Single electron emission in two-phase xenon with application to the detection of coherent neutrino-nucleus scattering

We present an experimental study of single electron emission in ZEPLIN-III, a two-phase xenon experiment built to search for dark matter WIMPs, and discuss applications enabled by the excellent signal-to-noise ratio achieved in detecting this signature. Firstly, we demonstrate a practical method for precise measurement of the free electron lifetime in liquid xenon during normal operation of these detectors. Then, using a realistic detector response model and backgrounds, we assess the feasibility of deploying such an instrument for measuring coherent neutrino-nucleus elastic scattering using the ionisation channel in the few-electron regime. We conclude that it should be possible to measure this elusive neutrino signature above an ionisation threshold of $\sim$3 electrons both at a stopped pion source and at a nuclear reactor. Detectable signal rates are larger in the reactor case, but the triggered measurement and harder recoil energy spectrum afforded by the accelerator source enable lower overall background and fiducialisation of the active volume

Особенности функционирования врожденного иммунитета у детей с хронической крапивницей

Aim. To study the features of the functioning of innate immunity in children with chronic idiopathic urticaria.Materials and methods. The study included 28 children of both sexes aged 6–16 years with chronic idiopathic urticaria (CIU). The median age of the patients was 8 years (p = 0.045). Clinical research methods included an analysis of complaints and anamnestic data, as well as an objective examination of the child (dynamics of urticaria, severity of itching, the presence of angioedema). Immunological techniques included determination of the number of monocytes expressing CD14+CD282+, CD14+CD284+, CD14+CD289+, the number of peripheral blood lymphocytes expressing CD3+CD16+, the levels of immunoglobulin (Ig) E, lactoferrin, interferon (IFN) γ, interleukin (IL)4, and IL-6, and a nitroblue tetrazolium test.Results. In the course of the study, an increase in the expression of Toll-like receptors TLR2 and TLR4 by monocytes, a decrease in the expression of TLR9 by monocytes, a significant rise in lactoferrin levels, a slight decrease in the number of natural killer (NK) cells, a decrease in microbicidal activity and adaptive reserves, a rise in IgE levels, a decrease in IL-4 levels, and an increase in IFNγ and IL-6 were revealed in children with CIU.Conclusion. The immunological changes revealed during the study indicate multidirectional expression of Toll-like receptors, disturbances in the work of the cellular components of innate immunity, and a launch of a proinflammatory cytokine cascade in children with CIU, which can serve as a mainstay for the development of new schemes for personalized therapy of CIU in children.Цель. Изучить особенности функционирования врожденного иммунитета у детей с хронической крапивницей (ХК).Материалы и методы. В исследование включены 28 детей обоих полов в возрасте от 6 до 16 лет с хронической идиопатической (спонтанной) крапивницей. Медиана возраста – 8 лет (р = 0,045). Клинические методы исследования: анализ жалоб, анамнестических данных, объективный осмотр ребенка (динамика уртикариев, выраженности кожного зуда, наличие ангиоотеков). Иммунологические методы исследования: определение количества моноцитов, экспрессирующих CD14+CD282+, CD14+CD284+, CD14+CD289+, количества лимфоцитов периферической крови, экспрессирующих CD3+CD16+, содержания иммуноглобулина E, уровня лактоферрина, интерферона (IFN) γ, интерлейкина (IL) 4 и 6, проведение теста с нитросиним тетразолием.Результаты. В ходе исследования у детей с ХК выявлено повышение экспрессии моноцитами Toll-рецепторов TLR2 и TLR4, подавление экспрессии моноцитами TLR9, значительное увеличение уровня лактоферрина, незначительное сокращение количества NK-клеток, снижение микробицидной активности и адаптационных резервов, повышение уровня IgЕ, IFNγ и IL-6, уменьшение уровня IL-4.Заключение. Выявленные в ходе исследования иммунологические изменения свидетельствуют о разнонаправленной экспрессии Toll-рецепторов, нарушениях в работе клеточного звена врожденного иммунитета, запуске цитокинового каскада воспаления у детей с хронической идиопатической крапивницей, что может послужить основой для разработки новых схем персонифицированной терапии ХК у детей

WIMP-nucleon cross-section results from the second science run of ZEPLIN-III

We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1,344 kg.days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7-29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8E-8 pb near 50 GeV/c^2 WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9E-8 pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0E-3 pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach

Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator

Plastic scintillators are widely used in industry, medicine and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 keV and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterise the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semi-empirical formulation of Birks and a kB factor of (0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured quenching factor falls more steeply than predicted by the Birks formalism.Comment: 8 pages, 9 figure

