LHC’s Latest Hunt: Could Supersymmetry’s Elusive Squarks Finally Be Found?
In a groundbreaking development that could fundamentally rewrite our understanding of the universe, physicists at the Large Hadron Collider (LHC) are pushing the boundaries of experimental physics in their relentless pursuit of the elusive squark, a hypothetical particle predicted by theories of supersymmetry. This ambitious hunt, detailed in a recent publication in the European Physical Journal C, focuses on the possibility of these squarks, specifically those associated with the first two generations of matter, being the ultimate form of dark matter – the invisible scaffolding that holds galaxies together. The implications of such a discovery would be nothing short of revolutionary, offering a tantalizing glimpse into the universe’s hidden architecture and potentially unifying seemingly disparate fundamental forces. The sheer energy levels sustained within the LHC, the world’s most powerful particle accelerator, provide the unique environment necessary to recreate the conditions of the early universe, a crucible where such exotic particles might have been forged. This new analysis represents a significant refinement in the search strategies, targeting specific decay patterns that would signal the presence of these predicted supersymmetric partners to the known Standard Model particles.
The Standard Model of particle physics, while incredibly successful in describing the fundamental building blocks of matter and their interactions, leaves several profound questions unanswered. The nature of dark matter and dark energy, the hierarchy problem concerning the vast difference between the gravitational force and the other fundamental forces, and the lack of a unified theory encompassing all forces are just a few of the mysteries that have spurred theoretical physicists to look beyond the Standard Model’s confines. Supersymmetry, or SUSY, emerges as a compelling candidate for addressing these shortcomings. It postulates that for every known fundamental particle, there exists a heavier “superpartner” with a different spin. For quarks, the particles that make up protons and neutrons, their superpartners are called squarks. The excitement surrounding this particular search stems from the possibility that the lightest supersymmetric particle (LSP), a key prediction of many SUSY models, could indeed be a squark from the first or second generation of quarks.
This cutting-edge research capitalizes on the immense data sets generated by proton-proton collisions at the LHC. The LHC accelerates protons to nearly the speed of light, smashing them together with incredible energy. These collisions create a fleeting shower of exotic particles, many of which are unstable and decay almost instantaneously into more familiar particles. By meticulously analyzing the debris of these collisions, physicists can search for specific signatures that would indicate the production of new, undiscovered particles. The technique employed in this study involves looking for events characterized by a significant imbalance in momentum, often accompanied by a particular number of leptons (like electrons and muons) and energetic jets of particles. These characteristics are precisely what one would expect from the decay of a squark, which would then decay into other particles, including the hypothetical LSP, potentially carrying away a substantial amount of energy and momentum that would be unobserved in the detector.
The theoretical framework underpinning this experimental endeavor paints a picture where the universe’s fundamental constituents have a supersymmetric partner. In this shadowy realm, quarks have squarks, electrons have selectrons, and photons have photinos. The beauty of SUSY lies in its ability to elegantly address several persistent puzzles in physics. It can naturally explain the observed masses of fundamental particles, provide a mechanism for electroweak symmetry breaking, and, perhaps most significantly, offer a viable candidate for dark matter. The LSP, in many SUSY scenarios, is stable and interacts weakly with ordinary matter, making it an ideal candidate for the mysterious dark matter that dominates the universe’s mass-energy budget. The possibility that this LSP could be a squark specifically from the first two generations of quarks – up, down, charm, and strange quarks – has become a focal point for experimentalists.
The experimental challenge is immense, primarily due to the overwhelming background noise of Standard Model processes that can mimic the signatures of new physics. The LHC detectors, sophisticated marvels of engineering, are designed to capture the trajectory, energy, and momentum of virtually every particle produced in a collision. However, distinguishing the faint signal of a rare new particle amidst trillions of ordinary events requires finely tuned algorithms and rigorous statistical analysis. The researchers in this study have refined their selection criteria, focusing on specific kinematic distributions and particle multiplicities that are most sensitive to the presence of squarks with masses and decay properties suggested by viable SUSY models. The precision of their measurements is paramount, as even subtle deviations from Standard Model predictions could be the harbingers of new physics.
The concept of “naturalness” also plays a role in motivating this search. The hierarchy problem highlights the discrepancy between the electroweak scale (related to the masses of the W and Z bosons) and the Planck scale (associated with gravity). Without some form of new physics, such as supersymmetry, the masses of fundamental particles would require extreme fine-tuning to remain at their observed values, a scenario many physicists find unnatural. SUSY provides a mechanism for cancelling out large quantum corrections that would otherwise drive these masses to unnatural scales, thus “naturalizing” the electroweak scale. If squarks are indeed the LSP, their masses would be stringently constrained by the need to maintain this naturalness, guiding the experimental search to specific mass ranges.
