Pavao, R. P., Liang, W. H., Nieves, J., & Oset, E. (2017). Predictions for Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790) (Xi(0)(C)(2815) and Xi(-)(b) -> (v)over-bar (l)l Xi(0)(C)(2790) (Xi(0)(C)(2815). Eur. Phys. J. C, 77(4), 265–12pp.
Abstract: We have performed calculations for the non-leptonic Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790)(J = 1/2) Xi(-)(b) -> pi(-) Xi(0)(C)(2815) (J = 3/2) and decays and the same reactions replacing the pi- by a D-s(-). At the same time we have also evaluated the semileptonic rates for and Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790). We look at the reactions from the perspective that the Xi(0(2790))(c) and Xi(0)(c)(2815()) resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions. We evaluate ratios of the rates of these reactions and make predictions that can be tested in future experiments. We also find that the results are rather sensitive to the coupling of the Xi(c)* resonances to the D*Sigma and D*A components.
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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). Measurement of the W boson polarisation in t(t)over-barevents from pp collisions at root s=8 TeV in the lepton plus jets channel with ATLAS. Eur. Phys. J. C, 77(4), 264–28pp.
Abstract: This paper presents a measurement of the polarisation of W bosons from t (t) over bar t decays, reconstructed in events with one high-p(T) lepton and at least four jets. Data from pp collisions at the LHC were collected at root s = 8 TeV and correspond to an integrated luminosity of 20.2 fb(-1). The angle theta* between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos theta* is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left-and right-handed polarisation states are F-0 = 0.709 +/- 0.019, F-L = 0.299 +/- 0.015 and F-R = – 0.008 +/- 0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the W tb vertex are set.
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Buchta, S., Chachamis, G., Draggiotis, P., & Rodrigo, G. (2017). Numerical implementation of the loop-tree duality method. Eur. Phys. J. C, 77(5), 274–15pp.
Abstract: We present a first numerical implementation of the loop-tree duality (LTD) method for the direct numerical computation of multi-leg one-loop Feynman integrals. We discuss in detail the singular structure of the dual integrands and define a suitable contour deformation in the loop three-momentum space to carry out the numerical integration. Then we apply the LTD method to the computation of ultraviolet and infrared finite integrals, and we present explicit results for scalar and tensor integrals with up to eight external legs (octagons). The LTD method features an excellent performance independently of the number of external legs.
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XENON Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2017). Removing krypton from xenon by cryogenic distillation to the ppq level. Eur. Phys. J. C, 77(5), 275–12pp.
Abstract: The XENON1T experiment aims for the direct detection of dark matter in a detector filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low. One major contributor is the beta-emitter Kr-85 which is present in the xenon. For XENON1T a concentration of natural krypton in xenon Kr-nat/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10(-15) mol/mol) is required. In this work, the design, construction and test of a novel cryogenic distillation column using the common McCabe-Thiele approach is described. The system demonstrated a krypton reduction factor of 6.4 . 10(5) with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of natKr/Xe < 26 ppq is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN.
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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 top-quark pair differential cross-sections in the e μchannel in pp collisions at root s=13 TeV using the ATLAS detector. Eur. Phys. J. C, 77(5), 292–30pp.
Abstract: This article presents measurements of t (t) over bar differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb(-1) of proton-proton data at a centre-of-mass energy of root s = 13 TeV recorded by the ATLAS experiment at the LHC in 2015. Differential crosssections are measured as a function of the transverse momentum and absolute rapidity of the top quark, and of the transverse momentum, absolute rapidity and invariant mass of the t (t) over bar system. The t (t) over bar events are selected by requiring one electron and onemuonof opposite electric charge, and at least two jets, one of which must be tagged as containing a b-hadron. The measured differential cross-sections are compared to predictions of next-to-leading order generators matched to parton showers and the measurements are found to be consistent with all models within the experimental uncertainties with the exception of the Powheg-Box + Herwig++ predictions, which differ significantly from the data in both the transverse momentum of the top quark and the mass of the t (t) over bar system.
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