Predicting the composition of dark matter

A new analysis by a team of physicists offers an innovative means to predict the “cosmological signatures” of dark matter models.

A team of physicists has developed a method to predict the composition of dark matter, invisible matter only detectable due to its gravitational pull on ordinary matter, which scientists have long sought to discover.

His work that appears in the magazine Physical Review Letters, is focused on predicting “cosmological signatures” for dark matter models with a mass between an electron and a proton. Previous methods have predicted similar signatures for simpler models of dark matter. This study establishes new ways of finding these signatures in more complex models that experiments continue to seek, the authors of the article note.

“Experiments looking for dark matter are not the only way to learn more about this mysterious type of matter,” says Cara Giovannetti, Ph.D. physics student at New York University and lead author of the paper.

“Precise measurements of various parameters of the universe — such as the amount of helium in the universe or the temperature of various particles in the early universe — can also tell us a lot about dark matter,” adds Giovanetti, describing the described method. in Physical Review Letters paper.

In a study with Hongwang Liu, an NYU postdoctoral fellow, Joshua Ruderman, an associate professor in the NYU Department of Physics, and Princeton physicist Mariangela Lisanti, Giovannetti and her co-authors focused on Big Bang Nucleosynthesis (BBN), a process that lighter forms of matter such as helium, hydrogen and lithium have been created. The presence of invisible dark matter affects how each of these elements will form. Also vital to these phenomena is the cosmic microwave background (CMB), the electromagnetic radiation generated by the union of electrons and protons that is left over from the formation of the universe.

The team was looking for a way to detect the presence of a particular category of dark matter — with a mass between an electron and a proton — by building models that account for both BBN and CMB.

“Such dark matter can change the abundance of certain elements produced in the early universe and leave an imprint on the cosmic microwave background, changing the expansion rate of the universe,” explains Giovanetti.

In their study, the team made predictions of cosmological signatures associated with the presence of certain forms of dark matter. These signatures are the result of dark matter changing the temperature of various particles or the expansion rate of the universe.

Their results showed that too light dark matter would result in different amounts of light elements than what astrophysical observations see.

“Light forms of dark matter could cause the universe to expand so rapidly that these elements would not have a chance to form,” says Giovannetti, outlining one scenario.

“From our analysis, we learned that some models of dark matter cannot have too little mass, otherwise the universe would look different than the one we observe,” she adds.