69 research outputs found
Experimental feasibility of measuring the gravitational redshift of light using dispersion in optical fibers
This paper describes a new class of experiments that use dispersion in
optical fibers to convert the gravitational frequency shift of light into a
measurable phase shift or time delay. Two conceptual models are explored. In
the first model, long counter-propagating pulses are used in a vertical fiber
optic Sagnac interferometer. The second model uses optical solitons in
vertically separated fiber optic storage rings. We discuss the feasibility of
using such an instrument to make a high precision measurement of the
gravitational frequency shift of light.Comment: 11 pages, 12 figure
Violation of the Equivalence Principle in the light of the SNO and SK solar neutrino results
The SNO result on charged current deuteron disintegration, the
SuperKamiokande 1258-day data on electron scattering, and other solar neutrino
results are used to revisit the model of neutrino oscillations driven by a
violation of the equivalence principle. We use a chisq minimization technique
to examine oscillation between the nu(e) and another active neutrino, both
massless, and find that within the Standard Solar Model the fit to the SNO and
SuperKamiokande spectra are moderately good while a very good fit is obtained
when the absolute normalizations of the 8B and hep neutrino fluxes are allowed
to vary. The best fit prefers large, but not maximal, mixing, essentially no
hep neutrinos, and a 40% reduction in the 8B neutrino flux. The fit to the
total rates from the different experiments is not encouraging but when the
rates and spectra are considerd together the situation is much improved. We
remark on the expectations of the VEP model for the neutral current
measurements at SNO.Comment: Latex, 11 pages (incl. 1 postscript figure
Atmospheric Neutrino Oscillations and New Physics
We study the robustness of the determination of the neutrino masses and
mixing from the analysis of atmospheric and K2K data under the presence of
different forms of phenomenologically allowed new physics in the nu_mu--nu_tau
sector. We focus on vector and tensor-like new physics interactions which allow
us to treat, in a model independent way, effects due to the violation of the
equivalence principle, violations of the Lorentz invariance both CPT conserving
and CPT violating, non-universal couplings to a torsion field and non-standard
neutrino interactions with matter. We perform a global analysis of the full
atmospheric data from SKI together with long baseline K2K data in the presence
of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together
with sub-dominant effects due to these forms of new physics. We show that
within the present degree of experimental precision, the extracted values of
masses and mixing are robust under those effects and we derive the upper bounds
on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include
Can lepton flavor violating interactions explain the LSND results?
If the atmospheric and the solar neutrino problem are both explained by
neutrino oscillations, and if there are only three light neutrinos, then all
mass-squared differences between the neutrinos are known. In such a case,
existing terrestrial neutrino oscillation experiments cannot be significantly
affected by neutrino oscillations, but, in principle there could be an anomaly
in the neutrino flux due to new neutrino interactions. We discuss how a
non-standard muon decay would modify the
neutrino production processes of these experiments. Since violation
is small for New Physics above the weak scale one can use related
flavor-violating charged lepton processes to constrain these decays in a model
independent way. We show that the upper bounds on ,
muonium-antimuonium conversion and rule out any observable
effect for the present experiments due to
for , respectively. Applying similar arguments to
flavor-changing semi-leptonic reactions we exclude the possibility that the
"oscillation signals" observed at LSND are due to flavor-changing interactions
that conserve total lepton number.Comment: 21 pages, 6 figures, Latex; minor correction
Reexamining nonstandard interaction effects on supernova neutrino flavor oscillations
Several extensions of the standard electroweak model allow new four-fermion
interactions (nu_a nu_b * ff) with strength eps_ab*G_F, where (a,b) are flavor
indices. We revisit their effects on flavor oscillations of massive
(anti)neutrinos in supernovae, in order to achieve, in the region above the
protoneutron star, an analytical treatment valid for generic values of the
neutrino mixing angles (omega,phi,psi)=(theta_12,theta_13,theta_23). Assuming
that eps_ab<<1, we find that the leading effects on the flavor transitions
