Nuclear effects and their interplay in nuclear DVCS amplitudes

In this paper we analyze nuclear medium effects on DVCS amplitudes in the \Bx range of $0.1-0.0001$ for a large range of $Q^2$ and four different nuclei. We use our nucleon GPD model capable of describing all currently available DVCS data on the proton and extend it to the nuclear case using two competing parameterizations of nuclear effects. The two parameterizations, though giving different absolute numbers, yield the same type and magnitude of effects for the imaginary and real part of the nuclear DVCS amplitude. The imaginary part shows stronger nuclear shadowing effects compared to the inclusive case i.e. $F^N_2$, whereas in the real part nuclear shadowing at small \Bx and anti-shadowing at large \Bx combine through evolution to yield an even greater suppression than in the imaginary part up to large values of \Bx. This is the first time that such a combination of nuclear effects has been observed in a hadronic amplitude. The experimental implications will be discussed in a subsequent publication.Comment: 8 pages, 5 figures, uses RevTex4, final version to appear in PHys. Rev.

DVCS on nuclei: Observability and Consequences

In this paper, we discuss the feasibility of measuring deeply virtual Compton scattering (DVCS) on nuclei in a collider setting, as for example, the planned high-luminosity Electron-Ion-Collider (EIC). We demonstrate that employing our recent model for nuclear generalized parton distributions (nGPDs), the one-photon unpolarized DVCS cross section as well as the azimuthal- and spin asymmetry are of the same size as in the proton case. This will allow for an experimental extraction of nuclear GPDs with high precision shedding new light on nuclear shadowing at small $x_{bj}$ and the interplay of shadowing and nuclear enhancement at $x_{bj}~0.1$.Comment: 9 pages, 18 figures, uses EPJ style format, final version to appear in EPJ

Single spin asymmetry in DVCS

In the following note, we will present an estimation of the single spin asymmetry in deeply virtual Compton scattering (DVCS) which directly allows one to test predictions of the ratio of the imaginary part of the amplitude in DIS to DVCS, as well as access the skewed parton distributions at small $x$ in the DGLAP region. We find it to be large for the HERA kinematics to be accessible in forthcoming runs with polarized electrons.Comment: 6 pages, 2 figures in eps format. Submitted to Phys. Rev. D's Rapid Communication

Systematic Exploration of the Neutrino Factory Parameter Space including Errors and Correlations

We discuss in a systematic way the extraction of neutrino masses, mixing angles and leptonic CP violation at neutrino factories. Compared to previous studies we put a special emphasis on improved statistical methods and on the multidimensional nature of the combined fits of the nu_e -> nu_mu, \bar nu_e -> \bar nu_mu appearance and nu_mu -> nu_mu, \bar nu_mu -> \bar nu_mu disappearance channels. Uncertainties of all involved parameters and statistical errors are included. We find previously ignored correlations in the multidimensional parameter space, leading to modifications in the physics reach, which amount in some cases to one order of magnitude. Including proper statistical errors we determine for all parameters the improved sensitivity limits for various baselines, beam energies, neutrino fluxes and detector masses. Our results allow a comparison of the physics potential for different choices of baseline and beam energy with regard to all involved parameters. In addition we discuss in more detail the problem of parameter degeneracies in measurements of delta_CP.Comment: 29 pages, 14 fugure

Studies of a Terawatt X-Ray Free-Electron Laser

The possibility of constructing terawatt (TW) x-ray free-electron lasers (FELs) has been discussed using novel superconducting helical undulators [5]. In this paper, we consider the conditions necessary for achieving powers in excess of 1 TW in a 1.5 {\AA} FEL using simulations with the MINERVA simulation code [7]. Steady-state simulations have been conducted using a variety of undulator and focusing configurations. In particular, strong focusing using FODO lattices is compared with the natural, weak focusing inherent in helical undulators. It is found that the most important requirement to reach TW powers is extreme transverse compression of the electron beam in a strong FODO lattice. The importance of extreme focusing of the electron beam in the production of TW power levels means that the undulator is not the prime driver for a TW FEL, and simulations are also described using planar undulators that reach near-TW power levels. In addition, TW power levels can be reached using pure self-amplified spontaneous emission (SASE) or with novel self-seeding configurations when such extreme focusing of the electron beam is applied.Comment: 10 pages, 12 figure