This paper reports on a search for heavy resonances decaying into $WW$, $ZZ$ or $WZ$ using proton-proton collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV. The data, corresponding to an integrated luminosity of 139 $\mathrm{fb^{-1}}$, were recorded with the ATLAS detector from 2015 to 2018 at the Large Hadron Collider. The search is performed for final states in which one $W$ or $Z$ boson decays leptonically, and the other $W$ boson or $Z$ boson decays hadronically. The data are found to be described well by expected backgrounds. Upper bounds on the production cross sections of heavy scalar, vector or tensor resonances are derived in the mass range 300-5000 GeV within the context of Standard Model extensions with warped extra dimensions or including a heavy vector triplet. Production through gluon-gluon fusion, Drell-Yan or vector-boson fusion are considered, depending on the assumed model.
We present the first observation of WW+WZ production in the channel with an identified lepton and two jets in 2.7 fb$^{-1}$ of integrated luminosity collected with the CDF II detector in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV. The signal is separated from the large background using matrix element calculations and is observed with a significance of 5.4$σ$. The WW+WZ production cross section is measured to be $17.7 \pm 3.1$(stat)$\pm 2.4$(sys) pb, in good agreement with standard model predictions. A complimentary measurement using a fit to the dijet mass is also presented.
Diboson cross sections have been measured for all combinations of W,Z and isolated photons, using the ATLAS detector at the LHC. The cross sections are measured in kinematic regions defined by the decay kinematics, in some cases including vetoes on additional jets. The measurements are also extrapolated to the full phase space using theoretical calculations of the acceptance, and are additionally used to place constraints on triple-gauge boson couplings.
This review covers results at a centre-of-mass energy of $\sqrt{s}=13$ TeV from the ATLAS experiment that have been published, or submitted for publication, up to April 2020. It summarizes results on the inclusive production cross-section measurements of boson pairs and of the electroweak production of diboson in association with two jets. The measurements either use the full integrated luminosity of 139 $\text{fb}^\text{-1}$ collected by the ATLAS detector at the LHC from 2015 to 2018, or a partial dataset of 36 $\text{fb}^\text{-1}$. The inclusive production rates of diboson are studied to h…
This paper reports on a search for the electroweak diboson ($WW/WZ/ZZ$) production in association with a high-mass dijet system, using data from proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV. The data, corresponding to an integrated luminosity of 35.5 fb$^{-1}$, were recorded with the ATLAS detector in 2015 and 2016 at the Large Hadron Collider. The search is performed in final states in which one boson decays leptonically, and the other boson decays hadronically. The hadronically decaying $W/Z$ boson is reconstructed as either two small-radius jets or one large-radi…
Recent measurements of the associated production of two or three massive vector bosons in proton-proton collisions at the Large Hadron Collider, collected by the ATLAS detector at a centre-of-mass energy of $\sqrt{s} = 13$ TeV, are reported. The diboson analyses target the production and decay modes $WW\rightarrow eν_eμν_μ$, $WZ \rightarrow \ell^{\prime} ν\ell \ell\,(\ell = e, μ)$, $ZZ \rightarrow \ell\ellνν$, and the $4\ell$ final state. Fiducial inclusive cross sections are compared to state-of-the-art Standard Model calculations and several unfolded differential distributions are measured. …
Narrow resonances decaying into $WW$, $WZ$ or $ZZ$ boson pairs are searched for in 36.7 fb $^{-1}$ of proton-proton collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The diboson system is reconstructed using pairs of large-radius jets with high transverse momentum and tagged as compatible with the hadronic decay of high-momentum $W$ or $Z$ bosons, using jet mass and substructure properties. The search is sensitive to diboson resonances with masses in the range 1.2-5.0 TeV. No significant excess is obse…
