Jet Substructure Without Trees

We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods.Comment: 22 pages, 16 figures, version accepted by JHE

Desempenho reprodutivo de vacas leiteiras sem raça definida submetidas a diferentes protocolos de indução de estro

Avaliou-se a eficiência de diferentes protocolos (CIDR, CIDR+GnRH e CIDR+eCG) sobre a indução do estro, prenhez e fertilidade de vacas leiteiras sem raça definida entre 45 e 60 dias de paridas. As vacas (n = 150) foram aleatoriamente distribuídas em quatro grupos. As do grupo CIDR (n  = 45) receberam um dispositivo intravaginal com 1,9 g de progesterona durante 11 dias e uma injeção por via intramuscular (i.m.) contendo 4 mg de benzoato de estradiol. As do grupo CIDR+GnRH (n = 30) receberam o dispositivo e  500 µg de GnRH i.m. As do grupo CIDR+eCG (n = 30) receberam o dispositivo e 500 UI de eCG i.m. Nas fêmeas do grupo Controle (n = 45), o estro foi observado durante 30 dias. A ocorrência de estro no grupo tratado com CIDR foi maior do que a observada no grupo Controle (P < 0,05), não havendo diferença (P > 0,05) entre os demais grupos. Foi verificada uma menor taxa de prenhez (P < 0,05) no grupo tratado com CIDR+GnRH em relação ao grupo Controle, não havendo diferença (P > 0,05) entre os demais grupos. Quanto a fertilidade, não foi observada diferença (P > 0,05) entre os grupos. Os resultados permitem concluir que a utilização dos protocolos utilizados não é viável para aumentar o desempenho reprodutivo de fêmeas leiteiras entre o 45o e o 60o dia de prenhez.&nbsp

The mass area of jets

We introduce a new characteristic of jets called mass area. It is defined so as to measure the susceptibility of the jet's mass to contamination from soft background. The mass area is a close relative of the recently introduced catchment area of jets. We define it also in two variants: passive and active. As a preparatory step, we generalise the results for passive and active areas of two-particle jets to the case where the two constituent particles have arbitrary transverse momenta. As a main part of our study, we use the mass area to analyse a range of modern jet algorithms acting on simple one and two-particle systems. We find a whole variety of behaviours of passive and active mass areas depending on the algorithm, relative hardness of particles or their separation. We also study mass areas of jets from Monte Carlo simulations as well as give an example of how the concept of mass area can be used to correct jets for contamination from pileup. Our results show that the information provided by the mass area can be very useful in a range of jet-based analyses.Comment: 36 pages, 12 figures; v2: improved quality of two plots, added entry in acknowledgments, nicer form of formulae in appendix A; v3: added section with MC study and pileup correction, version accepted by JHE

Identifying Boosted Objects with N-subjettiness

We introduce a new jet shape -- N-subjettiness -- designed to identify boosted hadronically-decaying objects like electroweak bosons and top quarks. Combined with a jet invariant mass cut, N-subjettiness is an effective discriminating variable for tagging boosted objects and rejecting the background of QCD jets with large invariant mass. In efficiency studies of boosted W bosons and top quarks, we find tagging efficiencies of 30% are achievable with fake rates of 1%. We also consider the discovery potential for new heavy resonances that decay to pairs of boosted objects, and find significant improvements are possible using N-subjettiness. In this way, N-subjettiness combines the advantages of jet shapes with the discriminating power seen in previous jet substructure algorithms.Comment: 26 pages, 26 figures, 2 tables; v2: references added; v3: discussion of results extende