The exclusion limits set by previous experiments at the LHC have already placed significant pressure on many SUSY models. However, the vast parameter space of these theories means that new regions are constantly being explored. This latest analysis specifically probes scenarios where the squarks of the first two families are relatively light compared to those of the third family (top and bottom quarks), a possibility that has not yet been definitively ruled out. The reason for focusing on the first two generations is multifaceted; it relates to the specific structure of certain SUSY models and the particular decay channels that would be most accessible given the LHC’s capabilities. The sensitivity to these lighter squarks is crucial, as they represent a more immediate manifestation of supersymmetry that could be within reach of current experimental energies.
The search for squarks is not a monolithic endeavor; it involves looking for various production mechanisms and decay pathways. Squarks can be produced directly in pairs through strong interactions, similar to how quarks are produced. Their subsequent decay can lead to a cascade of other particles, including other superpartners. The signature investigated in this study often involves the production of squarks that decay into quarks and gluinos (superpartners of gluons), or into quarks and neutralinos (a potential mixture of photino, Z boson, and Higgsino states). These decay chains then manifest as leptons, missing transverse energy (indicating the presence of invisible, weakly interacting particles like the LSP) and energetic jets. The precise configuration of these observed final-state particles provides crucial clues about the mass of the parent squark and the nature of the LSP.
Understanding the precise relationship between squarks and the broader SUSY landscape is critical. If squarks are the LSP, they would be the lightest superpartners. However, other SUSY models predict that the LSP could be a neutralino or a charguino, which would then decay into squarks and quarks. The focus on squarks as the LSP in this particular study reflects a specific class of models where the breaking of supersymmetry leads to these particular particles being the lightest. This theoretical motivation guides the experimentalists in optimizing their search strategies, targeting the specific decay products and event topologies that are most characteristic of these scenarios. The intricate interplay between theoretical predictions and experimental design is the driving force behind the progress in particle physics.
The implications of a positive detection would extend far beyond confirming supersymmetry. If a squark were identified as the LSP, it would provide a direct, tangible link to the enigmatic dark matter that permeates the cosmos. Understanding the properties of this squark-LSP would allow scientists to determine its mass, its interaction strength with ordinary matter, and its role in the evolution of the universe. This could lead to a paradigm shift in cosmology, offering a concrete explanation for the gravitational anomalies observed in galaxies and galaxy clusters, and potentially shedding light on the very origin and structure of the universe. The discovery would represent a monumental leap in humanity’s quest to comprehend the fundamental constituents of reality.
The ongoing analysis at the LHC is inherently a process of refinement and exploration. Even if this specific search does not yield a definitive discovery, the stringent limits placed on squark masses and properties are invaluable. These limits help to rule out large swathes of the SUSY parameter space, guiding theorists to refine their models and focus on more promising avenues of investigation. The scientific process is iterative, with each experiment building upon the knowledge gained from previous ones. The relentless pursuit of these elusive particles, even in the face of no definitive signal yet, pushes the boundaries of our understanding and hones the tools and techniques that will be essential for future discoveries.
The current generation of LHC experiments, with their unparalleled precision and sensitivity, represents the forefront of experimental particle physics. The continuous upgrades and improvements to the detectors and the accelerator itself ensure that the search for new physics remains a dynamic and evolving field. The insights garnered from analyzing these high-energy collisions are not just about finding new particles; they are about testing the fundamental symmetries and principles that govern the universe. Supersymmetry, if it exists, would be a profound reflection of a deeper, more elegant symmetry in nature, a principle that has historically guided our understanding of the physical world.
The prospect of discovering a squark as the lightest supersymmetric particle ignites a fervent excitement within the scientific community. It signifies not just the confirmation of a compelling theoretical framework but also a potential breakthrough in understanding one of the universe’s most profound mysteries: dark matter. The journey from theoretical conjecture to experimental verification is often long and arduous, but the potential rewards – a radically different and more complete picture of reality – drive the unwavering dedication of the physicists involved in these groundbreaking investigations at the LHC. The universe continues to hold its secrets close, but with each meticulously analyzed collision, we edge closer to unlocking its deepest truths, with the humble squark standing as a potential key to unlocking the dark universe. The data presented in this recent publication offers a tantalizing glimpse into the ongoing progress, refining the hunt and bringing us ever closer to potentially revolutionary answers.
Subject of Research: The search for the lightest supersymmetric particle (LSP) as a squark of the first two generations, utilizing data from proton-proton collisions at the Large Hadron Collider.
Article Title: Searching for a squark LSP of the first two families at the LHC.
Article References:
Knees, P., Kpatcha, E., Lara, I. et al. Searching for a squark LSP of the first two families at the LHC.
Eur. Phys. J. C 85, 852 (2025). https://doi.org/10.1140/epjc/s10052-025-14591-2
Image Credits: AI Generated
DOI: 10.1140/epjc/s10052-025-14591-2
Keywords: Supersymmetry, Squark, LSP, Dark Matter, LHC, Particle Physics, Beyond the Standard Model, High Energy Physics, Experimental Physics
