Average shape of longitudinal shower profiles measured at the Pierre Auger Observatory

The average profiles of cosmic ray shower development as a function of atmospheric depth are measured for the first time with the Fluorescence Detectors at the Pierre Auger Observatory. The profile shapes are well reproduced by the Gaisser-Hillas parametrization at the 1% level in a 500 g/cm2 interval around the shower maximum, for cosmic rays with log(E/eV) > 17.8. The results are quantified with two shape parameters, measured as a function of energy. The average profiles carry information on the primary cosmic ray and its high energy hadronic interactions. The shape parameters predicted by the commonly used models are compatible with the measured ones within experimental uncertainties. Those uncertainties are dominated by systematics which, at present, prevent a detailed composition analysis.Comment: presented at the UHECR 2018 (Paris, October 2018

The muonic longitudinal shower profiles at production

In this paper the longitudinal profile of muon production along the shower axis is studied. The characteristics of this distribution is investigated for different primary masses, zenith angles, primary energies, and different high energy hadronic models. It is found that the shape of this distribution displays universal features similarly to what is known for the electromagnetic profile. The relation between the muon production distribution and the longitudinal electromagnetic evolution is also discussed

The interplay between the electromagnetic and the muonic longitudinal profile at production

The electromagnetic and the muonic longitudinal profile at production enclosure important information about the primary particle and the hadronic interactions that rule the shower development. In fact, these two profiles provide two different insights of the shower: the electromagnetic component gives a measurement of the energy and the strength of the neutral pion channel; while the muonic profile, being intimately related with the charged mesons decays, can be used as a direct probe for the high energy hadronic interactions. In this work we explore the interplay between the electromagnetic and muonic profiles, by analysing their phenomenologic behaviour for different primary masses and energies, zenith angles, and also different high energy hadronic interaction models. We have found that the muonic longitudinal profile at production displays universal features similar to what is known for the electromagnetic one. Moreover, we show that both profiles have new primary mass composition variables which are fairly independent of the high energy hadronic interaction model. Finally we discuss how the information in the electromagnetic and the muonic longitudinal profile can be combined to break the degeneracy between the primary mass composition and the high energy hadronic physics.Comment: 5 pages, to appear in conference proceedings of International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2012), Berlin, German

Synthetic studies of archaeal lipids and related long-chain isoprenoids

Archaea have been classified as a separate domain of life since 1977, and is the least well known of all three. Even though many species of archaea thrive under “normal” conditions, they are most well known for their ability to proliferate under what we consider “extreme” conditions. Due to key structural differences they are able to adapt to withstand extreme temperatures, and a range of acidic, alkaline and high salinity conditions. This thesis focusses on one of the key adaptations that archaea have made in order to survive under extreme conditions, namely their unique membrane composition. Unlike bacteria and eukaryotes, archaea have a bi-layer membrane which is formed by membrane spanning lipids. These are very large macrocyclic lipids that span the membrane, offering increased rigidity. Furthermore, to make the membrane even more resistant to high temperatures and acidic and alkaline conditions, the branched isoprene core is connected to the glycerol backbone via ether bonds, instead of ester bonds as in bacteria and eukaryotes. The biosynthesis of these macrocyclic lipids has been resolved allready to a great extent in the past years. The construction of the isoprene tail is well understood, and the coupling of the tails to the glycerol backbone(s) as well. However, there are still some key biosynthetic transformations that are not well understood. The most significant conundrum that still is unknown, is how the macrocycle is formed. This thesis employs the art and science of total synthesis as a framework to gain a a better understanding of the biosynthesis of archaeal lipids. We have taken a synergistic approach together with the Driessen microbiology group (GBB, university of Groningen) towards this goal. We provide synthetic molecules that they in turn can use to investigate biosynthetic processes