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ZEPLIN-III

May 09, 2024

The ZEPLIN-III dark matter experiment attempted to detect galactic WIMPs using a 12 kg liquid xenon target. It operated from 2006 to 2011 at the Boulby Underground Laboratory in Loftus, North Yorkshire. This was the last in a series of xenon-based experiments in the ZEPLIN programme pursued originally by the UK Dark Matter Collaboration (UKDMC). The ZEPLIN-III project was led by Imperial College London and also included the Rutherford Appleton Laboratory and the University of Edinburgh in the UK, as well as LIP-Coimbra in Portugal and ITEP-Moscow in Russia. It ruled out cross-sections for elastic scattering of WIMPs off nucleons above 3.9 × 10−8 pb (3.9 × 10−44 cm2) from the two science runs conducted at Boulby (83 days in 2008 and 319 days in 2010/11).

ZEPLIN-III experiment: the WIMP detector, built mainly out of copper, included two chambers within a cryostat vessel: the upper one contained 12 kg of active liquid xenon; an array of 31 photomultipliers operated immersed in the liquid to detect prompt scintillation as well as delayed electroluminescence from a thin gas layer above the liquid. The lower chamber contained liquid nitrogen to provide cooling. The detector was surrounded by Gd-loaded polypropylene to moderate and capture neutrons, a potential source of background. The gamma-rays from neutron capture were detected by 52 modules of plastic scintillator placed around the moderator. The shielding was completed by a 20-cm thick lead castle.

Direct dark matter search experiments look for extremely rare and very weak collisions expected to occur between the cold dark matter particles that are believed to permeate our galaxy and the nuclei of atoms in the active medium of a radiation detector. These hypothetical elementary particles could be Weakly Interacting Massive Particles, or WIMPs, weighing as little as a few protons or as much as several heavy nuclei. Their nature is not yet known, but no sensible candidates remain within the Standard Model of particle physics to explain the dark matter problem.

Detection technology edit

Condensed noble gases, most notably liquid xenon and liquid argon, are excellent radiation detection media. They can produce two signatures for each particle interaction: a fast flash of light (scintillation) and the local release of charge (ionisation). In two-phase xenon – so called since it involves liquid and gas phases in equilibrium – the scintillation light produced by an interaction in the liquid is detected directly with photomultiplier tubes; the ionisation electrons released at the interaction site are drifted up to the liquid surface under an external electric field, and subsequently emitted into a thin layer of xenon vapour. Once in the gas, they generate a second, larger pulse of light (electroluminescence or proportional scintillation), which is detected by the same array of photomultipliers. These systems are also known as xenon 'emission detectors'.[1]

This configuration is that of a time projection chamber (TPC); it allows three-dimensional reconstruction of the interaction site, since the depth coordinate (z) can be measured very accurately from the time separation between the two light pulses. The horizontal coordinates can be reconstructed from the hit pattern in the photomultiplier array(s). Critically for WIMP searches, the ratio between the two response channels (scintillation and ionisation) allows the rejection of the predominant backgrounds for WIMP searches: gamma and beta radiation from trace radioactivity in detector materials and the immediate surroundings. WIMP candidate events produce lower ionisation/scintillation ratios than the more prevalent background interactions.

The ZEPLIN programme pioneered the use of two-phase technology for WIMP searches. The technique itself, however, was first developed for radiation detection using argon in the early 1970s.[1] Lebedenko, one of its pioneers at the Moscow Engineering Physics Institute, was involved in building ZEPLIN-III in the UK from 2001. Developed alongside it, but on a faster timescale, ZEPLIN-II was the first such WIMP detector to operate in the world (2005).[2] This technology was also adopted very successfully by the XENON programme. Two-phase argon has also been used for dark matter searches by the WARP collaboration and ArDM. LUX is developing similar systems that have set improved limits.

 
Signal from ZEPLIN-III two-phase xenon detector. The fast scintillation pulse (S1) is generated promptly by scintillation in the liquid; a larger, delayed pulse (S2) is obtained once the ionisation drifted from the interaction site is emitted into the thin gas phase above the liquid. The insets below the signal traces show Monte Carlo simulation of the optical signals.

