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Beam /Background observations in LHCb

Beam /Background observations in LHCb. LBS Meeting, 16April. Beam losses vs luminosity ramp @IP8. Losses measured with the BLS scintillator system and diamond-based BCM BKGD1 is given by short running sums from BCM (80us, on which we dump )/

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Beam /Background observations in LHCb

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  1. Beam/Background observations in LHCb LBS Meeting, 16April

  2. Beamlosses vs luminosityramp @IP8 • Lossesmeasured with the BLS scintillatorsystem and diamond-based BCM • BKGD1 isgiven by short runningsums from BCM (80us, on whichwedump)/ • BKGD2 isgiven by 25ns runningsums from BLS (running sum of 12x25ns bxids, more like an «operational background number») • BKGD3 lsgiven by long runningsums from BCM (1280 us) • BLS systemisbased on plasticscintillatorslocated 1.5m away from the IP on the wall in front of VELO BLS2 BLS1 Center of the ring   Outside of the ring

  3. Beamlosses vs luminosityramp @IP8 • Intensity of losses (proportional to #of MIPs) changesaccording to the step in the luminosityramp • Itisdependent on the separation of beams • Dependent on geometrical position of beams (and tilt) • Fill 2516 LumiInst

  4. Beamlosses vs luminosityramp @IP8 • Anotherexample • Fill 2514 LumiInst

  5. Beamlosses vs luminosityramp @IP8 • Anotherexample • Fill 2513 LumiInst

  6. Beamlosses with SMOG on • SMOG ON with BLS • Followsthe bellshape of heating of TDI? • Fill 2508 LumiInst

  7. Beamlosses with SMOG on • SMOG ON asseen with the BeamConditionsMonitors • Samebellshape • Fill 2508 LumiInst

  8. Beam gas ratesduring lumi ramp • Beamgas are detector rate gated with bunchcrossingtype • beam1gas istriggered on beam1-empty, beam2gas istriggered on empty-beam2 • slightdependance on luminosity • beamgasratesincrease/decreasewhileincreasing/decreasingluminosity • Fill 2516 LHCb beam1 gas LHCb beam2 gas

  9. Beam gas rates, last year • Hints of TDI heating on beam2gas, but beam1gas isexpected: • exponentialdecay from intensity of beams due to luminosity! • No evidence of lumi leveling in last yearbeamgasrates! • Fill2216 LumiInst LHCb beam2 gas LHCb beam1 gas

  10. Movement in Z duringluminosityramp • From VELO detector • Live monitoring of luminosityramp: to be analysedbetter offline, just observationhere • Z moves to about +25mm, thenstableuntil end of fill Z [mm] • Fill 2516 • From VELO detector • During lumi rampwealsosee high occupancyevents • Manytrack and parallel to z • Thiswill be studied more in detail by analizing the beamangles and will be confirmedwhenwewillhave the LHCb magnetpolaritychange (as the angleswillflip) Time sincebeginning of run

  11. Conclusions No bad background conditionsseenduring first StableBeamsfills in 2012  no hint of vacuumactivityin LHCb  only case (maybe?) seen with SMOG, butthatitisexpected. Somethingisgoing on duringourluminosityramp: movement of beamsis in both X and Y plane  VELO z position moves(to be confirmedoffline with more analysed data, work ongoing)  Differentintensitylossesatdifferent lumi step in differentdirections  geometricaleffects (extremelydifficult to disentangle in 3D…)  Slight dependance of beamgasrates from luminosity  notseen last year with similarconditions («goodmagnetpolarity», +) Q: are wesureabout the 8sigma separationat 3.75m? Eitherwe are notmovingorthogonally to the crossing angle plane or the beamshavedifferentangles @ IP8.

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