607 research outputs found
Z-boson as "the standard candle" for high precision W-boson physics at LHC
In this paper we propose a strategy for measuring the inclusive W-boson
production processes at LHC. This strategy exploits simultaneously the unique
flexibility of the LHC collider in running variable beam particle species at
variable beam energies, and the configuration flexibility of the LHC detectors.
We propose their concrete settings for a precision measurement of the Standard
Model parameters. These dedicated settings optimise the use of the Z boson and
Drell-Yan pair production processes as ``the standard reference candles''. The
presented strategy allows to factorise and to directly measure those of the QCD
effects which affect differently the W and Z production processes. It reduces
to a level of 10^{-4} the impact of uncertainties in the partonic distribution
functions (PDFs) and in the transverse momentum of the quarks on the
measurement precision. Last but not the least, it reduces by a factor of 10 an
impact of systematic measurement errors, such as the energy scale and the
measurement resolution, on the W-boson production observables.Comment: 20 pages, 4 figure
The correction of the littlest Higgs model to the Higgs production process in collisions
The littlest Higgs model is the most economical one among various little
Higgs models. In the context of the littlest Higgs(LH) model, we study the
process and calculate the contributions of the
LH model to the cross section of this process. The results show that, in most
of parameter spaces preferred by the electroweak precision data, the value of
the relative correction is larger than 10%. Such correction to the process
is large enough to be detected via
collisions in the future high energy linear collider()
experiment with the c.m energy =500 GeV and a yearly integrated
luminosity , which will give an ideal way to test the
model.Comment: 13 pages, 4 figure
Measurement of MW+ - MW- at LHC
This paper is the second of the series of papers proposing dedicated
strategies for precision measurements of the Standard Model parameters at the
LHC. The common feature of these strategies is their robustness with respect to
the systematic measurement and modeling error sources. Their impact on the
precision of the measured parameters is reduced using dedicated observables and
dedicated measurement procedures which exploit flexibilities of the collider
and detector running modes. In the present paper we focus our attention on the
measurement of the charge asymmetry of the W-boson mass. This measurement is of
primordial importance for the LHC experimental program, both as a direct test
of the charge-sign-independent coupling of the W-bosons to the matter particles
and as a necessary first step towards the precision measurement of the
charge-averaged W-boson mass. We propose and evaluate the LHC-specific strategy
to measure the mass difference between the positively and negatively charged
W-bosons, MW+ - MW-. We show that its present precision can be improved at the
LHC by a factor of 20. We argue that such a precision is beyond the reach of
the standard measurement and calibration methods imported to the LHC from the
Tevatron program.Comment: 39 pages, 8 figure
Solar wind pressure pulseâdriven magnetospheric vortices and their global consequences
We report the in situ observation of a plasma vortex induced by a solar wind dynamic pressure enhancement in the nightside plasma sheet using multipoint measurements from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. The vortex has a scale of 5â10 Re and propagates several Re downtail, expanding while propagating. The features of the vortex are consistent with the prediction of the Sibeck (1990) model, and the vortex can penetrate deep (~8 Re ) in the dawnâdusk direction and couple to field line oscillations. Global magnetohydrodynamics simulations are carried out, and it is found that the simulation and observations are consistent with each other. Data from THEMIS ground magnetometer stations indicate a poleward propagating vortex in the ionosphere, with a rotational sense consistent with the existence of the vortex observed in the magnetotail. Key Points Solar wind pressure pulseâdriven vortex was observed in the magnetosphere Simulation and ground magnetic field data confirm this tailward moving vortex The vortex can penetrate deep inside the tail plasma sheet and couple to FLRsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107999/1/jgra51112.pd
Immersed boundary-finite element model of fluid-structure interaction in the aortic root
