The proton–Ω correlation function in Au + Au collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">s</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">NN</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn><mml:mspace width="0.25em"/><mml:mtext>GeV</mml:mtext></mml:math>

We present the first measurement of the proton-correlation function in heavy-ion collisions for the central (0-40%) and peripheral (40-80%) Au + Au collisions at s NN = 200 GeV by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). Predictions for the ratio of peripheral collisions to central collisions for the proton-correlation function are sensitive to the presence of a nucleon-bound state. These predictions are based on the proton-interaction extracted from (2 + 1)-flavor lattice QCD calculations at the physical point. The measured ratio of the proton-correlation function between the peripheral (small system) and central (large system) collisions is less than unity for relative momentum smaller than 40 MeV/c. Comparison of our measured correlation ratio with theoretical calculation slightly favors a proton-bound system with a binding energy of 27 MeV.