# Measurement of $\psi(2S)$ meson production in $pp$ collisions at $\sqrt{s}$=7 TeV

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## Abstract

The differential cross-section for the inclusive production of psi(2S) mesons in pp collisions at sqrt(s)=7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated luminosity of 36 pb-1. The psi(2S) mesons are reconstructed in the decay channels psi(2S) -> mu+ mu- and psi(2S) -> J/psi pi+ pi-, with the J/psi meson decaying into two muons. Results are presented both for promptly produced psi(2S) mesons and for those originating from b-hadron decays. In the kinematic range pT(psi(2S)) <= 16 GeV/c and 2 < y(psi(2S)) <= 4.5 we measure 1.44 +- 0.01 +- 0.12+0.2-0.4 mub for prompt psi(2S) production and 0.25 +- 0.01 +- 0.02 mub for psi(2S) from b-hadron decays, where the last uncertainty on the prompt cross-section is due to the unknown psi(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/psi measurements we determine the inclusive branching fraction B(b -> psi(2S) X) = (2.73 +- 0.06 +- 0.16 +- 0.24) x 10^(-3), where the last uncertainty is due to the B(b -> J/psi X), B(J/psi -> mu+ mu-) and B(psi(2S) -> e+ e-) branching fraction uncertainties. All above results are corrected by an erratum included as an appendix.

## Figures and captions

 Invariant mass distribution for all $\psi(2S)$ candidates passing the selection cuts for the $\mu^+ \mu^-$ decay (a) and the $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu(\mu^+ \mu^-) \pi^+ \pi^-$ decay (b). Fig1a.pdf [344 KiB] HiDef png [202 KiB] Thumbnail [182 KiB] *.C file Fig1b.pdf [323 KiB] HiDef png [182 KiB] Thumbnail [159 KiB] *.C file Total efficiency { vs.} $p_{\mathrm{T}}$ computed from simulation for unpolarized $\psi {(2S)}$ mesons for $\psi(2S) \rightarrow \mu^+\mu^-$ (a) and $\psi(2S) \rightarrow J\mskip -3mu/\mskip -2mu\psi\mskip 2mu(\mu^+ \mu^-) \pi^+ \pi^-$ (b). Fig2a.pdf [73 KiB] HiDef png [124 KiB] Thumbnail [135 KiB] *.C file Fig2b.pdf [72 KiB] HiDef png [122 KiB] Thumbnail [134 KiB] *.C file Pseudo-decay-time distribution for $\psi(2S) \rightarrow \mu^+ \mu^-$ (a) and $\psi(2S) \rightarrow J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$(b) in the $p_{\mathrm{T}}$ range $4< p_{\mathrm{T}} \le5$ $\text{ Ge V /}c$ , showing the background and prompt contributions. Fig3a.pdf [794 KiB] HiDef png [1 MiB] Thumbnail [525 KiB] *.C file Fig3b.pdf [714 KiB] HiDef png [921 KiB] Thumbnail [383 KiB] *.C file Fraction of prompt $\psi(2S)$ as a function of $p_{\mathrm{T}}$ for the $\mu^+ \mu^-$ mode (solid squares) and the $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$ mode (open squares). Error bars include the statistical uncertainties and the systematic uncertainties due to the fitting procedure. This figure is updated in the Erratum (Appendix A). Fig4.pdf [296 KiB] HiDef png [143 KiB] Thumbnail [138 KiB] *.C file Dipion mass spectrum for the $\psi(2S) \rightarrow J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$ decay. The curve shows the result of the fit with Eq. (3) corrected for the acceptance. Fig5.pdf [293 KiB] HiDef png [170 KiB] Thumbnail [157 KiB] *.C file Comparison of the differential cross-sections measured for prompt $\psi(2S)$ (circles) and for $\psi(2S)$ from $b$-hadron decay (squares) in the $\psi(2S) \rightarrow \mu^+ \mu^-$ (solid symbols) and $\psi(2S) \rightarrow J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$ (open symbols) modes. Only the uncorrelated uncertainties are shown. \bf{This figure is obsolete. Corrected cross sections are found in Figs. 7 and 8 in the Erratum}. Fig6.pdf [329 KiB] HiDef png [189 KiB] Thumbnail [182 KiB] *.C file Differential production cross-section { vs.} $p_{\mathrm{T}}$ for prompt $\psi(2S)$. The predictions of three nonrelativistic QCD models are also shown for comparison. MWC \cite{bib:chao} and KB \cite{bib:bernd} are NLO calculations including colour-singlet and colour-octet contributions. AL \cite{bib:Lansberg,bib:Lansberg2} is a colour-singlet model including the dominant NNLO terms. This figure is updated in the Erratum. Fig7.pdf [385 KiB] HiDef png [277 KiB] Thumbnail [197 KiB] *.C file Differential production cross-section { vs.} $p_{\mathrm{T}}$ for $\psi(2S)$ from $b$-hadrons. The shaded band is the prediction of a FONLL calculation \cite{bib:FONLL_1,bib:FONLL_2,bib:cacciari}. This figure is updated in the Erratum. Fig8.pdf [308 KiB] HiDef png [209 KiB] Thumbnail [170 KiB] *.C file Ratio of $\psi(2S) \rightarrow \mu^+ \mu^-$ to $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \rightarrow \mu^+ \mu^-$ cross-sections for prompt production (a) and for $b$-hadron decay (b), as a function of $p_{\mathrm{T}}$ . This figure is updated in the Erratum. Fig9.pdf [56 KiB] HiDef png [297 KiB] Thumbnail [177 KiB] *.C file Fraction of prompt $\psi {(2S)}$ , $f_\mathrm{p}$, as a function of $p_{\mathrm{T}}$ . The error bars include statistical and systematic uncertainties added in quadrature. Fig4_e[..].pdf [15 KiB] HiDef png [88 KiB] Thumbnail [55 KiB] *.C file Differential production cross-section of prompt $\psi {(2S)}$ as a function of $p_{\mathrm{T}}$ in the range $2.0 < y < 4.5$. The results are compared with the NRQCD calculations \cite{Shao:2014yta}. The error bars include statistical and systematic uncertainties added in quadrature. Fig7_e[..].pdf [16 KiB] HiDef png [221 KiB] Thumbnail [159 KiB] *.C file Differential production cross-section of $\psi {(2S)}$ from $b$ hadrons as a function of $p_{\mathrm{T}}$ in the range $2.0 < y < 4.5$. The results are compared with the FONLL calculations \cite{Cacciari:1998it}. The error bars include statistical and systematic uncertainties added in quadrature. Fig8_e[..].pdf [17 KiB] HiDef png [271 KiB] Thumbnail [172 KiB] *.C file Ratio of $\psi {(2S)} \rightarrow \mu^+ \mu^-$ and $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \rightarrow \mu ^+\mu ^-$ cross-sections for prompt production (a) and for b-hadron decay (b), as a fucntion of $p_{\mathrm{T}}$ . Fig9a_[..].pdf [14 KiB] HiDef png [69 KiB] Thumbnail [41 KiB] *.C file Fig9b_[..].pdf [14 KiB] HiDef png [71 KiB] Thumbnail [41 KiB] *.C file Animated gif made out of all figures. PAPER-2011-045.gif Thumbnail

