We present a generative surrogate for charged-current νμ-nucleus scattering that can be calibrated to measured differential cross sections without event-level experimental samples. Starting from a theoretical interaction model, we fine-tune the surrogate to a MicroBooNE measurement and show that this also improves the description of observables not used in the fit. The calibrated model can also be applied to measurements from different neutrino fluxes without retuning, while retaining event-level predictions of outgoing-muon kinematics. Our results show that experimental cross sections can directly constrain generative event models while preserving their applicability across different observables and beam configurations.
Figures & tables
Figure 1: Training scheme: (a) The σ -DNN and GAN are pretrained on NuWro. (b) Fine-tuning alternates adversarial regularization using the data-informed reservoir with a differentiable full-covariance fit to the forward-smeared MicroBooNE measurement. The latter updates G and the σ -DNN.
χv2 /n
χc2 /n
σ -DNN B , GAN B
461.7/138
460.3/138
σ -DNN B , GAN T
435.6/138
268.4/138
σ -DNN T , GAN B
152.0/138
500.1/138
σ -DNN T , GAN T
110.5/138
220.3/138
Table 1: The values of χv2 and χc2 over the number of bins (n) for four configurations of the models: base (subscript B) and fine-tuned (subscript T) σ -DNN and GAN models. Computed for samples of 1 million events.
Figure 2: Base and tuned models compared with the MicroBooNE double-differential cross-section measurement [ 23 ] for various Eν ranges. Grey vertical dashed lines separate different Eν regions, from left to right: [0.2,0.705] , [0.705,1.05] , [1.05,1.57] , and [1.57,4] GeV.
Figure 3: Event distribution at Eν=3 GeV generated by the fine-tuned GAN with and without the reservoir sub-step.
Figure 4: Base and fine-tuned models compared to the MicroBooNE measurement [ 24 ] : σ/⟨Eν⟩ (left), dσ/dEμ (center) and dσ/dEhad (right).
Figure 5: Base model, tuned model, and the MicroBooNE data [ 25 , 26 ] for dσ/dcosθ , not used in the training.
Figure 6: Base model, tuned model, and ArgoNeuT data [ 27 , 28 ] for dσ/dpμ distribution. The shaded area shows the pμ range of the training MicroBooNE data.
Figure S1: Training scheme. (a) The σ -DNN and the conditional GAN ( G , D ) are first trained on NuWro. (b) Fine-tuning combines (1) adversarial regularization using the data-informed reservoir and (2) a differentiable full-covariance fit in the measurement space. The discriminator is updated on every reservoir batch, while every fifth discriminator update is followed by an adversarial update of G and by the χc2 update of G and the σ -DNN. Sampling of Eν from Φσ^ carries no gradient.
Figure S2: Cross section predicted by NuWro and by the base neural network. Predictions were made on the energies sampled for training ( NuWro ) and points in the middle of the energies of the tables (DNN).
Figure S3: The output of each block of G and D is used as an input to all subsequent blocks; all inputs to a block are averaged before it is processed.
Figure S4: One-million-event reservoir used to fine-tune the GAN. The reservoir is constructed by resampling truth-level NuWro events according to flux-weighted target occupancies inferred from the MicroBooNE measurement. The visible bin structures reflect the experimental binning.
Figure S5: Left: A representation of a flux Φ bin of width ΔEν divided into sub-bins of flux Φ′ of width ΔEν′ . Right: Measurement bins of width ΔEν,ω′′ that may contain several Φ bins or fractions, but always entire Φ′ bins.
Figure S6: Left: double differential cross section as a function of Eν from the base DNN models, using exact event counts to create histograms, and the result using the differentiable histogram approximation, with a batch of 4000 events. Right: same data as left, but smeared with the matrix Ac .
Figure S7: Base and tuned models compared with MicroBooNE two-dimensional differential cross-section data in Eν Bins [ 23 ] on the left, and the (MC − Data) / Unc ratio on the right. The black plot in the ratio figure shows Data −∣ Data ∣ to highlight the negative cross-section values found in the experimental measurement, and the gray bands show the measurement uncertainties. Grey vertical dashed lines show the different Eν regions.
σ(Eν)
dσ/dEμ
dσ/dEhad
χc2 /n
χv2 /n
χc2 /n
χv2 /n
χc2 /n
χv2 /n
Base
58.1/10
54.2/10
29.1/11
69.1/11
17.1/8
41.3/8
Tuned
44.2/10
0.5/10
12.7/11
6.4/11
4.4/8
6.0/8
Table S1: χc2 and χv2 over the number of bins of the base and tuned DNN models for σ(Eν) , dσ/dEμ , and dσ/dEhad .
Figure S8: Base model, tuned model, and MicroBooNE data [ 25 , 26 ] for d2σ/dEμdcosθ (left) and dσ/dcosθ (right).
d2σ/dEμdcosθ
dσ/dcosθ
χc2 /n
χv2 /n
χc2 /n
χv2 /n
Base
257.0/69
554.7/69
291.5/17
2991.7/17
Tuned
109.2/69
87.9/69
6.8/17
4.8/17
Table S2: Same as Table S1 but for d2σ/dEμdcosθ and dσ/dcosθ .
