arXiv subjects

Marco Catillo

Publications and source records attributed to Marco Catillo.

14 recordsLinked to original sources

arXiv2023

Strange and charm contributions to the HVP from C* boundary conditions

We present preliminary results for the determination of the leading strange and charm quark-connected contributions to the hadronic vacuum polarization contribution to the muon's g-2. Measurements are performed on the RC* collaboration's QCD ensembles, with 3+1 flavors of O(a) improved Wilson fermions and C* boundary conditions. The HVP is computed on a single value of the lattice spacing and two lattice volumes at unphysical pion mass. In addition, we compare the signal-to-noise ratio for different lattice discretizations of the vector current.

hep-lat↗

arXiv2022

Hadronic vacuum polarization with C* boundary conditions

We present a progress report on the calculation of the connected hadronic contribution to the muon g-2 with C* boundary conditions. For that purpose we use a QCD gauge ensemble with 3+1 flavors and two QCD+QED gauge ensembles with 1+2+1 flavors of dynamical quarks generated by the RC* collaboration. We detail the calculation of the vector mass and elaborate on both statistical and systematic errors.

hep-lat↗

arXiv2022

Tuning of QCD+QED simulations with C$^{\star}$ boundary conditions

We give an update on the ongoing effort of the RC$^\star$ collaboration to generate fully dynamical QCD+QED ensembles with C$^\star$ boundary conditions using the openQ$^\star$D code. The simulations were tuned to the U-symmetric point ($m_d = m_s$) with pions at $m_{\pi^{\pm}} \approx 400$ MeV. The splitting of the light mesons is used as one of three tuning observables and fixed to $m_{K^{0}} - m_{K^{\pm}} \approx 5$ MeV and $m_{K^{0}} - m_{K^{\pm}} \approx 25$ MeV on ensembles with renormalized electromagnetic coupling $\alpha_{\text{R}} \approx \alpha_{\text{phys}}$ and $\alpha_R \approx 5.5\alpha_{phys}$ respectively. The tuning of the three independent quark masses to the desired lines of constant physics is particularly challenging. We will define the chosen hadronic renormalization scheme, and we will present a tuning strategy based on a combination of mass reweighting and linear interpolation to explore the parameter space. We will comment on finite-volume effects comparing meson masses on two different volumes with $m_{\pi^{\pm}} L \approx 3.2$ and $m_{\pi^{\pm}} L \approx 5.1$. We will also provide some technical details on our updated strategy to calculate the sign of the fermionic Pfaffian, which arises in presence of C$^\star$ boundary conditions in place of the standard fermionic determinant. More technical details on the generation of the configurations can be found in J. L\"ucke's proceedings

hep-lat↗

arXiv2022

$N_f = 1+2+1$ QCD+QED simulations with C$^\star$ boundary conditions

We give an update on the ongoing effort of the RC$^\star$ collaboration to generate fully dynamical QCD+QED configurations with C$^\star$ boundary conditions using the openQ$^\star$D code. The simulations are tuned to the U-symmetric point ($m_d=m_s$) with pions at $m_{\pi^\pm}\approx 400$ MeV. The splitting of the light mesons is used as one of three tuning observables and fixed to $m_{K^0} - m_{K^\pm} \approx 5$ MeV and $m_{K^0} - m_{K^\pm} \approx 25$ MeV on ensembles with renormalized electromagnetic coupling $\alpha_\mathrm{R} \approx \alpha_\mathrm{phys.}$ and $\alpha_\mathrm{R}\approx 5.5 \alpha_\mathrm{phys.}$ respectively. We will discuss some details concerning our tuning strategy and present the calculation of the meson and baryon masses. Finally, we will also present a cost analysis for our simulations. More technical details on finite-volume effects and the tuning can be found in A. Cotellucci's proceedings.

hep-lat↗

arXiv2022

First results on QCD+QED with C* boundary conditions

Accounting for isospin-breaking corrections is critical for achieving subpercent precision in lattice computations of hadronic observables. A way to include QED and strong-isospin-breaking corrections in lattice QCD calculations is to impose C$^\star$ boundary conditions in space. Here, we demonstrate the computation of a selection of meson and baryon masses on two QCD and five QCD+QED gauge ensembles in this setup, which preserves locality, gauge and translational invariance all through the calculation. The generation of the gauge ensembles is performed for two volumes, and three different values of the renormalized fine-structure constant at the U-symmetric point, corresponding to the SU(3)-symmetric QCD in the two ensembles where the electromagnetic coupling is turned off. We also present our tuning strategy and, to the extent possible, a cost analysis of the simulations with C$^\star$ boundary conditions.

hep-lat↗

arXiv2022

Implementing noise reduction techniques into theOpenQ*D package

We present the results of testing a new technique for stochastic noise reduction in the calculation of propagators by implementing it in OpenQ*D for two ensembles with O(a) improved Wilson fermion action, with periodic boundary conditions and pion masses of 437 MeV and 331 MeV, for the connected vector and pseudoscalar correlators. We find that the technique yields no speedup compared to traditional methods, owning to the failure of its underlying assumption that the spectra of the spatial Laplacian and Dirac operators are sufficiently similar for the technique's purposes.

