1

T. Peitzmann (Utrecht University/Nikhef)

High-Granularity EM Calorimetry for Forward Measurements

CFNS Forward Workshop 2018, Stony Brook, 17.10.2018

Outline• Physics case for FoCal proposal in ALICE• FoCal baseline design, performance• R&D: high-granularity EM calorimeter• Summary

PDF Uncertainties and Saturation

• large uncertainties of nPDFs• parameterised nuclear modification• recently updated to allow more freedom (e.g. flavour dependence)

• x-dependence?• very little dependence for x < 10-2

• non-linear effects from high gluon density• gluon saturation?

2

EPPS16

x

RPb g(x,Q

2=1.69GeV

2 )

EPPS16

xRPb g(x,Q

2=10GeV

2 )

EPPS16, EPJC 77, 163

Black DiskLimit

s3ln

EM probes - kinematic coverage

x6−10 5−10 4−10 3−10 2−10 1−10 1

Q (G

eV)

1

10

210

EIC1

EIC2

DIS p

DIS A

FO

CA

L

CM

S

AT

LA

S

AL

ICE

Pbsat

Q

psat

Q

x-Sensitivity – Charm vs. Photons?

3

• LO kinematics estimates provide rather lower limit for x2

• but: higher orders contribute significant tail towards large x2

ps (TeV) y pT (GeV/c) z x2

0.2 4 2 0.3 1.2 · 103

8.8 0 2 0.3 1.5 · 103

jet 8.8 4 20 1 8.3 · 105

8.8 4 2 0.3 2.8 · 105

D 8.8 4 0 0.5 1.5 · 105

8.8 4 4 1 1.7 · 105

8.8 4.5 4 1 1.0 · 105

dσd(log(x 2

))/d

σ

x2

Isolated γInclusive D 0

Inclusive π0

√s = 8 .8 TeV5 < pT < 20GeV4 < η < 5

• compare D0 (LHCb) and prompt γ (FoCal)• expect better sensitivity for photons

• x-distributions from NLO pQCD

no analytical approximation, taking into account η of recoil parton

x1,2 2mTps

exp (±y)

