Bottomonium Production in the Regge Limit of QCD
B. A. Kniehl, V. A. Saleev, D. V. Vasin
TL;DR
The paper investigates bottomonium hadroproduction at the Tevatron within the quasi-multi-Regge kinematics (QMRK) framework combined with NRQCD factorization at leading order in $α_s$ and $v$, emphasizing the Regge limit where unintegrated gluon densities and reggeized gluons govern dynamics. It derives LO QMRK amplitudes, relates them to $k_T$-factorization, and performs fits to CDF Run I/II data for prompt $\Upsilon(nS)$ using three unintegrated gluon distributions (JB, JS, KMR) to extract color-octet NMEs for multiple bottomonium states. The results indicate small color-octet NMEs for bottomonium, especially when including feed-down from the yet-unobserved $\chi_{bJ}(3P)$ states, with the KMR gluon providing the best fit; this suggests stronger suppression of octet contributions in bottomonium than in charmonium and supports the QMRK approach as a robust LO tool in the Regge limit. The authors also highlight the necessity of NLO analyses to reduce theoretical uncertainties and to connect LO QMRK results with the broader collinear framework.
Abstract
We study bottomonium hadroproduction in proton-antiproton collisions at the Fermilab Tevatron in the framework of the quasi-multi-Regge kinematics approach and the factorization formalism of non-relativistic QCD at leading order in the strong-coupling constant alpha_s and the relative velocity v of the bound quarks. The transverse-momentum distributions of prompt Upsilon(nS)-meson production measured at the Tevatron are fitted to obtain the non-perturbative long-distance matrix elements for different choices of un-integrated gluon distribution functions of the proton.