Impact of particle production during inflation on the CMB detection

This work focuses on particle production described by a nonminimally coupled model during inflation. In this model, three parameters determine the characteristic frequency and strength of the induced gravitational waves (GWs). Considering the impact of particle production on inflation, we identify the parameter values that generate the strongest GWs without violating the slow-roll mechanism at the CMB scale. However, even with such extreme parameters, the power spectrum of induced GWs is only about three thousandths of that of primordial GWs. This contribution remains insignificant when identifying the primary source of the detected CMB B-mode polarization. Furthermore, when our results are integrated with the constraints driven by P+ACT+LB+BK18, the contribution of induced GWs at CMB scales becomes negligible. In contrast, their impact on the scalar spectral index $n_s$ proves significant. For a range of parameter values, the Starobinsky inflation model yields predictions for $n_s$ that are consistent with the measurements obtained from P+ACT+LB+BK18.