Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 1807.05225

Phenomenology of extra quarks at the LHC

Hugo Prager
View original source ↗Read source document ↗Export metadata ↓

Abstract

We study in a model independent way models of new Physics featuring extra quarks (XQs). These XQs are predicted by extensions of the Standard Model (SM) but have never been observed yet even though many searches have been designed to find them at the LHC. After an introduction about the SM and the LHC, we present the main properties of these XQs and a model independent parametrisation that can be used to describe their phenomenology with generic hypotheses about their mixing with SM quarks, both in the case of XQ coupling with SM bosons and with Dark Matter (DM) candidates. In these cases we study the offshellness effects in pair-production and decay and show that if the Narrow-Width Approximation (NWA) is a good approximation of the full result in the small width over mass ratio limit, sizeable differences occur when the XQ width becomes larger. The conclusion of our analysis is that even though the small width assumption is always conservative it is not possible to trivially rescale the mass bounds obtained considering processes of pair production and decay in the NWA to determine constraints for XQs with large widths. We also study the role of interference in the process of pair production of new heavy XQs decaying to SM particles and show that in the NWA the interference contribution can be described by considering a parameter which contains only the relevant couplings and the scalar part of the propagators of the new quarks, both at the cross section level and at the distribution level. Finally, we study how various SUSY searches perform for our simplified model with XQs decaying to DM. We show that the bound for XQs can be obtained from the SUSY ones just by rescaling the exclusion with the XQ cross section.

Explore related subjects

hep-ph

Keep this discovery

BibTeXRIS

Hugo Prager. 2018-07-13. Phenomenology of extra quarks at the LHC. https://arxiv.org/abs/1807.05225

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Axionic Wormholes in Metric-Affine Gravity

The axion is a promising candidate for solving the strong CP problem. To solve this problem, the global U(1) symmetry must be preserved to a high degree of accuracy. However, it is well known that global symmetries are explicitly violated by quantum gravity effects, giving rise to what is referred to as the axion quality problem. In this paper, we investigate axionic wormholes as a source of explicit U(1) violation in Metric-Affine Gravity. This framework allows for spacetime torsion and non-metricity, which accommodate additional curvature-like and topological terms, such as the Holst and Nieh--Yan terms, that are absent from the metric and Palatini formalisms. We show that non-minimal couplings to these terms modify the wormhole dynamics and enhance the Euclidean wormhole action, thereby alleviating the axion quality problem. We also find that the viable parameter space is enlarged when two of these couplings are simultaneously present. We further identify representative parameter regions where the alleviation of the axion quality problem is compatible with inflationary constraints.

hep-ph↗
arXiv2026

Qubit-Qutrit Quantum Tomography of hadronic $\Lambda\phi$ and $\Lambda K^{\ast 0}$ systems

Quantum-information observables have emerged in recent years as new tools in nuclear and particle physics, from entanglement in top-quark pairs to spin correlations in $\Lambda\bar{\Lambda}$ production. Extending these studies to unequal-spin hadronic final states poses a fundamental challenge: the $6\times6$ density matrix of a qubit-qutrit system contains 35 independent spin parameters, but the decays of $\Lambda V$ pairs, with $V=\phi$ or $K^{*0}$, provide access to only 23 due to the hidden vector polarization from the strong decay. In this Letter, we formulate a qubit-qutrit quantum tomography (QQQT) technique for these spin-$\tfrac{1}{2}\otimes1$ systems and establish exact criteria for entanglement certification from the \textit{incomplete} density matrix. Compared with the $\Lambda\bar{\Lambda}$ system, QQQT of $\Lambda\phi$ and $\Lambda K^{*0}$ provides a new probe of nonperturbative QCD hadronization, enabling a direct comparison of the spin evolution of entangled quark pairs produced from the vacuum as they hadronize into a baryon or a vector meson.

hep-ph↗
arXiv2026

Twist decomposition of exclusive heavy meson production cross sections

We study the twist decomposition of the total cross sections for exclusive heavy vector meson electroproduction and photoproduction in the $\gamma^\ast p$ processes, within the leading logarithmic $1/x$ BFKL formalism. The Mellin transforms of the impact factors of the vector meson are calculated. We show that the higher twist contributions are strongly suppressed in the low-$x$ kinematical regime. Possible enhancement of the higher twists effects for nuclei targets is discussed.

hep-ph↗