OAKLAND, Calif., Jan. 13 — At least three advanced diagnostic tests suggest that an experiment at the Brookhaven National Laboratory has cracked open protons and neutrons like subatomic eggs to create a primordial form of matter that last existed when the universe was roughly one-millionth of a second old, scientists said here on Tuesday. The hot, dense substance, called a quark-gluon plasma, has managed to generate intense disputes in the 15 years or so in which scientists have pursued it. In 2000, a major European laboratory claimed that it had, for the first time, liberated particles called quarks from where...