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Abstract
Introduction
Conclusion
References

LHC bounds on colored scalars

Profile image of Antonio PichAntonio Pich

Physical Review D

https://doi.org/10.1103/PHYSREVD.100.115042
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20 pages

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Abstract

We analyze the constraints on coloured scalar bosons imposed by the current LHC data at √ s = 13 TeV. Specifically, we consider an additional electroweak doublet of colouroctet scalars, satisfying the principle of minimal flavour violation in order to fulfill the stringent experimental limits on flavour-changing neutral currents. We demonstrate that coloured scalars with masses below 800 GeV are already excluded, provided they are not fermiophobic.

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Elaine Fortes

2013

In this work we present an analysis of flavor violating effects mediated by color sextet scalars, which arise naturally in left-right symmetric gauge theories based on SU(2)_L \times SU(2)_R \times SU(4)_C group. The sextets, denoted here by \Delta_{dd}, Delta_{ud} and \Delta_{uu}, couple to right--handed quarks. We delineate the constraints on these couplings arising from meson--anti-meson transitions and flavor changing weak decays. The sextet \Delta_{uu} mediates D^{0}-\bar{D}^{0} mixing via tree-level and box diagrams, and also mediates D --> K pi, pi pi decays. The sextets \Delta_{ud} and \Delta_{dd} mediate B_{d}^{0}-\bar{B}_{d}^{0}, B_{s}^{0}-\bar{B}_{s}^{0} and K^{0}-\bar{K}^{0} mixings as well as rare B and D meson decays. Our analysis shows that for coupling strengths of order 10^{-2}, the current experimental data requires the mass of these color sextets to exceed several TeV. These bounds are stronger than those obtained from direct LHC searches.

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Bounds on flavor gauge bosons from precision electroweak data
Gustavo Burdman

Physical review, 2000

Gauged flavor symmetries at low energies have been proposed in models of dynamical electroweak symmetry breaking and fermion mass generation. The massive flavor gauge bosons give rise to corrections to precisely measured electroweak quantities. We perform a fit to the collider electroweak data and place indirect limits on such new physics. In particular we study several models from the literature: universal coloron; chiral top color; chiral quark family symmetry; SU(9) and SU(12) chiral flavor symmetry. The 95% exclusion limits on the mass of the heavy gauge bosons for these models, at their critical coupling for chiral symmetry breaking, typically lie between 1-3 TeV. We discuss the robustness of these bounds with respect to changes in higgs mass, b-quark asymmetry data, the SLD left right asymmetry data, or additional new physics.

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Color octet scalar bound states at the LHC
Thomas Mehen

Physical Review D, 2009

One possible extension of the Standard Model scalar sector includes SU (2) L doublet scalars that are color octets rather than singlets. We focus on models in which the couplings to fermions are consistent with the principle of minimal flavor violation (MFV), in which case these color octet scalars couple most strongly to the third generation of quarks. When the Yukawa coupling of color octet scalars to Standard Model fermions is less than unity, these states can live long enough to bind into color-singlet spin-0 hadrons, which we call octetonia. In this paper, we consider the phenomenology of octetonia at the Large Hadron Collider (LHC). Predictions for their production via gluon-gluon fusion and their two-body decays into Standard Model gauge bosons, Higgs bosons, andtt are presented.

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Colorless top partners, a 125 GeV Higgs boson, and the limits on naturalness
Gustavo Burdman

Physical Review D, 2015

Theories of physics beyond the Standard Model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs to the top quark. With extensions of the Standard Model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the Standard Model particles. This results in corrections to the Higgs production and decay rates that can be detected at the Large Hadron Collider (LHC) provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the Mirror Twin Higgs, Folded Supersymmetry, and the Quirky Little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with 3000 fb −1 of data at 14 TeV.

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Pair production of color-octet scalars at the LHC
Thomas Mehen

Physical Review D, 2010

Heavy colored scalar particles, which exist in many models of new physics, can be pair produced at the Large Hadron Collider (LHC) via gluon-gluon fusion and possibly form quarkonium-like bound states. If the scalars are also charged under the electroweak gauge group, these bound states can then decay into electroweak bosons. This yields a resonant cross section for final states such as γγ that can exceed Standard Model backgrounds. This paper studies this process in the Manohar-Wise model of color-octet scalars (COS). Important threshold logarithms and final state Coulomb-like QCD interactions are resummed using effective field theory. We compute the resummed cross section for gluon-gluon fusion to COS pairs at the LHC as well as the resonant cross section for octetonium decaying to γγ. The latter cross section exceeds the Standard Model di-photon cross section when the COS mass is less than 500 (350) GeV for √ s = 14 (7) TeV. Nonobservation of resonances below these energies can significantly improve existing bounds on COS masses.

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Cited by

Color-octet scalar decays to a gluon and an electroweak gauge boson in the Manohar-Wise model
Alper Hayreter

Physical Review D

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