History edit

The ZEPLIN (ZonEd Proportional scintillation in LIquid Noble gases) series of experiments was a progressive programme pursued by the UK Dark Matter Collaboration using liquid xenon. It evolved alongside the DRIFT programme which promoted the use of gas-filled TPCs to recover directional information on WIMP scattering. In the late 1980s the UKDMC had explored the potential of different materials and techniques, including cryogenic LiF, CaF2, silicon and germanium, from which a programme emerged at Boulby based on room-temperature NaI(Tl) scintillators.[3] The subsequent move to a new target material, liquid xenon, was motivated by the realisation that noble liquid targets are inherently more scalable and could achieve lower energy thresholds and better background discrimination.[4] In particular, external layers of the bulk target, affected more by external backgrounds, can be sacrificed during data analysis if the position of the interactions in known; this leaves an inner fiducial volume with potentially very low background rates. This self-shielding effect (alluded to by the 'zoned' term in the contrived ZEPLIN acronym) explains the faster gain in sensitivity of these targets compared to technologies based on a modular approach adopted with crystal detectors, where each module brings its own background.

ZEPLIN-I, a 3 kg liquid xenon target, operated at Boulby from the late 1990s.[5] It used pulse shape discrimination for background rejection, exploiting a small but helpful difference between the timing properties of the scintillation light caused by WIMPs and background interactions. This was followed by two-phase systems ZEPLIN-II and ZEPLIN-III, which were designed and built in parallel at RAL/UCLA and Imperial College, respectively.

ZEPLIN-II was the first two-phase system deployed to search for dark matter in the world;[2] it consisted of a 30 kg liquid xenon target topped by a 3 mm layer of gas in a so-called three-electrode configuration: separate electric fields were applied to the bulk of the liquid (WIMP target) and to the gas region above it by using an extra electrode underneath the liquid surface (in addition to an anode grid, located above the gas, and a cathode, at the bottom of the chamber). In ZEPLIN-II an array of 7 photomultipliers viewed the chamber from above in the gas phase.

ZEPLIN-III was proposed in the late 1990s,[6] based partly on a similar concept developed at ITEP,[7] and built by Prof. Tim Sumner and his team at Imperial College. It was deployed underground at Boulby in late 2006, where it operated until 2011. It was a two-electrode chamber, where electron emission into the gas was achieved by a strong (4 kV/cm) field in the liquid bulk rather than by an additional electrode. The photomultiplier array contained 31 photon detectors viewing the WIMP target from below, immersed in the cold liquid xenon.[8]

ZEPLIN–II and –III were purposely designed in different ways, so that the technologies employed in each sub-system could be appraised and selected for the final experiment proposed by the UKDMC: a tonne-scale xenon target (ZEPLIN-MAX) capable of probing most of the parameter space favored by theory at that point (1 × 10−10 pb), although this latter system was never built in the UK for lack of funding.

Results edit

Although the ZEPLIN-III liquid xenon target was built on the same scale as that of its ZEPLIN predecessors, it achieved significant improvements in WIMP sensitivity due to the higher discrimination factor achieved and to a lower overall background. In 2011 it published exclusion limits on the spin-independent WIMP-nucleon elastic scattering cross-section above 3.9 × 10−8 pb for a 50 GeV WIMP mass.[9] Although not as stringent as results from XENON100,[10] this was achieved with a 10 times smaller fiducial mass and demonstrated the best background discrimination ever achieved in these detectors. The WIMP-neutron spin-dependent cross-section was excluded above 8.0 × 10−3 pb.[11][12] It also ruled out an inelastic WIMP scattering model which attempted to reconcile a positive claim from DAMA with the absence of signal in other experiments.[13]

