R. A. Coimbra

SCANNERS: constraining the phase diagram of a complex scalar singlet at the LHC

We present the first version of a new tool to scan the parameter space of generic scalar potentials, ScannerS (Coimbra et al., ScannerS project., 2013). The main goal of ScannerS is to help distinguish between different patterns of symmetry breaking for each scalar potential. In this work we use it to investigate the possibility of excluding regions of the phase diagram of several versions of a complex singlet extension of the Standard Model, with future LHC results. We find that if another scalar is found, one can exclude a phase with a dark matter candidate in definite regions of the parameter space, while predicting whether a third scalar to be found must be lighter or heavier. The first version of the code is publicly available and contains various generic core routines for tree level vacuum stability analysis, as well as implementations of collider bounds, dark matter constraints, electroweak precision constraints and tree level unitarity.

On the kinetics and energetics of one-electron oxidation of 1,3,5-triazines

One-electron oxidation of 1,3,5-triazines is observed with both excited uranyl ion (*UO2(2+)) and sulfate radical anion (SO4.-) in aqueous solution, but not with Tl2+, indicating that the standard reduction potentials E degree of 1,3,5-triazine radical cations are = 2.3 +/- 0.1 V vs. NHE, consistent with theoretical calculations; this suggests that if triazines inhibit electron transfer during photosynthesis, they would need to act on the reductive part of the electron transport chain.

Dimension six FCNC operators and top production at the LHC

R.A. Coimbra , P.M. Ferreira , R.B. Guedes , O. Oliveira , A. Onofre , R. Santos ∗∗ and Miguel Won †† 1 LIPDepartamento de F́ısica, Universidade de Coimbra, 3004-516 Coimbra, Portugal; 2 Centro de F́ısica Computacional, Universidade de Coimbra, 3004-516 Coimbra, Portugal; 3 Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emı́dio Navarro 1, 1959-007 Lisboa, Portugal; 4 Centro de F́ısica Teórica e Computacional, Faculdade de Ciências, Universidade de Lisboa, Avenida Professor Gama Pinto, 2, 1649-003 Lisboa, Portugal; 5 NExT Institute and School of Physics and Astronomy, University of Southampton Highfield, Southampton SO17 1BJ, United Kingdom

MEtop—a generator for single top production via FCNC interactions

We present a generator for single top-quark production via flavour-changing neutral currents. The MEtop event generator allows for Next-to-Leading-Order direct top production pp→t and Leading-Order production of several other single top processes. Axa0few packages with definite sets of dimension six operators are available. We discuss how to improve the bounds on the effective operators and how well new physics can be probed with each set of independent dimension six operators.

Dimension six flavor changing neutral current operators and top-quark production at the LHC

In this work we calculate the effects of the electroweak flavor changing neutral currents dimension six effective operators on single-top production at the LHC. These results are then combined with previous ones we have obtained for the strong sector. This allow us, for the first time, to perform a combined analysis of flavor changing neutral currents in top production with all contributing dimension six operators. Finally, we study the feasibility of their observation and characterization both at the Tevatron and at the LHC.

Heavy quarkonia from classical SU(3) Yang-Mills configurations

Abstract.A generalized Cho-Faddeev-Niemi ansatz for SU(3) Yang-Mills is investigated. The corresponding classical field equations are solved for its simplest parametrization. From these solutions it is possible to define a confining non-relativistic central potential used to study heavy quarkonia. The associated spectra reproduces the experimental spectra with an error of less than 3% for charmonium and 1% for bottomonium. Moreover, the recently discovered new charmonium states can be accomodate in the spectra, keeping the same level of precision. The leptonic widths show good agreement with the recent measurements. The charmonium and bottomonium E1 electromagnetic transitions widths are computed and compared with the experimental values.

Angiogenic Factors produced by Hypoxic Cells are a leading driver of Anastomoses in Sprouting Angiogenesis–a computational study

Angiogenesis - the growth of new blood vessels from a pre-existing vasculature - is key in both physiological processes and on several pathological scenarios such as cancer progression or diabetic retinopathy. For the new vascular networks to be functional, it is required that the growing sprouts merge either with an existing functional mature vessel or with another growing sprout. This process is called anastomosis. We present a systematic 2D and 3D computational study of vessel growth in a tissue to address the capability of angiogenic factor gradients to drive anastomosis formation. We consider that these growth factors are produced only by tissue cells in hypoxia, i.e. until nearby vessels merge and become capable of carrying blood and irrigating their vicinity. We demonstrate that this increased production of angiogenic factors by hypoxic cells is able to promote vessel anastomoses events in both 2D and 3D. The simulations also verify that the morphology of these networks has an increased resilience toward variations in the endothelial cell’s proliferation and chemotactic response. The distribution of tissue cells and the concentration of the growth factors they produce are the major factors in determining the final morphology of the network.

MEtop – a top FCNC event generator

In this work we present a new Monte Carlo generator for Direct top and Single top production via flavour-changing neutral currents (FCNC). This new tool calculates the cross section and generates events with Next-to-Leading order precision for the Direct top process and Leading-Order precision for all other FCNC single top processes. A set of independent dimension six FCNC operators has been implemented – including four-fermion operators – where at least one top-quark is present in the interaction.

Charmonium and Bottomonium from Classical SU(3) Gauge Configurations

The charmonium and bottomonium spectra computed from a potential defined from a single gauge configuration, obtained from solving the classical field equations, is discussed. The theoretical spectra shows good agreement with the measured states.A discussion of possible interpretations, within the same non‐relativistic potential model, for the new charmonia states X(3872), χc1(2P) and Y(4260) is performed. In particular, we give predictions for electromagnetic E1 transitions for various scenarios.