• x-distributions from PYTHIA

log(x2)6− 5− 4− 3− 2− 1− 0

) (ar

b. u

nits

)2

dN/d

(log

x

5−10

4−10

3−10

2−10

1−10

PYTHIA pp 8.8 TeV

< 4η < 2 GeV/c - 3.5 < T

- p0 D

< 4.5η < 6 GeV/c - 4 < T

- 4 < pγ

x-Q2-Sensitivity

6−10 5−10 4−10 3−10 2−10 1−10 1x2

1

10

210

2Q

<5.0[GeV/c]T

<4.5, 4.0< pη : 4.0< γ

> = 1.6e+01 2> = 3.7e-05, <Q2<x

6−10 5−10 4−10 3−10 2−10 1−10 1x2

1

10

210

2Q

<5.0[GeV/c]T

<4.0, 4.0< pη : 3.5< γ

> = 1.6e+01 2> = 5.3e-05, <Q2<x

6−10 5−10 4−10 3−10 2−10 1−10 1x2

1

10

210

2Q

<3.0[GeV/c]T

<4.5, 2.0< pη : 4.0< γ

> = 6.1e+00 2> = 2.5e-05, <Q2<x

6−10 5−10 4−10 3−10 2−10 1−10 1x2

1

10

210

2Q

<5.0[GeV/c]T

<4.0, 4.0< pη : 3.5< 0D> = 2.8e+01 2> = 9.4e-04, <Q2<x

6−10 5−10 4−10 3−10 2−10 1−10 1x2

1

10

210

2Q

<1.0[GeV/c]T

<4.0, 0.0< pη : 3.5< 0D> = 5.1e+00 2> = 1.0e-03, <Q2<x

PYTHIA pp 8.8TeVforward measurements

D0

γ

3.5 < η < 4.04.0 < pT < 5.0 GeV/c

3.5 < η < 4.04.0 < pT < 5.0 GeV/c

3.5 < η < 4.00.0 < pT < 1.0 GeV/c

4.0 < η < 4.54.0 < pT < 5.0 GeV/c

4.0 < η < 4.52.0 < pT < 3.0 GeV/c

< x2 > = 1.0 ⋅ 10−3

< Q2 > = 5.1 GeV2

< x2 > = 3.7 ⋅ 10−5

< Q2 > = 16 GeV2

FoCal in ALICE

• main challenge: separate γ/π0 at high energy• need small Molière radius, high-granularity read-out

• Si-W calorimeter, effective granularity ≈ 1mm2

5

electromagnetic calorimeter (FoCal-E) for γ and π0 measurement

preferred scenario:• at z ≈ 7m (outside solenoid magnet)

3.3 < η < 5.3• add hadronic calorimeter (FoCal-H)

under internal discussionpossible installation in LS3

advantage in ALICE: forward region not instrumented, “unobstructed view”

note: two-photon separation from π0 decay (pT = 10 GeV/c, y = 4.5, α = 0.5) is d = 2 mm!

The FoCal Detector – Strawman Design

6

studied in performance simulations:

20 layers: W (3.5mm ≈ 1 X0) + Si-sensors

hybrid design (2 types of sensors)• Si-pads (≈ 1 cm2):

energy measurement, timing(?)• CMOS pixels (≈ 30x30 µm2):

two-shower separation, position resolution

543210

Longitudinal segmentation

HG cells

1 HG cell

1 mm

1 c

m

LG cells

LG layer HG layerabsorber

Transverse segmentation

Si-pads Si-pixelspixel/pad

size ≈ 1 cm2 ≈ 30x30 µm2

total # pixels/pads ≈ 2.5 x 105 ≈ 2.5 x 109

readout channels ≈ 5 x 104 ≈ 2 x 106

assuming ≈ 1m2 detector surface

pads pixels

ALI-SIMUL-307251

Direct γ Performance in pp• combined rejection (invariant mass + shower shape, isolation)• combined suppression of background relative to signal: factor ≈ 10

• largely pT-independent

7

)c (GeV/Tp

4 6 8 10 12 14

/all

clus

ters

dir

γ

3−10

2−10

1−10

1

= 13 TeVspp < 5.0η4.0 <

7m position

ALICE simulationFoCal upgrade

< 3.0 GeVE+HT,isop=0.4, isoR no selection

dec rej (IM+SS)isolation

dec rej + iso

Direct 𝛾/all cluster ratio

direct photon/all > 0.1 for pT > 4 GeV/c

Direct 𝛾 uncertainty

≈ 20% uncertainty at pT = 4 GeV/cdecreases with increasing pT

8

Uncertainties can be improved significantlyStill some discussion ongoing: choice of Δ𝜒2, effect of DGLAP evolution, shape of parameterisation

Work in progress!

uncertainty of nPDFs without/with FoCalJ. Rojo et al, priv. comm.,arXiv 1610.09373,1706.00428,1802.03021

)c (GeV/Tp

0 5 10 15 20

pPb

R

0

0.2

0.4

0.6

0.8

1 = 8.8 TeVNNs

< 5.0η4.0 <

ALICE simulation

FoCal upgrade

Impact of Forward Photons on nPDFsPerformance estimate of FoCal measurement

Extensive R&D Program Ongoing• requires to go beyond state of the art

• pixel sensors needed for pion rejection (two-shower separation)• Si-pads needed for energy resolution and timing

• proof of principle demonstrated• successful test of first digital pixel calorimeter (JINST 13 (2018) P01014)• investigating several options for pad sensor readout• ongoing test-beam program

• test setup with pads currently in ALICE cavern

• still significant R&D steps necessary• modifications to ALPIDE sensor• optimisation of pad readout• general design (minimisation of Molière radius, etc.)

