Multiboson Production Research Articles

Multiboson production at the LHC

In this contribution, I discuss the new topics of quantum entanglement and polarized cross sections in diboson production processes at the LHC. Motivations for triboson production studies are given.

Search for the anomalous quartic gauge couplings through Z γ production at e − e + colliders

Spontaneous breaking of the electroweak symmetry of the standard model (SM) sets the constraints on triple and quartic gauge couplings. Therefore, the measurement of multiboson production in e − e + collisions allows us to directly test the predictions of the SM and to indirectly probe new physics beyond the SM. In this paper, we focus on the process e − e + → e − Z γ e + with Z boson decaying into neutrinos to study the anomalous quartic gauge couplings using the effective Lagrangian approach at the compact linear collider (CLIC). We obtain the sensitivities on the anomalous f T,i /Λ4 (i = 0, 2, 5, 6, 7, 8, 9) couplings taking into account the systematic uncertainties of 3, 5% at 95% Confidence Level for the CLIC with TeV. Our results show that the sensitivities on some anomalous couplings without systematic errors are up to two orders of magnitude better than the current experimental limits. Considering a realistic systematic uncertainty such as 5% from possible experimental sources, the sensitivity of all anomalous quartic couplings becomes worse by about 10% compared to those without systematic uncertainty for the CLIC.

Multiboson signals in the UN2HDM

We address multiboson production from a heavy Z' resonance in the context of the UN2HDM, a standard model extension with an additional text {U}(1)' symmetry and an enlarged scalar sector with an extra doublet and a singlet. After taking into account theoretical and experimental constraints on the model, it turns out this type of signals – mostly uncovered by current searches – could be sizeable. We focus on three benchmark scenarios, each of them predicting up to 4000 multiboson events with the LHC Run 2 collected luminosity. Anomaly-detection methods could uncover those signals, if present in data.

Analysis of the anomalous quartic WWWW couplings at the LHeC and the FCC-he

The quartic gauge boson couplings that identify the strengths of the gauge boson self-interactions are exactly determined by the non-Abelian gauge nature of the Standard Model. The examination of these couplings at $ep$ collisions with high center-of-mass energy and high integrated luminosity provides an important opportunity to test the validity of the Standard Model and the existence of new physics beyond the Standard Model. The quartic gauge boson couplings can contribute directly to multi-boson production at colliders. Therefore, we examine the potential of the process $ep \rightarrow \nu_{e}W^{+}W^{-} j$ at the Large Hadron Electron Collider and the Future Circular Collider-hadron electron to study non-standard $WWWW$ couplings in a model independent way by means of the effective Lagrangian approach. We present an investigation on measuring $W^{+}W^{-}$ production in pure leptonic and semileptonic decay channels. In addition, we calculate the sensitivity limits at $95\%$ Confidence Level on the anomalous $\frac{f_{M0}}{\Lambda^{4}}$, $\frac{f_{M1}}{\Lambda^{4}}$, $\frac{f_{M7}}{\Lambda^{4}}$, $\frac{f_{S0}}{\Lambda^{4}}$, $\frac{f_{S1}}{\Lambda^{4}}$, $\frac{f_{T0}}{\Lambda^{4}}$, $\frac{f_{T1}}{\Lambda^{4}}$ and $\frac{f_{T2}}{\Lambda^{4}}$ couplings obtained by dimension-8 operators through the process $ep \rightarrow \nu_{e}W^{+}W^{-} j$ for the Large Hadron Electron Collider and the Future Circular Hadron Electron Collider's different center-of-mass energies and integrated luminosities. Our results show that with the process $ep \rightarrow \nu_{e}W^{+}W^{-} j$ at the Large Hadron Electron Collider and the Future Circular Collider-hadron electron the sensitivity estimated on the anomalous $WWWW$ couplings can be importantly strengthened.

CP violation at ATLAS in effective field theory

CP violation beyond the Standard Model (SM) is a crucial missing piece for explaining the observed matter-antimatter symmetry in the Universe. Recently, the ATLAS experiment at the Large Hadron Collider has performed an analysis of electroweak $Zjj$ production, thereby excluding the SM locally at 95\% confidence level in the measurement of CP-sensitive observables. We take the excess' interpretation in terms of anomalous gauge-Higgs interactions at face value and discuss further steps that are required to scrutinize its origin. In particular, we discuss the relevance of multi-boson production using adapted angular observables to show how they can be used to directly tension the reported $Zjj$ excess in a more comprehensive analysis. To connect the excess to a concrete UV scenario for which the underlying assumptions of the $Zjj$ analysis are valid, we identify vector-like leptons as a candidate theory consistent with the observed CP-odd Wilson coefficient hierarchy observed by ATLAS. We perform a complete one-loop matching calculation to motivate further model-specific and correlated new physics searches. In parallel, we provide estimates of the sensitivity reach of the LHC's high luminosity phase for this particular scenario of CP-violation in light of electroweak precision and Run-2 Higgs data. These provide strong constraints on the model's CP-even low-energy phenomenology, but also inform the size of the CP-odd SM deformation indirectly via our model hypothesis.

