Double charm production e^+ e^- \to J/ψ+ c \bar{c} at B factories with next-to-leading order QCD corrections

TL;DR

The nonrelativistic QCD (NRQCD) factorization formalism is used, and it is found that the next-to-leading order (NLO) QCD virtual and real corrections can substantially enhance the cross section with a K factor of about 1.8.

Abstract

The inclusive $J/ψ$ production in $e^+ e^- \to J/ψc\bar c$ at B factories is one of the most challenging open problems in heavy quarkonium physics. The observed cross section of this double charm production process is larger than existing leading order (LO) QCD predictions by a factor of 5. In the nonrelativistic QCD (NRQCD) factorization formalism, we calculate the next-to-leading order (NLO) QCD virtual and real corrections to this process, and find that these corrections can substantially enhance the cross section with a $K$ factor of about 1.8. We further take into account the feeddown contributions from higher charmonium states (mainly the $ψ(2S)$ as well as $χ_{cJ}$) and the two-photon contributions, and find that the discrepancy between theory and experiment can be largely removed.

Figures (5)

• Figure 1: Two of the four Born diagrams for $e^- e^+ \to J/\psi c \bar{c}$.
• Figure 2: Twelve of the twenty-four box and pentagon diagrams for $e^-(k_1) e^+ (k_2)\to J/\psi(p_J)+ c(p_c) \bar{c}(p_{\bar{c}})$.
• Figure 3: Fifteen of the thirty real correction diagrams for $e^- e^+ \to J/\psi+ c \bar{c}+g$.
• Figure 4: Direct production cross sections of $e^+ + e^-\rightarrow J/\psi+c \bar{c}+X$ as functions of the renormalization scale $\mu$. Here $|R_S(0)|^2=1.01 {\rm GeV}^3$, $\Lambda=0.338 {\rm GeV}$, $\sqrt s=10.6{\rm GeV}$; NLO results are represented by solid lines and LO one by dashed lines; the upper line is for $m=1.4{\rm GeV}$ and the corresponding lower line is for $m=1.5{\rm GeV}$.
• Figure 5: Two of the six QED diagrams for $e^+e^- \to J/\psi c \bar{c}$.