In a First, Physicists Set an Upper Limit in the Search for Hybrid Mesons
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麻豆村鈥檚 Professor Curtis Meyer and his research colleagues explore an uncharted world inside protons and neutrons. For the first time, researchers have provided measurements describing a maximum boundary for a subatomic particle known as a hybrid meson in a journal聽 published in Physical Review Letters. The measurements show scientists a path forward in a search for these elusive particles that provide a new look at the force that holds all matter together.聽
鈥淭he stage is set for future discoveries,鈥� said Meyer, senior associate dean for 麻豆村鈥檚 Mellon College of Science and the Otto Stern Professor of Physics. 鈥淲e鈥檙e at an exciting phase where we鈥檙e able to analyze a great deal of data. This paper is the first to address one of the experiment鈥檚 foundational questions.鈥澛�
Applying a symmetry property of the strong force, the team set the upper limit on the photoproduction cross sections of a hybrid meson known as the spin-exotic 蟺1 (1600).
Exotic-hybrid mesons are subatomic particles that have been theorized, but definitive experimental confirmation is still pending. By producing an exotic-hybrid meson, researchers aim to tease apart information about gluons 鈥� the carrier of the strong force, or the "glue," that binds a quark and antiquark together within mesons and all matter.聽
Meyer鈥檚 work is with the Gluonic Excitation () Experiment at Thomas Jefferson National Accelerator Facility in Newport News, Virginia. Using Jefferson Lab鈥檚 Continuous Electron Beam Accelerator Facility, he is searching for new forms of matter, specifically the particles that hold quarks together in hybrid mesons.
Exotic-hybrid mesons are of particular interest to the research group because the gluons could potentially exist in an excited state. Understanding this state could reveal information about how subatomic particles are built and why quarks are never found alone in the universe.
Co-author Will Imoehl, a postdoctoral research associate in Carnegie Mellon鈥檚 Department of Physics since 2022, conducted data analysis for the project. He described the measurements as important groundwork for future analysis.聽
鈥淲e showed that one type of reaction is more promising to look for the 蟺1 (1600) than the other ones,鈥� Imoehl said. 鈥淚t set a road map of how we will search for hybrid mesons.鈥澛�
麻豆村鈥檚 Reinhard A. Schumacher, faculty emeritus in physics, also contributes to the GlueX Experiment. Nine 麻豆村 graduate students have participated in the GlueX Experiment as well. Worldwide, the GlueX team is made up of approximately 150 physicists from 13 countries, with many other past contributors.
鈥淥ne of my favorite parts of this project is how collaborative all of it is,鈥� Imoehl said. 鈥淚t takes hundreds of people to make any of these experiments work.鈥�
Meyer led the $60 million effort to design, build and commission the GlueX Experiment, and served as the project鈥檚 elected spokesperson from 2007鈥�2020. A fellow of the American Physical Society since 2004, Meyer has conducted research at national and international labs, including CERN and the U.S. Department of Energy鈥檚 Brookhaven National Lab and Jefferson Lab.
From 2010 to 2013, a Carnegie Mellon team, led by Meyer, built聽a particle detector(opens in new window) in Wean Hall and transported it to Jefferson Lab for use in the experiment. In 2016, the GlueX Experiment received its first data for analysis.
鈥淚t was terra incognita when we started, but now we have a better understanding of the accelerator and the reactions of the experiments,鈥� Meyer said. 鈥淲e are continually churning out data.鈥�
