status of +4/3 scalar as explanation of $t\bar t$ asymmetry

Question

One of the early proposals for the Tevatron asymmetry on $t \bar t$ was a "fundamental diquark" with a charge (and hypercharge) +4/3, either in a triplet or a sextet colour. I am interested on the current status of this proposal:

Generically, has some particular model of been favoured in ulterior research?

For starters, you can see the short report in JHEP 1109:097,2011, at the end of section 2, points 5 and 6. I only become aware of the survival of this hypothesis after seeing http://arxiv.org/abs/1111.0477 last week.

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Comments

Can you link to some published account of this proposal?

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@Moshe done. But I am interested on any account, either unpublished (conferences or arxiv), published or rumoured.

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I have confirmed with some authors that the field uses the normalization Q=T3+Y for the hypercharge. So hypercharge=4/3 is charge=4/3 if T=0

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