First Lattice QCD Study of B-physics With Four Flavors of Dynamical Quarks
Istituto Nazionale di Fisica Nucleare (INFN) - Sezione Roma Tre (Italy)
Local Project ID:
HPC Platform used:
JUGENE/JUQUEEN of JSC
Flavor physics deals, basically, with transitions among quarks induced by the weak interaction. Since quarks are not free particles, the quark mixing can be studied only through the decays of systems made of quarks (namely, mesons and baryons). The structure of such systems is governed by another interaction, the strong one, for which our fundamental theory is the quantum chromodynamics (QCD). In this theory, quarks interact with gluons in a highly non-perturbative way, which can only be properly taken into account by using simulations performed on a discretized space-time lattice.
By using lattice QCD, the aim of the scientists is to calculate from first principles several B-physics observables with unprecedented accuracy based on the use of the gluon configurations produced by the European Twisted Mass Collaboration with four flavors of dynamical quarks (Nf = 2+1+1). These include the non-perturbative effects due to the light mass-degenerate up (u) and down (d) quarks, as well as to the strange (s) and the charm (c) quarks with masses close to their physical values. Such a setup is the closest one to the real world.
The B-physics observables that were computed accurately are:
The present situation of the lattice determinations for some of the quantities of interest in our project is summarized in Figs. 1 and 2, taken from the recent updated publication of the FLAG working group .
In order to get very precise results, the number of lattice points has to be sufficiently large. Therefore the lattice QCD simulations of the present project have been carried out on the HPC Tier-0 systems JUGENE and JUQUEEN of the JSC (Germany) and FERMI of the CINECA (Italy).
The analysis of all the correlation functions calculated in the project is in progress and some preliminary results have been presented already at the recent lattice Conference in Mainz (2013).
 S. Aoki et al. [FLAG working group], Review of lattice results concerning low energy particle physics, arXiv:1310.8555 [hep-lat].
 N. Carrasco et al. [ETM collaboration], A Nf =2+1+1 “twisted” determination of the b-quark mass, fB and fBs, arXiv:1311.2837 [hep-lat].
 N. Carrasco et al. [ETM collaboration], K and D oscillations in the Standard Model from Nf=2+1+1 twisted mass, arXiv:1310.5461 [hep-lat].
Istituto Nazionale di Fisica Nucleare (INFN) - Sezione Roma Tre
Via della Vasca Navale 84, I-00146 Roma/Italy