We develop a framework to relate proton number cumulants measured in heavy-ion collisions within a momentum space acceptance to the susceptibilities of baryon number, assuming that particles are emitted from a fireball with uniform distribution of temperature and baryochemical potential, superimposed on a hydrodynamic flow velocity profile. The rapidity acceptance dependence of proton cumulants measured by the HADES Collaboration in $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV Au-Au appears to be consistent with thermal emission of nucleons from a grand-canonical heat bath, with the extracted baryon number susceptibilities exhibiting an hierarchy ${\chi }_4^B\gg -{\chi }_3^B\gg {\chi }_2^B\gg {\chi }_1^B$. Naively, this could indicate large non-Gaussian fluctuations that might point to the presence of the QCD critical point close to the chemical freeze-out at $T\sim 70$ MeV and ${\mu }_B\sim 850-900$ MeV. However, the description of the experimental data at large rapidity acceptances becomes challenging once the effect of exact baryon number conservation is incorporated, suggesting that more theoretical and experimental studies are needed to reach a firm conclusion.

我们开发了一个框架，将在动量空间接受内的重离子碰撞中测量的质子数累积量与重子数的敏感性联系起来，假设粒子从具有均匀温度和重化学势分布的火球发射，叠加在流体动力学流速上轮廓。HADES Collaboration 测量的质子累积量的快速接受依赖性$\sqrt{s_{\mathrm{神经网络}}}=2.4$GeV Au-Au 似乎与来自大正则热浴的核子热发射一致，提取的重子数磁化率表现出层次结构${\chi }_4^{乙}\gg -{\chi }_3^{乙}\gg {\chi }_2^{乙}\gg {\chi }_1^{乙}$. 天真地，这可能表明存在较大的非高斯波动，这可能表明存在接近化学冻结的 QCD 临界点$吨～70$兆伏安和${\mu }_{乙}～850-900$兆伏安。然而，一旦结合了精确重子数守恒的影响，对大快速度实验数据的描述就变得具有挑战性，这表明需要更多的理论和实验研究才能得出明确的结论。