Particle physics research

NMSU Continues Particle Physics Research with Renewed DOE Grant

LAS CRUCES – Many people learn in elementary school that the main components that make up all matter on earth are protons, neutrons and electrons. However, the true foundations of atoms are smaller and much more enigmatic than the school narrative suggests.

The U.S. Department of Energy has renewed the $1.26 million grant allowing the Physics Department at New Mexico State University to continue uncovering the complex behaviors of quarks and gluons, the particles that form protons and neutrons (collectively called nucleons).

NMSU physics professors Stephen Pate and Vassilios Papavassiliou are involved in two ongoing experiments, SpinQuest and MicroBooNE, taking place at Fermi National Accelerator Laboratory near Chicago. Graduate student Samantha Sword-Fehlberg and postdoctoral researcher Lu Ren work on MicroBooNE while graduate research assistants Forhad Hossain, Dinupa Nawarathne, Harsha Arachchige and postdoctoral researcher Abinash Pun work on SpinQuest.

SpinQuest is, as you can imagine, on a quest to understand the “spin” of nucleons, a particular property of particles that mysteriously results from the behavior of their components. Spin, as Pate explained, is a property that makes them appear to be spinning when they are not. The spin of a particle, when combined with an electric charge, creates a magnetic field around the particle.

“Quarks and gluons conspire to create the spin of the proton,” Pate said, “but we don’t have a full understanding of how they do it.”

Gluons, which produce a powerful energy field that acts like a glue to hold quarks together, can create vanishing quark and antiquark pairs that are extremely elusive; they are formed by gluon energy but rapidly recombine, existing only temporarily. The behavior of these “marine quarks” – as physicists call them – could play a more complex role in generating the nucleon’s spin.

Other experiments have clarified that the spin of the nucleon does not arise from the mere spin of its constituents, raising the question of what is at stake. The team wants to see if sea quarks contribute to the spin of the nucleon by spinning around its center, like planets revolving around the sun.

“The SpinQuest experiment uses a high-energy proton beam from Fermilab’s main injector and a ‘polarized’ target made of frozen ammonia,” Papavassiliou said. The target is polarized by using a strong magnetic field to arrange the protons so that their spins are aligned, pointing in the same direction. As the proton beam and target protons collide, researchers look for quark and antiquark interactions that provide insight into their behavior within nucleons.

NMSU also participates in an international collaboration called MicroBooNE, which is short for Micro Booster Neutrino Experiment. This project brings together about 180 researchers from 36 institutions who are trying to understand the properties of the neutrino, another elusive elementary particle, but which does not constitute the atom.

“While much of the effort is devoted to studying the neutrino,” Papavassiliou said, “our group is focused on using a neutrino beam to study the internal structure of the proton.” He explains that neutrinos, although still mysterious, are sufficiently understood to be used as a probe for the properties of nucleons.

These nucleons reside in a 170 ton vessel of liquid argon which has a time projection chamber inside. The team uses sophisticated electronics to record the immense number of interactions that occur between the neutrino beam and the nucleons of the argon atoms.

According to Pate, this research has far-reaching applications for technological advancement, even if they are not immediately apparent. For example, MRI, commonly used in healthcare facilities, has capitalized on what we understand about particle behavior and interaction. Pate posits that once physicists are trained to understand these fundamental properties, they can use their learned skills to go out and invent new technologies that contribute to society.

“EYE ON RESEARCH” is provided by New Mexico State University. This week’s article was written by Jessica Brinegar of NMSU Marketing and Communications. She can be contacted at [email protected].

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