nuclear physics pion reaction breakthrough

Nuclear Physics Breakthrough: New Calculation Links Disparate Pion Reactions

Introduction to the Groundbreaking Lattice QCD Calculation

A physicist at the early stage of their career has made a mathematical breakthrough linking timelike and spacelike from factors, offering new pathways to understanding force. This innovative lattice QCD calculation establishes a connection between two  previously unrelated  reactions involving the pion, the lightest particle influenced by the strong interaction.

Felipe Ortega-Gama's Early research and Mentorship at Jefferson Lab

Undergraduate Research and Mentorship at Tecnológico de Monterrey

During his undergraduate studies at Tecnológico de Monterrey, Mexico, Felipe Ortega-Gama participated in the U.S. Department of Energy's Science Undergraduate Laboratory Internships program at the Thomas Jefferson National Accelerator Facility. Under the mentorship of Raúl Briceño, a staff scientist at the lab's Center for Theoretical and Computational Physics and a professor at Old Dominion University, Ortega-Gama contributed to research in theoretical physics.

Introduction to Quantum Chromodynamics (QCD)

Under the guidance of Raúl Briceño, he was introduced to quantum chromodynamics (QCD), the theoretical framework describing the strong interaction. This force is responsible for binding quarks and gluons into protons, neutrons, and other hadronic particles. Researchers use lattice QCD, a numerical approach to solving QCD equations, to generate predictions that aid in analyzing experimental data on hadronic interactions.

The Pivotal Moment in Ortega-Gama's QCD Journey

A Moment of Realization for Ortega-Gama

"Raúl Briceño presented a plot displaying both theoretical calculations and experimental measurements of various particle masses, all closely aligned," Ortega-Gama recalled amazed by the precision of these predictions. "That was the moment I realized that QCD could accurately forecast particle properties with remarkable accuracy."

This pivotal moment sparked Ortega-Gama's interest in QCD and led him to Jefferson Lab. Despite the impressive agreement between theory and experiment in the plot, physicists have yet to fully harness QCD to compute all possible properties of quarks, gluons, and the particles they compose.

Advancing QCD with Lattice Calculations

Ortega-Gama's Ph.D. Research at William & Mary

During his Ph.D. studies at William & Mary, Ortega-Gama leveraged the university's strong collaboration with Jefferson Lab to resume working with Raúl Briceño and engage with Jozef Dudek, a senior scientist holding a joint appointment at both institutions, to deepen his understanding of QCD.

Breakthrough in Pion Reactions: Unifying Spacelike and Timelike processes

Orgega-Gama, as the lead author of a lattice QCD study published in Physical Review D, uncovered a fundamental connection between two pion-mediated processes previously thought to be distinct.

Computational Synergies in QCD Analysis

Understanding Spacelike vs. Timelike processes

The spacelike process involves an electron being scattered off a pion, while the timelike process occurs when an electron and its antiparticle collide and produce two pions upon annihilation.

"Although these two processes appear distinct at first glance," Dudek explained, "they are governed by the same fundamental physics. Their Feynman diagrams are essentially rotated versions of one another. Felipe's work demonstrates their connection through a unified calculation at the level of quarks, and gluons."

Unifying Spacelike and Timelike Reactions

This computational approach successfully unifies the description of both spacelike and timelike processes, highlighting the inherent interconnectivity of QCD-governed reactions. While experimental observations previously hinted at this relationship, it is now firmly supported by mathematical validation.

The Challenges and Innovations of QCD Calculation

Addressing Computational Constraints in QCD Research

Ortega-Gama's prior research provided the foundation for this groundbreaking calculation. In experimental settings, post-collision particles travel outward indefinitely until they are detected, effectively reaching a 'theoretical infinity' beyond the strong interaction's influence. In numerical calculations, however, computational constraints necessitate confining these particles within a finite volume, only marginally larger than the strong interaction's effective range.

"This presents a challenge—how can we effectively relate the constrained results obtained from a finite computational box to the infinite-volume outcome observed in experimental detectors?" Ortega-Gama explained.

Collaboration and Advancements in QCD Formalism

Developing a Mathematical Formalism for Finite-Volume Calculations

Briceño, Dudek and other experts in the field have developed a mathematical formalism—an analytical approach that ensures finite-volume numerical calculations can be extended to predict infinite-volume outcomes.

Ortega-Gama's Role in Advancing QCD Formalism

Ortega-Gama, working alongside Briceño, advanced this formalism to enable the calculation of form factors for hadrons that, in contrast to the pion, decay via the strong interaction.

Building a Strong Research Foundation through Mentorship

Collaborative Work with Briceño and Dudek

"Felipe had already produced remarkable formalism papers before this publication," Dudek noted. "In our field of lattice QCD, the most accomplished researchers are those who excel in both theoreticla formalism and numerical computations. Felipe demonstrates exceptional skill in both domains at the highest level."

