Abbe Brown

Limits on spin-dependent WIMP-nucleon cross sections from 225 live days of XENON100 data

We present new experimental constraints on the elastic, spin-dependent WIMP-nucleon cross section using recent data from the XENON100 experiment, operated in the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 224.6 live days×34 kg of exposure acquired during 2011 and 2012 revealed no excess signal due to axial-vector WIMP interactions with 129Xe and 131Xe nuclei. This leads to the most stringent upper limits on WIMP-neutron cross sections for WIMP masses above 6 GeV/c², with a minimum cross section of 3.5×10(-40) cm² at a WIMP mass of 45 GeV/c², at 90% confidence level.

Observation and applications of single-electron charge signals in the XENON100 experiment

The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter weakly interacting massive particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.

Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment

The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 286 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.

Conceptual design and simulation of a water Cherenkov muon veto for the XENON1T experiment

XENON is a dark matter direct detection project, consisting of a time projection chamber (TPC) filled with liquid xenon as detection medium. The construction of the next generation detector, XENON1T, is presently taking place at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. It aims at a sensitivity to spin-independent cross sections of 2 10-47 c 2 for WIMP masses around 50 GeV2, which requires a background reduction by two orders of magnitude compared to XENON100, the current generation detector. An active system that is able to tag muons and muon-induced backgrounds is critical for this goal. A water Cherenkov detector of ~ 10 m height and diameter has been therefore developed, equipped with 8 inch photomultipliers and cladded by a reflective foil. We present the design and optimization study for this detector, which has been carried out with a series of Monte Carlo simulations. The muon veto will reach very high detection efficiencies for muons (>99.5%) and showers of secondary particles from muon interactions in the rock (>70%). Similar efficiencies will be obtained for XENONnT, the upgrade of XENON1T, which will later improve the WIMP sensitivity by another order of magnitude. With the Cherenkov water shield studied here, the background from muon-induced neutrons in XENON1T is negligible.

The neutron background of the XENON100 dark matter search experiment

The XENON100 experiment, installed underground at the Laboratori Nazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their elastic scattering off xenon nuclei. This paper presents a study on the nuclear recoil background of the experiment, taking into account neutron backgrounds from (α, n) reactions and spontaneous fission due to natural radioactivity in the detector and shield materials, as well as muon-induced neutrons. Based on Monte Carlo simulations and using measured radioactive contaminations of all detector components, we predict the nuclear recoil backgrounds for the WIMP search results published by the XENON100 experiment in 2011 and 2012, 0.11 events and 0.17 events, respectively, and conclude that they do not limit the sensitivity of the experiment.TheXENON100 experiment, installed underground at the LaboratoriNazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their elastic scattering off xenon nuclei. This paper presents a study on the nuclear recoil background of the experiment, taking into account neutron backgrounds from (alpha, n) reactions and spontaneous fission due to natural radioactivity in the detector and shield materials, as well as muon-induced neutrons. Based on MonteCarlo simulations and using measured radioactive contaminations of all detector components, we predict the nuclear recoil backgrounds for the WIMP search results published by theXENON100 experiment in 2011 and 2012, 0.11(-0.04)(+0.08) events and 0.17(-0.07)(+0.12) events, respectively, and conclude that they do not limit the sensitivity of the experiment.

Sustainability through an integrated approach to decision making? A law and regulation case study

Many legal fields are relevant to all kinds of problems; however, decision makers often take a narrow approach, looking only at the base of the claim or the issue they are established to consider. This can led to imbalanced outcomes. There is a particular risk of this in respect of decisions regarding key societal challenges, which might be the subject of law and policymaking from several different perspectives. This paper explores the need and bases for a more integrated approach to decision making. It does so using a case study, and explores a range of laws that could be relevant to a business seeking to use technology and resources that could address climate change, the different decisions that courts can make (with a focus on the nature of the action, outcome and forum), and the resulting conflicts, synergies and areas of enquiry.

