Abstract
This review discusses some recent developments in the study of ultrahigh-energy interactions using cosmic-ray γ-family data obtained with emulsion chambers at mountain altitudes. The apparent excess of the event rate at large transverse momenta with respect to the prediction based on perturbative QCD indicates new interaction mechanisms at E lab ≃104–105 TeV, an energy regime beyond the reach of existing colliders. To reconcile the data with a compositeness model of quarks, the characteristic energy scale would have to be as low as Λc≤0.1 TeV, in conflict with the lower limit of Λc>1.4 TeV or a possible value of Λc≃1.6 TeV obtained by the CDF experiment at Tevatron. Possible new physics beyond the standard model, together with future experiments at the LHC, are also discussed.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
