Wed·Dec 14, 2022Wednesday·December 14, 2022

1. 01*

   Continuum limit of parton distribution functions from the pseudo-distribution approach on the lattice

   Manjunath Bhat🇵🇱 · Wojciech Chomicki🇵🇱 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Jeremy R. Green🇩🇪 · Aurora Scapellato🇺🇸

   Precise exploration of the partonic structure of the nucleon is one of the most important aims of high-energy physics. In recent years, it has become possible to address this topic with first-principle lattice QCD investigations. In this talk, we focus on the so-called pseudo-distribution approach to determine the isovector unpolarized PDFs. In particular, we employ three lattice spacings to study discretization effects and extract the distributions in the continuum limit, at a pion mass of around 370 MeV. Also, for the first time with pseudo-PDFs, we explore effects of the 2-loop matching from pseudo- to light-cone distributions.

   hep-latPoS(2023)·1 citation
2. 02*

   Twisted mass ensemble generation on GPU machines

   Bartosz Kostrzewa🇩🇪 · Simone Bacchio🇨🇾 · Jacob Finkenrath🇨🇾 · Marco Garofalo🇩🇪 · Ferenc Pittler🇨🇾 · Simone Romiti🇩🇪 · Carsten Urbach🇩🇪

   We present how we ported the Hybrid Monte Carlo implementation in the tmLQCD software suite to GPUs through offloading its most expensive parts to the QUDA library. We discuss our motivations and some of the technical challenges that we encountered as we added the required functionality to both tmLQCD and QUDA. We further present some performance details, focussing in particular on the usage of QUDA's multigrid solver for poorly conditioned light quark monomials as well as the multi-shift solver for the non-degenerate strange and charm sector in $N_f=2+1+1$ simulations using twisted mass clover fermions, comparing the efficiency of state-of-the-art simulations on CPU and GPU machines. We also take a look at the performance-portability question through preliminary tests of our HMC on a machine based on AMD's MI250 GPU, finding good performance after a very minor additional porting effort. Finally, we conclude that we should be able to achieve GPU utilisation factors acceptable for the current generation of (pre-)exascale supercomputers with subtantial efficiency improvements and real time speedups compared to just running on CPUs. At the same time, we find that future challenges will require different approaches and, most importantly, a very significant investment of personnel for software development.

   hep-latPoS(2023)·29 citations
3. 03*

   Running HMC Simulation with Python via QUDA

   Shuhei Yamamoto🇨🇾 · Simone Bacchio🇨🇾 · Jacob Finenrath

   Lyncs-API is a Python API for Lattice QCD applications. It is designed as a Python toolkit that allows the user to use and run various lattice QCD libraries while programming in Python. The goal is to provide the user an easy programming experience without scarifying performance across multiple platforms, by preparing a common framework for various softwares for lattice QCD calculations. As such, it contains interfaces to, e.g., c-lime, DDalphaAMG, tmLQCD, and QUDA. In this proceeding, we focus on a Lyncs interface to QUDA, named Lyncs-QUDA, and present a small tutorial on how to use this Python interface to perform a HMC simulation using QUDA.

   hep-latPoS(2023)·4 citations
4. 04*

   The $\eta \to {\gamma }^{\ast }{\gamma }^{\ast }$ transition form factor and the hadronic light-by-light $\eta$-pole contribution to the muon $g-2$ from lattice QCD

   Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Sebastian Burri🇨🇭 · Jacob Finkenrath🇨🇾 · Andrew Gasbarro🇨🇭 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Gurtej Kanwar🇨🇭 · Bartosz Kostrzewa🇩🇪 · Konstantin Ottnad🇩🇪 · Marcus Petschlies🇩🇪 · Ferenc Pittler🇨🇾 · Carsten Urbach🇩🇪 · Urs Wenger🇨🇭

   We calculate the double-virtual $\eta \to {\gamma }^{\ast }{\gamma }^{\ast }$ transition form factor ${\mathcal{F}}_{\eta \to {\gamma }^{\ast }{\gamma }^{\ast }}(q_1^2,q_2^2)$ from first principles using a lattice QCD simulation with $N_f=2+1+1$ quark flavors at the physical pion mass and at one lattice spacing and volume. The kinematic range covered by our calculation is complementary to the one accessible from experiment and is relevant for the $\eta$-pole contribution to the hadronic light-by-light scattering in the anomalous magnetic moment $a_{\mu }=(g-2)/2$ of the muon. From the form factor calculation we extract the partial decay width $\Gamma (\eta \to \gamma \gamma )=323(85{)}_{\text{stat}}(22{)}_{\text{syst}}$ eV and the slope parameter $b_{\eta }=1.19(36{)}_{\text{stat}}(16{)}_{\text{syst}}$ GeV${}^{-2}$. For the $\eta$-pole contribution to $a_{\mu }$ we obtain $a_{\mu }^{\eta -\text{pole}}=13.2(5.2{)}_{\text{stat}}(1.3{)}_{\text{syst}}\cdot 10^{-11}$.

   hep-lathep-phPRD(2023)·39 citations
5. 05*

   Exploring the large-$N_c$ limit with one quark flavour

   Michele Della Morte🇩🇰 · Benjamin Jäger · Sofie Martins🇩🇰 · Francesco Sannino🇮🇹 · J. Tobias Tsang🇨🇭 · Felix P. G. Ziegler🇬🇧

   We use one-flavour QCD ($N_c=3$) as a proxy to understand $\mathcal{N}=1$ SYM. For our simulations, we use tree-level improved Wilson fermions and Symanzik improved gauge action. The hadron spectrum is obtained by using LapH smearing for different masses and simulation volumes. We also report on our efforts to increase the number of colours in our simulations, where we find that the simulations show increasing topological freezing for larger $N_c$.

   hep-latPoS(2023)·10 citations
6. 06*

   The V-QCD baryon : numerical solution and baryon spectrum

   M. Järvinen🇰🇷 · E. Kiritsis🇫🇷 · F. Nitti🇫🇷 · E. Préau🇫🇷

   The single baryon solution of V-QCD is numerically computed. The spectrum of spin and isospin modes is also computed by quantizing the light fluctuations around the baryon. It is shown that there is a partial restoration of chiral symmetry at the baryon center.

   ↳ hep-thhep-lathep-phnucl-thJHEP(2023)·19 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.