The LHC is nearing the end of a long overnight run that started with a record luminosity of 3/ub/s. It is already the first run to collect over 100/nb (100 inverse nanobarns) in one go and it has another hour to run before they plan to terminate it. With luck they will be able to repeat this most days throughout August enabling them to collect 3/pb (3000 inverse nanobarns) this month which is about 10 times the data used for the ICHEP talks. After that they will start a rapid exponential growth of luminosity until the end of this year that should enable them to collect 1/fb (a million inverse nonabarns) by the end of 2011 when the LHC will shut down for further maintenance. Meanwhile the Tevatron continues to steadily collect data at a higher rate but lower energy and waits to hear how long it can continue.
That makes this a great time to play the game of guessing what will be discovered when and where. It is a game that anyone can play whether they are a humble independent blogger like myself or a full-time phenomenologist guru like John Ellis. Those who are insider members of one of the experimental collaborations will have to be careful not to reveal unpublished results but for the rest of us it is harmless fun.
Tommaso Dorigo looks to a 4th generation quark as the next discovery based on excesses above background for high mass events, now seen in both CDF and DZero at the Tevatron. In the end he cops out and says the signal is too weak and he thinks it will be a while before new physics is seen.
Lubos Motl has been excited about supersymmetry with the likelihood of a light Higgs and some excesses in channels where supersymmetry is supposed to live. The mass likelihoods for Higgs are represented by this plot from this presentation. Remember there could be more than one Higgs if supersymmetry is right.
Peter Woit reports a claim that early results from the LHC have already ruled out parts of the parameter space of supersymmetry and asks how long it will be before supersymmetry is ruled out. Nobody was expecting a high chance of seeing supersymmetry with so little data from the LHC so the impact on its parameter space so far must be very small. There is a small chance that evidence for new physics including supersymmetry could be seen this year in dijet or dimuon events at high mass if the right sort of particle exists. It is also even possible that Fermilab already have the evidence for a supersymmetry style Higgs and are going through a careful process of review and approval that could take several months.
To rule out supersymmetry if it is not there would take a little longer. Eliminating supersymmetry at the electroweak scale would require the full Higgs sector to be explored. If the Higgs is light as supersymmetry favours then it will take about 16 inverse femtobarns to cover the whole mass range looking for a 3-sigma signal. Fermilab could reach that point around 2013 if they are allowed to continue and their detectors withstand the potential radiation damage.
To convincingly rule out supersymmetry will however require the full force of the LHC. Taking Steve Meyers predictions for LHC luminosities as shown in this table, we can see that it should be around 2014 before they have enough data to rule out electroweak scale supersymmetry. Of course there may be another form of supersymmetry at much higher energies but that would be something very different that could not easily account for the effects that supersymmetry is meant to explain in the Higgs sector.
So if it is time for me to place my chips on the table I will bet on growing evidence for supersymmetry from now until end of 2011, but with the likelihood that we will have to wait until about 2014 for all the full details to emerge. If a fourth generation exists there is no reason to expect it at around this mass scale so I don’t expect to see it. Tommaso is probably right that the Tevatron excesses are due to something else.
If anyone thinks something else will unfold, now is the time to say it.