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  1. Realistic fracture simulations in rock as a heterogeneous brittle material with significant inherent randomness require the use of models that incorporate its inhomogeneities and statistical variability. The high dependence of their fracture progress on microstructural defects results in wide scatter in their ultimate strength and the so-called size effect. This paper proposes an approach based on statistical volume elements (SVEs) to characterize rock fracture strength at the mesoscale. The use of SVEs ensures that the material randomness is maintained upon averaging of microscale features. Because the fracture strength varies not just spatially, but also by the angle of loading, thismore »work includes angular variability to properly model a heterogeneous rock domain. Two different microcrack distributions, one angularly uniform and one angularly biased towards a specific angle, are used to show that implementing angle into the random field provides the most realistic fracture simulation. An adaptive asynchronous spacetime discontinuous Galerkin (aSDG) finite element method is used to perform the dynamic fracture simulations.« less
  2. Abstract Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D 0 D 0 π + mass spectrum just below the D *+ D 0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalarmore »$${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + tetraquark with a quark content of $${{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}\overline{{{{{{\rm{u}}}}}}}\overline{{{{{{\rm{d}}}}}}}$$ c c u ¯ d ¯ and spin-parity quantum numbers J P  = 1 + . Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D *+ mesons is consistent with the observed D 0 π + mass distribution. To analyse the mass of the resonance and its coupling to the D * D system, a dedicated model is developed under the assumption of an isoscalar axial-vector $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state decaying to the D * D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.« less
    Free, publicly-accessible full text available December 1, 2023
  3. Abstract Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively 1,2 . Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a $$\overline{{{{{u}}}}}$$ u ¯ and a $$\overline{{{{{d}}}}}$$ d ¯ quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of D 0 D 0 π + mesons just below the D *+ D 0 mass threshold. The near-threshold mass together with the narrow widthmore »reveals the resonance nature of the state.« less
    Free, publicly-accessible full text available July 1, 2023
  4. A bstract A precision measurement of the Z boson production cross-section at $$ \sqrt{\mathrm{s}} $$ s = 13 TeV in the forward region is presented, using pp collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb − 1 . The production cross-section is measured using Z → μ + μ − events within the fiducial region defined as pseudorapidity 2 . 0 < η < 4 . 5 and transverse momentum p T > 20 GeV /c for both muons and dimuon invariant mass 60 < M μμ < 120 GeV /c 2 .more »The integrated cross-section is determined to be $$ \sigma \left(Z\to {\mu}^{+}{\mu}^{-}\right)=196.4\pm 0.2\pm 1.6\pm 3.9\ \mathrm{pb}, $$ σ Z → μ + μ − = 196.4 ± 0.2 ± 1.6 ± 3.9 pb , where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.« less
    Free, publicly-accessible full text available July 1, 2023
  5. A bstract Coherent production of J/ψ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about 10 μb −1 . The J/ψ mesons are reconstructed in the dimuon final state and are required to have transverse momentum below 1 GeV. The cross-section within the rapidity range of 2 . 0 < y < 4 . 5 is measured to be 4 . 45 ± 0 . 24 ± 0 . 18 ± 0 . 58 mb, where the firstmore »uncertainty is statistical, the second systematic and the third originates from the luminosity determination. The cross-section is also measured in J/ψ rapidity intervals. The results are compared to predictions from phenomenological models.« less
    Free, publicly-accessible full text available July 1, 2023
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  10. A bstract The $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 . 4 fb − 1. The $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is reconstructed partially, where the photon from the $$ {\varXi}_c^{\prime +}\to {\varXi}_c^{+}\gamma $$ Ξ c ′ + → Ξ c + γ decay is not reconstructed and the pK − π + finalmore »state of the $$ {\varXi}_c^{+} $$ Ξ c + baryon is employed. The $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + branching fraction relative to that of the $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{+}{\pi}^{+} $$ Ξ cc + + → Ξ c + π + decay is measured to be 1 . 41 ± 0 . 17 ± 0 . 10, where the first uncertainty is statistical and the second systematic.« less
    Free, publicly-accessible full text available May 1, 2023