论文标题
使用偶极子模型调查HERA领先中子事件的饱和效应和虚拟茶
Investigating saturation effects and the virtual pion in leading neutron events at HERA with the dipole model
论文作者
论文摘要
我们使用有或没有饱和的依赖性参数的颜色偶极子模型调查了HERA中$ EP $碰撞中中子非常正向中子的事件。这是对部署这些模型的领先中子过程的首次研究。将模型预测与可用的HERA测量值进行比较，价格为$ 6 <q^2 <100 $ 〜gev $^2 $，$ 70 <w <245 $ 〜GEV。我们的分析表明，这些模型表现出Feynman缩放，独立于$ Q^2 $。我们的结果表明，横截面的$ w $和$ q^2 $依赖性独立于限制片段化假设所预测的正向中子的存在，这是Feynman缩放本身的结果。我们推断，HERA领先的中子生产包含数据对饱和物理不敏感，这些横截面可能无法区分未来的$ EP $ colliders中的Gluon饱和效应。我们在小$ x $下的领先中子结构功能$ f_2^{ln} $的良好描述使用假设质子和质子的小$ x $结构是普遍的归一化。我们还表明，在最终状态下的矢量介子的独家衍射测量中的观察值对小$ x $时的饱和物理的敏感比包容性测量更敏感。最后，我们使用Yukawa Theory在Dipole模型中使用偶极模型中的$ \ hat t $频谱进行了预测，以对虚拟Pion的空间波函数进行建模。
We investigate events with very forward neutrons in $ep$ collisions at HERA using impact parameter dependent colour dipole models with and without saturation. This is the first study of the leading neutron process deploying these models. The model predictions are compared with the available HERA measurements for $6<Q^2<100$~GeV$^2$, $70<W<245$~GeV. Our analysis shows that the models exhibit Feynman scaling, independent of $Q^2$. Our results demonstrate that the $W$ and $Q^2$ dependence of the cross section is independent of the presence of a forward neutron as predicted by the limiting fragmentation hypothesis, which is a consequence of Feynman scaling itself. We infer that the HERA leading neutron production inclusive data is insensitive to saturation physics and these cross sections may not be able to distinguish gluon saturation effects in future $ep$ colliders. We provide a good description of the leading neutron structure function $F_2^{LN}$ at small $x$ using an assumption that the small-$x$ structure of protons and pions is universal up to a normalisation. We also show that the observables in the exclusive diffractive measurements with a vector meson in the final state are more sensitive to saturation physics at small $x$ than inclusive measurements. At last, we provide a prediction for the $\hat t$ spectrum in exclusive vector meson production in the dipole model using Yukawa theory to model the virtual pion's spatial wave function.