occurring at high (H) and low (L) density along the supernova matter profile
can be simply embedded through the replacements phi-->phi+eps_H and
omega-->omega+eps_L, respectively, where eps_H and eps_L are specific linear
combinations of the eps_ab's. Similar replacements hold for eventual
oscillations in the Earth matter. From a phenomenological point of view, the
most relevant consequence is a possible uncontrolled bias (phi-->phi+eps_H) in
the value of the mixing angle phi inferred by inversion of supernova neutrino
data. Such a drawback, however, does not preclude the discrimination of the
neutrino mass spectrum hierarchy (direct or inverse) through supernova neutrino
oscillations.Comment: Text clarified, one figure added. To appear in PR
Measurement of the forward-backward asymmetry in Î0b and ÎÂŻ0b baryon production in ppÂŻ collisions at sâ=1.96 TeV
We measure the forward-backward asymmetry in the production of Î0b and ÎÂŻ0b baryons as a function of rapidity in ppÂŻ collisions at sâ=1.96ââTeV using 10.4ââfbâ1 of data collected with the D0 detector at the Fermilab Tevatron collider. The asymmetry is determined by the preference of Î0b or ÎÂŻ0b particles to be produced in the direction of the beam protons or antiprotons, respectively. The measured asymmetry integrated over rapidity y in the range 0.1<|y|<2.0 is A=0.04±0.07(stat)±0.02(syst)
Tracking development assistance for health and for COVID-19 : a review of development assistance, government, out-of-pocket, and other private spending on health for 204 countries and territories, 1990-2050
Background The rapid spread of COVID-19 renewed the focus on how health systems across the globe are financed, especially during public health emergencies. Development assistance is an important source of health financing in many low-income countries, yet little is known about how much of this funding was disbursed for COVID-19. We aimed to put development assistance for health for COVID-19 in the context of broader trends in global health financing, and to estimate total health spending from 1995 to 2050 and development assistance for COVID-19 in 2020. Methods We estimated domestic health spending and development assistance for health to generate total health-sector spending estimates for 204 countries and territories. We leveraged data from the WHO Global Health Expenditure Database to produce estimates of domestic health spending. To generate estimates for development assistance for health, we relied on project-level disbursement data from the major international development agencies' online databases and annual financial statements and reports for information on income sources. To adjust our estimates for 2020 to include disbursements related to COVID-19, we extracted project data on commitments and disbursements from a broader set of databases (because not all of the data sources used to estimate the historical series extend to 2020), including the UN Office of Humanitarian Assistance Financial Tracking Service and the International Aid Transparency Initiative. We reported all the historic and future spending estimates in inflation-adjusted 2020 US per capita, purchasing-power parity-adjusted US8. 8 trillion (95% uncertainty interval [UI] 8.7-8.8) or 40.4 billion (0.5%, 95% UI 0.5-0.5) was development assistance for health provided to low-income and middle-income countries, which made up 24.6% (UI 24.0-25.1) of total spending in low-income countries. We estimate that 13.7 billion was targeted toward the COVID-19 health response. 1.4 billion was repurposed from existing health projects. 2.4 billion (17.9%) was for supply chain and logistics. Only 1519 (1448-1591) per person in 2050, although spending across countries is expected to remain varied. Interpretation Global health spending is expected to continue to grow, but remain unequally distributed between countries. We estimate that development organisations substantially increased the amount of development assistance for health provided in 2020. Continued efforts are needed to raise sufficient resources to mitigate the pandemic for the most vulnerable, and to help curtail the pandemic for all. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.Peer reviewe
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt [ s ] = 13TeV
A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fbâ1 of protonâproton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at âs = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions
Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at sqrt (s) = 13 TeV with the ATLAS detector
A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fbâ1 of pp collisions at View the MathML sources=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter
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