An agent-based approach to spatial epidemics through GIS

This study introduces a bottom up approach to model the complex phenomena involving the spread of epidemics in a human population with spatial dependence. To pursue this, several concepts and technologies are assembled together such as Artificial Life, Complex Networks, and Geographical Information Systems (GIS). At the beginning of this project, a Cellular Automata (CA) model was developed, but that was replaced later by an agent-based model (ABM) as it seemed more ad equate for this particular context the main target was relaxing the assumptions of homogeneous space and of random mixing of individuals. The model is split into a movement model and an infection model. The movement model uses network concepts and combines different ranges of movements to emulate the movement of individuals in human populations. The infection model is based on a classic SEIR ( Susceptible- Latent-Infectious-Removed) model and it is flexible enough to accommodate different infectious diseases. Both these models are probabilistic. The model was implemented from scratch in C++, and developed within a Geographical Information Systems (GIS) environment that provides functions for the display and analysis of geographic informa tion. Finally, some spatial vaccination strategies were implemented which illustrates a useful purpose of this kind of simulation model, for instance for aiding in the definition of health policies. The documented simulations cover the sensitivity analysis of the parameters of the movement and infection model, and there are also simulations to reproduce a mumps outbreak that occurred in Portugal between 1993 and 1996. In this way, an application of the epidemic model was illustrated for a case study, that enabled an analysis and interpretation of the model efficiency

Calreticulin is a secreted BMP antagonist, expressed in Hensen's node during neural induction

Hensen's node is the “organizer” of the avian and mammalian early embryo. It has many functions, including neural induction and patterning of the ectoderm and mesoderm. Some of the signals responsible for these activities are known but these do not explain the full complexity of organizer activity. Here we undertake a functional screen to discover new secreted factors expressed by the node at this time of development. Using a Signal Sequence Trap in yeast, we identify several candidates. Here we focus on Calreticulin. We show that in addition to its known functions in intracellular Calcium regulation and protein folding, Calreticulin is secreted, it can bind to BMP4 and act as a BMP antagonist in vivo and in vitro. Calreticulin is not sufficient to account for all organizer functions but may contribute to the complexity of its activity

Heavy Squarks at the LHC

The LHC, with its seven-fold increase in energy over the Tevatron, is capable of probing regions of SUSY parameter space exhibiting qualitatively new collider phenomenology. Here we investigate one such region in which first generation squarks are very heavy compared to the other superpartners. We find that the production of these squarks, which is dominantly associative, only becomes rate-limited at mSquark > 4(5) TeV for L~10(100) fb-1. However, discovery of this scenario is complicated because heavy squarks decay primarily into a jet and boosted gluino, yielding a dijet-like topology with missing energy (MET) pointing along the direction of the second hardest jet. The result is that many signal events are removed by standard jet/MET anti-alignment cuts designed to guard against jet mismeasurement errors. We suggest replacing these anti-alignment cuts with a measurement of jet substructure that can significantly extend the reach of this channel while still removing much of the background. We study a selection of benchmark points in detail, demonstrating that mSquark= 4(5) TeV first generation squarks can be discovered at the LHC with L~10(100)fb-1

Non-global logarithms and jet algorithms in high-pT jet shapes

We consider jet-shape observables of the type proposed recently, where the shapes of one or more high-pT jets, produced in a multi-jet event with definite jet multiplicity, may be measured leaving other jets in the event unmeasured. We point out the structure of the full next-to-leading logarithmic resummation specifically including resummation of non-global logarithms in the leading-Nc limit and emphasising their properties. We also point out differences between jet algorithms in the context of soft gluon resummation for such observables.Comment: 22 pages, 4 figures. Title and a few words changed. Several typos corrected. Version accepted by JHE

Diboson-Jets and the Search for Resonant Zh Production

New particles at the TeV-scale may have sizeable decay rates into boosted Higgs bosons or other heavy scalars. Here, we investigate the possibility of identifying such processes when the Higgs/scalar subsequently decays into a pair of W bosons, constituting a highly distinctive "diboson-jet." These can appear as a simple dilepton (plus MET) configuration, as a two-prong jet with an embedded lepton, or as a four-prong jet. We study jet substructure methods to discriminate these objects from their dominant backgrounds. We then demonstrate the use of these techniques in the search for a heavy spin-one Z' boson, such as may arise from strong dynamics or an extended gauge sector, utilizing the decay chain Z' -> Zh -> Z(WW^(*)). We find that modes with multiple boosted hadronic Zs and Ws tend to offer the best prospects for the highest accessible masses. For 100/fb luminosity at the 14 TeV LHC, Z' decays into a standard 125 GeV Higgs can be observed with 5-sigma significance for masses of 1.5-2.5 TeV for a range of models. For a 200 GeV Higgs (requiring nonstandard couplings, such as fermiophobic), the reach may improve to up to 2.5-3.0 TeV.Comment: 23 pages plus appendices, 9 figure