A peak has been unambiguously detected in the cosmic microwave background ( CMB ) angular spectrum .
Here we characterize its properties with fits to phenomenological models .
We find that the TOCO and BOOM/NA data determine the peak location to be in the range 175–243 and 151–259 respectively ( both ranges 95 % confidence ) and determine the peak amplitude to be between \approx 70 ~ { } { and } ~ { } 90 \mu { K } .
By combining all the data , we constrain the full-width at half-maximum to be between 180 and 250 at 95 % confidence .
Such a peak shape is consistent with inflation-inspired flat , cold dark matter plus cosmological constant models of structure formation with adiabatic , nearly scale-invariant initial conditions .
It is inconsistent with open and defect models .