1,450 research outputs found
Effective Hamiltonian Approach to Hyperon Beta Decay with Final-State Baryon Polarization
Using an effective Hamiltonian approach, we obtain expressions for hyperon
beta decay final-state baryon polarization. Terms through second order in the
energy release are retained. The resulting approximate expressions are much
simpler and more compact than the exact expressions, and they agree closely
with them.Comment: 1 Figure Will appear in Phys Rev D 60 Article 117505 (Dec 1, 1999
Time-Lapse Acoustic Imaging of Mesoscale and Fine-Scale Variability within the Faroe-Shetland Channel
We describe and analyze the results of a threeâdimensional seismic (i.e. acoustic) reflection survey from the FaroeâShetland Channel that is calibrated with nearâcoincident hydrographic and satellite observations. 54 vertical seismic transects were acquired over a period of 25 days. On each transect, a 250ââ400 m band of reflections is observed within the water column. Hydrographic measurements demonstrate that this reflective band is caused by temperature variations within the pycnocline that separates warm, nearâsurface waters of Atlantic origin from cold, deep waters which flow southward from the Nordic Seas. Tilting of reflective surfaces records geostrophic shear between these nearâsurface and deep waters. Measurements of temporal changes of pycnoclinic depth and of reflection tilt are used to infer the existence of an anticyclonic vortex that advects northeastward. Comparison with satellite measurements of seaâsurface temperature and height suggests that this vortex is caused by meandering of the Continental Slope Current. A model of a Gaussian vortex is used to match seismic and satellite observations. This putative vortex has a core radius of 20â30 km and a maximum azimuthal velocity of 0.3ââ0.4 m sâ1. It translates at 0.01ââ0.1 m sâ1. Within the pycnocline, diapycnal diffusivity, K , is estimaed by analyzing the turbulent spectral subrange of tracked reflections. K varies between 10â5.7 and 10â5.0 m 2 sâ1 in a pattern that is broadly consistent with translation of the vortex. Our integrated study demonstrates the ability of timeâlapse seismic reflection surveying to dynamically resolve the effects that mesoscale activity has upon deep thermohaline structure on scales from meters to hundreds of kilometers.Natural Environment Research Council (NERC)
Engineering and Physical Science Research Council
794 Program Grant EP/K034529/
Cancer, COVID-19, and the need for critique [version 2; peer review: 2 approved]
In this open letter we examine the implications of the coronavirus disease 2019 (COVID-19) pandemic for cancer research and care from the point of view of the social studies of science, technology, and medicine. We discuss how the pandemic has disrupted several aspects of cancer care, underscoring the fragmentation of institutional arrangements, the malleable priorities in cancer research, and the changing promises of therapeutic innovation. We argue for the critical relevance of qualitative social sciences in cancer research during the pandemic despite the difficulties of immersive kinds of fieldwork. Social science research can help understand the ongoing, situated and lived impact of the pandemic, as well as fully underline its socially stratified consequences. We outline the risk that limiting and prioritising research activities according to their immediate clinical outcomes might have in the relational and longitudinal understanding of cancer practices in the UK. Finally, we alert against potential distortions that a âcovidizationâ of cancer research might entail, arguing for the need to maintain a critical point of view on the pandemic
Soft capacitor fibers using conductive polymers for electronic textiles
A novel, highly flexible, conductive polymer-based fiber with high electric
capacitance is reported. In its crossection the fiber features a periodic
sequence of hundreds of conductive and isolating plastic layers positioned
around metallic electrodes. The fiber is fabricated using fiber drawing method,
where a multi-material macroscopic preform is drawn into a sub-millimeter
capacitor fiber in a single fabrication step. Several kilometres of fibers can
be obtained from a single preform with fiber diameters ranging between 500um
-1000um. A typical measured capacitance of our fibers is 60-100 nF/m and it is
independent of the fiber diameter. For comparison, a coaxial cable of the
comparable dimensions would have only ~0.06nF/m capacitance. Analysis of the
fiber frequency response shows that in its simplest interrogation mode the
capacitor fiber has a transverse resistance of 5 kOhm/L, which is inversely
proportional to the fiber length L and is independent of the fiber diameter.
Softness of the fiber materials, absence of liquid electrolyte in the fiber
structure, ease of scalability to large production volumes, and high
capacitance of our fibers make them interesting for various smart textile
applications ranging from distributed sensing to energy storage
Improved KL->pi e nu Form Factor and Phase Space Integral with Reduced Model Uncertainty
Using the published KTeV sample of 2 million KL-> pi e nu decays and a new
form factor expansion with a rigorous bound on higher order terms, we present a
new determination of the KL->pi e nu form factor and phase space integral.
