Eγ Colliders Research Articles

Single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity

Introducing the top partner is a common way to cancel the largest quadratically divergent contribution to the Higgs mass induced by the top quark. In this work, we study single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity (LHT). Since it is well known that polarized beams can enhance the cross section, we analyze the signal via polarized electron beams, and photon beams. we have selected two decay modes for comparison, based on the leptonic or the hadronic decays of the W and Z from the top partner. We then construct a detailed detector simulation, and choose a set of cuts to enhance signal significance. For mode A(B), the capacity for exclusion in this process at = 3 TeV is comparable to the current experimental limits with L = 1000 (500) fb−1. If the integrated luminosity can be increased to 3000 fb−1, the top partner mass can be excluded up to 1350 (1440) GeV at 2σ level. We also considered the initial state radiation effect, and find that this effect reduces the excluding ability of the eγ collision on the the top partner mass by approximately 10 GeV. Moreover, the ability to exclude the LHT parameter space at eγ collision complements the existing research.

Search for vector-like T quark through th channel at eγ collider

In an extension of the Standard Model with vector-like top partner, we investigate the vector-like top quark partner T via the channel e−γ→bνeT¯(→t¯h) at future linear collider. Due to the larger production rates than unpolarized beams, we calculate the production cross sections in polarized beams at s=2 and 3 TeV. We make a fast detector simulation for signal and background events and take a set of appropriate kinematic variables to enhance the signal significance. When the initial state radiation and beamstrahlung effects are in charge, we find that the correlated region g⁎∈[0.33,0.5] ([0.14,0.5]) and mT∈[1300GeV,1480GeV] ([1300GeV,1900GeV]) can be excluded at 2σ level with the integrated luminosity 600fb−1 (3000fb−1) at s=2 TeV. When the center-mass energy s is upgraded to 3 TeV, the excluded region is expanded to g⁎∈[0.3,0.5] ([0.14,0.5]) and mT∈[1300GeV,1940GeV] ([1300GeV,2000GeV]) with the integrated luminosity 600fb−1 (3000fb−1). Besides, we find the 5σ discovery correlated region is g⁎∈[0.30,0.5] ([0.27,0.5]) and mT∈[1300GeV,1500GeV] ([1300GeV,2000GeV]) with the integrated luminosity 3000fb−1 at s=2 TeV (3 TeV).

Single production of vector-like top partner in the Wb channel at eγ collision in the LHT model

In the framework of the littlest Higgs Model with T-parity (LHT), we investigate the single production of vector-like top partner [Formula: see text] decaying to [Formula: see text] in the leptonic channel at the high energy [Formula: see text] collision. We utilize the polarized electron beam and photon beam to enhance the signal and propose a search strategy by performing a detector simulation. On the basis of the current limits from the precision electroweak data and Higgs data, we find that the top partner mass can be excluded up to 1350 (1380) GeV with integrated luminosity of 1000 fb[Formula: see text] and 1400 (1470) GeV with integrated luminosity of 3000 fb[Formula: see text] for the [Formula: see text] TeV (2.4 TeV) at the [Formula: see text] level. If the center-of-mass energy can be improved to 3.0 TeV, the limits on the top partner mass will reach 1450 (1550) GeV with integrated luminosities of 1000 (3000) fb[Formula: see text].

CP-odd Higgs boson production in eγ collisions

We investigate the CP-odd Higgs boson production via two-photon processes in eγ collisions. The CP-odd Higgs boson, which we denote as A0, is expected to appear in the Two-Higgs Doublet Models (2HDM) as a minimal extension of Higgs sector for which the Minimal Supersymmetric Standard Model (MSSM) is a special case. The scattering amplitude for eγ→eA0 is evaluated at the electroweak one-loop level. The dominant contribution comes from top-quark loops when A0 boson is rather light and tan⁡β is not large. There are no contributions from the W-boson and Z-boson loops nor the scalar top-quark (stop) loops. The differential cross section for the A0 production is analyzed.

Non-standard Higgs couplings in single Higgs boson production at the LHC and future linear collider

We investigate the potential of single Higgs boson photoproduction at the LHC and at eγ mode of future linear e−e+ collider to probe non-standard HZγ and Hγγ couplings. We consider the semi-elastic production process pp → pγp → pHqX at the LHC where q represents the quarks and X represents the remnants of one of the initial protons. We also study the single Higgs production through γe → He in the eγ collision at the future linear collider. We perform a model-independent analysis and obtain the sensitivity bounds on the non-standard Higgs couplings for both colliders. We compare the capability of single Higgs photoproduction process at these two colliders to probe non-standard Higgs couplings.

