Evolution of the response of the CMS ECAL and possible ... · and possible design options for electromagnetic calorimetry at the HL-LHC 1 ... APD • Lead Tungstate ... TB 2010 TB

Arabella Martelli IPRD13 08/10/13

Evolution of the response of the CMS ECAL and possible design options

for electromagnetic calorimetry at the HL-LHC

1

Arabella Martelli - Università e INFN Milano-Bicoccafor the CMS collaboration

13th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD13) 7 - 10 October 2013 Siena, It


The ECAL at the LHC• The homogeneous PbWO4 crystals of the Electromagnetic CALorimeter:

2


The ECAL at the LHC

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Endcap EE1.48<|η|<3.

Barrel EB|η|<1.48

Pb/Si preshower1.65<|η|<2.6

compact & high granularity for excellent energy containment: ✦Molière radius 22.mm✦ Radiation length X0 8.9.mm

✤ Energy resolution for photons from Hγγ: 1.1.% to 2.6.% (in EB) and 2.2.% to 5.% (in EE)✤ Timing resolution: 190.ps (in EB) and 280.ps (in EE)

ECAL Crystals

• Excellent energy/mass resolution• Fast response• High granularity• Very compact more than 99% of EM shower contained

Detector characteristic:

Crystal properties:

• High density (8.3 g/cm3)• Small Molière radius (2.2 cm)• Short radiation length (0.89 cm)• Fast scintillation

22 cm24.7 Xo22 cm

24.7 Xo

VPT

APD

• Lead Tungstate (PbWO4) crystals

4

mercoledì 18 settembre 13

• ENDCAP 14648 crystals in 4 Dees VPT photodetectors

• BARREL 61200 crystals in 36 super-modules APD photodetectors

ECAL Crystals



Crystal properties:


22 cm24.7 Xo22 cm

24.7 Xo

VPT

APD


4


ECAL Crystals



Crystal properties:


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APD


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23 cm25.8 X0

APD


from LHC to HL-LHC• A new machine for high-precision measurements and new discoveries:

Higgs couplings and Vector Boson scattering, VBF productions...

• ECAL is designed to operate up to 500/fb at 1034 cm-2s-1

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LHC and High Luminosity LHC (HL-LHC)

ECAL was designed to operate at L = 1 × 1034 cm−2s−1for

�L dt = 500 fb−1

Will it survive through HL-LHC era?

LS1

LS2

LS3

300-500/fbcollected

~8TeV ~13TeV

PHASE 1 PHASE 2

L2 = 2xL1L1 = 1034cm-2s-1

L3 = 5xL1

High-Lumi up to 3000/fb

expected High-PU

average 140 events per bunch crossing

L = 5


from LHC to HL-LHC• Many opportunities....

• to explore a rich physics programme• to optimize/upgrade detector performance to match the physics requirements

o faster detectors with extended pseudo-rapidity coverage

• ... and many challenges

• high radiation o radiation 6times higher than LHC designo with strong eta dependence in the EE

• very high PU o average 140 events per bunch crossing

• very high event rate

• It is fundamental for the ECAL to maintain current performance in Phase2, to fully exploit the HL-LHC potential:• acceptance, selection efficiency and purity, position and energy/momentum resolutions

4

2012 Design Phase2

cms energy [TeV]

7 14 14

L [cm-2s-1] 7x1033 1x1034 5x1034

Lint [fb-1] 30 500 3000

γ dose rate [Gy/h]

0.2(EB) 4(EE)

0.3(EB) 6.5(EE)

3(EB) 65(EE)

protons [cm-2]

1.8x1010(EB) 1.4x1012(EE)

4x1011(EB) 3x1013(EE)

2.4x1012(EB) 2x1014(EE)

detector aging

operation conditions


5

The evolution of the ECAL performance


The ECAL aging• The APDs show an expected increase in dark current, linearly growth with hadron fluence• Result is the increase of the electronic noise in EB

• Effect already visible during 2011-2012 operations

• The evolution of the APD noise is simulated for the HL-LHC conditions• measurements + extrapolations

• Evolution of noise model affected the 2012 data: • important to understand and take into account its impact

6

increased APD noise

Long term projection indicate that the noise will increase at |η|~1.45

• about a factor 2 by end Phase1 (2024) • more that a factor 5 in Phase2

see A. Benaglia’s talk


The ECAL aging• Radiation damage creates crystals defects which cause light transmission loss

• Damage from γ irradiation is spontaneously recovered at room temperature• Hadron damage is permanent and cumulative at room temperature

