SHiP as a (post-)discovery machine: identifying the diphoton signals' origin
Abstract
The upcoming SHiP experiment may probe interaction strengths of decaying feebly coupled particles several orders of magnitude below existing limits. In the event of a discovery, it may also reveal the nature of the new particle. This requires identifying its exact production mechanism, which SHiP does not observe directly. We explore whether this mechanism can be inferred from the kinematics of its visible decays. As a benchmark, we consider an axion-like particle (ALP) with a dominant diphoton decay, which may occur for couplings to the U(1)Y and SU(2)L gauge fields. For a known ALP mass, the observed energy and angular distributions depend on the relative magnitude and sign of the couplings and on the unknown lifetime, which we profile independently under each hypothesis. We first determine how the ALP energy and its longitudinal and transverse decay positions distinguish the interactions, assuming perfect reconstruction and accounting for production, propagation, decay, and geometric acceptance. We then include the detector response and reconstruct the diphoton decays using a full simulation of the SHiP electromagnetic calorimeter. Only $2−−4$ reconstructed diphoton events are needed to distinguish the two pure U(1)Y and SU(2)L interactions for ALP masses between $0.2$ and 1 GeV. For coupling admixtures, the study assuming perfect reconstruction indicates requirements of several tens to 𝒪(102) events in favorable regions.
Related
- Transformer-based machine learning using low-level calorimeter signals for collimated photon identification at collider experiments
- From Heuristics to Machine Learning: The Performance Ceiling for Single-Ion Magnets and Its Electronic Origin
- A measurement of the Higgs boson mass in the diphoton decay channel in proton-proton collisions at s=13TeV
- A measurement of the Higgs boson mass in the diphoton decay channel in proton-proton collisions at √s = 13 TeV
- Vertexing displaced diphoton decays with recoil photons at Belle II
BibTeX
@misc{climescu2026ship,
title = {{SHiP as a (post-)discovery machine: identifying the diphoton signals' origin}},
author = {Matei Climescu and Malte Fogde Mikkelsen and Maksym Ovchynnikov},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19269},
eprint = {2609.19269},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19269},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - SHiP as a (post-)discovery machine: identifying the diphoton signals' origin
AU - Matei Climescu
AU - Malte Fogde Mikkelsen
AU - Maksym Ovchynnikov
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.19269
UR - https://arxiv.org/abs/2609.19269
AB - The upcoming SHiP experiment may probe interaction strengths of decaying feebly coupled particles several orders of magnitude below existing limits. In the event of a discovery, it may also reveal the nature of the new particle. This requires identifying its exact production mechanism, which SHiP does not observe directly. We explore whether this mechanism can be inferred from the kinematics of its visible decays. As a benchmark, we consider an axion-like particle (ALP) with a dominant diphoton decay, which may occur for couplings to the U(1)_Y and SU(2)_L gauge fields. For a known ALP mass, the observed energy and angular distributions depend on the relative magnitude and sign of the couplings and on the unknown lifetime, which we profile independently under each hypothesis. We first determine how the ALP energy and its longitudinal and transverse decay positions distinguish the interactions, assuming perfect reconstruction and accounting for production, propagation, decay, and geometric acceptance. We then include the detector response and reconstruct the diphoton decays using a full simulation of the SHiP electromagnetic calorimeter. Only $2−−4$ reconstructed diphoton events are needed to distinguish the two pure U(1)_Y and SU(2)_L interactions for ALP masses between $0.2$ and 1 GeV. For coupling admixtures, the study assuming perfect reconstruction indicates requirements of several tens to 𝒪(10^2) events in favorable regions.
ER -