Detector Requirements andSoftware for CLIC

André SailerOn behalf of the CLICdp Collaboration

CERN-EP-LCD

Software and Physics Requirements for e+e− CollidersJanuary 16, 2020

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 1 / 29

Table of Contents

IntroductionCLIC AcceleratorBeam-Beam EffectsBeam-induced Backgrounds

Detector, Software, Requirements, and PerformanceReconstruction SoftwareThe Full DetectorTrackerVertex DetectorCalorimeters and Particle Flow Clustering

Electromagnetic Calorimeter

Hadronic CalorimeterForward Calorimetersγγ→ hadron Background Mitigation

Summary

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 2 / 29

CLICdp Collaboration

CLIC detector and physics (CLICdp): 30institutes from 18 countries

CLICdp focuses on CLIC-specific studies ofI Physics prospects and simulation studiesI Detector optimisation and hardware R&D

for CLICI Together with CALICE and FCal

collaborations

CLIC collaboration developing the acceleratortechnology

50 µm thick silicon wafer CLICpix2 + C3PD glue assembly LumiCal Sensor Calorimeter Test Beam Scintillator Tile

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 3 / 29

CLIC Accelerator

The Compact Linear Collider (CLIC) is amulti-TeV electron–positron colliderI Two-beam acceleration with

room-temperature copper, gradient up to100 MV/m

I Main beam comes in 156 ns (176 ns at380 GeV) trains with 50 Hz

I StagingI First stage around 380 GeV for Higgs

and top physics, top-threshold scanI Second stage at 1.5 TeV possible with

single CLIC drive beamI 3 TeV stage with one drive beam complex

for each beam

156 ns 20 ms

0.5 ns

CLIC: trains at 50 Hz, 1 train = 312 bunches

TA

BC2

delay loop2.5 km

decelerator, 4 sectors of 878 m

446 klystrons20 MW, 48 µs

CR2

CR1

circumferencesdelay loop 73 mCR1 293 mCR2 439 m

BDS1.9 km

IPTA

BC2 BDS1.9 km

11 kmCR combiner ringTA turnaroundDR damping ringPDR predamping ringBC bunch compressorBDS beam delivery systemIP interaction point dump

BC1

drive beam accelerator2.0 GeV, 1.0 GHz

time delay line

e+ injector2.86 GeV

e+ PDR

389 m

e+ DR

427 m

booster linac 2.86 to 9 GeV

e+ main linac

e– injector2.86 GeV

e– DR

427 m

e– main linac, 12 GHz, 72 MV/m, 3.5 km (c)FT

Main Beam

Drive Beam

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 4 / 29

CLIC Accelerator

The Compact Linear Collider (CLIC) is amulti-TeV electron–positron colliderI Two-beam acceleration with

room-temperature copper, gradient up to100 MV/m

I Main beam comes in 156 ns (176 ns at380 GeV) trains with 50 Hz

I StagingI First stage around 380 GeV for Higgs and

top physics, top-threshold scanI Second stage at 1.5 TeV possible with

single CLIC drive beamI 3 TeV stage with one drive beam

complex for each beam

156 ns 20 ms

0.5 ns

CLIC: trains at 50 Hz, 1 train = 312 bunches(c)FT

TA

BC2

delay loop2.5 km

decelerator, 25 sectors of 878 m

540 klystrons20 MW, 148 µs

CR2

CR1

circumferencesdelay loop 73 mCR1 293 mCR2 439 m

BDS2.75 km

IPTA

BC2

delay loop2.5 km

540 klystrons20 MW, 148 µs

drive beam accelerator2.4 GeV, 1.0 GHz

CR2

CR1

BDS2.75 km

50 kmCR combiner ringTA turnaroundDR damping ringPDR predamping ringBC bunch compressorBDS beam delivery systemIP interaction point dump

drive beam accelerator2.4 GeV, 1.0 GHz

Drive Beam

Main Beambooster linac2.86 to 9 GeV

e+ main linace– main linac, 12 GHz, 72/100 MV/m, 21 km

e+ injector2.86 GeV

e+ PDR

389 m

e+ DR

427 me– injector

2.86 GeV

e– DR

427 m

BC1

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 4 / 29

Higgs Processes

I Higgsstrahlung dominates at smaller centre-of-massenergy: ∝ 1/s

I chose working point at√

s = 380 GeVI Trade-off between cross-section, luminosity, and jet

topology, more-boosted jets simplify separationI Can also do top physics at this energy