References edit

  1. ^ a b B. A. Dolgoshein, V. N. Lebedenko & B. I. Rodionov, "New method of registration of ionizing-particle tracks in condensed matter", JETP Lett. 11(11): 351 (1970)
  2. ^ a b Alner, G.J.; Araújo, H.M.; Bewick, A.; Bungau, C.; Camanzi, B.; et al. (2007). "First limits on WIMP nuclear recoil signals in ZEPLIN-II: A two-phase xenon detector for dark matter detection". Astroparticle Physics. 28 (3): 287–302. arXiv:astro-ph/0701858. Bibcode:2007APh....28..287A. doi:10.1016/j.astropartphys.2007.06.002. ISSN 0927-6505. S2CID 1044263.
  3. ^ See full UKDMC reference list in http://hepwww.rl.ac.uk/ukdmc/pub/fulpub.html
  4. ^ Davies, G.J.; Davies, J.D.; Lewin, J.D.; Smith, P.F.; Jones, W.G. (1994). "Liquid xenon as a dark matter detector. Prospects for nuclear recoil discrimination by photon timing". Physics Letters B. 320 (3–4). Elsevier BV: 395–399. Bibcode:1994PhLB..320..395D. doi:10.1016/0370-2693(94)90676-9. ISSN 0370-2693.
  5. ^ Alner, G.J.; Araujo, H.; Arnison, G.J.; Barton, J.C.; Bewick, A.; et al. (2005). "First limits on nuclear recoil events from the ZEPLIN I galactic dark matter detector". Astroparticle Physics. 23 (5). Elsevier BV: 444–462. Bibcode:2005APh....23..444U. doi:10.1016/j.astropartphys.2005.02.004. ISSN 0927-6505.
  6. ^ T. J. Sumner et al., "ZEPLIN-III: a two-phase xenon dark matter detector, in: Proc. 3rd Int. Workshop. Id. Dark Matter, Spooner & Kudryavtsev (Eds): World Scientific, pp. 452–456 (2001)
  7. ^ D. Yu. Akimov et al., "Scintillation two-phase xenon detector with gamma and electron-background rejection for dark matter search", in: Sources and Detection of Dark Matter in the Universe: North Holland, pp. 461–464 (1998)
  8. ^ AKIMOV, D; ALNER, G; ARAUJO, H; BEWICK, A; BUNGAU, C; et al. (2007). "The ZEPLIN-III dark matter detector: Instrument design, manufacture and commissioning". Astroparticle Physics. 27 (1): 46–60. arXiv:astro-ph/0605500. Bibcode:2007APh....27...46A. doi:10.1016/j.astropartphys.2006.09.005. hdl:10316/4383. ISSN 0927-6505. S2CID 11911700.
  9. ^ Akimov, D.Yu.; Araújo, H.M.; Barnes, E.J.; Belov, V.A.; Bewick, A.; et al. (2012). "WIMP-nucleon cross-section results from the second science run of ZEPLIN-III". Physics Letters B. 709 (1–2). Elsevier BV: 14–20. arXiv:1110.4769. Bibcode:2012PhLB..709...14A. doi:10.1016/j.physletb.2012.01.064. ISSN 0370-2693. S2CID 14136134.
  10. ^ Aprile, E.; Arisaka, K.; Arneodo, F.; Askin, A.; Baudis, L.; et al. (19 September 2011). "Dark Matter Results from 100 Live Days of XENON100 Data". Physical Review Letters. 107 (13): 131302. arXiv:1104.2549. Bibcode:2011PhRvL.107m1302A. doi:10.1103/physrevlett.107.131302. ISSN 0031-9007. PMID 22026838. S2CID 9685630.
  11. ^ Lebedenko, V. N.; Araújo, H. M.; Barnes, E. J.; Bewick, A.; Cashmore, R.; et al. (25 September 2009). "Results from the first science run of the ZEPLIN-III dark matter search experiment". Physical Review D. 80 (5): 052010. arXiv:0812.1150. Bibcode:2009PhRvD..80e2010L. doi:10.1103/physrevd.80.052010. ISSN 1550-7998. S2CID 119237969.
  12. ^ Lebedenko, V. N.; Araújo, H. M.; Barnes, E. J.; Bewick, A.; Cashmore, R.; et al. (8 October 2009). "Limits on the Spin-Dependent WIMP-Nucleon Cross Sections from the First Science Run of the ZEPLIN-III Experiment". Physical Review Letters. 103 (15): 151302. arXiv:0901.4348. Bibcode:2009PhRvL.103o1302L. doi:10.1103/physrevlett.103.151302. ISSN 0031-9007. PMID 19905617. S2CID 1349055.
  13. ^ Akimov, D.Yu.; Araújo, H.M.; Barnes, E.J.; Belov, V.A.; Bewick, A.; et al. (2010). "Limits on inelastic dark matter from ZEPLIN-III". Physics Letters B. 692 (3): 180–183. arXiv:1003.5626. Bibcode:2010PhLB..692..180A. doi:10.1016/j.physletb.2010.07.042. ISSN 0370-2693. S2CID 67836272.