Bodily extensions and performance

In contemporary technological society, bodily extension has become a regular occurrence for many people. Extensions can attach to or connect with human bodies to adjust, change or augment them in physical or virtual spaces, including artificial limbs, contact lenses and digital avatars. They can be as hi-tech as a surgeon manipulating a device to operate remotely on a patient in another country, as media-present as a Paralympic athlete with running blades, or as everyday as a blind person using a stick. We might use extensions ourselves or witness others using them in workplaces, social environments, at home, and in the media. They may be perceived as enabling tools by some, replacing or augmenting body parts, capacities or abilities, perhaps leading to superhuman feats (Thompson 2012). However, others may see them as disabling restrictions, with their use enforced by social or cultural expectations about what a body should be (Betcher 2001). Inevitably, extensions are incorporated into body images and implicated in social identities (Serlin 2004). This Special Issue on ‘Bodily Extensions and Performance’ raises critical questions about the nature of extended bodies and body-technology practices. The six essays are concerned with the lived experiences of such bodies, highlighting processes of incorporation and hybridity (Donnarumma), influence and exchange (O’Brien), blurring and entanglement (Wilson), shifting identities (Riszko), destabilisation and metamorphosis (Stępień) and defamiliarisation of the everyday (Sobchack). The increasingly complex blending of bodies and technologies has corresponded with a rise in the intellectual popularity of the cultural theories of posthumanism and new materialism. These philosophies offer direct monist challenges to the dualist tendencies of humanist perspectives, denying priority of mind over matter, and of flesh over other forms of material (Dolphijn and van der Tuin 2012; Braidotti 2013). ‘Bodily Extensions and Performance’ was an intentionally provocative choice of title for this issue, given that ‘bodily extension’ implies the centrality of a body to be extended, and at least one of our authors has responded by rejecting this conceptualisation. Yet we argue that neither monist nor dualist perspectives are able to appreciate experiences of bodily extension. In theories and practices of performance, bodies are well recognised as sites of knowledge. The importance of sensory perception, including the internal senses of proprioception and kinaesthesia, is understood in relation to the specific communication of affect and empathy (Massumi 2002; Reynolds and Reason 2012). If we are to understand what it means to live as flesh-technology entities, and to grasp the sensory and ethical implications thereof, performance is an important disciplinary arena in which to debate questions of bodily experience. The articles in this Special Issue address the coming together of flesh and other materials, acknowledging processes of assembly and the influence of interfaces in the fluid becoming of embodied extended beings. Bodies are accustomed to extending their internal sensory fields to include other materials, with the blind person’s stick as a prime example. Kinaesthetic and proprioceptive senses can be pushed out into those extensions with surprising alacrity

Commissioning of a dual-phase xenon TPC at Nikhef

A dual-phase xenon time-projection chamber was built at Nikhef in Amsterdam as a direct dark matter detection R&D facility. In this paper, the setup is presented and the first results from a calibration with a 22Na gamma-ray source are presented. The results show an average light yield of (5.6±0.3) photoelectrons/keV (calculated to 122 keV and zero field) and an electron lifetime of (429±26) μs. The best energy resolution σE/E is (5.8±0.2)% at an energy of 511 keV. This was achieved using a combination of the scintillation and the ionization signals. A photomultiplier tube gain calibration technique, based on the electroluminescence signals occurring from isolated electrons, is presented and its advantages and limitations are discussed.

Access to essential technologies: The role of the interface between intellectual property, competition and human rights

Intellectual property (IP) can stimulate innovation but it can also impose restrictions on the wider development of and access to essential technologies. Yet IP should be viewed within the context of a larger legal framework, which includes the laws of human rights and competition. This article introduces these laws into this larger framework and explores their relationship with IP. The article reviews steps which have been taken at policy level to manage the impact of IP, notably the draft Access to Knowledge Treaty, and the new contribution which could be made using human rights and competition law. It then proposes further amendment of TRIPS (the Agreement on Trade Related Aspects of Intellectual Property Rights) as the most effective approach to securing a new place for IP and discusses the challenges which may be encountered.

Body Extension and the Law: Medical Devices, Intellectual Property, Prosthetics and Marginalisation (Again)

ABSTRACT This interdisciplinary paper, drawing on empirical and doctrinal research regarding artificial limbs and digital avatars, analyses two concepts which are argued to be core to the person – integrity and identity. From the perspective of a person who is a prosthetic user, the paper then evaluates the extent to which two legal regimes which are highly relevant to prosthetics, medical devices regulation (and its delivery) and intellectual property (and its power), engage with the person, integrity and identity with a focus on approaches taken to authority and control. The paper criticises the meaning which law generates regarding the person. It calls for new approaches to be taken by the legal regimes explored to the person, identity and integrity; and for a new multifaceted interdisciplinary driven approach to the person.