Lepton flavor violating Higgs couplings and single production of the Higgs boson via eγ collision

Taking into account the constraints on the lepton flavor violation (LFV) couplings of the Standard Model (SM) Higgs boson H with leptons from low energy experiments and the recent Compact Muon Solenoid experiment results, we investigate production of the SM Higgs boson associated with a lepton τ via eγ collision at the International Linear Collider (ILC) and Large Hadron Electron Collider experiments. The production cross sections are calculated and the LFV signals and the relevant SM backgrounds are examined. The LFV signals of the SM Higgs boson might be observed via eγ collision in future ILC experiments.

Single vector-like top partner production in the left-right twin Higgs model at TeV energy eγ colliders

The left-right twin Higgs model contains a new vector-like heavy top quark, which mixes with the SM-like top quark. In this work, we studied the single vector-like top partner production via process e−γ → νeT̄b at the International Linear Collider. We calculated the production cross section at tree level and displayed the relevant differential distributions. The result shows that there will be 125 events produced each year with √s=2 TeV and the integrated luminosity ℒint ≈ 500 fb−1, and the b-quark tagging and the relevant missing energy cut will be helpful to detect this new effect.

SINGLE PRODUCTION OF THE GAUGE BOSONS VIA eγ COLLISION AT THE HIGH ENERGY e+e- LINEAR COLLIDERS

The eγ collider is better suited to study single production of the gauge bosons. In this paper, we first consider the contributions of the three-site Higgsless (3SHL) model and the left–right twin Higgs (LRTH) model to the standard model (SM) processes eγ→eZ and eγ→νeW, and then study single production of the new neutral and charged gauge bosons predicted by these two models via eγ collision in the future high energy e+e- linear collider experiments. We find that the correction effects of 3SHL model on the processes eγ→eZ and eγ→νeW might be detected in the future, while this is not the case for the LRTH model. The process eγ→eZ' can give rise to different signatures in the 3SHL and LRTH models and thus can be used to distinguish these two kinds of new physics models at the high energy e+e- linear colliders.

Production of the doubly charged leptons at the high-energy linear e+e− colliders

We consider production of the doubly charged leptons X±± via e+e−, γγ and eγ collisions at the high-energy linear e+e− colliders. It is found that, due to the smallness of the mixing parameter ve, the production cross section for the subprocess eγ → X−−W+ is too small to be used to study the possible signatures of the doubly charged leptons. However, the processes and , are not this case. As long as the doubly charged leptons are not too heavy, they can be abundantly produced via these two processes at the high-energy linear e+e− colliders.

Single Production of Doubly Charged Higgs Boson via eγ Collision in Higgs Triplet Model

The Higgs triplet model (HTM) predicts the existence of a pair of doubly charged Higgs bosons H±±. Single production of H±± via eγ collision at the next generation e+e− International Linear Collider (ILC) and the Large Hadron electron Collider (LHeC) is considered. The numerical results show that the production cross sections are very sensitive to the neutrino oscillation parameters. Their values for the inverted hierarchy mass spectrum are larger than those for the normal hierarchy mass spectrum at these two kinds of collider experiments. With reasonable values of the relevant free parameters, the possible signals of the doubly charged Higgs bosons predicted by the HTM might be detected in future ILC experiments.

Probing Topcolor-Assisted Technicolor Models from Like-Sign τ Pair Production in eγ Collisions

We consider the contributions of the extra gauge boson Z′ to the like sign τ production processes e−γ → e+(μ+)τ−τ−, induced by the tree-level flavor changing interactions. Since these rare production are far below the observable level in the Standard Model and other popular new physics models such as the minimal supersymmetric model, we find that, in the topcolor-assisted technicolor models, the Z′ can give significant contributions to these processes, and with reasonable values of the parameters, the cross section σ can reach several tens of fb and may be detected at the eγ collisions.

Production of Charged Higgs Bosons from Left-Right Twin Higgs Model at TeV Energy e−γ Colliders

The left-right twin Higgs (LRTH) model predicts the existence of three additional Higgs bosons: one neutral Higgs φ0 and a pair of charged Higgs bosons φ±. In this paper, we study two pair production processes of these new particles at the next generation eγ colliders, i.e., e−γ→ e−φ+φ−, and e−γ→ νRφ−φ0. We find that the production cross section of the process e−γ→ e−φ+φ− are at the level of several tens fb, the production cross section of the process e−γ→ νRφ−φ0 can reach 0.35 fb with the reasonable parameter values. As long as the charged Higgs bosons are not too heavy, we conclude that these processes might be used to test for the left-right twin Higgs model in future high-energy linear collider experiments.

