Science & Technology, South Africa (Commonwealth Union) – The quest for Dark Matter began with the realization that the visible matter observed in galaxies and galaxy clusters does not account for the gravitational forces at play. Something else, something invisible, exerts a gravitational pull, shaping the large-scale structure of the universe. This realization spurred a quest to unravel the nature of this hidden cosmic force.
Scientists are currently delving into the intriguing possibility that Dark Matter particles might originate within a jet of standard model particles.
The enigma of Dark Matter has persisted as one of the enduring mysteries in our universe. Despite constituting approximately, a quarter of the cosmos, Dark Matter exhibits minimal interaction with ordinary matter. Its existence has been substantiated through a series of astrophysical and cosmological observations, including the recent captivating images captured by the James Webb Space Telescope. Nevertheless, despite these confirmations, no experimental observations of Dark Matter have been reported to date. Consequently, the exploration of Dark Matter has become a longstanding quest undertaken by high-energy and astrophysicists globally.
Professor Deepak Kar, affiliated with the School of Physics at the University of the Witwatersrand in Johannesburg, South Africa, emphasizes the importance of fundamental scientific research in unveiling the deepest mysteries of the universe. He underscores the potential of the Large Hadron Collider at CERN, the colossal experiment designed to recreate conditions akin to the big bang, as a tool for detecting subtle indications of Dark Matter.
Conducting their research at the ATLAS experiment at CERN, Professor Kar and his former PhD student, Sukanya Sinha, currently a postdoctoral researcher at the University of Manchester, have introduced an innovative approach to the quest for Dark Matter. Their groundbreaking research has been documented in the journal Physics Letters B.
While previous collider searches for Dark Matter primarily focused on weakly interacting massive particles, or WIMPs, Professor Kar notes a shift in perspective. WIMPs, a class of particles hypothesized to elucidate Dark Matter, do not absorb or emit light and exhibit weak interactions with other particles. Given the absence of conclusive evidence for WIMPs, the researchers recognized the necessity for a paradigm shift in the ongoing pursuit of Dark Matter.
“What we were wondering, was whether Dark Matter particles actually are produced inside a jet of standard model particles,” said Kar. This brought about an investigation of a new detector signature referred to as semi-visible jets, which researchers have not explored on prior occasions.
In the realm of high-energy proton collisions, the outcome frequently involves the creation of a focused spray of particles, known as jets, originating from the decay of ordinary quarks or gluons. The concept of semi-visible jets enters the picture when hypothetical dark quarks undergo partial decay, giving rise to both Standard-Model quarks (recognized particles) and stable dark hadrons (constituting the “invisible fraction”). Produced in pairs, these semi-visible jets typically accompany additional Standard-Model jets, contributing to an energy imbalance or missing energy in the detector when the jets are not entirely balanced. Notably, the direction of the missing energy often aligns with one of the semi-visible jets.
The quest for semi-visible jets presents a formidable challenge, as this event signature can also result from inaccurately measured jets within the detector. The innovative approach introduced by Kar and Sinha in their exploration of Dark Matter introduces novel avenues for detecting the presence of Dark Matter, transcending traditional methodologies and shedding light on previously challenging aspects of this elusive phenomenon.
“Even though my PhD thesis does not contain a discovery of Dark Matter, it sets the first and rather stringent upper bounds on this production mode, and already inspiring further studies,” explained Sinha.
