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Register a new userPresent Bounds on New Neutral Vector Resonances from Electroweak Gauge Boson Pair Production at the LHC
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Several extensions of the Standard Model predict the existence of new neutral spin-1 resonances associated to the electroweak symmetry breaking sector. Using the data from ATLAS (with integrated luminosity of L=1.02 fb^{-1}) and CMS (with integrated luminosity of L=1.55 fb^{-1}) on the production of W+W- pairs through the process pp -> l^+ l^{prime -} sla{E}_T, we place model independent bounds on these new vector resonances masses, couplings and widths. Our analyses show that the present data excludes new neutral vector resonances with masses up to 1-2.3 TeV depending on their couplings and widths. We also demonstrate how to extend our analysis framework to different models working a specific example.
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The model independent bounds on new neutral vector resonances masses, couplings and widths presented at arxiv:1112.0316 are updated with an integrated luminosity of L=4.7 fb^-1 from ATLAS and L=4.6 fb^-1 from CMS. These exclusion limits correspond to the most stringent existing bounds on the production of new neutral spin-1 resonances that decay to electroweak gauge boson pairs and that are associated to the electroweak symmetry breaking sector in several extensions of the Standard Model.
We search for signatures of the extra neutral gauge boson $ Z^prime$, predicted in some extensions of the Standard Model, from the analysis of some distributions for $p + p longrightarrow mu^+ + mu^- + X$, where the only exotic particle involved is $ Z^prime$. In addition to the invariant mass and charge asymmetry distributions, we propose in our search to use the transverse momentum distribution ($p_T$) as an observable. We do our calculation for two values of the LHC center of mass energy (7 and 14 TeV), corresponding to 1 and 100 fb$^{-1}$ of luminosity, in order to compare our findings from some models with the distributions following from the Standard Model. By applying convenient cuts in the invariant mass, we show that the final particles $p_T$ distributions can reveal the presence of an extra neutral gauge boson contribution. We also claim that it is possible to disentangle the models considered here and we emphasize that the minimal version of the model, based on ${SU (3)_C times SU (3)_L times U (1)_X}$ symmetry, presents the more clear signatures for $ Z^prime$ existence.
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.
Vector-boson scattering (VBS) processes probe the innermost structure of electroweak interactions in the Standard Model, and provide a unique sensitivity for new physics phenomena affecting the gauge sector. In this review, we report on the salient aspects of this class of processes, both from the theory and experimental point of view. We start by discussing recent achievements relevant for their theoretical description, some of which have set important milestones in improving the precision and accuracy of the corresponding simulations. We continue by covering the development of experimental techniques aimed at detecting these rare processes and improving the signal sensitivity over large backgrounds. We then summarise the details of the most relevant VBS signatures and review the related measurements available to date, along with their comparison with Standard-Model predictions. We conclude by discussing the perspective at the upcoming Large Hadron Collider runs and at future hadron facilities.
Weak gauge boson pair production is an important process at the LHC because it probes the non-Abelian structure of electroweak interactions and it is a background process for many new physics searches, and with enough statistics we can perform comparisons between measurements and theoretical calculations for different but correlated observables. In these proceedings, we present a theoretical status including state-of-the-art results from recent calculations of higher-order QCD and electroweak corrections.
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