Browsing by Issue Date, starting with "2019-09-02"
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- The Role of the $t{\bar t}h$ Rest Frame in Direct Top-Quark Yukawa Coupling MeasurementsPublication . Andrea Ferroglia; Miguel C. N. Fiolhais; Emanuel Gouveia; António OnofreThis paper studies new possibilities to directly measure a hypothetical $CP$-odd (pseudoscalar) component in the top-quark Yukawa coupling. In particular, the role of the $t{\bar t} h$ center-of-mass rest frame in the associated production of a top pair and a $h$ boson at the LHC is explored. The $h$ boson is assumed to have both a $CP$-even (scalar) and a $CP$-odd coupling to the top quark. The relative strength of the scalar and pseudoscalar components is regulated by an angle $\alpha$. Observables sensitive to the nature of the top-quark Yukawa coupling are proposed. These observables are defined in terms of the transverse and longitudinal projections of $t$, $\bar{t}$ and $h$ momenta with respect to the beam axis in the $t{\bar t} h$ rest frame. Distributions differential with respect to those observables are evaluated up to NLO in QCD. These distributions are found to be sensitive to the $CP$ nature of the coupling. Dileptonic final states of the $t{\bar t} h$ system (with $h\rightarrow b\bar b$) are used, after fast DELPHES detector simulation and full event reconstruction through a kinematic fit, as a case study to test the observables' sensitivity to the $CP$ nature of the coupling. Confidence levels are presented as a function of the total integrated LHC luminosity for the case of exclusion of a pure $CP$-odd coupling against the Standard Model $CP$-even hypothesis. By using observables evaluated in the $t{\bar t} h$ system, the luminosity needed to directly probe the $CP$ properties of the top-quark Yukawa coupling at the High-Luminosity run of the LHC can be decreased by a few hundred inverse femtobarns, when compared to analyses that use observables in the laboratory rest frame. In addition, transverse momentum distributions of the $h$ boson and top quarks are found to provide no more discriminant power than a counting experiment.
- MDMA Intoxication in potential donor with cardiac arrest – A case reportPublication . Castro, André Lobo; Tarelho, Sónia; Almeida, Dina; Sousa, Lara; Franco, João Miguel; Teixeira, HelenaAmphetamines consumption is still an important public health issue, namely in terms of compounds variability and disposition to consumers. However, some of them, still classic substances, keep standing in the illicit market, with remarkable and continuous success. That is the case of MDMA. Nevertheless, there is always new information and data on MDMA intoxication, both in vivo as in post-mortem context. The authors report an intoxication case with MDMA in an 18 years old male, who was considered a potential organ donor, after a cardiac arrest. Whole blood samples were collected in vivo, at the Emergency Room (ER), in different moments, and post-mortem, at the Forensic Pathology Service of the National Institute of Legal Medicine and Forensic Science. After a general screening procedure, samples were extracted by an SPE procedure (OASIS® MCX) followed by a GC-MS single quad analysis. The post-mortem whole blood sample was positive for Lidocaine (< 500 ng/mL), compatible with ER intervention, and positive for MDMA (2278 ng/mL) and MDA (49 ng/mL), while the whole blood samples collected in vivo (during the maintenance of the individual under advanced life support), were positive for MDMA (between 504 ng/mL and 1918 ng/mL) and MDA (between 20 ng/mL and 89 ng/mL). The samples were negative for other substances, namely ethanol, other drugs of abuse and medicines. Interpretation of these results is pivotal to understand the behaviour of the substance. So, in this case, MDMA post-mortem behaviour should be carefully evaluated, considering as possible influencers, in the specific context of the case, the time lapse between the death verification, the maintenance of the advanced life support and the body manipulation for organ collection purposes. Also referred and discussed is the ante-mortem/post-mortem ratio of MDMA obtained values, compared with literature references. No doubt that death was due to MDMA intoxication, but information from the in vivo samples analysis suggests that this type of sample should also be considered, in a complementary role, whenever possible.