Neutrino direct simulation Monte Carlo (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ν</mi><mi>DSMC</mi></math>) is a Monte Carlo method for solving the neutrino Boltzmann equation in the early Universe, designed to track the evolution of cosmic neutrinos across a wide range of cosmological scenarios. We develop a complete <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ν</mi><mi>DSMC</mi></math> solver that consistently incorporates the effects of the electron mass, three-flavor neutrino oscillations, and finite-temperature QED corrections to the thermodynamics of the electromagnetic plasma. As a first application, we perform a high-precision calculation of neutrino decoupling in the standard cosmological model and obtain <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>eff</mi></msub><mo>=</mo><mn>3.0439</mn><mo>±</mo><mn>0.0006</mn></math>, in excellent agreement with state-of-the-art results.

Ukraine

Oleksii Ihnatenko

CERN

Maksym Ovchynnikov

Precision calculation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>eff</mi></msub></math> with neutrino direct simulation Monte Carlo

The IKKT model (or the type IIB matrix model) has been investigated as a promising nonperturbative formulation of superstring theory. One of the recent developments concerning this model is the discovery of the dual supergravity solution corresponding to the model obtained after supersymmetry-preserving mass deformation, which is dubbed the polarized IKKT model. Here we perform Monte Carlo simulations of this model in the case of matrix size <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>N</mi><mo>=</mo><mn>2</mn></mrow></math> for a wide range of the deformation parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Ω</mi></mrow></math>. While we reproduce precisely the known result for the partition function obtained by the localization method developed for supersymmetric theories, we also calculate the observables, which were not accessible by the previous work, in order to probe the spacetime structure emergent from the dominant matrix configurations. In particular, we find that the saddle point corresponding to the original IKKT model is smoothly connected to the saddle represented by the fuzzy sphere dominant at large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Ω</mi></mrow></math>, whereas the dominant configurations become diverging commuting matrices at small <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Ω</mi></mrow></math>.

Japan

Chien-Yu Chou

Jun Nishimura

Cheng-Tsung Wang

Monte Carlo Studies of the Emergent Spacetime in the Polarized Type IIB Matrix Model

Lattice Monte Carlo simulations and the functional renormalization group (RG) are powerful approaches that allow for quantitative studies of nonperturbative phenomena such as bound-state formation, spontaneous symmetry breaking, and phase transitions. While results from both methods have recently shown remarkable agreement for many observables, e.g., in quantum chromodynamics, an analysis of deviations in certain quantities turns out to be challenging. This is because calculations with the two methods are based on different approximations, regularizations, and scale fixing procedures. In the present work, we present a framework for a more direct comparison by formulating the functional RG approach on a finite spacetime lattice. This removes all ambiguities of regularization, finite-size, and scale fixing procedures in concrete studies. By investigating the emergence of spontaneous symmetry breaking and phase transitions in a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math> scalar theory in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi><mo>=</mo><mn>1</mn></math>, 2, and 3 spacetime dimensions, we demonstrate at the example of the local potential approximation how this framework can be used to evaluate and compare the systematic errors of both approaches.

Germany

Niklas Zorbach

Jan Philipp Klinger

Owe Philipsen

Jens Braun

Lattice Monte Carlo meets the lattice functional renormalization group: A quantitative comparison