Lepton flavor violation production of new particles from a topcolor scenario via eγ collision

The topcolor scenario generally predicts the existence of the neutral top-pion π0t and the nonuniversal gauge boson Z′, which have flavor changing couplings to ordinary fermions at tree-level. Taking into account the constraints of the lepton flavor violation (LFV) processes μ → eγ and μ → 3e on the relevant free parameters, we consider production of these new particles via the LFV processes eγ → τπ0t and eγ → τZ′ at the international linear e+e− collider (ILC) experiments. We find that the effective cross section for the LFV process eγ → τπ0t is smaller than 0.2fb. While, the effective cross section of the LFV process eγ → τZ′ can reach 12.2fb with reasonable values of the free parameters.

CP-violating WWγ couplings in eγ collision with polarized beams

We investigate the constraints on CP-violating triple WWγ gauge boson couplings through the process eγ→Wνe. Considering the longitudinal and transverse polarization states of the final W and incoming polarized beams, we find 95% confidence level limits on CP odd anomalous coupling parameters and with an integrated luminosity of 500 fb−1 and and 1.5 TeV energies. It is shown that the initial and final state polarizations improve the sensitivity limits of by a factor of 1.3–1.6 and of by a factor of 5.2–9.

TOP QUARK SPIN POLARIZATION IN eγ COLLISION

We investigate the degree of spin polarization of single top quarks in the eγ collision via the process [Formula: see text] with center-of-mass energies [Formula: see text], 1 and 1.5 TeV of the parental linear e+e- collider. Dominant spin fractions and spin asymmetries for the various top quark spin bases are investigated. We show that e+-beam direction is the favorite top quark spin decomposition axis. It is found to be comparable with the ones in pp and ep collisions.

Polarized single top quark production in eγ collision and anomalous Wtb couplings

We investigate the potential of eγ collisions to probe anomalous Wtb couplings via the polarized single top quark production process e+γ→tbνe. We find 95% confidence level limits on the anomalous coupling parameters F2L and F2R with an integrated luminosity of 500 fb-1 and $\sqrt{s}=0.5$ , 1 and 1.5 TeV energies. The effects of top quark spin polarization on the anomalous Wtb couplings are discussed. It is shown that polarization leads to a considerable improvement in the sensitivity limits.

WZ production at eγ colliders and anomalous quartic WWZγ coupling

We investigate the constraints on the anomalous quartic W+W−Zγ gauge boson coupling through the process e−γ → νeW−Z. Considering incoming beam polarizations and the longitudinal and transverse polarization states of the final W and Z boson we find 95% confidence level limits on the anomalous coupling parameter an with an integrated luminosity of 500 fb−1 and = 0.5, 1 TeV energies. We show that initial beam and final state polarizations improve the sensitivity to the anomalous coupling by up to factors of 2–3.5 depending on the energy.

Production of the charged top-pions from TC2 model at the TeV energy e-γ colliders

The top-pions (Πt0,±) and the top-Higgs (ht0) are the typical particles predicted by the topcolor-assisted technicolor (TC2) model and the observation of these particles can be regarded as direct evidence of the TC2 model. In this paper, we study three pair production processes of these new particles at the next generation eγ colliders, i.e., e-γ→e-Πt+Πt-, e-γ→νeΠt-Πt0 and e-γ→νeΠt-ht0. The results show that the production rates can reach the level 100–101 fb with reasonable parameter values. So one can expect that enough signals could be produced in future high- energy linear collider experiments. Furthermore, the flavor-changing (FC) decay modes Πt-→bc, Πt0(ht0)→tc can provide us with the typical signal to detect these new particles.

Probing anomalous Higgs couplings at an eγ collider using unpolarised beams

We examine the sensitivity of eγ colliders (based on e + e − linear colliders of c.m. energy 500 GeV) to the anomalous couplings of the Higgs to W-boson via the process e − γ → νWH. This has the advantage over e + e − collider in being able to dissociate WWH vertex from ZZH. We are able to construct several dynamical variables which may be used to constrain the various couplings in the WWH vertex.

Two photon at future linear colliders

Abstract The physics potential of γγ and eγ collisions at future linear collisions is discussed.