NA48/2 Collaboration(Batley, J. R. et al), & Fiorini, L. (2017). Searches for lepton number violation and resonances in K-+/- -> pi μμdecays. Phys. Lett. B, 769, 67–76.
Abstract: The NA48/2 experiment at CERN collected a large sample of charged kaon decays to final states with multiple charged particles in 2003-2004. A new upper limit on the rate of the lepton number violating decay K-+/- -> pi(+/-)mu(+/-)mu(+/-) is reported: B( K-+/- -> pi(+/-)mu(+/-)mu(+/-)) < 8.6 x 10(-11) at 90% CL. Searches for two-body resonances X in K-+/- -> pi μμdecays (such as heavy neutral leptons N-4 and inflatons chi) are also presented. In the absence of signals, upper limits are set on the products of branching fractions B(K-+/- -> μN-+/-(4))B(N-4 -> pi mu) and B(K-+/- ->pi X-+/-)B(X -> mu(+),mu(-)) for ranges of assumed resonance masses and lifetimes. The limits are in the (10(-11),10(-9)) range for resonance lifetimes below 100 ps.
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Albiol, F., Corbi, A., & Albiol, A. (2017). Evaluation of modern camera calibration techniques for conventional diagnostic X-ray imaging settings. Radiol. Phys. Technol., 10(1), 68–81.
Abstract: We explore three different alternatives for obtaining intrinsic and extrinsic parameters in conventional diagnostic X-ray frameworks: the direct linear transform (DLT), the Zhang method, and the Tsai approach. We analyze and describe the computational, operational, and mathematical background differences for these algorithms when they are applied to ordinary radiograph acquisition. For our study, we developed an initial 3D calibration frame with tin cross-shaped fiducials at specific locations. The three studied methods enable the derivation of projection matrices from 3D to 2D point correlations. We propose a set of metrics to compare the efficiency of each technique. One of these metrics consists of the calculation of the detector pixel density, which can be also included as part of the quality control sequence in general X-ray settings. The results show a clear superiority of the DLT approach, both in accuracy and operational suitability. We paid special attention to the Zhang calibration method. Although this technique has been extensively implemented in the field of computer vision, it has rarely been tested in depth in common radiograph production scenarios. Zhang's approach can operate on much simpler and more affordable 2D calibration frames, which were also tested in our research. We experimentally confirm that even three or four plane-image correspondences achieve accurate focal lengths.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector. Eur. Phys. J. C, 77(2), 70–31pp.
Abstract: Direct searches for lepton flavour violation in decays of the Higgs and Z bosons with the ATLAS detector at the LHC are presented. The following three decays are considered: H -> e tau, H -> μtau, and Z -> μtau. The searches are based on the data sample of proton-proton collisions collected by the ATLAS detector corresponding to an integrated luminosity of 20.3 fb(-1) at a centre-of-mass energy of root s = 8 TeV. No significant excess is observed, and upper limits on the lepton-flavour-violating branching ratios are set at the 95% confidence level: Br(H -> e tau) < 1.04%, Br(H -> μtau) < 1.43%, and Br(Z -> μtau) < 1.69 x 10(-5).
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurements of charge and CP asymmetries in b-hadron decays using top-quark events collected by the ATLAS detector in pp collisions at root s=8 TeV. J. High Energy Phys., 02(2), 071–49pp.
Abstract: Same-and opposite-sign charge asymmetries are measured in lepton+ jets t (t) over bar events in which a b-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb(-1) from proton-proton collisions at a centre-of-mass energy of root s = 8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a b -hadron and are measured in a fi ducial region corresponding to the experimental acceptance. Four CP asymmetries (one mixing and three direct) are measured and are found to be compatible with zero and consistent with the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Observation of B+ -> J/psi 3 pi(+)2 pi(-) and B+ -> psi (2S)pi(+)pi(+)pi(-) decays. Eur. Phys. J. C, 77(2), 72–12pp.
Abstract: The decays B+-> J/psi 3 pi(+)2 pi(-) and B+ -> psi(2S)pi(+)pi(+)pi(-) are observed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment in proton- proton collisions at the centre-of-mass energies of 7 and 8 TeV. The branching fractions relative to that of B+ -> psi(2S)K+ are measured to be B(B+-> J/psi 3 pi(+)2 pi(-))/B(B+ -> psi (2S)K+) = (1.88 +/- 0.17 +/- 0.09)x10(-2). B(B+ -> psi(2S)pi(+)pi(+)pi(-))/B(B+ -> psi (2S)K+) = (3.04 +/- 0.50 +/- 0.26)X10(-2) where the first uncertainties are statistical and the second are systematic.
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