论文标题
SIDI的饱和效应在非常远的速度
Saturation effects in SIDIS at very forward rapidities
论文作者
论文摘要
使用偶极子图片用于小bjorken $ x $的电子核核深弹性散射，我们研究了核靶标在核靶标对SIDIS横截面的影响（单个包含强生或JET，生产）。我们认为，可以通过在载有大量的虚拟光子纵向动量的强大分数$ z \ simeq 1 $上进行标记来增强此过程对Gluon饱和度的敏感性。这打开了在相对艰难的过程中研究gluon饱和度的可能性，其中虚拟性$ q^2 $比目标饱和动量$ q_s^2 $大，但使得$ z（1-z）q^2 \ lyssim q_s q_s^2 $。在限制$ z（1-z）q^2 \ ll q_s^2 $中工作，我们预测新现象将在SIDIS横截面中发出饱和度。对于产生粒子的足够低的横向动量$ k_ \ perp \ ll q_s $，主要贡献来自黑色磁盘极限中的弹性散射，这暴露了虚拟光子中未集成的夸克分布。对于较大的动量$ k_ \ perp \ gtrsim q_s $，非弹性碰撞扮演主角。他们通过多次散射探索Gluon饱和度，导致以$ q_s $为中心的$ k_ \ perp $中的高斯分布。当$ z（1-z）q^2 \ ll q^2 $时，这会导致核修饰因子（$ r_ {pa} $比率）中的cronin峰值，中等值$ x $。随着$ x $的减少，该峰被高能演化所消除，并由核抑制（$ r_ {pa} <1 $）取代，直至大型Momenta $ k_ \ perp \ perp \ gg q_s $。仍然适用于$ z（1-z）q^2 \ ll q_s^2 $，我们还计算了SIDIS横截面以$ k_ \ perp $集成。我们发现，弹性和非弹性散射都受到黑色磁盘极限的控制，因此它们在QCD耦合中产生了类似的零件。
Using the dipole picture for electron-nucleus deep inelastic scattering at small Bjorken $x$, we study the effects of gluon saturation in the nuclear target on the cross-section for SIDIS (single inclusive hadron, or jet, production). We argue that the sensitivity of this process to gluon saturation can be enhanced by tagging on a hadron (or jet) which carries a large fraction $z \simeq 1$ of the longitudinal momentum of the virtual photon. This opens the possibility to study gluon saturation in relatively hard processes, where the virtuality $Q^2$ is (much) larger than the target saturation momentum $Q_s^2$, but such that $z(1-z)Q^2\lesssim Q_s^2$. Working in the limit $z(1-z)Q^2\ll Q_s^2$, we predict new phenomena which would signal saturation in the SIDIS cross-section. For sufficiently low transverse momenta $k_\perp\ll Q_s$ of the produced particle, the dominant contribution comes from elastic scattering in the black disk limit, which exposes the unintegrated quark distribution in the virtual photon. For larger momenta $k_\perp\gtrsim Q_s$, inelastic collisions take the leading role. They explore gluon saturation via multiple scattering, leading to a Gaussian distribution in $k_\perp$ centred around $Q_s$. When $z(1-z)Q^2\ll Q^2$, this results in a Cronin peak in the nuclear modification factor (the $R_{pA}$ ratio) at moderate values of $x$. With decreasing $x$, this peak is washed out by the high-energy evolution and replaced by nuclear suppression ($R_{pA}<1$) up to large momenta $k_\perp\gg Q_s$. Still for $z(1-z)Q^2\ll Q_s^2$, we also compute SIDIS cross-sections integrated over $k_\perp$. We find that both elastic and inelastic scattering are controlled by the black disk limit, so they yield similar contributions, of zeroth order in the QCD coupling.
