7 research outputs found
Neural Networks Asymptotic Behaviours for the Resolution of Inverse Problems
This paper presents a study of the effectiveness of Neural Network (NN)
techniques for deconvolution inverse problems relevant for applications in
Quantum Field Theory, but also in more general contexts. We consider NN's
asymptotic limits, corresponding to Gaussian Processes (GPs), where
non-linearities in the parameters of the NN can be neglected. Using these
resulting GPs, we address the deconvolution inverse problem in the case of a
quantum harmonic oscillator simulated through Monte Carlo techniques on a
lattice. In this simple toy model, the results of the inversion can be compared
with the known analytical solution. Our findings indicate that solving the
inverse problem with a NN yields less performing results than those obtained
using the GPs derived from NN's asymptotic limits. Furthermore, we observe the
trained NN's accuracy approaching that of GPs with increasing layer width.
Notably, one of these GPs defies interpretation as a probabilistic model,
offering a novel perspective compared to established methods in the literature.
Our results suggest the need for detailed studies of the training dynamics in
more realistic set-ups
, LFU and symmetry breaking in decays using Lattice QCD and Unitarity
We present an application of the unitarity-based dispersion matrix (DM)
approach to the extraction of the CKM matrix element from the
experimental data on the exclusive semileptonic decays. The DM method allows to achieve a non-perturbative,
model-independent determination of the momentum dependence of the semileptonic
form factors. Starting from lattice results available at large values of the
4-momentum transfer and implementing non-perturbative unitarity bound, the
behaviour of the form factors in their whole kinematical range is obtained
without introducing any explicit parameterization of their momentum dependence.
We consider the four exclusive semileptonic decays and extract from the experimental data for each
transition. The average over the four channels is , which is compatible with the latest inclusive determination at
level. We address also the issue of Lepton Flavour Universality by
computing pure theoretical estimates of the ratios of the branching
fractions for each channel, where is a light lepton. In the case of a
light spectator quark we obtain and ,
which are compatible with the corresponding experimental values within
. In the case of a strange spectator quark we obtain
and . The different
values for and may reflect symmetry breaking
effects, which seem to be present in some of the lattice form factors,
especially at large values of the recoil.Comment: Contribution to ICHEP-202
Sphaleron rate of QCD
We compute the sphaleron rate of QCD at the physical point for a
range of temperatures MeV MeV. We adopt a
strategy recently applied in the quenched case, based on the extraction of the
rate via a modified version of the Backus-Gilbert method from
finite-lattice-spacing and finite-smoothing-radius Euclidean topological charge
density correlators. The physical sphaleron rate is finally computed by
performing a continuum limit at fixed physical smoothing radius, followed by a
zero-smoothing extrapolation.Comment: Main text: 5 pages, 4 figures. Supplementary Material: 8 pages, 29
figure
Sphaleron rate from lattice QCD
We compute the sphaleron rate on the lattice from the inversion of the
Euclidean time correlators of the topological charge density, performing also
controlled continuum and zero-smoothing extrapolations. The correlator
inversion is performed by means of a recently-proposed modification of the
Backus-Gilbert method.Comment: 8 pages, 11 figures, Proceedings of the 26th international conference
in HEP (QCD23), 10-14th july 2023, Montpellier-F
, LFU and symmetry breaking in decays using Lattice QCD and Unitarity
International audienceWe present an application of the unitarity-based dispersion matrix (DM) approach to the extraction of the CKM matrix element from the experimental data on the exclusive semileptonic decays. The DM method allows to achieve a non-perturbative, model-independent determination of the momentum dependence of the semileptonic form factors. Starting from lattice results available at large values of the 4-momentum transfer and implementing non-perturbative unitarity bound, the behaviour of the form factors in their whole kinematical range is obtained without introducing any explicit parameterization of their momentum dependence. We consider the four exclusive semileptonic decays and extract from the experimental data for each transition. The average over the four channels is , which is compatible with the latest inclusive determination at level. We address also the issue of Lepton Flavour Universality by computing pure theoretical estimates of the ratios of the branching fractions for each channel, where is a light lepton. In the case of a light spectator quark we obtain and , which are compatible with the corresponding experimental values within . In the case of a strange spectator quark we obtain and . The different values for and may reflect symmetry breaking effects, which seem to be present in some of the lattice form factors, especially at large values of the recoil
LFU ratios in B decays using Lattice QCD and Unitarity
We present the results of the application of the unitarity-based Dispersion
Matrix approach to semileptonic charged-current decays. This method allows
to achieve a non-perturbative and completely model-independent determination of
the hadronic form factors. Starting from lattice results available at large
values of the momentum transfer, the behaviour of the form factors in their
whole kinematical range is obtained without introducing any explicit
parameterization of their momentum dependence. We will focus on the analysis of
Lepton Flavour Universality by computing the ratios of the branching
fractions of the and decays. The
most important result is that, for the first time, the discrepancies between
the SM expectation values and the measurements of the Lepton Flavour
Universality ratios for the decays are reduced at the
1.3 level for each of the two channels, separately.Comment: 8 pages, 3 figures. Contribution to "La Thuile 2022, XXXV Rencontres
de Physique de la Vall\'ee d'Aoste