Investigating perturbative unitarity in the presence of anomalous couplings

Dahiya, Mamta; Dutta, S.; Islam, Rashidul

doi:10.1103/physrevd.93.055013

Cited by 11 publications

(16 citation statements)

References 60 publications

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“…A study somewhat similar in approach, assuming that the SM vertices may allow some deviations from their predicted values, through possibly higher-order interactions, was undertaken in Refs. [30,31].…”

Section: Introductionmentioning

confidence: 99%

Scattering unitarity with effective dimension-6 operators

Ghosh

Islam

Kundu

2017

J. Phys. G: Nucl. Part. Phys.

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The effects of physics beyond the Standard Model may be parametrized by a set of higherdimensional operators leading to an effective theory. The introduction of these operators makes the theory nonrenormalizable, and one may reasonably expect a violation of unitarity in 2 → 2 scattering processes, depending on the values of the Wilson coefficients of the higher dimensional operators. Bounds on these coefficients may be obtained from demanding that there be no such unitarity violation below the scale of the effective theory. We show, at the lowest level, how the new operators affect the scattering amplitudes with longitudinal gauge bosons, scalars, and tt in the final state, and find that one may expect a violation of unitarity even at the LHC energies with small values of some of the new Wilson coefficients. For most of the others, such a violation needs large coefficients, indicating nonperturbative physics for the ultraviolet-complete theory, although a proper treatment necessitates the inclusion of even higher-dimensional operators. However, deviations from the Standard Model expectations may be observed with even smaller values for these coefficients. We find that W W → W W , W W → ZZ, and ZZ → hh scatterings are the best possible channels to probe unitarity violations.

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Section: Introductionmentioning

confidence: 99%

Scattering unitarity with effective dimension-6 operators

Ghosh

Islam

Kundu

2017

J. Phys. G: Nucl. Part. Phys.

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“…These conditions are equivalent to those in Refs. [79,103,104], if only 2 → 2 processes are considered.…”

Section: B Details For the Derivation Of Unitarity Constraintsmentioning

confidence: 99%

Multi-Higgs boson production and unitarity in vector-boson fusion at future hadron colliders

et al. 2020

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We study multi-Higgs final states in vector boson fusion (VBF) processes at the LHC and at future proton-proton colliders, focusing on the prospects for measurements at 27 TeV and at 100 TeV. We use an effective Lagrangian which includes higher-dimensional operators in the mass eigenstates which are relevant to VBF processes and relate this to specific param-At the LHC, the dominant SM process of multi-Higgs production is gluon-gluon-fusion (ggF) via a heavy top-quark loop. Current LHC data constrain the triple Higgs self-coupling only very weakly [3], and not at all the quartic Higgs self-coupling. Multiple groups have evaluated the potential for a first meaningful measurement of the triple Higgs self-coupling at future highluminosity runs of the LHC [4-10]. The considered decay channels of the Higgs pair include and bbbb [18, 22, 23]. It is expected that the triple self-coupling can be constrained within 40% accuracy after collecting 3 ab −1 of data at the 14 TeV LHC [24]. There will be no access to the quartic self-coupling. Beyond the LHC, at a future 100 TeV hadron collider, the Higgs pair-production rate is enhanced significantly [9,13,[25][26][27][28][29][30], allowing for a more accurate determination of the Higgs potential.A subdominant process of multi-Higgs production in hadron collisions is vector-bosonfusion (VBF) [31], W + W − → hh, where the W bosons are effectively radiated from incoming quarks. In addition to its dependence on the Higgs self-interaction, this process also gives access to the hhW W coupling, which is another SM interaction that has not been accessible by other means. In fact, the hVV (V = W ± , Z ) couplings can be derived from the precise measurement of the decay branching fractions h → W W * and h → Z Z * at the LHC, up to a common normalization factor. The current LHC data on the decay branching fractions for these channels are consistent with the SM predictions [32, 33]. By contrast, there are no significant constraints from data on hhV V direct couplings.The VBF mode of double-Higgs production at hadron colliders has been studied in Refs. [34][35][36][37][38]. Beyond tree level, the NLO QCD correction enhances the cross section by ∼ 7% [39,40]. In the high-luminosity mode of the LHC (HL-LHC) with 3000 fb −1 at 14 TeV, the hhV V interaction can be constrained to 20%. A 100 TeV hadron collider has the potential to reduce the uncertainty down to 1% [37]. The hhW W coupling is also accessible in the W ± W ± h final state. In Ref. [41] it is found that this particular final state can constrain this coupling to O(100%) at the HL-LHC, and to 20% at a 100 TeV collider.The other modes of double Higgs production are tt hh or V hh production. The production rates of these mode are smaller than ggF and VBF mode. The discussion of these modes is beyond the scope of current work. For interested readers, we refer to [39,40,[42][43][44][45][46][47][48].Measuring the quartic Higgs self-coupling in the SM is a much more challenging task. At the 14 TeV LHC, the cross section of g g → hhh is onl...

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“…where qq ′ + q ′ constitute the sea quarks [91][92][93][94][95][98][99][100][101][102][103][104][105][106][107][108]. The GB field can be expressed in terms of the GBs and their transition probabilities as…”

Section: Model (χCqm)mentioning

confidence: 99%

“…Even though many experimental and theoretical efforts have been made to understand the internal structure of the hadrons and origin of the sea quarks , the effective interaction Lagrangian approach of the strong interactions used in the chiral constituent quark model (χCQM) [88][89][90][91][92][93][94][95][96][97] successfully explains the spin structure of the nucleon [98][99][100][101][102][103][104][105][106][107][108], magnetic moments of octet and decuplet baryons [109,110], semileptonic weak decay parameters [111,112], magnetic moments of nucleon resonances and Λ resonances [113,114], quadrupole moment and charge radii of octet baryons [115,116], etc.. The inclusion of Q 2 dependence in the vector and axial-vector form factors can be done through the dipole form of parametrization as…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic and axial-vector form factors of the quarks and nucleon

Dahiya

Randhawa

2017

Int. J. Mod. Phys. A

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In light of the improved precision of the experimental measurements and enormous theoretical progress, the nucleon form factors have been evaluated with an aim to understand how the static properties and dynamical behavior of nucleons emerge from the theory of strong interactions between quarks. We have analysed the vector and axial-vector nucleon form factors (G p,n E,M (Q 2 ) and G p,n A (Q 2 )) using the spin observables in the chiral constituent quark model (χCQM) which has made a significant contribution to the unraveling of the internal structure of the nucleon in the nonperturbative regime. We have also presented a comprehensive analysis of the flavor decomposition of the form factors (G q E (Q 2 ), G q M (Q 2 ) and G q A (Q 2 )for q = u, d, s) within the framework of χCQM with emphasis on the extraction of the strangeness form factors which are fundamental to determine the spin structure and test the chiral symmetry breaking effects in the nucleon. The Q 2 dependence of the vector and axial-vector form factors of the nucleon has been studied using the conventional dipole form of parametrization. The results are in agreement with the available experimental data.

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Investigating perturbative unitarity in the presence of anomalous couplings

Cited by 11 publications

References 60 publications

Scattering unitarity with effective dimension-6 operators

Scattering unitarity with effective dimension-6 operators

Multi-Higgs boson production and unitarity in vector-boson fusion at future hadron colliders

Electromagnetic and axial-vector form factors of the quarks and nucleon

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