Weekly Collaboration and Knowledge Sharing

As Ortega-Gama's Ph.D. advisor, Dudek held weekly meetings with him throughout the project to refine calculations and exchange ideas.

Ortega-Gama said, "At each stage of the calculation, I could collaborate with him, allowing us to tailor the code to our study's specific needs."

Interrelations in Nuclear Physics: The Hadron Spectrum Collaboration

Leveraging Collaborative Research Resources

Senior members of the Hadron Spectrum (HadSpec) collaboration, Dudek and Briceño, contribute to lattice QCD computations of hadronic properties, with Ortega-Gama leveraging the collaboration's computational infrastructure.

Ortega-Gama noted that this project emerged through discussions with various members of the collaboration.

Contributions from Robert Edwards and Optimizing Codebases

HadSpec member Robert Edwards, a staff scientist at Jefferson Lab's Theory Center, has developed an extensive suite of codes that optimize lattice QCD calculations. Ortega-Gama utilized both this codebase and Edward's expertise in his research.

Advancing Career and Moving Forward in QCD Research

Ortega-Gama's Postdoctoral Role at UC Berkeley

As a result of these collaborations, Ortega-Gama has advanced to his current role as a postdoctoral scholar at the University of California, Berkeley, where he began in September 2024. He continues his work on QCD calculations alongside Briceño, now a professor at UC Berkeley.

The Role of Significant Research Projects in Career Advancement

"Having such a significant research project played a crucial role in easing the transition from Ph.D. student to postdoctoral scholar," Ortega-Gama remarked.

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supernova dark matter axion gamma ray detection

Could a Nearby Supernova Hold the Key to Solving the Dark Matter Mystery?

The Mystery of Dark Matter

The quest to uncover the universe's dark matter could reach its conclusion as early as tomorrow—if a nearby supernova offers the right conditions. For 90 years, astronomers have been puzzled by the elusive nature of dark matter, which constitutes 85% of the universe's mass yet remains invisible to telescopes. Current research focuses on the axion, a lightweight particle widely regarded as the leading candidate.

The Role of Axions in Dark Matter Research

Identifying Axions Through Supernova Gamma Rays

Researchers at the University of California, Berkeley, propose that axions could be identified almost instantly following the detection of gamma rays from a nearby supernova. If axions exist, they would be generated in vast numbers during the first 10 seconds of a massive star's collapse into a neutron star. These particles would then escape and convert into high-energy gamma rays within the star's powerful magnetic field.

The Challenge of Detecting Gamma Rays

At present, such a detection can occur only if the Fermi Gamma-ray Space Telescope, the only operational gamma-ray telescope in orbit, is oriented toward the supernova at the moment of its explosion. With the telescope's restricted field of view, the probability of this alignment is approximately 10%.

Implications of Gamma-Ray Detection

Determining the Mass of the QCD Axion

A single gamma-ray detection could precisely determine the mass of the axion, specifically the QCD axion, across a vast range of theoretical possibilities, including those under investigation in Earth-based experiments. Conversely, the absence of such a detection would rule out a significant portion of potential mass ranges, rendering many current dark matter searches obsolete.

The Need for a Nearby Supernova

The challenge lies in the fact that gamma rays must be sufficiently bright to detect, which requires the supernova to occur nearby—within the Milky Way or its satellite galaxies. However, such events are rare, with nearby stars exploding only every few decades. The most recent occurrence was in 1987, when a supernova erupted in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Although the Solar Maximum Mission gamma-ray telescope was directed toward this supernova, its sensitivity was insufficient to detect the predicted gamma-ray intensity, as analyzed by the UC Berkeley team.

"A modern gamma-ray telescope observing a supernova like 1987A could confirm or eliminate the existence of the QCD axion—a fascinating theoretical particle—over a vast range of parameter space," said Benjamin Safdi, UC Berkeley associate professor of physics and senior author of a paper published on November 19 in Physical Review Letters. "This includes nearly all parameter regions unreachable by laboratory methods and a considerable portion that laboratories are currently investigating, and it would happen within 10 seconds."

The Proposed GALAXIS Satellite Network

The Urgency of Detecting Axions

The researchers express concern that when the long-anticipated supernova occurs in the nearby universe, the opportunity to observe gamma rays produced by axions might be missed. To address this, they are collaborating with colleagues involved in gamma-ray telescope development to explore the possibility of deploying a fleet of satellites capable of monitoring the entire sky continuously. They have even proposed a name for this ambitious constellation of full-sky gamma-ray satellites: the GALactic Axion Instrument for Supernova, or GALAXIS.

The Risks of Missing the Opportunity

"We're all deeply concerned about the possibility of the next supernova occurring before the necessary instruments are in place," said Safdi. "Missing the chance to detect axions due to a supernova happening tomorrow would be a profound loss—such an opportunity may not arise again for another 50 years."

