We consider multimode two-photon interference at a beam splitter by photons created by spontaneous parametric down-conversion. The resulting interference pattern is shown to depend upon the transverse spatial symmetry of the pump beam. In an experiment, we employ the first-order Hermite-Gaussian modes in order to show that, by manipulating the pump beam, one can control the resulting two-photon...

The level of photon beam stability required to meet measurement resolution goals varies from experiment to experiment, depending on experiment-specific photon phase space acceptance aperture and the sensitivity of measurement to electron beam motion within its 6-D phase space. Stability time scales range from hours to microseconds, depending on experiment sampling rate, data integration period ...

In a previous article [Phys. Rev. Lett. 117, 213201 (2016)] we have determined the angular resolved and the total energy spectrum of a positron produced via nonlinear Breit-Wheeler pair production by a high-energy photon counterpropagating with respect to a tightly focused laser beam. Here, we first generalize the results in that article by including the possibility that the incoming photon is ...

All beams of electromagnetic radiation are made of photons. Therefore, it is important to find a precise relationship between the classical properties of the beam and the quantum characteristics of the photons that make a particular beam. It is shown that this relationship is best expressed in terms of the Riemann–Silberstein vector – a complex combination of the electric and magnetic field vec...

Backward polygon beam tracing methods, that is beam tracing from the light source (L), are well suited to gather path coherency from specular (S) scattering surfaces. These methods are useful for modelling and efficiently simulating caustics on diffuse (D) surfaces; an effect due to LS+D transport paths. This paper generalizes backward polygon beam tracing to include a glossy (G) scattering sur...

We present a preliminary analysis of the photon beam asymmetry observable (Σ) from the photoproduction reaction channel γn → π−p. This new data was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 2.3 GeV. The measurement will provide new data to address the poorly established ...

The four-dimensional Wigner distribution function is determined from intensity profiles measured in the focused photon beam of FLASH (Free-electron laser in Hamburg) for a variety of photon beamline settings. The Wigner formalism results in comprehensive coherence information without the requirement of simplifying assumptions on the beam. The entire four-dimensional spatial mutual coherence fun...

We discuss the experimental issues confronting measurements of the Virtual Compton Scattering (VCS) reaction ep → epγ with electron beam energies 6–30 GeV. We specifically address the kinematics of Deeply Virtual Compton Scattering (Deep Inelastic Scattering, with coincident detection of the exclusive real photon nearly parallel to the virtual photon direction) and large transverse momentum VCS...

background: delivering the maximum dose to tumor while achieving the minimum dose delivery to normal tissue; is the most important goal in external radiotherapy. diode in vivo dosimetry is widely considered to be an important tool for quality improvement of patient care in external radiotherapy. uncertainty in dose delivery should fall within 5% of the prescribed dose as recommended by internat...