A brand new seek for dark matter has turned up empty handed — but, in a silver lining, the trouble provided essential limits that may help future experiments narrow down the hunt for this elusive substance.
Most astronomers consider that dark matter accounts for 85 percent of all mass in the universe, and that its existence would explain the apparent extra gravity detectable around galaxies and inside huge galaxy clusters. Nevertheless, to this point, nobody has been capable of discover what dark matter is manufactured from.
Until recently, the front-runner suspect had been a breed of particle called a WIMP, which is a neat acronym for Weakly Interacting Massive Particles. These theoretical particles are thought to barely interact with normal matter, except in relation to gravity. Nevertheless, the Large Hadron Collider (LHC), the world’s largest and strongest particle accelerator, has did not turn up evidence for the existence of WIMPs.
Thus, theorists are having to scramble to seek out alternative theories of what dark matter may very well be.
Related: We still do not know what dark matter is, but here’s what it isn’t
“WIMPs is one class of particles which might be hypothesized to elucidate dark matter as they don’t absorb or emit light and don’t interact strongly with other particles,” Deepak Kar, a professor of physics of the University of the Witwatersrand in Johannesburg, said in a statement. “Nevertheless, as no evidence of WIMPs has been found to this point, we realized that the seek for dark matter needed a paradigm shift.”
Some alternative models of dark matter posit that, quite than being weakly interacting, dark matter could actually interact strongly with some particles within the Standard Model, which is a framework of particle physics that describes every known particle in addition to how each particle interacts with, and pertains to, each other. Dark matter particles are believed to exist beyond the Standard Model’s scope; the models that predict strongly interacting dark matter, quite,describe a whole menagerie of theoretical particles starting with basic “dark quarks” and “dark gluons.” Those are like dark mirrors of quarks and gluons which might be the basic constructing blocks of all visible matter and surely present within the Standard Model.
Now, Kar and his former student, Sukanya Sinha who’s now on the University of Manchester within the U.K., have developed a brand new way of looking for these potential dark quarks and dark gluons in high-energy collisions between protons that happen throughout the LHC.
When protons come together at almost the speed of sunshine contained in the LHC, they’re smashed apart into their component quarks and gluons that swiftly decay to provide a shower of short-lived subatomic particles. These particle showers are known as “jets.”
Kar and Sinha’s idea, which formed the idea of Sinha’s Ph.D., is that possible dark quarks and dark gluons could decay to provide a mix of particles, some odd and a few dark as well. This may end in what they check with as “semi-visible” jets. Jets are produced in pairs, they explain, and if one normal jet and one semi-visible jet were produced side-by-side, the dark particles would carry away a few of the energy, resulting in a telltale energy imbalance reading since the dark particles wouldn’t be seen.
Kar and Sinha have led a seek for these energy imbalances with the LHC’s ATLAS experiment. Because a slight mis-measurement of two normal jets could mimic the energy imbalance of a semi-visible jet, nevertheless, the info from ATLAS needed to be analyzed very fastidiously.
The duo found no evidence for semi-visible jets — but that doesn’t mean they don’t exist.
The ATLAS results, published within the journal Physics Letters B, point to upper limits for the properties of those theoretical dark particles, allowing future experiments looking for them to be fine-tuned.