I WW-fusion dominates at larger energies: ∝ log(s)I Rarer decays more available at higher energyI Triple Higgs coupling in HHνeνe benefits from

highest energyI All studies summarised in a comprehensive paper [1]

[GeV]s0 1000 2000 3000

HX

) [fb

]→ - e+

(eσ

2−10

1−10

1

10

210

eνeνH

-e+He

ZH

ZHH

Htt

eνeνHH

Z

e−

e+

H

Z

W

W

e−

e+

νe

H

νe

W

W

H

e−

e+

νe

H

H

νe

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 5 / 29

Top Quark Studies

I 350 GeV and 380 GeVI Threshold scan around 350 GeVI Top-quark mass from radiative eventsI Flavour-changing neutral current top-quark decaysI Direct reconstruction of the top quark

I 1.4 TeV and 3 TeVI Vector boson fusion production of top pairsI Top Yukawa coupling

I Kinematic studies of top-pair production at all stagesI Summarised in comprehensive paper [2]

[GeV]s0 1000 2000 3000

(+X

)) [f

b]t t

→ - e+(eσ

1−10

1

10

210

310

tt

eνeνtt Htt

Ztt

Z∗/ γ∗

e−

e+

t

t

Z∗/ γ∗

e−

e+

t

H

t

W−∗W+∗

e−

e+

νe

t

t

νe

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 6 / 29

Luminosity and Beam-Beam Effects

I Large luminosities require high bunchcharge N and small beams σx/y/z (giventhe other constraints from the accelerator)

L ∝ N2

σx σy

I Leads to large electromagnetic fieldsduring bunch crossing B ∝ γN

σz (σx+σy )

I Use flat beams σy � σx

Par. Unit 380 GeV 3 TeV

N 5.2 ·109 3.72 ·109

σx nm ≈ 149 ≈ 45σy nm ≈ 2.9 ≈ 1σz µm 70 44L 1/cm2s1 1.5 ·1034 5.9 ·1034

L0.01 1/cm2s1 0.9 ·1034 2.0 ·1034

I The bunch particles are strongly deflectedby the fields and radiate Beamstrahlung

0 0.2 0.4 0.6 0.8 1s/s'=sx

1−10

1

10

210

sdxdN

N1

380 GeV

3 TeV

√s′/√

s 380 GeV 3 TeV

> 0.99 58% 36%> 0.90 87% 57%> 0.50 99.96% 88.6%

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 7 / 29

Beam-induced Backgrounds

I Beamstrahlung photonscollide with beam particles or other photons

I Incoherent e+e− pairsI qq pairs in γγ→ Hadron events

I Backgrounds strongly depend oncentre-of-mass energy

I Incoherent pairs have largestconcentration at small angles, and smalltransverse momentum

I Detector acceptance starts at 10 mrad,limited by coherent pairs

[rad]θ4−10 3−10 2−10 1−10 1

per

BX

θ d

N/d

4−10

2−10

1

210

410

610

810­

e+

Incoherent e

hadrons→ γγ

CLICdp

380 GeV

>0 MeVT

p

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 8 / 29

Beam-induced Backgrounds

I Beamstrahlung photonscollide with beam particles or other photons

I Incoherent e+e− pairsI qq pairs in γγ→ Hadron events

I Backgrounds strongly depend oncentre-of-mass energy

I Incoherent pairs have largestconcentration at small angles, and smalltransverse momentum

I Detector acceptance starts at 10 mrad,limited by coherent pairs

[rad]θ

4−10 3−10 2−10 1−10 1

per

BX

θdN

/d

4−10

2−10

1

210

410

610

810­

e+

Incoherent e

hadrons→ γγ

CLICdp

3 TeV

>0 MeVT

p

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 8 / 29

Beam-induced Backgrounds

I Beamstrahlung photonscollide with beam particles or other photons

I Incoherent e+e− pairsI qq pairs in γγ→ Hadron events

I Backgrounds strongly depend oncentre-of-mass energy

I Incoherent pairs have largestconcentration at small angles, and smalltransverse momentum

