Littlest Higgs Model With T-parity 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.

The full lepton flavor of the littlest Higgs model with T-parity

We re-examine lepton flavor violation (LFV) in the Littlest Higgs model with T-parity (LHT) including the full T-odd (non-singlet) lepton and Goldstone sectors. The heavy leptons induce two independent sources of LFV associated with the couplings necessary to give masses to the T-odd mirror fermions and to their partners in right-handed SO(5) multiplets, respectively. The latter, which have been neglected in the past, can be decoupled from gauge mediated processes but not from Higgs mediated ones and must therefore also be included in a general analysis of LFV in the LHT. We also further extend previous analyses by considering on-shell Z and Higgs LFV decays together with the LFV processes at low momentum transfer. We show that current experimental limits can probe the LHT parameter space up to global symmetry breaking scales f ∼ 10 TeV. For lower f values ≳ 1 TeV, μ − e transitions require the misalignment between the heavy and the Standard Model charged leptons to be ≲ 1%. Future LFV experiments using intense muon beams should be sensitive to misalignments below the per mille level. For τ LFV transitions, which could potentially be observed at Belle II and the LHC as well as future lepton colliders, we find that generically they can not discriminate between the LHT and supersymmetric models though in some regions of parameter space this may be possible.

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].

Single production of vectorlike top partner decaying to Wb in the leptonic channel at ep colliders in the littlest Higgs model with T-parity

In the littlest Higgs model with T-parity(LHT), we study the single production of vector-like top partner with the subsequent decay $T_{+}\to Wb$ in the leptonic channel at the $ep$ colliders. Focus on the LHeC ($ \sqrt{s} $ = 1.98 TeV) and FCC-eh ($ \sqrt{s} $ = 5.29 TeV), we investigate the observability of the single top partner production with the unpolarized and polarized electron beams, respectively. As a result, the statistical significance can be enhanced by the polarized electron beams. Under the current constraints, the search for $T_{+}$ in the $Wb$ channel at the LHeC cannot provide a stronger limit on the top partner mass. By contrast, the search for the $T_{+}$ in this channel at the FCC-eh with polarized $ e^- $ beams can exclude the top partner mass up to 1350 GeV, 1500 GeV and 1565 GeV with integrated luminosities of 100 fb$^{-1}$, 1000 fb$^{-1}$ and 3000 fb$^{-1}$ at the 2$\sigma$ level, which is an improvement with respect to the current indirect searches and the LHC direct searches. Furthermore, we also give an extrapolation to the high-luminosity LHC with $\sqrt{s}=14$ TeV and $ L=3000~\rm{fb}^{-1} $. Our results show that the LHT model is still a natural solution to the shortcomings of the electroweak and scalar sector although it has been constrained severely.

Higgs boson production in the littlest Higgs model with T-parity at the ILC

We investigate the Higgs boson production processes [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in the littlest Higgs model with T-parity (LHT) at the International Linear Collider (ILC). We calculate the LHT model predictions on the production rate of these processes at the ILC in the case of (un)polarized beams and the signal strengths of the production processes [Formula: see text] and [Formula: see text] with Higgs decaying to [Formula: see text]. In the allowed parameter space, we find that the signal strengths [Formula: see text] is most likely approach to the expected precision of the ILC.

Rare Higgs three body decay induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity**Supported by National Natural Science Foundation of China (11305049, 11405047), Startup Foundation for Doctors of Henan Normal University (11112, qd15207) and Education Department Foundation of Henan Province(14A140010)

Motivated by the search for flavor-changing neutral current (FCNC) top quark decays at the LHC, we calculate the rare Higgs three body decay H → Wbc induced by top-Higgs FCNC coupling in the littlest Higgs model with T-parity (LHT). We find that the branching ratio of H → Wbc in the LHT model can reach O(10−7) in the allowed parameter space.

Lepton flavor violating Higgs boson decay h→μτ in the littlest Higgs model with T parity

Inspired by the recent CMS $h \to \mu\tau$ excess, we calculate the lepton flavor violating Higgs decay $h \to \mu\tau$ in the littlest Higgs model with T-parity (LHT). Under the constraints of $\ell_i \to \ell_j \gamma$, $Z \to \ell_i \bar{\ell}_j$ and Higgs data, we find that the branching ratio of $h \to \mu\tau$ can maximally reach $\mathcal O(10^{-4})$. We also investigate the correlation between $h \to \mu\tau $, $\tau \to \mu \gamma$ and $Z \to \mu\tau$, which can be used to test LHT model at future $e^+e^-$ colliders.

