On 1 March 2001, the Tevatron Proton- antiproton (p p) collider at Fermilab near Chicago commenced its run 2. After run 1 (1992–1996), in which the collider had discovered the top quark, Tevatron had shut down for significant upgrades focused on improving the potential for finding the Higgs boson; the energies of the protons and antiprotons was bumped up to 0.98 TeV, and the number of collisions per second was increased by an order of magnitude (with further increases planned as the run continued). Even with the upgrades Tevatron was not guaranteed to find the Higgs. If the Higgs were too heavy (> 180 GeV), then the collisions would not have enough energy to produce a Higgs boson. If it were too light (< 140 GeV), then the Higgs would predominantly decay to pairs of bottom quarks—a signal that would be swamped by background events, and the Tevatron would not produce enough collisions to filter out the statistics. Nonetheless, the Tevatron was at the time the only operational particle collider that was sufficiently powerful to be capable of seeking the Higgs particle.