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R. S. Chivukula

Publications and source records attributed to R. S. Chivukula.

At least 19 recordsLinked to original sources
arXiv2016

Les Houches 2015: Physics at TeV colliders - new physics working group report

We present the activities of the 'New Physics' working group for the 'Physics at TeV Colliders' workshop (Les Houches, France, 1-19 June, 2015). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments. Important signatures for searches for natural new physics at the LHC and new assessments of the interplay between direct dark matter searches and the LHC are also considered.

hep-ph↗
arXiv2012

Les Houches 2011: Physics at TeV Colliders New Physics Working Group Report

We present the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our report includes new agreements on formats for interfaces between computational tools, new tool developments, important signatures for searches at the LHC, recommendations for presentation of LHC search results, as well as additional phenomenological studies.

hep-ph↗
arXiv2010

The Top Triangle Moose

We introduce a deconstructed model that incorporates both Higgsless and top-color mechanisms. The model alleviates the typical tension in Higgsless models between obtaining the correct top quark mass and keeping delta-rho small. It does so by singling out the top quark mass generation as arising from a Yukawa coupling to an effective top-Higgs which develops a small vacuum expectation value, while electroweak symmetry breaking results largely from a Higgsless mechanism. As a result, the heavy partners of the SM fermions can be light enough to be seen at the LHC.

hep-ph↗
arXiv2008

New Physics at the LHC: A Les Houches Report. Physics at Tev Colliders 2007 -- New Physics Working Group

We present a collection of signatures for physics beyond the standard model that need to be explored at the LHC. The signatures are organized according to the experimental objects that appear in the final state, and in particular the number of high pT leptons. Our report, which includes brief experimental and theoretical reviews as well as original results, summarizes the activities of the "New Physics'' working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 11-29 June, 2007).

hep-ph↗
arXiv2003

The structure of electroweak corrections due to extended gauge symmetries

This paper studies models with extended electroweak gauge sectors of the form SU(2) x SU(2) x U(1) x [SU(2) or U(1)]. We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group.

hep-ph↗
arXiv2003

Flavor Constraints on Theory Space

Composite Higgs models based on the chiral symmetries of ``theory space'' can produce Higgs bosons with masses of order 100 GeV from underlying strong dynamics at scales up to 10 TeV without fine tuning. This talk argues that flavor-violating interactions generically arising from underlying flavor dynamics constrain the Higgs compositeness scale to be at least 75 GeV, implying that significant fine-tuning is required. Bounds from CP violation and weak isospin violation are also discussed.

hep-ph↗
arXiv2002

Electroweak Limits on Non-Universal Z' Bosons

Many types of physics beyond the standard model include an extended electroweak gauge group. If these extensions are associated with flavor symmetry breaking, the gauge interactions will not be flavor-universal. In this note we update the bounds placed by electroweak data on the existence of flavor non-universal extensions to the standard model in the context of topcolor assisted technicolor (TC2), noncommuting extended technicolor (NCETC), and the ununified standard model (UUM). In the first two cases the extended gauge interactions couple to the third generation fermions differently than to the light fermions, while in the ununified standard model the gauge interactions couple differently to quarks and leptons. The extra SU(2) triplet of gauge bosons in NCETC and UUM models must be heavier than about 3 TeV, while the extra Z boson in TC2 models must be heavier than about 1 TeV.

hep-ph↗
arXiv1997

General constraints on light resonances in a strongly coupled symmetry breaking sector

In this paper we consider the information that can be obtained about a strongly-interacting symmetry breaking sector from precision measurements of four-fermion processes at LEP2 or a (500 GeV) NLC . Using a ``Z-peak'' subtracted approach to describe four-fermion processes, we show that measurements of the cross section for muon production, the related forward-backward asymmetry, and the total cross section for the production of hadrons (except $t$'s) can place constraints on (or measure the effectsof) the lightest vector or axial resonances present in a strong symmetry breaking sector. We estimate that such effects will be visible at LEP2 for resonances of masses up to approximately 350 GeV, and at a 500 GeV NLC for resonances of masses up to approximately 800 GeV. Multiscale models, for example, predict the presence of light vector and axial mesons in this mass range and their effects could be probed by these measurements.

hep-ph↗
arXiv1997

Strong Coupling Electroweak Symmetry Breaking

We review models of electroweak symmetry breaking due to new strong interactions at the TeV energy scale and discuss the prospects for their experimental tests. We emphasize the direct observation of the new interactions through high-energy scattering of vector bosons. We also discuss indirect probes of the new interactions and exotic particles predicted by specific theoretical models. [Working group summary report from the Snowmass `96 summer study, to appear in the proceedings.]

