Resonances in three-body systems with short and long-range interactions

The complex scaling method permits calculations of few-body resonances with the correct asymptotic behaviour using a simple box boundary condition at a sufficiently large distance. This is also valid for systems involving more than one charged particle. We first apply the method on two-body systems. Three-body systems are then investigated by use of the (complex scaled) hyperspheric adiabatic expansion method. The case of the 2$^+$ resonance in $^6$Be and $^6$Li is considered. Radial wave functions are obtained showing the correct asymptotic behaviour at intermediate values of the hyperradii, where wave functions can be computed fully numerically.Comment: invited talk at the 18th International Conference on Few-Body Problems in Physics, Santos-S.Paulo, August 21-26, 200

Measurement of the neutron electric dipole moment by crystal diffraction

An experiment using a prototype setup to search for the neutron electric dipole moment by measuring spin-rotation in a non-centrosymmetric crystal (quartz) was carried out to investigate statistical sensitivity and systematic effects of the method. It has been demonstrated that the concept of the method works. The preliminary result of the experiment is $d_{\rm n}=(2.5\pm 6.5)\cdot 10^{-24}$ e$\cdot$cm. The experiment showed that an accuracy of $\sim 2.5\cdot 10^{-26}$ e$\cdot$cm can be obtained in 100 days data taking, using available quartz crystals and neutron beams.Comment: 13 pages, 4 figure

Photon noise in a random laser amplifier with fluctuating properties

We study fluctuations of the number of photocounts measured by an ideal photodetector illuminated by light scattered in an amplifying disordered medium, below the threshold for random lasing. We show that the variance of fluctuations and their correlation function carry information about fluctuating properties of the medium. A direct link is established between the fluctuations of the number of photocounts due to the amplified spontaneous emission (ASE) and the dimensionless conductance g of the medium. Our results suggest a possibility of probing amplifying disordered media by analyzing statistics of their ASE, without illuminating them from outside by a probe beam.Comment: 14 pages, 9 figure

Three-body Thomas-Ehrman shifts of analog states of 17^{17}Ne and 17^{17}N

The lowest-lying states of the Borromean nucleus $^{17}$Ne ($^{15}$O+$p$ + $p$) and its mirror nucleus $^{17}$N ($^{15}$N+$n$ + $n$) are compared by using the hyperspheric adiabatic expansion. Three-body resonances are computed by use of the complex scaling method. The measured size of $^{15}$O and the low-lying resonances of $^{16}$F ($^{15}$O+$p$) are first used as constraints to determine both central and spin-dependent two-body interactions. The interaction obtained reproduces relatively accurately both experimental three-body spectra. The Thomas-Ehrman shifts, involving excitation energy differences, are computed and found to be less than 3% of the total Coulomb energy shift for all states.Comment: 9 pages, 3 postscript figures, revtex style. To be published in Phys. Rev.

Anatomy of three-body decay III. Energy distributions

We address the problem of calculating momentum distributions of particles emerging from the three-body decay of a many-body resonance. We show that these distributions are determined by the asymptotics of the coordinate-space complex-energy wave-function of the resonance. We use the hyperspherical adiabatic expansion method where all lengths are proportional to the hyperradius. The structures of the resonances are related to different decay mechanisms. For direct decay all inter-particle distances increase proportional to the hyperradius at intermediate and large distances. Sequential three-body decay proceeds via spatially confined quasi-stationary two-body configurations. Then two particles remain close while the third moves away. The wave function may contain mixtures which produce coherence effects at small distances, but the energy distributions can still be added incoherently. Two-neutron halos are discussed in details and illustrated by the $2^+$ resonance in $^{6}$He. The dynamic evolution of the decay process is discussed.Comment: 30 pages, 8 figures, to be published in Nuclear Physics

Classification of three-body quantum halos

The different kinds of behaviour of three-body systems in the weak binding limit are classified with specific attention to the transition from a true three-body system to an effective two-body system. For weakly bound Borromean systems approaching the limit of binding we show that the size-binding energy relation is an almost universal function of the three s-wave scattering lengths measured in units of a hyperradial scaling parameter defined as a mass weighted average of two-body equivalent square well radii. We explain why three-body halos follow this curve and why systems appearing above reveal two-body substructures. Three-body quantum halos 2-3 times larger than the limit set by zero hypermoment are possible