A measurement of dielectron production in proton-proton (pp) collisions at $\sqrt{s}=13\mathrm{TeV}$, recorded with the ALICE detector at the CERN LHC, is presented in this Letter. The data set was recorded with a reduced magnetic solenoid field. This enables the investigation of a kinematic domain at low dielectron (ee) invariant mass $m_{\mathrm{ee}}$ and pair transverse momentum $p_{T,\mathrm{ee}}$ that was previously inaccessible at the LHC. The cross section for dielectron production is studied as a function of $m_{\mathrm{ee}}$, $p_{T,\mathrm{ee}}$, and event multiplicity $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$. The expected dielectron rate from hadron decays, called hadronic cocktail, utilizes a parametrization of the measured $\eta /{\pi }^0$ ratio in pp and proton-nucleus collisions, assuming that this ratio shows no strong dependence on collision energy at low transverse momentum. Comparison of the measured dielectron yield to the hadronic cocktail at $0.15<m_{\mathrm{ee}}<0.6\mathrm{GeV}/c^2$ and for $p_{T,\mathrm{ee}}<0.4\mathrm{GeV}/c$ indicates an enhancement of soft dielectrons, reminiscent of the “anomalous” soft-photon and soft-dilepton excess in hadron-hadron collisions reported by several experiments under different experimental conditions. The enhancement factor over the hadronic cocktail amounts to $1.61\pm 0.13(\mathrm{stat})\pm 0.17(\text{syst},\text{data})\pm 0.34(\text{syst},\text{cocktail})$ in the ALICE acceptance. Acceptance-corrected excess spectra in $m_{\mathrm{ee}}$ and $p_{T,\mathrm{ee}}$ are extracted and compared with calculations of dielectron production from hadronic bremsstrahlung and thermal radiation within a hadronic many-body approach.

中文翻译：

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质子-质子碰撞中的软介电子过量 ats=13TeV

质子-质子 (pp) 碰撞中双电子产生的测量 $\sqrt{秒}=13\mathrm{伏特}$用欧洲核子研究中心 LHC 的 ALICE 探测器记录的 ，在这封信中呈现。数据集是用减少的电磁场记录的。这使得研究低介电子 (ee) 不变质量的运动域成为可能${米}_{\mathrm{ee}}$ 和对横向动量 ${磷}_{吨,\mathrm{ee}}$这在以前在 LHC 上是无法获得的。研究了双电子产生的横截面作为函数${米}_{\mathrm{ee}}$, ${磷}_{吨,\mathrm{ee}}$, 和事件多重性 $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$. 来自强子衰变的预期双电子速率，称为强子鸡尾酒，利用测量的参数化$\eta /{\pi }^0$pp 和质子-核碰撞中的比率，假设该比率在低横向动量下对碰撞能量没有很强的依赖性。测量的双电子产率与强子鸡尾酒的比较$0.15<{米}_{\mathrm{ee}}<0.6\mathrm{电子伏特}/C^2$ 并为 ${磷}_{吨,\mathrm{ee}}<0.4\mathrm{电子伏特}/C$表明软双电子的增强，让人想起在不同实验条件下的几个实验报告的强子-强子碰撞中的“异常”软光子和软双轻子过剩。强子鸡尾酒的增强因子等于$1.61\pm 0.13(\mathrm{状态})\pm 0.17(\text{系统},\text{数据})\pm 0.34(\text{系统},\text{鸡尾酒})$在驴友验收。验收校正的过量光谱${米}_{\mathrm{ee}}$ 和 ${磷}_{吨,\mathrm{ee}}$ 提取并与强子多体方法中强子轫致辐射和热辐射的双电子产生计算进行比较。