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We compute charm and bottom quark masses in the quenched approximation and in the continuum limit of lattice QCD. We make use of a step scaling method, previously introduced to deal with two scale problems, that allows to take the continuum limit of the lattice data. We determine the RGI quark masses and make the connection to the M S scheme.

Abstract:The definition and computation of the topological susceptibility in non-abelian gauge theories is complicated by the presence of non-integrable short-distance singularities. Recently, alternative representations of the susceptibility were discovered, which are singularity-free and do not require renormalization. Such an expression is here studied quantitatively, using the lattice formulation of the SU(3) gauge theory and numerical simulations. The results confirm the expected scaling of the susceptibility with respect to the lattice spacing and they also agree, within errors, with computations of the susceptibility based on the use of a chiral lattice Dirac operator.

The B K parameter is computed in quenched lattice QCD with Wilson twisted mass fermions. Two variants of tmQCD are used; in both of them the relevant S = 2 four-fermion operator is renormalised multiplicatively. The renormalisation adopted is non-perturbative, with a Schrödinger functional renormalisation condition. Renormalisation group running is also non-perturbative, up to very high energy scales. In one of the two tmQCD frameworks the computations have been performed at the physical K-meson mass, thus eliminating the need of mass extrapolations. Simulations have been performed at several lattice spacings and the continuum limit was reached by combining results from both tmQCD regularisations. Finite volume effects have been partially checked and turned out to be small. Exploratory studies have also been performed with non-degenerate valence flavours. The final result for the RGI bag parameter, with all sources of uncertainty (except quenching) under control, isB K = 0.789 ± 0.046.

ENEA is the Italian National Agency for New Technologies, Energy and Sustainable Economic Development. ENEA operates in many sectors among which the most important are: energy technologies, materials physics, life sciences and climate. In the framework of its institutional mission, the ICT Division provides computing and storage resources integrated into ENEAGRID/CRESCO, an infrastructure distributed over 6 sites, whose main facilities are the HPC CRESCO clusters. The bulk of all storage is based on IBM Spectrum Scale (GPFS) since many years. The access to data, even over WAN, is managed by GPFS clusters. In May 2018 the new cluster CRESCO6 was inaugurated. CRESCO6, a 1.4 Pflops based on Intel Xeon X86_64 SkyLake CPU ranked at 420 th of TOP 500 Nov.2018 list. While the interconnection of CRESCO6 is based on Intel Omni-Path (OPA) (100 Gbps), the previous CRESCO4 and CRESCO5 clusters have a network based on InfniBand QDR Truescale fabric (40 Gbps). Hence, in order to provides storage to all CRESCO clusters a GPFS multifabric layout has been implemented after dedicated tests. The work describes the ENEAGRID/CRESCO infrastructure and in particular the solution adopted to implement the GPFS multifabric.

We compute the decay constants for the heavy-light pseudoscalar mesons in the quenched approximation and continuum limit of lattice QCD. Within the Schrödinger Functional framework, we make use of the step scaling method, which has been previously introduced in order to deal with the two scale problem represented by the coexistence of a light and a heavy quark. The continuum extrapolation gives us a value f Bs = 192(6)(4) MeV for the B s meson decay constant and f Ds = 240(5)(5) MeV for the D s meson.

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