Study of $J/ψ$ production and cold nuclear matter effects in $p$Pb collisions at $\sqrt{s_{NN}}=5 \mathrm{TeV}$ (1308.6729v4)

Abstract: The production of $J/\psi$ mesons with rapidity $1.5<y<4.0$ or $-5.0<y<-2.5$ and transverse momentum $p_\mathrm{T}<14 \mathrm{GeV}/c$ is studied with the LHCb detector in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$. The analysis is based on a data sample corresponding to an integrated luminosity of about $1.6 \mathrm{nb}^{-1}$. For the first time the nuclear modification factor and forward-backward production ratio are determined separately for prompt $J/\psi$ mesons and $J/\psi$ from $b$-hadron decays. Clear suppression of prompt $J/\psi$ production with respect to proton-proton collisions at large rapidity is observed, while the production of $J/\psi$ from $b$-hadron decays is less suppressed. These results show good agreement with available theoretical predictions. The measurement shows that cold nuclear matter effects are important for interpretations of the related quark-gluon plasma signatures in heavy-ion collisions.

• The paper quantifies cold nuclear matter effects by demonstrating ~40% suppression in prompt J/ψ production.
• It employs LHCb dimuon decay data within specific rapidity and pT ranges to distinguish between prompt and non-prompt J/ψ yields.
• Comparisons with models, including EPS09 NLO, validate the observed CNM effects and aid in interpreting QGP signals in heavy-ion collisions.

Study of $\jpsi$ Production and Cold Nuclear Matter Effects in $p\mathrm{Pb}$ Collisions at $\sqrt{s_{\small NN}}=5$ TeV

The paper presents a systematic paper of $\jpsi$ meson production in proton-lead ($p\mathrm{Pb}$) collisions at the Large Hadron Collider (LHC). The focus is on investigating cold nuclear matter (CNM) effects, such as nuclear absorption, parton shadowing, and energy loss, which can influence particle production in high-energy nuclear collisions. The research utilizes data from the LHCb detector and forms part of a more comprehensive effort to distinguish CNM effects from those related to quark-gluon plasma (QGP) formation, which is a distinct signature in heavy-ion collisions.

Key Findings and Methodology

• Data and Kinematic Range: The analysis uses a data set corresponding to an integrated luminosity of approximately 1.6 nb$^{-1}$, with $\jpsi$ mesons analyzed through their dimuon decay channels. The kinematic range for rapidity is $1.5 < y < 4.0$ (forward region) and $-5.0 < y < -2.5$ (backward region), with transverse momentum $p_T < 14$ GeV/$c$.
• Nuclear Modification Factor ($R_{\pPb}$): For the first time, $R_{\pPb}$ and the forward-backward production ratio $R_{\text{FB}}$ are determined separately for prompt $\jpsi$ mesons and $\jpsi$ from $b$-hadron decays. The results indicate a significant suppression (about 40%) of prompt $\jpsi$ production at large rapidities, consistent with CNM effects. However, $\jpsi$ from $b$-hadron decays exhibit less suppression, highlighting different interaction dynamics.
• Comparison with Theoretical Models: The paper compares experimental results with predictions from various theoretical models, including those incorporating parton shadowing and coherent parton energy loss. The measurements are well-aligned with most models, although discrepancies exist with particular approaches, such as those using the EPS09 NLO parameterization.
• Implications for Heavy-Ion Collisions: These findings underline the necessity to account for CNM effects when interpreting quark-gluon plasma signatures in nucleus-nucleus collisions. By isolating CNM effects in $p\mathrm{Pb}$ collisions, researchers can better understand phenomena in more complex systems like lead-lead (PbPb) collisions.

Implications and Future Directions

The paper's outcome enhances the understanding of CNM effects in $\jpsi$ production, providing critical inputs for refining models of hadronic interactions in nuclear environments. Future advancements could involve extending the analysis to other quarkonia states or various kinematic regions, helping to clarify different suppression mechanisms further. Additionally, comparisons with results from other LHC detectors, such as ALICE, offer opportunities for cross-validation and expanded exploration of QGP properties.

Overall, the paper sets the groundwork for improved analysis of QGP phenomena, fostering deeper insights into the behavior of matter under extreme temperatures and densities, which are essential for theoretical and practical advancements in high-energy nuclear physics.