Precise test of Higgs boson properties via triple Higgs boson production in vector boson fusion at future colliders

For certain classes of Beyond the Standard Model theories, including composite Higgs models, the coupling of the Higgs to gauge bosons can be different from the Standard Model one. In this case, the multi-boson production via vector boson fusion (VBF) can be hugely enhanced in comparison to the SM production one due to the lack of cancellation in longitudinal vector boson scattering. Among these processes, triple Higgs boson production in VBF plays a special role - its enhancement is especially spectacular due to the absence of background from transversely polarised vector bosons in the final state. While the rates from $pp\to jjhhh$ production in vector boson fusion are too low at the LHC and even at future 33 TeV $pp$ colliders, we have found that the 100 TeV $pp$ future circular collider (FCC) has the unique opportunity to probe the $hVV$ coupling far beyond the LHC sensitivity. We have evaluated the $pp\to jjhhh$ rates as a function of deviation from the $hVV$ coupling and have found that the background is much smaller than the signal for observable signal rates. We also found that the 100 TeV $pp$ FCC can probe the $hVV$ coupling up to the permille level, which is far beyond the LHC reach. These results highlight a special role of the $hhh$ VBF production and stress once more the importance of the 100 TeV $pp$ FCC.

3rd International Conference on Particle Physics and Astrophysics (ICPPA 2017)

1. PrefaceThe 3rd International Conference on Particle Physics and Astrophysics (ICPPA-2017) was held in Moscow, Russia, from October 2 to 5, 2017. The conference is organized by the National Research Nuclear University "MEPhI". The aim of the Conference is to promote contacts between scientists and to develop new ideas in fundamental research. We bring together experts and young scientists working on experimental and theoretical aspects of particle physics on the Earth and in the Space and cosmology (figure 1). The conference covers a wide range of topics such as accelerator physics, (astro) particle physics, cosmic rays, cosmology and methods of experimental physics: detectors and instruments. These directions are unified by development of the Standard Model which is evidently not complete. There are deviations from the Standard Model: neutrino oscillations, the dark matter existence, which are main subjects of the Conference. Various aspects of Standard Model testing and search for new phenomena are main subjects of the conference. Among them: flavor physics (LHCb, Belle, BESIII and other experiments), precision multi-boson production measurements (ATLAS, CMS and other experiments), dark matter searches. Electroweak interaction was discussed in the talks given by participants of neutrino physics experiments (Borexino, Neutrino-4, SOX, T2K and others).Lists of committees are available in this pdf.

Precision measurements and searches with single and multiple gauge bosons with the ATLAS detector

The ATLAS collaboration has carried out a set of measurements at center-of-mass energies of 8 TeV and 13 TeV, which provide stringent tests of the electroweak sector of the Standard Model, specifically on single, di- and multi-boson production cross sections.This paper gives a review of the latest results on these topics from ATLAS. It covers the inclusive production measurement of single W and Z/γ * bosons and the measurement of the complete set of coefficients that describe the angular distributions of the decay leptons in Z events. Also it includes the review of the inclusive and differential cross sections measurements for the production of two heavy gauge bosons (WW , WZ , ZZ ) in the leptonic channels, the production measurement of the Z boson in association with one or two photons and the search for the WZ production via vector-boson scattering. These measurements are compared to (N)NLO predictions of the Standard Model and provide model-independent constraints on the so-called «new physics», by setting the limits on the anomalous triple or quartic gauge-boson couplings.