9

FoCal R&D: Si-pad readout

10

several calorimeter prototypes with pad readout from different groups

extensive test beam campaigns

recently installed 27 cm x 9 cm full depth prototype in ALICE cavern

measurements in pp collisionsperformance under realistic conditions?

most important issue:readout electronics with sufficient dynamic range (~16bit?)

plan to investigate several avenues: SAMPA, CMS-HGCal, ATLAS-VMM, …

pad layer prototypes

ORNL/Tsukuba Kolkata/Mumbai

miniFoCal in ALICE cavern

W/Si-Pad Test-Beam Performance

11

ORNL/Japan Pad prototype with APV/SRS readout

India Pad prototype with custom chip (MANAS/ANUSANSKAR)

test beam performance agrees with simulations papers on instrumentation in preparation

ADC distributions

linearity

)R

Layer Number(X0 2 4 6 8 10 12 14 16 18 20

Mea

n A

DC

0

2000

4000

6000

8000

marker ==> Data)-bt*ea*t

0 (ADC = E

05 GeV20 GeV30 GeV40 GeV50 GeV60 GeV

longit. distrib.

(GeV)incidenceE10 20 30 40 50 60

)de

posit

ion

/Eσ

Reso

lutio

n (

0

0.05

0.1

0.15

0.2

0.25

DataFit with σ/E = a ⊕ b/E ⊕ c/E

resolution

Developing an Extremely Granular Calorimeter

12

~ CMS-HGCALpad size (0.5cm2)

X (mm)5 5.5 6 6.5

Y (m

m)

3.5

4

4.5

5

single electron shower measurement (244 GeV) in CMOS sensor

1

10

0.1 1 10

RM = 40 mmRM = 20 mmRM = 15 mmRM = 10 mm

x sep (m

m)

cell size (mm)

state of the artcalorimeters

CALICE SiW ECAL

digital pixel calorimeter

• go beyond state of the art• current technologies do not exploit the potential for two-shower separation

• digital pixel calorimeter• ~ mm effective cell size useful• analog read-out difficult on mm scale• use pseudo-analog value from pixel counting:

requires order of magnitude smaller pixel sizes

FoCal R&D: Si-W CMOS pixel

13

Utrecht/Nikhef, BergenJINST 13 (2018) P01014

24-layer prototype with MIMOSA sensors 39M pixels, 30μm pitch

• half layer with two sensors and 1.5mm W

• two half layers mounted together with opposite orientation to minimise dead areas

• total layer thickness ≈ 1 X0• full active layer with readout boards

within 1mm

A: MIMOSA sensor, B: PCB, C: tungsten

most important issue: readout speed/bandwidthMIMOSA sensor much too slow,now moving to ALPIDE sensor• synergy with ALICE ITS upgrade• needs chip design steps

preparing prototypes with current ALPIDE• full pixel prototype• hybrid (pixel/pad) prototype

Utrecht/Nikhef, Bergen, Charkov

four layers with flex-cable mounting

Single Event Hit Distribution - FoCal Pixel Prototype

14

very high hit density in shower core• not possible to reconstruct single shower particles from pixel clusters• have to use number of hits as response (not number of clusters)• saturation (overlap of clusters) likely for very high energy

X (mm)5 5.5 6 6.5

Y (m

m)

3.5

4

4.5

5

X (mm)5 5.5 6 6.5

Y (m

m)

3.5

4

4.5

5

X (mm)5 5.5 6 6.5

Y (m

m)

3.5

4

4.5

5

layer 4 layer 8 layer 12

244 GeV e-

15

average hit densities as a function of radius for different layers• low energy: early shower maximum, profiles broaden and decay with depth • high energy: profiles broaden with depth, increase up to shower maximumshower measurements with unprecedented detail!

