Our Informal Science Education team’s latest study made quite a splash, landing us on the cover of a special edition of the journal Symmetry. This pioneering investigation at Jefferson Lab seeks to illuminate the origins of hadron mass. It is the lab’s high-intensity accelerator that is spearheading these revolutionary discoveries. It builds upon almost three decades of data to investigate the puzzling mystery of how protons, neutrons and other particles get their mass. Like all complex topics, physicists are immersing themselves in this one. Their findings will have significant implications for the broader field of particle physics.
The underlying analysis relies on data gathered at Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF). This facility provides high-intensity electron and photon beams with energies up to 12 GeV, focused on nuclear materials. This world-class facility offers a great opportunity to observe the strong interactions that give particles mass. The discoveries provide new insights into underlying physics. They further shed light on the state of visible matter in the universe.
High-Intensity Accelerator Insights
Jefferson Lab’s new, high-intensity accelerator is key to this new frontiers exploration of hadron mass. It creates intense beams of electrons and photons, which collide with nuclear targets—enabling a rich experimental program to produce new data. Scientists have crunched almost three decades of experimental data. This enormous effort has come together to give them a holistic picture of how hadron mass is generated.
This study is focused on the CEBAF Large Acceptance Spectrometer for 12 GeV (CLAS12). This complex three-dimensional detector is located in Experimental Hall B. What makes CLAS12 truly special is its ability to track a wide variety of particles produced when electrons scatter from protons. The design allows for arbitrary emission angles of particles over a large solid angle. This is a huge improvement for the accuracy and consistency of the data being collected.
Victor Mokeev, a senior physicist in the study, details the need to understand the mechanism of hadron mass generation. He sees this understanding as paramount for moving the field forward. He notes that this work deepens our comprehension of why protons and neutrons have the masses that they do. It’s doing so with more than 98% accuracy. This broader view would reorient how physicists think about matter’s fundamental constituents.
The Nature of Hadron Mass
The study delves into the complex ways in which protons acquire their mass. This mass mainly arises from the strong interactions between their three dressed quarks. These collisions produce a center of mass energy of nearly 1 GeV for protons. In addition, the varied range of excited states of protons from 1.0 to 3.0 GeV were uncovered in the study along with other findings. Her robust, nuanced investigation offers a surprising glimpse. Hadron mass does not arise only from the constituent quark masses, but more significantly from the strong quark interactions.
In quantum chromodynamics (QCD), quarks gain their effective mass via the Higgs mechanism. The results raise the possibility that the dominant part of real-world matter’s mass comes from sources beyond the Higgs. This beautiful, profound realization is an absolutely crucial turning point in understanding how matter acts at the very bottommost layer.
Gluons, the glue holding quarks together and the carriers of the strong force that binds them, are essential to this interaction. They self-interact, an internal property with profound implications on the nature of matter in the universe. Physicists speculate that in an alternate universe without gluon self-interaction, formed stars would fall apart. This change would have drastic effects on the creation and maintenance of observable matter.
Progress Through Collaboration
The analysis shows how important is the combined effort of specialists from various disciplines to study hadron mass. It combines experimental data with phenomenological models and theoretical approaches. This synergy is essential for advancing knowledge in particle physics, as researchers strive to uncover the underlying principles governing matter’s behavior.
In the last ten years, immense progress has been made to understand this prevailing slice of the universe’s visible mass. Ongoing research at Jefferson Lab is a testament to this advancement. It showcases just how high-intensity accelerators can help us to further explore more complicated and intricate physical phenomena. As scientists continue to explore the intricacies of hadron mass, future discoveries may further illuminate fundamental questions about the nature of reality.