Revisiting rare top quark decays in the littlest Higgs Model with T-parity

In this paper, we calculate rare top quark 2-body and 3-body decays in the littlest Higgs Model with T-parity (LHT). We find that the branching ratios of [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text] can be greatly enhanced in the LHT model in the allowed parameter space. The recent measurements of the decay [Formula: see text] can give a strong constraint on the LHT parameters and the decays of [Formula: see text] and [Formula: see text] can be accessible at the LHC.

Testing the littlest Higgs model with T-parity at the LHC Run-II

We study the Littlest Higgs model with T-parity (LHT) in the process of $pp \to W_H^+W_H^- \to W^+W^- A_H A_H$ at the 14 TeV LHC. With the $W$-jet tagging technique, we demonstrate that the bulk of the model parameter space can be probed at the level of more than $5\sigma$ in the signature of two fat $W$-jets plus large missing energy. Furthermore, we propose a novel strategy of measuring the principle parameter $f$ that is crucial to testify the LHT model and to fix mass spectrum, including dark matter particle. Our proposal can be easily incorporated into current experimental program of diboson searches at the LHC Run-II.

Quark flavour observables in the Littlest Higgs model with T-parity after LHC Run 1.

The Littlest Higgs model with T-parity (LHT) belongs to the simplest new physics scenarios with new sources of flavour and CP violation. The latter originate in the interactions of ordinary quarks and leptons with heavy mirror quarks and leptons that are mediated by new heavy gauge bosons. Also a heavy fermionic top partner is present in this model which communicates with the SM fermions by means of standard W^pm and Z^0 gauge bosons. We present a new analysis of quark flavour observables in the LHT model in view of the oncoming flavour precision era. We use all available information on the CKM parameters, lattice QCD input and experimental data on quark flavour observables and corresponding theoretical calculations, taking into account new lower bounds on the symmetry breaking scale and the mirror quark masses from the LHC. We investigate by how much the branching ratios for a number of rare K and B decays are still allowed to depart from their SM values. This includes K^+rightarrow pi ^+nu bar{nu }, K_{L}rightarrow pi ^0nu bar{nu }, K_Lrightarrow mu ^+mu ^-, Brightarrow X_sgamma , B_{s,d}rightarrow mu ^+mu ^-, Brightarrow K^{(*)}ell ^+ell ^-, Brightarrow K^{(*)}nu bar{nu }, and varepsilon '/varepsilon . Taking into account the constraints from Delta F=2 processes, significant departures from the SM predictions for K^+rightarrow pi ^+nu bar{nu } and K_{L}rightarrow pi ^0nu bar{nu } are possible, while the effects in B decays are much smaller. In particular, the LHT model favours mathcal {B}(B_{s}rightarrow mu ^+mu ^-) ge mathcal {B}(B_{s}rightarrow mu ^+mu ^-)_mathrm{SM}, which is not supported by the data, and the present anomalies in Brightarrow K^{(*)}ell ^+ell ^- decays cannot be explained in this model. With the recent lattice and large N input the imposition of the varepsilon '/varepsilon constraint implies a significant suppression of the branching ratio for K_{L}rightarrow pi ^0nu bar{nu } with respect to its SM value while allowing only for small modifications of K^+rightarrow pi ^+nu bar{nu }. Finally, we investigate how the LHT physics could be distinguished from other models by means of indirect measurements and discuss the consequences for quark flavour observables of not finding any LHT state in the coming years.

Associated production of single top and Higgs at the LHC in the littlest Higgs model with T-parity

In the littlest Higgs model with T-parity (LHT), we study the t-channel single top production in association with a Higgs boson at 8 and 14 TeV LHC. We find that the cross section can be enhanced obviously in this model compared to the Standard Model. By performing a simple parton-level simulation through $$ pp\to t\left(\to {\ell}^{+}\nu b\right)h\left(\to b\overline{b}\right)j $$ at 14 TeV LHC, we find that the observability of the signal is promising in the favorable parameter space.

Single-top and Higgs associated production via the and tHW− channels at the LHC in the LHT model

Motivated by the recent Large Hadron Collider (LHC) hints of a Higgs boson around 125 GeV, we investigate the processes and at the 8 TeV and 14 TeV LHC in the framework of the littlest Higgs model with T-parity (LHT). Under the current constraints, we find that the relative corrections of at the 8 TeV and 14 TeV LHC can, respectively, reach and at level. These processes have the potential to act as probes for the LHT model at the future LHC.

