The ZEPLIN-III dark matter detector: performance study using an end-to-end simulation tool

We present results from a GEANT4-based Monte Carlo tool for end-to-end simulations of the ZEPLIN-III dark matter experiment. ZEPLIN-III is a two-phase detector which measures both the scintillation light and the ionisation charge generated in liquid xenon by interacting particles and radiation. The software models the instrument response to radioactive backgrounds and calibration sources, including the generation, ray-tracing and detection of the primary and secondary scintillations in liquid and gaseous xenon, and subsequent processing by data acquisition electronics. A flexible user interface allows easy modification of detector parameters at run time. Realistic datasets can be produced to help with data analysis, an example of which is the position reconstruction algorithm developed from simulated data. We present a range of simulation results confirming the original design sensitivity of a few times $10^{-8}$ pb to the WIMP-nucleon cross-section.Comment: Submitted to Astroparticle Physic

Study of number of black prongs in two generations of nuclear interactions in photoemulsion irradiated by 72 GeV 22Ne

This work is a study of new aspects in relativistic nucleus–nucleus interactions using the nuclear emulsion technique and it is aimed at development of a method of search of these interactions. Layers of nuclear photographic emulsion type-BR2 with sizes 100 x 200 mm2 x 600 µm were irradiated with 72 GeV 22Ne beam parallel to emulsion surface. The scanning length was 110 mm. The new idea is the counting of black prongs in nuclear–nuclear interactions due to primary projectile22Ne ions and due to theirα- andZ⩾3projectile fragments, i.e. their (Z⩾2)-secondary fragments. The ratio of their black prong multiplicity distributions is measured. Black prongs are low-energy Z=1 particles in case of protons with energies below 30 MeV emitted from the residual nuclei of these high-energy interactions. Two divisions of events were used. The first one was over more peripheral events, more central and exceedingly central collisions. The second division was over collisions creating fragments Z⩾2 and without their creation. The ratios between numbers of events in such different subsets, as well the ratios between of different mean values of Nb multiplicities averaged inside these subsets were studied. These results are discussed, also in the context of other thick target experiment, studied with radiochemistry or neutron counting techniques. In addition, different versions of the mean free nuclear ranges of Ne-ions and their heavy secondary fragments have been measured and calculated. We have scheduled the further strategy of search of new phenomena in similar multiplicity distributions at greater statistics of future experiments

Preliminary results on position reconstruction for ZEPLIN III

ZEPLIN III is a two-phase xenon detector for direct dark matter search that will look for rare nuclear recoils from elastic scattering of Weakly Interacting Massive Particles off xenon atoms. ZEPLIN III measures both the scintillation and ionisation signals produced in the liquid by the interacting particle. The prompt scintillation is detected by an array of 31 photomultipliers (PM) immersed in the liquid, and a strong electric field extracts the ionisation electrons to the vapour phase. Electroluminescence photons are produced in the gas and detected by the same PM array. In this paper we describe position reconstruction methods that use both these signals to achieve a position accuracy of a few millimetres in the horizontal plane and sub-millimetre in the vertical coordinate.http://www.sciencedirect.com/science/article/B6TJM-4MD310K-D/1/a5d0b57794dcd67b6d2dd09a098299d

Interactions of relativistic heavy ions in thick heavy element targets and some unresolved problems

Interactions of relativistic heavy ions with total energies above 30 GeV in thick Cu and Pb targets (≥ 2 cm) have been studied with various techniques. Radiochemical irradiation experiments using thick Cu targets, both in a compact form or as diluted “2π-Cu targets” have been carried out with several relativistic heavy ions, such as 44 GeV 12C (JINR, Dubna, Russia) and 72 GeV 40Ar (LBL, Berkeley, USA). Neutron measuring experiments using thick targets irradiated with various relativistic heavy ions up to 44 GeV 12C have been performed at the JINR. In addition, the number of “black prongs” in nuclear interactions (due to protons with energies less than 30 MeV and emitted from the target-like interaction partner at rest) produced with 72 GeV 22Ne ions in nuclear emulsion plates has been measured in the first nuclear interaction of the primary 22Ne ion and in the following second nuclear interaction of the secondary heavy (Z > 1) ion. Some essential results have been obtained. (1) Spallation products produced by relativistic secondary fragments in interactions ([44 GeV 12C or 72 GeV 40Ar] + Cu) within thick copper yield fewer products close to the target and many more products far away from the target as compared to primary beam interactions. This applies also to secondary particles emitted into large angles (Θ > 10°). (2) The neutron production of 44 GeV 12C within thick Cu and Pb targets is beyond the estimated yield as based on experiments with 12 GeV 12C. These rather independent experimental results cannot be understood within well-accepted nuclear reaction models. They appear to present unresolved problems