This paper reports on a search for narrow resonances in diboson production in the $\ell\ell q\bar{q}$ final state using pp collision data corresponding to an integrated luminosity of 20 fb$^{-1}$ collected at $\sqrt{s}=8$ TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95% confidence level are set on the production cross section times branching ratio for Kaluza--Klein gravitons predicted by the Randall--Sundrum model and for Extended Gauge Model W' bosons. These results lead to t…
A search for resonant diboson production using a data sample corresponding to 4.7 fb-1 of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in pp collisions at 7 TeV is presented. The search for a narrow resonance in the WW or WZ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum and at least two jets. No significant excess is observed and limits are set using three benchmark models: WW resonance masses below 940 GeV and 710 GeV are excluded at 95% confidence level for spin-2 Randall-Sundrum and bulk Randal…
Narrow resonances decaying into $WW$, $WZ$ or $ZZ$ boson pairs are searched for in 139 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded with the ATLAS detector at the Large Hadron Collider from 2015 to 2018. The diboson system is reconstructed using pairs of high transverse momentum, large-radius jets. These jets are built from a combination of calorimeter- and tracker-inputs compatible with the hadronic decay of a boosted $W$ or $Z$ boson, using jet mass and substructure properties. The search is performed for diboson resonances with masses gr…
We investigate $W'$ interpretations for the ATLAS 2 TeV diboson anomalies. The roles of the unitarity sum rules, which ensure the perturbativity of the longitudinal vector boson scattering amplitudes, are emphasized. We find the unitarity sum rules and the custodial symmetry are powerful enough to predict various nontrivial relations among $WWZ'$, $WZW'$, $WWh$, $WW'h$ and $ZZ'h$ coupling strengths in a model independent manner. We also perform surveys in the general parameter space of $W'$ models and find the ATLAS 2 TeV diboson anomalies may be interpreted as a $W'$ particle of the three sit…
This paper presents an overview of the diboson production cross-section measurements and constraints on anomalous triple-gauge boson couplings performed by the ATLAS and CMS collaborations using proton-proton collisions produced at a centre-of-mass energy of sqrt{s} = 7 and 8 TeV at LHC. Results for all combinations of W, Z and γ gauge bosons (excluding γγ) are presented with emphasis on the new WZ and ZZ production cross sections measured by ATLAS at sqrt{s} = 8 TeV and on the new constraints on anomalous triple-gauge couplings set by CMS in the WW and Zγ modes.
The ATLAS collaboration has reported excesses in diboson invariant mass searches of new resonances around 2 TeV, which might be a prediction of new physics around that mass range. We interpret these results in the context of a modified stealth doublet model where the extra Higgs doublet has a Yukawa interaction with the first generation quarks, and show that the heavy CP-even Higgs boson can naturally explain the excesses in the WW and ZZ channels with a small Yukawa coupling, ξ\sim 0.15, and a tiny mixing angle with the SM Higgs boson, α\sim 0.06. Furthermore, the model satisfy constraints fr…
Recently, the ATLAS Collaboration recorded an interesting anomaly in diboson production with excesses at the diboson invariant mass around 2 TeV in boosted jets of all the $WZ$, $W^+ W^-$, and $ZZ$ channels. We offer a theoretical interpretation of the anomaly using a phenomenological right-handed model with extra $W'$ and $Z'$ bosons. Constraints from narrow total decay widths, dijet cross sections, and $W/Z + H$ production are taken into account. We also comment on a few other possibilities.
