Blog 54 Dark Matter from Neutron Decay

There are many types of dark matter detectors, so far dark matter is a mystery, by award-winning author, adventurer and scientist Mark Kingston Levin PhD

Figure 1. Super-Kamiokande (SK) is the Japanese Dark Matter experiment started in 1996.

SK is located under a mountain known as Mt. Ikenoyama in the Gifu Prefecture near Nagoa Japan. A prefecture compares to states in the USA this Gifu Prefecture is very mountainous. There is a 50 kilo-ton Cherenkov detector 1000 meter under this massive mountain. The detector, which is located in the Kamioka Observatory, 1,000 meters beneath Mt. Ikenoyama. SK is dedicated to searching for nucleon decays and observing neutrinos from various sources, which is an indirect dark matter search. “The Japanese SK experiments looking for neutrinos and neutrino-induced muons from annihilations of WIMPs in the Earth, the sun, and the galaxy’s center and halo. SK has an excellent sensitivity to lower mass weakly interacting massive particles due to its lower neutrino energy threshold. There are many dozens of experiments looking for dark matter. To date nothing has worked.” Please see Dark Matter Hub, most of these are examining weak interacting massive particles (WIMPs) either directly or indirectly; however, recently some new approach have emerged. Much of this material below can be found in an article by Clara Moskowitz on January 29, 2018 Scientific American. A new neutron experiment near Grenoble France is very appropriate because the French have 80% nuclear electric power. The new PERKEO below shows the size compared to a woman for scale.

Figure 2. New improved large neutron decay spectrometer is called PERKEO III, which is located in Grenoble, Francs. It is designed to study neutron β-decay in-beam experiments, which offers many improved over its predecessor PERKEO II.

When used with a pulsed neutron beam, leading sources of systematic errors in other experiments are strongly suppressed or eliminated. The instrument was commissioned in a first run at the high flux reactor of the Institut Laue-Langevin, Grenoble. With a continuous polarized neutron beam, a neutron decay rate of 5x104s-1 was obtained. If Benjamin Grinstein can get some time on the French machine perhaps we all can learn something about dark matter.

Doctor Benjamin Grinstein chairman of the physics department University of California San Diego (UCSD) may be on the edge of dark matter discovery. According to Scientific American, beam experiments suggest the neutron’s average lifetime is about 888 seconds, roughly 9 seconds longer than what bottle experiments do. “When the lifetime of the neutron is measured by two different approaches, and the results differ, which could be a fundamental problem in our basic understanding of the laws of physics.” said study senior author Dr. Benjamín Grinstein.

After decades of fine-tuning both experimental approaches, physicists “have found no reason to suspect the discrepancy arises from bad measurements,” Grinstein said. “We are left with the very real option that we need to consider changing the laws of physics in a fundamental way.”

These scientists suggest that about 1 percent of the time that neutrons decay, along with breaking down into a few known particles, it is suggested that a small percentage produce dark matter particles, which may explain one of the greatest mysteries in science.

Figure 3. Scientific American article studies the possibility the missing neutrons could turn into DARK MATTER, but how could such small amounts of 4% of universe make 25% of the universe? Credit Scientific American and Credit: Ella Maru Studio Getty Images

The existence of dark matter particles was proposed to explain a variety of cosmic puzzles, such as why galaxies can spin as fast as they are seen to without flying off into space. Scientists have largely ruled out all known ordinary materials as candidates for dark matter. There is no consensus on the made up of Dark Matter: however, most experiments for the past few decades have been designed to find WIMPs. Since beam experiments are focused on neutrons decaying into protons, they could not account for the possible mode of decay that produces dark matter particles, and thus they give a different lifetime for the neutron than bottle experiments do.

“It would be truly amazing if the good old neutron turned out to be the particle enabling us to probe the dark matter sector of the universe,” said study coauthor Bartosz Fornal, a theoretical physicist at the University of California, San Diego. Fornal and Grinstein detailed their findings online May 9 in the journal Physical Review Letters.

The physicists explored several different scenarios of “dark decay” for neutrons, where the neutrons would break down into both dark matter particles and ordinary components such as gamma rays or electrons. “Our proposed new particles are dark in that, like dark matter, they interact feebly with normal matter,” Grinstein said.

