PhD defense by Sune Jakobsen – University of Copenhagen

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PhD defense by Sune Jakobsen

Commissioning of the Absolute Luminosity For ATLAS detector at the LHC

Abstract: The LHC (Large Hadron Collider) has opened a new energy regime for measurements¨in particle physics. To normalize the measurements and express them in terms of cross-sections it is necessary to know the absolute luminosity. Whereas the ATLAS experiment has numerous methods at its disposal to measure the relative luminosity variations from one run to the next, the absolute luminosity calibration relies solely on van der Meer scans of beam separation. To cross check and improve the precision, ATLAS has built a sub-detector called ALFA (Absolute Luminosity For ATLAS) to measure protons scattered elastically at very small angles, the rate of which relates to the absolute luminosity. It is positioned inside the beam pipe 240 m from the interaction point and requires therefore special beam conditions, very high β*, in order to operate.  This thesis describes the commissioning of ALFA, its integration into ATLAS and the first physics results obtained with it.