High-statistics \(\pi ^-\pi ^-\) and \(\pi ^+\pi ^+\) femtoscopy data are presented for Au + Au collisions at \(\sqrt{s_\mathrm{NN}} = 2.4~\hbox {GeV}\), measured with HADES at SIS18/GSI. The experimental correlation functions allow the determination of the space-time extent of the corresponding emission sources via a comparison to models. The emission source, parametrized as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, azimuthal emission angle with respect to the reaction plane, collision centrality and beam energy. For all centralities and transverse momenta, a geometrical distribution of ellipsoidal shape is found in the plane perpendicular to the beam direction with the larger extension perpendicular to the reaction plane. For large transverse momenta, the corresponding eccentricity approaches the initial eccentricity. The eccentricity is smallest for most central collisions, where the shape is almost circular. The magnitude of the tilt angle of the emission ellipsoid in the reaction plane decreases with increasing centrality and increasing transverse momentum. All source radii increase with centrality, largely exhibiting a linear rise with the cube root of the number of participants. A substantial charge-sign difference of the source radii is found, appearing most pronounced at low transverse momentum. The extracted source parameters are consistent with the extrapolation of their energy dependence down from higher energies.

中文翻译：

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在$$ \ sqrt {s _ {\ mathrm {NN}}} = 2.4〜\ hbox {GeV} $$ sNN = 2.4GeV的同等介子强度干涉仪

呈现了\（\ sqrt {s_ \ mathrm {NN}}处Au + Au碰撞的高统计\（\ pi ^-\ pi ^-\）和\（\ pi ^ + \ pi ^ + \） fefeoscopy数据。= 2.4〜\ hbox {GeV} \），使用SIS18 / GSI上的HADES测量。实验相关函数允许通过与模型进行比较来确定相应排放源的时空范围。根据成对的横向动量，相对于反应平面的方位角发射角，碰撞中心和射束能量研究了参数化为三维高斯分布的发射源。对于所有中心点和横向动量，在垂直于光束方向的平面中发现椭圆形的几何分布，而较大的延伸垂直于反应平面。对于较大的横向力矩，相应的偏心距接近初始偏心距。对于大多数中央碰撞，形状几乎是圆形的，偏心率最小。发射椭球在反应平面中的倾斜角的大小随中心度的增加和横向动量的增加而减小。所有源半径都随着中心性的增加而增加，并且在很大程度上随参与者人数的立方根呈线性增加。发现源半径存在显着的电荷符号差异，在低横向动量下最明显。提取的源参数与其从较高能量向下的能量依赖性外推相一致。在较低的横向动量下显得最为明显。提取的源参数与其从较高能量向下的能量依赖性外推相一致。在较低的横向动量下显得最为明显。提取的源参数与其从较高能量向下的能量依赖性外推相一致。