arXiv 1607.046432016-07-15hep-phhep-ex

双Higgs二重态模型中手征重费米子：750 GeV共振与否

Chiral heavy fermions in a two Higgs doublet model: 750 GeV resonance or not

Shaouly Bar-Shalom, Amarjit Soni

备注：: 13 pages, latex
DOI：: 10.1016/j.physletb.2016.12.046

摘要：

我们重新审视模型，其中重手征第四代费米子的二重态嵌入一类具有离散$Z_2$对称性的两个希格斯二重态模型（2 HDM）中，该模型将“重”标量二重态仅耦合到第四代费米子，而“轻”标量二重态耦合到标准模型（SM）费米子-我们几年前引入的所谓4G 2 HDM。我们研究的约束施加在4G 2 HDM从直接搜索重费米子，从精密电弱数据（PEWD）和测量的生产和衰变信号的125 GeV标量，这在4G 2 HDM对应于最轻的CP-甚至标量h。然后，我们证明了最近报道的在750 GeV附近的$γγ$谱中的过剩可以被4G 2 HDM的重CP偶标量H所容纳，从而导致了参数空间的唯一选择：两个CP偶标量h，H与重第四代夸克和轻子质量m_t '，m_b' 900 GeV之间的可忽略混合（sinα~ O（0.001））< 400 GeV and $m_{ν'},m_{τ'}$ >。无论750 GeV的γγ共振是否被证实，在q' - Higgs系统（q'= t '，b'）中都会出现有趣的现象，可以在LHC中进行搜索。例如，模型的重标量态S=H，A，H^+可以具有BR（S -> q 'q'）~ O（1），在共振时产生可观察到的q 'q'信号，随后是味道改变q'衰减t'->uh（u=u，c）和/或b '->dh（d=d，s，b）。这导致了不同的高喷注多重性特征，有或没有带电轻子，形式为q 'q' ->（nj + mb + lW）_S（j和b分别是轻和b夸克喷注），n+m+l =6-8和独特的运动学特征。它还表明，4G 2 HDM可以很容易地容纳有趣的最近的迹象表明，在轻子味违反（LFV）衰变$h \to τμ$的125 GeV希格斯粒子，如果证实的一个π级分支比。

英文摘要：

We revisit models where a heavy chiral 4th generation doublet of fermions is embedded in a class of two Higgs doublets models (2HDM) with a discrete $Z_2$ symmetry, which couples the "heavy" scalar doublet only to the 4th generation fermions and the "light" one to the Standard Model (SM) fermions - the so-called 4G2HDM introduced by us several years ago. We study the constraints imposed on the 4G2HDM from direct searches of heavy fermions, from precision electroweak data (PEWD) and from the measured production and decay signals of the 125 GeV scalar, which in the 4G2HDM corresponds to the lightest CP-even scalar h. We then show that the recently reported excess in the $γγ$ spectrum around 750 GeV can be accommodated by the heavy CP-even scalar of the 4G2HDM, H, resulting in a unique choice of parameter space: negligible mixing (sinα~ O(0.001)) between the two CP-even scalars h,H and heavy 4th generation quark and lepton masses m_t',m_b' < 400 GeV and $m_{ν'},m_{τ'}$ > 900 GeV, respectively. Whether or not the 750 GeV γγresonance is confirmed, interesting phenomenology emerges in q' - Higgs systems (q'=t',b'), that can be searched for at the LHC. For example, the heavy scalar states of the model, S=H,A,H^+, may have BR(S -> q'q') ~ O(1), giving rise to observable q'q' signals on resonance, followed by the flavor changing q' decays t'->uh (u=u,c) and/or b'->dh (d=d,s,b). This leads to distinct high jet-multiplicity signatures, with or without charged leptons, of the form q'q' -> (nj + mb + lW)_S (j and b being light and b-quark jets, respectively), with n+m+l =6-8 and unique kinematic features. It is also shown that the 4G2HDM can easily accommodate the interesting recent indications of a percent-level branching ratio in the lepton-flavor-violating (LFV) decay $h \to τμ$ of the 125 GeV Higgs, if confirmed.

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