Response Matrix Estimation in Unfolding Differential Cross Sections

Fuente: arXiv
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Hauptverfasser: Zhu, Huanbiao, Marini, Andrea Carlo, Kuusela, Mikael, Wasserman, Larry
Format: Preprint
Veröffentlicht: 2025
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author Zhu, Huanbiao
Marini, Andrea Carlo
Kuusela, Mikael
Wasserman, Larry
author_facet Zhu, Huanbiao
Marini, Andrea Carlo
Kuusela, Mikael
Wasserman, Larry
contents The unfolding problem in particle physics is to make inferences about the true particle spectrum based on smeared observations from a detector. This is an ill-posed inverse problem, where small changes in the smeared distribution can lead to large fluctuations in the unfolded distribution. The forward operator is the response matrix which models the detector response. In practice, the forward operator is rarely known analytically and is instead estimated using Monte Carlo simulation. This raises the question of how to best estimate the response matrix and what impact this estimation has on the unfolded solutions. In most analyses at the LHC, response matrix estimation is done by binning the true and smeared events and counting the propagation of events between the bins. However, this approach can result in a noisy estimate of the response matrix, especially with a small Monte Carlo sample size. Unexpectedly, we also find that the noise in the estimated response matrix can inadvertently regularize the problem. As an alternative, we propose to estimate the response matrix through the use of conditional density estimation of the response kernel in the unbinned setting followed by binning this estimator. Using simulation studies, we investigate the performance of the two approaches.
format Preprint
id arxiv_https___arxiv_org_abs_2509_00892
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Response Matrix Estimation in Unfolding Differential Cross Sections
Zhu, Huanbiao
Marini, Andrea Carlo
Kuusela, Mikael
Wasserman, Larry
High Energy Physics - Experiment
The unfolding problem in particle physics is to make inferences about the true particle spectrum based on smeared observations from a detector. This is an ill-posed inverse problem, where small changes in the smeared distribution can lead to large fluctuations in the unfolded distribution. The forward operator is the response matrix which models the detector response. In practice, the forward operator is rarely known analytically and is instead estimated using Monte Carlo simulation. This raises the question of how to best estimate the response matrix and what impact this estimation has on the unfolded solutions. In most analyses at the LHC, response matrix estimation is done by binning the true and smeared events and counting the propagation of events between the bins. However, this approach can result in a noisy estimate of the response matrix, especially with a small Monte Carlo sample size. Unexpectedly, we also find that the noise in the estimated response matrix can inadvertently regularize the problem. As an alternative, we propose to estimate the response matrix through the use of conditional density estimation of the response kernel in the unbinned setting followed by binning this estimator. Using simulation studies, we investigate the performance of the two approaches.
title Response Matrix Estimation in Unfolding Differential Cross Sections
topic High Energy Physics - Experiment
url https://arxiv.org/abs/2509.00892