A Dark Matterline search using 3D-modeling of Cherenkov showers below 10 TeVwith VERITAS

by Nils Hkansson

Institution: Universitt Potsdam
Year: 2017
Posted: 02/01/2018
Record ID: 2222103
Full text PDF: https://publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/39767


Dark matter, DM, has not yet beendirectly observed, but it has a very solid theoretical basis. Thereare observations that provide indirect evidence, like galacticrotation curves that show that the galaxies are rotating too fastto keep their constituent parts, and galaxy clusters that bends thelight coming from behind-lying galaxies more than expected withrespect to the mass that can be calculated from what can be visiblyseen. These observations, among many others, can be explained withtheories that include DM. The missing piece is to detect somethingthat can exclusively be explained by DM. Direct observation in aparticle accelerator is one way and indirect detection usingtelescopes is another. This thesis is focused on the lattermethod. The Very Energetic Radiation Imaging Telescope ArraySystem, V ERITAS, is a telescope array that detects Cherenkovradiation. Theory predicts that DM particles annihilate into, e.g.,a pair and create a distinctive energy spectrum when detected bysuch telescopes, e.i., a monoenergetic line at the same energy asthe particle mass. This so called smoking-gun signature is soughtwith a sliding window line search within the sub-range 0.3 10TeV of the VERITAS energy range, 0.01 30 TeV. Standardanalysis within the VERITAS collaboration uses Hillas analysis andlook-up tables, acquired by analysing particle simulations, tocalculate the energy of the particle causing the Cherenkov shower.In this thesis, an improved analysis method has been used.Modelling each shower as a 3Dgaussian should increase the energyrecreation quality. Five dwarf spheroidal galaxies were chosen astargets with a total of 224 hours of data. The targets wereanalysed individually and stacked. Particle simulations were basedon two simulation packages, CARE and GrISU. Improvements have beenmade to the energy resolution and bias correction, up to a fewpercent each, in comparison to standard analysis. Nevertheless, noline with a relevant significance has been detected. The mostpromising line is at an energy of 422 GeV with an upper limitcross section of 8.10 10^24 cm3 s^1 and a significance of 2.73 , before trials correction and 1.56 after. Upper limitcross sections have also been calculated for the annihilationprocess and four other outcomes. The limits are in line withcurrent limits using other methods, from 8.56 10^26 6.61 10^23 cm3s^1. Future larger telescope arrays, like the upcomingCherenkov Telescope Array, CTA, will provide better results withthe help of this analysis method. Dunkle Materie, DM, wurde noch nichtdirekt beobachtet, aber die Theorie ist sehr solide. Es gibtBeobachtungen, die als indirekte Beweise gelten, z.B. galaktischeRotationskurven, die besagen, dass Galaxien zu schnell rotieren umohne eine zustzliche Massenkomponente zusammenhalten zu knnen,oder elliptische Zwerggalaxien, die massereicher sind als diesichtbare Materie vermuten lsst. Diese Beobachtungen knnten z.B.mit dem Vorhandensein von DM erkrt werden,Advisors/Committee Members: Pohl, Martin (advisor).