Double Higgs production in the littlest Higgs model with T-parity at high energy $$e^{+}e^{-}$$ e + e - colliders

In the framework of the littlest Higgs model with T-parity (LHT), we investigate the double Higgs production processes $$e^{+}e^{-}\rightarrow ZHH$$ and $$e^{+}e^{-}\rightarrow \nu \bar{\nu }HH$$ at high energy $$e^{+}e^{-}$$ colliders. We calculate the production cross sections and find that the relative correction at the center-of-mass energy $$\sqrt{s}=500$$ GeV can maximally reach $$-30\,\%$$ for the process $$e^{+}e^{-}\rightarrow ZHH$$ and $$-16\,\%$$ for the process $$e^{+}e^{-}\rightarrow \nu \bar{\nu }HH$$ in the allowed parameter space, respectively. These large relative corrections can reach the detection range of the future $$e^{+}e^{-}$$ colliders so that they can be used to test the LHT effect. The two relevant decay modes $$e^{+}e^{-}$$ $$\rightarrow ZHH \rightarrow l\bar{l} b\bar{b}b\bar{b}$$ and $$e^{+}e^{-}\rightarrow \nu \bar{\nu }HH\rightarrow \nu \bar{\nu }b\bar{b}b\bar{b}$$ are studied and some distributions of the signal and background are displayed.

Precision Calculations for the T-Odd Quark Pair Production at the CLIC e+e− Linear Collider

We perform the precision calculations for the e+e− → q−q̄−(q−q̄− = u−ū−, c−c̄−,d−d̄−, s−s̄−) processes up to the QCD next-to-leading order (NLO) including full weak decays for the final T-odd mirror quarks in the littlest Higgs model with T-parity (LHT) at the Compact Linear Collider (CLIC). We show the dependence of the leading order (LO) and NLO QCD corrected cross sections on the colliding energy √s, and provide the LO and QCD NLO kinematic distributions of final particles. The results show that the LO cross section can be enhanced by the NLO QCD correction and the K-factor increases obviously when the threshold of the on-shell q−q̄−-pair production approaches the colliding energy √s. The K-factor value varies in the range of 1.04 ∼ 1.41 in our chosen parameter space. We find that a simple approximation of multiplying the LO kinematic distribution with the integrated K-factor is not appropriate for precision study of the e+e− → q−q̄−(q−q̄− = u−ū−, c−c̄−, d−d̄−, s−s̄−) processes, since the NLO QCD corrections are phase space dependent. It is necessary to calculate the differential cross sections including full NLO QCD corrections to get reliable results.

Top quark flavor-changing neutral-current decay to a 125 GeV Higgs boson in the littlest Higgs model withTparity

Motivated by the current observation of a 125 GeV Higgs boson, we calculate $t\rightarrow cH$ and $t\rightarrow cg(\gamma)H$ in the unitary gauge in the littlest Higgs model with T-parity(LHT). Due to the large contribution from the new mirror fermions, we find that the branching ratios of $t\rightarrow cH$ and $t\rightarrow cgH$ can be greatly enhanced in the LHT model and maximally reach $\mathcal O(10^{-5})$ in the allowed parameter space. When the mirror fermion mass $M_3 > 2(1.5)$ TeV and the cut-off scale $f=500$ GeV, the process of $pp \to t\bar{t} \to 3b +c +\ell+ \slashed E_{T}^{miss}$ can reach $3\sigma$($5\sigma$) sensitivity at 8(14) TeV LHC with luminosity $\cal{L}$ $=20(300) fb^{-1}$.

Production of $Z t \bar{t}$ and $Z t \bar{T}^{+}$ in the littlest Higgs model with T-parity at High Energy Colliders

In the framework of the littlest Higgs model with T-parity (LHT), we study the process $pp\rightarrow Zt\bar{t}$ at the LHC and the process $e^{+}e^{-}\rightarrow Zt\bar{t}$ at the ILC. Besides, we study the effects in the new production channel, $Z t \bar{T}^{+}$ or $Z T^{+}\bar{t}$ production, at the LHC. We calculate the $Zt\bar{t}$ production cross section and the relative correction, and we present some kinematic distributions. In the allowed parameter space, we find that the relative corrections of the $Zt\bar{t}$ production cross section are significant and may be a good probe for the LHT model. Compared with $Zt \bar{t}$ production, we find that the $Z t \bar{T}^{+}$ production can have a sizable production rate for a T + below TeV scale, which will influence the $Zt \bar{t}$ events.

