W. KozaneckiMDI meeting, 19 Mar 04 Separating the luminosity background from the non-colliding beam-gas contribution  Principle  the problem  the beam-gas cross-term background scales with I L * I H (always)  under physics conditions, L ~ I L * I H as long as the bunch pattern does not change neglecting beam-beam blow up   decorrelate L variations from beam-current variations by  modifying the constant current accidentaly (L dips) deliberately (beam-beam scans)  modifying the bunch pattern: L ~ [ I L * I h / n b ] / [  x *  y ]  See for a summary of the 16 March MD and of the available datasets W. Kozanecki

MDI meeting, 19 Mar 04 Beam-beam scans 143 x 107 mA 1600 b 2172 x 1300 mA 1415 b 610 x 395 mA 801 colldg b

W. KozaneckiMDI meeting, 19 Mar 04 Scaling: L or I L * I H ? 1320 bunches (27 Jan 04) 801 bunches (16 Mar 04) 1320 bunches (27 Jan 04) 801 bunches (16 Mar 04) I L * I H Lumi

W. KozaneckiMDI meeting, 19 Mar 04 Conclusions  After subtraction of the single-beam contributions, the DCH current measured in the 800-bunch pattern during the 16 Mar 04 MD  does not scale with the product of beam currents I L * I H  scales linearly with L. The measured sensitivity (52  A/10 33 ) equals that observed in the February 2002 background-characterization runs (53  A/10 33 ).  The L sensitivity measured in the Jan 04 background runs is 60  A/10 33   one cannot exclude that the DCH L term measured in 2004 receives a 5-10% contribution from non-colliding beam-gas.  however, the spread of fitted sensitivities is sufficiently large that it may be responsible for this apparent excess  The same method should be applicable to other background measures (SVT occupancy, diamonds/pin diodes, EMC occupancy, DIRC scaler rates)