Cosmic positron signature from dark matter in the littlest Higgs model withTparity

Abstract

We calculate the flux of cosmic positrons from the dark matter annihilation in the littlest Higgs model with T-parity. The dark matter annihilates mainly into weak gauge bosons in the halo, and high energy positrons are produced through leptonic and hadronic decays of the bosons. We investigate a possibility to detect the positron signal in upcoming experiments such as PAMELA and AMS-02. We found that the dark matter signal can be distinguished from the background in the PAMELA experiment when the dark matter mass is less than 120 GeV and the signal flux is enhanced due to a small scale clustering of dark matter. Furthermore, the signal from the dark matter annihilation can be detected in the AMS-02 experiment, even if such enhancement does not exist. We also discuss the invisible width of the Higgs boson in this model. 1 E-mail: masano@post.kek.jp 2 E-mail: smatsu@post.kek.jp 3 E-mail: okadan@post.kek.jp 4 E-mail: yasuhiro.okada@kek.jp I IntroductionThe hierarchy problem in the Standard Model (SM) is expected to give a clue to explore the physics beyond the SM. This problem is essentially related to quadratically divergent corrections to the Higgs boson mass, and we need a mechanism to avoid the divergences. To solve the problem, many scenarios have been proposed so far, for example supersymmetry, in which the divergences are completely removed.Other examples are scenarios with a low energy cutoff scale around a TeV such as Techni-color and TeV scale extra-dimension.The latter scenarios are, however, constrained by the electroweak precision measurements. From the analysis of higher dimensional operators at the cutoff scale, it has been found that the scale should be larger than roughly 5 TeV [1]. For such high energy cutoff, the hierarchy problem appears again: We still need the fine-tuning of a few percent level in the Higgs mass term in order to obtain the 100-200 GeV Higgs boson mass. This problem is called the little hierarchy problem.Recently the little Higgs model [2,3] has been proposed for solving the little hierarchy problem. In this scenario, the Higgs boson is regarded as a pseudo NambuGoldstone boson. New particles such as heavy gauge bosons and a top-partner are introduced, and all quadratic divergences to the Higgs mass term completely vanish at one-loop level due to these particles' contributions. Thus, the fine-tuning of the Higgs boson mass is avoided even if the cutoff scale is around 10 TeV.The original little Higgs model is still strongly constrained by the electroweak precision measurements [4]. This is mainly due to the contributions to electroweak observables from new heavy gauge bosons, because their masses are much smaller than the cutoff scale. In particular, direct couplings among a new heavy gauge boson and SM particles give sizable contributions to the observables. As a result, masses of new particles have to be raised, and the fine-tuning of the Higgs boson mass is reintroduced.To resolve the problem, the implementation of the Z 2 symmetry called T-parity to the model has b...

Probing the littlest Higgs model withTparity using di-Higgs events throughZH-pair production at the LHC in NLO QCD

“…The T -odd mirror fermions acquire masses via the following SU (5) and T parity invariant Lagrangian: 18) where i, j = 1, ..., 3 are flavor indices, and ξ = e iΠ/f , transforming under SU (5) as…”

“…According to the current research, the dark matter should be cold and weakly interacting, typically detected as missing-energy signals at particle colliders. The littlest Higgs model with T parity (LHT) predicts a neutral and colorless T -odd particle A H that can be a good candidate for dark matter [17][18][19].…”

Galactic electrons and positrons at the Earth: new estimate of the primary and secondary fluxes

“…Dark matter could indeed in some cases manifests itself in this channel (e.g. Baltz & Edsjö 1998;Hooper & Kribs 2004;Lavalle et al 2007;Asano et al 2007;Bergström et al 2008;Cirelli et al 2008;Delahaye et al 2008;Pieri et al 2009;Catena et al 2010), and the discovery of an exotic contribution to the positron budget would be a spectacular result. Any such result would, however, have to rely on solid grounds, in particular a good understanding of the astrophysical contributions.…”

Correlations between ε′/ε and rareKdecays in the Littlest Higgs model with T-parity

“…A discrete symmetry called T-parity [29] is then introduced, in order to reconcile the model with electroweak precision tests. It restores the custodial SU(2) symmetry and, therefore, the compatibility with electroweak precision data is obtained already for quite small values of the NP scale, f ≥ 500 GeV [61,62]. Another important consequence is that particle fields are T-even or T-odd under T-parity.…”