• The crystals’ transparency is reduced, due to the increase of µinduced

• VPT conditioning: response loss due to cumulated charge on photo-cathode• Expect 10.%-20.% signal loss over future operation

7

response loss

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How to estimate light transmission @ 420 nm

when direct measurement is not available

Damage induced by energetichadrons gives strong correlationbetween µind and fluence

Good agreement betweenmeasurements from differentgroups (black and red dots)

Ionizing damage is a function ofdose rate and was derived fromloss of transmission in ECALduring 2011-2012

12


The ECAL aging• Channel response is constantly monitored with λ = 447.nm laser light

• Channel response loss already visible with data taken during 2011-2012 operations

• The evolution of the channel transparency is simulated for the HL-LHC conditions• extrapolation model validated with data

8

FORWARD DETECTOR UPGRADE INTERIM REPORT 5

photons at high |η| throughout the operation of the HL-LHC. The impact on benchmark110

physics channels will need to be confirmed with simulation studies.111

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-1s-2, 5E+34 cm-11000 fb

-1s-2, 5E+34 cm-12000 fb

-1s-2, 5E+34 cm-13000 fb

Figure 3. Light loss curvesas a function of |η| and fordifferent integrated luminos-ity for the present PbWO4

EE detector.

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/AA

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-310

-210

-110

1 -1s-2, 5E+33 cm-1 10 fb -1s-2, 1E+34 cm-1 100 fb

-1s-2, 2E+34 cm-1 500 fb -1s-2, 5E+34 cm-11000 fb

-1s-2, 5E+34 cm-12000 fb -1s-2, 5E+34 cm-13000 fb

Figure 4. The EE con-stant term vs |η| at vari-ous levels of radiation dam-age. Other contributions toconstant term, like the en-ergy containment, are not in-cluded in this plot.

For the hadron calorimeter HE, the situation in the higher regions of |η| is similar. After112

500 fb−1 the Total Integrated Dose (TID) in HE will range from a few Gray up to tens of113

kilo-Gray, increasing by a factor of about six during the HL-LHC operation. Measurements114

with ionizing radiation have shown that at dose levels in excess of 10 kGy the degradation115

of the the plastic scintillator and WLS fibers in HE leads to a significant reduction in the116

light yield, with the regions most affected being those that are closest to the beam pipe and117

at the front face of the calorimeter. In the near-term (Phase 1) upgrade the longitudinal118

division of the readout that has been selected to minimize this effect, as has the decision119

to readout the detector with SiPMs instead of HPDs. The degradation due to neutron120

irradiation, which will be significant during Phase II, has only recently been measured and121

results are expected soon. With this, and the ionization data, a detailed degradation model122

can be made, which will be used as input to simulations.123

The forward calorimeter, HF, was constructed for the detection of forward jets. The124

choice of the fiber lengths was made so as to optimize the response linearity. However, the125

radiation damage to the fused silica core optical fibers will eventually render HF inoperable126

CMS ECAL

Simulation50 GeV e-

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9

The constraintsfor the operations in Phase2


The ECAL performance at the HL-LHC• Detector upgrades will be needed during LS3 to deal with the HL-LHC conditions

• Requirements from the aging of the detector:• Could mitigate the APD noise with further cooling• The ECAL endcaps need to be replaced

• Requirements for the on-detector electronics: 10µs latency and 1MHz readout rate• ECAL absolute maximum, with today’s hardware:

- EB/EE: 120-150 kHz on Trigger MAX - 6.4 us fixed maximum latency on the Front End (EB/EE)

• Constraints from High-Luminosity runs: HL-LHC will deliver interactions with <PU> ≈ 140 events per bunch crossing• Pile-up is most critical in the forward region• very difficult to assign object to proper vertex

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~80 reconstructed vertices(dedicated run in 2012)

performance is acceptable up to 500/fb

replace ECAL ENDCAP for Phase2

replace EB on-detector electronics


PU mitigation• ECAL is expected to play crucial role in pile-up mitigation in the upgraded CMS detector

• Calorimeter current performance will not help • Need to separate objects from different vertices

o Forward jets (VBF, η~3.5) -> determine if jets are from the primary vertex of hard interactiono Photon vertex (Hγγ, η~0) -> measure primary vertex or assign γ to selection of vertices

• Objects cleaningo Remove pile-up energy deposits from physics objects (jets, photons)

• The luminous region at the HL-LHC is expected to have a Gaussian width of σZ ~10 cm• Within tracker acceptance, charged particles are well reconstructed (Zvertex resolution ~100µm)• At high η and for neutral particles, high precision pico-second timing (20-30 ps) can be

important for pile-up mitigation

11

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Pile-up is most critical in the forward region, so upgrades should aim at optimizing the forward detector for high pile-up conditions. Two areas of study :

Increased granularity and segmentation may help to separate out pile-up activity from primary event physics objects High precision (pico second) timing may help in pile-up mitigation. The subdetector providing the precision timing may best be associated to precise and finely segmented detector ECAL.