External links edit

  • ZEPLIN-III Project
  • Boulby Underground Laboratory
  • UK Dark Matter Collaboration

54°33′12″N 0°49′28″W / 54.5534°N 0.8245°W / 54.5534; -0.8245

May 09, 2024
zeplin, dark, matter, experiment, attempted, detect, galactic, wimps, using, liquid, xenon, target, operated, from, 2006, 2011, boulby, underground, laboratory, loftus, north, yorkshire, this, last, series, xenon, based, experiments, zeplin, programme, pursued. The ZEPLIN III dark matter experiment attempted to detect galactic WIMPs using a 12 kg liquid xenon target It operated from 2006 to 2011 at the Boulby Underground Laboratory in Loftus North Yorkshire This was the last in a series of xenon based experiments in the ZEPLIN programme pursued originally by the UK Dark Matter Collaboration UKDMC The ZEPLIN III project was led by Imperial College London and also included the Rutherford Appleton Laboratory and the University of Edinburgh in the UK as well as LIP Coimbra in Portugal and ITEP Moscow in Russia It ruled out cross sections for elastic scattering of WIMPs off nucleons above 3 9 10 8 pb 3 9 10 44 cm2 from the two science runs conducted at Boulby 83 days in 2008 and 319 days in 2010 11 ZEPLIN III experiment the WIMP detector built mainly out of copper included two chambers within a cryostat vessel the upper one contained 12 kg of active liquid xenon an array of 31 photomultipliers operated immersed in the liquid to detect prompt scintillation as well as delayed electroluminescence from a thin gas layer above the liquid The lower chamber contained liquid nitrogen to provide cooling The detector was surrounded by Gd loaded polypropylene to moderate and capture neutrons a potential source of background The gamma rays from neutron capture were detected by 52 modules of plastic scintillator placed around the moderator The shielding was completed by a 20 cm thick lead castle Direct dark matter search experiments look for extremely rare and very weak collisions expected to occur between the cold dark matter particles that are believed to permeate our galaxy and the nuclei of atoms in the active medium of a radiation detector These hypothetical elementary particles could be Weakly Interacting Massive Particles or WIMPs weighing as little as a few protons or as much as several heavy nuclei Their nature is not yet known but no sensible candidates remain within the Standard Model of particle physics to explain the dark matter problem Contents 1 Detection technology 2 History 3 Results 4 References 5 External linksDetection technology editCondensed noble gases most notably liquid xenon and liquid argon are excellent radiation detection media They can produce two signatures for each particle interaction a fast flash of light scintillation and the local release of charge ionisation In two phase xenon so called since it involves liquid and gas phases in equilibrium the scintillation light produced by an interaction in the liquid is detected directly with photomultiplier tubes the ionisation electrons released at the interaction site are drifted up to the liquid surface under an external electric field and subsequently emitted into a thin layer of xenon vapour Once in the gas they generate a second larger pulse of light electroluminescence or proportional scintillation which is detected by the same array of photomultipliers These systems are also known as xenon emission detectors 1 This configuration is that of a time projection chamber TPC it allows three dimensional reconstruction of the interaction site since the depth coordinate z can be measured very accurately from the time separation between the two light pulses The horizontal coordinates can be reconstructed from the hit pattern in the photomultiplier array s Critically for WIMP searches the ratio between the two response channels scintillation and ionisation allows the rejection of the predominant backgrounds for WIMP searches gamma and beta radiation from trace radioactivity in detector materials and the immediate surroundings WIMP candidate events produce lower ionisation scintillation ratios than the more prevalent background interactions The ZEPLIN programme pioneered the use of two phase technology for WIMP searches The technique itself however was first developed for radiation