A brand new candidate for darkish matter

Dark matter stays one of many greatest mysteries in elementary physics. Many theoretical proposals (axions, WIMPs) and 40 years of in depth experimental searches have failed to supply any clarification of the character of darkish matter.

Several years in the past, in a concept unifying particle physics and gravity, new, radically totally different darkish matter candidates have been proposed: superheavy charged gravitinos.

Now, a paper revealed in Physical Review Research by scientists from the University of Warsaw and Max Planck Institute for Gravitational Physics reveals how new underground detectors, particularly the JUNO detector beginning quickly to take information, regardless that designed for neutrino physics, are additionally extraordinarily nicely suited to finally detect charged darkish matter gravitinos.

The simulations combining two fields, elementary particle physics and superior quantum chemistry, present that the gravitino sign within the detector must be distinctive and unambiguous.

In 1981, Murray Gell-Mann, Nobel Prize laureate for the introduction of quarks as elementary constituents of matter, observed the intriguing indisputable fact that the particles of the Standard Model, quarks and leptons, are contained in a concept formulated purely mathematically two years earlier, “N=8 supergravity,” distinguished by its maximal symmetry. N=8 supergravity comprises Standard Model matter particles of spin 1/2, but additionally comprises a gravitational half: graviton (of spin 2) and eight gravitinos of spin 3/2.

If the Standard Model is certainly associated to N=8 supergravity, the relation might level to a option to clear up probably the most tough downside of elementary theoretical physics—unifying gravity with particle physics. N=8 supergravity within the spin ½ sector comprises precisely 6 quarks (u,d,c,s,t,b) and 6 leptons (electron, muon, tauon and neutrinos) and forbids the presence of every other matter particles.

After 40 years of intensive accelerator analysis failing to find any new matter particles, the N=8 supergravity matter content material just isn’t solely in step with our information however stays the one recognized theoretical clarification of the variety of quarks and leptons within the Standard Model.

However, direct connection of N=8 supergravity with the Standard Model has a number of drawbacks, the principle one being that the electrical costs of quarks and leptons have been shifted by ±1/6 with respect to the recognized values; for instance, an electron had a cost -5/6 as a substitute of -1.

Several years in the past, Krzysztof Meissner from the Faculty of Physics on the University of Warsaw, Poland and Hermann Nicolai from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI), Potsdam, Germany, returned to Gell-Mann’s thought, and so they have been capable of transcend N=8 supergravity and modify the unique proposal acquiring appropriate electrical costs of the Standard Model matter particles.

The modification is much reaching, pointing to an infinite symmetry Ok(E10), which is little-known mathematically and replaces the standard symmetries of the Standard Model.

One of the stunning outcomes of the modification, described in papers in Physical Review Letters and Physical Review, is the truth that the gravitinos, presumably of an especially massive mass near the Planck scale, i.e., billion-billion proton plenty, are electrically charged: six of them have cost ±1/3 and two of them ±2/3.

The gravitinos, regardless that they’re extraordinarily huge, can’t decay since there are not any particles they may decay into. Meissner and Nicolai proposed subsequently that two gravitinos of cost ±2/3 (the opposite six have a lot decrease abundance) might be darkish matter particles of a really totally different form than something proposed thus far.

Namely, the extensively marketed traditional candidates, both extraordinarily gentle like axions or intermediate (proton) mass like WIMPs (weakly interacting huge particles), have been electrically impartial, in compatibility with the title “dark matter.” However, after greater than 40 years of intensive search by many various strategies and gadgets, no new particles past the Standard Model have been detected.

However, gravitinos current a brand new different. Even although they’re electrically charged, they are often darkish matter candidates as a result of, being so huge, they’re extraordinarily uncommon and subsequently observationally “do not shine in the sky” and keep away from the very tight constraints on the cost of darkish matter constituents.

Moreover, the electrical cost of gravitinos suggests a totally totally different method of making an attempt to show their existence.

The original paper revealed in 2024 within the European Physical Journal C by Meissner and Nicolai identified that neutrino detectors, based mostly on scintillators totally different from water, might be appropriate for the detection of darkish matter gravitinos.

However, the search is made enormously tough by their excessive rarity (presumably just one gravitino per 10,000 km³ within the photo voltaic system), which is why there isn’t any prospect of detection with presently accessible detectors. However, new big, oil or liquid argon underground detectors are both constructed or deliberate and real looking potentialities for looking for these particles at the moment are opening up.

Among all detectors, the Chinese Jiangmen Underground Neutrino Observatory (JUNO), now underneath building, appears predestined for such a search. It goals to find out the properties of neutrinos (really antineutrinos), however since neutrinos work together extraordinarily weakly with matter, the detectors should have very massive volumes.

In the case of the JUNO detector, this implies 20,000 tons of an natural, artificial oil-like liquid, generally used within the chemical trade, with particular additions, in a spherical vessel with a diameter of roughly 40 meters with greater than 17 thousand photomultipliers across the sphere. JUNO is scheduled to start measurements within the second half of 2025.

The paper in Physical Review Research by Meissner and Nicolai, with collaborators Adrianna Kruk and Michal Lesiuk from the Faculty of Chemistry on the University of Warsaw, presents an in depth evaluation of the precise signatures that occasions brought on by gravitinos might produce at JUNO and in future liquid argon detectors such because the Deep Underground Neutrino Experiment (DUNE) within the United States.

The paper describes not solely the theoretical background each on the physics and chemistry sides, but additionally a really detailed simulation of the potential signatures as a perform of the speed and monitor of a gravitino touring by means of the oil vessel. It required superior information of quantum chemistry and intensive CPU-time-consuming calculations.

The simulations needed to bear in mind many potential backgrounds—decay of radioactive ¹⁴C current within the oil, darkish rely fee and effectivity of photomultipliers, absorption of photons in oil, and so forth.

The simulations present that, with the suitable software program, the passage of a gravitino by means of the detector will depart a singular sign not possible to be wrongly recognized with a passage of any of the presently recognized particles.

The evaluation units new requirements when it comes to interdisciplinarity by combining two totally different areas of analysis: theoretical and experimental elementary particle physics on one hand and really superior strategies of contemporary quantum chemistry on the opposite.

The detection of the superheavy gravitinos could be a significant step ahead within the seek for a unified concept of gravity and particles. Since gravitinos are predicted to have plenty on the order of the Planck mass, their detection could be the primary direct indication of physics close to the Planck scale and will thus present beneficial experimental proof for a unification of all forces of nature.