It has long been recognized that aortic root elasticity helps to ensure
efficient aortic valve closure, but our understanding of the functional
importance of the elasticity and geometry of the aortic root continues to
evolve as increasingly detailed in vivo imaging data become available. Herein,
we describe fluid-structure interaction models of the aortic root, including
the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the
sinotubular junction, that employ a version of Peskin's immersed boundary (IB)
method with a finite element (FE) description of the structural elasticity. We
develop both an idealized model of the root with three-fold symmetry of the
aortic sinuses and valve leaflets, and a more realistic model that accounts for
the differences in the sizes of the left, right, and noncoronary sinuses and
corresponding valve cusps. As in earlier work, we use fiber-based models of the
valve leaflets, but this study extends earlier IB models of the aortic root by
employing incompressible hyperelastic models of the mechanics of the sinuses
and ascending aorta using a constitutive law fit to experimental data from
human aortic root tissue. In vivo pressure loading is accounted for by a
backwards displacement method that determines the unloaded configurations of
the root models. Our models yield realistic cardiac output at physiological
pressures, with low transvalvular pressure differences during forward flow,
minimal regurgitation during valve closure, and realistic pressure loads when
the valve is closed during diastole. Further, results from high-resolution
computations demonstrate that IB models of the aortic valve are able to produce
essentially grid-converged dynamics at practical grid spacings for the
high-Reynolds number flows of the aortic root
First Observation and Measurement of the Decay K+- -> pi+- e+ e- gamma
Using the full data set of the NA48/2 experiment, the decay K+- -> pi+- e+ e-
gamma is observed for the first time, selecting 120 candidates with 7.3 +- 1.7
estimated background events. With K+- -> pi+- pi0D as normalisation channel,
the branching ratio is determined in a model-independent way to be Br(K+- ->
pi+- e+ e- gamma, m_eegamma > 260 MeV/c^2) = (1.19 +- 0.12_stat +- 0.04_syst) x
10^-8. This measured value and the spectrum of the e+ e- gamma invariant mass
allow a comparison with predictions of Chiral Perturbation Theory.Comment: 13 pages, 3 figures. Accepted for publication in Phys.Lett.
VHL substrate transcription factor ZHX2 as an oncogenic driver in clear cell renal cell carcinoma
Inactivation of the von Hippel-Lindau (VHL) E3 ubiquitin ligase protein is a hallmark of clear cell renal cell carcinoma (ccRCC). Identifying how pathways affected by VHL loss contribute to ccRCC remains challenging. We used a genome-wide in vitro expression strategy to identify proteins that bind VHL when hydroxylated. Zinc fingers and homeoboxes 2 (ZHX2) was found as a VHL target, and its hydroxylation allowed VHL to regulate its protein stability. Tumor cells from ccRCC patients with VHL loss-of-function mutations usually had increased abundance and nuclear localization of ZHX2. Functionally, depletion of ZHX2 inhibited VHL-deficient ccRCC cell growth in vitro and in vivo. Mechanistically, integrated chromatin immunoprecipitation sequencing and microarray analysis showed that ZHX2 promoted nuclear factor ÎșB activation. These studies reveal ZHX2 as a potential therapeutic target for ccRCC
Spin dynamics in semiconductors
This article reviews the current status of spin dynamics in semiconductors
which has achieved a lot of progress in the past years due to the fast growing
field of semiconductor spintronics. The primary focus is the theoretical and
experimental developments of spin relaxation and dephasing in both spin
precession in time domain and spin diffusion and transport in spacial domain. A
fully microscopic many-body investigation on spin dynamics based on the kinetic
spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published
in Physics Reports
Measurement of the Atmospheric Muon Spectrum from 20 to 3000 GeV
The absolute muon flux between 20 GeV and 3000 GeV is measured with the L3
magnetic muon spectrometer for zenith angles ranging from 0 degree to 58
degree. Due to the large exposure of about 150 m2 sr d, and the excellent
momentum resolution of the L3 muon chambers, a precision of 2.3 % at 150 GeV in
the vertical direction is achieved.
The ratio of positive to negative muons is studied between 20 GeV and 500
GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003
(stat.) +- 0.019 (syst.).Comment: Total 32 pages, 9Figure
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