detection using argon in the early 1970s 1 Lebedenko one of its pioneers at the Moscow Engineering Physics Institute was involved in building ZEPLIN III in the UK from 2001 Developed alongside it but on a faster timescale ZEPLIN II was the first such WIMP detector to operate in the world 2005 2 This technology was also adopted very successfully by the XENON programme Two phase argon has also been used for dark matter searches by the WARP collaboration and ArDM LUX is developing similar systems that have set improved limits nbsp Signal from ZEPLIN III two phase xenon detector The fast scintillation pulse S1 is generated promptly by scintillation in the liquid a larger delayed pulse S2 is obtained once the ionisation drifted from the interaction site is emitted into the thin gas phase above the liquid The insets below the signal traces show Monte Carlo simulation of the optical signals History editThe ZEPLIN ZonEd Proportional scintillation in LIquid Noble gases series of experiments was a progressive programme pursued by the UK Dark Matter Collaboration using liquid xenon It evolved alongside the DRIFT programme which promoted the use of gas filled TPCs to recover directional information on WIMP scattering In the late 1980s the UKDMC had explored the potential of different materials and techniques including cryogenic LiF CaF2 silicon and germanium from which a programme emerged at Boulby based on room temperature NaI Tl scintillators 3 The subsequent move to a new target material liquid xenon was motivated by the realisation that noble liquid targets are inherently more scalable and could achieve lower energy thresholds and better background discrimination 4 In particular external layers of the bulk target affected more by external backgrounds can be sacrificed during data analysis if the position of the interactions in known this leaves an inner fiducial volume with potentially very low background rates This self shielding effect alluded to by the zoned term in the contrived ZEPLIN acronym explains the faster gain in sensitivity of these targets compared to technologies based on a modular approach adopted with crystal detectors where each module brings its own background ZEPLIN I a 3 kg liquid xenon target operated at Boulby from the late 1990s 5 It used pulse shape discrimination for background rejection exploiting a small but helpful difference between the timing properties of the scintillation light caused by WIMPs and background interactions This was followed by two phase systems ZEPLIN II and ZEPLIN III which were designed and built in parallel at RAL UCLA and Imperial College respectively ZEPLIN II was the first two phase system deployed to search for dark matter in the world 2 it consisted of a 30 kg liquid xenon target topped by a 3 mm layer of gas in a so called three electrode configuration separate electric fields were applied to the bulk of the liquid WIMP target and to the gas region above it by using an extra electrode underneath the liquid surface in addition to an anode grid located above the gas and a cathode at the bottom of the chamber In ZEPLIN II an array of 7 photomultipliers viewed the chamber from above in the gas phase ZEPLIN III was proposed in the late 1990s 6 based partly on a similar concept developed at ITEP 7 and built by Prof Tim Sumner and his team at Imperial College It was deployed underground at Boulby in late 2006 where it operated until 2011 It was a two electrode chamber where electron emission into the gas was achieved by a strong 4 kV cm field in the liquid bulk rather than by an additional electrode The photomultiplier array contained 31 photon detectors viewing the WIMP target from below immersed in the cold liquid xenon 8 ZEPLIN II and III were purposely designed in different ways so that the technologies employed in each sub system could be appraised and selected for the final experiment proposed by the UKDMC a tonne scale xenon target ZEPLIN MAX capable of probing most of the parameter space favored by theory at that point 1 10 10 pb although this latter system was never built in the UK for lack of funding Results editAlthough the ZEPLIN III liquid xenon target was built on the same scale as that of its ZEPLIN predecessors it achieved significant improvements in WIMP