New physics in e + e − → Zγ at the ILC with polarized beams: explorations beyond conventional anomalous triple gauge boson couplings

Abstract

One of the most-studied signals for physics beyond the standard model in the production of gauge bosons in electron-positron collisions is due to the anomalous triple gauge boson couplings in the Zγ final state. In this work, we study the implications of this at the ILC with polarized beams for signals that go beyond traditional anomalous triple neutral gauge boson couplings. Here we report a dimension-8 CP-conserving ZγZ vertex that has not found mention in the literature. We carry out a systematic study of the anomalous couplings in general terms and arrive at a classification. We then obtain linear-order distributions with and without CP violation. Furthermore, we place the study in the context of general BSM interactions represented by e + e − Zγ contact interactions. We set up a correspondence between the triple gauge boson couplings and the four-point contact interactions. We also present sensitivities on these anomalous couplings, which will be achievable at the ILC with realistic polarization and luminosity.

On polarization parameters of spin-1 particles and anomalous couplings in $$e^+e^-\rightarrow ZZ/Z\gamma $$ e + e - → Z Z / Z γ

“…The neutral sector of the anomalous vertices discussed in [6] include Z Z Z, Z Zγ , and Z γ γ interactions and have been widely studied in the literature [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] in the context of different collider; e + e − collider [11][12][13][14][15][16], hadron collider [17][18][19], both e + e − and hadron collider [20][21][22], eγ collider [23][24][25] and γ γ collider [26]. For these effective anomalous vertices one can write an effective Lagrangian and they have been given in [12,13,21,23] up to differences in conventions and parametrizations.…”

“…Further, the terms corresponding to h V 2 and h V 4 are of mass dimension-8, while the others are dimension-6 in the Lagrangian. In [16] the authors have pointed out one more possible dimension-8 CP-even term for Z γ Z vertex, given by…”

“…To put simultaneous limits on all the form factors one would need as many observables as possible, like differential rates, kinematic asymmetries, etc. A set of asymmetries with respect to the initial beam polarizations has been considered [11,[13][14][15][16]21,[23][24][25] at the e + e − and eγ colliders. References [11,15,16,23] also include CP-odd asymmetries made out of the initial beam polarizations alone, which are instrumental in putting strong limits on CP-odd form factors.…”

Anomalous triple gauge boson couplings in ZZ production at the LHC and the role of Z boson polarizations

“…The anomalous neutral triple gauge boson couplings in Eq. (1) have been widely studied in the literature for various colliders: in e + e − collider [7,9,[17][18][19][21][22][23][24][25], eγ collider [10,15,16], γγ collider [20], hadron collider [8,12,14,26,27] and both e + e − and hadron collider [6,11,13]. On the experimental side, the anomalous Lagrangian in Eq.…”

On the choice of beam polarization in $$e^+e^-\rightarrow ZZ/Z\gamma $$ e + e - → Z

“…The anomalous couplings among the neutral gauge boson have been studied earlier with unpolarized beams in [31][32][33][34][35][36][37][38][39] as well as with polarized beams in [15][16][17]19,[40][41][42][43][44][45]. Some of these studies have used given beam polarizations to enhance the sensitivity of observables, while others have used two different sets of beam polarizations to construct the observables.…”