Anomalous Quartic Couplings Research Articles

Search for anomalous quartic WWZγ couplings at the future linear e+e− collider

In this paper, the potentials of two different processes [Formula: see text] and [Formula: see text] at the Compact Linear Collider (CLIC) are examined to probe the anomalous quartic [Formula: see text] gauge couplings. For [Formula: see text], 1.5 and 3[Formula: see text]TeV energies at the CLIC, 95% confidence level limits on the anomalous coupling parameters defining the dimension-six operators are found via the effective Lagrangian approach in a model independent way. The best limits on the anomalous couplings [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] which can be achieved with the integrated luminosity of [Formula: see text] at the CLIC with [Formula: see text] are [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], respectively.

Anomalous quartic ZZγγ couplings at the CLIC

We study the sensitivity to anomalous quartic $ZZ\gamma\gamma$ couplings through the processes $e^{+}e^{-}\rightarrow Z\, Z\, \gamma$, $e^{+}e^{-} \rightarrow e^{+}\gamma^{*} e^{-} \rightarrow e^{+} Z\, Z\, e^{-}$ and $e^{+}e^{-} \rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+}\, Z\, Z\, e^{-}$ at the CLIC. We find $95\%$ confidence level bounds on these coupling parameters defining by the dimension-six operators. The best bounds on the anomalous $ZZ\gamma\gamma$ couplings among the three processes are obtained from $e^{+}e^{-}\rightarrow Z\, Z\, \gamma$ at a center of mass energy of $3$ TeV and an integrated luminosity of $590$ fb$^{-1}$. We show that the best bounds obtained on both the anomalous coupling parameters are of the order of $10^{-8}$ GeV$^{-2}$, significantly improving the current bounds.

Probe of anomalous quartic WWZγ couplings in photon-photon collisions

In this paper, we examine the potentials of the processes $\gamma \gamma\rightarrow W^{+} W^{-}Z $ and $e^{+}e^{-} \rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+} W^{+} W^{-} Z e^{-}$ at the CLIC with $\sqrt{s}=0.5,1.5$ and $3$ TeV to investigate anomalous quartic $WWZ\gamma$ couplings by two different CP-violating and CP-conserving effective Lagrangians. We find $95\%$ confidence level limits on the anomalous coupling parameters at the three CLIC energies and various integrated luminosities. The best limits obtained from the process $\gamma \gamma\rightarrow W^{+} W^{-}Z $ on the anomalous $\frac{k_{0}^{W}}{\Lambda^{2}}$, $\frac{k_{c}^{W}}{\Lambda^{2}}$ and $\frac{k_{2}^{m}}{\Lambda^{2}}$ couplings defined by CP-conserving effective Lagrangians are $[-1.73;\, 1.73]\times 10^{-7}$ GeV$^{-2}$, $[-2.44;\, 2.44]\times 10^{-7}$ and $[-1.89; \, 1.89]\times 10^{-7}$ GeV$^{-2}$, while $\frac{a_{n}}{\Lambda^{2}}$ coupling determined by CP-violating effective Lagrangians is obtained as $[-1.74;\, 1.74]\times 10^{-7}$ GeV$^{-2}$. In addition, the best limits derived on $\frac{k_{0}^{W}}{\Lambda^{2}}$, $\frac{k_{c}^{W}}{\Lambda^{2}}$ and $\frac{k_{2}^{m}}{\Lambda^{2}}$ and $\frac{a_{n}}{\Lambda^{2}}$ from the process $e^{+}e^{-} \rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+} W^{+} W^{-} Z e^{-}$ are obtained as $[-1.09;\, 1.09]\times 10^{-6}$ GeV$^{-2}$, $[-1.54;\, 1.54]\times 10^{-6}$ GeV$^{-2}$, $[-1.18;\, 1.18]\times 10^{-6}$ and $[-1.04;\, 1.04]\times 10^{-6}$ GeV$^{-2}$, respectively.