Object reconstruction Object-to-vertex attribution H

Studies on precision timing are ongoing for pile-up mitigation through time-of-flight. Desired resolution is 20-30 ps.

Pile-up Mitigation

Calorimeter

primary vertex

secondary vertex

XX

t t’~20 ps resolution

needed


12

The possiblecalorimeter design options


Design options for the endcap calorimeters 1____• Scenario 1

• replace the Endcap calorimeters in LS3• Hadron calorimeter endcaps (HE) may need to replace the active materials only

• New ECAL Endcap designed as a standalone calorimeter

• Choice on material and configuration to reduce the radiation damage

• Sampling configuration (i.e. Shashlik)• rad-hard inorganic scintillator (LYSO or CeF3)• compact with Pb or W as absorber

• Embedded wavelength shifter concept:

• Other possibility is with photon sensors on the sides

• R&D: rad-hard fibers, photo-detectors, mechanical mounting, calibration&monitoring13

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Sampling

• short optical path in scintillator and WLS

• quartz handles the light transport (it is rad-hard)

• capillary goal: D ≈ 1.2 mm d ≈ 0.4 mm



• Both ECAL and HCAL Endcap calorimeters replaced in LS3• Possibility of a common integrated redesign of the endcap calorimeters

• Combined readout technology to provide event-by-event calibration

• Cherenkov/Scintillator Sampling Calorimeter• simultaneous measurement of cherenkov and scintillation light, to remove the intrinsic

fluctuations in the hadronic and e.m. component of the hadronic showers (offline compensation)

• Possible configuration:• solid absorber (W) block • fibers inserted in a square grid array• Packing Fractions:

12 % quartz fibers 12 % scintillating fibers

• Order 5 % energy resolution for 50 GeV jets• Timing info. (different feature for π and e initiated showers) could help in particle ID

• R&D: rad-hard scintillating/quartz fibers, photo-detectors, calibration&monitoring

14

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• Both ECAL and HCAL Endcap calorimeters replaced in LS3• Possibility of a common integrated redesign of the endcap calorimeters

• Integrated design with the forward pixel disks and the muon system for optimal performance

• Imaging Gas Sampling Calorimeter: • Separating showers through a finely granulated and longitudinally segmented calorimeter• Highly segmented layers of active media readout independently

• Not completely new ideas (CALICE)• showers are tracked as they develop • are associated with tracks in the upstream tracker • and downstream in the muon detectors

• HL-LHC, high rates in the endcaps drive the active detector choice• at |η| = 3, expected 50MHz/cm2 single particle rate at shower maximum

• R&D: number of channels, compact and inexpensive electronics, trigger, cooling, performance in high pile-up, linearity, calibration&monitoring

15

Imaging calo

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Summary and Outlook

• LHC is at the beginning of its operation: ~30 fb-1 of integrated lumi. delivered up to now• Evidence of small radiation damage is already visible in the ECAL performance

• observation is in general agreement with expectations

• In 10years from now, the HL-LHC will operate at 5x Inst. Luminosities wrt LHC in 2012, delivering up to 3000 fb-1 in Phase2• stringent detector requirements in terms of performance and rad-hardness

• Simulations have been developed to predict the evolution of the ECAL response in the high-radiation environment and understand the upgrade needs

• New calorimeter options are being studied• Target is to fully profit from the potential offered by the HL-LHC• Key points are radiation-hardness, granularity and segmentation• Timing resolution may add important information for pile-up mitigation and object ID

• Major R&D already launched

16


17

BACKUP


18Figure 26: Charged particle fluence in the central region of the CMS detector after 100 fb!1 luminosity.

Figure 27: Muon fluence in the central region of the CMS detector after 100 fb!1 luminosity.

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Documents

Evolution of the response of the CMS ECAL and possible ... · and possible design options for electromagnetic calorimetry at the HL-LHC 1 ... APD • Lead Tungstate ... TB 2010 TB