Physicists find signs of pentaquark states and new matter

Until recently, all hadrons could be understood as combinations of a quark and an antiquark, like the J/psi, or combinations of three quarks, like the proton. Despite this, it has long been suspected that other quark combinations are possible—what amounts to new forms of matter.

Sometimes a bump in the data is a wonderful new thing, and sometimes it is just a bump. Theorists at the University of Pittsburgh and Swansea University have shown that recent experimental results from the CERN collider give strong evidence for a new form of matter.

Physicists have examined a heavy particle called a Lambda b that decays to lighter particles, including the familiar proton and the famed J/psi, discovered in 1974.

To come up with a convincing explanation for each observation, the new effort integrates the CERN data with those from other experiments from 2018 and 2019.

Physicist Tim Burns of Swansea in Wales said, “We have a model that explains the data beautifully, and for the first time, incorporates all the experimental constraints. The explanation requires the existence of several new particles that consist of four quarks and one antiquark, called “pentaquarks. The research also indicates that the pentaquarks are just at the threshold for being observed at other laboratories.”

“There is no other way to interpret the data—pentaquark states must exist. The conclusion raises the possibility that other pentaquarks are possible and that a whole new class of matter is at the cusp of being discovered.”

Journal Reference:

1. T. J. Burns et al., Production of Pc states in Λb decays, Physical Review D (2022). DOI: DOI: 10.1103/PhysRevD.106.054029