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Register a new userTime to Go Beyond Triple-Gauge-Boson-Coupling Interpretation of $W$ Pair Production
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Zhengkang Zhang
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$W$ boson pair production processes at $e^+e^-$ and $pp$ colliders have been conventionally interpreted as measurements of $WWZ$ and $WWgamma$ triple gauge couplings (TGCs). Such interpretation is based on the assumption that new physics effects other than anomalous TGCs are negligible. While this TGC dominance assumption was well-motivated and useful at LEP2 thanks to precision electroweak constraints, it is already challenged by recent LHC data. In fact, contributions from anomalous $Z$ boson couplings that are allowed by electroweak precision data but neglected in LHC analyses, being enhanced at high energy, can even dominate over those from the anomalous TGCs considered. This limits the generality of the anomalous TGC constraints derived in current analyses, and necessitates extension of the analysis framework and change of physics interpretation. The issue will persist as we continue to explore the high energy frontier. We clarify and analyze the situation in the effective field theory framework, which provides a useful organizing principle for understanding Standard Model deviations in the high energy regime.
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We demonstrate that the LHC will be sensitive to quantum correlations between two quarks inside the proton. Same-sign W-boson pair production is the most promising channel for clear measurements of double parton scattering. The left-handed nature of the coupling between quarks and W-bosons makes it a prime probe to measure parton spin correlations. We perform a detailed analysis of double parton scattering, including relevant backgrounds. The analysis reveals that measurements comparing the rate at which two muons from W boson decays are produced in the same compared to opposite hemispheres are especially sensitive to spin correlations between two quarks inside the proton. We provide estimates of the significance of the measurements as a function of the integrated luminosity.
Higgs pair production is one of the primary goals of the LHC program. Investigating the effects beyond the Standard Model (BSM) is then of high interest. Two cases are presented to exemplify the impact of BSM physics on Higgs pair production and on the triple Higgs coupling: first a review on charged Higgs pair production mostly in the context of Two-Higgs-Doublet of type II and in particular the Minimal Supersymmetric SM, second a study of the one-loop effects of a heavy neutrino on the triple Higgs coupling.
The production of pairs of Higgs bosons at hadron colliders provides unique information on the Higgs sector and on the mechanism underlying electroweak symmetry breaking (EWSB). Most studies have concentrated on the gluon fusion production mode which has the largest cross section. However, despite its small production rate, the vector-boson fusion channel can also be relevant since even small modifications of the Higgs couplings to vector bosons induce a striking increase of the cross section as a function of the invariant mass of the Higgs boson pair. In this work, we exploit this unique signature to propose a strategy to extract the $hhVV$ quartic coupling and provide model-independent constraints on theories where EWSB is driven by new strong interactions. We take advantage of the higher signal yield of the $bbar b bbar b$ final state and make extensive use of jet substructure techniques to reconstruct signal events with a boosted topology, characteristic of large partonic energies, where each Higgs boson decays to a single collimated jet . Our results demonstrate that the $hhVV$ coupling can be measured with 45% (20%) precision at the LHC for $mathcal{L}=$ 300 (3000) fb$^{-1}$, while a 1% precision can be achieved at a 100 TeV collider.
We consider the triple coupling of the Higgs boson in the context of the gauge-Higgs unification scenario. We show that the triple coupling of the Higgs boson in this scenario generically deviates from SM prediction since the Higgs potential in this scenario has a periodicity. We calculate the coupling in the five-dimensional $SU(3)$ x $U(1)_X$ gauge-Higgs unification model and obtain 70% deviation from the SM prediction.
In the framework of effective Lagrangians with the SU(2)_L x U(1)_Y symmetry linearly realized, modifications of the couplings of the Higgs field to the electroweak gauge bosons are related to anomalous triple gauge couplings (TGCs). Here, we show that the analysis of the latest Higgs boson production data at the LHC and Tevatron give rise to strong bounds on TGCs that are complementary to those from direct TGC analysis. We present the constraints on TGCs obtained by combining all available data on direct TGC studies and on Higgs production analysis. Note added: The analysis has been updated with all the public data available as November 2013. Updates of this analysis are provided at http://hep.if.usp.br/Higgs
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