Rice physicists play role in new discovery from Fermilab

Prelude to the Higgs: A work for two bosons in the key of Z
Rice physicists play role in new discovery from Fermilab’s DZero experiment

BY JADE BOYD
Rice News staff

Physicists from the DZero collaboration at Fermi National Accelerator Laboratory in Batavia, Ill., this week announced the observation of a key pairing of subatomic particles called “Z bosons.” The subatomic, force-carrying particles were produced at Fermilab’s Tevatron particle accelerator. The multinational DZero collaboration consists of more than 600 scientists, including several from Rice’s Bonner Nuclear Laboratory.

	MARJORIE CORCORAN

“The observation of a pair of simultaneously produced Z bosons is an exciting discovery,” said DZero member Marjorie Corcoran, professor of physics and astronomy at Rice, who just finished a yearlong sabbatical at Fermilab in July. “This is the last diboson pair to be observed, and Rice faculty and graduate students have made important contributions to the observation and study of these diboson pairs.”

Corcoran said the ZZ boson pair is one of several types of subatomic particle pairs called “dibosons” that are predicted by prevailing subatomic theories.

The properties of the ZZ boson pair make its discovery an essential prelude to finding or excluding the Higgs boson, an elusive particle that physicists expect to find if prevailing theories about the interactions of subatomic particles are correct. The search for the Higgs boson is ongoing at Fermilab’s Tevatron, and it is also a prime target of the Large Hadron Collider, a much larger particle accelerator that is slated to go on line in Europe this fall.

DZero officials say the observation of the ZZ connects to the search for the Higgs boson in several ways. The process of producing the ZZ is very rare, and hence, difficult to detect. The rarest diboson processes after ZZ are those involving the Higgs boson, so seeing ZZ is an essential step in demonstrating the ability of the experimenters to see the Higgs.

The DZero scientists searched for the ZZ pairing among nearly 200 trillion proton-antiproton collisions that occurred in the Tevatron. The physicists used two analyses to look for telltale signs of the rare Z particles. One method looked for one Z decaying into electrons or muons and the other decaying into neutrinos. The second method looked for the extremely rare occurrence of both Z particles decaying into electrons or muons. Just three of these distinctive events were observed.