I Detector acceptance starts at 10 mrad,limited by coherent pairs

4−10 3−10 2−10 1−10 1 [rad]θ

4−10

2−10

1

210

410

610

810

per

BX

θdN

/d

­e

+Incoherent e

hadrons→ γγ

CLICdp

3 TeV

>20MeVT

p

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 8 / 29

CLIC use of the Linear Collider Software

I Detector Model described with DD4HEP

I Event data model and persistency: LCIOI Reconstruction currently using iLCSoft

with the Marlin framework1. γγ→ hadron background overlay2. Digitisation applying sensor

resolutions(tracker), calibration factors(calorimeter)

3. ConformalTracking pattern recognitionand iLCSoft::KalmanFilter

4. Particle flow reconstruction:PANDORAPFA

5. Vertexing and Flavour Tagging: LCFIPlus6. Jet clustering with FastJet and

FastJetContrib7. Very Forward Calorimeter Reconstruction

with FCalClusterer

Generator

Detector Geometry: lcgeo (DD4hep)

AnalysisRecon-struction

Simulation

C++, Python OverlayDigitizationTracking

PFA

VertexingJet ClusteringFlavor Tagging

Persistency FrameworkEvent Data Model: LCIO

Whizard,Pythia, ...

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 9 / 29

Detector for CLIC

General purpose detector for Particle Flow reconstruction [3]

I Steel–Scintillator HCalwith 3 cm cell-size

I Silicon–Tungsten ECalwith 5 mm cell-size

I Silicon Tracker, mostly50 µm pitch strips

I Vertex Detector with25 µm pixels

6 m

I SuperconductingSolenoid of 4 T

I Iron Yoke with RPCs forMuon ID

I End-coilsI Forward calorimeters

for EM coverage downto 10 mrad

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 10 / 29

Track Reconstruction

I Full silicon tracking due to timing andoccupancy

I Momentum resolution of 2×10−5/GeV forcentral high momentum tracksI Needed for, e.g., slepton

measurements [4], Higgs to muons [1]0 0.5 1 1.5 2

0

0.5

1

1.5

z[m]

x[m]

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 11 / 29

Track Reconstruction

I Full silicon tracking due to timing andoccupancy

I Momentum resolution of 2×10−5/GeV forcentral high momentum tracksI Needed for, e.g., slepton

measurements [4], Higgs to muons [1]

[GeV]µp0 500 1000 1500 2000

dN/d

p

0

20

40

60no smearing

-510×=42T

/pT

pσ-510×=82

T/p

Tpσ

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 11 / 29

Track Reconstruction

I Full silicon tracking due to timing andoccupancy

I Momentum resolution of 2×10−5/GeV forcentral high momentum tracksI Needed for, e.g., slepton

measurements [4], Higgs to muons [1]

) [GeV]µµm(110 120 130 140

Eve

nts

/ 0.5

GeV

0

20

40

60

80 simulated databackground fitsignal + background fit

-µ+µ →; HννH = 3 TeVsCLICdp

) = -80%-

P(e

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 11 / 29

Pattern Recognition: Conformal Tracking

I Global pattern recognition for all silicontracking layers

I Conformal mapping to turn circle fittinginto straight line fittingI u = x

x2+y2 v = yx2+y2

I At least for prompt tracks

I Publication:https://doi.org/10.1016/j.nima.2019.163304[5]

x [mm]1500− 1000− 500− 0 500 1000 1500

y [

mm

]

1500−

1000−

500−

0

500

1000

1500CLICdp

­µSingle

prompt, p = 100 GeV

prompt, p = 400 MeV

non­prompt, p = 100 GeV

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 12 / 29

Pattern Recognition: Conformal Tracking

I Global pattern recognition for all silicontracking layers

I Conformal mapping to turn circle fitting intostraight line fittingI u = x

x2+y2 v = yx2+y2

I At least for prompt tracks

I Publication:https://doi.org/10.1016/j.nima.2019.163304[5]

u [1/mm]0.04− 0.02− 0 0.02 0.04

v [

1/m

m]

