120020642
The Low-Energy p–d System in Pionless EFT
We summarize results presented at the 5th Asian Pacific Conference on Few Body Problems in Physics, which was held in Seoul in August 2011. We calculate low-energy quartet and doublet channel proton–deuteron scattering in the framework of pionless effective field theory. We obtain good agreement with the available phase shift analyses. Moreover, we calculate the Coulomb contribution to the 3He–3H binding energy difference in first order perturbation theory.
118547616
The proton-deuteron system in pionless EFT revisited
We provide a detailed discussion of the low-energy proton?deuteron system in pionless effective field theory, considering both the spin-quartet and doublet S-wave channels. Extending and amending our previous work on the subject, we calculate the 3He?3H binding energy difference both perturbatively (using properly normalized trinucleon wave functions) and non-perturbatively by resumming all Coulomb diagrams in the doublet channel. Our nonperturbative result agrees well with a calculation that involves the full off-shell Coulomb T-matrix. Carefully examining the cutoff-dependence in the doublet channel, we present numerical evidence for a new three-nucleon counterterm being necessary at next-to-leading order if Coulomb effects are included. Indeed, such a term has recently been identified analytically. We furthermore make a case for a simplified Coulomb power counting that is consistent throughout the bound-state and scattering regimes. Finally, using a ?partially screened? full off-shell Coulomb T-matrix, we investigate the importance of higher-order Coulomb corrections in low-energy quartet-channel scattering.
119208271
Causality, universality, and effective field theory for van der Waals interactions
We analyze low-energy scattering for arbitrary short-range interactions plus an attractive 1/r^6 tail. We derive the constraints of causality and unitarity and find that the van der Waals length scale dominates over parameters characterizing the short-distance physics of the interaction. This separation of scales suggests a separate universality class for physics characterizing interactions with an attractive 1/r^6 tail. We argue that a similar universality class exists for any attractive potential 1/r^{alpha} for alpha >= 2. We also discuss the extension to multi-channel systems near a magnetic Feshbach resonance. We discuss the implications for effective field theory with attractive singular power law tails.
119296383
Causality constraints for charged particles
In quantum systems with short-range interactions, causality imposes nontrivial constraints on low-energy scattering parameters. We investigate these causality constraints for systems where a long-range Coulomb potential is present in addition to a short-range interaction. The main result is an upper bound for the Coulomb-modified effective range parameter. We discuss the implications of this bound to the effective field theory for nuclear halo systems. In particular, we consider several examples of proton–nucleus and nucleus–nucleus scattering. For the bound-state regime, we find relations for the asymptotic normalization coefficients (ANCs) of nuclear halo states. As an application of these relations, we extract the ANCs of the excited 2+ and 1− states in 16O from α − 12C scattering data.
119028863
${}^{3}\mathrm{He}$ and $pd$ Scattering to Next-to-Leading Order in Pionless Effective Field Theory
We study the three-body systems of ${}^{3}\mathrm{He}$ and $pd$ scattering and demonstrate, both analytically and numerically, that a new $pd$ three-body force is needed at next-to-leading order in pionless effective field theory. We also show that at leading order these observables require no new three-body force beyond what is necessary to describe $nd$ scattering. We include electromagnetic effects by iterating only diagrams that involve a single photon exchange in the three-body sector.
119249399
Precision calculation of the quartet-channel p-d scattering length
We present a fully perturbative calculation of the quartet-channel proton--deuteron scattering length up to next-to-next-to-leading order in pionless effective field theory. We use a framework that consistently extracts the Coulomb-modified effective range function for a screened Coulomb potential in momentum space and allows for a clear linear extrapolation back to the physical limit without screening. Our result of (10.9 +/- 0.4) fm agrees with older experimental determinations of this quantity but deviates from potential-model calculations and a more recent result from Black et al., which find larger values around 14 fm. As a possible resolution to this discrepancy, we discuss the scheme dependence of Coulomb subtractions in a three-body system.
121281729
Beam test measurements on GaAs pixel detectors at various angles of incidence
Abstract A GaAs pixel detector constructed in Aachen has been tested in a 4 GeV electron beam at DESY. The experimental setup allowed tilting the detector with respect to the beam line with angles of incidence from 0° to 45°. The sensor-array consisted of 8 × 16 pixels with a size of 125 × 125 μm 2 each. The detector was made of a 250μm thick Freiberger SI-GaAs wafer. An improved contact was formed on the backside, allowing safe operation of the detector in the soft breakdown regime. A double metal technique allowed bonding the single pixels linearly to the readout-chip. Using the the fast PreMux128 preamplifier multiplexer chip ( τ p = 40 ns ) a signal to noise ratio of 29 was obtained for a beam angle of incidence of 0° increasing up to 38 for 45°. The spatial resolution obtained with an angle of incidence of 45° was (9.0 ± 6.0) μm while the resolution of the untilted detector is equal to the digital one (36.1μm). For these testbeam-measurements the detector was connected to the electronics via wire-bonds. For future experiments bump-bonding connections are required. The results of a process for the formation of bump-bond connections on GaAs pixeldetectors are shown.