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, $H\rightarrowγγ$, $H\rightarrow ZZ^{*}\rightarrow 4 \ell$ and $H\rightarrow W W \rightarrow \ellν\ellν$. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of about 25 fb$^{-1}$. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Hig…
Heavy resonances decaying into a pair of fundamental particles such as $jj$, $\ell^+\ell^-$, $γγ$, and $\ellν$, are among the most common features to search for phenomena beyond the standard model (SM). Electroweak boson pair production, such as $WW$ or $ZZ$ with subsequent decays to $\ellν\ell'ν'$ and $\ell\ell jj$ respectively, is a powerful test of the spontaneously broken gauge symmetry of the SM and can be also used to search for phenomena beyond the SM. There is a wide spectrum of theoretical models predicting these kinds of resonant signatures. This note covers several searches for thes…
Motivated by ATLAS diboson excess around 2 TeV, we investigate a phenomenology of spin-1 resonances in a model where electroweak sector in the SM is weakly coupled to strong dynamics. The spin-1 resonances, W' and Z', are introduced as effective degrees of freedom of the dynamical sector. We explore several theoretical constraints by investigating the scalar potential of the model as well as the current bounds from the LHC and precision measurements. It is found that the main decay modes are V' -> VV and V' -> Vh, and the V' width is narrow enough so that the ATLAS diboson excess can be explai…
The ATLAS excess in fat jet pair production is kinematically compatible with the decay of a heavy resonance into two gauge bosons plus an extra particle. This hypothesis would explain the absence of such a large excess in the analogous CMS analysis of fat dijet final states, as well as the negative results of diboson resonance searches in the semi-leptonic decay modes. If the extra particle is the Higgs boson, this hypothesis might also explain -statistical fluctuations aside- why the CMS search for WH resonances in the semi-leptonic channel finds some excess while in the fully hadronic one it…
We provide an interpretation of the recent ATLAS diboson excess in terms of a class of supersymmetric models in which the scale of supersymmetry (SUSY) breaking is in the few TeV range. The particle responsible for the excess is the scalar superpartner of the Goldstone fermion associated with SUSY breaking, the sgoldstino. This scalar couples strongly to the Standard Model vector bosons and weakly to the fermions, with all coupling strengths determined by ratios of soft SUSY breaking parameters over the SUSY breaking scale. Explaining the ATLAS excess selects particular relations and ranges fo…
A search is performed for narrow resonances decaying into $WW$, $WZ$, or $ZZ$ boson pairs using 20.3 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. Diboson resonances with masses in the range from 1.3 to 3.0 TeV are sought after using the invariant mass distribution of dijets where both jets are tagged as a boson jet, compatible with a highly boosted $W$ or $Z$ boson decaying to quarks, using jet mass and substructure properties. The largest deviation from a smoothly falling background in…
Electroweak diboson production in association with a high-mass dijet system in semileptonic final states from $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究中心）
Studies of the spin, parity and tensor couplings of the Higgs boson in the $H\rightarrow ZZ^*\rightarrow 4\ell$, $H\rightarrow WW^* \rightarrow eνμν$ and $H\rightarrow γγ$ decay processes at the LHC are presented. The investigations are based on $25$ fb$^{-1}$ of $pp$ collision data collected by the ATLAS experiment at $\sqrt{ s} = 7$ TeV and $\sqrt{ s }= 8$ TeV. The Standard Model (SM) Higgs boson hypothesis, corresponding to the quantum numbers $J ^P=0^+$, is tested against several alternative spin scenarios, including non-SM spin-0 and spin-2 models with universal and non-universal coupling…
We study an s-channel resonance $R$ as a viable candidate to fit the diboson excess reported by ATLAS. We compute the contribution of the $\sim 2$ TeV resonance $R$ to semileptonic and leptonic final states at 13 TeV LHC. To explain the absence of an excess in semileptonic channel, we explore the possibility where the particle $R$ decays to additional light scalars $X,X$ or $X,Y$. Modified analysis strategy has been proposed to study three particle final state of the resonance decay and to identify decay channels of $X$. Associated production of $R$ with gauge bosons has been studied in detail…
Searches for new heavy resonances decaying to $WW$, $WZ$, and $ZZ$ bosons are presented, using a data sample corresponding to 3.2 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=13$ TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting $ννqq$, $\ellνqq$, $\ell\ell qq$ and $qqqq$ final states are combined, searching for a narrow-width resonance with mass between 500 and 3000 GeV. The discriminating variable is either an invariant mass or a transverse mass. No significant deviations from the Standard Model predictions are observed. Three benchmark models are teste…
A general review of the latest results about single and double vector boson production in the multipurpose experiments at LHC (ATLAS and CMS) and at Tevatron (CDF and D0) will be presented. The review will focus on boson production, while a more detailed report about W and Z properties can be found elsewhere. Only leptonic decays into electrons and muons will be considered.