0.04−

0.02−

0

0.02

0.04

CLICdp

­µSingle

prompt, p = 100 GeV

prompt, p = 400 MeV

non­prompt, p = 100 GeV

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 12 / 29

Tracking Efficiency

I Single Muon efficiency >99.8% above200 MeV and θ ≥ 10◦

I High efficiency for displaced tracks, untilthey no longer leave enough hitsI Can be improved with adapted

reconstruction parameters

I Good efficiency for particles in jets, alsowhen including γγ→ hadron backgrounds

[GeV]T

p

1−10 1 10 210

Tra

ckin

g e

ffic

ien

cy

0.96

0.97

0.98

0.99

1

1.01CLICdp

­µSingle

(forward)° = 10θ

(transition)° = 30θ

(barrel)° = 89θ

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 13 / 29

Tracking Efficiency

I Single Muon efficiency >99.8% above200 MeV and θ ≥ 10◦

I High efficiency for displaced tracks,until they no longer leave enough hitsI Can be improved with adapted

reconstruction parameters

I Good efficiency for particles in jets, alsowhen including γγ→ hadron backgrounds

vertex R [mm]

0 100 200 300 400 500

Tra

ckin

g e

ffic

ien

cy

0

0.2

0.4

0.6

0.8

1

1.2 ­µDisplaced single

° < 100φ, θ< °0 < y < 600 mm, 80

p = 1 GeV

p = 10 GeV

p = 100 GeV

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 13 / 29

Tracking Efficiency

I Single Muon efficiency >99.8% above200 MeV and θ ≥ 10◦

I High efficiency for displaced tracks, untilthey no longer leave enough hitsI Can be improved with adapted

reconstruction parameters

I Good efficiency for particles in jets,also when including γγ→ hadronbackgrounds

[GeV]T

p

1−10 1 10 210

Tra

ckin

g e

ffic

ien

cy

0.7

0.8

0.9

1

> 0.02 radMC

∆, vertex R < 50 mm, ° < 170θ < °10

= 3 TeVCM

, Ett

No background

hadrons background→γγ3 TeV

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 13 / 29

Momentum Resolution

I Reaching required momentum resolutionfor central high pT tracks [6]

I Small dependency on single pointresolution in the vertex detectorI More important for impact parameter, see

next slide

p [GeV]1 10 210

]­1

) [G

eV

T,tru

e

2/p

Tp

∆(σ

5−10

4−10

3−10

2−10

1−10­µSingle

= 10 degθ

= 30 degθ

= 89 degθ

mµ = 10 deg, VTX single point res 5θ

mµ = 30 deg, VTX single point res 5θ

mµ = 89 deg, VTX single point res 5θ

mµ = 10 deg, VTX single point res 7θ

mµ = 30 deg, VTX single point res 7θ

mµ = 89 deg, VTX single point res 7θ

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 14 / 29

Vertex Detector

I Silicon vertex detector: precise vertexreconstruction

I Double layers (0.2%X0 per detection layer)I Rin = 31 mmI Spiral geometry in endcaps for air cooling

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 15 / 29

VXD: Single Point Resolution

Transverse and longitudinal impact parameter resolutions for different single point resolutions ofthe vertex detector [6]

]° [θ20 40 60 80

m]

µ)

[0

d∆(

σ

1

10

210

310

CLICdp

­µSingle m (default)µ = 3

VTXσp = 1 GeV,

m (default)µ = 3VTX

σp = 10 GeV, m (default)µ = 3

VTXσp = 100 GeV,

mµ = 5VTX

σp = 1 GeV, mµ = 5

VTXσp = 10 GeV,

mµ = 5VTX

σp = 100 GeV, mµ = 7

VTXσp = 1 GeV,

mµ = 7VTX

σp = 10 GeV, mµ = 7

VTXσp = 100 GeV,

]° [θ20 40 60 80

m]

µ)

[0z

∆(σ

1

10

210

310

410

510CLICdp

­µSingle m (default)µ = 3

VTXσp = 1 GeV,

m (default)µ = 3VTX

σp = 10 GeV, m (default)µ = 3

VTXσp = 100 GeV,

mµ = 5VTX

σp = 1 GeV, mµ = 5

VTXσp = 10 GeV,

mµ = 5VTX

σp = 100 GeV, mµ = 7

VTXσp = 1 GeV,

mµ = 7VTX

σp = 10 GeV, mµ = 7

VTXσp = 100 GeV,

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 16 / 29

Calorimeters and Particle Flow Clustering

I Require excellent jet energy resolution,separation of jets from W’s or Z’s [4]

