Present Bounds on New Neutral Vector Resonances from Electroweak Gauge Boson Pair Production at the LHC

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.Comment: 10 pages, 6 figure

Effective Lagrangian approach to the EWSB sector

AbstractIn a model independent framework, the effects of new physics at the electroweak scale can be parametrized in terms of an effective Lagrangian expansion. Assuming the SU(2)LxU(1)Y gauge symmetry is linearly realized, the expansion at the lowest order span dimension–six operators built from the observed Standard model (SM) particles, in addition to a light scalar doublet. After a proper choice of the operator basis we present a global fit to all the updated available data related to the electroweak symmetry breaking sector: triple gauge boson vertex (TGV) collider measurements, electroweak precision tests and Higgs searches. In this framework modifications of the interactions of the Higgs field to the electroweak gauge bosons are related to anomalous TGV's, and given the current experimental precision, we show that the analysis of the latest Higgs boson data at the LHC and Tevatron gives rise to strong bounds on TGV's that are complementary to those from direct TGV measurements. Interestingly, we present how this correlated pattern of deviations from the SM predictions could be different for theories based on a non–linear realization of the SU(2)LxU(1)Y symmetry, characteristic of for instance composite Higgs models. Furthermore, anomalous TGV signals expected at first order in the non–linear realization may appear only at higher orders of the linear one, and viceversa. Their study could lead to hints on the nature of the observed boson

Constraining anomalous Higgs interactions

The recently announced Higgs discovery marks the dawn of the direct probing of the electroweak symmetry breaking sector. Sorting out the dynamics responsible for electroweak symmetry breaking now requires probing the Higgs interactions and searching for additional states connected to this sector. In this work we analyze the constraints on Higgs couplings to the standard model gauge bosons using the available data from Tevatron and LHC. We work in a model--independent framework expressing the departure of the Higgs couplings to gauge bosons by dimension--six operators. This allows for independent modifications of its couplings to gluons, photons and weak gauge bosons while still preserving the Standard Model (SM) gauge invariance. Our results indicate that best overall agreement with data is obtained if the cross section of Higgs production via gluon fusion is suppressed with respect to its SM value and the Higgs branching ratio into two photons is enhanced, while keeping the production and decays associated to couplings to weak gauge bosons close to their SM prediction.Comment: v3: Added acknowledgment to FP7 ITN INVISIBLES (Marie Curie Actions PITN-GA-2011-289442). Nothing else changed with respect to v

CP violation with a dynamical Higgs

We determine the complete set of independent gauge and gauge-Higgs CP-odd effective operators for the generic case of a dynamical Higgs, up to four derivatives in the chiral expansion. The relation with the linear basis of dimension six CP-odd operators is clarified. Phenomenological applications include bounds inferred from electric dipole moment limits, and from present and future collider data on triple gauge coupling measurements and Higgs signals.Comment: 41 pages, 3 figures; V2: citations added, typos corrected, version published on JHE

Light Non-degenerate Composite Partners at the LHC

We study the implications of a large degree of compositeness for the light generation quarks in composite pseudo-Nambu-Goldstone-boson Higgs models. We focus in particular on viable scenarios where the right-handed up-type quarks have a sizable mixing with the strong dynamics. For concreteness we assume the latter to be characterized by an SO(5)/SO(4) symmetry with fermionic resonances in the SO(4) singlet and fourplet representations. Singlet partners dominantly decay to a Higgs boson and jets. As no dedicated searches are currently looking for these final states, singlet partners can still be rather light. Conversely, some fourplet partners dominantly decay to an electroweak gauge boson and a jet, a signature which has been analyzed at the LHC. To constrain the parameter space of this scenario we have reinterpreted various LHC analyses. In the limit of first two generation degeneracy, as in minimal flavor violation or U(2)-symmetric flavor models, fourplet partners need to be relatively heavy, with masses above 1.8 TeV, or the level of compositeness needs to be rather small. The situation is rather different in models that deviate from the first two generation degeneracy paradigm, as the charm parton distribution functions are suppressed relative to the up quark ones. The right-handed charm quark can be composite and its partners being as light as 600 GeV, while the right-handed up quark needs either to be mostly elementary or to have its partners as heavy as 2 TeV. Models with fully composite singlet fermions are also analyzed, leading to similar conclusions. Finally, we consider the case where both the fourplet and the singlet states are present. In this case the bounds could be significantly weaken due to a combination of smaller production rates and the opening of new channels including cascade processes.Comment: 49 pages, 18 figure

The complete HEFT Lagrangian after the LHC Run I

The complete effective chiral Lagrangian for a dynamical Higgs is presented and constrained by means of a global analysis including electroweak precision data together with Higgs and triple gauge-boson coupling data from the LHC Run I. The operators’ basis up to next-to-leading order in the expansion consists of 148 (188 considering righthanded neutrinos) flavour universal terms and it is presented here making explicit the custodial nature of the operators. This effective Lagrangian provides the most general description of the physical Higgs couplings once the electroweak symmetry is assumed, and it allows for deviations from the SU (2)L doublet nature of the Standard Model Higgs. The comparison with the effective linear Lagrangian constructed with an exact SU (2)L doublet Higgs and considering operators with at most canonical dimension six is presented. A promising strategy to disentangle the two descriptions consists in analysing (i) anomalous signals present only in the chiral Lagrangian and not expected in the linear one, that are potentially relevant for LHC searches, and (ii) decorrelation effects between observables that are predicted to be correlated in the linear case and not in the chiral one. The global analysis presented here, which includes several kinematic distributions, is crucial for reducing the allowed parameter space and for controlling the correlations between parameters. This improves previous studies aimed at investigating the Higgs Nature and the origin of the electroweak symmetry breakingI.B. research was supported by an ESR contract of the EU network FP7 ITN INVISIBLES (Marie Curie Actions, PITN-GA-2011-289442).M.C.GG is supported by USA-NSF grant PHY-13-16617, by grants 2014- SGR-104 and by FPA2013-46570 and consolider-ingenio 2010 program CSD-2008-0037. L.M. acknowledge partial support of CiCYT through the project FPA2012-31880 and of the Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme under grant SEV- 2012-0249. M.C.G-G and L.M. acknowledge partial support by FP7 ITN INVISIBLES (PITN-GA-2011-289442), FP10 ITN ELUSIVES (H2020-MSCA-ITN-2015-674896) and INVISIBLES-PLUS (H2020- MSCA-RISE-2015-690575

The Higgs Legacy of the LHC Run I

Based on Run I data we present a comprehensive analysis of Higgs couplings. For the first time this SFitter analysis includes independent tests of the Higgs-gluon and top Yukawa couplings, Higgs decays to invisible particles, and off-shell Higgs measurements. The observed Higgs boson is fully consistent with the Standard Model, both in terms of coupling modifications and effective field theory. Based only on Higgs total rates the results using both approaches are essentially equivalent, with the exception of strong correlations in the parameter space induced by effective operators. These correlations can be controlled through additional experimental input, namely kinematic distributions. Including kinematic distributions the typical Run I reach for weakly interacting new physics now reaches 300 to 500 GeV.Comment: 29 pages, 15 figure