Measuring the Higgs-vector boson couplings at lineare+e−collider

Abstract

We estimate the accuracy with which the coefficient of the CP even dimension six operators involving Higgs and two vector bosons (HV V ) can be measured at linear e + e − colliders. Using the optimal observables method for the kinematic distributions, our analysis is based on the five different processes.First is the W W fusion process in the t-channel (e + e − →ν e ν e H), where we use the rapidity y and the transverse momentum p T of the Higgs boson as observables. Second is the ZH pair production process in the s-channel, where we use the scattering angle of the Z and the Z decay angular distributions, reproducing the results of the previous studies. Third is the t-channel ZZ, fusion processes (e + e − → e + e − H), where we use the energy and angular distributions of the tagged e + and e − . In the fourth, we consider the rapidity distribution of the untagged e + e − H events, which can be approximated well as the γγ fusion of the bremsstrahlung photons from e + and e − beams. As the last process, we consider the single tagged e + e − H events, which probe the γe ± → He ± process. All the results are presented in such a way that statistical errors of the constraints on the effective couplings and their correlations are read off when all of them are allowed to vary simultaneously, for each of the above processes, for m H = 120 GeV, at √ s = 250 GeV, 350 GeV 500 GeV and 1 TeV, with and without e − beam polarization of 80%. We find for instance that the HZZ and HW W couplings can be measured with 0.6% and 0.9% accuracy, respectively, for the integrated luminosity of L = 100 fb −1 at √ s = 250 GeV, 350 GeV and L = 500 fb −1 at √ s = 500 GeV, 1 TeV, for the luminosity uncertainty of 1% at each energy. We find that the luminosity uncertainty affects only one combination of the non-standard couplings which are proportional to the standard HW W and HZZ couplings, while it does not affect the errors of the other independent combinations of the couplings. As a consequence, we observe that a few combinations of the eight dimension six operators can be constrained as accurately as the two operators which have been constrained by the precision measurements of the Z and W boson properties.

Investigating perturbative unitarity in the presence of anomalous couplings

“…The operators O BW and O Φ,1 have a tree level effect on precision electroweak observables and therefore are subject to very strict constraints [14]. Hence we do not constrain these operators in our analysis.…”

“…On comparing with the effective Lagrangian given in equation (2), we can express the anomalous couplings as a linear combination of the coefficients f i (see reference [13] and [14]). Below we give relations of TGC and QGC with the coefficients of the above mentioned dimension six operators:…”

“…Vector boson scattering has drawn a lot of attention earlier and many works exist in the literature that discuss the gauge boson scattering and unitarity problems [12]. The anomalous gauge and gauge-Higgs couplings and their limits in various models as well as in modelindependent approach have also been studied in various papers [13][14][15][16][17][18][19][20][21].…”

Measuring anomalous couplings inH→WW*decays at the International Linear Collider

“…where The effects of dimension-six operators in the effective Lagrangian were considered in [11]. of rotation in the direction of the W + momentum) is given by…”

Role of polarization in probing anomalous gauge interactions of the Higgs boson

“…Note: During the last stages of finalising our manuscript, a paper dealing with related issues containing a very detailed analysis [75] on probing the coefficients of the CP-even, dimension 6 operators in the anomalous V V H vertices has appeared.…”