We perform a general analysis of new physics interpretations of the recent ATLAS diboson excesses over Standard Model expectations in LHC Run I collisions. Firstly, we estimate a likelihood function for the true signal in the $WW$, $WZ$, and $ZZ$ channels, finding that the maximum has zero events in the $WZ$ channel, though the likelihood is sufficiently flat to allow other scenarios. Secondly, we survey the possible effective field theories containing the Standard Model plus a new resonance that could explain the data, finding just two possibilities, viz., a vector that is either a left- or r…
The ATLAS collaboration has recently reported a 2.6 sigma excess in the search for a heavy resonance decaying into a pair of weak gauge bosons. Only fully hadronic final states are being looked for in the analysis. If the observed excess really originates from the gauge bosons' decays, other decay modes of the gauge bosons would inevitably leave a trace on other exotic searches. In this paper, we propose the use of the Z boson decay into a pair of neutrinos to test the excess. This decay leads to a very large missing energy and can be probed with conventional dark matter searches at the LHC. W…
Most recent measurements of properties of $W$ and $Z$ gauge bosons at hadron colliders are presented. The measurements were performed by ATLAS, CMS, and LHCb collaborations with proton-proton collisions at the LHC and by CDF and D0 collaborations with proton-antiproton collisions at the Tevatron. Center-of-mass energy was 7 TeV and 1.96 TeV at the LHC and Tevatron respectively. Integrated luminosity ranges from 35 pb$^{-1}$ to 1.02 pb$^{-1}$ for LHC and from 0.2 fb$^{-1}$ to 7.1 fb$^{-1}$ for Tevatron.
The full ATLAS Run 2 data set with time-integrated luminosity of 139 fb$^{-1}$ in the diboson channels in hadronic final states is used to probe a simple model with an extended gauge sector (EGM), proposed by Altarelli et al., and often taken as a convenient benchmark by experimentalists. This model accommodates new charged $W'$ and neutral $Z'$ vector bosons with modified trilinear Standard Model gauge couplings, decaying into electroweak gauge boson pairs $WZ$ or $WW$, where $W$/$Z$ decay hadronically. Exclusion limits at the 95% C.L. on the $Z'$ and $W'$ resonance production cross section t…
We discuss the diboson excess seen by the ATLAS detector around 2 TeV in the LHC run I at $\sqrt{s}=8$ TeV. We explore the possibility that such an excess can arise from a $Z'$ boson which acquires mass through a $U(1)_X$ Stueckelberg extension. The corresponding $Z'$ gauge boson is leptophobic with a mass of around 2 TeV and has interactions with $SU(2)_L$ Yang-Mills fields and gauge fields of the hypercharge. The analysis predicts $Z'$ decays into $WW$ and $ZZ$ as well as into $Zγ$. Further three-body as well as four-body decays of the $Z'$ such as $WWZ, WWγ, WWZZ$ etc are predicted. In the …
This review article summarizes results on the production cross section measurements of electroweak boson pairs ($WW$, $WZ$, $ZZ$, $Wγ$ and $Zγ$) at the Large Hadron Collider (LHC) in $pp$ collisions at a center-of-mass energy of $\sqrt{s}=7$ \TeV. The two general-purpose detectors at the LHC, ATLAS and CMS, recorded an integrated luminosity of $5fb^{-1}$ in 2011, which offered the possibility to study the properties of diboson production to high precision. These measurements test predictions of the Standard Model (SM) in a new energy regime and are crucial for the understanding and the measure…
The resonant excesses around 2 TeV reported by the ATLAS Collaboration can be explained in the left-right model, and the tight constraints from lepton plus missing energy searches can be evaded if the $SU(2)_R$ gauge symmetry is leptophobic. We for the first time propose an anomaly free leptophobic left-right model with gauge symmetry $SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_{X}$ where the SM leptons are singlets under $SU(2)_R$. The gauge anomalies are cancelled by introducing extra vector-like quarks. The mass of $Z^\prime$ gauge boson, which cannot be leptophobic, is assumed to be…
We investigate the implications of a putative new resonance in the TeV region coupled to the weak bosons. By studying perturbative unitarity in longitudinal WW scattering, we find that a weakly coupled spin-1 resonance, that explains the ATLAS diboson excesses, is allowed with a SM-like Higgs. On the other hand, larger values of the resonance couplings, preferred in models of strong dynamics, would imply either sizeable reduction of the Higgs couplings or new physics, beyond the diboson resonance, at a few TeV.
