CGC predictions for p+Pb collisions at the LHC (1209.2001v3)

Abstract: We present predictions for total multiplicities and single inclusive particle production in proton-lead collisions at the LHC. The main dynamical input in our calculations is the use of solutions of the running coupling BK equation tested in e+p data. We use a Monte-Carlo treatment of the nuclear geometry and either $k_t$-factorization or the hybrid formalisms to describe particle production in the central and forward rapidity regions, respectively.

CGC Predictions for Proton-Lead Collisions at the LHC

The paper "CGC predictions for p+Pb collisions at the LHC" by Javier L. Albacete et al. investigates the theoretical predictions for proton-lead (p+Pb) collisions at the Large Hadron Collider (LHC) using the framework of the Color Glass Condensate (CGC). This paper aims to provide baseline predictions for multiplicities and single inclusive particle production, which are pivotal for understanding the dynamics of strong color fields in high-energy nuclear collisions.

Key Components

1. Color Glass Condensate Framework: The CGC is a theoretical framework that describes the high-density gluonic state at small values of the Bjorken variable $x$. It incorporates non-linear QCD dynamics and saturation effects, characterized by the saturation scale $Q_s(x)$.
2. Running Coupling BK Equation: The researchers employ the running coupling Balitsky-Kovchegov (rcBK) equation, which describes the evolution of the dipole scattering amplitude. This equation is pivotal for predicting the behavior of gluon densities at small-$x$, a regime relevant for LHC energies.
3. Particle Production Formalisms: Two approaches are discussed for calculating particle spectra:
   • $k_t$-factorization for central rapidity regions.
   • Hybrid formalism for forward rapidities.

Numerical Predictions and Implications

• Multiplicities and Spectra: The paper offers detailed predictions for charged particle multiplicities and transverse momentum spectra in p+Pb collisions. They utilize realistic models of nuclear geometry and account for fluctuations in nucleon configurations.
• Centrality Dependence: Predictions for the centrality dependence of observables provide insights into the interaction dynamics, emphasizing the role of initial state effects.
• Nuclear Modification Factors: The predictions for nuclear modification factors $R_{pPb}$ account for potential suppression or enhancement patterns due to saturation effects, which are influenced by parton transverse momentum and rapidity.

Practical and Theoretical Implications

From a theoretical standpoint, the CGC framework offers a coherent picture of non-linear QCD dynamics at high energies, potentially bridging the gap between theoretical predictions and experimental measurements. Practically, the paper's predictions serve as benchmarks for future LHC experiments, aiding the interpretation of collision data in terms of saturation physics versus other high-energy phenomena.

Future Developments

Continued experimental data collection at the LHC will validate the CGC predictions, allowing researchers to refine models and deepen the understanding of saturation physics. Future work might explore higher-order corrections to the rcBK equation and further investigate the impact of fluctuations in nuclear geometry on particle production.

In conclusion, the paper provides a comprehensive set of predictions for p+Pb collisions at the LHC within the CGC framework, offering valuable insights into strong color fields dynamics in nuclear physics. It sets the stage for both theoretical exploration and experimental validation at high-energy particle colliders.