Safdi's co-researchers are graduate student Yujin Park and postdoctoral scholars Claudio Andrea Manzari and Inbar Savoray. Together, they are part of UC Berkeley's physics department and the Theoretical Physics Grou p at Lawrence Berkeley National Laboratory.

Understanding the QCD Axion

Dark Matter and the Search for Axions

Dark matter searches began by focusing on faint, massive compact halo object (MACHOs), which were expected to be spread throughout our galaxy and beyond. When MACHOs couldn't be detected, attention turned to theoretical elementary particles that should be ubiquitous and detectable in lab experiments on Earth. Yet, the hunt for weakly interacting massive particles (WIMPs) also yielded no results.

Axions and Their Role in Physics

The axion is currently the leading candidate for dark matter, a particle that seamlessly integrates into the standard model of physics while addressing several unresolved issues in particle physics.

Additionally, axions arise naturally from string theory, a theoretical framework for the universe's fundamental geometry, and could potentially reconcile gravity, which governs large-scale interactions, with quantum mechanics, which governs the microscopic.

According to Safdi, it appears nearly impossible to formulate a consistent theory that integrates gravity with quantum mechanics without including particles such as the axion.

The leading candidate for an axion, known as the QCD axion—so named after the prevailing theory of the strong face, quantum chromodynamics—hypothetically interacts with all forms of matter, albeit weakly, through the four fundamental forces: gravity, electromagnetism, the strong force (which binds atoms), and the weak force (which governs atomic decay).

One consequence is that in a powerful magnetic field, an axion should occasionally transform into an electromagnetic wave, or photon. This contrasts with the neutrino, a similarly lightweight, weakly-interacting particle, which only engages with gravity and the weak force, entirely disregarding the electromagnetic force.

Experimental Efforts and Simulations

Axion Detection in Laboratory Experiments

Experiments in laboratory settings, such as the ALPHA Consortium (Axion Longitudinal Plasma HAloscope), DMradion, and ABRACADABRA, all involving UC Berkeley researchers, utilize compact cavities that resonate like a tuning fork, enhancing the faint electromagnetic field or photon produced when a low-mass axion undergoes transformation in the presence of a strong magnetic field.

Supercomputer Simulations and Neutron Stars

Rather than focusing on distant galactic magnetic fields, the researchers investigated the generation of gamma rays by axions within the strong magnetic fields surrounding the star that produced them. Supercomputer simulations revealed that this process efficiently generates a burst of gamma rays, with intensity linked to the mass of the axion.

Neutron Stars as Axion Laboratories

The Role of Neutron Stars and Magnetars

Gamma ray burst should coincide with a burst of neutrinos from within the neutron star. However, this axion burst only lasts for 10 seconds following the formation of the neutron star, after which the production rate rapidly decreases, hours before the outer layers of the star begin to explode.

"This has prompted us to consider neutron stars as ideal locations for axion searches, effectively turning them into 'axion laboratories,'" Safdi explained. "Neutron stars offer many advantages. Not only are they incredibly hot, but they also possess some of the strongest magnetic fields in the universe. Magnetars, a type of neutron star, for instance, generate magnetic fields that are tens of billions of times stronger than anything we can produce in a laboratory. These intense magnetic fields help convert axions into detectable signals."

Setting Limits on Axion Mass

Two years ago, Safdi and his team established the most precise upper limit on the mass of the QCD axion, pegging it at roughly 16 million electron volts, which is about 32 times smaller than the electron's mass. This conclusion was drawn from analyzing the cooling rate of neutron stars, which would accelerate if axions were produced alongside neutrinos within these dense celestial objects.

The Future of Axion Research

Predictions and Opportunities for Gamma-Ray Detection

In their latest publication, the UC Berkeley team details the generation of gamma rays following a core collapse into a neutron star. Additionally, they utilize the lack of gamma ray detection from the 1987A supernova to set the most stringent constraints on the mass of axion-like particles, which differ from QCD axions in their lack of interaction with the strong force.

The researchers predict that detecting gamma rays enable them to determine the mass of the QCD axion, provided it exceeds 50 microelectron volts (μeV), roughly one 10-billionth of the electron's mass. A single observation could redirect ongoing experiments to verify the axion's mass, according to Safdi. Although a network of dedicated gamma-ray telescopes is the optimal solution for detecting gamma rays from a nearby supernova, a fortunate event with Fermi would be an even more advantageous scenario.

The Role of Fermi in Axion Research

The optimal scenario for detecting axions would be for Fermi to capture a supernova. However, Safdi notes that the probability of this hap pening is low. "But if Fermi were to observe it, we would be able to measure the axion's mass and interaction strength, providing us with the critical information about the axion. The signal would be highly reliable, as no ordinary matter could produce such an event," he said.

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