Friday, December 18, 2009

Dark matter particle was not discovered!

The title of my previous posting was Has dark matter been found?. The answer came in thursday and was Probably not!.

Peter Woit told about the outcome of the experiment. There were two events with the estimated background of .8 events and the probability of observing two or more events is 23 per cent. Therefore the result could be argued to be noise. The experiment was however very useful since it poses an upper bound 7.0×10-44 cm2 for a WIMP of mass 70 GeV at the 90 per cent confidence level. The mass of 70 GeV would maximize the cross section if WIMP corresponds to a dark matter particle. Otherwise the lower bound for mass is 2 GeV: not very informative! The cross section estimate is not absolute but relies on standard model dark matter halos of galaxies based on WIMPs allowing to estimate the density of dark matter particles and their flux to the detector. If one assumes that the density is of same order of magnitude as the density of ordinary particles the upper bound on the cross section is higher.

Tommaso Dorigo gives a nice summary about the implications of the finding in this posting SUSY more unlikely by the new CDMS II results. The SUSY afficionados identifying WIMP as neutralino could experience unpleasant sensations in their stomach since this identification eats a considerable fraction of the parameter space of SUSYs. Tommaso Dorigo created the impression that the experiment poses limits on SUSY parameters as such: this is of course not true. Even the believers on neutralino dark matter have no reason to get worried about funding: there are LOTs of parameter space left.

What does TGD say about the results. For few months ago I still believed that TGD does not predict space-time supersymmetry but the progress in the understanding of the mathematical structure of the theory forced me to turn up my coat (see this). The resulting super-symmetry shares a lot with standard SUSY but differs in some aspects dramatically from it. In TGD framework neutralino is not responsible for dark matter and its density is expected to be much lower than in dark matter scenarios -of the same of order of magnitude as the densities of other particles. The irony is that if neutralino corresponds to dark matter in TGD sense (has large Planck constant and therefore lives at different page of the Big Book whose pages are partially characterized by the values of Planck constant than we do), its detection requires that it leaks to our page. This reduces the detection probability further!

In TGD framework the most plausible interpretation of WIMPs (not identified as dark matter) would be as neutralinos (see this). If one takes seriously the anomalous eeγγ +missing transverse energy event detected for 15 years ago by CDF, one can deduce from the kinematics of this event the masses of the superpartners of electron, Higgs, and Z0 using p-adic length scale hypothesis and the assumption that SUSY breaking at the level of mass spectrum means only different p-adic mass scales for the members of SUSY multiplet. The masses are 131 GeV (just at the upper bound allowed kinematically), 45.6 GeV, and 91.2 GeV (Z0 mass) respectively. My hope was that they might have detected 45.6 GeV higgsino but this hope was unrealistic from TGD point of view suggesting much lower flux of these particles.

Addition: In New Scientist there is an article titled 2010 preview: Will a neutralino steal Higgs's thunder? about the possibility that LHC might discover neutralino before Higgs. Also Lubos Motl mentions this possibility. If the mixing between neutralinos is absent and SUSY breaking takes place only via the choice of the p-adic mass scale, Higgsino with 45.6 GeV mass would be the neutralino and its discovery would indirectly prove also the existence of Higgs in TGD Universe. Do not forget the 45.6 GeV;-)!

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