Quantum Radiation Reaction Effects in Multiphoton Compton Scattering

Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify the quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of the radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

Figure 1

A diagrammatic visualization of the calculation of incoherent multiphoton emission by a laser-driven electron. The double electron lines indicate that the electron states are Volkov states, and the dots represent the emission of more than two incoherent photons. At each photon emission step, the electron incoming quantum number $p_{-}$ is changed and determined by the previous step.

Figure 2

Multiphoton Compton spectra calculated quantum mechanically with (solid, black line) and without (long dashed, red line) the RR. For the sake of comparison, the corresponding classical spectra with (short dashed, blue line) and without (dotted, magenta line) the RR are also shown. The error bars in $d{\mathcal{S}}_Q^{\mathrm{RR}}/d\varpi$ stem from uncertainties in the multidimensional integrations in Eq. (2). The inset shows a zoom of the spectral region where different curves cross. The numerical parameters are ${\epsilon }_0=1\mathrm{GeV}$, ${\omega }_0=1.55\mathrm{eV}$, and $I_0=E_0^2/8\pi =5\times {10}^{22}\mathrm{W}/{\mathrm{cm}}^2$, corresponding to ${\xi }_0=154$, ${\chi }_0=1.8$, and $R_Q=1.1$, respectively.