Physicists² in Syracuse University's College of Arts and Sciences have confirmed the existence of two rare pentaquark states. Their discovery, which has taken place at the CERN Large Hadron Collider (LHC) in Geneva, Switzerland, is said to have major implications for the study of the structure of matter. It also puts to rest a 51-year-old mystery, in which American physicist¹ Murray Gell-Mann famously posited³ the existence of fundamental subatomic constituents⁵ called quarks, which form particles such as protons. In 1964, he said that, in addition to a constituent⁴ with three quarks, there could be one with four quarks and an anti-quark, known as a "pentaquark." Until now, the search for pentaquarks has been fruitless.

 

"The statistical⁶ evidence of these new pentatquark states is beyond question," says Sheldon Stone, Distinguished⁷ Professor of Physics, who helped engineer the discovery. "Although some positive evidence was reported around 10 years ago, those results have been thoroughly⁸ debunked⁹. Since then, the LHCb [Large Hadron Collider beauty] collaboration¹⁰ has been particularly deliberate in its study."

 

In addition to Stone, the research team includes other physicists with ties to Syracuse: Tomasz Skwarnicki, professor of physics; Nathan Jurik G'16, a Ph.D. student; and Liming Zhang, a former University research associate who is now an associate professor at Tsinghua University in Beijing, China.

 

Liming, in fact, is presenting the findings at a LHCb workshop on Wednesday, July 22, at CERN. 

 

Stone credits Gell-Mann, a Nobel Prize-winning scientist who spent much of his career at Caltech, for postulating¹¹ the existence of quarks, which are fractionally charged objects that make up matter. "He predicted that strongly interacting particles [hadrons] are formed from quark-antiquark pairs [mesons] or from three quarks [baryons]," Stone says. "This classification scheme, which has grown to encompass¹² hadrons with four and five quarks, underscores the Standard Model, which explains the physical make-up of the Universe."

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