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Characterizing the hadronization of parton showers using the HOMER method
by Benoit Assi, Christian Bierlich, Philip Ilten, Tony Menzo, Stephen Mrenna, Manuel Szewc, Michael K. Wilkinson, Ahmed Youssef, Jure Zupan
Submission summary
| Authors (as registered SciPost users): | Tony Menzo · Stephen Mrenna · Manuel Szewc |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2503.05667v3 (pdf) |
| Date accepted: | Oct. 9, 2025 |
| Date submitted: | Sept. 24, 2025, 9:25 p.m. |
| Submitted by: | Manuel Szewc |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Computational, Phenomenological |
Abstract
We update the HOMER method, a technique to solve a restricted version of the inverse problem of hadronization -- extracting the Lund string fragmentation function $f(z)$ from data using only observable information. Here, we demonstrate its utility by extracting $f(z)$ from synthetic Pythia simulations using high-level observables constructed on an event-by-event basis, such as multiplicities and shape variables. Four cases of increasing complexity are considered, corresponding to $e^+e^-$ collisions at a center-of-mass energy of $90$ GeV producing either a string stretched between a $q$ and $\bar{q}$ containing no gluons; the same string containing one gluon $g$ with fixed kinematics; the same but the gluon has varying kinematics; and the most realistic case, strings with an unrestricted number of gluons that is the end-result of a parton shower. We demonstrate the extraction of $f(z)$ in each case, with the result of only a relatively modest degradation in performance of the HOMER method with the increased complexity of the string system.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
List of changes
- We have fixed the typos pointed out by the reports.
- We have expanded on the definition of exact weights in Section 3.1 and clarified their relationship to the weights detailed in Section 4.4.
- We have added a clarifying sentence regarding the numerical costs of the introduction of a smearing kernel at the end of Section 3.2.2.
- We have clarifited our choice of GBC and MPGNN in Section 4.1.
- We have clarified the assumptions behind the use of Shapley values in Section 4.4.1.
- We have modified multiple figures to increase readability.
- We have added a sentence in the conclusions regarding the need for uncertainty quantification in the determination of the smearing kernel width.
- We have included an additional appendix where we explore a HOMER fit to data generated with two simultaneous parameter variations.
Published as SciPost Phys. 19, 125 (2025)
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