Bayesian Optimization of The Relativistic Heavy Ion Collider Luminosity via s* Control
Abstract
Maximizing luminosity at the interaction point (IP) requires the collision location sIP to coincide with the longitudinal position of the minimum beta function, s. Accurate optics measurements and control of s are therefore essential for luminosity optimization. At the Relativistic Heavy Ion Collider (RHIC), average horizontal beta-beat measurements between operating IPs are approximately 20%, with significant variation in measured s*. Precise control of the beam waist position s is particularly challenging for modern high-energy colliders with short bunch lengths and large crossing angles. We present an online Bayesian optimization (BO) application using the GPTune framework to optimize sPHENIX luminosity through s control at RHIC. GPTune was first validated at the RHIC Electron Beam Ion Source (EBIS), where it achieved up to a 70% increase in beam intensity over the baseline, although experienced operators could reach similar performance with longer manual tuning. The framework was subsequently deployed during sPHENIX operations. Using an intensity-normalized Zero-Degree Calorimeter (ZDC) signal as the optimization objective, due to the unavailability of the live sPHENIX MVTX signal, GPTune identified local luminosity maxima, recovered from intentionally degraded s configurations, and revealed residual horizontal and vertical waist offsets in the interaction region. These results demonstrate the robustness and efficiency of Bayesian optimization for real-time collider tuning under noisy, time-varying conditions. The s control methodology provides a promising tool for precision luminosity optimization and is particularly relevant to next-generation short-bunch colliders such as the Electron-Ion Collider (EIC).
Related
- FCC-μe: High Energy, High Luminosity Muon-Electron Collider & Neutrino Factory at CERN
- Precision luminosity measurement in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the Large Hadron Collider
- LHμC: A high energy, high luminosity muon-hadron collider at CERN
- Precision luminosity measurement in proton-proton collisions at a center-of-mass energy of 13 TeV with the CMS detector at the Large Hadron Collider
- Non-relativistic Cosmological Collider Signals
BibTeX
@misc{gu2026bayesian,
title = {{Bayesian Optimization of The Relativistic Heavy Ion Collider Luminosity via $s^*$ Control}},
author = {Xiaofeng Gu and Benjamin Coe and Guillaume Robert-Demolaize and Takeshi Kanesue and Masahiro Okamura and William Fung and Yue Hao and Ji Qiang and Xiaoye S. Li and Yang Liu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.24978},
eprint = {2609.24978},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24978},
}
RIS
TY - UNPB
TI - Bayesian Optimization of The Relativistic Heavy Ion Collider Luminosity via s^* Control
AU - Xiaofeng Gu
AU - Benjamin Coe
AU - Guillaume Robert-Demolaize
AU - Takeshi Kanesue
AU - Masahiro Okamura
AU - William Fung
AU - Yue Hao
AU - Ji Qiang
AU - Xiaoye S. Li
AU - Yang Liu
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.24978
UR - https://arxiv.org/abs/2609.24978
AB - Maximizing luminosity at the interaction point (IP) requires the collision location s_IP to coincide with the longitudinal position of the minimum beta function, s^. Accurate optics measurements and control of s^ are therefore essential for luminosity optimization. At the Relativistic Heavy Ion Collider (RHIC), average horizontal beta-beat measurements between operating IPs are approximately 20%, with significant variation in measured s^*. Precise control of the beam waist position s^ is particularly challenging for modern high-energy colliders with short bunch lengths and large crossing angles. We present an online Bayesian optimization (BO) application using the GPTune framework to optimize sPHENIX luminosity through s^ control at RHIC. GPTune was first validated at the RHIC Electron Beam Ion Source (EBIS), where it achieved up to a 70% increase in beam intensity over the baseline, although experienced operators could reach similar performance with longer manual tuning. The framework was subsequently deployed during sPHENIX operations. Using an intensity-normalized Zero-Degree Calorimeter (ZDC) signal as the optimization objective, due to the unavailability of the live sPHENIX MVTX signal, GPTune identified local luminosity maxima, recovered from intentionally degraded s^ configurations, and revealed residual horizontal and vertical waist offsets in the interaction region. These results demonstrate the robustness and efficiency of Bayesian optimization for real-time collider tuning under noisy, time-varying conditions. The s^ control methodology provides a promising tool for precision luminosity optimization and is particularly relevant to next-generation short-bunch colliders such as the Electron-Ion Collider (EIC).
ER -