  Cosmic Microwave Background (CMB) is an important probe for understanding the
inflationary era of the Universe. We consider the Perturbed Power Law (PPL)
model of inflation which is a soft deviation from Power Law (PL) inflationary
model. This model captures the effect of higher order derivative of Hubble
parameter during inflation, which in turn leads to a non-zero effective mass
$m_{\rm eff}$ for the inflaton field. The higher order derivatives of Hubble
parameter at leading order sources constant difference in the spectral index
for scalar and tensor perturbation going beyond PL model of inflation. PPL
model have two observable independent parameters, namely spectral index for
tensor perturbation $\nu_t$ and change in spectral index for scalar
perturbation $\nu_{st}$ to explain the observed features in the scalar and
tensor power spectrum of perturbation. From the recent measurements of CMB
power spectra by WMAP, Planck and BICEP-2 for temperature and polarization, we
estimate the feasibility of PPL model with standard $\Lambda$CDM model.
Although BICEP-2 claimed a detection of $r=0.2$, estimates of dust
contamination provided by Planck have left open the possibility that only upper
bound on $r$ will be expected in a joint analysis. As a result we consider
different upper bounds on the value of $r$ and show that PPL model can explain
a lower value of tensor to scalar ratio ($r<0.1$ or $r<0.01$) for a scalar
spectral index of $n_s=0.96$ by having a non-zero value of effective mass of
the inflaton field $\frac{m^2_{\rm eff}}{H^2}$. The analysis with WP+ Planck
likelihood shows a non-zero detection of $\frac{m^2_{\rm eff}}{H^2}$ with
$5.7\,\sigma$ and $8.1\,\sigma$ respectively for $r<0.1$ and $r<0.01$. Whereas,
with BICEP-2 likelihood $\frac{m^2_{\rm eff}}{H^2} = -0.0237 \pm 0.0135$ which
is consistent with zero.

Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology