“We’re not trying to find the chairman [with] hookers. . . . This is not a revenge business. I’m trying to figure out what’s going on.” The day after Paul Singer’s hedge fund, Elliott Management Corp., disclosed it had increased its stake in aluminum-parts manufacturer Arconic to more than 10 percent, its private investigators hit the pavement. It was January 26, 2017. The two sleuths, employed by Berkeley Research Group, were knocking on the doors of neighbors of Klaus Kleinfeld, Arconic’s then-CEO, in suburban Westchester County, New York.