I Particle flow clustering, separate clustersfrom neutral and charged particles

I Fine grained calorimeters

Mass [GeV]60 70 80 90 100 110 120

Arb

itrar

y U

nits

0

2

4

6

/m = 1%mσ/m = 2.5%mσ/m = 5%mσ/m = 10%mσ

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 17 / 29

Electromagnetic Calorimeter

I Depth and sampling fraction (40 layers,22 X0) for high energy EM objectreconstruction [3]I Further optimisation of layer structure

possible, Silicon ECal is a cost driver

I High granularity (5×5 mm2) for good jetenergy resolution [3]I studied with ILD detector model

[GeV]γtrueE

0 500 1000 1500

)/E

[%]

HC

al+

EE

Cal

(Eσ

0

1

2

3

4

5

6

CLICdet_17_8

CLICdet_20_10

CLICdet_30

CLICdet_40_b

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 18 / 29

Electromagnetic Calorimeter

I Depth and sampling fraction (40 layers, 22X0) for high energy EM objectreconstruction [3]I Further optimisation of layer structure

possible, Silicon ECal is a cost driver

I High granularity (5×5 mm2) for good jetenergy resolution [3]I studied with ILD detector model

ECAL Cell Size [mm]0 5 10 15 20 25

) [%

]j

(E90

) / M

ean

j(E

90R

MS

0

1

2

3

4

5

45 GeV Jets

100 GeV Jets

180 GeV Jets

250 GeV Jets

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 18 / 29

Electromagnetic Calorimeter

I Depth and sampling fraction (40 layers, 22X0) for high energy EM objectreconstruction [3]I Further optimisation of layer structure

possible, Silicon ECal is a cost driver

I High granularity (5×5 mm2) for good jetenergy resolution [3]I studied with ILD detector model

nLayers15 20 25 30

) [%

]j

(E90

) / M

ean

j(E

90R

MS

0

1

2

3

4

5

45 GeV Jets

100 GeV Jets

180 GeV Jets

250 GeV Jets

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 18 / 29

Hadronic Calorimeter

I Jet energy resolution with differentHCal depths [4]

I Need 7.5λI to contain highest energy jets

's in CLIC HCALIλNumber of 4 6 8 10

/E [%

]Eσ

3

4

5

6 uds, jet energy:→Z45.5 GeV100 GeV250 GeV500 GeV1 TeV1.5 TeV

0.7≤ θcos

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 19 / 29

Jet Energy Resolution

I Reaching 3.5% jet energy resolution forhigh energy jets in the barrel [6]

I Endcap region more affected byγγ→ hadron backgrounds, which areforward peaked

|θ|cos0 0.2 0.4 0.6 0.8 1

)[%

]G j

/ER j

(E90

)/M

ean

G j/E

R j(E

90

RM

S

2

4

6

8

10

12

14 VLC7 Jets 50 GeV≈

100 GeV≈

250 GeV≈

750 GeV≈

1500 GeV≈

CLICdp

3.5%

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 20 / 29

Jet Energy Resolution

I Reaching 3.5% jet energy resolution forhigh energy jets in the barrel [6]

I Endcap region more affected byγγ→ hadron backgrounds, which areforward peaked

|θ|cos0 0.2 0.4 0.6 0.8 1

)[%

]G j

/ER j

(E90

)/M

ean

G j/E

R j(E

90

RM

S

2

4

6

8

10

12

14 VLC7 Jets, with 3TeV BG 50 GeV≈

100 GeV≈

250 GeV≈

750 GeV≈

1500 GeV≈

CLICdp

3.5%

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 20 / 29

W/Z-Separation

I Jet energy resolution good enough for≈ 2σ separation between jets from W andZ bosons [6]

I For different boson energies and includingbackgrounds

Background EW,Z σm(W)/m(W) σm(Z)/m(Z) ε Separation

[GeV] [%] [%] [%] [σ ]

no BG

125 5.5 5.3 88 2.3250 5.3 5.4 88 2.3500 5.1 4.9 90 2.51000 6.6 6.2 84 2.0

3 TeV BG

125 7.8 7.1 80 1.7250 6.9 6.8 82 1.8500 6.2 6.1 85 2.01000 7.9 7.2 80 1.7

380 GeV BG 125 6.0 5.5 87 2.2 di­jet mass [GeV]60 80 100 120

A.U

.

