Quantum interference effects enhanced in $\pi^+p$ femtoscopic correlation functions

Abstract

We present a comprehensive analysis of the $\pi^+p$ femtoscopic correlation functions measured by the ALICE Collaboration in high-multiplicity $pp$ collisions at $\sqrt{s}=13$ TeV. Using the Koonin-Pratt formula with a Gaussian source and data-driven $\pi N$ partial-wave amplitudes, we account for the contributions from $\pi^+p$ scattering and $\Delta(1232)^{++}$-decay, thereby successfully reproducing the measured data and their transverse-mass ($m_T$) dependence. The scattering contribution yields a peak near the relative momentum $k\approx140$ MeV/$c$, whereas the decay contribution peaks around $k\approx220$ MeV/$c$. The observed correlation peak results from a weighted sum of the two contributions, with $m_T$-dependent relative weights. We find that the 140 MeV/$c$ peak originates from quantum interference between the incident and scattered waves-a mechanism previously unnoticed in femtoscopic studies. This finding resolves the peak-shift puzzle in $\pi^+p$ correlations and provides a novel perspective for quantum interference effects in femtoscopy.