474 research outputs found
Nonperturbative renormalisation of composite operators with overlap quarks
We compute non-perturbatively the renormalisation constants of composite
operators on a lattice with lattice spacing = 0.093 fm
for the overlap fermion action by using the regularisation independent (RI)
scheme. The quenched gauge configurations are generated by tadpole improved
plaquette plus rectangle action. We test the perturbative continuum relation
and and find that they agree well above = 1.6 GeV.
We also perform a Renormalisation Group analysis at the next-to-next-to-leading
order and convert the renormalisation constants to the scheme.Comment: Talk given at LHP2003, Cairns, Australi
Electromagnetic Form Factors with FLIC fermions
The Fat-Link Irrelevant Clover (FLIC) fermion action provides a new form of
nonperturbative O(a) improvement and allows efficient access to the light
quark-mass regime. FLIC fermions enable the construction of the
nonperturbatively O(a)-improved conserved vector current without the
difficulties associated with the fine tuning of the improvement coefficients.
The simulations are performed with an O(a^2) mean-field improved
plaquette-plus-rectangle gluon action on a 20^3 x 40 lattice with a lattice
spacing of 0.128 fm, enabling the first simulation of baryon form factors at
light quark masses on a large volume lattice.
Magnetic moments, electric charge radii and magnetic radii are extracted from
these form factors, and show interesting chiral nonanalytic behavior in the
light quark mass regime.Comment: Presented by J.Zanotti at the Workshop on Lattice Hadron Physics,
Cairns, Australia, 2003. 7pp, 8 figure
Measuring primordial gravitational waves from CMB B-modes in cosmologies with generalized expansion histories
We evaluate our capability to constrain the abundance of primordial tensor
perturbations in cosmologies with generalized expansion histories in the epoch
of cosmic acceleration. Forthcoming satellite and sub-orbital experiments
probing polarization in the CMB are expected to measure the B-mode power in CMB
polarization, coming from PGWs on the degree scale, as well as gravitational
lensing on arcmin scales; the latter is the main competitor for the measurement
of PGWs, and is directly affected by the underlying expansion history,
determined by the presence of a DE component. In particular, we consider early
DE possible scenarios, in which the expansion history is substantially modified
at the epoch in which the CMB lensing is most relevant. We show that the
introduction of a parametrized DE may induce a variation as large as 30% in the
ratio of the power of lensing and PGWs on the degree scale. We find that
adopting the nominal specifications of upcoming satellite measurements the
constraining power on PGWs is weakened by the inclusion of the extra degrees of
freedom, resulting in a reduction of about 10% of the upper limits on r in
fiducial models with no GWs, as well as a comparable increase in the error bars
in models with non-zero r. Moreover, we find that the inclusion of sub-orbital
CMB experiments, capable of mapping the B-mode power up to the angular scales
affected by lensing, can restore the forecasted performances with a
cosmological constant. Finally, we show how the combination of CMB data with
Type Ia SNe, BAO and Hubble constant allows to constrain simultaneously r and
the DE quantities in the parametrization we consider, consisting of present
abundance and first redshift derivative of the energy density. We compare this
study with results obtained using the forecasted lensing potential measurement
precision from CMB satellite observations, finding consistent results.Comment: 17 pages, 9 figures, accepted for publication by JCAP. Modified
version after the referee's comment
A Lattice Study of the Magnetic Moment and the Spin Structure of the Nucleon
Using an approach free from momentum extrapolation, we calculate the nucleon
magnetic moment and the fraction of the nucleon spin carried by the quark
angular momentum in the quenched lattice QCD approximation. Quarks with three
values of lattice masses, 210, 124 and 80 MeV, are formulated on the lattice
using the standard Wilson approach. At every mass, 100 gluon configurations on
16^3 x 32 lattice with \beta=6.0 are used for statistical averaging. The
results are compared with the previous calculations with momentum
extrapolation. The contribution of the disconnected diagrams is studied at the
largest quark mass using noise theory technique.Comment: 14 pages, 3 figures, Talk given at Lattice2001, Berlin, German
Equations of State in the Brans-Dicke cosmology
We investigate the Brans-Dicke (BD) theory with the potential as cosmological
model to explain the present accelerating universe. In this work, we consider
the BD field as a perfect fluid with the energy density and pressure in the
Jordan frame. Introducing the power-law potential and the interaction with the
cold dark matter, we obtain the phantom divide which is confirmed by the native
and effective equation of state. Also we can describe the metric gravity
with an appropriate potential, which shows a future crossing of phantom divide
in viable gravity models when employing the native and effective
equations of state.Comment: 23 pages, 7 figure
Track Finding Efficiency in BaBar
We describe several studies to measure the charged track reconstruction
efficiency and asymmetry of the BaBar detector. The first two studies measure
the tracking efficiency of a charged particle using and initial state
radiation decays. The third uses the decays to study the asymmetry in
tracking, the fourth measures the tracking efficiency for low momentum tracks,
and the last measures the reconstruction efficiency of particles. The
first section also examines the stability of the measurements vs BaBar running
periods.Comment: 20 pages, 30 figures, Submitted to Nuclear Instruments and Methods in
Physics Research
Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider
This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-→e+e- and (for the ϒ(4S) only) e+e-→μ+μ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-→e+e- and e+e-→μ+μ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the ϒ(3S) and ϒ(2S) resonances, an additional uncertainty arises due to ϒ→e+e-X background. For data collected off the ϒ resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the ϒ(4S), 0.58% (0.72%) for the ϒ(3S), and 0.68% (0.88%) for the ϒ(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l’Energie Atomique and Institut National de Physique Nucléaire et de Physiquedes Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e Innovación (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)
Double volume reflection of a proton beam by a sequence of two bent crystals
The doubling of the angle of beam deflection due to volume reflection of protons by a sequence of two bent silicon crystals was experimentally observed at the 400 GeV proton beam of the CERN SPS. A similar sequence of short bent crystals can be used as an efficient primary collimator for the Large Hadron Collider
The effects of age on health-related quality of life in cancer populations: A pooled analysis of randomized controlled trials using the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 involving 6024 cancer patients.
Cancer incidence increases exponentially with advancing age, cancer patients live longer than in the past, and many new treatments focus on stabilizing disease and HRQOL. The objective of this study is to examine how cancer affects patients' HRQOL and whether their HRQOL is age-dependent.Data from 25 EORTC randomized controlled trials was pooled. EORTC QLQ-C30 mean scores for the cancer cohort and five general population cohorts were compared to assess the impact of cancer on patients' HRQOL. Within the cancer cohort, multiple linear regressions (two-sided level P-value = 0.05 adjusted for multiple testing.) were used to investigate the association between age and HRQOL, adjusted for gender, WHO performance status (PS), distant metastasis and stratified by cancer site. A difference of 10 points on the 0-100 scale was considered clinically important.Cancer patients generally have worse HRQOL compared to the general population, but the specific HRQOL domains impaired vary with age. When comparing the cancer versus the general population, young cancer patients had worse financial problems, social and role functioning, while the older cancer groups had more appetite loss. Within the cancer cohort, HRQOL was worse with increasing age for physical functioning and constipation, and better with increasing age for social functioning, insomnia and financial problems (all p < 0.05).HRQOL is impaired in cancer patients compared to the general population, but the impact on specific HRQOL domains varies by age. Within the cancer population, some HRQOL components improve with age while others deteriorate. Optimal care for older cancer patients should target HRQOL domains most relevant to this population
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