Pioneering the Search for Dark Matter: A Revolutionary Approach at the Large Hadron Collider

Scientists at CERN’s ATLAS experiment, conducted at the Large Hadron Collider, have introduced an innovative method to explore the enigmatic realm of Dark Matter through semi-visible jets. This groundbreaking approach marks a significant shift in the field, offering fresh perspectives and stringent constraints in the ongoing quest to comprehend the nature of dark matter.

The enduring mystery of dark matter has intrigued the scientific community for decades. Constituting roughly a quarter of the universe’s mass-energy content, dark matter eludes interaction with ordinary matter, making its detection an intricate challenge. While its existence has been affirmed through a series of astrophysical and cosmological observations, experimental verification has remained elusive, captivating high-energy physicists and astrophysicists worldwide.

Advancements in the Realm of Dark Matter Research

Professor Deepak Kar, hailing from the School of Physics at the University of the Witwatersrand in Johannesburg, South Africa, underscores the significance of basic science research in unraveling the universe’s deepest mysteries. The Large Hadron Collider, renowned as the most substantial experimental apparatus ever constructed, provides a unique opportunity to seek clues about dark matter within particle collisions that mimic conditions akin to the Big Bang.

Within the ATLAS experiment at CERN, Professor Kar and his former PhD student, Dr. Sukanya Sinha, now a postdoctoral researcher at the University of Manchester, have spearheaded a novel approach to investigate dark matter. Their findings have been detailed in the journal “Physics Letters B.”

A Paradigm Shift in the Search for Dark Matter

Traditionally, collider searches for dark matter have centered around weakly interacting massive particles, known as WIMPs. These hypothesized particles were thought to explain dark matter due to their minimal interaction with other particles and the absence of light absorption or emission. However, the absence of conclusive evidence for WIMPs prompted scientists to rethink their approach.

Professor Kar explains the rationale behind their new direction: “We contemplated whether dark matter particles might actually be produced within a jet of standard model particles.” This inquiry led to the exploration of a unique detector signature termed “semi-visible jets,” which had not been previously examined.

High-energy proton collisions often yield collimated sprays of particles, referred to as jets, resulting from the decay of ordinary quarks or gluons. Semi-visible jets manifest when hypothetical dark quarks partially decay into Standard-Model quarks (known particles) and partially into stable dark hadrons (the “invisible fraction”). These pairs of semi-visible jets, typically accompanied by additional Standard-Model jets, generate an energy imbalance or missing energy in the detector when not fully balanced. Remarkably, the direction of this missing energy often aligns with one of the semi-visible jets.

This characteristic makes the search for semi-visible jets exceptionally challenging, as it can also arise from inaccuracies in jet measurements within the detector. Nonetheless, Kar and Sinha’s innovative approach opens up new avenues for detecting the presence of dark matter.

Dr. Sinha emphasizes the impact of their research: “While my PhD thesis may not have unveiled the secrets of dark matter, it has set stringent upper limits on this production mode, serving as a catalyst for further investigations.”

The ATLAS Collaboration at CERN has recognized this as a flagship result emerging from their summer conferences.

Reference: “Search for non-resonant production of semi-visible jets using Run 2 data in ATLAS” by The ATLAS Collaboration, 11 November 2023, Physics Letters B.
DOI: 10.1016/j.physletb.2023.138324

The Large Hadron Collider in Europe, including the ATLAS calorimeter, is contributing to more precise measurements of fundamental particles, advancing our understanding of the universe’s building blocks.

The ATLAS Experiment

The ATLAS experiment stands as a monumental scientific undertaking within CERN, the European Organization for Nuclear Research. As an integral component of the Large Hadron Collider (LHC), the world’s largest and most potent particle accelerator, ATLAS, abbreviated for “A Toroidal LHC ApparatuS,” is dedicated to probing the fundamental aspects of physics.

ATLAS is designed to explore a diverse array of scientific inquiries, encompassing the fundamental forces that have shaped the universe’s evolution and its ultimate destiny. Among its primary objectives is the investigation of the Higgs boson, a particle intimately linked with the Higgs field, responsible for endowing other particles with mass. The discovery of the Higgs boson in 2012, achieved through a collaborative effort by ATLAS and the CMS (Compact Muon Solenoid) experiment, marked a seminal moment in physics.

Additionally, the experiment seeks to unearth indications of new physics, shedding light on the origins of mass, the existence of extra dimensions, and the potential constituents of dark matter. ATLAS accomplishes this by scrutinizing the multitude of particles generated during high-speed proton collisions within the LHC.

The ATLAS detector itself stands as a marvel of technology, boasting immense dimensions, with a length of approximately 45 meters, a diameter of 25 meters, and a weight of around 7,000 tonnes. Comprising distinct layers tailored to detect various particle types resulting from proton-proton collisions, the detector incorporates an array of cutting-edge technologies. These encompass trackers for tracing particle paths, calorimeters for measuring energy, and muon spectrometers for identifying and quantifying muons, a heavyweight electron variant pivotal to numerous physics investigations.

The data amassed by ATLAS is staggering, often quantified in petabytes. This voluminous data undergoes analysis by a global community of scientists, fostering a deeper understanding of fundamental physics and the potential revelation of new insights and technologies.

Frequently Asked Questions (FAQs) about Dark Matter Discovery

More about Dark Matter Discovery

• CERN’s ATLAS Experiment
• Physics Letters B Journal
• The Large Hadron Collider at CERN
• Higgs Boson Discovery at CERN
• Dark Matter Overview
• School of Physics, University of the Witwatersrand
• University of Manchester
• The ATLAS Collaboration