The LHCb Electromagnetic Calorimeter

The LHCb Electromagnetic

Calorimeter

Ivan Belyaev, ITEP/MoscowIvan Belyaev, ITEP/Moscow

5 March'2k+25 March'2k+2 Ivan Belyaev ITEP/Moscow "The LHCb Ecal"Ivan Belyaev ITEP/Moscow "The LHCb Ecal" 22

45 institutes 14 countries


LHCb Experiment

LHCbLHCb

•LHC is supposed to be LHC is supposed to be the most prolific source the most prolific source of beauty hadronsof beauty hadrons

• bb = 500 = 500 b (b (inin=80 mb)=80 mb)

•The dedicated forward The dedicated forward spectrometer at modest spectrometer at modest LL • 101012 12 b-pairs / 10b-pairs / 1077ss

•Flexible trigger efficient Flexible trigger efficient for both leptonic and for both leptonic and hadronic final stateshadronic final states

•Particle IDParticle ID

•Forward spectrometerForward spectrometer

•~10-300 mrad ~10-300 mrad acceptanceacceptance


LHCb Ecal

LHCb EcalLHCb Ecal

•Et of electrons for L0Et of electrons for L0

•B->J/B->J/KKSS, e, eX, …X, …

•Et of photons for L0Et of photons for L0•B->K*

•Reconstruction of Reconstruction of 00s s and and s offlines offline

• //00 and and e/he/h separation separation

•Overall dimensions Overall dimensions

• 6.3 m x 7.8 m 6.3 m x 7.8 m

• Transverse granularityTransverse granularity

• Varies with a function of Varies with a function of occupancy occupancy

• Radiation resistanceRadiation resistance

• Readout within 1 BX (25ns)Readout within 1 BX (25ns)

• 40 MHz electronics40 MHz electronics

• Fast optical componentsFast optical components

• ResolutionResolution

• 10% stochastic 10% stochastic

• 1.5 % constant1.5 % constant


LHCb Ecal

Total weight0.1k tons

3312 modules 3312 modules 3312 modules

3.3k modules5.5k channels


Shashlyk technology

Length: 25 X0

Weight of one module ~28 kg

66 layers:• 4 mm scintillator tile • 2 mm Pb absorber


3 types of modules

OuterOuter2.7/2.7 k2.7/2.7 k

InnerInner0.2/1.5 k0.2/1.5 k

MiddleMiddle0.4/1.8 k0.4/1.8 k


Non-uniformity of response

• For fixed cell size and volume For fixed cell size and volume ratio the constant term in ratio the constant term in energy resolution is energy resolution is determined by transverse and determined by transverse and longitudinal non-uniformity of longitudinal non-uniformity of modules modules

Transverse non-uniformityTransverse non-uniformity::

• light reflection efficiency from tile edge (global uniformity)

•position+density of fibres relative to ionising particle (local and global uniformity)

Reduced fiber densityReduced fiber density

•Improve global Improve global uniformityuniformity

•Decrease the fiber Decrease the fiber bundle diameterbundle diameter

•Reduce the overall costReduce the overall cost

•Decrease the light yieldDecrease the light yield

•Decrease local Decrease local uniformityuniformity

The tile edge matingThe tile edge mating

•Increase the light yieldIncrease the light yield

•Improve uniformityImprove uniformity


Tile edge mating

Black: l.y. 128Black: l.y. 128

Mated: l.y. 393Mated: l.y. 393Aluminized:l.y. Aluminized:l.y. 342342

Clean: l.y. 188Clean: l.y. 188

Scan over the scintillator tile with radiative sourceScan over the scintillator tile with radiative source


Fiber density optimization

Optimisation results:

•Outer module: •64 fibers

•Inner and Middle modules:•144 fiber

Test beam: 50 GeV Test beam: 50 GeV e e

Corrected for global non-Corrected for global non-uniformityuniformity


Transverse uniformity

• -beam -beam •100 GeV/c electron 100 GeV/c electron beam beam


Scintillator tiles

Chemical DMA treatment Chemical DMA treatment of scintillator tile edges of scintillator tile edges

(mating)(mating)

•The light yield spreadThe light yield spread•1.7% for tiles with 1.7% for tiles with

mated edgesmated edges

Light yield of tilesLight yield of tiles

1.5%1.5% 1.7%1.7%

matedmatedNon-Non-matedmated


Fibers

WLS fibersWLS fibers•Kuraray Y11 fibersKuraray Y11 fibers

•Multi-cladMulti-clad

•Decay time ~7ns Decay time ~7ns

•1.2 mm diameter1.2 mm diameter

•Radiation resistantRadiation resistant

•Fiber-to-fiber light yield Fiber-to-fiber light yield spread: 1.7% spread: 1.7%

•Fiber loops Fiber loops

• Loop-to-loop light yield Loop-to-loop light yield spread: 1.6%spread: 1.6%

• Loop “efficiency” > 94%Loop “efficiency” > 94%

Relative light yield of Relative light yield of fibers fibers Loop “efficiency”Loop “efficiency”

LY with loopLY w/o loop


Energy Resolution

Test beam: Test beam:

•~ 9% stochastic term ~ 9% stochastic term

•~ 1% constant term~ 1% constant term

Monte Carlo for B-> Monte Carlo for B-> ++--00

• = 5.7 MeV/c2= 5.7 MeV/c2

• BB = 35 MeV/c2 = 35 MeV/c2

MCMC


Radiation hardness

• Expected dose: Expected dose: 2.5 Mrad/ 10 year2.5 Mrad/ 10 year (innermost modules at shower max) (innermost modules at shower max)

• All components are tested up to 5MradAll components are tested up to 5Mrad

inner module:0.25 Mrad/y max

TileTile FiberFiber

DEGDEG/E (%) versus doze/E (%) versus doze


Conclusion: Modules in production

•3.3k modules to be 3.3k modules to be producedproduced•120 tested on e/120 tested on e/

beamsbeams

•Production rate Production rate •10 modules/day 10 modules/day

Light yield of modules (cosmic)Light yield of modules (cosmic)

Module-to-module spread Module-to-module spread <5%<5%

10 modules/day10 modules/day

Documents

The LHCb Electromagnetic Calorimeter