Tuesday, January 15, 2013

SUSY Higgs Boson Global Fits Get Specific

In there Standard Model there are 4-3 Higgs bosons (ie. one of them because the other three are "eaten" by the W+, W- and Z bosons).  But, in Supersymmetric models there are at least 8-3 Higgs bosons (i.e. five of them), two charged and three neutral (some supersymmetric models have additional sets of four Higgs bosons).
[I]f you believe in Supersymmetry you might want to try and classify the newly found boson . . . as one of the three neutral states that the less complicated class of SUSY theories predict to exist: two h, H cp-even states, and a CP-odd state A. Or some mixture of those. If you do that, you immediately get some constraining power to add to the many direct searches for SUSY signatures in the tan(β) versus M_A plane. The exercise may thus reveal where to look for the other Higgs bosons, for instance! . . .
So, a new paper by Bechtle, Brein, Heinemeyer, Stal, Stefaniak, Weiglein and Williams . . .  [has] taken information about experimental rates and limits of neutral Higgs decays in all measured final states by the experiments at the LHC and Tevatron, together with limits from charged Higgs signals, and produced a map of delta-chi squared (a statistical measure of compatibility between experimental results and theoretical predictions) in the tan(β) - A mass plane. . .
In particular, by assuming that the 126-GeV Higgs boson is the heavier of the two neutral CP-even states, then the best-fit region highlighted in black shows that, if one accepts the authors' sample choice of some of the SUSY parameters (except β and M_A), [specifically: MSUSY = 1 TeV; |X|= 2.4 TeV; mu = 1 TeV; M1 = 100 GeV; M2 = 200 GeV; M3 = 800 GeV] one gets the hint that the A mass is 101 GeV, tan(β) is 6, and the light-Higgs h mass is 92.3 GeV. . . . in this scenario the h particle, the lightest Higgs, escapes the LEP II search limits by acquiring reduced couplings to Z bosons (I recall that LEP II limits a standard model Higgs at 114.4 GeV, but that if one assumes that the production cross section of h in electron-positron collisions is smaller than what the standard model calculates, then LEP II could have missed that particle). . . we are down to ranges of tan(β) from 2 to 14.
From here.

This has the desirable character of being falsifiable with existing technologies and there are indeed rumors of a possible 100 GeVish bump in the LHC data.  The margin of theoretical error in the mass predictions is roughly +/- 2.5 GeV at the one sigma level.

But, this narrowed parameter space isn't too meaningful because less complicated versions of SUSY used to make the estimate, the Minimal Supersymmetric Model (MSSM), and even its close cousin, the next-to-MSSM (NMSSM) is increasingly being ruled out on a variety of grounds in addition to those provided by a Higgs boson mass fit in any case.  A computer program linked to in the paper allows for others to make their own fits with different choices of parameters from the same data.


Maju said...

I see that you're better already. Nice. :)

andrew said...