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Probing topcolor-assisted technicolor from top charge asymmetry and triple-top production at the LHC

Han, Chengcheng; Liu, Ning; Wu, Lei; Yang, Jin MinSubjects: Physics >> The Physics of Elementary Particles and Fields

In a topcolor-assisted technicolor model (TC2) with large FCNC top quark couplings, we study its correlated contributions to the top quark forward-backward asymmetry (A(FB)) at the Tevatron, the top charge asymmetry (A(C)) and the triple-top production at the LHC. Under current constraints on the top quark from the LHC and Tevatron (such as the total and differential production rates), we scan the parameter space of such a TC2 model. We find that in the allowed parameter space the TC2 model can explain the Tevatron measured A(FB) at 2 sigma level, but meanwhile significantly enhance A(C) at the LHC. Such enhanced A(C), albeit currently allowed by the LHC measurement at 2 sigma level, will serve as a test of TC2 with the improvement of measurement precision at the LHC. Then with all the constraints (including the requirement to explain A(FB) at 2 sigma level and satisfying the current LHC measurement of A(C) at 2 sigma level), we find that the TC2 model can induce sizable triple-top production at the 14 TeV LHC (the production rate can maximally reach 16 pb). Due to the low SM backgrounds, the triple-top production can also be a good probe for TC2 model, complementary to A(C). (C) 2012 Elsevier B.V. All rights reserved. |

Subjects: Physics >> The Physics of Elementary Particles and Fields

Inspired by the recent LHC Higgs data and null search results of supersymmetry (SUSY), we scan the parameter space of the Minimal Supersymmetric Standard Model (MSSM) with relatively heavy sparticles (1-3 TeV). Then in the parameter space allowed by current collider experiments and dark matter detections, we calculate the complete one) SUSY QCD corrections to pp -> b (b) over barh at the LHC with root s = 14 TeV and obtain the following observations: (1) For the large values of tan beta and low values of m(A), the SUSY QCD effects can be quite large, which, however, have been excluded by the latest results of LHC search for H/A -> tau(+)tau(-); (ii) For modest values of tan beta and m(A) which so far survived all experimental constraints, the SUSY QCD corrections can maximally reach about -9%. |

Subjects: Physics >> The Physics of Elementary Particles and Fields

The excess of top-quark forward-backward asymmetry (A(FB)(t)) reported by the Tevatron and the enhancement of the Higgs decay to diphoton observed at the LHC may point to a same origin of new physics. In this note we examined such anomalies in the two-Higgs-doublet model with a color-triplet scalar. We found that under current experimental constraints this model can simultaneously explain both anomalies at 1 sigma level. Also, we examined the Higgs decay h -> Z gamma and displayed its correlation with h -> gamma gamma. We found that unlike other models, this model predicts a special correlation between h -> Z gamma and h -> gamma gamma, i.e., the Z gamma rate is highly suppressed while the gamma gamma rate is enhanced. This behavior may help to distinguish this model in the future high luminosity run of the LHC. |

Probing light higgsinos in natural SUSY from monojet signals at the LHC

Han, Chengcheng; Kobakhidze, Archil; Liu, Ning; Saavedra, Aldo; Wu, Lei; Yang, Jin MinSubjects: Physics >> The Physics of Elementary Particles and Fields

We investigate a strategy to search for light, nearly degenerate higgsinos within the natural MSSM at the LHC. We demonstrate that the higgsino mass range mu in 100 - 160 GeV, which is preferred by the naturalness, can be probed at 3 sigma significance through the monojet search at 14TeV HL-LHC with 3000 fb(-1) luminosity. The proposed method can also probe certain region in the parameter space for the lightest neutralino with a high higgsino purity, that cannot be reached by planned direct detection experiments at XENON-1T(2017). |

Full one-loop electroweak corrections to e(+)e(-) -> ZH gamma at a Higgs factory

Liu, Ning; Ren, Jie; Wu, Lei; Wu, Peiwen; Yang, Jin MinSubjects: Physics >> The Physics of Elementary Particles and Fields

Motivated by the future precision test of the Higgs boson at an e(+)e(-) Higgs factory, we calculate the production e(+)e(-) -> ZH gamma in the Standard Model with complete next-to-leading order electroweak corrections. We find that for p s root s = 240 (350) GeV the cross section of this production is sizably reduced by the electroweak corrections, which is 1.03 (5.32) fb at leading order and 0.72 (4.79) fb at next-to-leading order. The transverse momentum distribution of the photon in the final states is also presented. |

ATLAS Z-peaked excess in the MSSM with a light sbottom or stop

Kobakhidze, Archil; Liu, Ning; Wu, Lei; Yang, Jin MinSubjects: Physics >> The Physics of Elementary Particles and Fields

We attempt to explain the recent ATLAS 3 sigma excess of dilepton events with an invariant mass near Z peak through the gluino-mediated sbottom production in a simplified scenario inspired by the minimal supersymmetric Standard Model. The additional Z bosons can be produced through the cascade decay chain (g) over tilde -> b (b) over tilde1(dagger) -> b (b) over bar(chi) over tilde (0)(2,3) -> b (b) over bar(chi) over tilde (0)(1)Z, in which (b) over tilde (1) is the right-handed sbottom, (chi) over tilde (0)(1) is the bino-like lightest supersymmetric particle (LSP) and (chi) over tilde (0)(2,3) are two nearly degenerate Higgsino-like next-to LSPs. Taking into account the constraint from the LHC search for the gluino-mediated sbottom production in the final states with the missing transverse energy and at least three b-jets, we find that the ATLAS on-Z excess can only be marginally explained at the 2 sigma level. We also note that within the scenario where the gluino predominantly decays to the right-handed stop instead of the sbottom, the excess can hardly be explained, since the Z-boson is not produced in the stop dominant decay channel, (t) over tilde (1) -> b (chi) over tilde (+)(1). |

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