Evidence for BFKL and saturation dynamics from di-hadron spectra at the LHC

Abstract

We demonstrate that rapidity separated di-hadron spectra in high multiplicity proton-proton collisions at the LHC can be quantitatively described by a combination of BFKL and saturation dynamics. Based on these results, we predict the systematics of di-hadron spectra in proton-nucleus collisions at the LHC.

Figures (5)

• Figure 1: Anatomy of di-hadron correlations. The glasma graph on the left illustrates its its schematic contribution to the double inclusive cross-section (dashed orange curve). On the right is the back-to-back graph and the shape of its yield (dashed blue curve). The grey blobs denote emissions all the way from beam rapidities to those of the triggered gluons. The solid black curve represents the sum of contributions from glasma and back-to-back graphs. The shaded region represents the Associated Yield (AY) calculated using the zero-yield-at-minimum (ZYAM) procedure.
• Figure 2: The integrated associated nearside yield per trigger as a function of $p^{\textrm{trig}}_T$ in three different $p^{\textrm{asc}}_T$ windows for high multiplicity p+p collisons. Filled symbols denote CMS data points extracted from the published $p^{\textrm{trig}}_T$, $p^{\textrm{asc}}_T$ di-hadron matrix Khachatryan:2010gv. Open symbols are our results, with dashed lines between points to guide the eye.
• Figure 3: The associated yield per trigger as a function of $p^{\textrm{trig}}_T$ in min.bias p+Pb collisions at $\sqrt{s}=5$ TeV (left) and central p+Pb collisions (right). Predictions are for the same $p^{\textrm{asc}}_T$ windows as for high multiplicity p+p collisons, and results from the latter are presented for comparison as dashed lines.
• Figure 4: CMS data after the removal of the underlying event in each bin via the ZYAM procedure. The solid curve is the BFKL result added to the Glasma result with K-factors of $K_{\rm{BFKL}}=1.1$ and $K_{\rm{Glasma}}=2.3$. The solid (dashed) gray curves show the result without BFKL evolution in the MRK (QMRK) framework.
• Figure 5: BFKL prediction for the away-side yield in minimum bias p+Pb collisions at $\sqrt{s}=5$ TeV. The gray curves show the corresponding results from central p+p. The underlying event has been subtracted from each bin.