A realistic photon spectra in polarized γγ processes in SANCphot

TL;DR

The paper addresses the need for precise simulation of polarized γγ processes by extending SANCphot beyond the linear Compton approximation to incorporate general energy distributions and realistic polarization states. It introduces a CAIN-based, nonlinear Compton framework whose outputs are mapped into piecewise luminosity and polarization distributions and fed into SANCphot, enabling arbitrary input spectra while preserving polarization information. Numerical results show that using CAIN-derived spectra with realistic beam geometry can significantly alter cross sections and kinematic distributions—in particular increasing σ(γγ→γγ) by roughly 50–100% at certain energies while reducing channels with final Z bosons—without erasing polarization features. The approach enhances predictive accuracy for Standard Model and Beyond-Standard Model studies in γγ collisions and provides a flexible path to include beamstrahlung-like spectra in future analyses.

Abstract

This work presents an approach to improve the precision of polarized photon-photon collisions simulation implemented in the SANCphot package. The basic linear Compton approximation of the incoming photon spectrum is extended to a general energy distribution and a realistic description of circular or linear polarizations as expected to be seen at photon-photon colliders.

Figures (6)

• Figure 1: A comparison of normalized photon energy spectra $\frac{1}{N_\gamma} \frac{dN_\gamma}{dx}$ and cross section polarizing coefficients $d\langle\xi2\rangle/dx$ and $d\langle\xi3\rangle/dx$ depending on the fraction of transferred energy $x$. The left and right columns correspond to linear and circular laser polarizations respectively.
• Figure 2: The kinematic distributions for $\gamma\gamma\rightarrow\gamma\gamma$ process at 500GeV with linear Compton approximation. Upper plots are based on the analytic expressions from SANCphot. Lower plots give the ratios of distributions built using piecewise approximation of SANCphot (red) and CAIN (blue) spectra to the analytic values.
• Figure 3: Final state $\cos\theta$ kinematic distributions for electron beam energy $\sqrt{s_{ee}} = 500$ GeV and various polarizations (see text). The color legend for $\gamma\gamma\rightarrow\gamma\gamma$ plot applies to the other two.
• Figure 4: Final state invariant mass kinematic distributions for different electron beam energies $\sqrt{s_{ee}} = 500$ GeV (upper row) and 1000 GeV (lower row) and various polarizations (see text). The color legend for 500 GeV $\gamma\gamma\rightarrow\gamma\gamma$ plot applies to the others.
• Figure 5: Final state transverse momentum kinematic distributions for different electron beam energies $\sqrt{s_{ee}} = 500$ GeV (upper row) and 1000 GeV (lower row) and various polarizations (see text). The color legend for 500 GeV $\gamma\gamma\rightarrow\gamma\gamma$ plot applies to the others.