sensitivity due to the higher discrimination factor achieved and to a lower overall background In 2011 it published exclusion limits on the spin independent WIMP nucleon elastic scattering cross section above 3 9 10 8 pb for a 50 GeV WIMP mass 9 Although not as stringent as results from XENON100 10 this was achieved with a 10 times smaller fiducial mass and demonstrated the best background discrimination ever achieved in these detectors The WIMP neutron spin dependent cross section was excluded above 8 0 10 3 pb 11 12 It also ruled out an inelastic WIMP scattering model which attempted to reconcile a positive claim from DAMA with the absence of signal in other experiments 13 References edit a b B A Dolgoshein V N Lebedenko amp B I Rodionov New method of registration of ionizing particle tracks in condensed matter JETP Lett 11 11 351 1970 a b Alner G J Araujo H M Bewick A Bungau C Camanzi B et al 2007 First limits on WIMP nuclear recoil signals in ZEPLIN II A two phase xenon detector for dark matter detection Astroparticle Physics 28 3 287 302 arXiv astro ph 0701858 Bibcode 2007APh 28 287A doi 10 1016 j astropartphys 2007 06 002 ISSN 0927 6505 S2CID 1044263 See full UKDMC reference list in http hepwww rl ac uk ukdmc pub fulpub html Davies G J Davies J D Lewin J D Smith P F Jones W G 1994 Liquid xenon as a dark matter detector Prospects for nuclear recoil discrimination by photon timing Physics Letters B 320 3 4 Elsevier BV 395 399 Bibcode 1994PhLB 320 395D doi 10 1016 0370 2693 94 90676 9 ISSN 0370 2693 Alner G J Araujo H Arnison G J Barton J C Bewick A et al 2005 First limits on nuclear recoil events from the ZEPLIN I galactic dark matter detector Astroparticle Physics 23 5 Elsevier BV 444 462 Bibcode 2005APh 23 444U doi 10 1016 j astropartphys 2005 02 004 ISSN 0927 6505 T J Sumner et al ZEPLIN III a two phase xenon dark matter detector in Proc 3rd Int Workshop Id Dark Matter Spooner amp Kudryavtsev Eds World Scientific pp 452 456 2001 D Yu Akimov et al Scintillation two phase xenon detector with gamma and electron background rejection for dark matter search in Sources and Detection of Dark Matter in the Universe North Holland pp 461 464 1998 AKIMOV D ALNER G ARAUJO H BEWICK A BUNGAU C et al 2007 The ZEPLIN III dark matter detector Instrument design manufacture and commissioning Astroparticle Physics 27 1 46 60 arXiv astro ph 0605500 Bibcode 2007APh 27 46A doi 10 1016 j astropartphys 2006 09 005 hdl 10316 4383 ISSN 0927 6505 S2CID 11911700 Akimov D Yu Araujo H M Barnes E J Belov V A Bewick A et al 2012 WIMP nucleon cross section results from the second science run of ZEPLIN III Physics Letters B 709 1 2 Elsevier BV 14 20 arXiv 1110 4769 Bibcode 2012PhLB 709 14A doi 10 1016 j physletb 2012 01 064 ISSN 0370 2693 S2CID 14136134 Aprile E Arisaka K Arneodo F Askin A Baudis L et al 19 September 2011 Dark Matter Results from 100 Live Days of XENON100 Data Physical Review Letters 107 13 131302 arXiv 1104 2549 Bibcode 2011PhRvL 107m1302A doi 10 1103 physrevlett 107 131302 ISSN 0031 9007 PMID 22026838 S2CID 9685630 Lebedenko V N Araujo H M Barnes E J Bewick A Cashmore R et al 25 September 2009 Results from the first science run of the ZEPLIN III dark matter search experiment Physical Review D 80 5 052010 arXiv 0812 1150 Bibcode 2009PhRvD 80e2010L doi 10 1103 physrevd 80 052010 ISSN 1550 7998 S2CID 119237969 Lebedenko V N Araujo H M Barnes E J Bewick A Cashmore R et al 8 October 2009 Limits on the Spin Dependent WIMP Nucleon Cross Sections from the First Science Run of the ZEPLIN III Experiment Physical Review Letters 103 15 151302 arXiv 0901 4348 Bibcode 2009PhRvL 103o1302L doi 10 1103 physrevlett 103 151302 ISSN 0031 9007 PMID 19905617 S2CID 1349055 Akimov D Yu Araujo H M Barnes E J Belov V A Bewick A et al 2010 Limits on inelastic dark matter from ZEPLIN III Physics Letters B 692 3 180 183 arXiv 1003 5626 Bibcode 2010PhLB 692 180A doi 10 1016 j physletb 2010 07 042 ISSN 0370 2693 S2CID 67836272 External links editZEPLIN III Project Boulby Underground Laboratory UK Dark Matter Collaboration 54 33 12 N 0 49 28 W 54 5534 N 0 8245 W 54 5534 0 8245 Retrieved from https en wikipedia org w index php title ZEPLIN III amp oldid 1112516974 History, wikipedia, wiki, book, books, library,

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