# How can Kaluza-Klein particles be told apart from winding modes at the LHC?

Ive already asked this in the comments below this article http://profmattstrassler.com/articles-and-posts/some-speculative-theoretical-ideas-for-the-lhc/extra-dimensions/how-to-look-for-signs-of-extra-dimensions/ from Prof. Strassler but did not get a satisfactory answer...

In the article Prof. Strassler explains that a possible sign of extra dimensions at the LHC could be the detection of Kaluza-Klein particles. The energy (or mass squared) spectrum of the corresponding particle tower would have a step size proportional to 1/r (where r is the radius of a compact extra dimension).

Now Im wondering how such a (hypothetical) KK particle candidate can be told apart from a winding mode particle (with the step size of the energy spectrum proportional to r) which is probably more easily produced depending on the size r of the extra dimension ? By the way what's the actual state of these searches for extra dimensions considering the data already available ?

Clarification

Considering an extra dimension that is much larger than the particle, the KK modes with the 1/r spectrum arise from the quantized angular momentum a particle can have due to it' movement in the extra dimension. If the extra dimension is smaller the particle can wind around the extra dimension leading to the winding mode particles. For these the energy spectrum is determined by the potential energy of stretching. The spectra of the KK and winding modes are T-dual to each other.

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By the way what's the actual state of these searches for extra dimensions considering the data already available ?

The LHC experiments are looking for extra dimensions in various channels (search for "extra dimensions LHC) and putting limits. At the moment the standard model reigns.

They are trying for KK s too, though still at a planning stage.

I do not know what a winding mode particle is, but I expect the decay products, which are the main thing measured at LHC experiments, will make the distinction possible.

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Thanks @anna v. There seems to be something wrong with the first link; upon clicking it says "Collection Articles Not Found". Considering an extra dimension that is much larger than the particle, the heavier KK modes with the 1/r spectrum arise from the quantized angular momentum a particle can have in the extra dimension. If the extra dimension is smaller the particle can wind around the extra dimension leading to the winding mode particles (if they are not points ... ;-P). For these these the energy spectrum is determined by the potential stretching energy –  Dilaton Jan 15 '12 at 14:39
which leads to step size to be proportional to r. The winding modes and the KKs are T-dual to each other. Ive stolen this from Prof. Susskind's lectures :-). So Im aking myself if the winding particles should start being more easy to get (if they exist) if there are strong limits for the size of the extra dimensions ...? –  Dilaton Jan 15 '12 at 14:45
But are winding modes particles necessarily? The first link is from a search of the CERN preprints. cdsweb.cern.ch/collection/Articles%20%26%20Preprints?ln=en asking for "extra dimensions LHC" –  anna v Jan 15 '12 at 21:16
Now the link works :-). I`ve just found a picture of the spectra of the KK and the winding modes: web.me.com/kenmcelvain/StringTheory/StringTheory_C9_files/…. If I understand this right they both correspond to particles which are similar to but more massive than the known particles. The "extra mass" is due to the kinetic energy of the movement IN the extra dimensions for the KKs or due to the additional stretching potential energy for the winding modes which are wound AROUND, dependent on the size of the extra dimensions. –  Dilaton Jan 15 '12 at 21:41
Could be. Or for all I know someone upvoted your question by accident, didn't realize within the first 5 minutes, and then couldn't undo it until you edited. –  David Z Jan 18 '12 at 21:07