570 research outputs found

    Top quark chromomagnetic dipole moment in the littlest Higgs model with T-parity

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    The littlest Higgs model with T-parity, which is called LHTLHT model, predicts the existence of the new particles, such as heavy top quark, heavy gauge bosons, and mirror fermions. We calculate the one-loop contributions of these new particles to the top quark chromomagnetic dipole moment (CMDM)(CMDM) ΔK\Delta K. We find that the contribution of the LHTLHT model is one order of magnitude smaller than the standard model prediction value.Comment: latex files, 12 pages, 3 figure

    Collider Signature of T-quarks

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    Little Higgs models with T Parity contain new vector-like fermions, the T-odd quarks or "T-quarks", which can be produced at hadron colliders with a QCD-strength cross section. Events with two acoplanar jets and large missing transverse energy provide a simple signature of T-quark production. We show that searches for this signature with the Tevatron Run II data can probe a significant part of the Little Higgs model parameter space not accessible to previous experiments, exploring T-quark masses up to about 400 GeV. This reach covers parts of the parameter space where the lightest T-odd particle can account for the observed dark matter relic abundance. We also comment on the prospects for this search at the Large Hadron Collider (LHC).Comment: 5 pages, 3 figure

    Little Higgs models with a light T quark

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    We study Little Higgs models based on a SU(3)_1 x SU(3)_2 global symmetry and with two scales (the two vacuum expectation values f_{1,2}) substantially different. We show that all the extra vector boson fields present in these models may be much heavier than the vectorlike T quark necessary to cancel top-quark quadratic corrections. In this case the models become an extension of the standard model with a light (500 GeV) T quark and a scalar Higgs field with a large singlet component. We obtain that the Yukawa and the gauge couplings of the Higgs are smaller than in the standard model, a fact that reduces significantly the Higgs production rate through glu-glu and WW fusion. The T-quark decay into Higgs boson becomes then a dominant Higgs production channel in hadron colliders.Comment: 16 pages, version to appear in NP

    Precise limits from lepton flavour violating processes on the Littlest Higgs model with T-parity

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    We recalculate the leading one-loop contributions to mu > e gamma and mu -> eee in the Littlest Higgs model with T-parity, recovering previous results for the former. When all the Goldstone interactions are taken into account, the latter is also ultraviolet finite. The present experimental limits on these processes require a somewhat heavy effective scale ~2.5 TeV, or the flavour alignment of the Yukawa couplings of light and heavy leptons at the ~10% level, or the splitting of heavy lepton masses to a similar precision. Present limits on tau decays set no bounds on the corresponding parameters involving the tau leptonComment: 41 pages, 11 figures; v3: matches published version in JHE

    Minimal Flavour Violation and Beyond

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    Starting from the effective-theory framework for Minimal Flavour Violation, we give a systematic definition of next-to-minimal (quark) flavour violation in terms of a set of spurion fields exhibiting a particular hierarchy with respect to a small (Wolfenstein-like) parameter. A few illustrative examples and their consequences for charged and neutral decays with different quark chiralities are worked out in some detail. Our framework can be used as a model-independent classification scheme for the parameterization of flavour structure from physics beyond the Standard Model.Comment: 17 pages, no figures, phenomenological discussion extended, references adde

    Photon-induced production of the mirror quarks from the LHTLHT model at the LHCLHC

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    The photon-induced processes at the LHCLHC provide clean experimental conditions due to absence of the proton remnants, which might produce complementary and interesting results for tests of the standard model and for searching of new physics. In the context of the littlest HiggsHiggs model with T-parity, we consider the photon-induced production of the mirror quarks at the LHCLHC. The cross sections for various production channels are calculated and a simply phenomenology analysis is performed by assuming leptonic decays.Comment: 20 pages, 10 figure

    Pair production of the heavy leptons in future high energy linear e^{+}e^{-} colliders

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    The littlest Higgs model with T-parity predicts the existence of the T-odd particles, which can only be produced in pair. We consider pair production of the T-odd leptons in future high energy linear e+e−e^{+}e^{-} collider (ILCILC). Our numerical results show that, as long as the T-odd leptons are not too heavy, they can be copiously produced and their possible signals might be detected via the processes e+e−→LˉiLje^{+}e^{-}\to \bar{L}_{i}L_{j} in future ILCILC experiments.Comment: Discussions added, typos and references correcte

    Muon to electron conversion in the Littlest Higgs model with T-parity

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    Little Higgs models provide a natural explanation of the little hierarchy between the electroweak scale and a few TeV scale, where new physics is expected. Under the same inspiring naturalness arguments, this work completes a previous study on lepton flavor-changing processes in the Littlest Higgs model with T-parity exploring the channel that will eventually turn out to be the most sensitive, \mu-e conversion in nuclei. All one-loop contributions are carefully taken into account, results for the most relevant nuclei are provided and a discussion of the influence of the quark mixing is included. The results for the Ti nucleus are in good agreement with earlier work by Blanke et al., where a degenerate mirror quark sector was assumed. The conclusion is that, although this particular model reduces the tension with electroweak precision tests, if the restrictions on the parameter space derived from lepton flavor violation are taken seriously, the degree of fine tuning necessary to meet these constraints also disfavors this model.Comment: 26 pages, 7 figures, 4 tables; discussion improved, results unchanged, one reference added, version to appear in JHE

    Effects of the littlest Higgs model with T-parity on Higgs boson production at high energy e+e−e^{+}e^{-} colliders

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    The Higgs boson production processes e+e−→ZHe^{+}e^{-}\to ZH, e+e−→ΜeˉΜeHe^{+}e^{-}\to \bar{\nu_{e}}\nu_{e}H, and e+e−→ttˉHe^{+}e^{-}\to t\bar{t}H are very important for studying Higgs boson properties and further testing new physics beyond the standard model(SMSM) in the high energy linear e+e−e^{+}e^{-} collider(ILCILC). We estimate the contributions of the littlest Higgs model with T-parity(LHTLHT model) to these processes and find that the LHTLHT model can generate significantly corrections to the production cross sections of these processes. We expect the possible signals of the LHTLHT model can be detected via these processes in the future ILCILC experiments.Comment: 9 pages, 2 figures, references adde
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