3,224 research outputs found
Determination of Strange Sea Quark Distributions from Fixed-target and Collider Data
We present an improved determination of the strange sea distribution in the
nucleon with constraints coming from the recent charm production data in
neutrino-nucleon deep-inelastic scattering by the NOMAD and CHORUS experiments
and from charged current inclusive deep-inelastic scattering at HERA. We
demonstrate that the results are consistent with the data from the ATLAS and
the CMS experiments on the associated production of -bosons with
-quarks. We also discuss issues related to the recent strange sea
determination by the ATLAS experiment using LHC collider data.Comment: 23 pages, 14 figure
Seed conservation in ex situ genebanks - genetic studies on longevity in barley
Recognizing the danger due to a permanent risk of loss of the genetic variability of cultivated plants and their wild relatives in response to changing environmental conditions and cultural practices, plant ex situ genebank collections were created since the beginning of the last century. World-wide more than 6 million accessions have been accumulated of which more than 90% are stored as seeds. Research on seed longevity was performed in barley maintained for up to 34 years in the seed store of the German ex situ genebank of the Leibniz-Institute of Plant Genetics and Crop Plant Research in Gatersleben. A high intraspecific variation was detected in those natural aged accessions. In addition three doubled haploid barley mapping populations being artificial aged were investigated to study the inheritance of seed longevity. Quantitative trait locus (QTL) mapping was based on a transcript map. Major QTLs were identified on chromosomes 2H, 5H (two) and 7H explaining a phenotypic variation of up to 54%. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs
On direct measurement of the W production charge asymmetry at the LHC
The prospects for making a direct measurement of the W production charge
asymmetry at the LHC are discussed. A modification to the method used at the
Tevatron is proposed for measurements at the LHC. The expected sensitivity for
such a measurement to parton distribution functions is compared to that for a
measurement of the lepton charge asymmetry. The direct measurement approach is
found to be less useful for placing constraints on parton distribution
functions at the LHC than a measurement of the lepton charge asymmetry.Comment: 18 pages, 10 figures, v2: references and keywords updated v3:
Additional paragraph discussing inclusion of W asymmetry in global fits adde
Prototyping of petalets for the Phase-II Upgrade of the silicon strip tracking detector of the ATLAS Experiment
In the high luminosity era of the Large Hadron Collider, the HL-LHC, the
instantaneous luminosity is expected to reach unprecedented values, resulting
in about 200 proton-proton interactions in a typical bunch crossing. To cope
with the resultant increase in occupancy, bandwidth and radiation damage, the
ATLAS Inner Detector will be replaced by an all-silicon system, the Inner
Tracker (ITk). The ITk consists of a silicon pixel and a strip detector and
exploits the concept of modularity. Prototyping and testing of various strip
detector components has been carried out. This paper presents the developments
and results obtained with reduced-size structures equivalent to those foreseen
to be used in the forward region of the silicon strip detector. Referred to as
petalets, these structures are built around a composite sandwich with embedded
cooling pipes and electrical tapes for routing the signals and power. Detector
modules built using electronic flex boards and silicon strip sensors are glued
on both the front and back side surfaces of the carbon structure. Details are
given on the assembly, testing and evaluation of several petalets. Measurement
results of both mechanical and electrical quantities are shown. Moreover, an
outlook is given for improved prototyping plans for large structures.Comment: 22 pages for submission for Journal of Instrumentatio
Diffusing-wave spectroscopy of nonergodic media
We introduce an elegant method which allows the application of diffusing-wave
spectroscopy (DWS) to nonergodic, solid-like samples. The method is based on
the idea that light transmitted through a sandwich of two turbid cells can be
considered ergodic even though only the second cell is ergodic. If absorption
and/or leakage of light take place at the interface between the cells, we
establish a so-called "multiplication rule", which relates the intensity
autocorrelation function of light transmitted through the double-cell sandwich
to the autocorrelation functions of individual cells by a simple
multiplication. To test the proposed method, we perform a series of DWS
experiments using colloidal gels as model nonergodic media. Our experimental
data are consistent with the theoretical predictions, allowing quantitative
characterization of nonergodic media and demonstrating the validity of the
proposed technique.Comment: RevTeX, 12 pages, 6 figures. Accepted for publication in Phys. Rev.
The photon PDF from high-mass Drell Yan data at the LHC
Achieving the highest precision for theoretical predictions at the LHC requires the calculation of hard-scattering cross-sections that include perturbative QCD corrections up to (N)NNLO and electroweak (EW) corrections up to NLO. Parton distribution functions (PDFs) need to be provided with matching accuracy, which in the case of QED effects involves introducing the photon parton distribution of the proton, . In this work a determination of the photon PDF from fits to recent ATLAS measurements of high-mass Drell-Yan dilepton production at TeV is presented. This analysis is based on the xFitter framework, and has required improvements both in the APFEL program, to account for NLO QED effects, and in the aMCfast interface to account for the photon-initiated contributions in the EW calculations within MadGraph5_aMC@NLO. The results are compared with other recent QED fits and determinations of the photon PDF, consistent results are found
Flexible X-ray imaging detectors using scintillating fibers
We present early design and simulation work on a novel X-ray imaging detector. The intent of the FleX-RAY project is to create a digital X-ray detector that is capable of producing high-resolution images, is flexible enough to produce an image on a curved surface, and is capable of self-reporting its final shape. The X-rays will be detected on a sheet of scintillating optical fibers, which will guide the scintillation light to single-photon avalanche photodiodes. This setup allows the electronics and hardware to be moved out of the path of the X-ray beam, limiting the need for additional shielding. Self-shape-reporting will be achieved using a flexible ultra-thin glass substrate with optical waveguides and Bragg gratings, processed by femtosecond laser point-by-point writing. The functionalized glass substrate allows precise measurement of strains, which can be used to calculate the shape
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS
Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations
- …