ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Observation of a New chi(b) State in Radiative Transitions to Y(1S) and Y(2S) at ATLAS. Phys. Rev. Lett., 108(15), 152001–17pp.
Abstract: The chi(b)(np) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at root s=7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb(-1), these states are reconstructed through their radiative decays to Y(1S,2S) with Y ->mu(+)mu(-). In addition to the mass peaks corresponding to the decay modes chi(b)(1P,2P)-> Y(1S)gamma, a new structure centered at a mass of 10.530 +/- 0.005(stat)+/- 0.009(syst) GeV is also observed, in both the Y(1S)gamma and Y(2S)gamma decay modes. This structure is interpreted as the chi(b)(3P) system.
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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). Observation of New Resonances in the Lambda(0)(b)pi(+)pi(-) System. Phys. Rev. Lett., 123(15), 152001–11pp.
Abstract: We report the observation of a new structure in the Lambda(0)(b)pi(+)pi(- )spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9 fb(-1), collected at root s = 7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m(Lambda b(6146)0) = 6146.17 +/- 0.33 +/- 0.22 +/- 0.16 MeV, m(Lambda b(6152)0) = 6152.51 +/- 0.26 +/- 0.22 +/- 0.16 MeV, Gamma(Lambda b(6146)0) = 2.9 +/- 1.3 +/- 0.3 MeV, Gamma(Lambda b(6152)0) = 2.1 +/- 0.8 +/- 0.3 MeV,with a mass splitting of Delta m = 6.34 +/- 0.32 +/- 0.02 MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Lambda(0)(b) baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Lambda(b)(1D)(0) states.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2020). Measurements of the Absolute Branching Fractions of B-+/- -> K(+/-)Xc(c)over-bar. Phys. Rev. Lett., 124(15), 152001–8pp.
Abstract: A study of the two-body decays B-+/- -> Xc (c) over barK +/-, where X-c (c) over bar refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424 fb(-1). The absolute determination of branching fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B-+/- -> X(3872)K+ at the 3 sigma level. The absolute branching fraction B[B+ -> X(3872)K+] = [2.1 +/- 0.6(stat) +/- 0.3(syst)] x 10(-4) is measured for the first time. It follows that B[X(3872) -> J/psi pi(+)pi(-)] = (4.1 +/- 1.3)%, supporting the hypothesis of a molecular component for this resonance.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2018). Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at root s=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 121(15), 152002–20pp.
Abstract: This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μmu, or e mu) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb(-1) of protonproton collision data taken at root s = 13 TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within 2 sigma of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.
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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). Model-Independent Observation of Exotic Contributions to B degrees -> J/psi K+pi(-) Decays. Phys. Rev. Lett., 122(15), 152002–10pp.
Abstract: An angular analysis of B degrees -> J/psi K+pi(-) decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected with the LHCb detector. The m(K+pi(-) ) spectrum is divided into fine bins. In each m(K+pi(-)) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+pi(-) system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J/psi pi(-)) vs m(K+pi(-)) plane suggests structures near m(J/psi pi(-)) = 4200 and 4600 MeV.
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