Sense and sensitivity of double beta decay experiments

The search for neutrinoless double beta decay is a very active field in which the number of proposals for next-generation experiments has proliferated. In this paper we attempt to address both the sense and the sensitivity of such proposals. Sensitivity comes first, by means of proposing a simple and unambiguous statistical recipe to derive the sensitivity to a putative Majorana neutrino mass, m_bb. In order to make sense of how the different experimental approaches compare, we apply this recipe to a selection of proposals, comparing the resulting sensitivities. We also propose a "physics-motivated range" (PMR) of the nuclear matrix elements as a unifying criterium between the different nuclear models. The expected performance of the proposals is parametrized in terms of only four numbers: energy resolution, background rate (per unit time, isotope mass and energy), detection efficiency, and bb isotope mass. For each proposal, both a reference and an optimistic scenario for the experimental performance are studied. In the reference scenario we find that all the proposals will be able to partially explore the degenerate spectrum, without fully covering it, although four of them (KamLAND-Zen, CUORE, NEXT and EXO) will approach the 50 meV boundary. In the optimistic scenario, we find that CUORE and the xenon-based proposals (KamLAND-Zen, EXO and NEXT) will explore a significant fraction of the inverse hierarchy, with NEXT covering it almost fully. For the long term future, we argue that Xe-based experiments may provide the best case for a 1-ton scale experiment, given the potentially very low backgrounds achievable and the expected scalability to large isotope masses.Comment: 30 pages, 12 figures, 6 table

The relationship between the research performance of scientists and their position in co-authorship networks in three fields

Research networks play a crucial role in the production of new knowledge since collabo-ration contributes to determine the cognitive and social structure of scientific fields andhas a positive influence on research. This paper analyses the structure of co-authorshipnetworks in three different fields (Nanoscience, Pharmacology and Statistics) in Spain overa three-year period (2006–2008) and explores the relationship between the research per-formance of scientists and their position in co-authorship networks. A denser co-authorshipnetwork is found in the two experimental fields than in Statistics, where the network is ofa less connected and more fragmented nature. Using the g-index as a proxy for individualresearch performance, a Poisson regression model is used to explore how performance isrelated to different co-authorship network measures and to disclose interfield differences.The number of co-authors (degree centrality) and the strength of links show a positive rela-tionship with the g-index in the three fields. Local cohesion presents a negative relationshipwith the g-index in the two experimental fields, where open networks and the diversity ofco-authors seem to be beneficial. No clear advantages from intermediary positions (highbetweenness) or from being linked to well-connected authors (high eigenvector) can beinferred from this analysis. In terms of g-index, the benefits derived by authors from theirposition in co-authorship networks are larger in the two experimental fields than in thetheoretical one.AcknowledgementsThis research was supported by the Spanish Ministry of Science and Innovation (MICINN) (research project CSO2008-06310) and the Spanish National Research Council (JAE predoctoral grant and project 201110E087).Peer reviewe

Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction

A Neutrino Factory producing an intense beam composed of nu_e(nubar_e) and nubar_mu(nu_mu) from muon decays has been shown to have the greatest sensitivity to the two currently unmeasured neutrino mixing parameters, theta_13 and delta_CP . Using the `wrong-sign muon' signal to measure nu_e to nu_mu(nubar_e to nubar_mu) oscillations in a 50 ktonne Magnetised Iron Neutrino Detector (MIND) sensitivity to delta_CP could be maintained down to small values of theta_13. However, the detector efficiencies used in previous studies were calculated assuming perfect pattern recognition. In this paper, MIND is re-assessed taking into account, for the first time, a realistic pattern recognition for the muon candidate. Reoptimisation of the analysis utilises a combination of methods, including a multivariate analysis similar to the one used in MINOS, to maintain high efficiency while suppressing backgrounds, ensuring that the signal selection efficiency and the background levels are comparable or better than the ones in previous analyses

Loving to Straighten Out Development: Sexuality and ‘Ethnodevelopment’ in the World Bank’s Ecuadorian Lending

Gender staff in the World Bank -- the world's largest and most influential development institution -- have a policy problem. Having prioritised efforts to get women into paid employment as the "cure-all" for gender inequality they must deal with the work that women already do -- the unpaid labour of caring, socialisation, and human needs fulfilment. This article explores the most prominent policy solution enacted by the Bank to this tension between paid and unpaid work: the restructuring of normative heterosexuality to encourage a two-partner model of love and labour wherein women work more and men care better. Through a case study of Bank gender lending in Ecuador I argue that staff are trying to (re)forge normative arrangements of intimacy, a policy preference that remains invisible unless sexuality is taken seriously as a category of analysis in development studies. Specifically, I focus on four themes that emerge from the attempt to restructure heteronormativity in the loan: (1) the definition of good gender analysis as requiring complementary sharing and dichotomous sex; (2) the Bank's attempt to inculcate limited rationality in women such that they operate as better workers while retaining altruistic attachments to loved ones; (3) the Bank's attempt to inculcate better loving in men, such that they pick up the slack of caring labour when their (partially) rational wives move into productive work, and; (4) the invocation of a racialised hierarchy resting on the extent to which communities approximate ideals of sharing monogamous partnership. Aside from providing clear evidence that the world's largest development institution is involved in micro-processes of sexuality adjustment alongside macro-processes of economic restructuring, I also critique the Bank's sexualised policy interventions and suggest that they warrant contestation

NEXT-100 Technical Design Report (TDR). Executive Summary

In this Technical Design Report (TDR) we describe the NEXT-100 detector that will search for neutrinoless double beta decay (bbonu) in Xe-136 at the Laboratorio Subterraneo de Canfranc (LSC), in Spain. The document formalizes the design presented in our Conceptual Design Report (CDR): an electroluminescence time projection chamber, with separate readout planes for calorimetry and tracking, located, respectively, behind cathode and anode. The detector is designed to hold a maximum of about 150 kg of xenon at 15 bar, or 100 kg at 10 bar. This option builds in the capability to increase the total isotope mass by 50% while keeping the operating pressure at a manageable level. The readout plane performing the energy measurement is composed of Hamamatsu R11410-10 photomultipliers, specially designed for operation in low-background, xenon-based detectors. Each individual PMT will be isolated from the gas by an individual, pressure resistant enclosure and will be coupled to the sensitive volume through a sapphire window. The tracking plane consists in an array of Hamamatsu S10362-11-050P MPPCs used as tracking pixels. They will be arranged in square boards holding 64 sensors (8 times8) with a 1-cm pitch. The inner walls of the TPC, the sapphire windows and the boards holding the MPPCs will be coated with tetraphenyl butadiene (TPB), a wavelength shifter, to improve the light collection.Comment: 32 pages, 22 figures, 5 table