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This report discusses techniques and challenges in studying Galactic Cosmic Rays, with a focus on the desirability of using a single technique to cover multiple spectral features and the exploration of the second knee phenomenon. The report delves into the separation of galactic and extra-galactic cosmic rays, addressing issues such as systematics, composition measurement challenges, and the implications of RHIC results. Various experimental and theoretical presentations are examined to shed light on the nature of the second knee and the origin of galactic cosmic rays. The potential of using different experimental setups, such as the LHC and RHIC, for further studies is explored, aiming to reduce theoretical uncertainties in the field.
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“Above the Kneepcap” Working Group Report C. C. H. Jui April 27, 2005
General Discussion on Apr.26 • Working Group had a ~1 hr discussion on the following topics: • The desirability of covering multiple spectral features (knee, second knee, ankle, GZK?) with a single technique, if not a single experiment (Akeno 1km2 is cited as an example to be inspired by). • The second knee • Separation of Galactic and Extra-Galactic cosmic rays
A Single Technique to Measure Them All • It was pointed out that the Akeno example is not without its challenages: • Ne-to-energy conversion varies with energy. • The systematics of the measurement probably also varies strongly over 4 decades of energy • Composition measurement is especially challenging: • Current Shower Models predict too few muons at higher energies. • Yesterday: example of too many muons in Shower Models
Techniques • RHIC results suggest that muon production should be even lower than the Shower Models predict • Forward calorimeters at LHC will be analyzed against air Shower Models • this will help to reduce many of the theoretical systematic uncertainties, including perhaps the muons problem
Techniques • It was also pointed out that the Xmax technique has not been cross-calibrated • FLASH thick-target experiment has demonstrated that light yielded follows shower size • Possibility of using RHIC for further thick target studies?
Second Knee • Considerable interest expressed concerning the second knee: • Experimental evidence: energy adjustments required
Nature of the Second Knee? • Question: What is the Second Knee:? • Several Theoretical Presentations will address whether the Second Knee is a source- or propagation effect • Need to separate out Galactic/Super-Galactic cosmic rays
Galactic Cosmic Rays • Recent Hess observation of hard TeV gamma sources and the consistency of their spectral indices suggest that shock acceleration does indeed occur around SNR (at least of electrons) • Can the Upper Limit of this mechanism be determined experimentally from the TeV gamma ray experiments? • Stay tuned for Rowell Presentation
Galactic Cosmic Rays • Several Presentations on the topic of the origin of the galactic cosmic rays • The separation of galactic/super-galactic components will likely depend on composition-tagged anisotropy studies • Some reservation expressed about the suitability of fluorescence detectors for this given the variable seasonal exposure • Not clear how well a ground array can measure the composition given the uncertainty of muon yield.