Compared to the previous KTeV result, the uncertainty in the new form factor
expansion is negligible and results in an overall uncertainty in the phase
space integral (IKe) that is a factor of two smaller: IKe = 0.15392 +- 0.00048
\.Comment: 3 pages, 2 figures, submitted to PRD Rapid Communicatio
Measurements of the Decay
The E799-II (KTeV) experiment at Fermilab has collected 83262 events above a background of 79 events. We measure a decay width,
normalized to the (\pi^0 \to \gamma\gamma, \pi^0 to
\gamma\gamma, \pi^0_D \to e^+e^-\gamma) decay width, of K_L \to
e^+e^-\gamma. We also measure parameters of two form factor models. In the Bergstrom, Masso, and Singer
(BMS) parametrization, we find \caks = -0.517 \pm 0.030_{stat} \pm
0.022_{syst}. We separately fit for the first parameter of the D'Ambrosio,
Isidori, and Portoles (DIP) model and find \adip = -1.729 \pm 0.043_{stat} \pm
0.028_{syst}.Comment: 5 pages, 3 figures, submitted to PR
A Measurement of the K0 Charge Radius and a CP Violating Asymmetry Together with a Search for CP Violating E1 Direct Photon Emission in the Rare Decay KL->pi+pi-e+e-
Using the complete KTeV data set of 5241 candidate KL->pi+pi-e+e- decays
(including an estimated background of 204+-14 events), we have measured the
coupling gCR=0.163+- 0.014(stat)+-0.023(syst) of the CP conserving charge
radius process and from it determined a K0 charge radius of
(K0)=(-0.077+-0.007(stat)+-0.011(syst)) fm**2. We have also determined a
first experimental upper limit of 0.04 (90% CL) for the ratio |g_{E1}|/|g_{M1}|
of the coupling for the E1 direct photon emission process relative to the
coupling for M1 direct photon emission process. We also report the measurement
of its associated vector form factor |gM1`|(1+
(a_1/a_2)/(M(rho)**2-M(K)**2)+2M(K)E(gamma*)) where |gM1`|=(1.11+-
0.12(stat)+-0.08(syst) and a_1/a_2 = (-0.744+-0.027(stat)0.032(syst))
GeV**2/c**2. In addition, a measurement of the manifestly CP violating
asymmetry of magnitude (13.6+- 1.4+-(stat)+-1.5(syst))% in the CP and T odd
angle phi between the decay planes of the e+e- and pi+pi- pairs in the KL
center of mass system is reported
Search for the Rare Decay K_{L}\to\pi^{0}\pi^{0}\gamma
The KTeV E799 experiment has conducted a search for the rare decay
via the topology
(where ). Due to Bose
statistics of the pair and the real nature of the photon, the
decay is restricted to proceed at lowest order
by the CP conserving direct emission (DE) of an E2 electric quadrupole photon.
The rate of this decay is interesting theoretically since chiral perturbation
theory predicts that this process vanishes at level . Therefore, this
mode probes chiral perturbation theory at . In this paper we report a
determination of an upper limit of (90% CL) for
. This is approximately a factor of 20 lower than
previous results.Comment: six pages and six figures in the submission. Reformatted for Physics
Review
Search for the Rare Decays KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-
The KTeV E799 experiment has conducted a search for the rare decays
KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-, where the X0 is a possible new
neutral boson that was reported by the HyperCP experiment with a mass of (214.3
pm 0.5) MeV/c^{2}. We find no evidence for either decay. We obtain upper limits
of Br(KL->pi0pi0X0->pi0pi0mu+mu-) pi0pi0mu+mu-) <
9.2 x 10^{-11} at the 90% confidence level. This result rules out the
pseudoscalar X0 as an explanation of the HyperCP result under the scenario that
the \bar{d}sX0 coupling is completely real
Measurement of the rare decay pi0 -> e+ e-
The branching ratio of the rare decay pi0 -> e+ e- has been measured
precisely, using the complete data set from the KTeV E799-II experiment at
Fermilab. We observe 794 candidate pi0 -> e+ e- events using K0_L -> 3pi0 as a
source of tagged pi0's. The expected background is 52.7 +- 11.2 events,
predominantly from high e+ e- mass pi0 -> e+ e- gamma decays. We have measured
B[(pi0 -> e+ e-), (m_e+e-/m_pi0)^2 > 0.95] = 6.44 +- 0.25(stat) +- 0.22(syst)
x10^(-8), which is above the unitary bound from pi0 -> gamma gamma and within
the range of theoretical expectations from the standard model.Comment: 6 pages, 4 figure
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