arXiv subjects

Sara Rosso

Publications and source records attributed to Sara Rosso.

6 recordsLinked to original sources

arXiv2026

Comparing RM123 and non-perturbative QCD+QED approaches to the HVP with C-periodic boundary conditions

Isospin-breaking corrections to the HVP are among the leading sources of uncertainty in the Standard Model prediction of the muon $g-2$. In recent work by the RC$^{\star}$ collaboration, we compute the intermediate window contribution for a flavour non-singlet current using two strategies to include isospin-breaking corrections: the RM123 approach and a fully non-perturbative dynamical QCD+QED simulation. In both computations, we use $C$-periodic spatial boundary conditions to ensure that locality, gauge invariance, and translational invariance are preserved throughout the calculation. At fixed lattice spacing and volume with $N_f =1+2+1$ dynamical fermions, and fully including sea-quark effects in both computations, we find that simulating the full QCD+QED distribution yields smaller uncertainties for a fixed statistics. We summarize the comparison of the two approaches and discuss the implications for future lattice QCD+QED computations.

hep-lat↗

arXiv2026

Baryon masses with C-periodic boundary conditions

Isospin-breaking corrections pose a significant challenge to lattice simulations, both because of the splitting between the up and down quark masses and, in particular, the need to include QED effects. The RC* collaboration has developed the openQxD code, based on openQCD, which enables fully dynamical QCD+QED simulations through the implementation of C-periodic boundary conditions. We use this code to measure baryon masses, with a special focus on the {\Omega^-} baryon mass, whose precise determination is especially important since it has been used to set the scale of lattice simulations. Due to the use of C-periodic boundary conditions, the two-point function of the {\Omega^-} baryon gets additional partially connected contributions, which vanish in the infinite-volume limit and which we are computing for the first time. We will present preliminary results for baryon masses obtained on QCD ensembles with C-periodic boundary conditions, at an unphysical pion mass of approximately 400 MeV.

hep-lat↗

arXiv2025

Update on the isospin breaking corrections to the HVP with C-periodic boundary conditions

In the RC$^\star$ collaboration, we simulate lattice QCD+QED using $C-$periodic spatial boundary conditions to ensure that locality, gauge invariance, and translational invariance are preserved throughout the calculation. We present our progress in computing isospin-breaking (IB) corrections to the leading hadronic contribution to $(g-2)_\mu$. We compare two ways of including the IB corrections: the RM123 method and dynamical QCD+QED simulations, both with $C-$periodic boundary conditions. The two calculations are performed at $\beta=3.24$ with four flavours of $\mathcal{O}(a)-$improved Wilson fermions; the QCD ensemble features $SU(3)-$symmetric sea quarks plus charm, while down and strange quarks are degenerate in QCD+QED gauge ensembles.

hep-lat↗

arXiv2025

Partially connected contributions to baryon masses in QCD+QED

Full QCD+QED simulations allow to evaluate isospin breaking corrections to hadron masses. With the openQxD code, we are able to perform these simulations employing C-periodic boundary conditions, implemented through a doubling of the physical lattice along one spatial direction. The use of these boundary conditions introduces non-zero Wick contractions between two quark or two antiquark fields, that, in the case of the computation of baryon masses, lead to partially connected additional contributions that we expect to vanish in the infinite volume limit. These contributions are challenging because they involve an all-to-all propagator connecting one point in the physical lattice and one in the mirror lattice. We present a way to compute these corrections to the $\Omega^-$ baryon mass using a combination of point and stochastic source inversions. This work is part of the program of the RC* collaboration.

hep-lat↗

arXiv2025

Error Scaling of Sea Quark Isospin-Breaking Effects

Sea-quark isospin-breaking effects (IBE) are difficult to compute since they require the evaluation of all-to-all propagators. However, the quest for high-precision calculations motivates a detailed study of these contributions. There are strong arguments that the stochastic error associated with these quantities should diverge in the continuum and infinite-volume limit, resulting in a possible bottleneck for the method. In this work, we present the study of the error scaling for these quantities using $N_f=3$ $O(a)$-improved Wilson fermions QCD with C-periodic boundary conditions in space, a pion mass $M_{\pi}=400$ MeV, a range of lattice spacings $a=0.05, 0.075, 0.1$ fm, and volumes $L=1.6, 2.4, 3.2$ fm. The analysis of the error as a function of the number of stochastic sources shows that we reach the gauge error for the dominant contributions. The errors do not show the leading order divergence $1/a$ for strong-IBE and $1/a^2$ for electromagnetic IBE, in the considered range of lattice spacings. On the other hand, our data are consistent with the predicted leading divergence $\sqrt{V}$.

hep-lat↗

arXiv2025

$O(a)$-improved QCD+QED Wilson Dirac operator on GPUs

Markov Chain Monte Carlo simulations of lattice Quantum Chromodynamics (QCD) are the only known tool to investigate non-perturbatively the theory of the strong interaction and are required to perform precision tests of the Standard Model of Particle Physics. As the Markov Chain is a serial process, the sole option for improving the sampling rate is accelerating each individual update step. Heterogeneous clusters of GPU-accelerated nodes offer large total memory bandwidth which can be used to speed-up our application, openQxD-1.1, which is dominated by inversions of the Dirac operator, a large sparse matrix. In this work we investigate offloading the inversion to GPU using the lattice-QCD library QUDA, and our early results demonstrate a significant potential speed-up in the time-to-solution for state-of-the-art problem sizes. Minimal extensions to the existing QUDA library are required for our specific physics programme while greatly enhancing the performance portability of our code and retaining the reliability and robustness of existing applications in openQxD-1.1. Our new interface will enable us to utilize pre-exascale infrastructure and reduce the systematic uncertainty in our physics predictions by incorporating the effects of quantum electromagnetism (QED) in our simulations.

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