What has been found is that the production rate for jet pairs with jet mass around 170 GeV, which happens to correspond to top quark mass, the production cross section is about 3 times higher higher than QCD simulations predict. 3.44 sigma deviation is in question meaning that its probability is same as for the normalized random variable x/σ to be larger than 3.44 for Gaussian distribution
Recall that 5 sigma is regarded as so unprobable fluctuation that one speaks about discovery. If top pairs are produced by some new particle, this deviation should be seen also when second top decays leptonically meaning a large missing energy of neutrino. There is however a slight deficit rather than excess of these events.
One can consider three interpretations.
- The effect is a statistical fluke. But why just at the top quark mass?
- The hadronic signal is real but there is a downwards fluctuation reducing the number of leptonic events slightly from the expected one. In the leptonic sector the measurement resolution is poorer so that this interpretation looks reasonable. In this case the decay of some exotic boson to top quark pair could explain the signal. Below this option will be considered in more detail in TGD framework and the nice thing is that it can be connected to another top quark related anomaly reported by CDF for few weeks ago.
- Both effects are real and the signal is due to R-parity violating 3-particle decays of gluinos with mass near to top quark mass. This is the explanation proposed in the paper of Perez and collaborators.
This option could make sense also in TGD framework where R-parity is violated by the same -purely TGD based- mechanism which forces massivation of particles at the fundamental level. Super partners are created by adding covariantly constant right-handed neutrinos and antineutrinos to the states. The dynamics of the modified Dirac equation however mixes right-handed and left-handed neutrinos so that R-parity is not conserved.
Addition: The three-body decay would be in TGD framework sg→ st+tbar (or t+stbar) → t+tbar+ νbar (or t+tbar+ ν). Only the other member of top pair would produce neutrino and the charged lepton accompanying it in electroweak decays would be absent so that the signature is unique. t is accompanied by νRbar and tbar by νR and gluino by νRbar at fermionic wormhole throat or by νR at antifermionic wormhole throat also gluino for which both throats are sfermionic is possible.
The three-body decay would be in TGD framework sg→ st+tbar (or t+stbar) → t+tbar+ νbar (or t+tbar+ ν). Only the other member of top pair would produce neutrino and the charged lepton accompanying it in electroweak decays would be absent so that the signature is unique. t is accompanied by νRbar and tbar by νR and gluino by νRbar at fermionic wormhole throat or by νR at antifermionic wormhole throat also gluino for which both throats are sfermionic is possible.
This effect is one of the basic signatures of quantum TGD and due to the fact that gamma matrices appearing in Dirac equation are different from those appearing in standard quantum field theories. Both induced gamma matrices (defined as projections of the imbedding space gamma matrices to the space-time surface) and modified gamma matrices (defined as contractions with imbedding space gamma matrices of canonical momentum densities defined by action) are mixtures of M4 and and CP2 gamma matrices. As a consequence, M4 chiralities get mixed and only H=M4 × CP2-chirality is conserved and corresponds to the separate conservation of baryon and lepton numbers.
It must be emphasized that the mixing is a direct signature for the space-time as a 4-surface identitification and distinguishes sharply and at very general level between TGD and competing theories.
Consider now the second option in which one would have heavy new boson decaying to top quark pair. The following short argument is modified from that appearing in the earlier posting.
- Already earlier both Jester and Lubos told that CDF sees 3.4 sigma top quark pair asymmetry in proton-antiproton collisions. The asymmetry would be roughly five times larger than predicted by QCD. The asymmetry requires that the quark-antiquark pair annihilating to top quark pair can do so by coupling not only to gluons and to a new boson which has axial or partially axial coupling so that interference term would produce the asymmetry.
- Axial vector color octet with rather strange couplings to quarks and leptons was suggested by the experimenters as an explanation of the finding. I do not however see any deep reason -correct me if I am wrong!- for why one could not consider also pseudo-scalar octet. TGD indeed predicts that all gauge bosons should be accompanied by scalars and pseudo-scalars with same quantum numbers: also gluons. Scalars should be eaten to give the third polarization to gauge bosons. Maybe the coupling to a pseudo-scalar variant of color octet Higgs could give rise to a contribution interfering with the contribution of spin zero virtual gluons and in this manner give rise to the asymmetry. Maybe there is simple objection but I am not able to invent it now. More complex option would be color octet excitation of Z0.
- The decays of pseudo-scalar gluon to top quark pairs might also explain the above described anomaly since the coupling would be strong so that at least orders of magnitude would be correct.
- Addition: Jester reports new data about the strange top-pair forward-backward asymmetry. For top pairs with invariant mass above 450 GeV the asymmetry is claimed by CDF to be stunningly large 48+/-11 per cent. 3 times more often top quarks produced in qqbar annihilation prefer to move in the direction of q. If true this would favor color octet excitations of Z0as the most natural explanation since the asymmetry would be not only due to the interference of vector and axial vector exchanges but also due to the inherent parity breaking of colored Z0 couplings. The effect would provide further support for the identification of color quantum numbers in terms of color partial waves rather than as spin like quantum numbers. The earlier support comes from the evidence for colored excitations of leptons.
Addition: After a badly slept night I have come to new thoughts about the possible explanation of the effect. What is so weird (really weird when one begins to think the numbers!) that the outgoing top quark (t) remembers the direction of motion of quark q before annihilation to intermediate gluon which it should by the basic definition of annihilation diagram. For any exchange diagram the situation would be totally different: consider only Coulomb scattering! The quark q of the first proton would scatter from the quark of the second proton and transform to top quark in the scattering and keep its direction of motion in good approximation since small angle exchanges dominate due to the propagator factor. Flavor changing exchange diagrams are however not possible in the standard model world since the only flavor changing are charged weak currents and their contribution is negligible.
In the new physics inspired by TGD situation is however different! The identification of family replication phenomenon in terms of genus of the wormhole throats (see this) predicts that family replication corresponds to a dynamical SU(3) symmetry with gauge bosons belonging to the octet and singlet representations. Ordinary gauge bosons would correspond besides the familar singlet representation also to exotic octet representation for which the exchanges induce neutral flavor changing currents in the case of gluons and neutral weak bosons and charge changing ones in the case of charged gauge bosons. The exchanges of the octet representation for gluons would explain the anomaly! Also electroweak octet could of of course contribute. Note that this mechanism would explain both anomalies associated with top quark production.
What is fantastic is that LHC will soon allow to decide whether this explanation is correct!