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  1. 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
  2. Free, publicly-accessible full text available May 1, 2023
  3. Abstract A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 . The LLPmore »lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at $$\sqrt{s} = 13\text {\,TeV} $$ s = 13 \,TeV , corresponding to an integrated luminosity of 5.4 $$\text {\,fb} ^{-1}$$ \,fb - 1 . No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.« less
    Free, publicly-accessible full text available April 1, 2023
  4. Free, publicly-accessible full text available February 1, 2023
  5. Abstract Mesons comprising a beauty quark and strange quark can oscillate between particle ( $${B}_{\mathrm{s}}^{0}$$ B s 0 ) and antiparticle ( $${\overline{B}}_{\mathrm{s}}^{0}$$ B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δ m s . Here we present a measurement of Δ m s using $${B}_{\mathrm{s}}^{0}\to {D}_{\mathrm{s}}^{-}$$ B s 0 → D s − π + decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δ m s  = 17.7683 ± 0.0051 ± 0.0032 ps −1 , where the firstmore »uncertainty is statistical and the second is systematic. This measurement improves on the current Δ m s precision by a factor of two. We combine this result with previous LHCb measurements to determine Δ m s  = 17.7656 ± 0.0057 ps −1 , which is the legacy measurement of the original LHCb detector.« less
    Free, publicly-accessible full text available January 1, 2023
  6. Free, publicly-accessible full text available September 1, 2022