N. Kitagawa

Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons

The Great Pyramid, or Khufu’s Pyramid, was built on the Giza plateau in Egypt during the fourth dynasty by the pharaoh Khufu (Cheops), who reigned from 2509 bc to 2483 bc. Despite being one of the oldest and largest monuments on Earth, there is no consensus about how it was built. To understand its internal structure better, we imaged the pyramid using muons, which are by-products of cosmic rays that are only partially absorbed by stone. The resulting cosmic-ray muon radiography allows us to visualize the known and any unknown voids in the pyramid in a non-invasive way. Here we report the discovery of a large void (with a cross-section similar to that of the Grand Gallery and a minimum length of 30u2009metres) situated above the Grand Gallery. This constitutes the first major inner structure found in the Great Pyramid since the nineteenth century. The void, named ScanPyramids’ Big Void, was first observed with nuclear emulsion films installed in the Queen’s chamber, then confirmed with scintillator hodoscopes set up in the same chamber and finally re-confirmed with gas detectors outside the pyramid. This large void has therefore been detected with high confidence by three different muon detection technologies and three independent analyses. These results constitute a breakthrough for the understanding of the internal structure of Khufu’s Pyramid. Although there is currently no information about the intended purpose of this void, these findings show how modern particle physics can shed new light on the world’s archaeological heritage.

A Test Experiment to Develop a Neutrino Detector with Emulsions for Neutrino-Nucleus Cross Section Measurements at J-PARC

We would like to perform a test experiment to develop a new neutrino detector with nuclear emulsions at the near detector hall of the J-PARC neutrino beam line. The physics aim is to detect neutrino interactions with high efficiency and measure the cross sections of neutrino (νμ/νμ, νe/νe)-nucleus charged/neutral current interactions in around 1 GeV energy region. First, we will perform a preliminary run to study environmental background inside the near detector hall. Then, we will perform a test run to study performance of the new detector and establish the analysis method to study neutrino interactions in the low energy region. Finally, we will perform data taking of physics runs to measure cross sections of neutrino-nucleus interactions with high efficiency.

Development of nuclear emulsion with thick type plastic base for improvement of angular accuracy

Muon radiography is nondestruction research technic for large structure like a pyramid, volcano, blast furnace. The technology measures the density length (=material density × path length) by calculating penetration rate of muon flux. The nuclear emulsion that is made in Nagoya university detects number of muon tracks and angles. We tried to change its “plastic layer” to thick type for improvement of angular accuracy and estimated “long term performance” and “angular accuracy”. In conclusion, the candidate has same long term quality and higher angular resolution.

Development of Analysis Method using GEANT4 for Cosmic Ray Radiography

Cosmic ray radiography is the inner investigation technology for large structures using by the muon. The Scan Pyramids Mission was launched in September of 2015 for observation of Egyptian Pyramid. We had installed nuclear emulsion detectors in the Bent Pyramid and the Khufus Pyramid. Cosmic ray radiography simulator was developed using by GEANT4 to estimate expected image by the survey. By the comparison between experiment data at the Descending Corridor in the Khufus Pyramid and simulation result, the unknown void had been discovered behind the entrance of the Khufus Pyramid.

Observation of Cosmic Rays with Nuclear Emulsions inside Egyptian Pyramids

A nuclear emulsion is a three dimensional tracking detector which is able to record minimum ionizing particles with micrometric accuracy. We are developing the nuclear emulsion for observation of cosmic rays and its analysis techniques. We have been applying nuclear emulsions to cosmic ray radiography for measuring the inner structure of nuclear power plants, volcanoes and so on. Since 2015, we have been observing cosmic rays inside the pyramids, which are the Bent Pyramid at Dahshur and Khufu’s Pyramid at Giza, in Egypt through ScanPyramids. In this project, we produced nuclear emulsions and installed them into the pyramids to measure cosmic ray muons. We observed over ten million muons passed through the pyramids and reconstructed the angular distribution of detected muons. Through the analysis, the validity of cosmic ray radiography for investigation of a pyramid was confirmed and the new space inside the Khufu’s Pyramid was discovered. In this paper, nuclear emulsions for the observation and latest results are described.