A search is presented for narrow diboson resonances decaying to $WW$ or $WZ$ in the final state where one $W$ boson decays leptonically (to an electron or a muon plus a neutrino) and the other $W/Z$ boson decays hadronically. The analysis is performed using an integrated luminosity of 20.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 8 TeV collected by the ATLAS detector at the LHC. No evidence for resonant diboson production is observed, and resonance masses below 700 GeV and 1490 GeV are excluded at 95% confidence level for the spin-2 Randall-Sundrum bulk graviton $G^*$ with coupling constan…
An overview of recent measurements of electroweak and top quark physics is given. In particular, total and differential diboson cross sections, limits on anomalous triple gauge couplings as well as top quark production cross sections and properties, such as charge asymmetry, top quark polarization and Wtb vertex measurements, are presented. Proton-proton collision data produced at the LHC at sqrt s = 7 TeV and sqrt s = 8 TeV collected with the ATLAS detector are used.
This note presents the prospects of searches for new heavy resonances decaying to diboson (WW) and measurements of electroweak WW/WZ production via vector boson scattering (VBS) in association with a high-mass dijet system in the $\ellνqq$ final states ($W\to\ellν$, $W/Z\to qq$). The prospects are presented for an integrated luminosity of 15 ab$^{-1}$ of proton-proton ($pp$) collisions at $\sqrt{s}=27$ TeV with an ATLAS-like detector simulated in the Delphes framework. The cross-section measurement of the electroweak $WW/WZ$ production in VBS processes is expected to reach the precision of $\s…
We propose a new explanation for excess events observed in the search for a high-mass resonance decaying into dibosons by the ATLAS experiment. The resonance is identified as a composite spin-$0$ particle that couples to the Standard Model gauge bosons via dimension-5 operators. The excess events can be explained if the dimension-5 operators are suppressed by a mass scale of ${\cal O}(1$-$10$) TeV. We also construct a model of hidden strong gauge dynamics which realizes the spin-$0$ particle as its lightest composite state, with appropriate couplings to Standard Model gauge bosons.
This review covers results of searches for new elementary particles that decay into boson pairs (dibosons), performed at the CERN Large Hadron Collider in proton-proton collision data collected by the ATLAS and CMS experiments at 7-, 8-, and 13-TeV center-of-mass energy until the year 2017. The available experimental results of the analysis of final states including most of the possible two-object combinations of W and Z bosons, photons, Higgs bosons, and gluons place stringent constraints on a variety of theoretical ideas that extend the standard model, pushing into the multi-TeV region the s…
In this Letter, we study the latest bound on the mass of doubly charged Higgs bosons, $H^{\pm\pm}$, assuming that they dominantly decay into a diboson. The new bound is obtained by comparing the inclusive searches for events with a same-sign dilepton by the ATLAS Collaboration using the latest 20.3 fb$^{-1}$ data at the LHC 8 TeV run with theoretical prediction based on the Higgs triplet model with next-to-leading order QCD corrections. We find that the lower mass bound on $H^{\pm\pm}$ is about 84 GeV.