Dark matter in the little Higgs model under current experimental constraints from the LHC, Planck, and Xenon data

We examine the status of dark matter (heavy photon) in the littlest Higgs model with T-parity (LHT) in light of the new results from the LHC Higgs search, the Planck dark matter relic density and the XENON100 limit on the dark matter scattering off the nucleon. We obtain the following observations: (i) For the LHC Higgs data, the LHT can well be consistent with the CMS results but disfavored by the ATLAS observation of diphoton enhancement; (ii) For the dark matter relic density, the heavy photon in the LHT can account for the Planck data for the small mass splitting of mirror lepton and heavy photon; (iii) For the dark matter scattering off the nucleon, the heavy photon can give a spin-independent cross section below the XENON100 upper limit for $m_{A_H}>95$ GeV ($f> 665$ GeV); (iv) A fit using the CMS Higgs data gives the lowest chi-square of 2.63 (the SM value is 4.75) at $f\simeq$ 1120 GeV and $m_{A_H}\simeq$ 170 GeV (at this point the dark matter constraints from Planck and XENON100 can also be satisfied). Such a best point and its nearby favored region (even for a $f$ value up to 3.8 TeV) can be covered by the future XENON1T (2017) experiment.

One-loop effects on top pair production in the littlest Higgs model with T-parity at the LHC

In this work, we systematically investigate the one-loop corrections to $t\bar{t}$ production in the littlest Higgs model with T-parity (LHT) at the LHC for $\sqrt{s}=8,14$ TeV. We focus on the effects of LHT particles on $t\bar{t}$ cross section, polarization asymmetries, spin correlation and charge asymmetry at the LHC. We also study the top quark forward-backward asymmetry at Tevatron and its correlations with the LHC observables. We found that: (1) the contributions of the LHT particles to $t\bar{t}$ production can only reach about 1% at the 14 TeV LHC. Meanwhile, the anomalous top quark forward-backward asymmetry at Tevatron is also hardly to be explained in the LHT model. (2) the parity violating asymmetries in $t\bar{t}$ production, such as left-right asymmetry $|A_{LR}|$ and the polarization $|P_t|$ can respectively reach 1.1% and 0.5%, which may have the potential to provide a signal of LHT at the LHC.

Production and decay of the 125 GeV Higgs boson in the littlest Higgs model with T-parity

Motivated by recent search results for the standard model (SM) Higgs boson at the Large Hadron Collider (LHC), we revisit the Higgs phenomenology in the littlest Higgs model with T-parity (LHT). We present the signal strength modifier μ, respectively, for the main search channels qq′ → jjh → jjγγ, qq′ → Vh → Vγγ, qq′ → Vh → Vbb, gg → h → γγ, and gg → h → VV in the LHT model. It is found that an enhancement factor of 1.09–1.56 in the qq′ → jjh → jjγγ channel can be obtained for this model in Case B with parameter f in the range 500–1000 GeV. However, the rates for bb̄, ττ̄ are significantly suppressed relative to the SM predictions, which are still consistent with the current sensitivity. It is hoped that this will be further tested with larger integrated luminosity at the LHC.

Precise QCD predictions onWHZHproduction in the littlest Higgs model withTparity at the LHC

We investigate the effects of the littlest Higgs model with $T$ parity up to the QCD next-to-leading order (NLO) on the ${W}_{H}^{\ifmmode\pm\else\textpm\fi{}}{Z}_{H}$ productions at the CERN Large Hadron Collider (LHC), and discuss the kinematic distributions of final decay products and the theoretical dependence of the cross section on the factorization/renormalization scale. We find that the QCD NLO corrections reduce the scale uncertainty of the leading-order cross section in the case of ${\ensuremath{\mu}}_{F}={\ensuremath{\mu}}_{R}$. By adopting the prospino subtraction scheme [scheme (II)] in analysing the QCD NLO contributions, we obtain the numerical results which keep the convergence of the perturbative QCD description. Our results by adopting scheme (II) at the 14 TeV (8 TeV) LHC show that the $K$-factor for the ${W}_{H}^{+}{Z}_{H}$ production varies in the range of 1.01--1.10 (1.00--1.08), while the $K$-factor for the ${W}_{H}^{\ensuremath{-}}{Z}_{H}$ production varies in the range of 1.11--1.13 (1.11--1.12), when the global symmetry-breaking scale $f$ goes from 400 GeV to 1.5 TeV (1 TeV).