QCD corrections to $J/ψ$ plus $Z^0$-boson production at the LHC

TL;DR

This work computes the NLO QCD corrections to J/ψ+Z^0 production at the LHC within the NRQCD framework, focusing on the dominant gg→car{c}[^3S_1^(1)]+Z^0 and qar{q}→car{c}[^3S_1^(8)]+Z^0 channels. The calculation includes virtual, real-gluon, and real-light-quark emissions, with IR/collinear divergences canceled by standard renormalization and PDF counterterms using TCPSS phase-space slicing. Numerically, the NLO corrections substantially boost the differential cross section, with K-factors up to about 3.4 across the J/ψ transverse momentum range, and CO contributions becoming dominant at high p_T, illustrating the potential of LHC measurements to test NRQCD color-octet dynamics and constrain LDME values.

Abstract

The $J/ψ+Z^0$ associated production at the LHC is an important process in investigating the color-octet mechanism of non-relativistic QCD in describing the processes involving heavy quarkonium. We calculate the next-to-leading order (NLO) QCD corrections to the $J/ψ+Z^0$ associated production at the LHC within the factorization formalism of nonrelativistic QCD, and provide the theoretical predictions for the distribution of the $J/ψ$ transverse momentum. Our results show that the differential cross section at the leading-order is significantly enhanced by the NLO QCD corrections. We conclude that the LHC has the potential to verify the color-octet mechanism by measuring the $J/ψ+Z^0$ production events.

Figures (5)

• Figure 1: The tree-level Feynman diagrams for the partonic processes $q\bar{q} \to J/\psi +Z^0~$(1-4) and $gg \to J/\psi +Z^0~$(5-12).
• Figure 2: Some representative QCD one-loop Feynman diagrams for the partonic processes $gg \to c\bar{c}[^3S_1^{(1)}] + Z^0$ (1-6) and $q\bar{q} \to c\bar{c}[^3S_1^{(8)}] + Z^0$ (7-12).
• Figure 3: Some representative Feynman diagrams for real gluon/light-(anti)quark emission partonic processes.
• Figure 4: The dependence of the LO and the NLO QCD corrected cross sections for the process $pp \to J/\psi +Z^0+X~$ on the factorization scale and renormalization scale ($\mu$/$\mu_0$) at the LHC where we define $\mu=\mu_f=\mu_r$ and $\mu_0 = m_T$.
• Figure 5: The LO and NLO QCD corrected distributions of $p_T^{J/\psi}$ and the corresponding K-factor for the $pp \to J/\psi +Z^0+X~$ process at the LHC.