Machine Background

The Machine Induced Background can be defined as the flux of secondary particles induced by proton losses upstream and downstream of the LHCb interaction region and as such derives from the interaction of beam protons with residual gas or machine elements.

An overview of the issue related to this background and its impact on the LHC experiments has been given at the "LHC Project Workshop Chamonix XV" in January 2006 (transparencies, proceedings).

Various presentation on the issue regarding LHCb have been given in LHCb meetings (including beam gas in the VeLo), a non exhaustive collection of presentation and notes will be available soon.

The most recent presentations have been in a dedicated sub-session of the LHCb Week Plenary Meeting on June 1st, 2006.

An LHC wide working group exist to exchange information between the experiments and various accelerator groups and better understand the problem. From the Machine Induced Background (MIB) Working group web site the minutes of the meetings as well as the presentation given are available.

Background Estimates regarding the beam gas contribution in the Long Straight Section (LSS) , Dispertion Suppression (DS) and ARC in sector 7-8 and 8-1 are relatively old (2001) and are expected to be re-evaluated with the current estimate of residual beam gas in the different operation scenario and with the introduction of the shields in the tunnels. The most recent talk on the status of the studies is the following:

• "Status of machine-induced background studies", G.Corti, 17 January 2005, Tuesday meeting

The most recent residual gas estimates from A.Rossi are available as an excel spread-sheet.

Recent estimates of background particles from the tertiary collimators introduced between D1 and D2 in the experimental insertions and due to IR7 cleaning inefficiency have been provided by V.Talanov. Relevant presentations related to the collimators background at the MIB meetings are:

• "Proposal for Estimating the Cleaning Inefficiency Background in IR8", V.Talanov, 24 June 2005
• "Beam losses on the collimators in the IR8" , G. Robert-Delamaize, 14 October 2005
• "Tertiary background at the IP8 - a first look", V.Talanov, 14 October 2005
• "Tertiary background and background shielding inthe IR8", V.Talanov, 16 December 2005

Source files are available to study this background in different conditions and its impact on the LHCb detectors. A descriptions of the files is provided here. An implementation in Gauss of a generator making use of these source is available since v25r10. For details refer to the release notes of the packages Gen/LbMIB and MIBData, as well as the following presentations

• "The collimator background generator", M.Lieng, 11 December 2006
• "Machine induced background generator", M.Lieng, 8 March 2007
• "Background analysis for the BCMs Project for LHCb", M.Lieng, 15 June 2007