The LHCb Muon System Upgrade

The LHCb Muon System Upgrade

Alessandro Cardini

on behalf of

The LHCb Muon Upgrade Group

Outline• The LHCb muon system

• The upgrade project

• The new electronics

• Performance studies

• Project organization

• Conclusions

LHCC, 03 December 2013 A. Cardini for the Muon Group 2

The LHCb Muon system

• 5 muon stations (interleaved with iron walls), 2 independent layers/station increased redundancy

• Layers are logically OR-ed increased efficiency

• 435 m2 of detector active area, 1380 chambers

• MWPC and triple-GEM in inner region of M1

• It provides:– robust muon identification– high pt muon trigger at L0



Current muon electronics

• 7536 front-end boards• 125k front-end channels• 26k readout (logical) channels

• 152 ODE (12 crates)• 152 IB (12 crates)

• 10 TELL1

• 144 SB + 12 PDM (12 crates)

The Muon upgrade in brief

• Get ready for the 40 MHz readout @ LS2

– New muon readout boards (nODE, with nSYNC ASIC) for an efficient detector readout by TELL40

– New boards for an efficient chamber pulsing (nPDM) and control (nSB) via GBT protocol

– IB removal in M5 outermost region

– Additional shielding around beam pipe behind HCAL to reduce particle rates in M2 inner regions

– Spare MWPC construction


Considerations• At the upgrade luminosities particles rates are tolerable except in M1 removed

• Particle fluxes very high in M2 inner regions additional shielding behind HCAL

• Occupancies very high in M5R4 due to backsplashes from a corrector magnet and because logical readout (~0.5 m2) channels are an OR of 24 physical channels remove IB in this region (this solution could also be implemented elsewhere if needed)

• The new electronics will be installed in existing crates without re-cabling

• Ageing of detectors is a concern after LS3, especially in innermost regions of M2 an R&D program for new more radiation tolerant detectors is ongoing (these new detectors could be built with higher readout granularity to deal with the increased occupancies)

• The proposed new electronics architecture is able to accommodate all the changes described above



New off detector board


nSYNC ASICnODE board

New control and pulsing system


nPDM board nSB board

Additional HCAL shielding

• In present detector 6.8 λI behind M2, not sufficient for upgrade luminosities, rates on M2 inner stations will be very high

• Replace PMT and bases of innermost cells of HCAL with W (or Fe) absorber

• Simulations show a 26% average rate reduction on M2R1


Spare MWPCs• Very low replacement rate

up to now

• No correlation with MWPC location on detector no evidence of damage induced by radiation

• Foreseen replacement rates similar to the ones currently observed

• Spare MWPCs will be identical to the ones currently installed


Performance studies

• Rates in the upgrade conditions were estimated from current measurements

– Rates scale very well with luminosity

– Include spill-over effect for 25 ns bunch spacing

– Conservative scaling with energy (from 7 TeV and 8 TeV data comparison)

– Effect of HCAL additional shielding included (-26% average rate reduction in most irradiated detectors of M2R1)

• Errors on rates:– Uncertainty of pp cross section (± 10%)– Increase in hit multiplicity with energy– Uncertainty of additional shielding effect


Estimated rates at 2x1033/cm2/s

Inefficiency estimate• No space charge effects seen in a high

luminosity test (1x1033/cm2/s) performed in Dec. 2012

• Efficiency decreases because of dead time due to large occupancies

• Dead time computation takes into account the in-time occupancy, the hit time profile, the analogue and digital dead time of the front-end electronics

• Method validated using special runs at 25 ns bunch spacing (it allows to disentangle dead time effect from other contributions)

• Extra O(1%) MWPC-related inefficiencies included


Muon identification efficiency• Inefficiencies impact on physics are

very analysis dependent show MuonID as the figure of merit

• MuonID– IsMuon: matching track to muon hits– Additional criteria: DLL (hit distance from

extrapolated track + RICH/CALO info)

• Use simulated Bsμμ events, with random hit removal according to estimated efficiencies

• Small efficiency losses (-5%) at 2x1033/cm2/s with respect to 2012 conditions


Pion misidentification probability• Muon misidentification (MisID) measured

directly on data using D0K-π+ sample

• Events are divided in various samples according to number of reconstructed tracks (ntrk) in each sample average number of primary vertices <nPV> is estimated

• MisID found to scale linearly with <nPV> used to for the extrapolation at the upgrade conditions

• MisID increases due to higher occupancies - can be partially recovered with additional particle identification criteria (DLL-cut)

• Further improvements expected by optimizing current MuonID algorithm to upgrade conditions and by including additional shielding


Project organization• Tasks have been allocated to

the participating institutes, matching their experience

• Project planning clearly defined

• Simplified installation of the new equipment at LS2

• Important ECS reorganization planned to occur significantly in advance of LS2 to reduce software commissioning time after hardware installation


Conclusions• High performance muon system is a key element of the particle identification

system of LHCb

• The upgraded electronics is compliant with the 40 MHz LHCb readout system

• The new control boards take advantage of the fast GBT protocol to improve system configuration and monitoring capabilities

• Muon system performance at high luminosity appears to be adequate and studies are ongoing to improve muon misidentification

• The new electronics architecture allows to better exploit the intrinsic granularity of the detector (also permits additional IB removal and possible new higher granularity detectors for most irradiated regions)


Backup slides


Costs• Costs not changed much from

FTDR, but project has evolved substantially

• Much better use of resources with the new proposed electronics

• New architecture allows other possible modifications to deal with high rates (further IB removal, new higher granularity detectors in M2/M3 inner regions)



Documents

The LHCb Muon System Upgrade