0

200

400

600

800500 GeV bosons

W bosonsZ bosons

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 21 / 29

W/Z-Separation

I Jet energy resolution good enough for≈ 2σ separation between jets from W andZ bosons [6]

I For different boson energies and includingbackgrounds

Background EW,Z σm(W)/m(W) σm(Z)/m(Z) ε Separation

[GeV] [%] [%] [%] [σ ]

no BG

125 5.5 5.3 88 2.3250 5.3 5.4 88 2.3500 5.1 4.9 90 2.51000 6.6 6.2 84 2.0

3 TeV BG

125 7.8 7.1 80 1.7250 6.9 6.8 82 1.8500 6.2 6.1 85 2.01000 7.9 7.2 80 1.7

380 GeV BG 125 6.0 5.5 87 2.2 di­jet mass [GeV]60 80 100 120

A.U

.

0

200

400

600500 GeV bosons, with 3 TeV BG

W bosonsZ bosons

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 21 / 29

Forward Calorimeters

I Integrated Luminosity measurements withLumiCal: require excellent polar angleresolution 20 µrad

I BeamCal complementing EM acceptancedown to 10 mrad

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 22 / 29

LumiCal Performance

I LumiCal reaching desired polar angleresolution for highest energyelectrons [6]

I Good reconstruction efficiencyI Low fake rate

0 500 1000 1500Energy [GeV]

0

50

100

150

200

rad

]µ

[θ

σ

LumiCal, 3 TeV, 40 BX < 75 mradθ50 mrad <

Polar Angle Resolution

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 23 / 29

LumiCal Performance

I LumiCal reaching desired polar angleresolution for highest energy electrons [6]

I Good reconstruction efficiencyI Low fake rate

40 60 80 100 120 [mrad]θ

0

0.5

1

1.5

Eff

icie

ncy

σLumiCal, 3 TeV, 40BX, 101500 GeV Electrons190 GeV Electrons100 GeV Electrons50 GeV Electrons10 GeV Electrons

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 23 / 29

LumiCal Performance

I LumiCal reaching desired polar angleresolution for highest energy electrons [6]

I Good reconstruction efficiencyI Low fake rate

50 100 150 [mrad]θ

4−10

3−10

2−10

1−10

Fa

ke

ra

te σLumiCal, 10Bkg: 3 TeV, 40BX

0 GeV < E < 10 GeV 10 GeV < E < 25 GeV 25 GeV < E

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 23 / 29

BeamCal Performance

I BeamCal dominated by incoherent pairbackgrounds

I Strong rejection of energy from thebackgrounds leads to lowerefficiency [6]

I Given near zero fake rate could tuneselection for slightly better efficiency

I Resolutions much worse than in LumiCal10 20 30 40 50

[mrad]θ

0

0.5

1

1.5

Eff

icie

ncy

σBeamCal, 3 TeV, 40BX, 31500 GeV Electrons1000 GeV Electrons500 GeV Electrons250 GeV Electrons

CLICdp

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 24 / 29

BeamCal Performance

I BeamCal dominated by incoherent pairbackgrounds

I Strong rejection of energy from thebackgrounds leads to lower efficiency [6]

I Given near zero fake rate could tuneselection for slightly better efficiency

I Resolutions much worse than in LumiCal

10 20 30 40 50 [mrad]θ

4−10

3−10

2−10

Fa

ke

ra

te σBeamCal, 3Bkg: 3 TeV, 40BX

0 GeV < E

CLICdp

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BeamCal Performance

I BeamCal dominated by incoherent pairbackgrounds

I Strong rejection of energy from thebackgrounds leads to lower efficiency [6]

I Given near zero fake rate could tuneselection for slightly better efficiency

I Resolutions much worse than in LumiCal

400 600 800 1000 1200 1400 1600Energy [GeV]

0

0.1

0.2

0.3

0.4

0.5

) [m

rad

]θ

RM

S(

BeamCal, 3 TeV, 40 BX < 40 mradθ15 mrad <

Polar Angle Resolution

CLICdp

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γγ→ hadron Background Mitigation

I Read out full bunch train and identify time of physicsevent

I Select hits around the event using the timeresolution of the sub-detectors

I Calculate truncated mean of hittimes and correct for time-of-flight

I Accept reconstructed particles depending on particletype, cluster time, and transverse momentum

I Selection cuts reduce background from 1.2 TeV to100 GeV.

