The vacuum, often perceived as devoid of any matter, teems with a rich tapestry of quantum fluctuations, manifesting as the intriguing phenomenon of vacuum zero-point energy. These ephemeral fluctuations give rise to fleeting particle-antiparticle pairs, existing fleetingly before annihilation. By subjecting the vacuum to intense external fields, these stochastic fluctuations can be stimulated, allowing them to acquire energy from the field and manifest as observable particles. In the realm of relativistic heavy-ion collisions, where the most powerful electromagnetic fields in laboratory settings are generated, the excitation of quantum vacuum fluctuations into real particle-antiparticle pairs becomes feasible, which offers a window into the genesis of matter from nothingness. In this paper, we present the observation of over a hundred pairs of the simplest atomic nucleus-antinucleus pairs, namely proton-antiproton pairs, induced by vacuum excitation via 200 GeV gold-gold collisions conducted at RHIC-STAR. Our findings not only advance our understanding of quantum electrodynamics in the vacuum but also open new avenues for exploring the dynamics of particle production in extreme electromagnetic environments. This work heralds a significant step forward in leveraging high-energy nuclear collisions as a probing tool for studying fundamental aspects of quantum field theory.

Figures:

Figure 1. Fast-moving gold nuclei carry extremely strong electromagnetic fields. The proton-antiproton pairs generated from vacuum quantum fluctuation were separated by the EM fields and flight to the detector.

Figure 2.The nσproton distribution after single track transverse momentum, pseudorapidity and nσelectron cut. The protons are clearly separated from the other particles.

Figure 3. The proton-antiproton pairs pT spectrum for Ultra-Peripheral AuAu collisions at √(sNN)=200 GeV. The error bars are the statistical uncertainties. Significant signal appeared at extremely low pT.

Figure 4. The differential cross sections for exclusively produced proton anti-proton pairs with respect to (a) the invariant mass Mpp̅, (b) the pair transverse momentum pT

Summary:

This measurement of proton-antiproton pairs produced in Au+Au ultra-peripheral collisions is considered to be the first observation of vacuum excitation leading to the production of the simplest atomic nucleus. Our findings not only advance our understanding of quantum electrodynamics in the vacuum but also open new avenues for exploring the dynamics of particle production in extreme electromagnetic environments. This work heralds a significant step forward in leveraging high-energy nuclear collisions as a probing tool for studying fundamental aspects of quantum field theory.