Figure S9: Base model, tuned model, and ArgoNeuT data [ 27 , 28 ] . Left: dσ/dθ . Right: dσ/dpμ . Results for neutrinos in the NuMI neutrino beam. The shaded areas on the right-side plot show the pμ range of the training MicroBooNE data.
χv2 /n
dσ/dθ
dσ/dpμ
Base
13.2/14
6.1/11
Tuned
11.4/14
6.0/11
Table S3: Comparison of MicroBooNE-tuned DNN to ArgoNeuT measurement of muon neutrino νμ on NuMI neutrino beam.
χv2 /n
dσ/dθ
dσ/dpμ
Base
9.1/18
9.6/20
Tuned
9.6/18
9.1/20
Table S4: Comparison of MicroBooNE-tuned DNN to ArgoNeuT measurement of muon neutrino νμ on NuMI anti-neutrino νˉμ beam.
Figure S10: Base model, tuned model, and ArgoNeuT data [ 27 , 28 ] . Left: dσ/dθ . Right: dσ/dpμ . Results for neutrinos on the NuMI antineutrino beam. The shaded areas on the right-side plots show the pμ range of the training MicroBooNE data.
To enable an accurate determination of oscillation parameters, accelerator-based neutrino experiments require detailed simulations of nuclear interaction physics in the GeV regime. While substantial effort from both theory and experiment is currently being invested to improve the fidelity of these simulations, their present deficiencies typically oblige experimental collaborations to resort to empirical tuning of simulation model parameters. As the precision requirements of the field continue to become more stringent, machine learning techniques may provide a powerful means of handling corresponding growth in the complexity of future neutrino interaction model tuning exercises. To study the suitability of simulation-based inference (SBI) for this physics application, in this paper we revisit a tuned configuration of the GENIE neutrino event generator that was originally developed by the MicroBooNE collaboration. Despite closely reproducing the adopted values of four physics parameters when confronted with the tuned cross-section predictions as input, we find that our trained SBI algorithm prefers modestly different values (within MicroBooNE's assigned uncertainties) and achieves slightly better goodness-of-fit when inference is run on the experimental data set originally used by MicroBooNE. We also find that our trained algorithm can create a fair approximation of an alternative neutrino scattering simulation, NuWro, that shares only a subset of its physics model parameters with GENIE.
Karla Tame-Narvaez, Steven Gardiner, Aleksandra Ćiprijanović +1
Fermi National Accelerator Laboratory, Batavia, Illinois 60510 USA · Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 · NSF-Simons AI Institute for the Sky (SkAI), 172 E. Chestnut St., Chicago, IL 60611
High-precision calorimeter simulation at current and future colliders imposes rapidly growing computational demands, motivating the development of machine-learning surrogates for traditional Monte Carlo tools such as Geant4. Flow matching and diffusion-based generative models have become leading approaches for high-dimensional fast simulation because of their sample quality, but typically require O(100) function evaluations at inference and often rely on auxiliary networks to constrain global observables, compromising streamlined end-to-end generation. We introduce a unified framework that improves the balance between speed, shower quality, and physics fidelity. The method combines: (i) an average velocity field integrator that enables sampling in one or a few evaluations; (ii) a learned generative prior in shower space, constructed from data rather than random noise; and (iii) physics-guided loss terms that impose inductive biases on key observables during training. These elements are training time regularizers, preserving end-to-end inference with no additional cost. With only one or a few evaluation steps, the model achieves shower quality competitive with state-of-the-art flow and diffusion approaches, tested on several public high granularity calorimeter datasets. The results demonstrate inter-layer shower structure consistent with the underlying physics, providing a strong candidate for future fast simulation workflows.
Cheng Jiang, Sitian Qian, Kevin Pedro +3
School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom · Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA · Fermi National Accelerator Laboratory, Batavia, IL 60510, USA +2
Beam-induced background (BIB) from muon decay products will be an overwhelming and unavoidable background at a future Muon Collider. In order to develop robust event reconstruction algorithms, we need large amounts of accurate BIB simulation to test on. BIB simulation is currently compute-limited: the simulated sample presently used for BIB overlay, which statistically represents approximately 10% of a single unique event's worth of simulated BIB, requires on the order of 106 HS23⋅hours to generate and occupies approximately 100 GB on disk. In this work, we develop the first machine learning models for fast BIB generation in tracking detectors. We consider two classes of architectures: a slower but higher-fidelity tabular diffusion model, and a faster but lower fidelity circular spline flow model. We find that both classes of architectures produce BIB hits and tracks that closely resemble those of available full simulation hits and tracks, and that the machine learning models can produce BIB in over an order of magnitude less time than what is needed to produce full simulation BIB. We release the model weights with the paper so that the Muon Collider community can use these fast BIB hits for future R&D.
Radha Mastandrea, Shiyu Peng, Benjamin Rosser +1
Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637, USA · Data Science Institute, The University of Chicago, Chicago, IL 60637, USA · Department of Physics, Brown University, Providence, RI 02912, USA +1