Tuesday, August 04, 2009

Indications for excited states of Z0 boson

Tommaso Dorigo is a highly inspiring physics blogger since he writes from the point of view of experimental physicist without the burden of theoretical dogmas and does not behave aggressively;-). I share with him also the symptons of splitting of personality to fluctuation-enthusiast and die-hard skeptic. This makes life interesting but not easy. This time Tommaso told about the evidence for new neutral gauge boson states in high energy ppbar collisions. The title of the posting was A New Z' Boson at 240 GeV? No, Wait, at 720!?.

1. The findings

The title tells that the tentative interpretation of these states are as excited states of Z0 boson and that the masses of the states are around 240 GeV and 720 GeV. The evidence for the new states comes from electron-positron pairs in relatively narrow energy interval produced by the decays of the might-be-there gauge boson. This kind of decay is an especially clean signature since strong interaction effects are not present and it appears at sharp energy.

240 GeV bump was reported by CDF last year in ppbar collisions at cm energy s1/2=1.96 TeV. The probability that it is a fluctuation is .6 per cent. What is encouraging that also D0 found the same bump. Tommaso explains much better the experimental side so that I need not lose that little credibility that I might still have. If the particle in question is analogous to Z0, it should decay also to muons. CDF checked this and found a negative result. This made Tommaso rather skeptic.

Also indications for 720 GeV resonance (this is just a nominal value, the mass could be somewhere between 700-800 GeV) was reported by D0 collaboration: the report is titled as Search for high-mass narrow resonances in the di-electron channel at D0. There are just 2 events above 700 GeV but background is small;-): just three events above 600 GeV. It is easy to guess what skeptic would say.

Before continuing I want to make clear that I refuse to be blind believer or die-hard skeptic and that I am unable to say anything serious about the experimental side. I am just interested to see whether these events might be interpreted in TGD framework. TGD indeed predicts -or should I say strongly suggests- a lot of new physics above intermediate boson length scale.

Are exotic Z0 bosons p-adically scaled up variants of ordinary Z0 boson?

p-Adic length scale hypothesis allows the p-adic length scale characterized by prime p ≈ 2k vary since k can have several integer values. The TGD counterpart of Gell-Mann-Okubo mass formula involves varying value of k for quark masses. Several anomalies reported by Tommaso during years could be resolved if k can have several values. Last anomaly was the discovery that Ωb baryon containing two strange quarks and bottom quark seems to appear with two masses differing by about 110 MeV. TGD explains the mass difference correctly by assuming that second strange quark has mass two times the ordinary. The predicted mass difference is 100 MeV.

One can look whether p-adic length scale hypothesis could explain the masses of exotic Z0 candidates as multiples of half octaves of Z0 mass which is 91 GeV. k=3 would give 257 GeV, not too far from 240 GeV. k=6 would give 728 GeV consistent with the nominal value of the mass. Also other masses are predicted and this could serve as a test for the theory. This option does not however explain why muon pairs are not produced in the case of 240 GeV resonance.

Support for topological explanation of family replication phenomenon?

An improved explanation is based on TGD based view about family replication phenomenon.

  1. In TGD the explanation of family replication is in terms of genus of 2-dimensional partonic surface representing fermion. Fermions correspond to SU(3) triplet of a dynamical symmetry assignable to the three lowest genera (sphere, torus, sphere with two handles). Bosons as wormhole contacts have two wormhole throats carrying fermion numbers and correspond to SU(3) singlet and octet. Sooner or later the members of the octet - presumably heavier than singlet- should be observed (maybe this has been done now;-)).

  2. The exchange of these particles predicts also charged flavor changing currents respecting conservation of corresponding "isospin" and "hypercharge." For instance, lepton quark scattering e+s → μ+d would be possible. The most dramatic signature of these states is production of muon-positron pairs (for instance) via decays.

  3. Since the Z0 or photon like boson in question has vanishing "isospin" and "hypercharge", it must be orthogonal to the ordinary Z0 which couples identically to all families. There are states particles of this kind and they correspond to superpositions of fermion pairs of different generations in TGD framework. The two bosons - very optimistically identified as 240 GeV and 720 GeV Z0, must be orthogonal to the ordinary Z0. This requires that the phase factors in superposition of pairs adjust themselves properly. Also mixing effects breaking color symmetry are possible and expected to occur since the SU(3) in question is not an exact symmetry. Hence the exotic Z0 bosons could couple preferentially to some fermion generation. This kind of mixing might be used to explain the absence of muon pair signal in the case of 240 GeV resonance.

  4. The prediction for the masses is same as for the first option if the octet and singlet bosons have identical masses for same p-adic mass scale so that mass splitting between different representations would take place via the choice of the mass scale alone.

Could scaled up copy of hadron physics involved?

One can also ask whether these particles could come from the decays of hadrons of a scaled up copy of hadron physics strongly suggested by p-Adic length scale hypothesis.

  1. Various hadron physics would correspond to Mersenne primes: standard hadron physics to M107 and new hadron physics to Mersenne prime M89=289-1. The first guess for the mass scale of "light" M89 hadrons would be 2(107-89)/2=512 times that for ordinary hadrons. The electron pairs might result in a decay of scaled up variant of pseudoscalar mesons π , η, or of η' or spin one ρ and ω mesons with nearly the same mass. Only scaled up ρ and ω mesons remains under consideration if one assumes spin 1.

  2. The scaling of pion mass about 140 MeV gives 72 GeV. This is three times smaller than 240 GeV but this is extremely rough estimate. Actually it is the p-adic mass scale of quarks involved which matters rather than that of hadronic space-time sheet characterized by M89. The naive scaling of the mass of η meson with mass 548 MeV would give about 281 GeV. η' would give 490 GeV. ρ meson with mass would give 396 GeV. The estimates are just order of magnitude estimates since the mass splitting between pseudoscalar and corresponding vector meson is sensitive to quark mass scale.

  3. This option does not provide any explanation for the lack of muon pairs in decays of 240 GeV resonance.

To conclude, family replication phenomenon for gauge bosons is consistent with the claimed masses and also absence of muon pairs might be understood. It remains to be seen whether only statistical fluctuations are in question.

For background see the chapter p-Adic Particle Massivation: New Physics of "p-Adic length Scale Hypothesis and Dark Matter Hierarchy".

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