# May 1 Colloquium

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**Walt Ogburn**, Kavli Institute for Particle Astrophysics and Cosmology, Stanford

*BICEP2 and The Echoes of Cosmic Inflation
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Host: Jim Brau

The BICEP2 team has announced the detection of degree-scale B-mode polarization of the CMB, consistent with the imprint of inflationary gravitational waves created an instant after the big bang. The telescope is a compact refractor with a 26 cm aperture and 512 antenna-coupled TES bolometers observing at 150 GHz (2 mm). BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square degrees was observed to a depth of 87 nK-degrees in Stokes Q and U. We have just announced an excess of B-mode power over the base lensed-LCDM expectation in the range 30<l<150, inconsistent with the null hypothesis at a significance of >5σ. The observed B-mode power spectrum is well fit by a lensed-LCDM + tensor theoretical model with tensor/scalar ratio r=0.20+0.07-0.05, with r=0 disfavored at 7.0σ.