Wednesday, February 23, 2011

Implications of 35/pb SUSY searches on best fit parameters

O. Buchmüller and 12 co-authors including John Ellis have made some new calculations within their previously used framework,
Implications of Initial LHC Searches for Supersymmetry
The so-far negative early searches by the CMS and ATLAS collaboration are incorporated into their updated best fits. Optimum parameters of several slices of the supersymmetric standard model's parameter spaces are adjusted.

m_{1/2} has to be raised to from 300 GeV or so to approximately 400 GeV in CMSSM, NUHM1, and VCMSSM, and 550 GeV in mSUGRA. m_0 may remain low, between 70 and 230 GeV. The best tan(beta) has to be raised from 8-11 to 9-16 in the three models and stays at 28 in mSUGRA. The preferred Higgs mass is near 115 GeV in the three models and 120 GeV in mSUGRA.

The gluino masses around 800-1000 GeV are favored in the three models while 1100-1400 GeV wins in mSUGRA.

One may say that the experimentally favored regions of the parameter spaces haven't changed substantially when the 35/pb data by ATLAS, CMS were released. A similar analysis was just released by Allanach and by Scopel et al.

The first paper, by Allanach, is described by the very author in this blog entry. One of the fun consequences is that because of a non-significant excess, the 800-1,000 GeV squark masses actually became more likely than before. Also, the most likely squark mass actually decreased! Allanach's best fit indicates that it's damn likely that the squarks are lighter than 1500 GeV and will be seen by the LHC.

So if and once the LHC excludes squarks up to 1500 GeV, I may become nervous, but the moment is not now.

The second paper argues that the lowest neutralino mass may stay as low as 10 GeV or so.

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