Distance to shower axis (mm)1−10 1 10

)-2

Hit

dens

ities

(mm

2−10

1−10

1

10

210

310Layer 4

Layer 8

Layer 12

Layer 17

5 GeV e+

Distance to shower axis (mm)1−10 1 10

)-2

Hit

dens

ities

(mm

2−10

1−10

1

10

210

310Layer 4

Layer 8

Layer 12

Layer 17

100 GeV e+

R&D - Lateral Profiles

dNhit

dA(r)

)cMomentum(GeV/1 10 210

En

erg

y re

solu

tion

1

10

Simulation (ideal detector)

Simulation (real detector)

)-

Data(e

R&D - Energy Resolution

16

reasonable energy resolution • better results expected from LGL• note: sampling fraction < 1/1000• possibly still improve calibration, better sensor (ALPIDE) in the future proof of principle of digital calorimetry

E

E= a bp

E/GeV c

E/GeV

a = (2.95± 1.65)%

b = (28.5± 3.8)%

c = 6.3%

noise term c compatiblewith pedestal width (fixed in fit)

recent work on improved calibration

slightly worse than MC simulation, not unexpected

first paper published: JINST 13 (2018) P01014 https://arxiv.org/abs/1708.05164

R&D - Position Resolution

17

single shower position resolution obtained from width of residuals

can also provide excellent two-shower separation

calculate difference of position from• cluster in layer 0 and • center of gravity of

shower in layers 1 - 23

Energy(GeV)0 50 100 150 200 250

m)

µPo

sitio

n R

esol

utio

n(

25

30

35

40

45

50

)+/e-Data(e

Simulation

(mm)cx-0x0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2

Nor

mal

ized

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14244 GeV EXP

100 GeV EXP

50 GeV EXP

30 GeV EXP

5.4 GeV EXP

R&D Results: Core Energy

18

reasonable energy resolution of pixel calorimeter, sufficient for conceptual design

response and resolution for core energy hardly affected down to r = 5mm: adequate for very high particle density

detector response (number of hits) energy resolution

Cylinder radius (mm)0 5 10 15 20 25 30

Det

ecto

r res

pons

e

310

410

5.4 GeV30 GeV100 GeV

Cylinder radius (mm)0 5 10 15 20 25 30

/ E

(%)

Eσ

0

5

10

15

20

255.4 GeV

30 GeV

100 GeV

FoCal preliminary FoCal preliminary

Pixel (HGL) R&D Results: Single Event Profiles

19

electron showers have well defined profile, very narrow shower corepion showers show much larger fluctuation, often much wider

electron pion

Distance to the shower centre (mm)0 5 10 15 20 25 30

)-2

Hit

dens

ity (m

m

3−10

2−10

1−10

1

10

210

310

244 GeV EXP electron segment 2

a : -0.40

b : 2.50

Distance to the shower centre (mm)0 5 10 15 20 25 30

)-2

Hit

dens

ity (m

m

3−10

2−10

1−10

1

10

210

310

244 GeV EXP pion segment 2

a : -0.08

b : 1.01

Summary• Forward photon measurements at LHC provide unique

opportunity for low-x physics• complementarity with open charm: some advantages for

photons• needs detector upgrade: proposed FoCal detector in ALICE• more physics opportunities with FoCal

• Extensive R&D to go beyond state of the art• significant steps on pad sensor readout• towards digital pixel calorimetry

• proof of principle• working towards a full-scale detector• strong potential for future photon, electron, and jet

measurements 20

Backup Slides

Recent: PDF Fits Using Charm• open charm used in re-weighting

• significant reduction of uncertainties • significant suppression – on the low

side of current PDFs• significant pQCD uncertainties (scale,

fragmentation)• relies on shape of parameterisation:

very little x-dependence at low x!