Analysis of anomalous quartic WWZγ couplings in γp collision at the LHC

Gauge boson self-couplings are exactly determined by the non-Abelian gauge nature of the Standard Model (SM), thus precision measurements of these couplings at the LHC provide an important opportunity to test the gauge structure of the SM and the spontaneous symmetry breaking mechanism. It is a common way to examine the physics of anomalous quartic gauge boson couplings via effective Lagrangian method. In this work, we investigate the potential of the process pp→pγp→pWZqX to analyze anomalous quartic WWZγ couplings by two different, CP-violating and CP-conserving, effective Lagrangians at the LHC. We calculate 95% confidence level limits on the anomalous coupling parameters with various values of the integrated luminosity. Our numerical results show that the best limits obtained on the anomalous couplings k0WΛ2, kcWΛ2, k2mΛ2 and anΛ2 at s=14 TeV and an integrated luminosity of Lint=100 fb−1 are [−1.37;1.37]×10−6 GeV−2, [−1.88;1.88]×10−6 GeV−2, [−6.55;6.55]×10−7 GeV−2 and [−2.21;2.21]×10−6 GeV−2, respectively. Thus, γp mode of photon-induced reactions at the LHC highly improves the sensitivity limits of the anomalous coupling parameters k0WΛ2, kcWΛ2, k2mΛ2 and anΛ2.

Anomalous coupling studies at the LHC with proton tagging

We present the photon induced processes leading to intact protons at the final state that can be studied at the LHC. We give the cross section predicted by the standard model for W and photon pair production. The study of these processes lead to unprecedented sensitivities on quartic anomalous couplings between photons and W, Z bosons, reaching the values expected for extra dimension models. In this short report, we discuss some potential mea- surements to be performed using proton tagging detectors at the LHC. The main motivation is to explore rare events, searching for beyond standard model physics such as quar- tic anomalous couplings between photons and W/Z bosons and photons. We assume in the following intact protons to be tagged in dedicated detectors located at about 210 m for ATLAS (220 m for CMS) as described in Ref. (1). In the first part of this report, we discuss the Standard Model (SM) production of W and γ pairs at the LHC via photon exchanges. In the second, third and fourth sections, we discuss the sensitivities of these processes to quartic gauge anomalous couplings.

Photon induced processes at the LHC

We discuss the photon-induced processes that can be studied at the LHC, leading to intact protons in the final state. We give the SM cross-section for W- and photon-pair production. These processes lead to unprecedented sensitivities on quartic anomalous couplings between photons and W and Z bosons, reaching the values expected for extra dimension models.

Probing new physics in diphoton production with proton tagging at the Large Hadron Collider

The sensitivities to anomalous quartic photon couplings at the Large Hadron Collider are estimated using diphoton production via photon fusion. The tagging of the protons proves to be a very powerful tool to suppress the background and unprecedented sensitivities down to $7\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}15}\text{ }{\mathrm{GeV}}^{\ensuremath{-}4}$ are obtained, providing a new window on extra dimensions and strongly interacting composite states in the multi-TeV range. Generic contributions to quartic photon couplings from charged and neutral particles with arbitrary spin are also presented.

Forward physics with proton tagging at the LHC

We present some inclusive and exclusive diffractive processes to be studied at the LHC, namely QCD, quartic anomalous couplings between γ and W/Z bosons and diffractive Higgs processes.

Causality, analyticity and an IR obstruction to UV completion

We argue that certain apparently consistent low-energy effective field theories described by local, Lorentz-invariant Lagrangians, secretly exhibit macroscopic non-locality and cannot be embedded in any UV theory whose S-matrix satisfies canonical analyticity constraints. The obstruction involves the signs of a set of leading irrelevant operators, which must be strictly positive to ensure UV analyticity. An IR manifestation of this restriction is that the "wrong" signs lead to superluminal fluctuations around non-trivial backgrounds, making it impossible to define local, causal evolution, and implying a surprising IR breakdown of the effective theory. Such effective theories can not arise in quantum field theories or weakly coupled string theories, whose S-matrices satisfy the usual analyticity properties. This conclusion applies to the DGP brane-world model modifying gravity in the IR, giving a simple explanation for the difficulty of embedding this model into controlled stringy backgrounds, and to models of electroweak symmetry breaking that predict negative anomalous quartic couplings for the W and Z. Conversely, any experimental support for the DGP model, or measured negative signs for anomalous quartic gauge boson couplings at future accelerators, would constitute direct evidence for the existence of superluminality and macroscopic non-locality unlike anything previously seen in physics, and almost incidentally falsify both local quantum field theory and perturbative string theory.

