Investigation of beauty production and parton shower effects at LHC

TL;DR

The paper examines beauty production at the LHC within the $k_T$-factorization framework using unintegrated gluon densities from the CCFM evolution and the KMR prescription. It compares parton-level ($LZ$) and hadron-level Cascade predictions to CMS and LHCb 7 TeV data, studying the impact of initial- and final-state parton showers and various fragmentation schemes. The results show good agreement for $b$-hadron and muon cross sections with CCFM A0 gluons, while angular correlations are not fully described, underscoring the importance of initial gluon transverse momentum and shower effects. The study quantifies theoretical uncertainties from evolution schemes, quark masses, scales, and fragmentation, placing the predictions within current uncertainty bands and highlighting areas for further refinement.

Abstract

We present hadron-level predictions from the Monte Carlo generator Cascade and parton level calculations of open b quark, b-flavored hadron and inclusive b-jet production in the framework of the kt-factorization QCD approach for the LHC energies. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation and the Kimber-Martin-Ryskin (KMR) prescription. Our predictions are compared with the first data taken by the CMS and LHCb collaborations at 7 TeV. We study the theoretical uncertainties of our calculations and investigate the effects coming from parton showers in initial and final states. The special role of initial gluon transverse momenta in description of the data is pointed out.

Figures (11)

• Figure 1: The transverse momentum and rapidity distributions of $B^+$ meson production at the LHC. The kinematical cuts applied are described in the text. The solid, dashed and dotted histograms correspond to the results obtained with the CCFM set A0, B0 and KMR unintegrated gluon densities. The first column shows the LZ results while the second one depicts the Cascade predictions. The experimental data are from CMS2.
• Figure 2: The transverse momentum and rapidity distributions of $B^0$ meson production at the LHC. The kinematical cuts applied are described in the text. The left histograms show the LZ numerical results while the right plots depict the Cascade predictions. Notation of all histograms is the same as in Fig. 1. The experimental data are from CMS3.
• Figure 3: The transverse momentum and pseudorapidity distributions of muons arising from the semileptonic decays of $b$ quarks at the LHC. The kinematical cuts applied are described in the text. The left histograms show the LZ numerical results while the right plots depict the Cascade predictions. Notation of all histograms is the same as in Fig. 1. The experimental data are from CMS4.
• Figure 4: The pseudorapidity distributions of $b$-flavored hadrons at the LHC. The kinematical cuts applied are described in the text. The left histogram shows the LZ numerical results while the right plot depicts the Cascade predictions. Notation of all histograms is the same as in Fig. 1. The experimental data are from LHCb1.
• Figure 5: The double differential cross sections $d\sigma/dy\,dp_T$ of inclusive $b$-jet production as a function of $p_T$ in different $y$ regions (LZ predictions). Notation of all histograms is the same as in Fig. 1. The experimental data are from CMS6.