Probing the Local Velocity Distribution of WIMP Dark Matter with Directional Detectors

We explore the ability of directional nuclear-recoil detectors to constrain the local velocity distribution of weakly interacting massive particle (WIMP) dark matter by performing Bayesian parameter estimation on simulated recoil-event data sets. We discuss in detail how directional information, when combined with measurements of the recoil-energy spectrum, helps break degeneracies in the velocity-distribution parameters. We also consider the possibility that velocity structures such as cold tidal streams or a dark disk may also be present in addition to the Galactic halo. Assuming a carbon-tetrafluoride detector with a 30-kg-yr exposure, a 50-GeV WIMP mass, and a WIMP-nucleon spin-dependent cross-section of 0.001 pb, we show that the properties of a cold tidal stream may be well constrained. However, measurement of the parameters of a dark-disk component with a low lag speed of ~50 km/s may be challenging unless energy thresholds are improved.Comment: 38 pages, 15 figure

Snow White in different guises: Interlingual and intercultural exchanges between grandparents and young children at home in East London

Grandparents play a significant role in childcare and one activity that frequently occurs within this context is story-reading. However, relatively little attention has been given to the potential part that grandparents can play in terms of language and literacy development of young children.This article reports on work investigating the interlingual and intercultural exchanges occurring in a home setting in East London. In particular, it focuses on how the traditional heritage pattern of story and rhyme reading by a grandmother of Bengali origin is fused with practices experienced by her six-year old grandchild.The data reveal not only the multiple worlds inhabited by the grandchild during story-reading but also the syncretism of these worlds on a number of levels.This article contributes to the small but growing body of investigation into the reading styles occurring within families from different cultural backgrounds

Getting the baby on a schedule: Dutch and American mothers' ethnotheories and the establishment of diurnal rhythms in early infancy

One of the earliest challenges for infants and their parents is developing a diurnal sleep-wake cycle. Although the human biological rhythm is circadian by nature, its development varies across cultures, based in part on "zeitgebers" (German: literally "time-givers") or environmental cues. This study uses the developmental niche framework by Super and Harkness to address two different approaches to getting the baby on a schedule. 33 Dutch and 41 U.S. mothers were interviewed when their babies were 2 and 6 months old. A mixed-methods analysis including counts of themes and practices as well as the examination of actual quotes shows that Dutch mothers emphasized the importance of regularity in the baby's daily life and mentioned practices to establish regular schedules for the baby's sleeping, eating, and time outside more than American mothers did. The U.S. mothers, in contrast, discussed regularity less often and when they did, they emphasized that their baby should develop his or her own schedule. Furthermore, actual daily schedules, based on time allocation diaries kept by the mothers, revealed greater regularity among the Dutch babies. Discussion focuses on how culture shapes the development of diurnal rhythms, with implications for "best practices" for infant care

Getting the baby on a schedule: Dutch and American Mothers’ Ethnotheories and the Establishment of Diurnal Rhythms in Early Infancy

One of the earliest challenges for infants and their parents is developing a diurnal sleep–wake cycle. Although the human biological rhythm is circadian by nature, its development varies across cultures, based in part on “zeitgebers” (German: literally “time‐givers”) or environmental cues. This study uses the developmental niche framework by Super and Harkness to address two different approaches to getting the baby on a schedule. 33 Dutch and 41 U.S. mothers were interviewed when their babies were 2 and 6 months old. A mixed‐methods analysis including counts of themes and practices as well as the examination of actual quotes shows that Dutch mothers emphasized the importance of regularity in the baby's daily life and mentioned practices to establish regular schedules for the baby's sleeping, eating, and time outside more than American mothers did. The U.S. mothers, in contrast, discussed regularity less often and when they did, they emphasized that their baby should develop his or her own schedule. Furthermore, actual daily schedules, based on time allocation diaries kept by the mothers, revealed greater regularity among the Dutch babies. Discussion focuses on how culture shapes the development of diurnal rhythms, with implications for “best practices” for infant care

Measuring pion beta decay with high-energy pion beams

Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay [pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon] is predicted by the Standard Model (SM) to be R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.3999[plus minus]0.0005 s[sup [minus]1]. The best experimental number, obtained using in-flight decays, is R([pi][sup +] [yields] [pi][sup 0]e[sup +]v[epsilon]) = 0.394 [plus minus] 0.015 s[sup [minus]1]. A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required