# Study of $\Upsilon$ production and cold nuclear matter effects in pPb collisions at $\sqrt{s_{NN}}=5 \mathrm{TeV}$

[to restricted-access page]

## Abstract

Production of $\Upsilon$ mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$ is studied with the LHCb detector. The analysis is based on a data sample corresponding to an integrated luminosity of $1.6 \mathrm{nb}^{-1}$. The $\Upsilon$ mesons of transverse momenta up to $15 \mathrm{GeV}/c$ are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is $1.5<y<4.0$ (forward region) and $-5.0<y<-2.5$ (backward region). The forward-backward production ratio and the nuclear modification factor for $\Upsilon(1S)$ mesons are determined. The data are compatible with the predictions for a suppression of $\Upsilon(1S)$ production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt $J/\psi$ mesons.

 Invariant mass distribution of $\mu^{+}\mu^{-}$ pairs in the (left) forward and (right) backward samples of $p\mathrm{Pb}$ collisions. The transverse momentum range is $p_{\rm T} <15 {\mathrm{ Ge V /}c}$. The rapidity range is $1.5 ## Tables and captions  Relative systematic uncertainties on the cross-sections, in percent, in the full rapidity range. The values in parenthesis refer specifically to$\Y1S$measurements when systematic uncertainties in the common rapidity range$2.5<|y|<4.0\$ are notably different. Table_1.pdf [19 KiB] HiDef png [95 KiB] Thumbnail [47 KiB] tex code

Created on 18 January 2020.