Luminescence quenching of the triplet excimer state by air traces in gaseous argon

While developing a liquid argon detector for dark matter searches we investigate the influence of air contamination on the VUV scintillation yield in gaseous argon at atmospheric pressure. We determine with a radioactive alpha-source the photon yield for various partial air pressures and different reflectors and wavelength shifters. We find for the fast scintillation component a time constant tau1= 11.3 +- 2.8 ns, independent of gas purity. However, the decay time of the slow component depends on gas purity and is a good indicator for the total VUV light yield. This dependence is attributed to impurities destroying the long-lived argon excimer states. The population ratio between the slowly and the fast decaying excimer states is determined for alpha-particles to be 5.5 +-0.6 in argon gas at 1100 mbar and room temperature. The measured mean life of the slow component is tau2 = 3.140 +- 0.067 microsec at a partial air pressure of 2 x 10-6 mbar.Comment: 7 pages submitted to NIM

Spectroscopy of Superfluid Pairing in Atomic Fermi Gases

We study the dynamic structure factor for density and spin within the crossover from BCS superfluidity of atomic fermions to the Bose-Einstein condensation of molecules. Both structure factors are experimentally accessible via Bragg spectroscopy, and allow for the identification of the pairing mechanism: the spin structure factor allows for the determination of the two particle gap, while the collective sound mode in the density structure reveals the superfluid state.Comment: 4 pages, 3 figure

Mesoscopic Rydberg Gate based on Electromagnetically Induced Transparency

We demonstrate theoretically a parallelized C-NOT gate which allows to entangle a mesoscopic ensemble of atoms with a single control atom in a single step, with high fidelity and on a microsecond timescale. Our scheme relies on the strong and long-ranged interaction between Rydberg atoms triggering Electromagnetically Induced Transparency (EIT). By this we can robustly implement a conditional transfer of all ensemble atoms among two logical states, depending on the state of the control atom. We outline a many body interferometer which allows a comparison of two many-body quantum states by performing a measurement of the control atom.Comment: published versio

Supersolid phase with cold polar molecules on a triangular lattice

We study a system of heteronuclear molecules on a triangular lattice and analyze the potential of this system for the experimental realization of a supersolid phase. The ground state phase diagram contains superfluid, solid and supersolid phases. At finite temperatures and strong interactions there is an additional emulsion region, in contrast to similar models with short-range interactions. We derive the maximal critical temperature $T_c$ and the corresponding entropy $S/N = 0.04(1)$ for supersolidity and find feasible experimental conditions for its realization.Comment: 4 pages, 4 figure

Preparation and spectroscopy of a metastable Mott insulator state with attractive interactions

We prepare and study a metastable attractive Mott insulator state formed with bosonic atoms in a three-dimensional optical lattice. Starting from a Mott insulator with Cs atoms at weak repulsive interactions, we use a magnetic Feshbach resonance to tune the interactions to large attractive values and produce a metastable state pinned by attractive interactions with a lifetime on the order of 10 seconds. We probe the (de-)excitation spectrum via lattice modulation spectroscopy, measuring the interaction dependence of two- and three-body bound state energies. As a result of increased on-site three-body loss we observe resonance broadening and suppression of tunneling processes that produce three-body occupation.Comment: 7 pages, 6 figure

Repulsively bound atom pairs: Overview, Simulations and Links

We review the basic physics of repulsively bound atom pairs in an optical lattice, which were recently observed in the laboratory, including the theory and the experimental implementation. We also briefly discuss related many-body numerical simulations, in which time-dependent Density Matrix Renormalisation Group (DMRG) methods are used to model the many-body physics of a collection of interacting pairs, and give a comparison of the single-particle quasimomentum distribution measured in the experiment and results from these simulations. We then give a short discussion of how these repulsively bound pairs relate to bound states in some other physical systems.Comment: 7 pages, 3 figures, Proceedings of ICAP-2006 (Innsbruck

Dispersion relations and soft pion theorems for K -> pi pi

We propose a new method to obtain the K -> pi pi amplitude from K -> pi which allows one to fully account for the effects of final state interactions. The method is based on a set of dispersion relations for the K -> pi pi amplitude in which the weak Hamiltonian carries momentum. The soft pion theorem, which relates this amplitude to the K -> pi amplitude, can be used to determine one of the two subtraction constants - the second constant is at present known only to leading order in chiral perturbation theory. We solve the dispersion relations numerically and express the result in terms of the unknown higher order corrections to this subtraction constant.Comment: Latex, 10 pages, 1 figure. Typo in eqs. (13,14) corrected, some rephrasing in the introductio

Radikale onkologische Chirurgie als Therapieprinzip beim Pankreaskarzinom

Zusammenfassung: Grundlagen: Mit den heutigen tiefen Morbiditäts-und Mortalitätsraten für Pankreasresektionen ist die Indikationsstellung für eine Standard- oder pyloruserhaltende Whipple-Operation weniger restriktiv zu stellen. Methodik: Pankreasresektionen für Karzinome sollten deshalb in kurativer oder palliativer Absicht, wenn immer möglich, durchgeführt werden. Verlangt werden dafür erfahrene Chirurgen mit über 10 Pankreaseingriffen pro Jahr und einer Mortalität von unter 10%. Als Standard gilt eine 2reihige Pankreatikojejunostomie mit Y-Roux-Rekonstruktion sowie die peri- und postoperative Therapie mit Octreotid während 7 Tagen. Ergebnisse: Innerhalb von 32 Monaten wurden 113 Patienten mit Pankreaskarzinom behandelt. Die Resektionsrate lag bei 50%, bei der Mehrzahl der Fälle wurde eine pyloruserhaltende Whipple-Operation durchgeführt (30/57). Die postoperative Morbidität lag bei 22,3%, kein Patient verstarb. Schlußfolgerungen: Die erweiterte (radikale) Duodenopankreatektomie wird ihren Wert im Vergleich zur Standard- oder pyloruserhaltenden Duodenopankreatektomie in prospektivrandomisierten Studien erst noch belegen müssen. Die Wirksamkeit einer adjuvanten Chemo- und/oder Radiotherapie bedarf weiterer Überprüfung mittels prospektiver Studie