Russian scientists on the verge of solving the 'muon puzzle'

August 26, 2016, National Research Nuclear University
Credit: National Research Nuclear University

It may only take scientists a few more years to solve one of the biggest puzzles in modern elementary particle physics, the so-called "muon puzzle." Russian scientists from the National Research Nuclear University (MEPhI) will make a significant contribution to this research.

Cosmic ray particles in the Earth's atmosphere undergo a series of transformations and, as a result, produce elementary particles or . Muons reach the Earth's surface and can therefore be registered by ground-based detectors. Several years ago, scientists noticed that the number of registered muons is by tens of percentage points higher than it should be, according to existing theories. This phenomenon was called the muon puzzle.

The first clue to the muon puzzle was found in 2002-2007 during a long series of experiments on the DECOR facility in MEPhI. Later, the excess of muons was confirmed by experiments at the Pierre Auger Observatory in Argentina.

NEVOD Scientific and Educational Center, which is a subdivision of the Institute of Nuclear Physics and Engineering of MEPhI, is studying muons with the world's only multi-purpose neutrino water detector, which is used to research all cosmic ray components near the Earth's surface. MEPhI researchers spoke about the latest results of the experiments with NEVOD at the National Cosmic Ray Conference in Dubna, Moscow Region.

"In the past several years, we have increased the amount of experimental data three- or four-fold and, as a result, improved the precision of measurements. One of the tasks in the muon puzzle experimental research is to count not only the number of muons but to measure their energy characteristics. We started the experiment of measuring the energies of muons back in 2012, and it is still in progress. First, we used the coordinate-tracking detector DECOR to register a group of muons. Then we measured what energy they deposited in the NEVOD Cherenkov water detector," said Rostislav Kokoulin, NEVOD Senior Research Associate.

The scientists intend to find out whether the mean energy of muons has changed, in addition to their excess number.

"When the experiment proves the excess of energy exists, it will become clear what changes in the theoretical model are required. Now MEPhI is building new facilities that will operate alongside DECOR and NEVOD. This will allow the scientists to expand the set of characteristics under observation and make the measurements more precise."

Kokoulin added that the solution to the "muon puzzle" is a question of three to five years..

"Once the muon puzzle is solved, we will have a more accurate idea of the nuclear cascade process initiated by interactions of ultra-high energy particles. This understanding is required for studying characteristics of the universe and the processes within it," the scientist stressed.

Explore further: Cosmic mystery deepens with discovery of new ultra-high-energy neutrino

Related Stories

Rebooted muon experiment tests detector design at SLAC

August 7, 2014

Last year, a monster magnet set out from Brookhaven National Lab on an epic, 35-day trek by land and sea to its new home at Fermilab, where it will serve as the heart of a search for evidence of new subatomic particles. Last ...

50-foot-wide Muon g-2 electromagnet installed at Fermilab

July 31, 2014

One year ago, the 50-foot-wide Muon g-2 electromagnet arrived at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Illinois after traveling 3,200 miles over land and sea from Long Island, New York. ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

Physicists reveal why matter dominates universe

March 21, 2019

Physicists in the College of Arts and Sciences at Syracuse University have confirmed that matter and antimatter decay differently for elementary particles containing charmed quarks.

ATLAS experiment observes light scattering off light

March 20, 2019

Light-by-light scattering is a very rare phenomenon in which two photons interact, producing another pair of photons. This process was among the earliest predictions of quantum electrodynamics (QED), the quantum theory of ...

How heavy elements come about in the universe

March 19, 2019

Heavy elements are produced during stellar explosion or on the surfaces of neutron stars through the capture of hydrogen nuclei (protons). This occurs at extremely high temperatures, but at relatively low energies. An international ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.