P. Ferrario

Heavy colored resonances in top-antitop + jet at the LHC

The LHC is the perfect environment for the study of new physics in the top quark sector. We study the possibility of detecting signals of heavy color-octet vector resonances, through the charge asymmetry, in

Constraining heavy colored resonances from top-antitop quark events

t\bar t + {\text{jet}}

Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders

events. Besides contributions with the

First proof of topological signature in high pressure xenon gas with electroluminescence amplification

t\bar t

Present Status and Future Perspectives of the NEXT Experiment

pair in a color-singlet state, the asymmetry gets also contributions which are proportional to the color factor fabc2. This process is particularly interesting for extra-dimensional models, where the inclusive charge asymmetry generated by Kaluza-Klein excitations of the gluon vanishes at the tree level. We find that the statistical significance for the measurement f such an asymmetry is sizable for different values of the coupling constants and already at low energies.

Compact Multigluonic Scattering Amplitudes with Heavy Scalars and Fermions

We thank the CERN TH TOP09 Institute, where this work was initiated, for hospitality and for many useful discussions. The work of P.F. is supported by the Consejo Superior de Investigaciones Cient´ificas (CSIC). This work is also supported by the Ministerio de Ciencia e Innovacion under Grant No. FPA2007-60323, by CPAN(Grant No. CSD2007-00042), by the Generalitat Valenciana under Grant No.PROMETEO/2008/069, and by the European Commission MRTN FLAVIAnet under Contract No. MRTN-CT-2006-035482.

Sensitivity of NEXT-100 to neutrinoless double beta decay

Several models predict the existence of heavy colored resonances decaying to top quarks in the TeV energy range that might be discovered at the CERN LHC. In some of those models, moreover, a sizable charge asymmetry of top versus antitop quarks might be generated. The detection of these exotic resonances, however, requires selecting data samples where the top and the antitop quarks are highly boosted, which is experimentally very challenging. We asses that the measurement of the top quark charge asymmetry at the LHC is very sensitive to the existence of excited states of the gluon with axial-vector couplings to quarks. We use a toy model with general flavor independent couplings, and show that a signal can be detected with relatively not too energetic top and antitop quarks. We also compare the results with the asymmetry predicted by QCD, and show that its highest statistical significance is achieved with data samples of top-antitop quark pairs of low invariant masses.

Background rejection in NEXT using deep neural networks

A bstractThe NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. One of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to Qββ. This paper presents the first demonstration that the topology provides extra handles to reject background events using data obtained with the NEXT-DEMO prototype.Single electrons resulting from the interactions of 22Na 1275 keV gammas and electronpositron pairs produced by conversions of gammas from the 228Th decay chain were used to represent the background and the signal in a double beta decay. These data were used to develop algorithms for the reconstruction of tracks and the identification of the energy deposited at the end-points, providing an extra background rejection factor of 24.3 ± 1.4 (stat.)%, while maintaining an efficiency of 66.7 ± 1.% for signal events.

Charge asymmetries of top quarks: A window to new physics at hadron colliders

NEXT is an experiment dedicated to neutrinoless double beta decay searches in xenon. The detector is a TPC, holding 100 kg of high-pressure xenon enriched in the 136Xe isotope. It is under construction in the Laboratorio Subterraneo de Canfranc in Spain, and it will begin operations in 2015. The NEXT detector concept provides an energy resolutionbetter than 1% FWHM and a topological signal that can be used to reduce the background. Furthermore, the NEXT technology can be extrapolated to a 1 ton-scale experiment.

Heavy colored resonances in t t-bar + jet at the LHC

Combining the Berends-Giele and on-shell recursion relations we obtain an extremely compact expression for the scattering amplitude of a complex massive scalar-antiscalar pair and an arbitrary number of positive helicity gluons. This is one of the basic building blocks for constructing other helicity configurations from recursion relations. We also show explicitly that the scattering amplitude of massive fermions to gluons, all with positive helicity, is proportional to the scalar one, confirming in this way the recently advocated SUSY-like Ward identities relating both amplitudes.