Fornal and Grinstein’s work has so far inspired roughly a dozen studies examining its implications. For instance, nuclear physicist Christopher Morris at Los Alamos National Laboratory in New Mexico and his colleagues searched for gamma rays from a bottle of ultracold neutrons; but couldn’t detect anything within the window their instruments could observe.

Figure 4. Computer simulation of the universe showing matter in yellow and dark matter in black. Credit Wikipedia

Another set of tests of this idea has focused on neutron stars, which are superdense clusters of neutrons that form when giant stars go supernova.
At University of Illinois at Urbana-Champaign Jessie Shelton is a theoretical physicist of great reputation in her field. Jessie and her colleagues explained that neutron stars do not form black holes because their gravitational fields are not powerful enough to crush neutrons. Jessie explains that neutrons can decay into dark matter, it may cause neutron stars with sufficient mass to collapse due to their own gravity. This would mean that neutron stars with 70 percent of the sun’s mass could collapse into black holes, which is much lighter than previous estimates.

Shelton explained that if neutrons can indeed decay into dark matter, they may not give rise to just one kind of particle, but to at least two, and interactions between these new particles might prevent larger neutron stars from collapsing into black holes. “What we see from neutron stars suggests that neutrons decay either into no dark matter particles, or at least two,” Shelton said. “Maybe the dark sector of our universe is richer than we thought.”

“But future experiments may prove that the neutron lifetime anomaly has nothing to do with dark matter at all,” Fornal and Grinstein said. A highly precise experiment to analyze neutron properties, such as Perkeo III at the Institut Laue-Langevin in Grenoble, France, “seems to be capable of deciding the viability of exotic neutron dark decays,” said theoretical physicist William Marciano at Brookhaven National Laboratory in Upton, New York,(where I spend several years) an avenue he and his colleagues explored in a study appearing online May 16 in Physical Review Letters.

Atomic nuclei decay from Beryllium-11 this summer could yield information about dank matter. Doctor Marek Pfutzner of the University of Warsaw stated “an experiment scheduled for this summer called ISOLDE radioactive nuclei beam facility in Geneva will try to observe protons emitted.”

In 2007, the Perkeo III instrument was successful in a first run at the Institute Laue-Langevin in France near the Alps. The continuous neutron beam experiment obtained a detected neutron decay rate of 50 kHz, which is two orders of magnitude more than in previous experiments! The results of this measurement have been published in Nucl. Instr. Meth. A 611 (2009) 216-218.

Figure 5. Tracks of particles produced by a type of decay process known as beta radiation. Image credits: Wikimedia Commons

If we see enough of them, we will strongly reduce the room for dark decay. If we do not see them, the excitement will grow,” said Pfutzner.


Clara Moskowitz on January 29, 2018 Scientific American.

Other reference

Simulations of the formation, evolution and clustering of galaxies and quasars by

Volker Springel, Simon D. M. White, Adrian Jenkins, Carlos S. Frenk, Naoki Yoshida, Liang Gao, Julio Navarro, Robert Thacker, Darren Croton, John Helly, John A. Peacock, Shaun Cole, Peter Thomas, Hugh Couchman, August Evrard, Joerg Colberg & Frazer Pearce, 2005, Nature, 435, 629

Darren J. Croton, Volker Springel, Simon D. M. White, G. De Lucia, C. S. Frenk, L. Gao, A. Jenkins, G. Kauffmann, J. F. Navarro, N. Yoshida, 2005, MNRAS, (to be published)

Nucl. Instr. Meth. A 611 (2009) 216-218

The cosmological simulation code GADGET-2

Volker Springel, 2005, MNRAS, submitted

Supercomputer Simulations Explain the Formation of Galaxies and Quasars in the Universe

Max-Planck Society, 2005, link Press Release The largest N-body simulation of the universe

Volker Springel, 2004, link MPA research highlight article

Fornal and Grinstein detailed their findings online May 9 in the journal Physical Review Letters.

2019-01-09T14:45:58+00:00 January 9th, 2019|Blog, Uncategorized|