Abstract
"Title: Development of MIDDLE, a novel method for the identification of the decays of heavy flavour hadrons to muons, to measure the fragmentation properties of the b-quark and the mass of the top quark. Description: The MIDDLE project aims to develop a novel Deep Learning–based method for identifying muons originating from the semileptonic decays of heavy-flavour hadrons (b- and c-hadrons) within hadronic jets. By exploiting detailed detector information—such as impact parameters, track quality, calorimetric deposits, and isolation profiles—MIDDLE will achieve superior background rejection compared to existing Boosted Decision-Tree approaches, while maintaining minimal bias from jet kinematics. The tool will be implemented within the ATLAS software framework and optimized for both Run-2 (√s=13 TeV) and Run-3 (√s=13.6 TeV) datasets, leveraging approximately 250 fb⁻¹ of LHC data for final measurements" The MIDDLE project is designed to revolutionize heavy-flavour muon identification by developing a state-of-the-art deep-learning classifier that dramatically improves signal purity and background rejection in hadronic jets using detailed inner-detector and calorimeter information . Building on this foundation, the MIDDLETOP extension will precisely reconstruct top-quark decay chains—distinguishing muons from b→μX, b→c→μX, and c→μX processes—and exploit charge and angular correlations to further enhance classification performance . Taking advantade from these advanced tagging tools, the project will deliver the first measurement of b-quark fragmentation observables in tt¯ events at the LHC, providing critical benchmarks for theoretical models and Monte Carlo generators. Finally, by combining superior muon-tag purity with robust top-reconstruction techniques, MIDDLE/MIDDLETOP aims to achieve a top-quark mass determination with an uncertainty below 500 MeV—setting a new standard for precision in direct mₜ measurements. MIDDLE and MIDDLETOP will be delivered as fully calibrated, publicly documented tools within ATLAS, each culminating in a high-impact publication. WP1/2 papers will describe the algorithms and their performance, while WP3/4 will present world-first measurements of b-quark fragmentation in tt¯ events and the most precise single direct top-mass determination. Beyond these flagship analyses, the tools are poised to enhance W/Z+HF cross-section measurements, improve boosted top/Higgs tagging by incorporating leptonic inputs, and support searches for new physics—thereby offering a versatile resource for the particle-physics community well beyond the project’s 24-month lifespan.
Dettagli del progetto
Responsabile scientifico: Matteo Franchini
Strutture Unibo coinvolte:
Dipartimento di Fisica e Astronomia "Augusto Righi"
Coordinatore:
INFN-Istituto Nazionale di Fisica Nucleare(Italy)
Contributo totale Unibo: Euro (EUR) 57.728,00
Durata del progetto in mesi: 24
Data di inizio
28/09/2023
Data di fine:
28/02/2026
