846 research outputs found
Measurement of the fraction of t-tbar production via gluon-gluon fusion in p-pbar collisions at sqrt(s)=1.96 TeV
We present a measurement of the ratio of t-tbar production cross section via
gluon-gluon fusion to the total t-tbar production cross section in p-pbar
collisions at sqrt{s}=1.96 TeV at the Tevatron. Using a data sample with an
integrated luminosity of 955/pb recorded by the CDF II detector at Fermilab, we
select events based on the t-tbar decay to lepton+jets. Using an artificial
neural network technique we discriminate between t-tbar events produced via
q-qbar annihilation and gluon-gluon fusion, and find
Cf=(gg->ttbar)/(pp->ttbar)<0.33 at the 68% confidence level. This result is
combined with a previous measurement to obtain the most precise measurement of
this quantity, Cf=0.07+0.15-0.07.Comment: submitted to Phys. Rev.
Search for lepton flavor violating decays of a heavy neutral particle in p-pbar collisions at root(s)=1.8 TeV
We report on a search for a high mass, narrow width particle that decays
directly to e+mu, e+tau, or mu+tau. We use approximately 110 pb^-1 of data
collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence
of lepton flavor violating decays is found. Limits are set on the production
and decay of sneutrinos with R-parity violating interactions.Comment: Figure 2 fixed. Reference 4 fixed. Minor changes to tex
Measurement of Resonance Parameters of Orbitally Excited Narrow B^0 Mesons
We report a measurement of resonance parameters of the orbitally excited
(L=1) narrow B^0 mesons in decays to B^{(*)+}\pi^- using 1.7/fb of data
collected by the CDF II detector at the Fermilab Tevatron. The mass and width
of the B^{*0}_2 state are measured to be m(B^{*0}_2) =
5740.2^{+1.7}_{-1.8}(stat.) ^{+0.9}_{-0.8}(syst.) MeV/c^2 and \Gamma(B^{*0}_2)
= 22.7^{+3.8}_{-3.2}(stat.) ^{+3.2}_{-10.2}(syst.) MeV/c^2. The mass difference
between the B^{*0}_2 and B^0_1 states is measured to be
14.9^{+2.2}_{-2.5}(stat.) ^{+1.2}_{-1.4}(syst.) MeV/c^2, resulting in a B^0_1
mass of 5725.3^{+1.6}_{-2.2}(stat.) ^{+1.4}_{-1.5}(syst.) MeV/c^2. This is
currently the most precise measurement of the masses of these states and the
first measurement of the B^{*0}_2 width.Comment: 7 pages, 1 figure, 1 table. Submitted to Phys.Rev.Let
Failing boys and moral panics: perspectives on the underachievement debate
The paper re-examines the underachievement debate from the perspective of the ‘discourse of derision’ that surrounds much writing in this area. It considers the contradictions and inconsistencies which underpin much of the discourse – from a reinterpretation of examination scores, to the conflation of the concepts of ‘under’ and ‘low’ achievement and finally to the lack of consensus on a means of defining and measuring the term underachievement. In doing so, this paper suggests a more innovative approach for understanding, re-evaluating and perhaps rejecting the notion of underachievement
Moving research into practice: lessons from the US Agency for Healthcare Research and Quality's IDSRN program
BACKGROUND: The U.S. Agency for Healthcare Research and Quality's (AHRQ) Integrated Delivery Systems Research Network (IDSRN) program was established to foster public-private collaboration between health services researchers and health care delivery systems. Its broad goal was to link researchers and delivery systems to encourage implementation of research into practice. We evaluated the program to address two primary questions: 1) How successful was IDSRN in generating research findings that could be applied in practice? and 2) What factors facilitate or impede such success? METHODS: We conducted in-person and telephone interviews with AHRQ staff and nine IDSRN partner organizations and their collaborators, reviewed program documents, analyzed projects funded through the program, and developed case studies of four IDSRN projects judged promising in supporting research implementation. RESULTS: Participants reported that the IDSRN structure was valuable in creating closer ties between researchers and participating health systems. Of the 50 completed projects studied, 30 had an operational effect or use. Some kinds of projects were more successful than others in influencing operations. If certain conditions were met, a variety of partnership models successfully supported implementation. An internal champion was necessary for partnerships involving researchers based outside the delivery system. Case studies identified several factors important to success: responsiveness of project work to delivery system needs, ongoing funding to support multiple project phases, and development of applied products or tools that helped users see their operational relevance. Factors limiting success included limited project funding, competing demands on potential research users, and failure to reach the appropriate audience. CONCLUSION: Forging stronger partnerships between researchers and delivery systems has the potential to make research more relevant to users, but these benefits require clear goals and appropriate targeting of resources. Trade-offs are inevitable. The health services research community can best consider such trade-offs and set priorities if there is more dialogue to identify areas and approaches where such partnerships may have the most promise. Though it has unique features, the IDSRN experience is relevant to research implementation in diverse settings
Interactive Learning-Based Realizability for Heyting Arithmetic with EM1
We apply to the semantics of Arithmetic the idea of ``finite approximation''
used to provide computational interpretations of Herbrand's Theorem, and we
interpret classical proofs as constructive proofs (with constructive rules for
) over a suitable structure \StructureN for the language of
natural numbers and maps of G\"odel's system \SystemT. We introduce a new
Realizability semantics we call ``Interactive learning-based Realizability'',
for Heyting Arithmetic plus \EM_1 (Excluded middle axiom restricted to
formulas). Individuals of \StructureN evolve with time, and
realizers may ``interact'' with them, by influencing their evolution. We build
our semantics over Avigad's fixed point result, but the same semantics may be
defined over different constructive interpretations of classical arithmetic
(Berardi and de' Liguoro use continuations). Our notion of realizability
extends intuitionistic realizability and differs from it only in the atomic
case: we interpret atomic realizers as ``learning agents''
Cost-effectiveness of Implementing Low-Tidal Volume Ventilation in Patients With Acute Lung Injury
Background: Despite widespread guidelines recommending the use of lung-protective ventilation (LPV) in patients with acute lung injury (ALI), many patients do not receive this lifesaving therapy. We sought to estimate the incremental clinical and economic outcomes associated with LPV and determined the maximum cost of a hypothetical intervention to improve adherence with LPV that remained cost-effective.