I Further background reduction through jet-clustering

A. Sailer Detector Requirements and Software for CLIC - HK DetSoft, Jan 16, 2020 25 / 29

γγ→ hadron Background Mitigation

I Read out full bunch train and identify time of physicsevent

I Select hits around the event using the timeresolution of the sub-detectors

I Calculate truncated mean of hittimes and correct for time-of-flight

I Accept reconstructed particles depending on particletype, cluster time, and transverse momentum

I Selection cuts reduce background from 1.2 TeVto 100 GeV.

I Further background reduction through jet-clustering e−e+→ HH with γγ→ hadronbackground overlaid before and after

timing selection cuts.

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Flavour Tagging

I Focus here on relative performance of differentvertex resolutions

I Optimising flavour tagging performance still work inprogressI Improvements in trackingI Tune machine learning parametersI Reject vertices from material interaction

Mis

identification e

ff.

3−10

2−10

1−10

1

Beauty contaminationmµ3 mµ5 mµ7

LF contaminationmµ3 mµ5 mµ7

CLICdp

° < 90θ < ° = 500 GeV, 20CM

Di­jet events, E

Charm eff.0.5 0.6 0.7 0.8 0.9 1

σm

/ o

the

r µ

3

0.2

0.4

0.6

0.8

1

1.2 Beauty contamination

LF contamination

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Flavour Tagging

I Focus here on relative performance of differentvertex resolutions

I Optimising flavour tagging performance still work inprogressI Improvements in trackingI Tune machine learning parametersI Reject vertices from material interaction

Mis

identification e

ff.

3−10

2−10

1−10

1

Charm contaminationmµ3 mµ5 mµ7

LF contaminationmµ3 mµ5 mµ7

CLICdp

° < 90θ < ° = 500 GeV, 20CM

Di­jet events, E

Beauty eff.0.5 0.6 0.7 0.8 0.9 1

σm

/ o

the

r µ

3

0.4

0.6

0.8

1

1.2 Charm contamination

LF contamination

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Jet Clustering

I γγ→ hadron background and longitudinalboost due to Beamstrahlung make LEP jetalgorithms unsuited for CLIC

I Use hadron collider jet algorithm featuresI Cluster forward particles into beam jetsI Benefit from longitudinal invariance.

Particle distance measure using∆R2 = ∆η2 + ∆φ2

I Specialised VLC jet algorithm [7]I Reconstruction parameters can and have

to be tuned to specific analyses, see thepresentation on the physics studies

144 Page 6 of 16 Eur. Phys. J. C (2018) 78:144

Fig. 3 The area or footprint ofjets reconstructed with R = 0.5with the three major families ofsequential recombinationalgorithms. The two shadedareas in each column correspondto a jet in the central detector(θ = π/2) and to a forward jet(θ = 7π/8). The jet axis isindicated with a cross

(rad.)π/φazimuth−0.5 0 0.5

(rad

.)π/θ

pola

r ang

le

0

0.2

0.4

0.6

0.8

1

/2π = θ

/8π = 7θ

-e+generalized e

1-cos Rijθ1 - cos

)2j

,E2i

= 2 min(Eijd

2i = EiBd

long. invariant

2R2 RΔ)2

Tj,p2

Ti = min(pijd

2Ti

= piBd

=1)γ=β (-e+VLC e

2Rijθ1 - cos

)2j

,E2i

= 2 min(Eijd

2Ti

= piBd

γ0.5− 0 0.5 1 1.5

β

1−

0.5−

0

0.5

1t

gen. k-e+e(~Durham)

t anti-k-e+e

Cambridge

Valencia

VLC-angular

anti-VLC

constant size ** shrinking footprint

hard

& c

oll.

