Lewis Alexander, a former Treasury Department official, is joining Nomura as managing director and chief economist of its US division. Mr. Alexander had been a counselor to Treasury Secretary Timothy Geithner before stepping down this year.  Previously, he had been Citigroup’s chief economist for nine years. He had earlier worked as a senior economist at the Federal Reserve and the Commerce Department.  A graduate of Stanford University, Alexander received a doctorate in economics from Yale University. He will be based in New York, leading a team of five economists.  He will report jointly to Jens Nordvig, head of Americas Fixed Income Research and Paul Sheard, the firm’s global chief economist. [Dealbook, 9/19/11]