Are we there yet?

Two sets of exciting results have emerged from CERN this week, illustrating the breadth of our research programmes, as well as the need to keep our eyes firmly on the road ahead. When new results emerge, it is almost irresistibly tempting to over-interpret what they seem to be telling us, but it’s at times like these that we need to remain circumspect, and not read more into the data than is really there.


The first physics to be presented from CERN this week came from the LHC experiments, which presented their latest results at the Lepton-Photon symposium in Mumbai starting on Monday 22 August. These included new results on Higgs searches. Not surprisingly to physicists who have been around for as long as I have, an excess seen at 145 GeV a month ago and presented at the EPS conference in Grenoble looks somewhat less convincing with more data analysed. It may still prove to be real, but as we said clearly at the EPS conference, it could equally well be a statistical fluctuation. Only more data will tell. What we do know now is that if the Higgs exists, it is almost certainly lighter than about 145 GeV or heavier than 466 GeV. These are precisely the regions where the Higgs particle is harder to disentangle from backgrounds. If it is there, as we suspect it might be, then we’ll need much more data before we can find it or definitively exclude it. Either would be a great result. Exciting though it was to see the excess at the EPS-conference, it’s never wise to over interpret an early result.

The same message of caution applies to the second major set of results to come from CERN this week. On Thursday, the journal Nature carried the first paper to be published by the CLOUD experiment. CLOUD brings together an international and interdisciplinary team of scientists who are using CERN expertise and accelerators to explore the physics underlying cloud formation. With current concerns about climate change, this is clearly important work, and over the long term will provide important data for better understanding the climate. But these are early days. CLOUD’s first results indicate that vapours previously thought to account for the nucleation of atmospheric aerosol particles that eventually lead to cloud formation are insufficient to explain atmospheric observations. The results also show that the rate of aerosol formation from these vapours is enhanced by ionising radiation from cosmic rays. What this tells us is that additional vapours must be involved, and it leaves open the possibility that cosmic rays could influence cloud formation: nothing more, nothing less. The next steps for CLOUD are to identify those other vapours, and to study the processes by which aerosols grow to become the condensation nuclei on which cloud droplets form. This will take time.

The LHC and CLOUD research programmes could hardly be further apart, but both are long journeys that are just at their beginning.  Like any long journey, the start is always exciting and full of anticipation. The middle tends to be accompanied by choruses of ‘are we there yet’ from the back seat, and the end is where the sense of anticipation is fulfilled. Are we there yet? No, but we’re well on our way.


Rolf Heuer