Charming Results from LHCb Conference: Has The LHC Finally Found Some New Physics?

There may finally be some great news coming out of LHC. After a string of negative results, LHC presents the first ever signals of CP violation in the charm quark sector. This might explain the very origin of matter, in the sense that it explains why matter dominates the Universe. Curiously, the awesome result comes from LHCb, one of the side’ experiments and not from the premier ATLAS and CMS collaborations.

An explanation of the results:
The LHCb Detector

What is found wasn’t quite expected!

This is what LHCb is saying. The observed asymmetries in the decay processes have been noticed in the charm-quark section, giving rise to the D-mesons. The D-mesons are a bound state of the charm quarks, which is one of the heaviest quarks in the Standard Model. The two relevant quarks are the D0 (D-zero) made up of a charm and an anti-up quark and the D0bar (D-zero bar) made up of anti-charm and an up quark. The LHCb looked into the decay of these relatively stable bound states into CP invariant states, like the Kaons or the pions. The D0 should decay into Ï€+Ï€ or κ+κ, and so should the D0bar at equal rates, if CP were an exact symmetry. What the LHCb found was that this is not the case and the deviation in the rates is substantial and LHCb claims a 3.5 sigma confidence level on this!  

The amount of deviation

The Standard Model does predict that CP is not an exact symmetry in the quark sector, but only an approximate one. Still it gives a value of mixing, based on the famous Cabbibo angle, which is close to zero. What LHCb found was that this mixing value is close to 0.82% +/- 0.24%, which is a significant deviation from the Standard Model (at a 3.5 sigma confidence level).

These are still preliminary results. The LHCb is not as sophisticated as the ATLAS or CMS and cannot handle the high beam luminosities that the premier detectors can. Thus, it has collected less data than either of ATLAS and CMS. Less data also means more noise or spurious signals.

More data and analysis will establish this newfound signature of Beyond Standard Model (BSM) physics.

Here’s more:
An explanation of the results from us:

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Debjyoti Bardhan

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

  • mfb

    I am used to the fact that most authors are like “oh, LHC is not only ATLAS and CMS”? But your comparison in the last paragraph is just wrong.

    “The LHCb is not as sophisticated as the ATLAS or CMS”?
    It depends on how you define sophisticated. In general, if there is a particle within the detector acceptance, LHCb can measure it with a better precision (position, momentum, lifetime) and a much better particle identification.
    LHCb has to use a lower luminosity as trade-off for that, that is true. However, it writes much _more_ events on tape than ATLAS and CMS, as most interesting channels in flavour physics are much more frequent than top/Higgs/SUSY events.

    And finally, giving standard deviations already account for statistical uncertainties. A 3.5sigma-measurement is the same significance, independent of the size of the actual dataset.

    • Debjyoti Bardhan

      Thank you for the comment. I didn’t know that LHCb writes many more events than ATLAS or CMS. Thanks for informing me of that.

      You’re obviously right about the 3.5 sigma measurements, but generally as more data comes in, the confidence levels change.

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