Double-slit experiment at Fermi scale: Coherent photoproduction in heavy-ion collisions

The double-slit experiment has become a classic thought experiment for its clarity in expressing the central puzzle of quantum mechanics—wave-particle complementarity. Such wave-particle duality continues to be challenged and investigated in a broad range of entities with electrons, neutrons, helium atoms, ${\mathrm{C}}_{60}$ fullerenes, Bose-Einstein condensates, and biological molecules. In this Rapid Communication, we present a double-slit scenario at Fermi scale with new entities—coherent photon products in heavy-ion collisions. Virtual photons from the electromagnetic fields of relativistic heavy ions can fluctuate to quark-antiquark pairs, scatter off a target nucleus, and emerge as vector mesons. The two colliding nuclei can take turns to act as targets, forming a double-slit interference pattern. Furthermore, the “which-way” information can be partially solved using sufficiently-high multiplicity heavy-ion collisions so that the reaction plane can be determined, which demonstrates the complementary principle, a key concept of quantum mechanics.

Figure 1

Amplitude and momentum distribution patterns of coherent $J/\psi$ photoproduction with different scenarios for $b=15\mathrm{fm}$ at midrapidity ($y=0$). Panel (a): point source scenario, panel (b): Woods-Saxon distribution, and panel (c): realistic scenario described in the text. Panels (d)–(f) show the corresponding momentum distributions according to the amplitude scenarios in panels (a)–(c), respectively.

Figure 2

Amplitude and momentum distribution patterns of coherent $J/\psi$ photoproduction in Au $+$ Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ for midrapidity ($y=0$) with different impact parameters. Panels (a) and (d): $b=13.0\mathrm{fm}$, panels (b) and (e): $b=10.0\mathrm{fm}$, and panels (c) and (f): $b=5.7\mathrm{fm}$.

Figure 3

Amplitude and momentum distribution patterns of coherent $J/\psi$ photoproduction in Au $+$ Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ with $b=10.0\mathrm{fm}$ at different rapidities. Panels (a) and (d): $y=0.0$, panels (b) and (e): $y=0.6$, and panels (c) and (f): $y=1.4$.

Figure 4

Amplitude and momentum distribution patterns of coherent $J/\psi$ photoproduction at midrapidity ($y=0$) in Au $+$ Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ with a disruption effect from overlap region for different impact parameters. Panels (a) and (d): $b=13.0\mathrm{fm}$, panels (b) and (e): $b=10.0\mathrm{fm}$, and panels (c) and (f): $b=5.7\mathrm{fm}$.

Figure 5

Integrated yields of coherent $J/\psi$ production with and without an “observation” effect as a function of $N_{\mathrm{part}}$ in (a) Au $+$ Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$ and (b) Pb $+$ Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$. Data from the experiment of the ALICE Collaboration [16] are shown for comparison.