first

**

angu

lar *

* so

ft &

col

l. fir

st

Fig. 4 Diagram of the parameter space spanned by exponents β andγ of the VLC algorithm. On the y-axis generalisations with beam jetsof the LEP/SLD algorithms are found, with the Cambridge algorithmwith angular ordering at the origin and the Durham or kt algorithm atβ = 1. Choosing β = -1 yields reverses the clustering order (like inanti-kt algorithm [38]). Choosing non-zero and positive values for γ

yields robust algorithms with a shrinking jet area in the forward region

slower decrease of the area when the polar angle goes to 0 orπ .

For γ = 0, diB = E2βi and we retrieve the generalised

e+e− algorithms with constant angular opening: the gener-alised Cambridge algorithm [17] for β = 0 and generalised kt

or Durham [18] for β = 1. Choosing β = -1 yields an e+e−variant of the anti-kt algorithm [38]. A schematic overviewof the algorithms in (β, γ ) space is given in Fig. 4.

4 Jet energy corrections

Before we turn to a detailed simulation including overlaidbackgrounds and a model for the detector response, we studythe perturbative and non-perturbative jet energy correctionsof the algorithms. Both types of corrections are closely con-nected to the jet area [39]. In this section we quantify theirimpact, following the analysis of Ref. [39]. This first explo-ration of the stability of the algorithms should be extended infuture work to quantify the impact of next-to-leading cor-rection, as performed for instance in Ref. [40]. Also therobustness of the conclusions for a variety of different setsof parameters (tunes) of the Monte Carlo simulation meritsfurther study.

4.1 Monte Carlo setup

The Monte Carlo simulation chain uses the MadGraph5_aMC@NLO package [23] to generate the matrix elementsof the hard scattering 2 → 2 event. Several processes arestudied, but results in this Section focus on e+e− → qq̄at

√s = 250 GeV and e+e− → t t̄ with fully hadronic top

decays at√s = 3 TeV. The four-vectors of the outgoing

quarks are fed into Pythia 8.180 [24], with the default tuneto LEP data, that performs the simulation of top-quark andW boson decays, the parton shower and hadronisation. Nodetector simulation is performed and initial-state radiationand beam energy spread are not included in the simulation.Particles or partons from the Pythia event record are clusteredusing FastJet 3.0.6 [33] exclusive clustering with N = 2.The default (“E-scheme”) recombination algorithm is usedto merge (pseudo-) jets.

123

Jet areas obtained from different types of jetclustering algorithm

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Summary

I In last years, studied and documented CLICdet performanceI Re-use of existing components, and developments were needed, allowed detailed studies

to be performedI Detector and software can fulfil the requirements for physics at CLIC

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References

[1] CLICdp Collaboration. “Higgs physics at the CLIC electron–positron linear collider”. In: Eur. Phys. J. C 77.7(2017). URL: https://arxiv.org/abs/1608.07538.

[2] CLICdp collaboration, H. Abramowicz, et al. “Top-quark physics at the CLIC electron-positron linear collider”. In: J.HEP 2019.11 (Nov. 2019), p. 3. DOI: 10.1007/JHEP11(2019)003. arXiv: 1807.02441.

[3] N. Alipour Tehrani et al. “CLICdet: The post-CDR CLIC detector model”. In: (Mar. 2017). CLICdp-Note-2017-001.URL: https://cds.cern.ch/record/2254048.

[4] L. Linssen et al., eds. Physics and Detectors at CLIC: CLIC Conceptual Design Report. CERN-2012-003,arXiv:1202.5940. CERN, 2012.

[5] E. Brondolin et al. “Conformal tracking for all-silicon trackers at future electron–positron colliders”. In: Nucl. Instr.Meth. A956 (2020), p. 163304. DOI: 10.1016/j.nima.2019.163304.

[6] Dominik Arominski et al. A detector for CLIC: main parameters and performance. 2018. arXiv: 1812.07337[physics.ins-det]. URL: https://cds.cern.ch/record/2649437.

[7] Ignacio Garcia Garcia et al. “Jet reconstruction at high-energy electron–positron colliders”. In: Eur. Phys. J. C 78.2(June 2017), p. 144.

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