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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 isoscalar T c c + tetraquark with a quark content of 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 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 T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed. The existence and properties of tetraquark states with two heavy quarks and two light antiquarks have been widely debated. Here, the authors use a unitarized model to study the properties of an exotic narrow state compatible with a doubly charmed tetraquark.

This article reports world averages of measurements of b -hadron, c -hadron, and τ -lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, C P  violation parameters, parameters of semileptonic decays, and Cabbibo–Kobayashi–Maskawa matrix elements.

A bstract An angular analysis of the rare decay B s 0 → ϕμ + μ − is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 8.4 fb − 1 . The observables describing the angular distributions of the decay B s 0 → ϕμ + μ − are determined in regions of q 2 , the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.

The Asian tiger mosquito, Aedes albopictus , is one of the world’s most dangerous invasive species. It has vector competence for a wide range of arboviruses such as chikungunya, dengue, Zika and Rift Valley fever viruses. The vector originated in Asia but has recently spread to the temperate regions of Europe and North America. Further spread to the north and the east and a shift to higher altitudes could be expected as a result of climate change. This makes modelling the regional climatic suitability for the establishment of A. albopictus in naïve regions a pressing issue. The future suitability and subsequent seasonal activity of the vector were investigated using three mechanistic models, with climatic data from the Eta Belgrade University-Princeton Ocean Model regional climate model. The results showed that after a slight decrease in suitability for the first part of the century, most of Serbia would become significantly more suitable for the establishment of A. albopictus . This is due to the simulated rise in seasonal and annual temperatures by the end of the twenty-first century. This study allows for the incorporation of regional heterogeneity in vector modelling. The spatial resolution of the maps obtained from a regional analysis is much higher than that acquired by a global model, allowing for detailed risk assessment and planning of surveillance focused on the habitats where the main introduction routes and climatic suitability are coupled. This work should be applied to all countries in the region with the risk of introduction or further spread of A. albopictus .

The Compact Linear Collider (CLIC) is an option for a future e + e - collider operating at centre-of-mass energies up to 3 TeV , providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: s = 350 GeV , 1.4 and 3 TeV . The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung ( e + e - → Z H ) and W W -fusion ( e + e - → H ν e ν ¯ e ), resulting in precise measurements of the production cross sections, the Higgs total decay width Γ H , and model-independent determinations of the Higgs couplings. Operation at s > 1 TeV provides high-statistics samples of Higgs bosons produced through W W -fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e + e - → t t ¯ H and e + e - → H H ν e ν ¯ e allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit.

A bstract The cross-sections of exclusive (coherent) photoproduction J/ψ and ψ (2S) mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5 . 02 TeV are measured using a data sample corresponding to an integrated luminosity of 228 ± 10 μb − 1 , collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for J/ψ and ψ (2S) mesons. The integrated cross-sections are measured to be σ J / ψ coh = 5 . 965 ± 0 . 059 ± 0 . 232 ± 0 . 262 mb and σ ψ 2 S coh = 0 . 923 ± 0 . 086 ± 0 . 028 ± 0 . 040 mb, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be σ ψ 2 S coh / σ J / ψ coh = 0 . 155 ± 0 . 014 ± 0 . 003, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.

A bstract The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies s = 380 GeV, 1 . 5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of t ̄ tH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.

A bstract A precision measurement of the Z boson production cross-section at 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 . The integrated cross-section is determined to be 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.

A bstract The production cross-section of the χ c 1 (3872) state relative to the ψ (2 S ) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb − 1 , respectively. The two mesons are reconstructed in the J/ψπ + π − final state. The ratios of the prompt and nonprompt χ c 1 (3872) to ψ (2 S ) production cross-sections are measured as a function of transverse momentum, p T , and rapidity, y , of the χ c 1 (3872) and ψ (2 S ) states, in the kinematic range 4 < p T < 20 GeV/ c and 2 . 0 < y < 4 . 5. The prompt ratio is found to increase with p T , independently of y . For the prompt component, the double ratio of the χ c 1 (3872) and ψ (2 S ) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of p T and centre-of-mass energy.

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 first 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.