Hadronic photon-photon interactions at high energies

TL;DR

The paper develops and applies the phojet event generator within the two-component Dual Parton framework to photon-photon interactions at high energies. It validates the approach against hadron-hadron and photon-hadron data and extends predictions to photon-photon collisions, emphasizing the roles of soft and hard processes, minijets, and direct photon contributions. It discusses photon flux modeling via bremsstrahlung, beamstrahlung, and laser-backscattering, and provides concrete predictions for photon-photon production at present and future e+e- colliders (including TESLA and LEP-II scenarios). The results indicate similar minimum-bias hadron production across hadronic and photonic collisions when diffractive channels are excluded, with notable enhancements in the high-p_T region for photon-photon events due to direct interactions and harder photon structure functions, offering essential background estimates for collider physics.

Abstract

Photon-photon collisions are investigated in the framework of the two-component Dual Parton Model. The model is shown to agree well to hadron production data from hadron-hadron and photon-hadron collisions. The multiparticle production in hadron-hadron, photon-hadron and photon-photon collisions as predicted by the model is compared. Strong differences are only found as function of the transverse momentum variable. The hadron production in photon-photon collisions at present and future electron-positron colliders is studied using photon spectra according to the equivalent photon approximation, according to beamstrahlung and according to backscattered laser radiation.

Figures (26)

• Figure 1: Inelastic photon-photon cross sections as calculated in the model compared with experimental data at low energies Feindt86Aihara90aBehrend91aBerger84aBintinger85a. The two curves from the model were calculated using the GRV LO photon structure function GRV92b and the SaS 2M photon structure function Schuler95a. The differences between both curves at high energy demonstrate the uncertainties of the predictions due to the limited data available on the photon structure function. Our curve calculated with the SaS 2M structure function agrees practically with the cross section calculated with the same structure function but using another model by Schuler and Sjöstrand schusjo94a.
• Figure 2: Diffractive cross sections as calculated with phojet using the GRV LO photon structure function GRV92b and the SaS 2M photon structure function Schuler95a. The upper curve is for each of the three cross sections the one obtained with the GRV LO structure function.
• Figure 3: Unitarity cut of a one-pomeron graph: the unitarity sum including all possible final states is subdivided into final states with low-$p_\perp$ partons and into final states with at least one parton satisfying $p_\perp \ge p_\perp^{\hbox{\scriptsize cutoff}}$.
• Figure 4: Comparison of transverse momentum distributions of charged hadrons with collider data at $\sqrt s$ = 200 GeV Albajar90. The calculation uses the Dual Parton Model code phojet.
• Figure 5: Pseudorapidity distributions of charged hadrons produced in $\bar{p}$-$p$ collisions as calculated with phojet are compared to collider data from the UA-5 Collaboration Alner86bAbe90 for the energy $\sqrt s =$ 200 GeV.