High energy behaviour of gamma gamma to f f(bar) processes in SM and MSSM

TL;DR

This work analyzes the high-energy behavior of electroweak one-loop corrections to γγ → f f̄ in the SM and MSSM by computing leading logarithmic contributions and decomposing them into gauge, Yukawa, and SUSY sectors. It demonstrates that the dominant corrections follow Sudakov-like ∼ ln^2(s/M^2) and ∼ ln(s/M^2) structures, with significant angular-dependent terms from the γWW sector and pronounced tanβ- and Yukawa-driven enhancements in MSSM. By expressing the results as helicity amplitudes and translating them into polarized and unpolarized cross sections, the authors show observable deviations from Born predictions at future LC/CLIC energies, and clear distinctions between SM and MSSM, especially for t t̄ and b b̄ final states. The study emphasizes the experimental potential of γγ colliders to test the electroweak sector and highlights the need for two-loop calculations or resummation to accurately capture high-energy logarithmic effects.

Abstract

We compute the leading logarithms electroweak contributions to gamma gamma to f f(bar) processes in SM and MSSM. Several interesting properties are pointed out, such as the importance of the angular dependent terms, of the Yukawa terms, and especially of the $\tan^2β$ dependence in the SUSY contributions. These properties are complementary to those found in e+e- to f f(bar). These radiative correction effects should be largely observable at future high energy gamma gamma colliders. Polarized beams would bring interesting checks of the structure of the one loop corrections. We finally discuss the need for two-loop calculations and resummation.

Figures (12)

• Figure 1: SM diagrams contributing in the asymptotic regime of $\gamma\gamma\to f\bar{f}$, $Z$ sector (a), $W$ sector (b), Higgs sector (c).
• Figure 2: SUSY additional diagrams contributing in the asymptotic regime of $\gamma\gamma\to f\bar{f}$, Chargino and neutralino sector (a), SUSY Higgs sector (b).
• Figure 3: Angular distribution of the unpolarized $\gamma\gamma\to f\bar{f}$ cross section at 3 TeV; $l^+l^-$ (a), $t\bar{t}$ (b), $b\bar{b}$ (c); Born (solid), total SM (small dashed), total MSSM($\tan\beta=4$) (dotted), total MSSM($\tan\beta=40$) (large dashed).
• Figure 4: Angular distribution of the relative departure from the unpolarized Born $\gamma\gamma\to f\bar{f}$ cross section at 3 TeV due to electroweak radiative corrections; $l^+l^-$ (a), $t\bar{t}$ (b), $b\bar{b}$ (c); total SM (solid), total MSSM($\tan\beta=4$) (small dashed), total MSSM($\tan\beta=40$) (large dashed).
• Figure 5: The ratio $R_0$ for $\gamma\gamma\to l^+l^-$ versus the energy; SM (a), MSSM(b); all logarithmic terms (solid), leading terms only (small dashed), leading angular independent terms only(large dashed).