The 2nd International Conference on Particle Physics and Astrophysics

The 2nd International Conference on Particle Physics and Astrophysics (ICPPA-2016) was held in Moscow, Russia, from October 10 to 14, 2016. The conference is organized by the National Research Nuclear University “MEPhI”. The aim of the Conference is to promote contacts between scientists and to develop new ideas in fundamental research. We bring together experts and young scientists working on experimental and theoretical aspects of nuclear, particle and astroparticle physics and cosmology.The conference covers a wide range of topics such as accelerator physics, (astro) particle physics, cosmic rays, cosmology and methods of experimental physics: detectors and instruments. These directions are unified by development of the Standard Model which is evidently not complete. There are deviations from the Standard Model: neutrino oscillations, the dark matter existence. Together with strong interactions they are main subjects of the Conference.New results from leading high energy physics collaborations are discussed. Main LHC experiments (ATLAS, CMS, ALICE) presented their results and detector upgrade prospects on the conference. Various aspects of Standard Model testing and search for new phenomena are main subjects of the conference. Among them: flavor physics at B factories, precision multi-boson production measurements, dark matter searches.Electroweak interaction was discussed in the talks given by participants of neutrino physics experiments (Borexino, Neutrino-4, SOX, T2K and others). Enigmatic properties of neutrinos such as their tiny masses, oscillations between different neutrino types, cannot be explained in frame of the modern theory and require new approaches. Properties of neutrinos influenced the formation of the large-scale structure of the Universe and may be neutrinos are partially responsible for the excess of matter over anti-matter. Also our current challenge is the nature of the Dark matter. Many opportunities arise with the development of neutrino detection technologies comprising: measurements of neutrinos from the Sun, measurements of geo-neutrino from the deep interior of the Earth, detecting neutrino fluxes from supernovae and different astrophysical sources. They were the subject of discussion which have been held at the conference. Neutrino physics experiments make huge demands to technologies like ultra-high precision measurements, huge detector size, excellent reliability and ultra-low radioactive background.AcknowledgmentsWe are thankful to Anotonova M M, Buzhan P Zh, Gurov Yu B, Vdovkina S S, Zherebtsova E S, Esipova E A, Kovylyaeva A A, Kozlov E S, Koshelenko D D, Matveev N A, Mayorov A G, Nigmatkulov G A, Novikov A S, Svadkovsky I V, Smirnov Yu S, Voronov S A and Yurin K O for the assistance in organizing the conference and heavy work on proceedings.Conference organizers would like to express their gratitude to the TFT company (supply and maintenance of CAEN equipment, delivery of equipment and components for scientific research) for their support.

Measurements of Multi-boson production, Trilinear and Quartic Gauge Couplings with the ATLAS detector

The ATLAS collaboration has carried a set of measurements that provide stringent tests of the electroweak sector of Standard Model, specifically on di- and multiboson production cross sections and on triple and quartic gauge-boson couplings. Such measurements include cross sections for WV (V=W or Z) production in the leptonic or semileptonic channels, the production of a W or Z boson in association with photons, a Z boson in the vector-boson fusion channel and two same-charge W bosons in the vectorboson scattering channel. These measurements are compared to (N)NLO predictions of the Standard Model and provide model-independent constraints on new physics, by setting limits on anomalous gauge-boson couplings.An analysis of the inclusive four-lepton lineshape has been carried out in the mass range from 80 to 1000 GeV, where several distinct physics processes give rise to the production of 4-lepton final state, namely the single Z resonant processes, the Higgs production at 125 GeV, as well as continuum ZZ production processes with qq and gg initial states.

Multiboson production in W ′ decays

In models with an extra $\text{SU}(2)_R$ gauge group and an extended scalar sector, the cascade decays of the $W'$ boson can provide various multiboson signals. In particular, diboson decays $W' \to WZ$ can be suppressed while $W' \to WZX$, with $X$ one of the scalars present in the model, can reach branching ratios around 4%. We discuss these multiboson signals focusing on possible interpretations of the ATLAS excess in fat jet pair production.

Recent results on Electroweak measurements from ATLAS

ATLAS measurements of multiboson production processes involving combinations of W,Z and isolated photons are summarized. Measurements using data at 7 TeV and at 8 TeV are presented. The measurements are performed using leptonic decay modes, including the invisible decay Z → v v̅, as well as semileptonic channels. Measurements of single and diboson production in association with two forward jets is sensitive to electroweak vector boson fusion and scattering processes. An observation of the electroweak production of the Z boson and an evidence of same sign WW production are reported.

Recent results on Electroweak measurements from ATLAS

ATLAS measurements of multiboson production processes involving combinations of W,Z and isolated photons are summarized. Measurements using data at 7 TeV and at 8 TeV are presented. The measurements are performed using leptonic decay modes, including the invisible decay Z → v v̅, as well as semileptonic channels. Measurements of single and diboson production in association with two forward jets is sensitive to electroweak vector boson fusion and scattering processes. An observation of the electroweak production of the Z boson and an evidence of same sign WW production are reported.

