arXiv subjects

Valentin Durupt

Publications and source records attributed to Valentin Durupt.

3 recordsLinked to original sources

arXiv2026

MadSpin2: automated spin-entangled decays of heavy resonances via the spin-density matrix formalism

The simulation of processes that contain multiple particles from the decay of unstable resonances becomes computationally challenging both at leading order and beyond. This paper presents MADSPIN2, a new version of MADSPIN, a dedicated tool tackling this problem, primarily for events generated with the MG5AMC event generator. While still based on the Frixione-Laenen-Motylinski-Webber formalism, the new version leverages spin-density matrices to lift most of the limitations of the previous implementation. It supports loop-induced processes, N -body decays and samples defined by amplitude-level interference between distinct hard-process amplitudes. It also introduces the multiple-pole approximation and a resonance-helicity decomposition, including off-diagonal helicity-interference contributions. These developments substantially broaden the phenomenological scope of MADSPIN, enabling applications that were previously inaccessible within the framework, several of which are demonstrated in this work.

hep-ph↗

arXiv2026

Experimental prospects for quantum decoherence measurements at colliders

We study the impact of radiation on quantum systems defined by the spins of elementary fermion-antifermion pairs produced at colliders. We present predictions for several processes, showing that energetic final-state radiation can induce decoherence and significantly reduce the entanglement of quantum systems formed by elementary fermion pairs. We investigate the feasibility of observing this effect experimentally in exclusive samples with energetic radiation. A statistically significant signal can be obtained with current data in associated $pp \rightarrow t\bar{t}(g)$ production at the LHC and in $e^+e^- \rightarrow \tau^{+}\tau^{-}(\gamma)$ production at Belle 2. Future electron-positron colliders operated at the $Z$ pole or well above the $t\bar{t}$ production threshold will extend these prospects further.

hep-ph↗

arXiv2025

Automated computation of spin-density matrices and quantum observables for collider physics

We present a fully automated framework to compute production spin-density matrices for generic collider processes at tree level within \textsc{MadGraph5\_aMC@NLO}. The method assembles helicity amplitudes into event-by-event production matrices. These are written to the LHE file in a compact form, together with run metadata, enabling direct post-processing of quantum observables. The implementation supports bi- and multipartite qubit and qutrit final states, configurable reference frames, and both polarised and unpolarised initial states. A companion, easy-to-extend library provides analysis routines to determine key quantum-information measures and witnesses. These include purity, concurrence, and entanglement of formation for qubits; Peres--Horodecki tests and negativity; spin-polarisation vectors and correlation matrices; $D$-coefficients; and stabiliser-based ``magic'' measures. As a result, multi-particle quantum correlations can be quantified systematically. We validate the implementation against known results for $t\bar t$ and $VV$ ($V=W^\pm,Z$) production in $pp$ and $e^+e^-$ collisions and in heavy-resonance decays. We then consider new applications and study quantum correlations in several LHC final states: $t\bar t W^\pm$, $tW^-$ vs.\ $t(\bar t\to W^- \bar b)$, and $t\bar t t$ vs. $t\bar t t\bar t$.

hep-ph↗