Abstract
We have estimated the sensitivity to the anomalous couplings of the γγγZ vertex in the γγ → γZ scattering of the Compton backscattered photons at the CLIC. Both polarized and unpolarized collisions at the e+e− energies 1500 GeV and 3000 GeV are addressed, and anomalous contributions to helicity amplitudes are derived. The differential and total cross sections are calculated. We have obtained 95% C.L. exclusion limits on the anomalous quartic gauge couplings (QGCs). They are compared with corresponding bounds derived for the γγγZ couplings via γZ production at the LHC. The constraints on the anomalous QGCs are one to two orders of magnitude more stringent that at the HL-LHC. The partial-wave unitarity constraints on the anomalous couplings are examined. It is shown that the unitarity is not violated in the region of the anomalous QGCs studied in the paper.
Highlights
Z γγγZ which can be reached at the CLIC using both polarized and unpolarized photon beams
One can obtain from eq (3.6) that the anomalous contribution to the unpolarized total cross section is proportional to the coupling combination 3g12 − 4g1g2 + 4g22, provided terms proportional to m2Z /s 1 are
We have shown that such a process provides an opportunity of searching for the anomalous quartic neutral gauge couplings for the γγγZ vertex at the CLIC
Summary
It is appropriate to describe the anomalous γγγZ interaction by means of an effective Lagrangian. Given parity is conserved and gauge invariance is valid, there are only two independent operators with dimension 8. This Lagrangian contains no derivatives of the Z boson field (correspondingly, no p4 in the momentum space), that simplifies a derivation of Feynman rules for the γγγZ vertex. The Feynman rules for the effective anomalous vertex, resulting from the Lagrangian (2.1), are given by [36]. Electromagnetic gauge invariance results in equations pμ Pμνρα = pν2Pμνρα = pρ3Pμνρα = 0. To calculate helicity amplitudes for the process (1.1), one has to make the replacement p3 → −p3 in the Feynman rules for the γγγZ vertex given by eqs. To calculate helicity amplitudes for the process (1.1), one has to make the replacement p3 → −p3 in the Feynman rules for the γγγZ vertex given by eqs. (2.10), (2.11), and (A.1)–(A.11)
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