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Anna Phan | USLHC | USA

View Blog | Read Bio

Measuring matter-antimatter asymmetries…

I’ve mentioned before that measuring CP violation is important in understanding why we have a matter dominated universe. So far, CP violation has been observed in the decay and mixing of neutral mesons containing strange, charm and bottom quarks and most measurements have been consistent with theory.

However, there is one measurement which has found evidence for significant CP violation in the decays of neutral B mesons, beyond what is expected from theory. In 2010, with an update in 2011, reported an interesting observation: that the number of events containing two positively charged muons is lower than the number of events containing two negatively charged muons. Like-sign dimuons can be produced from the decays of pairs of neutral B mesons, since they can mix between their particle and antiparticle states. A difference between the number of positive and negative dimuons is an indication of CP violation. The observed difference was close to 1% and 3.9σ away from the theory prediction. The analysis could not distinguish between the two different neutral B mesons, \(B^0_d\) and \(B^0_s\), so the difference had to be expressed in terms of two asymmetries: \(a^d_{sl}\), the semileptonic asymmetry of \(B^0_d\) mesons, and \(a^s_{sl}\), the semileptonic asymmetry of \(B^0_s\) mesons.

At ICHEP, DØ presented direct measurements of \(a^d_{sl}\) and \(a^s_{sl}\), by looking at the decays, \(B^0_d \rightarrow D^{(*)\pm}\mu^\mp X\) and \(B^0_s \rightarrow D_s^\pm\mu^\mp X\).

On the left, I have made a plot of these three results, comparing them to the Standard Model predictions. You can see that all three results are somewhat inconsistent with the prediction, which could indicate a contribution from new physics.

But of course, DØ isn’t the only experiment that is able to measure these asymmetries…


\(a^d_{sl}\) has been previously measured by both Belle and BaBar using \(B^0_d\) meson pairs produced by the decay of the \(\Upsilon(4S)\) meson and the results combined by the Heavy Flavour Averaging Group (HFAG).

And… LHCb released a preliminary result for ICHEP, measuring \(a^s_{sl}\) using \(B^0_s \rightarrow D_s^\pm\mu^\mp X\) decays.

On the right, I’ve added these results to the DØ ones, and now you can see that the situation now isn’t as compelling for new physics, with the BaBar, Belle and LHCb results all being compatible with the theory.

However, all experimental results are still compatible within two standard deviations, so new results are needed to definitively resolve the issue… Stay tuned to see if this is where evidence of new physics is found!


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  • Santilli’s studies on the mystery to detect antimatter

    Your personal belief that there is a matter-antimatter asymmetry is based on the unspoken conjecture that Einstein special relativity can represent antimatter and, since Einstein does not predict antimatter,m antimatter does not exist according to gurus at Harvard, Princeton & Co. My God!

    The sole conjugation for antimatter admitted by Newton, Galileo and Einstein is the sign of the charge. Therefore, their theories have NO serious scientific prediction for antimatter asteroids, stars and galaxies since they are NEUTRAL.

    To understand how far reality is from your view, you should read the following paper in print at the American Institute of Physics by Prof. R. M. Santilli (CV: http://www.world-lecture-series.org/santilli-cv)

    The Mystery of Detecting Antimatter Asteroids, Stars and galaxies
    Ruggero maria Santilli

    You should then study the resolution of the basic insufficiencies for antimatter by Newton, Galileo and Einstein in the summary monograph

    Isodual Theory of Antimatter with Application to Antigravity,
    Grand Unification and the Spacetime Machine,
    R.M.Santilli, Springer 2001

    and, for numerous specialized papers, you should consult the international conference held in the field

    San Marino Workshop on Astrophysics and Cosmology for
    Matter and Antimatter September 5 to 9, 2011

    A Post Ph. D. Course for ‘serious” studies in antimatter is part of the forthcoming

    2012 Seminar Course on Hadronic Mechanics
    To be held as part of the International Meeting
    CNAAM 2012,
    Kos, Greece, 19-25 September 2012
    Link to Conference main Website

    Preliminary outline of the HM Course

    Best Wishes

    Richard Anderson
    The R. M. Santilli Foundation

  • flashgordon

    Einstein’s Special and General relativity suggest that time can be manipulated. Quantum mechanics has these time symmetries of particles; could there be some way of connecting or creating quantum gravity by trying to relate this time phenomenon?

  • cb

    Is this supposed to be a joke? Sometimes sarcasm doesn’t come through in writing.