22

nCTEQ15

µF=2.0µ0

Original Reweighted LHCb data ALICE data

0.6

0.8

1

1.2

µF=µ0

0.6

0.8

1

1.2

ycms(D0)

µF=0.5µ0

RpPb

0.6

0.8

1

1.2

-3 -2 -1 0 1 2 3

EPPS16

µF=2.0µ0

µF=µ0

ycms(D0)

µF=0.5µ0

-3 -2 -1 0 1 2 3

HELAC-Onia 2.0

D0

Original μF=μ0 μF=2.0μ0 μF=0.5μ0

0.4

0.6

0.8

1

1.2

1.4

1.6

x

RPb

g10

-510

-410

-310

-210

-1

nCTEQ15 EPPS16μF=2 GeV

D0

0.4

0.6

0.8

1

1.2

1.4

1.6

x

RPb

g10

-510

-410

-310

-210

-1

Kusina et al., arXiv:1712.07024

x-Dependence of PDF modification

• parameterisation of RA• shape similar to EPS09• at low x leads to “plateau” in log(x)

• likely not sufficient• more flexible PDF

used for LHeC estimates

23

EPPS16, EPJC 77, 163

R

Ai (x,Q

2) =

8<

:

a0 + a1(x xa)2 x xa

b0 + b1x↵ + b2x

2↵ + b3x3↵

xa x xe

c0 + (c1 c2x)(1 x)xe x 1

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

10-4

10-3

10-2

10-1

1

antishadowing maximum

EMC minimum

small-x shadowing

x

a

x

e

y

e

y

a

y0

EPPS16

x

R

A

i

(x,Q

2 0)

Helenius, Paukkunen, Armesto, arXiv:1606.09003

EPPS16 LHeC fits

Influence of x Dependence

24

parameterise nuclear modification of gluon PDFs

different x-sensitivity of probes reflected in nuclear modification factor

Simple Model based on PYTHIA – no proper Q2 dependence

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8

LHCb forward D0 scenario 1

toy model γ

toy model D0

RpA

pT (GeV/c)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8

scenario 2

RpA

pT (GeV/c)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8

scenario 3

RpA

pT (GeV/c)

10-6

10-5

10-4

0.001 0.010

0.0

0.2

0.4

0.6

0.8

1.0

10-6

10-5

10-4

0.001 0.010

0.0

0.2

0.4

0.6

0.8

1.0

10-6

10-5

10-4

0.001 0.010

0.0

0.2

0.4

0.6

0.8

1.0

Rg

Rg

Rg

scenario 1

x x x

scenario 2 scenario 3

RpA =∫ dx dσ/dx(pT, y) ⋅ Rg(x)

∫ dx dσ/dx(pT, y)

Main Physics Motivation for FoCal (A Hierarchy)1. prove or refute gluon saturation

• compare saturation models with linear QCD• depends on saturation model implementation and flexibility of PDF analytical shape

2. show invalidity of linear QCD at low x • can all potential measurement outcomes be absorbed in a modified PDF?

3. constrain the PDFs at low x • nuclei, also protons

• main observable: nuclear modification factor RpA of direct photons• saturation stronger in nuclei • possibly non-existent in protons (calculation of reference in models?)

25

R pPb

pT

EPPS16

ALICE pseudodata

EPS09mod

p+Pb

psNN = 8.160TeV

4 < < 5

Isolated

R = 0.4ET < 2GeV

1 2 3 4 5 6 7 8kT [GeV]

0.6

0.7

0.8

0.9

1.0

1.1

RpA

y = 3y = 4y = 5

p + Pb/ p + p ! + X,p

s = 8 TeV

CGC Calculation:Ducloué, Lappi, Mäntysaari, arXiv:1210.02206

• mechanism for modifications still unclear, possibly final-state interaction!• relation between initial- and final-state kinematics may be obscured• introduces additional systematic uncertainty

