Tagging more quark jet flavours at FCC-ee at 91 GeV with a transformer-based neural network

Blekman, Freya; De Moor, Alexandre; Gautam, Kunal; Ilg, Armin; Macchiolo, Anna; Canelli, Florencia; Ploerer, Eduardo

Preprint

PUBDB-2024-07333

Tagging more quark jet flavours at FCC-ee at 91 GeV with a transformer-based neural network

Blekman, F.Extern*DESY* ; Canelli, F. ; De Moor, A. ; Gautam, K. (Corresponding author)Extern* ; Ilg, A. ; Macchiolo, A. ; Ploerer, E.

2024

[10.3204/PUBDB-2024-07333]

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Please use a persistent id in citations: doi:10.3204/PUBDB-2024-07333

Report No.: DESY-24-086; arXiv:2406.08590

Abstract: Jet flavour tagging is crucial in experimental high-energy physics. A tagging algorithm, DeepJetTransformer, is presented, which exploits a transformer-based neural network that is substantially faster to train. The DeepJetTransformer network uses information from particle flow-style objects and secondary vertex reconstruction as is standard for $b$- and $c$-jet identification supplemented by additional information, such as reconstructed V$^0$s and $K^{\pm}/\pi^{\pm}$ discrimination, typically not included in tagging algorithms at the LHC. The model is trained as a multiclassifier to identify all quark flavours separately and performs excellently in identifying $b$- and $c$-jets. An $s$-tagging efficiency of $40\%$ can be achieved with a $10\%$$ud$-jet background efficiency. The impact of including V$^0$s and $K^{\pm}/\pi^{\pm}$ discrimination is presented. The network is applied on exclusive $Z \to q\bar{q}$ samples to examine the physics potential and is shown to isolate $Z \to s\bar{s}$ events. Assuming all other backgrounds can be efficiently rejected, a $5\sigma$ discovery significance for $Z \to s\bar{s}$ can be achieved with an integrated luminosity of $60~\text{nb}^{-1}$, corresponding to less than a second of the FCC-ee run plan at the $Z$ resonance.

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