Gravity: Its Omnipresence in the Observable Universe
Gravity's influence is undeniably pervasive in the observable universe. Its effects are manifested as synchronized orbits of moons around planets, trajectories of comets altered due to gravitational pulls of massive stars, and the majestic spirals of enormous galaxies. These phenomena underline gravity's role on a grand scale of matter.
Probing the Quantum Realm: A Breakthrough in Nuclear Physics
A ground-breaking research conducted at the Thomas Jefferson National Accelerator Facility of the U.S. Department of Energy has leveraged a method connecting gravitational theories to interactions between the smallest particles of matter. This study has for the first time, shed light on the distribution of force inside a proton, providing a detailed description of the shear stress that the force can exert on the quark particles that constitute it. The findings were recently published in the Reviews of Modern Physics.
Volker Burkert, the principal author and scientist at Jefferson Lab, revealed that the measurement provides insights into the environment experienced by the constituent elements of the proton, which comprises three quarks bound together by a strong force.
The Intrinsic Force of Protons
To extract a quark from a proton, an equivalent force of four tons would have to be applied. Nature, however, does not allow this because of a property known as 'colour'. Quarks are mixed in the proton with three different colours to make it appear colourless from the outside, a prerequisite for its existence in space. Attempting to extract a coloured quark would produce a colourless quark/antiquark pair, a meson.
Mapping the Distribution of Force within the Proton
Nuclear physicists at Jefferson Lab have mapped the force distribution within the proton using a structure that connects to gravity. This discovery is only the second of the proton's mechanical properties to be measured. This includes its internal pressure, mass distribution, angular momentum, and shear stress. This achievement was made possible through a half-century-old prediction and data collected over two decades.
In the 1960s, it was theorized that if nuclear physicists could observe how gravity interacts with subatomic particles, such experiments could directly reveal the mechanical properties of the proton. However, this was an arduous task due to the huge difference in orders of magnitude between the gravitational and electromagnetic force.
The Role of CEBAF Experiments
Decades-old data from experiments conducted with the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab, a facility used by the DOE Office of Science, played a crucial role in this research. A typical CEBAF experiment would entail an energetic electron interacting with another particle, exchanging an energy packet and an angular momentum unit called a virtual photon. The electron's energy determines which particles it interacts with and their response.
In these experiments, a force far greater than the four tons required to extract a quark/antiquark pair was applied to the proton by a highly energetic electron beam interacting with it in a target of liquefied hydrogen.
Deep Virtual Compton Scattering (DVCS)
According to Latifa Elouadhriri, a Jefferson Lab staff scientist and co-author of the study, the research program was developed to comprehensively study deep virtual Compton scattering (DVCS), where an electron exchanges a virtual photon with itself. In the final state, the proton remained the same but recoiled, producing a real, highly energetic photon, plus the scattered electron.
It was discovered that this specific process - DVCS - can be linked to how gravity interacts with matter. A general version of this connection was theorized in the book on Einstein's general theory of relativity titled “Gravitation” by Charles W. Misner, Kip S. Thorne, and John Archibald Wheeler.
Theoretical Breakthrough and Future Research
Three decades later, the theorist Maxim Polyakov followed up on this idea, laying the theoretical groundwork that connects the DVCS process and gravitational interaction. According to Burkert, this theoretical breakthrough bridged the relationship between the measurement of deep virtual Compton scattering and the gravitational form factor, which they could use for the first time.
The researchers aim to work on extracting the information they need from existing DVCS data to enable the first determination of the proton's mechanical size. They also hope to benefit from new experiments with higher statistics and energy.
Conclusion
Amazed by the plethora of new theoretical efforts detailed in hundreds of publications that have begun to exploit this discovery to explore the proton's mechanical properties, Burkert and Elouadhriri conclude, "We are now in a new era of discoveries with the recently published Long-Term Plan for Nuclear Science, this will be a significant pillar in the development of new structures and detectors."
The exploration of gravity's profound influence on the quantum realm is a testament to the fascinating journey of scientific discovery, an adventure that FreeAstroScience.com invites you to join, as we strive to unravel the mysteries of our incredibly vast universe.
Post a Comment