2,667 research outputs found
Top differential cross section measurements (Tevatron)
Differential cross sections in the top quark sector measured at the Fermilab
Tevatron collider are presented. CDF used 2.7 fb of data and measured
the differential cross section as a function of the invariant mass of the
system. The measurement shows good agreement with the standard model
and furthermore is used to derive limits on the ratio for
gravitons which decay to top quarks in the Randall-Sundrum model. D0 used 1.0
fb$^{-1} of data to measure the differential cross section as a function of the
transverse momentum of the top quark. The measurement shows a good agreement to
the higher order perturbative QCD prediction and various predictions based on
various Monte-Carlo generators.Comment: To appear in the Proceedings of TOP2011, 4th International Workshop
on Top Quark Physics, Spai
D* production in deep-inelastic Scattering at low Q2
Inclusive production of D* mesons in deep-inelastic scattering at HERA is
studied in the range 5 < Q^2 < 100 GeV2 of the photon virtuality and 0.02 < y <
0.70 of the inelasticity of the scattering process. The visible range for the
D* meson is p_T (D*) > 1.25 GeV and |\eta(D*)| < 1.8. The data were taken with
the H1 detector in the years 2004 to 2007 and correspond to an integrated
luminosity of 347 pb^{-1}. Single and double differential cross sections are
measured. The results are compared to QCD predictions.Comment: XIX International Workshop on Deep-Inelastic Scattering and Related
Subjects (DIS 2011, April 11-15, Newport News, USA
Measurement of the Properties of the top Quark at D{\O}
Different measurements of the properties of the top quark using up to collected with the D{\O} detector at the Fermilab Tevatron collider
are presented. The top mass is obtained from a study of dilepton and
lepton+jets final states, while the width is obtained from a combination of the
measurements of the single top production via t-channel exchange and the
determination of the t \rightarrow Wb branching ratio. Furthermore the
measurement of the helicity of the W boson from top quark decays, a measurement
of spin correlations and a measurement of the jet pull (color flow)
in events are presented.Comment: XIX International Workshop on Deep-Inelastic Scattering and Related
Subjects (DIS 2011, April 11-15, Newport News, USA
Properties of the top quark
ABSTRACT Recent measurements of top-quark properties at the LHC and the Tevatron are presented. Most recent measurements of the top quark mass have been carried out by CMS using 19.7/fb of √ s = 8 TeV data including the study of the dependence on event kinematics. ATLAS uses the full Run I data at √ s = 7 TeV for a "3D" measurement that significantly reduces systematic uncertainties. D0 employs the full Run II data using the matrix element method to measure the top quark mass with significantly reduced systematic uncertainties. Many different measurements of the top quark exist to date and the most precise ones per decay channel per experiment have been combined into the first world combination with a relative precision of 0.44%. Latest updates of measurements of production asymmetries include the measurement of the tt production asymmetry by D0 employing the full Run II data set, by CMS and ATLAS (including the polarization of the top quark) employing both the full data set at √ s = 7 TeV. CMS uses the full √ s = 8 TeV data to measure the top quark polarization in single top production, the ratio R of the branching fractions B(t → W b)/B(t → W q) and to search for flavor changing neutral currents. The results from all these measurements agree well with their respective Standard Model expectation
Long-term Running Experience with the Silicon Micro-strip Tracker at the D{\O} detector
The SiliconMicro-strip Tracker (SMT) at the D{\O} experiment in the Fermilab
Tevatron collider has been operating since 2001. In 2006, an additional layer,
referred to as 'Layer 0', was installed to improve impact parameter resolution
and compensate for detector degradation due to radiation damage to the original
innermost SMT layer. The SMT detector provides valuable tracking and vertexing
information for the experiment. This contribution will highlight aspects of the