Constraints on anomalous quartic gauge boson couplings fromνν¯γγandqq¯γγevents at CERN LEP2

Anomalous quartic couplings between the electroweak gauge bosons may contribute to the nu(nu) over bar gammagamma and q (q) over bar gammagamma final states produced in e(+)e(-) collisions. This analysis uses the LEP2 OPAL data sample at center-of-mass energies up to 209 GeV. Event selections identify nu(nu) over bar gammagamma and q (q) over bar gammagamma events in which the two photons are reconstructed within the detector acceptance. The cross section for the process e(+)e(-)-->q (q) over bar gammagamma is measured. Averaging over all energies, the ratio of the observed e(+)e(-)-->q (q) over bar gammagamma cross section to the standard model expectation is R(data/SM)=0.92+/-0.07+/-0.04, where the errors represent the statistical and systematic uncertainties respectively. The nu(nu) over bar gammagamma and q (q) over bar gammagamma data are used to constrain possible anomalous W(+)W(-)gammagamma and ZZgammagamma couplings. Combining with previous OPAL results from the W(+)W(-)gamma final state, the 95% confidence level limits on the anomalous coupling parameters a(0)(Z), a(c)(Z), a(0)(W) and a(c)(W) are found to be -0.007 GeV-2<a(0)(Z)/Lambda(2)<0.023 GeV-2, -0.029 GeV-2<a(c)(Z)/Lambda(2)<0.029 GeV-2, -0.020 GeV-2<a(0)(W)/Lambda(2)<0.020 GeV-2, -0.052 GeV-2<a(c)(W)/Lambda(2)<0.037 GeV-2, where Lambda is the energy scale of the new physics. Limits found when allowing two or more parameters to vary are also presented.

RacoonWW1.3: A Monte Carlo program for four-fermion production at e +e − colliders

We present the Monte Carlo generator RacoonWW that computes cross sections to all processes e +e −→4 f and e +e −→4 fγ and calculates the complete O(α) electroweak radiative corrections to e +e −→WW→4 f in the electroweak Standard Model in double-pole approximation. The calculation of the tree-level processes e +e −→4 f and e +e −→4 fγ is based on the full matrix elements for massless (polarized) fermions. When calculating radiative corrections to e +e −→WW→4 f, the complete virtual doubly-resonant electroweak corrections are included, i.e. the factorizable and non-factorizable virtual corrections in double-pole approximation, and the real corrections are based on the full matrix elements for e +e −→4 fγ. The matching of soft and collinear singularities between virtual and real corrections is done alternatively in two different ways, namely by using a subtraction method or by applying phase-space slicing. Higher-order initial-state photon radiation and naive QCD corrections are taken into account. RacoonWW also provides anomalous triple gauge-boson couplings for all processes e +e −→4 f and anomalous quartic gauge-boson couplings for all processes e +e −→4 fγ.

Probing anomalous quartic couplings ineγ and γγ colliders

We analyze the potential of the ${e}^{+}{e}^{\ensuremath{-}}$ linear colliders, operating in the e\ensuremath{\gamma} and \ensuremath{\gamma}\ensuremath{\gamma} modes, to probe anomalous quartic vector-boson interactions through the multiple production of $W'\mathrm{s}$ and $Z'\mathrm{s}.$ We examine all ${\mathrm{SU}(2)}_{L}\ensuremath{\bigotimes}{U(1)}_{Y}$ chiral operators of order ${p}^{4}$ that lead to new four-gauge-boson interactions but do not alter trilinear vertices. We show that the e\ensuremath{\gamma} and \ensuremath{\gamma}\ensuremath{\gamma} modes are able not only to establish the existence of a strongly interacting symmetry breaking sector but also to probe for anomalous quartic couplings of the order of ${10}^{\ensuremath{-}2}$ at 90% C.L. Moreover, the information gathered in the $e\ensuremath{\gamma}$ mode can be used to reduce the ambiguities of the ${e}^{+}{e}^{\ensuremath{-}}$ mode.

Quartic anomalous couplings at LEP

The search for quartic anomalous gauge couplings at LEP requires appropriate predictions for the radiative processes e+ e- \to \nu\bar\nu \gamma\gamma, e+ e- \to q\bar{q}\gamma\gamma and e+ e- \to 4 fermions+\gamma. Matrix elements are exactly computed at the tree level, and the effects of anomalous couplings and initial-state radiation are included. Comparisons with results and approximations existing in the literature are shown and commented. Improved versions of the event generators NUNUGPV and WRAP are made available for experimental analysis.

