15.4: Monday 11-12 ------------------ Exercise 2.1: -The more accurate acceptance of AMS02 detector is 0.5 m2 sr. Be free to calculate more accurate event number estimates! -1d) Also other ways of estimating the intensity above E=10^{18} eV than the one presented in the model solution do exist and may give more accurate results. -An exercise task aiming to clarify the definitions of intensity and acceptance will be done for the next exercise. Exercise 2.2: -We go the exercise through on the next exercise session. Exercise 2.3: -One can also approach to solve the problem by using doppler shift formula for the CMB photon. -The calculated answer of E=3*10^{20} eV is more than the value given in the lectures. This is most likely due to the simplification used: CMB radiation is not monochromatic, i.e. photons of single energy. Exercise 2.4: -It was given in the exercise assigment to estimate the energy and mass. More precisely, the term "mass" denotes the mass number A of a nucleus. -A more accurate look at the shower profile figure given in the task assigment gives X_{max}=820 g/cm2. Extrapolation of the figure on lecture slide 3.46 is not easy, but the conclusion about the primary CR being most likely a light nuclei (H,He,...) holds. -b) Many arguments for placing the detectors at high altitude regions other than the ones given in the model answer do exist, for example that the attenuation of fluorescent light is less for shorter distances from the light source. For understanding the definition of shower depth it might be useful to look at the labels of the lower and upper axis of the figure in the lecture slide 3.20. The units g/cm2 denote the total mass of the column of air above an area of 1 cm2.