# Measurement of the ratio of prompt $\chi_{c}$ to $J/\psi$ production in $pp$ collisions at $\sqrt{s}=7$ TeV

LHCb Collaboration; Bernet, R; Büchler-Germann, A; Bursche, A; Chiapolini, N; De Cian, M; Elsasser, C; Müller, K; Palacios, J; Salzmann, C; Serra, N; Steinkamp, O; Straumann, U; Tobin, M; Vollhardt, A; Anderson, J; Aaij, R; Abellán Beteta, C; Adeva, B; Zvyagin, A (2012). Measurement of the ratio of prompt $\chi_{c}$ to $J/\psi$ production in $pp$ collisions at $\sqrt{s}=7$ TeV. Physics Letters B, 718(2):431-440.

## Abstract

The prompt production of charmonium $\chi_{c}$ and $J/\psi$ states is studied in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the Large Hadron Collider. The $\chi_{c}$ and $J/\psi$ mesons are identified through their decays $\chi_{c}\rightarrow J/\psi \gamma$ and $J/\psi\rightarrow \mu^+\mu^-$ using 36 pb$^{-1}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for $\chi_{c}$ and $J/\psi$, $\sigma (\chi_{c}\rightarrow J/\psi \gamma)/ \sigma (J/\psi)$, is determined as a function of the $J/\psi$ transverse momentum in the range $2 < p_{\mathrm T}^{J/\psi} < 15$ GeV/$c$. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low $p_{\mathrm T}^{J/\psi}$ region.

## Abstract

The prompt production of charmonium $\chi_{c}$ and $J/\psi$ states is studied in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the Large Hadron Collider. The $\chi_{c}$ and $J/\psi$ mesons are identified through their decays $\chi_{c}\rightarrow J/\psi \gamma$ and $J/\psi\rightarrow \mu^+\mu^-$ using 36 pb$^{-1}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for $\chi_{c}$ and $J/\psi$, $\sigma (\chi_{c}\rightarrow J/\psi \gamma)/ \sigma (J/\psi)$, is determined as a function of the $J/\psi$ transverse momentum in the range $2 < p_{\mathrm T}^{J/\psi} < 15$ GeV/$c$. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low $p_{\mathrm T}^{J/\psi}$ region.

## Citations

36 citations in Web of Science®
35 citations in Scopus®

## Altmetrics

Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics English 2012 12 Mar 2013 12:52 05 Jun 2016 08:07 Elsevier 0370-2693 Publisher DOI. An embargo period may apply. https://doi.org/10.1016/j.physletb.2012.10.068