• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 88
  • 64
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 2678
  • 1057
  • 662
  • 510
  • 463
  • 397
  • 368
  • 250
  • 135
  • 70
  • 69
  • 67
  • 61
  • 61
  • 57
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Decays of heavy-light mesons : weak matrix elements from the lattice

Maynard, Christopher Michael January 1999 (has links)
This thesis describes a numerical study of weak matrix elements of the vector and axial vector currents relevant to the semi-leptonic and leptonic decays of <I>B</I> and <I>D</I> mesons from Lattice QCD. The simulation was performed in Quenched QCD on a 24<SUP>3</SUP> x 48 lattice at <I>β</I> = 6.2. The fermionic degrees of freedom were calculated using a non-perturbatively <I>O</I>(<I>a</I>) improved action. For a pseudoscalar final state in a semi-leptonic decay, only the vector current contributes and can be parameterised by two form factors which are functions of the momentum transfer squared. The main results for the form factors of the decays <I>B</I> → π at zero momentum transfer are: <I>f</I><SUB>+</SUB> (0) = <I>f</I><SUB>0 </SUB>(0) = 0.31<SUP>+3</SUP><SUB>-3 stat </SUB><SUP>+8</SUP><SUB>-8 sys</SUB><I> </I>The momentum dependence was found to be reasonably modelled by pole dominance models. The decay rate for <I>B</I> → π is calculated and compared to experiment allowing the CKM matrix element <I>V</I><SUB>ub</SUB> to be extracted. <I>V</I><SUB>ub</SUB> = 0.0027<SUP>+2</SUP><SUB>-2 stat </SUB><SUP>+7</SUP><SUB>-7 sys </SUB><SUP>+9</SUP><SUB>-9 exp</SUB><I> </I>The form factors for <I>D</I> → <I>K,</I> π were calculated and the momentum dependence was found to be reasonably modelled by pole dominance. For leptonic decays of pseudoscalar mesons, the axial current is parameterised by the decay constant, for B and D decays the results are <I>f<SUB>B</SUB></I> = 191<SUP>+4</SUP><SUB>-4 stat </SUB><SUP>+22</SUP><SUB>-22 sys</SUB> MeV <I>f<SUB>D</SUB></I> = 203<SUP>+3</SUP><SUB>-2 stat </SUB><SUP>+22</SUP><SUB>-10 sys</SUB> MeV<I> </I>The soft pion relation for the B meson which relates the ratio <I>f<SUB>B</SUB> / f<SUB>π</SUB></I> to <I>f</I><SUB>o</SUB>(<I>q</I><SUP>2</SUP><SUB>max</SUB>), is evaluated and found to be substantially violated.

Pion interactions in hydrogen and deuterium

Briggs, Geoffrey Arthur January 1966 (has links)
No description available.

The effects of Gamma radiation on a PBX containing TATB and the fluoropolymer FK-800

Connors, S. C. January 2014 (has links)
The polymer bonded explosive TCV is analogous to PBX compositions used in some nuclear weapons where the PBX will be exposed to high energy ionising gamma radiation. It is therefore important to study how gamma radiation affects the mechanical and chemical properties of the PBX. In this study 60Co was used to irradiate samples of the TCV, its FK-800 binder and TATB explosive filler, at 37.5 °C, to total doses up to 200 kGy in air and under vacuum. Post irradiation analysis consisted of mechanical, thermal and chemical analysis of the irradiated materials. Results from the radiolysis of the FK-800 showed predominant main chain scission taking place, these results in the release of volatile fluorine containing products and an increase in the polymer’s crystallinity. The changes to the FK-800’s structural properties result in an increase in Young’s modulus and yield stress whilst reducing both ultimate tensile strength and elongation at maximum stress. Dynamic mechanical analysis shows the material softening initially upon irradiation, then stiffening as crystallinity increased. TATB was found to turn green and have increased sensitiveness to impact and electric spark discharge with gamma radiation. Analysis by HPLC and LC-MS identified a decomposition product with a mass of 240 g mol-1. No significant changes to the mechanical properties of TCV were identified; however, its sensitiveness to impact and electric spark discharge were found to increase similar to TATB’s. In conclusion, gamma irradiation of TCV has identified significant changes to the mechanical and chemical properties of the FK-800 binder, have little to no effect on mechanical properties of PBX up to 100 kGy. The predominant radiolytic effects on TCV were to its hazard characteristics caused by changes in the TATB. A mono-furazan derivative of TATB has been suggested as the decomposition product identified, and as a possible cause for the increase in sensitiveness of TATB upon gamma irradiation.

