QCD radiative corrections to ${\chi }_{cJ}$ production at hadron colliders

Abstract

To clarify the outstanding problem in charmonium production that existing theories cannot explain the observed cross sections of ${\chi }_{cJ}$ (J=0,1,2) and ratio $R_{{\chi }_c}={\sigma }_{{\chi }_{c2}}/{\sigma }_{{\chi }_{c1}}\approx 0.75$ (in contrast to the spin counting value 5/3) at the Tevatron, we study the complete next-to-leading order radiative corrections in nonrelativistic QCD, and find next-to-leading order contributions of ${}^3{P}_J^{[1]}$ are more important than leading order at high $p_T$, and ${}^3{P}_1^{[1]}$ decreases slower than ${}^3{P}_2^{[1]}$, implying a natural explanation for the $R_{{\chi }_c}$ puzzle. By fitting $R_{{\chi }_c}$, the predicted cross sections of ${\chi }_{cJ}$ are found to agree with data. The result indicates color-octet contribution is crucially needed, thus providing a unique test for heavy quarkonium production mechanisms. Feed-down contributions of ${\chi }_{cJ}$ to prompt $J/\psi$ production are estimated to be substantial, about $30-40$ at $p_T=20$ GeV. Production of ${\chi }_{cJ}$ (J=0,1,2) at the LHC is also predicted.

Version published in PRD (Rapid Communication); Title changed as suggested by journal editor; in Fig.5 predictions and data at Tevatron (as well as at LHC) are shown; no changes for physical results

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Cited by in corpus (2)

• Reconciling J/psi production at HERA, RHIC, Tevatron, and LHC with NRQCD factorization at next-to-leading order
• ${\chi }_{cJ}$ production associated with a $c\bar{c}$ pair at hadron colliders