The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region $1.8-2.2$ TeV. In the light of these results, we argue that such signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I Two Higgs Doublet Model. We demonstrate that in the presence of colored vector-like fermions, its gluon fusion production cross-section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. O…
We study the collider implication of a neutral resonance which decays to several diboson final states such as $W^+W^-$, $ZZ$, and $Zγ$ via a minimal set of effective operators. We consider both CP-even and CP-odd bosonic states with spin 0, 1, or 2. The production cross sections for the bosonic resonance states are obtained with the effective operators involving gluons (and quarks), and the branching fractions are obtained with the operators responsible for the interactions with electroweak gauge bosons. We demonstrate that each scenario allows for a broad parameter space which could accommoda…
We investigate diboson signals in the Standard Model (SM) with an extended Higgs sector, motivated by the excesses in the diboson channels at the LHC. We begin with the unitarity sum-rules of the weak gauge boson scattering assuming the Higgs sector is extended. According to the sum-rules, we discuss the Higgs interpretations of the diboson signals and the consistency with the ATLAS diboson anomaly and other experimental constraints. As a concrete example, we propose a two-Higgs-doublet model where the Yukawa coupling of an extra CP-even scalar with up-type quark is relatively large. The dibos…
I summarize an extensive ATLAS and CMS electroweak physics program that involves a variety of single boson, diboson, triboson, and vector boson scattering measurements. The relevance of these studies to our understanding of the electroweak sector and electroweak symmetry breaking is emphasized. I describe the recent results and prospects for future measurements.
Diboson resonance with mass around 2 TeV in the dijet invariant mass spectrum is reported by ATLAS experiment in proton-proton collisions at $\sqrt{s}=8$ TeV. We propose that the candidate of resonance is a heavy neutral Higgs $H^0$ or charged Higgs $H^\pm$ and use the extended two-Higgs-doublet (THD) to demonstrate the potentiality. We find that the large Yukawa coupling to the first generation of quarks can be realized in THD and the required value for producing the right resonance production cross section is of ${\cal O}(0.06-0.2)$. Besides $WW/ZZ$ channels, we find that if the mass of pseu…
ATLAS results are presented on a search for flavor-changing neutral currents (FCNC) in top quark decays at the LHC. Events are searched for where a pair of top quarks is produced and one decays through the Standard Model $t \rightarrow Wb$ mode while the other decays through the FCNC mode $t \rightarrow qZ$. Leptonic final states are used in which both the $W$- and $Z$-bosons decay leptonically, yielding final states with three leptons and two jets. The observed events are consistent with the expected backgrounds from Drell-Yan and diboson production and a limit on the FCNC branching ratio of …
The ATLAS Collaboration has reported excesses in the search for resonant diboson production with decay modes to hadronic final states at a diboson invariant mass around 2 TeV in boosted jets from $WZ$, $W^+W^-$, and $ZZ$ channels. Given potential contamination, we investigate the anomalies in leptophobic $U(1)_{\rm LP}$ models. We show that leptophobic models can be constructed in flipped $SU(5)\times U(1)_X$ models from free fermionic string constructions and Pati-Salam models from D-brane constructions. Additionally, we perform a collider phenomenological analysis to study production cross s…
The ATLAS experiment at the CERN Large Hadron Collider has performed searches for new, heavy bosons decaying to $WW$, $WZ$ and $ZZ$ final states in multiple decay channels using 20.3 fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 8$ TeV. In the current study, the results of these searches are combined to provide a more stringent test of models predicting heavy resonances with couplings to vector bosons. Direct searches for a charged diboson resonance decaying to WZ in the $\ellν\ell'\ell'$ ($\ell = μ, e$) , $\ell\ell q \bar{q}$, $\ell νq \bar{q}$ and fully hadronic final states are combined a…
We present a systematic interpretation of vector boson scattering (VBS) and diboson measurements from the LHC in the framework of the dimension-six Standard Model Effective Field Theory (SMEFT). We consider all available measurements of VBS fiducial cross-sections and differential distributions from ATLAS and CMS, in most cases based on the full Run II luminosity, and use them to constrain 16 independent directions in the dimension-six EFT parameter space. Compared to the diboson measurements, we find that VBS provides complementary information on several of the operators relevant for the desc…
In view of the recent diboson resonant excesses reported by both ATLAS and CMS Collaborations, we suggest that a new weak singlet pseudo-scalar particle, $η_W$, may decay into two weak bosons while being produced in gluon fusion at the LHC. The couplings to the gauge bosons can arise from a Wess-Zumino-Witten anomaly term and thus we study an effective model based on the anomaly term as a well motivated phenomenological model. In models where the pseudo-scalar arises as a composite state, the coefficients of the anomalous couplings can be related to the fermion components of the underlying dyn…
A direct search for doubly-charged Higgs bosons $H^{\pm\pm}$ is one of the most important probe in the Higgs Triplet Model, which is motivated by generation mechanisms of tiny neutrino masses. There are two major decay modes of $H^{\pm\pm}$; i.e., the same-sign dilepton decay $H^{\pm\pm}\to\ell^\pm\ell^\pm$ and the same-sign diboson decay $H^{\pm\pm}\to W^{\pm(*)}W^{\pm(*)}$. For the case where the former decay mode is dominant, the lower limit on the mass of $H^{\pm\pm}$ has been set at about 400 GeV by ATLAS and CMS Collaborations. On the other hand, for the case where the latter decay mode …
ATLAS and CMS observe deviations from the expected background in diboson invariant mass searches of new resonances around 2 TeV. We provide a general analysis of the results in terms of spin-one resonances and find that Fermi scale composite dynamics can be the culprit. The analysis and methodology can be employed for future searches at run two of the Large Hadron Collider.
