New extended interpolating operators for hadron correlation functions

New extended interpolating operators made of quenched three dimensional fermions are introduced in the context of lattice QCD. The mass of the 3D fermions can be tuned in a controlled way to find a better overlap of the extended operators with the states of interest. The extended operators have good renormalisation properties and are easy to control when taking the continuum limit. Moreover the short distance behaviour of the two point functions built from these operators is greatly improved. The operators have been numerically implemented and a comparison to point sources and Jacobi smeared sources has been performed on the new CLS configurations.Comment: 7 pages, 8 figures. Poster presented at the 34th annual International Symposium on Lattice Field Theory, july 24-30 2016, University of Southampton, Southampton, U.K. PoS LATTICE2016 (2016

Bilocal Dynamics for Self-Avoiding Walks

We introduce several bilocal algorithms for lattice self-avoiding walks that provide reasonable models for the physical kinetics of polymers in the absence of hydrodynamic effects. We discuss their ergodicity in different confined geometries, for instance in strips and in slabs. A short discussion of the dynamical properties in the absence of interactions is given.Comment: 38 LaTeX2e pages with 9 postscript figure

On the perturbative renormalization of four-quark operators for new physics

We discuss the renormalization properties of the full set of Δ F= 2 operators involved in BSM processes, including the definition of RGI versions of operators that exhibit mixing under RG transformations. As a first step for a fully non-perturbative determination of the scale-dependent renormalization factors and their runnings, we introduce a family of appropriate Schrödinger Functional schemes, and study them in perturbation theory. This allows, in particular, to determine the NLO anomalous dimensions of all Δ F= 1 , 2 operators in these schemes. Finally, we discuss the systematic uncertainties related to the use of NLO perturbation theory for the RG running of four-quark operators to scales in the GeV range, in both our SF schemes and standard MS ¯ and RI-MOM schemes. Large truncation effects are found for some of the operators consideredM.P. acknowledges partial support by the MIUR-PRINGrant 2010YJ2NYW and by the INFN SUMA project. C.P. and D.P. acknowledge support by Spanish MINECO Grants FPA2012-31686 and FPA2015-68541-P (MINECO/FEDER), and MINECO’s “Centro de Excelencia Severo Ochoa” Programme under Grant SEV-2012-024

Flavored tetraquark spectroscopy

The recent confirmation of the charged charmonium like resonance Z(4430) by the LHCb experiment strongly suggests the existence of QCD multi quark bound states. Some preliminary results about hypothetical flavored tetraquark mesons are reported. Such states are particularly amenable to Lattice QCD studies as their interpolating operators do not overlap with those of ordinary hidden-charm mesons

Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD

We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of $\Delta{B}=2$ parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by non-perturbatively ${\rm O}(a)$ improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered

Perturbative renormalization of DS = 2 four-fermion operators with the chirally rotated Schroedinger functional

The chirally rotated Schrödinger functional (χSF) renders the mechanism of automatic O(a) improvement compatible with Schrödinger functional (SF) renormalization schemes. Here we define a family of renormalization schemes based on the χSF for a complete basis of ΔF=2 parity-odd four-fermion operators. We compute the corresponding scale-dependent renormalization constants to one-loop order in perturbation theory and obtain their NLO anomalous dimensions by matching to the MSbar scheme. Due to automatic O(a) improvement, once the χSF is renormalized and improved at the boundaries, the step scaling functions (SSF) of these operators approach their continuum limit with O(a2) corrections without the need of operator improvement

First quenched results for the matrix elements of the B(B(s)) mixing parameter in the static limit from tmQCD

We report on a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of Delta B=2 parity-odd four-fermion operators in quenched lattice QCD. We also present some preliminary results of the matrix elements related to the mixing parameter of the B_s-meson. In our lattice formulation, the heavy quark is treated in the static approximation, while the strange one belongs to a doublet of twisted mass fermions at full twist, i.e. with twist angle alpha=pi/2. In this framework, the parity-even Delta B=2 four-fermion operators responsible for the mixing are rotated onto a linear combination of parity-odd operators in the above-mentioned basis. Their physical matrix elements between static B_s-mesons are extracted from lattice correlators with Schroedinger functional boundary conditions. We observe a suppression of excited state contributions to the B_{B_s} mixing parameter and speculate about possible explanations