We present preliminary results in the charm sector from a mixed-action setup, in which CLS \(N_f=2+1\) ensembles are combined with a Wilson twisted mass valence action. We study the continuum and ...chiral limits of charm quark observables such as the decay constants \(f_{D_{(s)}}\) and the renormalized charm-quark mass.
We introduce a mixed-action approach based on CLS ensembles, where a valence
$N_f$=2+1+1 Twisted Mass QCD action is combined with the $N_f$=2+1
non-perturbatively O$(a)$-improved Wilson sea sector. ...We show that for
maximally twisted valence quarks, the automatic O$(a)$-improvement of this
set-up holds up to lattice artifacts coming from sea quark mass effects.
Furthermore, we introduce a three-dimensional Gradient Flow smearing in order
to tame the signal to noise ratio problem.
We discuss an alternate scheme, or a 'line of constant physics', which can be used when computing isospin breaking corrections to hadronic quantities. We show that within a certain class of schemes ...one can separate the electromagnetic corrections from the strong isospin breaking corrections at leading order, meaning that within this class scheme-ambiguities are higher order effects.
Within the HMC algorithm, we discuss how, by using the shadow Hamiltonian and the Poisson brackets, one can achieve a simple factorization in the dependence of the Hamiltonian violations upon either ...the algorithmic parameters or the parameters specifying the integrator. We consider the simplest case of a second order (nested) Omelyan integrator and one level of Hasenbusch splitting of the determinant for the simulations of a QCD-like theory (with gauge group SU(2)). Given the specific choice of the integrator, the Poisson brackets reduce to the variances of the molecular dynamics forces. We show how the factorization can be used to optimize in a very economical and simple way both the algorithmic and the integrator parameters with good accuracy.
We consider the possibility of using reweighting techniques in order to correct for the breaking of unitarity when twisted boundary conditions are imposed on valence fermions in simulations of ...lattice gauge theories. We start by studying the properties of reweighting factors and their variances at tree-level. That leads us to the introduction of a factorization for the fermionic reweighting determinant. In the numerical, stochastic, implementation of the method, we find that the effect of reweighting is negligible in the case of large volumes but it is sizeable when the volumes are small and the twisting angles are large. More importantly, we find that for un-improved Wilson fermions, and in small volumes, the dependence of the critical quark mass on the twisting angle is quite pronounced and results in large violations of the continuum dispersion relation.
We present a practical strategy to optimize a set of Hybrid Monte Carlo parameters in simulations of QCD and QCD-like theories. We specialize to the case of mass-preconditioning, with multiple ...time-step Omelyan integrators. Starting from properties of the shadow Hamiltonian we show how the optimal setup for the integrator can be chosen once the forces and their variances are measured, assuming that those only depend on the mass-preconditioning parameter.
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour ...and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, \(\theta\). As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of \(\theta=\pi/2\) in a volume \(16\times 8^3\), and we observe a systematic upward shift in the pion dispersion relation.
A mixed action composed of valence quark flavours regularized with a fully-twisted tmQCD action and of \(N_f=2+1\) flavours of non-perturbatively \({\rm O}(a)\)-improved Wilson sea quarks is ...described. Two procedures for the matching of sea and valence quark masses are discussed. We report about a comparison of the continuum-limit scaling of pseudoscalar meson observables and of quark masses using the sea and valence actions.
The term Headache Disorders (HD) refers to a number of nervous system pathologies characterised by recurrent headaches. Despite the serious impact HD have on the health system, society, and the ...economy, these are an underestimated, underdiagnosed, and, hence, undertreated phenomenon. Triptans are the first-line therapy for the acute treatment of moderate to severe migraine but their utilization is still inadequate, perhaps also because in Italy no triptan can be bought without a medical prescription. In this article, the data from a 2016–2017 study has been further analysed with the aim of evaluating any associations between the use of triptans and the other series of variables identified in the questionnaire. This further analysis has been connected to the role that community pharmacies could play on this issue. The questionnaire was administered to 4,424 pharmacy users by 610 purposely trained pharmacists working in 514 pharmacies. The survey was carried out in 19 of the 20 Italian regions. The data shows that only 25% of patients suffering from HDs are prescribed triptans. Older patients, those with definite migraines, and those with a chronic disorder resort more frequently to this class of pharmaceuticals, as do those patients in care at a specialist headache centre. The multivariable analysis also confirmed these results. Our study, which performed a direct detection, in real life, on patients requesting pharmacological treatment for a migraine headache, therefore confirmed the need to investigate the reasons behind the low use and prescription of triptans in the Italian population. Moreover, any future studies should take advantage of community pharmacies, plan actions that would allow a series of evaluations over time of the requirements of migraineurs, and establish a process to put these patients under the care of the pharmacy to ensure adherence to therapy.
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