Positron production in multiphoton light-by-light scattering
- Princeton Univ., NJ (United States). Joseph Henry Labs.
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.
- Research Organization:
- Princeton Univ., NJ (United States). Joseph Henry Labs.; Rochester Univ., NY (United States); Stanford Linear Accelerator Center, Menlo Park, CA (United States); Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- FG02-91ER40671; FG02-91ER40685; AC03-76SF00515
- OSTI ID:
- 491608
- Report Number(s):
- SLAC-PUB--7444; CONF-960836--3; Princeton/HEP--97-4; UTHEP--97-0301; ON: DE97006474; IN: UR-1498 ER/40685/902
- Country of Publication:
- United States
- Language:
- English
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