Space

China’s DAMPE detects peak in cosmic ray electrons, might crack dark matter mystery

Current space telescope may help solve the secrets of dark matter

A Chinese space telescope has discovered an unfamiliar peak in high-energy cosmic ray electrons and positrons, which are highly active particles blazing across the universe at close to the speed of light. Scientists say they think such an anomaly can help crack the secrets of dark matter, the strangest ingredient in the universe. The Dark Matter Particle Explorer mission announced its first experimental outcomes on Nov. 30 in Nature, presenting the specific measurement of cosmic ray electron flux, mainly a spectral break at ~0.9 TeV. The data may emit light on the annihilation or decay of dark particle matter.

DAMPE is a cooperation of more than a hundred investigators, specialists, and students at nine institutes in China, Switzerland, and Italy, under the guidance of the Purple Mountain Observatory of the Chinese Academy of Sciences. The DAMPE mission is financed by the strategic preference science and technology projects in space science of CAS.

A Word on DAMPE

China’s first dark matter satellite named DAMPE (Dark Matter Particle Explorer) that was launched on 17 December from Jiuquan Satellite Launch Center, Gansu province has started sending data to the ground stations. Chinese space agency confirmed that it has received first data sent by dark matter probe.

The DAMPE satellite is also nicknamed as “Wukong” and the peculiar name has been taken from the Chinese classical fiction “Journey to the West”  after the Monkey King with penetrating eyes.

The 1.9- tonne desk-sized satellite will be placed in the sun-synchronous orbit at a height of 500 km where it will scan for dark matter for first two years. According to officials, more than 100 scientists will analyse the data sent back by the DAMPE satellite and first findings will be published in the second half of next year. In addition, the satellite will be in space for at least five years and will be used for several other missions.

“The main scientific objective of DAMPE is to measure electrons and photons with much higher energy resolution and energy reach than achievable with existing space experiments in order to identify possible dark matter signatures,” scientists wrote in a description of the mission on the University of Geneva’s website. “It has also great potential in advancing the understanding of the origin and propagation mechanism of high energy cosmic rays, as well as in new discoveries in high energy gamma astronomy.”

 

In its first 530 days of science plan through June 8 of this year, DAMPE has identified 1.5 million cosmic ray electrons and positrons above 25 GeV. The electron and positron data are characterized by unprecedentedly high energy resolution and low particle background infection.

The first declared results in the energy range from 25 GeV to 4.6 TeV. The spectral data in the energy range of 55 GeV-2.63 TeV strongly prefer an evenly broken power-law model to a single power-law model. DAMPE has straight identified a spectral break at ~0.9 TeV, with the phantom index turning from ~3.1 to ~3.9. The specific frequency of the cosmic ray electron and positron spectrum, in relevant the flux declination at TeV energies, significantly narrows the parameter space of models such as nearby pulsars, supernova remnants, and candidates for dark particle matter that was intended to account for the positron anomaly unveiled earlier by PAMELA and AMS-02, according to FAN Yizhong, deputy chief designer of DAMPE’s experimental application system.

FAN said that concurrently with data from the cosmic microwave background investigations, high energy gamma-ray measurements, and other celestial telescopes, the DAMPE data may help to eventually clarify the relationship between the positron anomaly and the annihilation or decay of dark particle matter. Data also hint at the appearance of spectral structure between 1 and 2 TeV energies, a probable result of nearby cosmic ray sources or exotic physical processes. More data are required to examine this phenomenon.

DAMPE has filmed over 3.5 billion cosmic ray events, with highest event energies exceeding ~100 trillion electronvolts. DAMPE is suspected to record more than 10 billion astronomical ray events over its useful life propelled to exceed five years given the contemporary state of its devices. More statistics will allow more precise analysis of the cosmic ray electron and positron spectrum up to ~10 TeV. Investigators will also be able to examine spectral characteristics potentially generated by dark matter particle annihilation nearby astrophysical sources.

The results compare of the cosmic ray electron and positron spectra from DAMPE and other investigations. The DAMPE outcomes detailed here demonstrate the unique capability of DAMPE to explore possible new physics and new astrophysics in the TeV energy window, thanks to its high energy resolution, broad instrumental acceptance, extensive energy coverage, excellent electron/proton disconnection power, and long working life.

DAMPE’s first experimental result is a milestone for the global cooperation. The purpose will continue to study galactic cosmic rays up to ~10 TeV for electrons/gamma-rays and hundreds of TeV for nuclei, sequentially. DAMPE data is supposed to unveil new phenomena of the universe in the TeV window.

PMO, under the leadership of Principal Investigator CHANG Jin, proposed and led the initial design of DAMPE. The Plastic Scintillator Detector was constructed by the Institute of Modern Physics, CAS. The Silicon-Tungsten tracKer-converter indicator was mutually developed by the Institute of High Energy Physics, CAS, the University of Geneva, and INFN Perugia. The BGO imaging calorimeter was jointly produced by the University of Science and Technology of China and PMO. PMO constructed the Neutron Detector. The Data Acquisition System was formed by National Space Science Center, CAS. The data investigation work of the DAMPE international Collaboration is the conclusion of the scientists in all the participating institutes. The experimental activities are organized by the ground Scientific Application System led by PMO, USTC, and UniGE, in a competitive but still collaborative training achieved to the release of highest level scientific results.

What is Dark Matter?

Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but accounts for most of the matter in the universe (nearly 85 percent). The existence and properties of dark matter are inferred from its gravitational effects on visible matter, on radiation, and on the large-scale structure of the universe.

Although scientists haven’t seen dark matter yet, several experiments have suggested that dark matter is omnipresent and accounts for more than 85 percent of our Universe’s mass. The new venture by China will unravel the mystery of Dark Matter.

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