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arXiv1997

Flavor Physics and the Triviality Bound on the Higgs Mass

The triviality of the scalar sector of the standard one-doublet Higgs model implies that this model is only an effective low-energy theory valid below some cut-off scale $Λ$. The underlying high-energy theory must include flavor dynamics at a scale of order $Λ$ or greater in order to give rise to the different Yukawa couplings of the Higgs to ordinary fermions. This flavor dynamics will generically produce flavor-changing neutral currents and non-universal corrections to Z -> b b-bar. We show that the experimental constraints on the neutral D-meson mass difference imply that $Λ$ must be greater than of order 21 TeV. We also discuss bounds on $Λ$ from the constraints on extra contributions to the K_L - K_S mass difference and to the coupling of the Z boson to b-quarks. For theories defined about the infrared-stable Gaussian fixed-point, we estimate that this lower bound on $Λ$ yields an upper bound of approximately 460 GeV on the Higgs boson's mass, independent of the regulator chosen to define the theory.

hep-ph↗
arXiv1997

Custodial Symmetry, Flavor Physics, and the Triviality Bound on the Higgs Mass

The triviality of the scalar sector of the standard one-doublet Higgs model implies that this model is only an effective low-energy theory valid below some cut-off scale Lambda. We show that the experimental constraint on the amount of custodial symmetry violation implies that the scale Lambda must be greater than of order 7.5 TeV. The underlying high-energy theory must also include flavor dynamics at a scale of order Lambda or greater in order to give rise to the different Yukawa couplings of the Higgs to ordinary fermions. This flavor dynamics will generically produce flavor-changing neutral currents. We show that the experimental constraints on the neutral D-meson mass difference imply that Lambda must be greater than of order 21 TeV. For theories defined about the infrared-stable Gaussian fixed-point, we estimate that this lower bound on Lambda yields an upper bound of approximately 460 GeV on the Higgs boson's mass, independent of the regulator chosen to define the theory. We also show that some regulator schemes, such as higher-derivative regulators, used to define the theory about a different fixed-point are particularly dangerous because an infinite number of custodial-isospin-violating operators become relevant.

hep-ph↗
arXiv1996

Custodial Symmetry and the Triviality Bound on the Higgs Mass

The triviality of the scalar sector of the standard one-doublet Higgs model implies that it is only an effective low-energy theory valid below some cut-off scale $Λ$. In this note we show that the experimental constraint on the amount of custodial symmetry violation, $|Δρ_* | = α|T | \le 0.4\%$, implies that the scale $Λ$ must be greater than of order 7.5 TeV. For theories defined about the infrared-stable Gaussian fixed-point, we estimate that this lower bound on $Λ$ yields an upper bound of approximately 550 GeV on the Higgs boson's mass, independent of the regulator chosen to define the theory. We also show that some regulator schemes, such as higher-derivative regulators, used to define the theory about a different fixed-point are particularly dangerous because an infinite number of custodial-isospin-violating operators become relevant.

hep-ph↗
arXiv1996

Precision Electroweak Constraints on Top-Color Assisted Technicolor

Using precision electroweak data, we put limits on ``natural'' top-color assisted technicolor models. Generically the new $U(1)$ gauge bosons in these models must have masses larger than roughly 2 TeV, although in certain (seemingly unrealistic) models the bound can be much lower.

hep-ph↗
arXiv1996

New Strong Interactons at the Tevatron ?

Recent results from CDF indicate that the inclusive cross section for jets with $E_T > 200$ GeV is significantly higher than that predicted by QCD. We describe here a simple flavor-universal variant of the ``coloron" model of Hill and Parke that can accommodate such a jet excess, and which is not in contradiction with other experimental data. As such, the model serves as a useful baseline with which to compare both the data and other models proposed to describe the jet excess. An interesting theoretical feature of the model is that if the global chiral symmetries of the quarks remain unbroken in the confining phase of the coloron interaction, it realizes the possibility that the ordinary quarks are composite particles.

hep-ph↗
arXiv1995

Direct Tests of Dynamical Electroweak Symmetry Breaking

We review the connection between $m_t$ and the $Zb\bar b$ vertex in ETC models and discuss the resulting experimental constraint on models with weak-singlet ETC bosons. We mention several recent efforts to bring ETC models into agreement with this constraint, and explore the most promising one (non-commuting ETC) in detail.

hep-ph↗
arXiv1995

Testing Extended Technicolor With $R_b$

We review the connection between $m_t$ and the $Zb\bar b$ vertex in ETC models and demonstrate the power of the resulting experimental constraint on models with weak-singlet ETC bosons. Some efforts to bring ETC models into agreement with experimental data on the $Zb\bar b$ vertex are mentioned, and the most promising one (non-commuting ETC) is discussed in detail.

hep-ph↗
arXiv1995

Limits on Non-Commuting Extended Technicolor

Using precision electroweak data, we put limits on non-commuting extended technicolor models. We conclude that these models are viable only if the ETC interactions are strong. Interestingly, these models predict a pattern of deviations from the standard model which can fit the data significantly better than the standard model does, even after taking into account the extra parameters involved.

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