Speaker
Description
The state of polarization is encoded in the elements of density matrix and for a massive spin-one particle the density matrix can be parametrized in terms of 8 independent parameters called polarization parameters. We show how the polarization parameters of the $Z$ boson can be used to study the new physics interaction at the $ZZH$ vertex at future $e^+e^-$ colliders and at the LHC. We analytically calculate the 8 polarization parameters using the spin density matrix of the $Z$ boson and estimate bounds on the anomalous $ZZH$ couplings by constructing angular asymmetries from the $Z$ boson decay leptons, which are related to the polarization observable. Taking into account possible longitudinal beam polarization at two different center of mass energies, we find that oppositely polarized beams at 500 GeV c.m. energy provides tighter bounds on the couplings than the same sign polarized and unpolarized beams. We find that most of the 1σ limits are of the order of a few times $10^{−3}$ for 14 TeV LHC with integrated luminosity of 1000 fb$^{−1}$ and for 500 GeV $e^+e^-$ colliders with oppositely polarized beams.
| First author | Priyanka Sarmah |
|---|---|
| sarmahpriyanka07@gmail.com | |
| Collaboration / Activity | IIT Bombay |