The Inert Doublet Model and Inelastic Dark Matter

The annual modulation observed by DAMA/NaI and DAMA/Libra may be interpreted in terms of elastic or inelastic scattering of dark matter particles. In this paper we confront these two scenarios within the framework of a very simple extension of the Standard Model, the Inert Doublet Model (IDM). In this model the dark matter candidate is a scalar, the lightest component of an extra Higgs doublet. We first revisit the case for the elastic scattering of a light scalar WIMP, M_DM~10 GeV, a scenario which requires that a fraction of events in DAMA are channelled. Second we consider the possibility of inelastic Dark Matter (iDM). This option is technically natural in the IDM, in the sense that the mass splitting between the lightest and next-to-lightest neutral scalars may be protected by a Peccei-Quinn (PQ) symmetry. We show that candidates with a mass M_DM between ~535 GeV and ~50 TeV may reproduce the DAMA data and have a cosmic abundance in agreement with WMAP. This range may be extended to candidates as light as ~50 GeV if we exploit the possibility that the approximate PQ symmetry is effectively conserved and that a primordial asymmetry in the dark sector may survive until freeze-out.Comment: 16 pages, 7 figures. v2: minor changes and discussion on the embedding in SO(10) added. v3: matches the published version in JCA

Dark Matter Spin-Dependent Limits for WIMP Interactions on 19-F by PICASSO

The PICASSO experiment at SNOLAB reports new results for spin-dependent WIMP interactions on $^{19}$F using the superheated droplet technique. A new generation of detectors and new features which enable background discrimination via the rejection of non-particle induced events are described. First results are presented for a subset of two detectors with target masses of $^{19}$F of 65 g and 69 g respectively and a total exposure of 13.75 $\pm$ 0.48 kgd. No dark matter signal was found and for WIMP masses around 24 GeV/c$^2$ new limits have been obtained on the spin-dependent cross section on $^{19}$F of $\sigma_F$ = 13.9 pb (90% C.L.) which can be converted into cross section limits on protons and neutrons of $\sigma_p$ = 0.16 pb and $\sigma_n$ = 2.60 pb respectively (90% C.L). The obtained limits on protons restrict recent interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent interactions.Comment: Revised version, accepted for publication in Phys. Lett. B, 20 pages, 7 figure

ZE3RA: The ZEPLIN-III Reduction and Analysis package

ZE3RA is the software package responsible for processing the raw data from the ZEPLIN-III dark matter experiment and its reduction into a set of parameters used in all subsequent analyses. The detector is a liquid xenon time projection chamber with scintillation and electroluminescence signals read out by an array of 31 photomultipliers. The dual range 62-channel data stream is optimised for the detection of scintillation pulses down to a single photoelectron and of ionisation signals as small as those produced by single electrons. We discuss in particular several strategies related to data filtering, pulse finding and pulse clustering which are tuned using calibration data to recover the best electron/nuclear recoil discrimination near the detection threshold, where most dark matter elastic scattering signatures are expected. The software was designed assuming only minimal knowledge of the physics underlying the detection principle, allowing an unbiased analysis of the experimental results and easy extension to other detectors with similar requirements. ©2011 IOP Publishing Ltd and SISSA

Measurement and simulation of the muon-induced neutron yield in lead

A measurement is presented of the neutron production rate in lead by high energy cosmic-ray muons at a depth of 2850 m water equivalent (w.e.) and a mean muon energy of 260 GeV. The measurement exploits the delayed coincidences between muons and the radiative capture of induced neutrons in a highly segmented tonne scale plastic scintillator detector. Detailed Monte Carlo simulations reproduce well the measured capture times and multiplicities and, within the dynamic range of the instrumentation, the spectrum of energy deposits. By comparing measurements with simulations of neutron capture rates a neutron yield in lead of (View the MathML source) ×10-3 neutrons/muon/(g/cm2) has been obtained. Absolute agreement between simulation and data is of order 25%. Consequences for deep underground rare event searches are discussed

Phenomenology of Light Sneutrino Dark Matter in cMSSM/mSUGRA with Inverse Seesaw

We study the possibility of a light Dark Matter (DM) within a constrained Minimal Supersymmetric Standard Model (cMSSM) framework augmented by a SM singlet-pair sector to account for the non-zero neutrino masses by inverse seesaw mechanism. Working within a 'hybrid' scenario with the MSSM sector fixed at high scale and the singlet neutrino sector at low scale, we find that, contrary to the case of the usual cMSSM where the neutralino DM cannot be very light, we can have a light sneutrino DM with mass below 100 GeV satisfying all the current experimental constraints from cosmology, collider as well as low-energy experiments. We also note that the supersymmetric inverse seesaw mechanism with sneutrino as the lightest supersymmetric partner can have enhanced same-sign dilepton final states with large missing transverse energy (mET) coming from the gluino- and squark-pair as well as the squark-gluino associated productions and their cascade decay through charginos. We present a collider study for the same-sign dilepton+jets+mET signal in this scenario and propose some distinctions with the usual cMSSM. We also comment on the implications of such a light DM scenario on the invisible decay width of an 125 GeV Higgs boson.Comment: 24 pages, 4 figures, 7 tables; matches published versio