A MEASUREMENT OF THE DAMPING TAIL OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM WITH THE SOUTH POLE TELESCOPE

We present a measurement of the angular power spectrum of the cosmic\nmicrowave background (CMB) using data from the South Pole Telescope (SPT). The\ndata consist of 790 square degrees of sky observed at 150 GHz during 2008 and\n2009. Here we present the power spectrum over the multipole range 650 < ell <\n3000, where it is dominated by primary CMB anisotropy. We combine this power\nspectrum with the power spectra from the seven-year Wilkinson Microwave\nAnisotropy Probe (WMAP) data release to constrain cosmological models. We find\nthat the SPT and WMAP data are consistent with each other and, when combined,\nare well fit by a spatially flat, LCDM cosmological model. The SPT+WMAP\nconstraint on the spectral index of scalar fluctuations is ns = 0.9663 +/-\n0.0112. We detect, at ~5-sigma significance, the effect of gravitational\nlensing on the CMB power spectrum, and find its amplitude to be consistent with\nthe LCDM cosmological model. We explore a number of extensions beyond the LCDM\nmodel. Each extension is tested independently, although there are degeneracies\nbetween some of the extension parameters. We constrain the tensor-to-scalar\nratio to be r < 0.21 (95% CL) and constrain the running of the scalar spectral\nindex to be dns/dlnk = -0.024 +/- 0.013. We strongly detect the effects of\nprimordial helium and neutrinos on the CMB; a model without helium is rejected\nat 7.7-sigma, while a model without neutrinos is rejected at 7.5-sigma. The\nprimordial helium abundance is measured to be Yp = 0.296 +/- 0.030, and the\neffective number of relativistic species is measured to be Neff = 3.85 +/-\n0.62. The constraints on these models are strengthened when the CMB data are\ncombined with measurements of the Hubble constant and the baryon acoustic\noscillation feature. Notable improvements include ns = 0.9668 +/- 0.0093, r <\n0.17 (95% CL), and Neff = 3.86 +/- 0.42. The SPT+WMAP data show...