Luminosity determination in pp collisions at √s = 7 TeV usingthe ATLAS detector at the LHC

Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at √s=7 TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from these methods are monitored as a function of time and of μ, the average number of inelastic interactions per bunch crossing. Residual time- and μ-dependence between the methods is less than 2% for 0 < μ < 2.5. Absolute luminosity calibrations, performed using beam separation scans, have a common systematic uncertainty of ±11%, dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods differ by at most ±2%. The visible cross sections measured using the beam scans are compared to predictions obtained with the PYTHIA and PHOJET event generators and the ATLAS detector simulation.

[1]  I. Aracena,et al.  CHARACTERIZATION OF INTERACTION-POINT BEAM PARAMETERS USING THE pp EVENT-VERTEX DISTRIBUTION RECONSTRUCTED IN THE ATLAS DETECTOR AT THE LHC , 2010 .

[2]  Wagner,et al.  Observation of beam-beam deflections at the interaction point of the SLAC Linear Collider. , 1989, Physical review letters.

[3]  S. White.  Determination of the Absolute Luminosity at the LHC , 2010 .

[4]  S. V. D. Meer,et al.  Calibration of the Effective Beam Height in the ISR , 1968 .

[5]  Peter Skands,et al.  A brief introduction to PYTHIA 8.1 , 2007, Comput. Phys. Commun..

[6]  Werner Herr,et al.  Concept of luminosity , 2006 .

[7]  M. Ferro-Luzzi,et al.  Results of the LHC DCCT Calibration Studies , 2012 .

[8]  The Atlas Collaboration,et al.  Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC , 2010, 1012.5104.

[9]  De Jong,et al.  Improved luminosity determination in pp collisions at sqrts = 7 TeV using the ATLAS detector at the LHC , 2013, 1302.4393.

[10]  Performance of the ATLAS Inner Detector Track and Vertex Reconstruction in the High Pile-Up LHC Environment The ATLAS Collaboration , 2012 .

[11]  Venturini.  Out-of-Plane Deflections as a Diagnostic Tool and Application to PEP-II , 2001 .

[12]  A. Boccardi,et al.  LHC Luminosity calibration using the Longitudinal Density Monitor , 2013 .

[13]  V. Balagura,et al.  Notes on Van der Meer scan for absolute luminosity measurement , 2011 .

[14]  S. Klimenko,et al.  Averaging of the inelastic cross sections measured by the CDF and the E811 experiments , 2003 .

[15]  T. Hansl-Kozanecka,et al.  Commissioning of the ATLAS Muon Spectrometer with Cosmic Rays , 2010, 1006.4384.

[16]  P. Henrard,et al.  Absolute luminosity measurements with the LHCb detector at the LHC , 2011, 1110.2866.

[17]  W. Boer,et al.  Radiation damage in the diamond based beam condition monitors of the CMS experiment at the Large Hadron Collider (LHC) at CERN , 2013 .

[18]  Balagura,et al.  STUDY OF THE RELATIVE LHC BUNCH POPULATIONS FOR LUMINOSITY CALIBRATION , 2012 .

[19]  A. Goshaw.  The ATLAS Experiment at the CERN Large Hadron Collider , 2008 .

[20]  H. Burkhardt,et al.  FIRST LUMINOSITY SCANS IN THE LHC , 2010 .

[21]  F. Decker.  Beam distributions beyond RMS , 1994 .

[22]  J Wenninger,et al.  Observation of Beam-beam Deflections with LHC Orbit Data , 2013 .