An anomaly was discovered in the CERN data - is the new physics a horse or a zebra?

If there is a standard deviation from the prediction, the experimenters try to figure out if something is wrong with the data. They repeatedly check the consistency of the machines and the statistics and they can say, with certainty, that there is a real discrepancy.

If there is a standard deviation from the prediction, the experimenters try to figure out if something is wrong with the data. They repeatedly check the consistency of the machines and the statistics and they can say, with certainty, that there is a real discrepancy.

If you hear hoofbeats, logic says they were most likely caused by a horse. However, there is still some chance that they hear a zebra. Physicists at the LHCb particle accelerator in Sarn near Geneva, apply this logic to an unusual finding that emerged from analyzing data about a particle called food B.

One in a million B-foods decays to a cation (K)-stimulating food and two muions. The decay can occur in several different ways, and therefore physicists classify them in what they call "bins". The standard model accurately predicts the chance of all angles of all types of decay in each 'bin'. The experiments will be able to measure this probability, so it is observable. Any difference between the observations and the prediction may indicate new physics.

Nicola Serra of the LHC, one of the analysts of the 2011 B-mass decay data, and his colleagues found such a difference. "Most of the observations we examined in this analysis were close to the expectations of the standard model, but in one observation we saw a discrepancy with the model." said.

In 'sigma' terms that physicists use to describe the significance of the results, the difference between the prediction and the actual measurements is 3.7 sigma - which may indicate new physics, but more data is still needed to confirm this. When they considered the likelihood of observing a certain standard deviation in all the data they had studied so far, the likelihood dropped to 2.8 sigma or a half percent chance that the standard deviation is caused by statistical fluctuation (the gold standard of detection is 5 sigma as we recall from the Higgs boson).

A team of theorists looked at the same decay and added additional observations to those the LHCb group included. They discovered a consistent pattern of standard deviations that raised the sigma to 4.5. This is almost at the level of a discovery, but still in the field of parameters that the measurements represent the presence of new physics. These parameters are more inclusive than those used by the LHCb team members.

"The theoretical interpretation is very interesting, and it cannot be denied" says Serra. "Shensin, I must focus on the data itself and not on the interpretation. If we see something different from the forecast, it is important to understand whether the pattern is real or not."

If there is a standard deviation from the prediction, the experimenters try to figure out if something is wrong with the data. They repeatedly look at the consistency of the machines and the statistics and they can say, with certainty, that there is a real discrepancy.

"The experimental article only shows the data. The theoretical article is the one that gives the interpretation. It's about two pieces of the puzzle and they both fit together beautifully," says Joachim Matias, a theorist from the University of Barcelona and one of the authors of the article. "The experimenters found a standard deviation and the theorists showed that it can be explained for the first time within the framework of a consistent picture."

The data from these particular analyzes of the LHCb are promising, and are encouraged by the theoretical possibilities noted in the paper arising from the aggregated LHCb data. However, only when the entire data set receives the same cross-checking treatment will the physicists be able to determine whether this decay is a horse or a zebra.
The LHCb team has begun analyzing the entire database, thus tripling the amount of data examined compared to those appearing in the article. They expect to update the results next year. Both experimentalists and theorists say that only a joint effort between their teams will allow them to determine whether the anomaly of the new physics is indeed real.

The particle accelerator is currently closed for renovations and is scheduled to reopen in 2015 at twice its current power.

For information on the CERN website