We perform a statistical combination of the ATLAS and CMS results for the search of a heavy resonance decaying to a pair of vector bosons with the $\sqrt{s}=8$ TeV datasets collected at the LHC. We take into account six searches in hadronic and semileptonic final states carried out by the two collaborations. We consider only public information provided by ATLAS and CMS in the HEPDATA database and in papers published in refereed journals. We interpret the combined results within the context of a few benchmark new physics models, such as models predicting the existence of a {\ensuremath{\mathrm{…
The ATLAS and CMS collaborations have recently released significant new data on Higgs and diboson production in LHC Run 2. Measurements of Higgs properties have improved in many channels, while kinematic information for $h \to γγ$ and $h \to ZZ$ can now be more accurately incorporated in fits using the STXS method, and $W^+ W^-$ diboson production at high $p_T$ gives new sensitivity to deviations from the Standard Model. We have performed an updated global fit to precision electroweak data, $W^+W^-$ measurements at LEP, and Higgs and diboson data from Runs 1 and 2 of the LHC in the framework o…
The production of a top quark in association with a $Z$ boson is studied in the trilepton channel. The data collected by the ATLAS experiment at the LHC in 2015 and 2016 at a centre-of-mass energy of $\sqrt{s} = 13\,\text{TeV}$ are used, corresponding to an integrated luminosity of $36.1\,\text{fb}^{-1}$. Events containing three identified leptons (electron and/or muon) and two jets, one of which is identified as a $b$-quark jet are selected. The major backgrounds come from diboson, $t\bar{t}$ and $Z+$jets production. A neural network is used to improve the background rejection and extract the…
Recently reported diboson and diphoton excesses at LHC are interpreted to be connected with heavy $WW$ zero spin resonances. The resonances appears due to the wouldbe anomalous triple interaction of the weak bosons, which is defined by well-known coupling constant $λ$. The $2\, TeV$ anomaly tentatively corresponds to weak isotopic spin 2 scalar state and the $γγ\,\,750\, GeV$ anomaly corresponds to weak isotopic spin 0 pseudoscalar state. We obtain estimates for the effect, which qualitatively agree with ATLAS data. Effects are predicted in a production of $W^+ W^-, (Z,γ) (Z,γ)$ via resonance …
Same- and opposite-sign charge asymmetries are measured in lepton+jets $t\bar{t}$ events in which a $b$-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb$^{-1}$ from proton--proton collisions at a centre-of-mass energy of $\sqrt{s}=8$ TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a $b$-hadron and are measured in a fiducial region corresponding to the experim…
A study of WZ production in proton-proton collisions at sqrt(s) = 7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb^-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68+/-10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be sigma_WZ(tot) = 19.0+1.4/-1.3(stat.)+/-0.9(syst.)+/-0.4(lumi.) pb, consistent with the Standard Model expectation of 17.6+1.1/-1.0 pb. Limits on anomalo…
