arXiv subjects

Nikolaos Konstantinidis

Publications and source records attributed to Nikolaos Konstantinidis.

3 recordsLinked to original sources

arXiv2026

Distilling Normalizing Flows for Real-Time Anomaly Detection at the LHC

Normalizing flows are principled anomaly detectors, selecting anomalies using a probabilistic per-event likelihood. Extreme latency and resource constraints have prevented the deployment of flow likelihoods within the hardware triggers at the Large Hadron Collider. We bypass these limitations by distilling the likelihood from a large normalizing flow into lightweight student estimators suitable for deployment on a field-programmable gate array. Our use of a conditional normalizing flow enables precise likelihood estimation in the presence of missing input features. Both decision tree and neural network students are considered, the latter optimized under advanced quantization techniques. By simultaneously improving likelihood quality and lowering inference cost, we demonstrate both state-of-the-art physics performance and latency compared with existing flow-based approaches.

hep-ex↗

arXiv2025

DECADE: Decorrelated anomaly detection triggers to enhance the low-mass discovery potential of the LHC

At the ATLAS and CMS experiments at CERN's Large Hadron Collider, the rate of proton-proton collisions far exceeds the rate at which data can be recorded. A real-time event selection process, or "trigger", is needed to ensure that the data recorded contains the highest possible discovery potential. In the absence of hoped-for anomalies that would lead to the discovery of new physics, there is increasing motivation to develop dedicated, model-agnostic, anomaly detection triggers. A common approach is to use unsupervised machine learning (ML) to predict an event-by-event anomaly score, based on the momenta and multiplicity of reconstructed objects. Such anomaly scores often exhibit high correlation with existing trigger observables and thus exhibit a selection bias towards high-momentum anomalies. In this article, we introduce DECorrelated Anomaly DEtection (DECADE), in which quantile regression is applied to the output of a pre-trained anomaly detection algorithm, guaranteeing the independence of the threshold on the anomaly score with respect to primary trigger observables. Thus, DECADE provides efficiency in low-momentum regions of phase space not captured by existing triggers, boosting the trigger efficiency for low-mass phenomena that are inaccessible via primary triggers and current anomaly detection triggers. Quantile regression is implemented using decision tree ensembles, making DECADE highly computationally efficient and therefore optimal for use both in software-based trigger systems and in FPGA-based hardware triggers. In both cases, we demonstrate that DECADE would add an insignificant additional latency and resource cost to the hardware anomaly detection triggers currently in operation at ATLAS and CMS, as well as to those proposed for the High-Luminosity era of the Large Hadron Collider.

hep-ex↗

arXiv2022

Study of Electroweak Phase Transition in Exotic Higgs Decays at the CEPC

A strong first-order electroweak phase transition (EWPT) can be induced by light new physics weakly coupled to the Higgs. This study focuses on a scenario in which the first-order EWPT is driven by a light scalar $s$ with a mass between 15-60 GeV. A search for exotic decays of the Higgs boson into a pair of spin-zero particles, $h \to ss$, where the $s$-boson decays into $b$-quarks promptly is presented. The search is performed in events where the Higgs boson is produced in association with a $Z$ boson, giving rise to a signature of two charged leptons (electrons or muons) and multiple jets from $b$-quark decays. The analysis is considering a scenario of analysing 5000 fb$^{-1}$ $e^+ e^-$ collision data at $\sqrt{s} = 240 $ GeV from the Circular Electron Positron Collider (CEPC). This study with $4b$ final state conclusively tests the expected sensitivity of probing the light scalars in the CEPC experiment. The sensitivity reach is significantly larger than that can be achieved at the LHC.

hep-ex↗