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Beringer, J.

Paper Title Page
MOPEC008 Characterization of Interaction-Point Beam Parameters Using the pp Event-Vertex Distribution Reconstructed in the ATLAS Detector at the LHC 471
 
  • R. Bartoldus, I. Aracena, P. Grenier, D.W. Miller, E. Strauss, D. Su
    SLAC, Menlo Park, California
  • J. Beringer, P. Loscutoff
    LBNL, Berkeley, California
  • H. Burkhardt, S.M. White
    CERN, Geneva
  • W. Kozanecki
    CEA, Gif-sur-Yvette
  • J. Walder
    Lancaster University, Lancaster
  
 

We pre­sent re­sults from the mea­sure­ment of the 3-D lu­mi­nos­i­ty dis­tri­bu­tion with the ATLAS Inner De­tec­tor dur­ing early run­ning. The spa­tial dis­tri­bu­tion of pp in­ter­ac­tions is re­con­struct­ed by a ded­i­cat­ed al­go­rithm in the High-Lev­el Trig­ger that fits tracks and pri­ma­ry event ver­tices in real time, and by an of­fline al­go­rithm that takes full ad­van­tage of the high track­ing ef­fi­cien­cy and res­o­lu­tion. The num­ber of ver­tices pro­vides on­line mon­i­tor­ing of the in­stan­ta­neous lu­mi­nos­i­ty, while lu­mi­nous-cen­troid mo­tion mir­rors IP-or­bit and RF-phase drifts. The x, y and z lu­mi­nous widths re­flect the evo­lu­tion of the trans­verse and lon­gi­tu­di­nal emit­tances. The length scales of the IP orbit bumps, which di­rect­ly im­pact the ac­cu­ra­cy of the trans­verse con­volved beam sizes mea­sured dur­ing van der Meer scans, are cal­i­brat­ed of­fline against the mea­sured dis­place­ment of the lu­mi­nous cen­troid; this sig­nif­i­cant­ly im­proves the ac­cu­ra­cy of the ab­so­lute lu­mi­nos­i­ty cal­i­bra­tion. The si­mul­ta­ne­ous de­ter­mi­na­tion, dur­ing such scans, of the trans­verse con­volved beam sizes (from the lu­mi­nos­i­ty vari­a­tion) and of the cor­re­spond­ing lu­mi­nous sizes can be used to dis­en­tan­gle the trans­verse IP sizes of the two beams.