The study of D and D meson production in deep inelastic scattering at HERA II with the ZEUS detector

Nichoass, D. January 2008 (has links)
Installed in 2000/2001, the ZEUS micro vertex detector provided the capability to reconstruct secondary vertices displaced from the primary by distances of the order 100 pm. In order to be useful for tagging heavy flavour mesons the micro vertex detector was aligned with a combination of tracks from cosmic events and ep events in the HERA collider. This thesis presents measurements of and D meson production obtained with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb-1. The measurements cover the kinematic range 5 < Q2 < 1000 GeV2, 0.02 < y < 0.7, 1.5 < p$ < 15 GeV and 11 < 1.6. Combinatorial background to the D meson signals is reduced by using the ZEUS micro vertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading order QCD which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open charm contribution, F2ca, to the proton structure function, F2.

Top quark physics at the LHC with the CMS detector

Senkin, Sergey January 2014 (has links)
In this thesis, the top quark mass and top quark pair differential cross section measurements are presented, based on data collected by the CMS detector at the LHC in 2011 and 2012. The mass of the top quark is measured using a sample of top-antitop candidate events with one electron and at least four jets in the final state, obtained from approximately 5.0 fb -1 of data at a centre of mass energy of Vs = 7 TeV. The top quark mass is extracted from a combined likelihood fit, and measured to be 172.87 ± 0.27 (stat.) ± 2.17 (syst.) GeV. The normalised differential cross section of top quark pair production is measured with respect to a number of event-level observables, including missing transverse energy, scalar sum of jet transverse momenta, scalar sum of total event transverse momenta, and leptonically decaying W boson transverse momentum and transverse mass. The analysis is performed for semileptonic top-antitop events, with either an electron or a muon, and at least four jets in the final state. Approximately 19.7 fb -1 of data at a centre of mass energy of Vs = 8 TeV are used. No significant deviations from the Standard Model predictions are observed.

The critical behaviour of Reggeon field theory

Behrsin, Mark Peter January 1977 (has links)
No description available.

Absolute cross sections for charge exchange to the continuum

Cranage, R. W. January 1975 (has links)
No description available.

The development of Compton imaging techiques for the GammaKev project using the AGATA A006 detector

Slee, Michael John January 2015 (has links)
This thesis presents the methods and results different position analysis techniques provide for Compton image reconstruction. The AGATA A006 detector a highly segmented large volume detector has been utilised for the analysis of data presented in this thesis. This data contained within the thesis was part of the GammaKEV project, which aimed to develop a portable gamma-ray spectrometer for use on a nuclear submarine, with this work focusing on how the improvement of position determination can improve the reconstructed image FWHM. The AGATA A006 detector is a 80x80x90 mm3 HPGe, 36 segment and one core, coaxial detector. The average energy resolution over all the segments and core was found to be 2.7 ke V. This work shows the improvement that parametric pulse shape analysis can make in large detector segments to Compton image reconstruction. Two 1332 keV 60CO sources have been placed in front of the AGATA A006 detector at 100 mm and have been imaged using a simple back projection Compton image reconstruction code developed at the University of Liverpool. A method has been developed to apply parametric PSA to improve the precision of locating the position of interaction within the segments. A GEANT4 simulation has been adapted to replicate the experimental setup utilising a Gaussian smearing function applied to the simulated x, y and z position and energy data to assess the improvement that parametric PSA provides to the discrimination of position within the detector segments. The simulated energy and position smeared data reconstructed image resolution has been compared to the experimental data reconstructed image resolution. It has been found that the parametric PSA method developed in this thesis, will give a position resolution of 3 ± 0.5 mm within the segments of the crystal when compared to a 15 ± 0.5 mm position resolution for data reconstructed without utilising parametric PSA.

Jet structure in a quark-parton model [and] New parametrisations and tests of unitary bounds in meson-nucleon scattering

Cotterill, Philip Andrew January 1979 (has links)
No description available.

Single sideband zone plates in coded aperture imaging of radionuclide distributions

Crippin, David D. M. January 1977 (has links)
No description available.

Page generated in 0.0339 seconds