Effective Theory for a Heavy Scalar Coupled to the SM via Vector-Like Quarks

We illustrate the application of the recently developed SCET$_{\rm BSM}$ framework in the context of a specific model, in which the Standard Model (SM) is supplemented by a heavy scalar $S$ and three generations of heavy, vector-like quarks $\Psi$. We construct the appropriate effective field theory for two-body decays of $S$ into SM particles. We explicitly compute the Wilson coefficients of the SCET$_{\rm BSM}$ operators appearing at leading and next-to-leading order (NLO) in an expansion in powers of $v/M_S$, as well as for a subset of operators arising at NNLO, retaining the full dependence on the ratio $M_S/M_\Psi$. For the phenomenologically most relevant decay channels of the heavy scalar, we study the impact of resummation effects of Sudakov logarithms on the decay rates.Comment: 11 pages, 6 figure

Top Quark Charge Asymmetry: Searching for Light Axigluons in top pair + jet Production at the LHC

We investigate the discovery potential of light color-octet bosons in the mass range of 100 - 400 GeV in exclusive top-pair plus jet production at the LHC. We study the impact of such bosons on the incline, the energy and the rapidity asymmetries. We show that light axigluons with large couplings to quarks can be discovered at the LHC with a luminosity of a few inverse fb. Almost all of the considered axigluon parameter space can be probed using the already available 2011/2012 LHC data. In a small-coupling scenario, axigluons could be discovered using the charge asymmetry with 65 inverse fb at the LHC and a center of mass energy of 14 TeV. We furthermore show that top pair+jet production could reveal the existence of scenarios where axigluons couple with a different strength to up- and down-type quarks.Comment: 25 pages, 11 figures, 1 tabl

Consistent Searches for SMEFT Effects in Non-Resonant Dijet Events

We investigate the bounds which can be placed on generic new-physics contributions to dijet production at the LHC using the framework of the Standard Model Effective Field Theory, deriving the first consistently-treated EFT bounds from non-resonant high-energy data. We recast an analysis searching for quark compositeness, equivalent to treating the SM with one higher-dimensional operator as a complete UV model. In order to reach consistent, model-independent EFT conclusions, it is necessary to truncate the EFT effects consistently at order $1/\Lambda^2$ and to include the possibility of multiple operators simultaneously contributing to the observables, neither of which has been done in previous searches of this nature. Furthermore, it is important to give consistent error estimates for the theoretical predictions of the signal model, particularly in the region of phase space where the probed energy is approaching the cutoff scale of the EFT. There are two linear combinations of operators which contribute to dijet production in the SMEFT with distinct angular behavior; we identify those linear combinations and determine the ability of LHC searches to constrain them simultaneously. Consistently treating the EFT generically leads to weakened bounds on new-physics parameters. These constraints will be a useful input to future global analyses in the SMEFT framework, and the techniques used here to consistently search for EFT effects are directly applicable to other off-resonance signals.Comment: v1: 23 pages, 9 figures, 3 tables; v2: references added, typos corrected, matches version published in JHE

Exclusive Radiative Decays of Z Bosons in QCD Factorization

We discuss the very rare, exclusive hadronic decays of a Z boson into a meson and a photon. The QCD factorization approach allows to organize the decay amplitude as an expansion in powers of $\Lambda_{\rm QCD}/m_Z\,$, where the leading terms contain convolutions of perturbatively calculable hard functions with the leading-twist light-cone distribution amplitudes of the meson. We find that power corrections to these leading terms are negligible since they are suppressed by the small ratio $(\Lambda_{\rm QCD}/m_Z)^2\,$. Renormalization-group effects play a crucial role as they render our theoretical predictions less sensitive to the hadronic input parameters which are currently not known very precisely. Thus, measurements of the decays $Z\to M\gamma$ at the LHC or a future lepton collider provide a theoretically very clean way to test the QCD factorization approach. The special case where $M=\eta^({}'{}^)$ is complicated by the fact that the decay amplitude receives an additional contribution where the meson is formed from a two-gluon state. The corresponding branching ratios are very sensitive to the hadronic parameters describing the $\eta-\eta'$ system. Future measurements of these decays could yield interesting information about these parameters and the gluon distribution amplitude.Comment: 6 pages, 3 figures, 1 table, contribution to the proceedings of the 38th International Conference on High Energy Physics, 3-10 August 2016, Chicago, US

IRIS: A new tool for suicide risk assessment

Na introdução os autores procedem a uma revisão histórica e conceptual dos instrumentos psicométricos que têm como objectivo a avaliação do risco de suicídio em indivíduos que apenas verbalizam ideação suicida. Nas secções seguintes é apresentado todo o processo de desenvolvimento do IRIS (Índice de Risco de Suicídio) - um novo índice com o mesmo objectivo de avaliação mas construído utilizando metodologias que proporcionam avanços qualitativos em relação aos índices existentes, bem como uma melhor adequação a contingências e características da realidade portuguesa. The introduction contains a historical and conceptual review of psychometric tools that aim at assessing the risk of suicide in individuals presenting suicidal ideation. In the following sections the whole process of development of IRIS (“Índice de Risco de Suicídio” – Suicide Risk Index) is presented - a new tool with the same objective but built using methods that provide qualitative advances over existing indexes, while better accounting for the contingencies and characteristics of the Portuguese reality

(R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine: an N-aryl pyrrolidine ligand for enantioselective transfer hydrogenation

The N-aryl pyrrolidine diphosphine (R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine was obtained from natural tartaric acid. Contrary to our preliminary expectations, this new chiral ligand proved to be less selective than the corresponding N-benzyl pyrrolidine diphosphine. An attempted explanation of the observed behaviour based on the stereochemistry of the ligand as shown by X-ray crystallography is presented.http://www.sciencedirect.com/science/article/B6TGM-42G6XGY-8/1/25fa9c4e0f48edebc992db1e0b302bf

Consistent Searches for SMEFT Effects in Non-Resonant Dilepton Events

Employing the framework of the Standard Model Effective Field Theory, we perform a detailed reinterpretation of measurements of the Weinberg angle in dilepton production as a search for new-physics effects. We truncate our signal prediction at order $1/\Lambda^2$, where $\Lambda$ denotes the new-physics mass scale, and introduce a theory error to account for unknown contributions of order $1/\Lambda^4$. Two linear combinations of four-fermion operators with distinct angular behavior contribute to dilepton production with growing impact at high energies. We define suitable angular observables and derive bounds on those two linear combinations using data from the Tevatron and the LHC. We find that the current data is able to constrain interesting regions of parameter space, with important contributions at lower cutoff scales from the Tevatron, and that the future LHC data will eventually be able to simultaneously constrain both independent linear combinations which contribute to dilepton production.Comment: 11 pages, 4 figures v2: updated to match version accepted for publicatio