2 research outputs found
Recommended from our members
Positron production in multiphoton light-by-light scattering
A signal of 106 {+-} 14 positrons above background has been observed in collisions of a low-emittance 46.6-GeV electron beam with terawatt pulses from a Nd:glass laser at 527 nm wavelength in an experiment at the Final Focus Test Beam at SLAC. Peak laser intensities of {approximately} 1.3 {times} 10{sup 18} W/cm{sup 2} have been achieved corresponding to a value of 0.3 for the parameter {Upsilon} = {var_epsilon}*/{var_epsilon}{sub crit} where {var_epsilon}* = 2{gamma}{var_epsilon}{sub lab} is the electric field strength of the laser transformed to the rest frame of the electron beam and {var_epsilon}{sub crit} = m{sup 2}c{sup 3}/e{bar h} = 1.3 {times} 10{sup 16} V/cm is the QED critical field strength. The positrons are interpreted as arising from a two-step process in which laser photons are backscattered to GeV energies by the electron beam followed by a collision between the high-energy photon and several laser photons to produce an electron-positron pair. These results are the first laboratory evidence for a light-by-light scattering process involving only real photons
Recommended from our members
Test of QED at critical field strength
In a new experiment at the Final Focus Test Beam at SLAC, a low-emittance 46.6 GeV electron beam is brought into collision with terawatt pulses of 1,054 nm or 527 nm wavelength from a Nd:glass laser. Peak laser intensities of 10{sup 18} W/cm{sup 2} have been achieved corresponding to a value of 0.6 for the parameter {eta} = e{var_epsilon}m{omega}{sub 0}c. In this case, an electron that crosses the center of the laser pulse has near-unit interaction probability. Results are presented for multiphoton Compton scattering in which an electron interacts with up to four laser photons, in agreement with theoretical calculations