66 research outputs found
Angular Conditions,Relations between Breit and Light-Front Frames, and Subleading Power Corrections
We analyze the current matrix elements in the general collinear (Breit)
frames and find the relation between the ordinary (or canonical) helicity
amplitudes and the light-front helicity amplitudes. Using the conservation of
angular momentum, we derive a general angular condition which should be
satisfied by the light-front helicity amplitudes for any spin system. In
addition, we obtain the light-front parity and time-reversal relations for the
light-front helicity amplitudes. Applying these relations to the spin-1 form
factor analysis, we note that the general angular condition relating the five
helicity amplitudes is reduced to the usual angular condition relating the four
helicity amplitudes due to the light-front time-reversal condition. We make
some comments on the consequences of the angular condition for the analysis of
the high- deuteron electromagnetic form factors, and we further apply the
general angular condition to the electromagnetic transition between spin-1/2
and spin-3/2 systems and find a relation useful for the analysis of the
N- transition form factors. We also discuss the scaling law and the
subleading power corrections in the Breit and light-front frames.Comment: 24 pages,2 figure
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Measurement of the Bs Lifetime in Fully and Partially Reconstructed Bs -> Ds- (phi pi-)X Decays in pbar-p Collisions at sqrt(s) = 1.96 TeV
We present a measurement of the Bs lifetime in fully and partially
reconstructed Bs -> Ds(phi pi)X decays in 1.3 fb-1 of pbar-p collisions at
sqrt(s) = 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron.
We measure tau(Bs) = 1.518 +/- 0.041 (stat.) +/- 0.027 (syst.) ps. The ratio of
this result and the world average B0 lifetime yields tau(Bs)/tau(B0) = 0.99
+/-0.03, which is in agreement with recent theoretical predictions.Comment: submitted to Phys. Rev. Let
W boson polarization measurement in the ttbar dilepton channel using the CDF II Detector
We present a measurement of boson polarization in top-quark decays in
events with decays to dilepton final states using of integrated luminosity in collisions collected by the
CDF II detector at the Tevatron. A simultaneous measurement of the fractions of
longitudinal () and right-handed () bosons yields the results
and . Combining this measurement
with our previous result based on single lepton final states, we obtain and . The results are consistent with standard
model expectation.Comment: Published in Phys. Lett.
Observation of the structure in the Mass Spectrum in cays
The observation of the structure in decays produced in collisions at \sqrt{s}=1.96~\TeV is
reported with a statistical significance greater than 5 standard deviations. A
fit to the mass spectrum is performed assuming the presence of a
Breit-Wigner resonance. The fit yields a signal of resonance
events, and resonance mass and width of
4143.4^{+2.9}_{-3.0}(\mathrm{stat})\pm0.6(\mathrm{syst})~\MeVcc and
15.3^{+10.4}_{-6.1}(\mathrm{stat})\pm2.5(\mathrm{syst})~\MeVcc respectively.
The parameters of this resonance-like structure are consistent with values
reported from an earlier CDF analysis.Comment: 7 pages, 2 figures, submited to Phys. Rev. Let
IDH mutant diffuse and anaplastic astrocytomas have similar age at presentation and little difference in survival: a grading problem for WHO
The WHO 2007 classification of tumors of the CNS distinguishes between diffuse astrocytoma WHO grade II (A IIWHO2007) and anaplastic astrocytoma WHO grade III (AA III WHO2007). Patients with A II WHO2007 are significantly younger and survive significantly longer than those with AA III WHO2007. So far, classification and grading relies on morphological grounds only and does not yet take into account IDH status, a molecular marker of prognostic relevance. We here demonstrate that WHO 2007 grading performs poorly in predicting prognosis when applied to astrocytoma carrying IDH mutations. Three independent series including a total of 1360 adult diffuse astrocytic gliomas with IDH mutation containing 683 A II IDHmut, 562 AA III IDHmut and 115 GBM IDHmut have been examined for age distribution and survival. In all three series patients with A II IDHmut and AA III IDHmut were of identical age at presentation of disease (36-37 years) and the difference in survival between grades was much less (10.9 years for A II IDHmut, 9.3 years for AA III IDHmut) than that reported for A II WHO2007 versus AA III WHO2007. Our analyses imply that the differences in age and survival between A II WHO2007 and AA III WHO2007 predominantly depend on the fraction of IDH-non-mutant astrocytomas in the cohort. This data poses a substantial challenge for the current practice of astrocytoma grading and risk stratification and is likely to have far-reaching consequences on the management of patients with IDH-mutant astrocytoma
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