An eikonal model for multiparticle production in hadron-hadron interactions

TL;DR

The paper develops an eikonal Monte Carlo framework that combines a perturbative hard-scattering component with a nonperturbative soft component to model multiparticle production in hadron-hadron collisions. Implemented within HERWIG, the model ensures unitarity via an eikonal approach and fixes the soft sector using the total cross section, guided by a Pomeron-inspired energy dependence for extrapolation. When tested against the CDF underlying-event data at 1.8 TeV, the eikonal model describes the observed activity—especially in the transverse region—more accurately than the existing HERWIG underlying-event and hard-multiparton models, with reduced sensitivity to the p_tmin cutoff. This framework provides a transparent, parameter-efficient means to study the balance between perturbative and nonperturbative contributions to the underlying event and offers a pathway for reliable predictions at higher energies, such as the LHC.

Abstract

We introduce an eikonal Monte Carlo model (running in conjunction with HERWIG) for simulating multiparticle production in hadron-hadron interactions. We compare our simulated data to the CDF Tevatron measurement of the underlying event activity in hard inelastic proton-antiproton scattering at sqrt(s)=1.8 TeV. By fixing the only free parameter in our model, the total hadron-hadron cross section, we find that our model describes the data better than either the HERWIG Underlying Event model or the Hard Multiparton model.

Figures (10)

• Figure 1: $\sigma_{SOFT}^{inc}(s_{p\overline{p}})$ corresponds to a soft collision between the two soft gluons (full color picture). Remnants are also connected to each other via $t$ channel gluon line.
• Figure 2: The soft collision between the two soft gluons, with dashed solid lines indicating the severed color connections between the remnants and the outgoing gluons, forming two clusters, $q_{1}\overline{q_{2}}$ and $q_{2}\overline{q_{2}}$.
• Figure 3: Toward, away and transverse regions from the leading in $p_{t}$ jet (see ref. Affolder:2002zg).The angle $\Delta$$\phi$ = $\phi$ - ${\phi_{jet\#1}}$ is the relative azimuthal angle between charged particles and the direction of jet$\#1$. The three regions are as follows; the toward region defined over the range $\mid$$\Delta$$\phi$$\mid$$<$${60^{\circ}}$ (this region includes the particles of the leading jet$\#1$), the away region defined over the range $\mid$$\Delta$$\phi$$\mid$$>$${120^{\circ}}$ and the transverse region defined over the range ${60^{\circ}}$$<$$\mid$$\Delta$$\phi$$\mid$$<$${120^{\circ}}$. Each region, toward, transverse, and away covers the same range $\mid$$\Delta$$\eta$$\mid$$\times$$\mid$$\Delta$$\phi$$\mid$=2$\times$${120^{\circ}}$.
• Figure 4: The average $P_t$ sum of charged particles as a function of $P_t$ (leading charged jet) in the toward region. HERWIG + Eikonal model solid line simulated data, experimental data solid circles.
• Figure 5: The average $P_t$ sum of charged particles as a function of $P_t$ (leading charged jet) in the away region. HERWIG + Eikonal model solid line simulated data, experimental data solid circles.