and Renormalization
Talk
The QCD coupling appears in the perturbative expansion of the current-current two-point (vacuum polarization) function. Any lattice calculation of vacuum polarization is plagued by several competing non-perturbative effects at small momenta and by discretization errors at large momenta. We work in an intermediate region and compute vacuum polarization for many off-axis momentum directions on...
Prof.
Gerrit Schierholz
(DESY)
15/07/2015, 17:30
Standard Model Parameters and Renormalization
Talk
It is argued that low energy parameters, such as the light quark masses, are related by infrared fixed points of the underlying theory. Implications for the u and d quark masses are discussed.
Dr
Michele Brambilla
(INFN Milano Bicocca and Università di Parma)
15/07/2015, 17:50
Standard Model Parameters and Renormalization
Talk
We present an implementation of clover fermions in Numerical Stochastic Perturbation Theory. Two loop computations are already possible, e.g. we already computed critical mass. We stress that any two loop computation only relies on the known value of c_SW to one loop.
A two loop determination of c_SW would be of great interest: we report on the status of our computation of the latter.
