Synopsis: Air showers from ultrahigh-energy cosmic rays

Cascades created by cosmic rays interacting with the atmosphere provide clues about the mass composition of ultrahigh-energy cosmic rays.
Synopsis figure
Illustration: Courtesy of the Pierre Auger Observatory

The nature and origin of ultrahigh-energy (>1018eV) cosmic rays remain a mystery. Astrophysicists hunt for clues regarding their mass composition, which, along with other properties such as the flux and arrival direction distribution, should help distinguish among the various models of the sources and propagation of cosmic rays. However, because of the low flux of ultrahigh-energy cosmic rays, the mass composition cannot be measured directly. Instead, it is inferred from measurements of the extensive air showers—the cascades of high-energy ions created when incident cosmic rays collide with atoms in the atmosphere. The atmospheric depth at which development of a shower reaches its maximum number of secondary particles depends on the mass and energy of the incident particle. Data on the depth of the maximum thus provide information about the mass composition.

The Pierre Auger Collaboration has presented in Physical Review Letters new measurements of extensive air showers from ultrahigh-energy cosmic rays. Their observations suggest a gradual increase in the average mass of cosmic rays in a region of energies around 1019eV. The data are the highest statistics measurements to date. – Stanley Brown


Features

More Features »

Announcements

More Announcements »

Subject Areas

Particles and FieldsAstrophysics

Previous Synopsis

Atomic and Molecular Physics

Better timing with aluminum ions

Read More »

Next Synopsis

Superconductivity

Keep it local

Read More »

Related Articles

Synopsis: Intel on Stellar Element Production from Accelerator Data
Nuclear Physics

Synopsis: Intel on Stellar Element Production from Accelerator Data

Measurements of a nuclear reaction relevant to the synthesis of calcium, potassium, and argon in stars boost the accuracy of models for predicting the elements’ abundances. Read More »

Synopsis: Putting Neutrino Oscillations on Ice
Particles and Fields

Synopsis: Putting Neutrino Oscillations on Ice

The IceCube mission in the ice of Antarctica has measured neutrino oscillations at energies higher than any previous observation. Read More »

Synopsis: LHC Sees No Dark Photons
Particles and Fields

Synopsis: LHC Sees No Dark Photons

A search for dark photons at the LHC comes up empty but puts new constraints on the strength of the hypothetical particles’ coupling to electromagnetic fields. Read More »

More Articles