## Friday, March 27, 2009 ... //

### F-theory footprints at the LHC

Could you be an experimenter in particle physics? Click the picture to zoom in and try to find the footprint. Hint for Al Gore: it is not a carbon footprint.

If you succeeded in this simpler task, you may also try to find the person on the picture whose footprint appeared at the LHC.

Important: if you use Google Images to search for "Cumrun", be sure that your anti-porn filter is turned on, otherwise you will also find pictures showing "cum run".

Were you as bright an observer as the girl at Princeton who found a bug with the LHC, impressing another girl who wrote about it for FoxNews? :-)

By the way, Cumrun Vafa is just giving talks in his homeland, in Tehran.

More seriously, Jonathan Heckman, Gordon Kane, Jing Shao, and Cumrun Vafa have written a 85-page paper that I recommend the expert readers,
The footprint of F-theory at the LHC
Thirty-seven pictures are included. F-theory model building is a recent minirevolution in theoretical physics, focusing on a previously understudied, highly geometrical, and very predictive corner (or "projection") of the string-theoretical configuration space.

They use the general footprint method designed by Kane, Kumar, and Shao (I, II) to address the inverse LHC problem (the reconstruction of the right theory from the LHC data) and sketch how to distinguish the F-theoretical vacua from other minimal supersymmetric standard models (or mSUGRA) that can arise in string theory.

While the validity of string theory is a pretty much settled fact, the identity of the relevant compactification remains a big unknown. There are theoretical tools to direct people's research. With the LHC, there will be new observational data, too. It is very clear that these authors are doing the right thing - which is to actually develop rational and quantitative methods to deduce insights out of the available data, whatever they are going to be.

Results exceed the expectations

But once the work is done, they have much more than the right approach.

Already in the previous papers by Kane et al., it turned out that with a reasonable integrated luminosity, comparable to 5 inverse femtobarns (less than the first year's expectations), one can distinguish these models rather reliably. All major, well-motivated classes of string-theoretical vacua are mapped to very small subregions in the LHC signature space: the resolution decreases if you consider more contrived models (e.g. with many messengers). In other words, string theory is highly predictive as long as you focus on highly motivated or "minimal" vacua of some kind.

This F-theoretical model building leads to a very characteristic, universal, non-field-theoretical shift of scalar superpartner masses away from the soft SUSY breaking prediction - a shift by 50 GeV or more that can be described as a result of a stringy Green-Schwarz-like mechanism, allowing to gauge a U(1) symmetry that would be anomalous in the truncated low-energy effective field theory.