CMS (LHC) Measurements and Unusual Cosmic Ray Events

Abstract

At the LHC, for the first time, laboratory energies are sufficiently large to reproduce the kind of reactions that occur when energetic cosmic rays strike the top of the atmosphere. The reaction products of interest for cosmic ray studies are produced at small angles, even with colliding beams. Most of the emphasis at the LHC is on rare processes that are studied with detectors at large angles. It is precision measurements at large angles that are expected to lead to discoveries of Higgs bosons and super symmetric particles. CMS currently has two small angle detectors, CASTOR and a Zero Degree Calorimeter (ZDC). CASTOR, at $0.7^{\circ}$ down to $0.08^{\circ}$, is designed to study "Centauro" and "long penetrating" events, observed in VHE cosmic-ray data. As a general purpose detector it also makes measurements of reaction products at forward angles from p-p collisions, which provide input for cosmic ray shower codes. The ZDC is small, 9 cm. wide, between the incoming and outgoing beam pipes out at a distance of 140 m. The ZDC measures neutral objects that follow the direction of the beam at the interaction point. If the long penetrating objects are spectators they could be seen in the ZDC if their charge to mass ratio, Z/A, is less than 0.2.Comment: Invited talk presented at the XVI International Symposium on Very High Energy Cosmic Ray Interactions, ISVHECRI 2010, Batavia, IL, USA (28 June - 2 July 2010). 4 pages, 5 figure