Abstract
A first alignment of the LHCb Vertex Locator has been obtained from beam induced tracks at the LHC. A 450 GeV/ c protons were collided on a beam absorber during the LHC synchronisation tests of the anti-clockwise beam in August and September 2008. The resulting particle tracks have been reconstructed by the Vertex Locator. This was the first full reconstruction of tracks induced by the LHC beam. The quality of the data obtained is discussed. A total of 2200 tracks were reconstructed from the full data sample, and a first spatial alignment was obtained. The detector is aligned to an accuracy of 5 μ m in the sensor plane. The results confirm that all detector modules have not been displaced from their surveyed positions by more than 10 μ m .
Highlights
The Large Hadron Collider (LHC) at CERN will collide bunches of up to 1011 protons at a centre of mass energy up to 14 TeV (5.5 TeV) and a design luminosity up to 1034 cm−2s−1 (1027 cm−2s−1)
This paper is structured as follows: a brief description of the VErtex LOcator (VELO) and of the commissioning is given in Section 2; the synchronisation test is described in Section 3 and the VELO data taking configuration in Section 4; the calibration of the VELO timing is discussed in Section 5; the track reconstruction is presented in Section 6; Section 7 illustrates the results obtained by offline reprocessing of the data with the correct parameters for the data acquisition boards; Section 8 describes the module alignment results; the measured spatial resolution of the VELO is shown in Section 9; Section 10 summarises the main conclusions
The first LHC beam induced tracks have been reconstructed in the LHCb VELO
Summary
The Large Hadron Collider (LHC) at CERN will collide bunches of up to 1011 protons (and 7 · 107 heavy ions) at a centre of mass energy up to 14 TeV (5.5 TeV) and a design luminosity up to 1034 cm−2s−1 (1027 cm−2s−1). LHCb detectors measured some of the particles produced by the proton interactions in the absorber and by their re-interaction This test provided the first reconstructed tracks after installation. This paper is structured as follows: a brief description of the VELO and of the commissioning is given in Section 2; the synchronisation test is described in Section 3 and the VELO data taking configuration in Section 4; the calibration of the VELO timing is discussed in Section 5; the track reconstruction is presented in Section 6; Section 7 illustrates the results obtained by offline reprocessing of the data with the correct parameters for the data acquisition boards; Section 8 describes the module alignment results; the measured spatial resolution of the VELO is shown in Section 9; Section 10 summarises the main conclusions
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