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Experimental Constraints on the Higgs Mass


Established measurements of the Z boson mass at LEP and the top quark mass at the Tevatron now allow predictions of the Higgs mass from precise measurements of the weak mixing angle, the W mass and the Z width.


Higgs' Mass Plot by Technique.  The yellow region is excluded  by direct searches for the Higgs by the LEP experiments. The curves represent probability distributions for what the Higgs mass should be based on several different experimental techniques.  The minimum of the curves is the most likely Higgs mass and where the curves intersect the 95% CL or 99% CL lines indicate that the Higgs mass should be below that intersection point with 95% or 99% confidence, respectively. SLD's result is shown in red.  The CERN result using leptonic asymmetries is shown in blue. Combined results from W mass measurements at CERN and Fermilab are shown in green.  The black band labeled 'Other' includes LEP measurements of GZ, shad0, and Rl, LEP/SLD measurements of Rb and Rc, SLD measurements of Ab and Ac, and NuTeV's measurement of R-.  All these techniques are self-consistent and prefer a light Higgs mass.  But the CERN result from the hadronic measurement of the weak mixing angle, which uses the forward-backward asymmetry in decays of the Z0 to b quarks (shown in magenta), favors a much heavier Higgs.   (This plot is made using Dahad(MZ2)=0.02738 +/- 0.00020.)


The 95% CL and 99% CL limits on the Higgs mass are summarized in an accompanying table. 



Higgs' Mass Plot comparing the LEP AFBb measurement with the rest of the world's data..  Combining all the world's data, but excluding the LEP AFBb result, yields the curve shown in red and determines that the Higgs should be lighter than 190 GeV at 99% CL.  The magenta curve shows the forward-backward b-quark asymmetry result from LEP.  In this case, one finds that the Higgs should be heavier than 190 GeV at 99% CL!    (This plot is made using Dahad(MZ2)=0.02738 +/- 0.00020.)

Last updated 04-09-2001.