Probing Supersymmetry With Third-Generation Cascade Decays

The chiral structure of supersymmetric particle couplings involving third generation Standard Model fermions depends on left-right squark and slepton mixings as well as gaugino-higgsino mixings. The shapes and intercorrelations of invariant mass distributions of a first or second generation lepton with bottoms and taus arising from adjacent branches of SUSY cascade decays are shown to be a sensitive probe of this chiral structure. All possible cascade decays that can give rise to such correlations within the MSSM are considered. For bottom-lepton correlations the distinctive structure of the invariant mass distributions distinguishes between decays originating from stop or sbottom squarks through either an intermediate chargino or neutralino. For decay through a chargino the spins of the stop and chargino are established by the form of the distribution. When the bottom charge is signed through soft muon tagging, the structure of the same-sign and opposite-sign invariant mass distributions depends on a set function of left-right and gaugino-higgsino mixings, as well as establishes the spins of all the superpartners in the sequential two-body cascade decay. Tau-lepton and tau-tau invariant mass distributions arising from MSSM cascade decays are likewise systematically considered with particular attention to their dependence on tau polarization. All possible tau-lepton and tau-tau distributions are plotted using a semi-analytic model for hadronic one-prong taus. Algorithms for fitting tau-tau and tau-lepton distributions to data are suggested.Comment: 35 pages, 17 .eps figure

A model independent spin analysis of fundamental particles using azimuthal asymmetries

Exploiting the azimuthal angle dependence of the density matrices we construct observables that directly measure the spin of a heavy unstable particle. A novelty of the approach is that the analysis of the azimuthal angle dependence in a frame other than the usual helicity frame offers an independent cross-check on the extraction of the spin. Moreover, in some instances when the transverse polarisation tensor of highest rank is vanishing, for an accidental or dynamical reason, the standard azimuthal asymmetries vanish and would lead to a measurement with a wrong spin assignment. In a frame such as the one we construct, the correct spin assignment would however still be possible. The method gives direct information about the spin of the particle under consideration and the same event sample can be used to identify the spins of each particle in a decay chain. A drawback of the method is that it is instrumental only when the momenta of the test particle can be reconstructed. However we hope that it might still be of use in situations with only partial reconstruction. We also derive the conditions on the production and decay mechanisms for the spins, and hence the polarisations, to be measured at a collider experiment. As an example for the use of the method we consider the simultaneous reconstruction, at the partonic level, of the spin of both the top and the $W$ in top pair production in $e^+ e^-$ in the semi-leptonic channel.Comment: 42 pages, 7 figures, 4 table

Ideal cardiovascular health and inflammation in European adolescents: The HELENA study

Background and aims Inflammation plays a key role in atherosclerosis and this process seems to appear in childhood. The ideal cardiovascular health index (ICHI) has been inversely related to atherosclerotic plaque in adults. However, evidence regarding inflammation and ICHI in adolescents is scarce. The aim is to assess the association between ICHI and inflammation in European adolescents. Methods and results As many as 543 adolescents (251 boys and 292 girls) from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study, a cross-sectional multi-center study including 9 European countries, were measured. C-reactive protein (CRP), complement factors C3 and C4, leptin and white blood cell counts were used to compute an inflammatory score. Multilevel linear models and multilevel logistic regression were used to assess the association between ICHI and inflammation controlling by covariates. Higher ICHI was associated with a lower inflammatory score, as well as with several individual components, both in boys and girls (p < 0.01). In addition, adolescents with at least 4 ideal components of the ICHI had significantly lower inflammatory score and lower levels of the study biomarkers, except CRP. Finally, the multilevel logistic regression showed that for every unit increase in the ICHI, the probability of having an inflammatory profile decreased by 28.1% in girls. Conclusion Results from this study suggest that a better ICHI is associated with a lower inflammatory profile already in adolescence. Improving these health behaviors, and health factors included in the ICHI, could play an important role in CVD prevention