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June 16, 2010

Evidence found for Five Types of Higgs Particles

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A discovery of CP violation in Bs−¯Bs mixing at the Tevatron might invalidate the Standard model and out the SM differentiate between various models of new physics. Evidence is hinting at five types of Higgs particles.

The Fermi Lab DZEro experiment web page is here
the Winter 2010 results page.

A physicist explains the news here.

There is evidence that the asymmetry is about 100x larger than expected or 3.2 sigma (or 3.2 standard deviations). Now that’s not enough away from the predicted value to claim discovery just yet (need 5 sigma to be really sure). But it’s a very interesting result.


The DZero experiment set up and observed collisions protons and anti-protons and was designed to examine the reason why the world is composed of normal matter rather than its opposite: anti-matter. They found the collisions resulted in pairs of muons one percent more often than anti-muon particles. The asymmetry could explain why matter has come to dominate over anti-matter, rather than the two annihilating each other.

This effect, called CP violation, had been seen before but not to the same degree as seen in DZero, and the degree of asymmetry found in the latest results is greater than can be accounted for by the Standard Model. The researchers said the results could be explained by the existence of five Higgs boson particles with similar masses, with one having a negative electric charge, one negative and three neutral. The theory is called the two-Higgs doublet model.


Arxiv - CP violation in Bs mixing from heavy Higgs exchange


The two-Higgs doublet model is not the only possible explanation for the results, but Dr Martin said fitting a new effect in the Standard Model without disrupting its fit with other tests is difficult. The Standard Model accommodates only one Higgs doublet, and while scientists think of the Higgs as a single particle, Dr Martin said it “actually comes in a package of four”. Only one is seen because the other three are seen as W and Z bosons. Adding another Higgs doublet adds four more particles.
The anomalous dimuon charge asymmetry reported by the D0 Collaboration may be due to the tree-level exchange of some spin-0 particles which mediate CP violation in Bs− ¯Bs meson mixing. We show that for a range of couplings and masses, the heavy neutral states in a two Higgs doublet model can generate a large charge asymmetry. This range is natural in “uplifted supersymmetry”, and may enhance the B−! and Bs!μ+μ− decay rates. However, we point out that on general grounds the reported central value of the charge asymmetry requires new physics not only in Bs−¯Bs mixing but also in B = 1 transitions or in Bd− ¯Bd mixing.


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