long term operation of the SMT, including the impact of the silicon readout
test-stand. Due to the full integration of the test-stand into the D{\O}
trigger framework, this test-stand provides an advantageous tool for training
of new experts and studying subtle effects in the SMT while minimizing impact
on the global data acquisition.Comment: Proceedings of TIPP 2011 (Technology and Instrumentation for Particle
Physics 2011), June 9-14 2011, Chicago, US
Systematic Heterogeneity of Fractional Vesicle Pool Sizes and Release Rates of Hippocampal Synapses
AbstractHippocampal neurons in tissue culture develop functional synapses that exhibit considerable variation in synaptic vesicle content (20–350 vesicles). We examined absolute and fractional parameters of synaptic vesicle exocytosis of individual synapses. Their correlation to vesicle content was determined by activity-dependent discharge of FM-styryl dyes. At high frequency stimulation (30 Hz), synapses with large recycling pools released higher amounts of dye, but showed a lower fractional release compared to synapses that contained fewer vesicles. This effect gradually vanished at lower frequencies when stimulation was triggered at 20 Hz and 10 Hz, respectively. Live-cell antibody staining with anti-synaptotagmin-1-cypHer 5, and overexpression of synaptopHluorin as well as photoconversion of FM 1-43 followed by electron microscopy, consolidated the findings obtained with FM-styryl dyes. We found that the readily releasable pool grew with a power function with a coefficient of 2/3, possibly indicating a synaptic volume/surface dependency. This observation could be explained by assigning the rate-limiting factor for vesicle exocytosis at high frequency stimulation to the available active zone surface that is proportionally smaller in synapses with larger volumes
Ferrofluids as thermal ratchets
Colloidal suspensions of ferromagnetic nano-particles, so-called ferrofluids,
are shown to be suitable systems to demonstrate and investigate thermal ratchet
behavior: By rectifying thermal fluctuations, angular momentum is transferred
to a resting ferrofluid from an oscillating magnetic field without net rotating
component. Via viscous coupling the noise driven rotation of the microscopic
ferromagnetic grains is transmitted to the carrier liquid to yield a
macroscopic torque. For a simple setup we analyze the rotation of the
ferrofluid theoretically and show that the results are compatible with the
outcome of a simple demonstration experiment.Comment: 4 pages, 3 figures, corrected version, improved figures, to be
published in Phys. Rev. Let
Prevalence and influence on outcome of HER2/neu, HER3 and NRG1 expression in patients with metastatic colorectal cancer
Our aim was to explore the impact of the HER2/neu, HER3 receptor as well as their ligands' neuregulin (NRG1) expression on the outcome of patients with metastatic colorectal cancer (mCRC). NRG1, HER2/neu and HER3 expression was evaluated in 208 patients with mCRC receiving 5-FU/LV plus irinotecan or irinotecan plus oxaliplatin as the first-line treatment. Biomarker expression was correlated with the outcome of patients. NRG1 (low: 192 vs. high: 16), HER2/neu (low: 201 vs. high: 7) and HER3 (low: 69 vs. high: 139) expressions were assessed in 208 patients. High versus low NRG1 expression significantly affected progression-free survival (PFS) 4.7 vs. 8.2 months, hazard ratio (HR): 2.45; 95{\%} confidence interval (CI): 1.45-4.13; P=0.001, but not overall survival (OS) (15.5 vs. 20.7 months, HR: 1.33; 95{\%} CI: 0.76-2.35; P=0.32). High versus low HER3 expression (PFS: 7.1 vs. 8.8 months, HR: 1.11; 95{\%} CI: 0.82-1.50; P=0.50; OS: 19.8 vs. 21.1 months, HR: 0.95; 95{\%} CI: 0.70-1.30; P=0.75) and high compared with low HER2/neu expression (PFS: 7.7 vs. 8.0 months, HR: 1.07; 95{\%} CI: 0.71-1.60; P=0.75; OS: 16.6 vs. 21.1 months, HR: 1.13; 95{\%} CI: 0.75-1.71; P=0.57) did not influence outcome. High NRG1 expression was associated with inferior PFS in the FIRE-1 trial. We did not detect a prognostic impact of HER2/neu and HER3 overexpression in mCRC. The frequency of overexpression was comparable with other studies
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