Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radioactivity Backgrounds in ZEPLIN-III   We examine electron and nuclear recoil backgrounds from radioactivity in the
ZEPLIN-III dark matter experiment at Boulby. The rate of low-energy electron
recoils in the liquid xenon WIMP target is 0.75$\pm$0.05 events/kg/day/keV,
which represents a 20-fold improvement over the rate observed during the first
science run. Energy and spatial distributions agree with those predicted by
component-level Monte Carlo simulations propagating the effects of the
radiological contamination measured for materials employed in the experiment.
Neutron elastic scattering is predicted to yield 3.05$\pm$0.5 nuclear recoils
with energy 5-50 keV per year, which translates to an expectation of 0.4 events
in a 1-year dataset in anti-coincidence with the veto detector for realistic
signal acceptance. Less obvious background sources are discussed, especially in
the context of future experiments. These include contamination of scintillation
pulses with Cherenkov light from Compton electrons and from $\beta$ activity
internal to photomultipliers, which can increase the size and lower the
apparent time constant of the scintillation response. Another challenge is
posed by multiple-scatter $\gamma$-rays with one or more vertices in regions
that yield no ionisation. If the discrimination power achieved in the first run
can be replicated, ZEPLIN-III should reach a sensitivity of $\sim 1 \times
10^{-8}$ pb$\cdot$year to the scalar WIMP-nucleon elastic cross-section, as
originally conceived.

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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th