Probing anomalous quartic gauge-boson couplings via $\mathrm{e^+e^-} \rightarrow 4$ fermions $+\gamma$

All lowest-order amplitudes for e+e- --> 4f+gamma are calculated including five anomalous quartic gauge-boson couplings that are allowed by electromagnetic gauge invariance and the custodial SU(2)_c symmetry. Three of these anomalous couplings correspond to the operators L_0, L_c, and L_n that have been constrained by the LEP collaborations in WWgamma production. The anomalous couplings are incorporated in the Monte Carlo generator RACOONWW. Moreover, for the processes e+e- --> 4f+gamma RACOONWW is improved upon including leading universal electroweak corrections such as initial-state radiation. The discussion of numerical results illustrates the size of the leading corrections as well as the impact of the anomalous quartic couplings for LEP2 energies and at 500GeV.

Anomalous quartic couplings in

The production of three electroweak gauge bosons in high-energy $e^+e^-$ collisions offers a window on anomalous quartic gauge boson couplings. We investigate the effect of three possible anomalous couplings on the cross sections for $W^+W^-\gamma$, $Z^0Z^0\gamma$ and $Z^0\gamma\gamma$ productions at LEP2 ($\sqrt{s} = 200$ GeV) and at a future linear collider ($\sqrt{s} = 500$ GeV). We find that the combination of energies and processes provides reasonable discrimination between the various anomalous contributions.

Anomalous quartic couplings in [formula omitted] production via WW-fusion at LEP2

The production of ν ν ̄ γγ in high-energy e + e − collisions offers a window on anomalous quartic gauge boson couplings. We investigate the effect of two possible anomalous couplings on the cross section for ν ν ̄ γγ production via WW-fusion at LEP2 ( s =200 GeV).

Radiation zeros in $W^+W^-\gamma$ production at high-energy colliders

The vanishing of the cross section for particular points in phase space - radiation zeros - is examined for the process $ q \bar q \to W^+W^- \gamma$ at high energy. Unlike the process $q \bar q' \to W^\pm \gamma$, actual zeros only occur in the soft-photon limit. However, for photon energies that are not too large, the cross section does exhibit deep dips in regions of phase space corresponding to the position of the actual zeros. We show that in these regions the sensitivity to possible anomalous quartic couplings is very large.

Strongly interacting vector bosons at the CERN LHC: Quartic anomalous couplings

We analyze the potential of the CERN Large Hadron Collider to study anomalous quartic vector-boson interactions through the production of vector-boson pairs accompanied by jets. In the framework of $\mathrm{SU}{(2)}_{L}\ensuremath{\bigotimes}\mathrm{U}{(1)}_{Y}$ chiral Lagrangians, we examine all effective operators of order ${p}^{4}$ that lead to new four-gauge-boson interactions but do not alter trilinear vertices. In our analyses, we perform the full tree-level calculation of the processes leading to two jets plus vector-boson pairs, ${W}^{+}{W}^{\ensuremath{-}}{,W}^{\ifmmode\pm\else\textpm\fi{}}{W}^{\ifmmode\pm\else\textpm\fi{}}{,W}^{\ifmmode\pm\else\textpm\fi{}}Z,$ or $ZZ,$ taking properly into account the interference between the standard model and the anomalous contributions. We obtain the bounds that can be placed on the anomalous quartic interactions and we study the strategies to distinguish the possible new couplings.

Tests of anomalous quartic couplings at the Next Linear Collider

We analyze the potential of the Next Linear $e^+e^-$ Collider to study anomalous quartic vector-boson interactions through the processes $e^+ e^- \to W^+W^-Z$ and $ZZZ$. In the framework of $SU(2)_L \otimes U(1)_Y$ chiral Lagrangians, we examine all effective operators of order $p^4$ that lead to four-gauge-boson interactions but do not induce anomalous trilinear vertices. In our analysis, we take into account the decay of the vector bosons to fermions and evaluate the efficiency in their reconstruction. We obtain the bounds that can be placed on the anomalous quartic interactions and we study the strategies to distinguish the possible couplings.

Anomalous quartic couplings in W+W- gamma production at e+e- colliders

We study the process e+e- to W+W- gamma at high-energy e+e- colliders to investigate the effect of genuine quartic W+W- gamma gamma and W+W-Z gamma anomalous couplings on the cross section. Deviations from the standard model predictions are quantified. We show how bounds on the anomalous couplings can be improved by choosing specific initial-state helicity combinations. The dependence of the anomalous contributions on the collider energy is studied.