The LHCb collaboration amplitude analysis of the decays <math altimg='si32.svg'><mrow><msup><mi>B</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>D</mi><mo>+</mo></msup><msup><mi>D</mi><mo>&#8722;</mo></msup><msup><mi>K</mi><mo>+</mo></msup></mrow></math>, <math altimg='si33.svg'><mrow><msup><mi>B</mi><mo>+</mo></msup><mo>&#8594;</mo><msup><mi>D</mi><mo>&#8722;</mo></msup><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><msup><mi>&#960;</mi><mo>+</mo></msup></mrow></math>, and <math altimg='si34.svg'><mrow><msup><mi>B</mi><mn>0</mn></msup><mo>&#8594;</mo><msup><mover accent='true'><mi>D</mi><mo>&#175;</mo></mover><mn>0</mn></msup><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><msup><mi>&#960;</mi><mo>&#8722;</mo></msup></mrow></math> suggested the existence of two new resonant <math altimg='si35.svg'><mrow><msup><mi>J</mi><mi>P</mi></msup><mo linebreak='goodbreak'>=</mo><msup><mn>0</mn><mo>+</mo></msup></mrow></math> states with minimum quark content <math altimg='si21.svg'><mrow><mover accent='true'><mi>u</mi><mo>&#175;</mo></mover><mover accent='true'><mi>d</mi><mo>&#175;</mo></mover><mi>s</mi><mi>c</mi></mrow></math> and <math altimg='si23.svg'><mrow><mover accent='true'><mi>s</mi><mo>&#175;</mo></mover><mover accent='true'><mi>u</mi><mo>&#175;</mo></mover><mi>d</mi><mi>c</mi></mrow></math>/ <math altimg='si24.svg'><mrow><mover accent='true'><mi>s</mi><mo>&#175;</mo></mover><mover accent='true'><mi>d</mi><mo>&#175;</mo></mover><mi>u</mi><mi>c</mi></mrow></math>, named <math altimg='si1.svg'><msub><mi>T</mi><mrow><mi>c</mi><mi>s</mi><mn>0</mn></mrow></msub></math> and <math altimg='si2.svg'><msub><mi>T</mi><mrow><mi>c</mi><mover accent='true'><mi>s</mi><mo>&#175;</mo></mover><mn>0</mn></mrow></msub></math>, respectively. In this work, we used the diffusion Monte Carlo (DMC) method to compute the masses of those tetraquarks within the framework of the constituent quark model. We describe the systems as compact structures, not as diquark/antidiquark or meson/meson arrangements. In this context, compact means that we used directly the eigenvectors of the spin, color and flavor operators without any splitting and/or (re)combination of smaller units. This allows us to deduce the existence of two distinct bound configurations for each composition, corresponding to ground and excited flavor states. In both cases, the excited flavor states are the ones with masses comparable to the ones observed by LHCb. In addition, our analysis allows us to assign unambiguously an isospin value of <math altimg='si20.svg'><mi>I</mi></math>=1 to the experimentally obtained <math altimg='si1.svg'><msub><mi>T</mi><mrow><mi>c</mi><mi>s</mi><mn>0</mn></mrow></msub></math> tetraquark.

Spain

M.C. Gordillo

J. Segovia

Diffusion Monte Carlo calculation of compact <math altimg='si1.svg'><msub><mi>T</mi><mrow><mi>c</mi><mi>s</mi><mn>0</mn></mrow></msub></math> and <math altimg='si2.svg'><msub><mi>T</mi><mrow><mi>c</mi><mover accent='true'><mi>s</mi><mo>&#175;</mo></mover><mn>0</mn></mrow></msub></math> tetraquarks

Building on the idea of numerically integrating differential equations satisfied by Feynman integrals, we propose a novel strategy for handling branch cuts within a numerical framework. We develop an integrator capable of evaluating a basis of integrals in both double and quadruple precision, achieving significantly reduced computational times compared to existing tools. We demonstrate the performance of our integrator by evaluating one- and two-loop five-point Feynman integrals with up to nine complex kinematic scales. In particular, we apply our method to the radiative return process of massive electron-positron annihilation into pions plus an energetic photon within scalar QED, for which we also build the differential equation, and extend it to the case where virtual photons acquire an auxiliary complex mass under the Generalised Vector-Meson Dominance model. Furthermore, we validate our approach on two integral families relevant for the two-loop production of $$ t\overline{t} $$ + jet. The integrator achieves, in double precision, execution times of the order of milliseconds for one-loop topologies and hundreds of milliseconds for the two-loop families, enabling for on-the-fly computation of Feynman integrals in Monte Carlo generators and a more efficient generation of grids for the topologies with prohibitive computational costs.

United Kingdom

Pau Petit Rosàs

William Torres Bobadilla

Fast evaluation of Feynman integrals for Monte Carlo generators

The neutrino energy reconstruction is crucial for reducing systematic uncertainties in neutrino oscillation experiments and improving cross section measurements. Kaon-decays-at-rest (KDAR) neutrinos provide a unique opportunity to probe neutrino-nucleus interactions at low energies with a precisely known energy of 235.5 MeV. This work presents Monte Carlo predictions of missing energy due to nuclear effects in the KDAR <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ν</mi><mi>μ</mi></msub></math> charged-current scattering on the carbon nucleus for the J-PARC sterile neutrino search at the J-PARC Spallation Neutron Source. The predictions from genie, nuwro, and gibuu show a significant impact of nuclear and final-state interaction (FSI) models, as well as nucleon removal energy, on missing energy reconstruction. Tuning the hA FSI model improves the predictions from genie. It is also observed that the nucleon elastic component of FSI leads to better predictions in nuwro compared to genie. nuwro shows the best agreement with data among the generators considered; however, the observed discrepancies with data across all generators highlight the limitations of current theoretical descriptions in the low-energy regime and the need for improvements in Monte Carlo modeling.

