SACRAMENTO -- The California Public Employees' Retirement System, which poured about $1 billion into a troubled real estate deal, is in negotiations to keep a related loan default from turning into a bankruptcy. CalPERS, the nation's biggest public pension fund, and its partners acquired a controlling interest in 15,000 acres of undeveloped land in the Santa Clarita Valley early last year, before the meltdown in the housing market. The land, once owned by Newhall Land and Farming Co., was appraised at $2.6 billion at the time of the CalPERS investment but has dropped considerably in value since then. CalPERS chief...