Randall-Sundrum graviton spin determination using azimuthal angular dependence

Top-antitop pairs produced in the decay of a new heavy resonance will exhibit spin correlations that contain valuable coupling information. When the tops decay, these correlations imprint themselves on the angular patterns of the final quarks and leptons. While many approaches to the measurement of top spin correlations are known, the most common ones require detailed kinematic reconstructions and are insensitive to some important spin interference effects. In particular, spin-1 resonances with mostly-vector or mostly-axial couplings to top cannot be easily discriminated from one another without appealing to mass-suppressed effects or to more model-dependent interference with continuum Standard Model production. Here, we propose to probe the structure of a resonance's couplings to tops by measuring the azimuthal angles of the tops' decay products about the production axis. These angles exhibit modulations which are typically O(0.1-1), and which by themselves allow for discrimination of spin-0 from higher spins, measurement of the CP-phase for spin-0, and measurement of the vector/axial composition for spins 1 and 2. For relativistic tops, the azimuthal decay angles can be well-approximated without detailed knowledge of the tops' velocities, and appear to be robust against imperfect energy measurements and neutrino reconstructions. We illustrate this point in the highly challenging dileptonic decay mode, which also exhibits the largest modulations. We comment on the relevance of these observables for testing axigluon-like models that explain the top quark A F B anomaly at the Tevatron, through direct production at the LHC.

Section: Introductionsupporting

confidence: 68%

Discriminating top-antitop resonances using azimuthal decay correlations

Baumgart

Tweedie

2011

“…For details on azimuthal correlations in Higgs and new particle production we refer the reader to refs. [48][49][50][51][52][53][54][55][56][57][58][59][60][61], and to ref. [62] for correlations in the QCD production of heavy quark pairs (top or bottom) in association with two jets.…”

Section: Jhep10(2014)012mentioning

confidence: 99%

Compressed SUSY search at the 13 TeV LHC using kinematic correlations and structure of ISR jets

Mukhopadhyay

Nojiri

Yanagida

2014

Abstract:The LHC search for nearly degenerate gluinos and neutralinos, which can occur, for example, in SUSY axion models, is limited by the reduced missing transverse momentum and effective mass in the events. We propose the use of kinematic correlations between jets coming from initial state radiation (ISR) in gluino pair production events at the 13 TeV LHC. A significant improvement in the signal to background ratio is obtained for the highly compressed gluino-neutralino search, by using cuts on the rapidity and azimuthal angle separation between the pair of tagged jets with the highest transverse momenta. Furthermore, the distribution of the azimuthal angle difference between the tagged jets in thegg+jets process is found to be distinctly different from the dominant background process of Z+jets. We also find quark and gluon jet tagging methods to be useful in separating the signal, which contains a higher fraction of gluon initiated jets compared to the dominant backgrounds.

“…Techniques developed for supersymmetric particles or similar physics (e.g. [56][57][58][59][60][61][62][63][64][65]), are not applicable to stable particles. However, we can rely on simpler methods, since the event is fully reconstructible.…”

Section: Llcp Spin Measurementsmentioning

confidence: 99%

Stable colored particles R-SUSY relics or not?

Buckley

Echenard

Kahawala

et al. 2011

R-hadrons are only one of many possible stable colored states that the LHC might produce. All such particles would provide a spectacular, if somewhat unusual, signal at ATLAS and CMS. Produced in large numbers and leaving a characteristic signature throughout all layers of the detector, including the muon chamber, they could be straightforward to discover even with low luminosity. Though such long lived colored particles (LLCPs) can be realized in many extensions of the Standard Model, most analyses of their phenomenology have focused only on R-hadrons. In order to distinguish among the possibilities, fundamental quantum numbers of the new states must be measured. In this paper, we demonstrate how to identify the SU(3) C charge and spin of such new particles at the LHC.