Editing Kaluza–Klein theory (section)

== Empirical tests ==
No experimental or observational signs of extra dimensions have been officially reported. Many theoretical search techniques for detecting Kaluza–Klein resonances have been proposed using the mass couplings of such resonances with the [[top quark]]. An analysis of results from the LHC in December 2010 severely constrains theories with [[large extra dimensions]].<ref name="arxiv.org 1">{{cite journal |title=Search for microscopic black hole signatures at the Large Hadron Collider |year=2011 |doi=10.1016/j.physletb.2011.02.032 |arxiv=1012.3375 |last1=Khachatryan |first1=V. |last2=Sirunyan |first2=A. M. |last3=Tumasyan |first3=A. |last4=Adam |first4=W. |last5=Bergauer |first5=T. |last6=Dragicevic |first6=M. |last7=Erö |first7=J. |last8=Fabjan |first8=C. |last9=Friedl |first9=M. |last10=Frühwirth |first10=R. |last11=Ghete |first11=V.M. |last12=Hammer |first12=J. |last13=Hänsel |first13=S. |last14=Hartl |first14=C. |last15=Hoch |first15=M. |last16=Hörmann |first16=N. |last17=Hrubec |first17=J. |last18=Jeitler |first18=M. |last19=Kasieczka |first19=G. |last20=Kiesenhofer |first20=W. |last21=Krammer |first21=M. |last22=Liko |first22=D. |last23=Mikulec |first23=I. |last24=Pernicka |first24=M. |last25=Rohringer |first25=H. |last26=Schöfbeck |first26=R. |last27=Strauss |first27=J. |last28=Taurok |first28=A. |last29=Teischinger |first29=F. |last30=Waltenberger |first30=W. |journal=Physics Letters B |volume=697 |issue=5 |pages=434–453 |bibcode=2011PhLB..697..434C |s2cid=122803232 |display-authors=1 |collaboration=CMS Collaboration}}</ref>

The observation of a [[Higgs boson|Higgs]]-like boson at the LHC establishes a new empirical test which can be applied to the search for Kaluza–Klein resonances and supersymmetric particles.
The loop [[Feynman diagram]]s that exist in the Higgs interactions allow any particle with electric charge and mass to run in such a loop. Standard Model particles besides the [[top quark]] and [[W and Z bosons|W boson]] do not make big contributions to the cross-section observed in the {{nowrap|H → γγ}} decay, but if there are new particles beyond the Standard Model, they could potentially change the ratio of the predicted Standard Model {{nowrap|H → γγ}} cross-section to the experimentally observed cross-section. Hence a measurement of any dramatic change to the {{nowrap|H → γγ}} cross-section predicted by the Standard Model is crucial in probing the physics beyond it.

An article from July 2018<ref name="arxiv.org 2">{{cite journal |title=Limits on the number of spacetime dimensions from [[GW170817]] |year=2018 |doi=10.1088/1475-7516/2018/07/048 |arxiv=1801.08160 |last1=Pardo |first1=Kris |last2=Fishbach |first2=Maya |last3=Holz |first3=Daniel E. |last4=Spergel |first4=David N. |journal=Journal of Cosmology and Astroparticle Physics |volume=2018 |issue=7 |page=048 |bibcode=2018JCAP...07..048P |s2cid=119197181 }}</ref> gives some hope for this theory; in the article they dispute that gravity is leaking into higher dimensions as in [[brane theory]]. However, the article does demonstrate that electromagnetism and gravity share the same number of dimensions, and this fact lends support to Kaluza–Klein theory; whether the number of dimensions is really 3&nbsp;+&nbsp;1 or in fact 4&nbsp;+&nbsp;1 is the subject of further debate.