596 research outputs found

    First Measurement of Charged Current Cross Sections with Longitudinally Polarised Positrons at HERA

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    The analysis presented in this thesis concerns the e+pe^{+}p deep inelastic charged current scattering cross sections measured with the H1 detector at HERA. The analysed data were taken in the years 2003-04 at a centre-of-mass energy s=319¬†GeV\sqrt{s} = 319 \ GeV and comprise two periods of positron beams with positive and negative longitudinal polarisation, corresponding to an integrated luminosity of 26.9 pb‚ąí1pb^{-1} and 20.7 pb‚ąí1pb^{-1}, respectively. The cross sections are measured in a kinematic region of four-momentum transfer squared Q2‚©ĺ300¬†GeV2Q^2 \geqslant 300 \ GeV^2 and inelasticity y‚©Ĺ0.9y \leqslant 0.9. \\ From the analysed data the polarisation dependence of the total charged current cross section is determined for the first time at high Q2Q^2. The results are compared with predictions of the Standard Model and found to be in agreement, i.e. possible contributions from non-standard right-handed currents are consistent with zero

    A determination of mc(mc) from HERA data using a matched heavy-flavor scheme

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    The charm quark mass is one of the fundamental parameters of the Standard Model Lagrangian. In this work we present a determination of the MSbar charm mass from a fit to the inclusive and charm HERA deep-inelastic structure function data. The analysis is performed within the xFitter framework, with structure functions computed in the FONLL general-mass scheme as implemented in APFEL. In the case of the FONLL-C scheme, we obtain mc(mc) = 1.335 +- 0.043(exp) +0.019 -0.000(param) +0.011 -0.008(mod) +0.033 -0.008(th) GeV. We also perform an analogous determination in the fixed-flavor-number scheme at next-to-leading order, finding mc(mc) = 1.318 +- 0.054(exp) +0.011 -0.010(param) +0.015 -0.019(mod) +0.045 -0.004(th) GeV, compatible with the FONLL-C value. Our results are consistent with previous determinations from DIS data as well as with the PDG world average.Comment: 37 pages, 12 figures, 3 table

    Impact of heavy-flavour production cross sections measured by the LHCb experiment on parton distribution functions at low x

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    The impact of recent measurements of heavy-flavour production in deep inelastic epep scattering and in pppp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions xx of the proton momentum, down to x‚ąľ5√ó10‚ąí6x \sim 5 \times 10^{-6}. This kinematic range is currently not covered by other experimental data in perturbative QCD fits

    The PDF4LHC report on PDFs and LHC data: Results from Run I and preparation for Run II

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    The accurate determination of the Parton Distribution Functions (PDFs) of the proton is an essential ingredient of the Large Hadron Collider (LHC) program. PDF uncertainties impact a wide range of processes, from Higgs boson characterisation and precision Standard Model measurements to New Physics searches. A major recent development in modern PDF analyses has been to exploit the wealth of new information contained in precision measurements from the LHC Run I, as well as progress in tools and methods to include these data in PDF fits. In this report we summarise the information that PDF-sensitive measurements at the LHC have provided so far, and review the prospects for further constraining PDFs with data from the recently started Run II. This document aims to provide useful input to the LHC collaborations to prioritise their PDF-sensitive measurements at Run II, as well as a comprehensive reference for the PDF-fitting collaborations.Comment: 55 pages, 13 figure

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an