{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"2809a061ce7dc1c0b759c77c7032a31da391af27a5c4c7c8002e362e8edf1844","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011","59c70c58ebc1de8bff7fc3398a95a4795b7d421f35be6bf7283b56f00e4e3db6"],"salt":"489ef48f92b491962e85871e754878083de8adba2a715f7f0cd0c3374de85149","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"nuc.qcd-phase-diagram.bes-fluctuation-signal","kind":"phenomenon","literature_status":"contested","n":"1","parents":[{"note":"","parent_revision":"59c70c58ebc1de8bff7fc3398a95a4795b7d421f35be6bf7283b56f00e4e3db6","relation":"special_case"}],"plain":"The STAR experiment counted how the number of protons minus antiprotons varies from collision to collision as it lowered the collision energy. In 2025 it reported a dip near one energy, and whether a critical point causes it is unclear.","posed_since":"2025","precise":"STAR Beam Energy Scan II (PRL 2025) measured the net-proton cumulant ratio $C4/C2$ in 0-5 percent central $\\mathrm{Au}+\\mathrm{Au}$ collisions at $\\sqrt{s_{NN}} = 7.7 \\text{ to } 27 \\mathrm{GeV}$ and found a minimum near 19.6 GeV deviating from non-critical baselines by 2 to 5 standard deviations. Determine whether this follows from a critical point, using dynamical models with baryon-number conservation, finite size and lifetime, and non-equilibrium evolution, or from non-critical effects. Answer: yes or no with quantified model uncertainty.","problem_ref":null,"references":"","settled_by":"Fixed-target data below $7.7\\,\\mathrm{GeV}$ (STAR FXT, HADES, CBM at FAIR) testing the predicted energy dependence of $C4/C2$, together with dynamical simulations reproducing the full excitation function.","status_note":"The significance depends on the choice of non-critical baseline, and no dynamical critical-point model had reproduced the full energy dependence as of 2026.","title":"Is the STAR net-proton fluctuation dip a critical-point signal?","topic_ref":"8cebfc31c6dfbbabf0b4214c4b9557e92e9b9f0d637fcd43a3fcc8c806d62935"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"1861e29d082f19222e4187ebd2a98c97d7eccf3a4cd5520788e1d3ee513b7171","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b8af46dfdcf8ae9a98be497a777ef1bedf48879077e06577fb2cefd108c98585","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"RPzzPo42TWdaMtiWVzYi8ichxem_f0LJ5jTRGzntyVuMMBbuZ-5lMf71c72k8feG4vq6q4ji7CQeMWO82I8FDw"},"schema":"pubphys.envelope/1"},"record_hash":"1861e29d082f19222e4187ebd2a98c97d7eccf3a4cd5520788e1d3ee513b7171","leaf_index":1800}