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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2014). Measurement of the production of a W boson in association with a charm quark in pp collisions at root s=7 TeV with the ATLAS detector. J. High Energy Phys., 05(5), 068–67pp.
Abstract: The production of a W boson in association with a single charm quark is studied using 4.6 fb(-1) of pp collision data at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96(-0.30)(+0.26) at Q (2) = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W (+) +)/sigma(W (-) + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-(s) over bar quark asymmetry.
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Gersabeck, E., & Pich, A. (2020). Tau and charm decays. C. R. Phys., 21(1), 75–92.
Abstract: A summary of recent precise results in tau and charm physics is presented. Topics include leptonic and hadronic tau decays, lepton flavour and lepton number violation, charm mixing and CP violation, leptonic and semileptonic charm decays, rare decays and spectroscopy.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Search for charge-parity violation in semileptonically tagged D0 → K+ π- decays. J. High Energy Phys., 03(3), 149–30pp.
Abstract: An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of D-0 -> K+ pi(-) and D-0 -> K- pi(+) decay rates is measured as a function of the decay time of the D-0 meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding (B) over bar -> D*(2010)(+) mu(-) X and D*(2010)(+) -> D-0 pi(+) decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV and corresponding to an integrated luminosity of 5.4 fb(-1). The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be y' = (5.8 +/- 1.6) x10(-3) and (x')(2) = (0.0 +/- 1.2) x10(-4). No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be A(D) = (2.3 +/- 1.7)%.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Study of Ds1(2460)+ → Ds+ π+π- in B → (D)over-bar(*)Ds+π+π- decays. Sci. Bull., 70(9), 1432–1444.
Abstract: An amplitude analysis of the D-s1(2460)(+) -> D-s(+)pi(+)pi(-) transition is performed simultaneously in B-0 -> D-Ds+pi(+)pi(-), B+ -> (D) over bar D-0(s)+pi(+)pi(-), and B-0 -> D*D--(s)+pi(+)pi(-) decays. The study is based on a data sample of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of root s = 7,8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb(-1). A clear double-peak structure is observed in the m(pi(+)pi(-)) spectrum of the D-s1(2460)(+) -> D-s(+)pi(+)pi(-) decay. The data can be described either with a model including f(0)(500), f(0)(980), and f(2)(1270) resonances, in which the contributions of f(0)(980) and f(2)(1270) are unexpectedly large, or with a model including f(0)(500), a doubly charged open-charm tetraquark state T-c (s) over bar(++) and its isospin partner T-c (s) over bar(0). If the former is considered implausible, the T-c (s) over bar states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two T-c (s) over bar states, their mass and width are determined to be (2327 +/- 13 +/- 13) MeV and (96 +/- 16(-23)(+170)) MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the DK threshold, and a spin-parity of 0(+) is favoured with high significance. (c) 2025 The Authors. Published by Elsevier B.V. and Science China Press.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). A search for Xi(++)(cc) -> D(+)pK(-)pi(+) decays. J. High Energy Phys., 10(10), 124–21pp.
Abstract: A search for the Xi(++)(cc) baryon through the Xi(++)(cc) -> D(+)pK(-)pi(+) decay is performed with a data sample corresponding to an integrated luminosity of 1.7 fb(-1) recorded by the LHCb experiment in pp collisions at a centre-of-mass energy of 13 TeV. No significant signal is observed in the mass range from the kinematic threshold of the decay to 3800 MeV/c(2). An upper limit is set on the ratio of branching fractions R = B(Xi(++)(cc) -> D(+)pK(-)pi(+))/B(Xi(++)(cc) -> A(c)(+) K- pi(+)pi(+)) with R < 1.7 (2.1) x 10(-2) at the 90% (95%) confidence level at the known mass of the Xi(++)(cc) state.
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