High-Energy Decays and Weak Quantum Measurements

Abstract

High-energy particle decays naturally realise informationally weak measurements of quantum spin. Decay kinematics act as continuous pointer variables whose overlapping angular distributions encode partial, non-projective information about the parent spin state. Ensemble averages of these pointers yield weak values, linking collider spin-density reconstruction to Aharonov-Vaidman measurement theory. This framework unifies spin tomography, entangled-decay correlations, and spin-correlation algorithms, showing that relativistic decays realise informationally weak measurements of spin and suggesting new ways to probe coherence and interference in high-energy processes.

Figures (1)

• Figure 1: Schematic: decay as a dynamical measurement. The parent spin density matrix $\rho$ couples via helicity amplitudes $f_m(\Omega)$ to decay-field modes. The quantum pointer states $|\Phi_m(\Omega)\rangle = \int {\rm d}\Omega\, f_m(\Omega)\, \ket{\Omega}$ are later amplified by the detector to produce the classical measurement outcome.