Methods: Adopting a societal perspective, we developed a theoretical decision model to determine the cost-effectiveness of LPV compared to non-LPV care. Model inputs were derived from the literature and a large population-based cohort of patients with ALI. Cost-effectiveness was determined as the cost per life saved and the cost per quality-adjusted life-years (QALYs) gained.
Results: Application of LPV resulted in an increase in QALYs gained by 15% (4.21 years for non-LPV vs 4.83 years for LPV), and an increase in lifetime costs of 99,588 for non-LPV vs 22,566 per life saved at hospital discharge and 9,482. Results were robust to a wide range of economic and patient parameter assumptions.
Conclusions: Even a costly intervention to improve adherence with low-tidal volume ventilation in patients with ALI reduces death and is cost-effective by current societal standards.NIH F32HL090220.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84154/1/Cooke - CEA LPV.pd
Top Quark Mass Measurement in the Lepton plus Jets Channel Using a Modified Matrix Element Method
46 pages, 16 figures. Edited in response to referee comments and resubmitted to Phys. Rev. DWe report a measurement of the top quark mass, m_t, obtained from ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9 fb^-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, with effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of m_t and a parameter JES that determines /in situ/ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find m_t = 172.7 +/- 1.8 (stat. + JES) +/- 1.2 (syst.) GeV/c^2.We report a measurement of the top quark mass, mt, obtained from pp̅ collisions at √s=1.96  TeV at the Fermilab Tevatron using the CDF II detector. We analyze a sample corresponding to an integrated luminosity of 1.9  fb-1. We select events with an electron or muon, large missing transverse energy, and exactly four high-energy jets in the central region of the detector, at least one of which is tagged as coming from a b quark. We calculate a signal likelihood using a matrix element integration method, where the matrix element is modified by using effective propagators to take into account assumptions on event kinematics. Our event likelihood is a function of mt and a parameter JES (jet energy scale) that determines in situ the calibration of the jet energies. We use a neural network discriminant to distinguish signal from background events. We also apply a cut on the peak value of each event likelihood curve to reduce the contribution of background and badly reconstructed events. Using the 318 events that pass all selection criteria, we find mt=172.7±1.8(stat+JES)±1.2(syst)  GeV/c2.Peer reviewe
Search for Long-Lived Massive Charged Particles in 1.96 TeV \bar{p}p} Collisions
16 pages, 2 figures; Revision to fix PDF errors on some displays/printersWe performed a signature-based search for long-lived charged massive particles (CHAMPs) produced in 1.0 of collisions at TeV, collected with the CDF II detector using a high transverse-momentum () muon trigger. The search used time-of-flight to isolate slowly moving, high- particles. One event passed our selection cuts with an expected background of events. We set an upper bound on the production cross section, and, interpreting this result within the context of a stable scalar top quark model, set a lower limit on the particle mass of 249 GeV/ at 95% C.L.We performed a signature-based search for long-lived charged massive particles produced in 1.0  fb-1 of pp̅ collisions at √s=1.96  TeV, collected with the CDF II detector using a high transverse-momentum (pT) muon trigger. The search used time of flight to isolate slowly moving, high-pT particles. One event passed our selection cuts with an expected background of 1.9±0.2 events. We set an upper bound on the production cross section and, interpreting this result within the context of a stable scalar top-quark model, set a lower limit on the particle mass of 249  GeV/c2 at 95% C.L.Peer reviewe
Search for a Higgs Boson Decaying to Two W Bosons at CDF
We present a search for a Higgs boson decaying to two W bosons in ppbar collisions at sqrt(s)=1.96 TeV center-of-mass energy. The data sample corresponds to an integrated luminosity of 3.0 fb-1 collected with the CDF II detector. We find no evidence for production of a Higgs boson with mass between 110 and 200 GeV/c^2, and determine upper limits on the production cross section. For the mass of 160 GeV/c^2, where the analysis is most sensitive, the observed (expected) limit is 0.7 pb (0.9 pb) at 95% Bayesian credibility level which is 1.7 (2.2) times the standard model cross section
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