Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment

If a quantum mechanical particle is scattered by a potential well, the wave function of the particle can propagate with negative phase time. Due to the analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is expected to be observable for electromagnetic wave propagation. Experimental data of electromagnetic wells realized by wave guides filled with different dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure

Vlasov Description Of Dense Quark Matter

We discuss properties of quark matter at finite baryon densities and zero temperature in a Vlasov approach. We use a screened interquark Richardson's potential consistent with the indications of Lattice QCD calculations. We analyze the choices of the quark masses and the parameters entering the potential which reproduce the binding energy (B.E.) of infinite nuclear matter. There is a transition from nuclear to quark matter at densities 5 times above normal nuclear matter density. The transition could be revealed from the determination of the position of the shifted meson masses in dense baryonic matter. A scaling form of the meson masses in dense matter is given.Comment: 15 pages 4 figure

Manifestation of the Nuclear Anapole Moment in M1 Transitions in Thallium

We calculate nuclear spin-dependent parity non-conserving $E1$-amplitudes for optical transition $6p_{1/2,F} -> 6p_{3/2,F'}$ and for hyperfine transition $6p_{1/2,F} -> 6p_{1/2,F'}$ in Tl. Experimental limit on the former amplitude placed by Vetter et al. [PRL, 74, 2658 (1995)] corresponds to the anapole moment constant $\kappa_a = -0.26 \pm 0.27$. Experiment on the hyperfine transition can give direct measurement of the spin-dependent amplitude, because spin-independent amplitude turns to zero.Comment: 4 pages, LaTeX2e, uses revtex4.cl

Coherent amplification of classical pion fields during the cooling of droplets of quark plasma

In the framework of the linear sigma model, we study the time evolution of a system of classical $\sigma$ and pion fields coupled to quarks. For this purpose we solve numerically the classical transport equation for relativistic quarks coupled to the nonlinear Klein-Gordon equations for the meson fields. We examine evolution starting from variety of initial conditions corresponding to spherical droplets of hot quark matter, which might mimic the behaviour of a quark plasma produced in high-energy nucleus-nucleus collisions. For large droplets we find a strong amplification of the pion field that oscillates in time. This leads to a coherent production of pions with a particular isospin and so would have similar observable effects to a disoriented chiral condensate which various authors have suggested might be a signal of the chiral phase transition. The mechanism for amplification of the pion field found here does not rely on this phase transition and is better thought of as a "pion laser" which is driven by large oscillations of the $\sigma$ field.Comment: 12 TeX pages + 20 postscript figures, psfig styl

3D Gamma-ray and Neutron Mapping in Real-Time with the Localization and Mapping Platform from Unmanned Aerial Systems and Man-Portable Configurations

Nuclear Scene Data Fusion (SDF), implemented in the Localization and Mapping Platform (LAMP) fuses three-dimensional (3D), real-time volumetric reconstructions of radiation sources with contextual information (e.g. LIDAR, camera, etc.) derived from the environment around the detector system. This information, particularly when obtained in real time, may be transformative for applications, including directed search for lost or stolen sources, consequence management after the release of radioactive materials, or contamination avoidance in security-related or emergency response scenarios. 3D reconstructions enabled by SDF localize contamination or hotspots to specific areas or objects, providing higher resolution over larger areas than conventional 2D approaches, and enabling more efficient planning and response, particularly in complex 3D environments. In this work, we present the expansion of these gamma-ray mapping concepts to neutron source localization. Here we integrate LAMP with a custom $Cs_2LiLa(Br,Cl)_6:Ce$ (CLLBC) scintillator detector sensitive to both gamma-rays and neutrons, which we dub Neutron Gamma LAMP (NG-LAMP). NG-LAMP enables simultaneous neutron and gamma-ray mapping with high resolution gamma-ray spectroscopy. We demonstrate the ability to detect and localize surrogate Special Nuclear Materials (SNM) in real-time and in 3D based on neutron signatures alone, which is critical for the detection of heavily shielded SNM, when gamma-ray signatures are attenuated. In this work, we show for the first time the ability to localize, in 3D and realtime, a neutron source in the presence of a strong gamma-ray source, simultaneous and spectroscopic localization of three gamma-ray sources and a neutron source, and finally the localization of a surrogate SNM source based on neutron signatures alone, where gamma-ray data are consistent with background

Negative group delay for Dirac particles traveling through a potential well

The properties of group delay for Dirac particles traveling through a potential well are investigated. A necessary condition is put forward for the group delay to be negative. It is shown that this negative group delay is closely related to its anomalous dependence on the width of the potential well. In order to demonstrate the validity of stationary-phase approach, numerical simulations are made for Gaussian-shaped temporal wave packets. A restriction to the potential-well's width is obtained that is necessary for the wave packet to remain distortionless in the travelling. Numerical comparison shows that the relativistic group delay is larger than its corresponding non-relativistic one.Comment: 10 pages, 5 figure