Aspects of CP violation in the<i>HZZ</i>coupling at the LHC

Godbole, Rohini M.; Miller, D. J.; Mühlleitner, Margarete

doi:10.1088/1126-6708/2007/12/031

Cited by 118 publications

(82 citation statements)

References 84 publications

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“…The kinematics of the H → ZZ → 4 process, as well as for any boson decaying to ZZ, has been extensively studied in the literature [117][118][119][119][120][121][122][123][124][125][126][127][128][129]. Since the Higgs boson is spinless, the angular distribution of its decay products is independent of the production mechanism.…”

Section: Jhep06(2013)081mentioning

confidence: 99%

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2013

J. High Energ. Phys.

548

427

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A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb −1 at √ s = 7 TeV, and up to 5.3 fb −1 at √ s = 8 TeV. The results for five Higgs boson decay modes γγ, ZZ, WW, τ τ , and bb, which show a combined local significance of 5 standard deviations near 125 GeV, are reviewed. A fit to the invariant mass of the two high resolution channels, γγ and ZZ → 4 , gives a mass estimate of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The measurements are interpreted in the context of the standard model Lagrangian for the scalar Higgs field interacting with fermions and vector bosons. The measured values of the corresponding couplings are compared to the standard model predictions. The hypothesis of custodial symmetry is tested through the measurement of the ratio of the couplings to the W and Z bosons. All the results are consistent, within their uncertainties, with the expectations for a standard model Higgs boson. The CMS collaboration 106 Keywords: Hadron-Hadron Scattering IntroductionThe standard model (SM) [1-3] of particle physics accurately describes many experimental results that probe elementary particles and their interactions up to an energy scale of a few hundred GeV [4]. In the SM, the building blocks of matter, the fermions, are comprised of quarks and leptons. The interactions are mediated through the exchange of force carriers: the photon for electromagnetic interactions, the W and Z bosons for weak interactions, and the gluons for strong interactions. All the elementary particles acquire mass through their interaction with the Higgs field [5][6][7][8][9][10][11][12][13]. This mechanism, called the "Higgs" or "BEH" mechanism [5][6][7][8][9][10], is the first coherent and the simplest solution for giving mass to W and Z bosons, while still preserving the symmetry of the Lagrangian. It is realized by introducing a new complex scalar field into the model. By construction, this field allows the W and Z bosons to acquire mass whilst the photon remains massless, and adds to the model one new scalar particle, the SM Higgs boson (H). The Higgs scalar field and its conjugate can also give mass to the fermions, through Yukawa interactions [11][12][13] The discovery or exclusion of the SM Higgs boson is one of the primary scientific goals of the LHC. Previous direct searches at the LHC were based on data from protonproton collisions corresponding to an integrated luminosity of 5.1 fb −1 collected at a centreof-mass energy of 7 TeV. The CMS experiment excluded at 95% CL masses from 127 to 600 GeV [20]. The ATLAS experiment excluded at 95% CL the ranges 111. . Within the remaining allowed mass region, an excess of events between 2 and 3 standard deviations (σ) near 125 GeV was reported by both experiments. In 2012, the proton-proton centre-of-mass energy was increased to 8 TeV, and by the end of June, an...

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Section: Jhep06(2013)081mentioning

confidence: 99%

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2013

J. High Energ. Phys.

548

427

View full text Add to dashboard Cite

show abstract

“…Various strategies have been proposed for determining the spin and parity of a Higgs candidate in hadron-hadron collisions, including angular distributions and kinematic correlations in X → ZZ * , W W * and γγ decays [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Historically, the problem of determining the spin and parity of a Higgs candidate was first considered in the context of e + e − collisions, and the point was made that the threshold behaviour of the cross section for the 'Higgs'-strahlung process e + e − → Z + X would depend on the spin and parity of the X particle, offering potential discrimination between different spin-parity assignments [23].…”

Section: Introductionmentioning

confidence: 99%

A fast track towards the ‘Higgs’ spin and parity

Ellis

Hwang

Sanz

et al. 2012

J. High Energ. Phys.

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Abstract:The LHC experiments ATLAS and CMS have discovered a new boson that resembles the long-sought Higgs boson: it cannot have spin one, and has couplings to other particles that increase with their masses, but the spin and parity remain to be determined. We show here that the 'Higgs' + gauge boson invariant-mass distribution in 'Higgs'-strahlung events at the Tevatron or the LHC would be very different under the J P = 0 + , 0 − and 2 + hypotheses. Our analysis is based on simulations of the experimental event selections and cuts using PYTHIA and Delphes, and incorporates statistical samples of 'toy' experiments. The observation of 'Higgs'-strahlung at the Tevatron and the expected peaking of backgrounds at low invariant masses suggest that this process could provide a fast-track indicator of the 'Higgs' spin and parity.

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“…For the optimistic photon energy resolution, the significance increases to more than 3σ with L = 1 ab −1 and 5σ with L = 3 ab −1 at √ s = 350 GeV, and more than 2.1σ with L = 3 ab −1 and 4σ with L = 10 ab −1 at √ s = 500 GeV. (23) (23) In order to estimate whether the A F B can be measured at the future high luminosity e + e − colliders, we calculate the significance of the expected asymmetry with which a particular CP phase ξ would manifest [10] …”

Section: Collider Simulationmentioning

confidence: 99%

“…(26), which has been discussed partly in in [10,12,15,20,21].We define the theoretical asymmetry A FB and the measured asymmetry A meas FB as…”

Section: Box Diagram Contributionsmentioning

confidence: 99%

ProbingCP-violatinght¯tcoupling ine+e<

Wang

Zhu

2016

Phys. Rev. D

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We investigate the possibility of probing the CP-violating htt coupling in the process e + e − → hγ at the future high luminosity e + e − colliders. Our numerical results show that the cross section for this process can be significantly increased for the allowed CP phase ξ and center of mass energy. For example the cross section is about 10 times of that in the standard model (SM) for √ s = 350 GeV and ξ = 3π/5 (see text for ξ definition). The simulation for the signal process e + e − → hγ → bbγ and its backgrounds shows that the signal significance can reach about 5σ and more than 2.1σ for √ s = 350 GeV, 500 GeV respectively, with the integrated luminosity L = 3 ab −1 and ξ ∈ [π/2, 3π/5]. For L = 10 ab −1 , the signal significance can be greater than 5σ for √ s = 350 GeV and about 4σ for √ s = 500 GeV with the CP phase ξ ∈ [π/2, 3π/5]. Besides the cross section enhancement, the CPviolating htt coupling will induce a forward-backward asymmetry AF B which is absent in the SM and is a clear signal of new CP violation. Compared with the AF B in the Higgs decay h → l + l − γ, the AF B can be greatly enhanced in the production process. For example AF B can reach -0.55 for ξ = π/4 and √ s = 500 GeV. Due to the large backgrounds, the significance of the expected AF B can be only observed at 1.68σ with L = 10 ab −1 and √ s = 500 GeV. It is essential to trigger the single photon in the final state to separate the bottom jets arising from scalar or vector bosons, in order to isolate the signal from the backgrounds more efficiently.

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Aspects of CP violation in theHZZcoupling at the LHC

Cited by 118 publications

References 84 publications

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

A fast track towards the ‘Higgs’ spin and parity

ProbingCP-violatinght¯tcoupling ine+e<

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