83 research outputs found
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Issues for high-luminosity fixed-target rare-B-decay experiments
Fermilab E789 is the prototype of a new approach to the study of heavy-quark decays using fixed target. The apparatus acceptance is restricted to charged particles of relatively large momentum emerging at relatively large angles, allowing operation at high interaction rates. At rates up to 10 interactions per RF-bucket, the experiment may have sensitivity at the level of 10{sup {minus}6} per running period for such rare decay modes as B {yields} {pi}{sup +}{pi}{sup {minus}}. Could such an approach be extended to give sensitivity to standard-model CP violation in the beauty sector Since the predicted CP asymmetry in B {yields} {pi}{sup +}{pi}{sup {minus}} is of order 10{sup {minus}1}, this is a particularly attractive mode to consider. The simplest CP asymmetry would be a difference in absolute rates for B{sup 0} {yields} {pi}{sup +}{pi}{sup {minus}} and {ovr B{sup 0}} {yields} {pi}{sup +}{pi}{sup {minus}}, requiring tagging of the b-quark charge for its observation. Assuming a plausible branching ratio of 10{sup {minus}5} for B {yields} {pi}{sup +}{pi}{sup {minus}}, E789 should reconstruct some 30 events per run. In a restricted-acceptance experiment such as E789, the most plausible tagging technique is detection of single muons from semileptonic decay of the B. Since the B semileptonic branching ratios are {approx}10% and the E789 acceptance for muons from B decay is {approx}10%, fewer than 1 tagged event per run would be expected. We are thus looking for at least two orders of magnitude improvement in the produce luminosity {times} acceptance {times} tagging efficiency
Climate Extremes Promote Fatal Co-Infections during Canine Distemper Epidemics in African Lions
Extreme climatic conditions may alter historic host-pathogen relationships and synchronize the temporal and spatial convergence of multiple infectious agents, triggering epidemics with far greater mortality than those due to single pathogens. Here we present the first data to clearly illustrate how climate extremes can promote a complex interplay between epidemic and endemic pathogens that are normally tolerated in isolation, but with co-infection, result in catastrophic mortality. A 1994 canine distemper virus (CDV) epidemic in Serengeti lions (Panthera leo) coincided with the death of a third of the population, and a second high-mortality CDV epidemic struck the nearby Ngorongoro Crater lion population in 2001. The extent of adult mortalities was unusual for CDV and prompted an investigation into contributing factors. Serological analyses indicated that at least five “silent” CDV epidemics swept through the same two lion populations between 1976 and 2006 without clinical signs or measurable mortality, indicating that CDV was not necessarily fatal. Clinical and pathology findings suggested that hemoparsitism was a major contributing factor during fatal epidemics. Using quantitative real-time PCR, we measured the magnitude of hemoparasite infections in these populations over 22 years and demonstrated significantly higher levels of Babesia during the 1994 and 2001 epidemics. Babesia levels correlated with mortalities and extent of CDV exposure within prides. The common event preceding the two high mortality CDV outbreaks was extreme drought conditions with wide-spread herbivore die-offs, most notably of Cape buffalo (Syncerus caffer). As a consequence of high tick numbers after the resumption of rains and heavy tick infestations of starving buffalo, the lions were infected by unusually high numbers of Babesia, infections that were magnified by the immunosuppressive effects of coincident CDV, leading to unprecedented mortality. Such mass mortality events may become increasingly common if climate extremes disrupt historic stable relationships between co-existing pathogens and their susceptible hosts
In-Plane Deformation Mechanics for Highly Stretchable Electronics
Scissoring in thick bars suppresses buckling behavior in serpentine traces that have thicknesses greater than their widths, as detailed in a systematic set of analytical and experimental studies. Scissoring in thick copper traces enables elastic stretchability as large as approximate to 350%, corresponding to a sixfold improvement over previously reported values for thin geometries (approximate to 60%).</p
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Measurement of the xenon/deuterium inelastic cross section ratio using 490 GeV/c muons
Inelastic scattering of 490 GeV {mu}{sup +} from deuterium and xenon nuclei has been studied at energy transfers (v) up to 370 GeV and four-momentum transferred squared (Q{sup 2}) down to 0.1 GeV{sup 2}. A depletion in the inelastic {mu}{sup +} cross section has been observed from xenon compared to deuterium in the kinematic range 0.001 < x{sub Bj} < 0.08. The ratio of the xenon/deuterium cross section decreases with increasing v but does not depend on Q{sup 2}. The data extend the v and Q{sup 2} ranges studied previously in charged lepton and photoproduction experiments. The data agree qualitatively with models that invoke parton fusion in nuclei and models based on generalized vector dominance
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