SPD and LHCb upgrade

Hugo Ruizet al from

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Outline

• Physics motivation• Ageing of:– Detector, fibers– PMTs

• Replacements to be done– VFEs?– FEBs– Fibers

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Before upgrade: motivation now

• Trigger:– Separate e – @ L0

• Thresholds 2.3 GeV and 3 GeV in the last optimization at http://indico.cern.ch/getFile.py/access?contribId=1&sessionId=2&resId=0&materialId=slides&confId=42082

– GECs, but decided to drop them two weeks ago– Under study: trigger for two-photon for lumi: 2 muons

+ low SPD multi• Offline:– Some improvement in resolution of 0 mass for

converted s (but not so if Pb not there?)• Instantaneous lumi and beam backgrounds

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The upgrade

• Lumi 1033

• All detectors read-out at 40 MHz, no L0• Still, trigger needs to use:– Seeds à la L0 (calo, muons)– Reconstruction based in regions of interestSee Hans’ presentation at http://indico.cern.ch/conferenceDisplay.py?confId=43555

• Bs one of the star channels

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The SPD in the upgrade• The SPD does not harm– It’s just a first sensitive layer in the calo– But electronics, fibers (etc?) to be replaced $

• Use: classify trigger seeds as photons or electrons– 1st layer of trigger

• 2 hadron + photon ?• 1 hadron + 1 photon? (maybe not, as also want 1 hadron + 1

electron?)– confirmation: use SPD to reject bulk of events

before looking for tracks in T stations pointing to ECAL cluster

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But: e+e-

• Current material budget:– 0.4 X0 magnet-Calo (Reoptimization TDR, pag 3)

– Underestimation: only M1 is 0.265 instead of the 0.22 in the simulation

• Probability of photon survival: 70%• Current -confirmation at HLT1 uses only

candidates– Mariusz: no inefficiency because most of ECAL clusters

duplicated as e and , differing in a single cell ??

45.09

7e

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Physics motivation• Other sources of inefficiency on photons:– Random coincidence, conversion in the SPD:

• Multiplicity 33 @ 21032, would be 160 @ 1033

• Roughly 160/6000 2.6% (maximum 8% in hottest cell)• Ways out of e+e-:– Still worth for the remaining 70%?– (non-binary output…)– Remove M1: ask for production of MC without M1

• Minimum bias (rate)• Bs (efficiency)

• Who will do the study?

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Ageing of detector & fibers

• Common with PS• Edu is just starting to have a look at some old

LHCb notes on HCAL scintillators and fibers– Ageing as a function of dose need interaction

with Gloria

• And tried to contact Evgeni• Inputs?

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Edu

Lumi 5·1032

PMTs ageing• Intensity with current settings:

• At 1033:– max 1-2 A– 25 < 0.4 A– rest < 0.2 A

Lumi 2·1032 200 nA

Míriam

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1 A

PMT ageing• LHCb-Calo 2003-044, http://indico.cern.ch/conferenceDisplay.py?confId=a031004

101 year of LHC

0.3 A

?

PMT ageing

• Beware: for higher currents– Plot is for an old 12 stages, but

same behavior checked on a 8-stage PMT

• Current at upgrade lie between safe and dangerous region…– But can change positions of a

few PMTs every year• Conclusion?– Need a test-bench?

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ZOOM THE VERY FIRST PARTOF THE DISTRIBUTION

10 A

Compensation of gain loss with HV

• Current HV settings:• Room for increasing to

800V

• Gain increase possible– At least factor 5

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V

VFEs and gain reduction: noise

• Noise level is 2 fC rms approx

• Current charge/MIP

• If we allow down to 5 : maximum factor 3 reduction

• Tails are low some margin for larger factors…

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VFEs and gain reduction: threshold

• Resolution with current gain– Common Vref

– Able to set up to 1 MIP in all channels

• Effect of gain reduction of a factor 3– 250 instead of 300mV required

for Vref

– Resolution typically 12%, up to 25% of MIP

• Again: margin for higher reductions

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Minimum resolution with current gain (one Vref)

Minimum resolution with gain/3 (one Vref)

Replacements: FE, fibers

• The FE will need to send data at 40 MHz to be replaced

• New fibers needed to accommodate the extra band-with to send data to the barracks

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Conclusions

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Back-up

• Efficiency of Bs vs rate (and # of tracks to be reconstructed) a good benchmark to evaluate the need for the SPD at the upgrade

• Not excluded that SPD could work in the upgrade without major replacement of PMTs– New PMT aging test bench?

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Occupancieslumi2 lumi2 lumi2

lumi5 lumi5 lumi5

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Intensity @ lumi5 / lumi2

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