Standard model measurements with ATLAS (+CMS) detector(s)

We present a broad range of Standard Model measurements performed in proton-proton collisions at the LHC on a variety of topics [Formula: see text]jets production and ratios, the electroweak multi-boson production, [Formula: see text] heavy flavor decay production, jet production, photon physics, the Standard Model soft QCD and diffractive physics. The latest public results from ATLAS experiment are obtained at the center-of-mass energy of both 7 TeV and 8 TeV, which covers total cross sections, fiducial cross sections, differential cross sections wherever available and comparison with Leading-Order/Next-to-Leading-Order/Next-to-Next-to-Leading-Order theory predictions. These measurements provide important tests for perturbative QCD, electroweak multi-boson interactions, Electroweak Symmetry Breaking over a broad kinematic range and constraints for PDFs. Model-independent new physics searches are also performed by probing anomalous gauge bosons couplings using effective Lagrangian or effective field theory formalism.

Recent Results from the CMS Experiment at the LHC

Numerous studies on Jet Production, Vector Boson Production, V+Jets Production and Multi-Boson Production have been carried out by the Compact Muon Solenoid (CMS) Collaboration to test perturbative quantum chromodynamics (QCD) pre- dictions, and to put more stringent constraints on PDFs (Parton Distribution Functions). In this paper, some of these experimental results will be presented, and their possible impacts on Higgs physics and new physics searches will be discussed.

Electroweak results from CMS

The latest electroweak results from CMS, based on pp collision data taken at 7 and 8 TeV, are presented. In particular precise measurements of the inclusive and differential cross sections for W and Z boson production, and for multi-boson production are reviewed and compared with theory predictions. Results agree with Standard Model and limits are set on anomalous triple gauge couplings.

Multiple-weak-boson signals at hadron supercolliders.

Multiple-weak-boson signals expected at future hadron supercolliders from several sources will provide new ways to probe the underlying interactions. The production of {ital t{bar t}t{bar t}}, {ital t{bar t}} {ital H}{sup 0}, {ital H}{sup 0}{ital H0}, {ital t{bar t}} {ital W}{sup +}{ital W{minus}}, {ital t{bar t}Z}{sup 0}{ital Z0}, Z{sup 0}{ital Z0}, {ital t{bar t}} {ital Z}{sup 0}, and {ital t{bar t}} {ital W}{sup {plus minus}} by standard-model mechanisms will lead to distinctive three-boson and four-boson signals via the decays {ital t}{r arrow}{ital bW} and {ital H}{sup 0}{r arrow}{ital W}{sup +}{ital W{minus}},{ital Z}{sup 0}{ital Z0},{ital t{bar t}},{gamma}{gamma}. In supersymmetric models the production and cascade decay of heavy gluinos can also give multiple {ital W} and {ital Z} configurations. We present calculations of these principal top-quark and Higgs-boson decay channels (plus some less important channels) and compare the resulting multi-weak-boson signals with backgrounds from direct multiboson production at energies of the Superconducting Super Collider and CERN Large Hadron Collider. We also present calculations of typical gluino cascade contributions. Since weak bosons are most readily identified through their leptonic decays, we also evaluate the principal signals and backgrounds at the lepton level. Within the standard model, the signals associated with strong top-quark productionmore » dominate completely over electroweak contributions; the expected event rates are large if we do not insist on all-leptonic {ital W} and {ital Z} decays. In the minimum supersymmetric standard model, gluino cascade decays can lead to still higher event rates; top-quark channels are typically important contributors here too.« less

Strong high-energy scattering in theories with weak coupling.

The problem of the existence of strong nonperturbative scattering at high energy in theories with weak coupling is considered. It is shown that such scattering associated with multiboson production definitely exists in practically any theory with self-interacting bosons. An approach to this problem is proposed which is based on explicit splitting of the short-wave and the long-wave modes of the bosonic field and considering the process of excitation by the initial particles of the long-wave field to states with large energy. The nonperturbative analysis of the probability of excitation of the soft field to a large amplitude is based on the WKB technique developed in quantum mechanics for similar problems. It is also shown that the results of previous calculations can be reproduced within the proposed approach including those based on the analysis of instanton-induced amplitudes.

From two to three jets in heavy boson decays: An algorithmic approach

The relation between two- and three-jet decays of vector particles is re-examined, with emphasis on the Monte Carlo simulation of multi-boson production processes such as e +e - → W +W -. An extremely simple algorithm is presented which allows one to include an extra gluon jet in two-jet decays while obtaining both momentum conservation and the correct angular correlations described by the complete vector boson production and three-jet decay amplitude.