BERLIN   A massive fire at a research center in western Germany has forced authorities to indefinitely delay the test phase of a billion euro particle accelerator, officials said on Thursday. The blaze broke out early morning at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, triggering a major response from firefighters. A towering plume of smoke could be seen from several kilometers away. Christian Wagner, operations manager for the Darmstadt fire department, told local media