New Constraint on the Tensor-to-scalar Ratio from the Planck and BICEP/Keck Array Data Using the Profile Likelihood

We derive a new upper bound on the tensor-to-scalar ratio parameter $r$ using frequentist profile likelihood method. vary all relevant cosmological parameters of $\Lambda$CDM model, as well nuisance parameters. Unlike Bayesian analysis Markov Chain Monte Carlo (MCMC), our is independent choice priors. Using $Planck$ Public Release 4, BICEP/Keck Array 2018, CMB lensing, and BAO data, we find an limit $r<0.037$ at 95% C.L., similar to MCMC result $r<0.038$ for flat prior conditioned lowlEB covariance matrix.