India

R.K. Pradhan

Israel

R. Lalnuntluanga

A. Giri

Monte Carlo study of KDAR <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ν</mi><mi>μ</mi></msub></math> charged-current scattering on carbon

Sweden

Ludwig Neste

Pascal Gutjahr

United States

Mirco Hünnefeld

Jean-Marco Alameddine

Wolfgang Rhode

Julia Becker Tjus

Felix Riehn

Kevin Kröninger

Johannes Albrecht

Erratum: Prompt and conventional high-energy muon spectra from a full Monte Carlo simulation via CORSIKA7

We develop an extended framework for the hybrid Monte Carlo (HMC) algorithm in lattice gauge theory by embedding the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></math> group into the space of general complex matrices, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>M</mi><mi>N</mi></msub><mo stretchy="false">(</mo><mi mathvariant="double-struck">C</mi><mo stretchy="false">)</mo></math>. Auxiliary directions will be completely factorized in the path integral, and the embedding does not alter the expectation values of the original theory. We perform the molecular dynamics updates by using the matrix elements of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi><mo>∈</mo><msub><mi>M</mi><mi>N</mi></msub><mo stretchy="false">(</mo><mi mathvariant="double-struck">C</mi><mo stretchy="false">)</mo></math> as the dynamical variables without group theoretic constraints. The framework enables us to introduce nonseparable Hamiltonians for the HMC in lattice gauge theory exactly, whose immediate application includes the Riemannian manifold HMC.

Norman H. Christ

Lu-Chang Jin

Christoph Lehner

Erik Lundstrum

Nobuyuki Matsumoto

Extended framework for the hybrid Monte Carlo in lattice gauge theory

We apply the variational Monte Carlo method based on neural network quantum states, using a neural autoregressive flow architecture as our ansatz, to determine the ground state wave function of the bosonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>SU</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></mrow></math> Yang-Mills-type two-matrix model at strong coupling. Previous literature hinted at the inaccuracy of such an approach at strong coupling. In this work, the accuracy of the results is tested using lattice Monte Carlo simulations: we benchmark the expectation value of the energy of the ground state for system sizes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> that are beyond brute-force exact diagonalization methods. We observe that the variational method with neural network states reproduces the right ground state energy when the width of the network employed in this work is sufficiently large. We confirm that the correct result is obtained for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo>=</mo><mn>2</mn></math> and 3, while obtaining a precise value for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo>=</mo><mn>4</mn></math> requires more resources than the amount available for this work.

Norbert Bodendorfer

Türkiye

Onur Oktay

Vaibhav Gautam

Masanori Hanada

Enrico Rinaldi

Variational Monte Carlo with neural network quantum states for a Yang-Mills matrix model

In this article, we probe the trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating (RPV) supersymmetric (SUSY) scenarios with specific nonzero interactions in the light of neutrino oscillation, Higgs, and flavor observables. We attempt to fit the set of observables using a state-of-the-art Markov Chain Monte Carlo (MCMC) setup and study its impact on the model parameter space. Our main objective is to constrain the trilinear couplings individually, along with some other SUSY parameters relevant to the observables. We present the constrained parameter regions in the form of marginalized posterior distributions on different two-dimensional parameter planes. We perform our analyses with two different scenarios characterized by our choices for the lightest SUSY particle (LSP), bino, and stop. Our results indicate that the lepton number violating trilinear couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mi>i</mi><mn>33</mn></mrow></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><mo>=</mo><mn>1</mn></math>, 2) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>λ</mi><mrow><mi>j</mi><mn>33</mn></mrow><mo>′</mo></msubsup></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>j</mi><mo>=</mo><mn>1</mn></math>, 2, 3) can be at most of the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> or even smaller while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>tan</mi><mi>β</mi></math> is restricted to below 15 even when <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> allowed regions are considered. We further comment on the possible LHC signatures of these LSPs focusing on and around the best-fit regions.

Arghya Choudhury

Sourav Mitra

Arpita Mondal

Subhadeep Mondal

Markov chain Monte Carlo analysis to probe trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating SUSY scenarios and possible LHC signatures