2023-11-28 09:45:09
The existence of dark matter is a mystery that has baffled physicists for years. Judging by the gravity it exerts, there is much more dark matter in the universe than normal, and yet no one has been able to detect dark matter directly. This exotic class of matter does not emit radiation of any kind nor interact significantly with ordinary matter. The existence of dark matter has been confirmed by a series of astrophysical and cosmological observations. However, to date no experimental observations of dark matter have been recorded. The existence of dark matter is the subject of research and debate for astrophysicists and high energy specialists around the world.
But what if dark matter particles are generated among the “normal” ones that are created in some collisions within accelerators during the course of experiments?
The LHC (Large Hadron Collider) at the European Laboratory for Particle Physics (CERN) is the largest particle accelerator in the world and the collisions of particles in it create conditions similar to some of those that reigned during the Big Bang, the “explosion “with which the universe was born. Such collisions at the LHC can be used to search for signs of dark matter, argues Deepak Kar of the University of the Witwatersrand in Johannesburg, South Africa.
Working on the ATLAS detector at the LHC at CERN, the team of Kar and Sukanya Sinha (now at the University of Manchester in the United Kingdom), devised a new way to search for dark matter by taking advantage of that detector.
In recent decades, numerous searches for dark matter have been carried out in particle accelerators, until now focused on hypothetical weakly interacting massive particles called WIMPs. WIMPs are a class of particles that, according to some hypotheses, could explain dark matter, since they do not absorb or emit light and do not interact strongly with other particles. However, since no evidence of the existence of these particles has been found so far, it seems that the search for dark matter needs a change of approach.
This frames the question of whether dark matter particles are generated within a jet of “normal” particles created by the energy of a collision caused in a particle accelerator such as the LHC. This led to the exploration of the possibility of using a new “signature” (or “fingerprint”) that could be collected by ATLAS and that, in theory, would demonstrate the passage of dark matter. Traces of this type are called “semi-visible jets.”
Graphic representation of how semi-visible jets will appear on the ATLAS detector, if they exist. (Image: CERN)
High-energy collisions of protons often result in the production of a collection of particles, collected in jets, from the decay of ordinary quarks or gluons. The semi-visible jets would arise when hypothetical dark quarks decay, partially giving rise to Standard Model quarks (known particles) and partially to stable dark hadrons (the “invisible fraction”). Since they occur in pairs, usually along with other Standard Model jets, energy imbalance or missing energy in the detector arises when all jets are not fully balanced. The direction of the missing energy is usually aligned with one of the semi-visible jets.
With enough improvements to avoid false positives, the strategy could work. The international team of Kar and Sinha has been working on this.
Kar, Sinha and their colleagues present the technical details of their latest findings in the academic journal Physics Letters B, under the title “Search for non-resonant production of semi-visible jets using Run 2 data in ATLAS.” (Source: NCYT from Amazings)
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