Measurement of the integrated luminosities of the data taken by BESIII at √ s = 3.650 and 3.773 GeV

Data sets were collected with the BESIII detector at the BEPCII collider at the center-of-mass energy of √ s = 3.650 GeV during May 2009 and at √ s = 3.773 GeV from January 2010 to May 2011. By analyzing the large angle Bhabha scattering events, the integrated luminosities of the two data sets are measured to be (44.49±0.02±0.44) pb −1 and (2916.94±0.18±29.17) pb −1 , respectively, where the first error is statistical and the second error is systematic.