hep-lat↗

arXiv2021

Baryon masses from full QCD+QED${}_\text{C}$ simulations

In these proceedings we present preliminary results for the masses of the proton, neutron and $\Omega^-$ baryons obtained from QCD+QED lattice simulations performed with four dynamical quarks using C$^*$ boundary conditions. These results are part of the ongoing effort of the RC${}^*$ collaboration discussed in the companion proceedings, and have been obtained on a single ensemble in which the renormalised electromagnetic coupling is $\alpha_{\text{em}}\sim 0.04$, the physical volume is $L\sim 1.7$ fm and the masses of the four dynamical quarks have been tuned at the $U$--spin symmetric point $m_d=m_s$. We demonstrate on this unphysical ensemble that baryon masses can be calculated with satisfactory precision when including QED without the need for gauge--fixing and perturbation theory. This makes us confident in the effectiveness of the strategy presented here also in the case of simulations closer to the physical point.

hep-lat↗

arXiv2021

Chiralspin symmetry and confinement

Interesting lattice QCD simulations at high temperature in QCD and particular truncated studies have shown the emergence of an unexpected group symmetry, so called \textit{chiralspin}. However this is not a symmetry of the QCD action for free quarks, which makes unclear the transition to deconfinement at high temperature in QCD. Therefore we try to redefine this group so that is a symmetry of free quark action and it is consistent with the presence of deconfinement in QCD.

hep-lat↗

arXiv2021

A chiralspin symmetry in QCD in Minkowski space-time

In this paper, we look how to construct in Minkowski space-time a new type of \textit{chiralspin} group transformation of the spinor fields, similar to the one discovered by recent works of \textit{Glozman et al.} in the context of high temperature QCD and truncated studies in lattice calculations. Afterwards, we prove the invariance of free massless fermionic action under such group transformations, as well the invariance of the Hamiltonian of free massless fermions. At the end, the possible presence of a symmetry driven by such new \textit{chiralspin} group at high temperature QCD, also at non zero chemical potential, is discussed.

hep-lat↗

arXiv2021

On $SU(2)_{CS}$-like groups and invariance of the fermionic action in QCD

In this work, we introduce some new $U(1)$ symmetry groups of the free fermionic action in euclidean space-time, which are a consequence of parity and time-reversal symmetries. Afterwards, we discuss how the introduction of a gauge interaction affects the invariance of the action, with special reference to QCD. Moreover, inspired by recent QCD lattice results of \textit{Glozman et al.}, in which an interesting and unexpected symmetry group has been observed, namely $SU(2)_{CS}$ (that contains $U(1)_A$ as subgroup), we build other $SU(2)_{CS}$-like groups in euclidean space-time using the previous introduced $U(1)$ groups. Finally we argue about the possible invariance of the fermionic action with respect these new $SU(2)_{CS}$-like groups and its consequence on the hadron temporal correlators.

hep-lat↗

arXiv2021

An update on QCD+QED simulations with C* boundary conditions

We present two novelties in our analysis of fully dynamical QCD+QED ensembles with C* boundary conditions. The first one is the explicit computation of the sign of the Pfaffian. We present an algorithm that provides a significant speedup compared to traditional methods. The second one is a reweighting of the mass in the context of the RHMC. We have tested the techniques on both pure QCD and QCD+QED ensembles with pions at $m_{\pi^\pm}\approx400$ MeV, a lattice spacing of $a\approx0.05$ fm, a fine-structure constant of $\alpha_{\mathrm{R}}=0$ and $0.04$.

hep-lat↗

arXiv2021

Gap in the Dirac spectrum and quark propagator symmetries in lattice QCD

Recent studies on lattice QCD have shown the emergence of large symmetries at high temperature. This includes not only the restoration $SU(n_F)_L \times SU(n_F)_R$, but also the effective emergence of an unexpected symmetry group, namely $SU(2)_{CS}$, which contains $U(1)_A$ as subgroup. At the same time, at high $T$, a gap in Dirac spectrum appears. As it is argued in several works of \textit{L. Glozman et al.}, there should be a connection between a gap in the Dirac spectrum and the presence of $SU(2)_{CS}$.In this paper, we analyze whether the quark propagator can be invariant under $SU(n_F)_L \times SU(n_F)_R$ and $SU(2)_{CS}$ transformations, in case of a gap in the Dirac spectrum, and consequently the invariance of hadron correlators, giving the condition for a quark propagator to be invariant under $SU(2)_{CS}$.

hep-lat↗

arXiv2020

From string breaking to quarkonium spectrum

We present a preliminary computation of potentials between two static quarks in $n_f=2$ QCD with O(a) improved Wilson fermions. We explore different smearing choices (HYP, HYP2 and APE) and their effect on the signal to noise ratio in the computed static potentials. This is a part of a larger effort concerning, at first, a precise computation of the QCD string breaking parameters and their subsequent utilization for the recent approach based on Born-Oppenheimer approximation (Bicudo et al. 2020 \cite{Bicudo:2019ymo}) to study quarkonium resonances and bound states.

hep-lat↗

arXiv2019

Chiral-spin symmetry emergence in baryons and eigenmodes of the Dirac operator

Truncating the low-lying modes of the lattice Dirac operator results in an emergence of the chiral-spin symmetry $SU(2)_{CS}$ and its flavor extension $SU(2N_F)$ in hadrons. These are symmetries of the quark - chromo-electric interaction and include chiral symmetries as subgroups. Hence the quark - chromo-magnetic interaction, which breaks both symmetries, is located at least predominantly in the near - zero modes. Using as a tool the expansion of propagators into eigenmodes of the Dirac operator we here analytically study effects of a gap in the eigenmode spectrum on baryon correlators. We find that both $U(1)_A$ and $SU(2)_L \times SU(2)_R$ emerge automatically if there is a gap around zero. Emergence of larger $SU(2)_{CS}$ and $SU(4)$ symmetries requires in addition a microscopical dynamical input about the higher-lying modes and their symmetry structure.

hep-ph↗