Thursday, March 17, 2011

The 21st Century is Here

Thanks to Carl for pointing out this new CDF paper:
Measurement of the mass difference between $t$ and $\bar{t}$ quarks
(Submitted on 14 Mar 2011)

We present a direct measurement of the mass difference between $t$ and $\bar{t}$ quarks using ttbar candidate events in the lepton+jets channel, collected with the CDF II detector at Fermilab's 1.96 TeV Tevatron ppbar Collider. We make an event by event estimate of the mass difference to construct templates for top quark pair signal events and background events. The resulting mass difference distribution of data is compared to templates of signals and background using a maximum likelihood fit. From a sample corresponding to an integrated luminosity of 5.6 $\textrm{fb}^{-1}$, we measure a mass difference, $\delta (t) = \mathrm{M}_{t} - \mathrm{M}_{\bar{t}} $ $= -3.3 \pm 1.4 \textrm{(stat)} \pm 1.0 \textrm{(syst)}$, approximately two standard deviations away from the CPT hypothesis of zero mass difference. This is the most precise measurement of a mass difference between $t$ and its $\bar{t}$ partner to date.


  1. OK, so for those who are not keeping up to date here: remember that neutrons have a different mass to the so called antineutrons. But as everyone knows, neutrons are made of quarks. It follows that we should expect quarks and antiquarks to have different masses.

    Dammit, we strike the language barrier again! They should not be called antiquarks if they cannot annihilate with quarks. They should be called mirror quarks ... or something else ... of course, there are still antiprotons annihilating with protons, which suggests that two up quarks and a down quark IS like an antiparticle, while two down quarks and an up quark is not.

  2. And to think! Just this afternoon, I was sitting downstairs with my pot of green tea, musing over the quark content of all the light nuclei, up to He3.

  3. The whole thing starts to make sense in that the neutrinos are the worst in terms of CPT invariance, the electrons are the best, while the quarks are midway between.

    I find it kind of amusing that the theoreticians are completely at sea on this. "It's just a 2-sigma" doesn't hold a lot of water after the neutrino data.

  4. Indeed, the 'just a 2 sigma' is a pretty pathetic response after the non observation of fairies, susy corpses and gravitational waves. Yes, remember that the quarks lie on the edge of a tetractys, so they are in a real sense a mixture of charged leptons and neutral leptons.


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