## Tables and captions

 Systematic uncertainties included in the measurement of the cross-section. Uncertainties labelled with $a$ are correlated between the $\mu^+ \mu^-$ and $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$ mode, while $b$ indicates a correlation between $\psi(2S) \rightarrow \mu^+ \mu^-$ and the $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \rightarrow \mu^+ \mu^-$ uncertainties \cite{bib:jpsi}. Table_1.pdf [58 KiB] HiDef png [143 KiB] Thumbnail [69 KiB] tex code Cross-section values for prompt $\psi(2S)$ and $\psi(2S)$ from $b$-hadrons in different $p_{\mathrm{T}}$ bins and in the range $2 < y \le 4.5$, evaluated as the weighted average of the $\mu^+ \mu^-$ and $J\mskip -3mu/\mskip -2mu\psi\mskip 2mu \pi^+ \pi^-$ channels. The first error is statistical, the second error is systematic, and the last asymmetric uncertainty is due to the unknown polarization of the prompt $\psi(2S)$ meson. This table is updated in the Erratum. Table_2.pdf [53 KiB] HiDef png [101 KiB] Thumbnail [57 KiB] tex code Differential cross-sections $\mathrm{d}\sigma/\mathrm{d} p_{\mathrm{T}}$ (in $\text{ nb}$ /( ${\mathrm{Ge V /}c}$ )) of prompt $\psi {(2S)}$ and $\psi {(2S)}$ -from-$b$ hadrons at $\sqrt{s} = 7\text{ Te V}$, integrated over $y$ between 2.0 and 4.5. The first uncertainty is statistical and the second systematic. The third asymmetric uncertainty for the prompt $\psi {(2S)}$ mesons is due to the unknown polarisation. Table_2.pdf [53 KiB] HiDef png [101 KiB] Thumbnail [57 KiB] tex code

Created on 10 July 2020.