26

significant v2 for D mesons, similar results for HF-decay leptons

CMS Collaboration, CERN-EP-2018-076

(GeV)T

p0 2 4 6 8

2v

0.1

0.2

0.3CMS pPb 8.16TeV

< 0.54cm < 250, -1.46 < yofflinetrk N≤185

0DS0K

Λ

-Ξ

-Ω

)c (GeV/T

p

0 5 10 15 20 25 30 35

CP

Q

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2 ALICE Preliminary

= 5.02 TeVNNsPb, −p

+, D*+, D0Average D

Charged particles

10% ZN energy−Central: 0

100% ZN energy−Peripheral: 60

ALI−PREL−136823

nuclear modification for D mesons similar to charged hadrons,

deviation from Ncoll scaling at low pT

Final-State Modification of Open Charm in p–A?

rast

er

logi

cb

uff

ers analog data processing

serializer serializer serializer serializer

DACs+bias JTAG controller PULL+PULL test

640

640Sensor and Readout

27

current sensor too slow (642 µs/frame)• real detector will likely use derivative of ALPIDE (ALICE-ITS upgrade)

read out via 4 Spartan and 2 Virtex FPGAs

continuous data stream of 8GB/s

in-pixelmicro-circuits

charge collectingdiode

particle

≈5µm

10-2

0µm

700µ

m

++

++

+

-----

MAPS sensor:MIMOSA23 (IPHC)full frame readout

4 x 80MB/s

MIMOSA

6 x 320MB/s

2 x ≈2GB/s

x2

≈4GB/s to PC

...

...

...

...

Conc.Board

Spartan 6

Virtex 6

Two Shower Separation

28

evaluate separation capability: core energycalculate shower energy in cylinder of finite radiusstudy as function of radius

X (mm)

15−10−

5− 0 5 10 15

Y (mm)

15−10−

5−0

510

15

Z (m

m)

0

20

40

60

80

100

Y (mm)15− 10− 5− 0 5 10 15

Z (m

m)

0

20

40

60

80

100

X (mm)15− 10− 5− 0 5 10 15

Y (m

m)

15−

10−

5−

0

5

10

15

display of single event (with pile-up) from 244 GeV mixed beam

Detector Response

29

Number of hits100 150 200 250 300 350 400 450 500 550 600

Num

ber o

f occ

uran

ces

100

200

300

400

500

600

700Data

Fit result

Pedestal

Pion tracks

Number of hits0 20000 40000 60000 80000

Cou

nts

0

20

40

60

80

100

120

30GeV

50GeV

100GeV

244GeV

- minimum ionising particle (MIP) peak from pion tracks

- pedestal: noise distribution of full prototype

- response to electrons from SPS test beam

- calculated from per-event hit density distributions

Energy (GeV)1 10 210

Aver

age

resp

onse

310

410

Simulation (ideal detector)

Simulation (real detector)

Data

β Eα=Rcfit : N

Energy (GeV)1 10 210

Dev

iatio

n (%

)

6−4−2−0246

Energy (GeV)1 10 210

Aver

age

resp

onse

310

410

Simulation (ideal detector)

Simulation (real detector)

Data

=k ERcfit : N

Energy (GeV)1 10 210

Dev

iatio

n (%

)

6−4−2−0246

R&D - Energy Linearity

30

detector response from integrated event-wise hit densities• fit with linear and power law function, good linearity (power β = 0.98)note - not yet corrected:• different calibration for low and high energy• small effects of saturation at high energy

fit with : Nhits = k · E fit with : Nhits = ↵ · E

R&D - Cumulative Lateral Profiles

31

Distance from shower axis (mm)0 5 10 15 20 25 30

Num

ber o

f hits

0

10

20

30

40

50

60

70

80 Layer 2 Layer 4 Layer 8 Layer 12

contained

Distance from shower axis (mm)0 5 10 15 20 25 30

Frac

tion

of to

tal n

umbe

r of

hits

0

0.2

0.4

0.6

0.8

1

2 GeV 100 GeV

Distance to shower axis (mm)

8 9 10 11 12

Frac

tion

of h

its

0.8

0.85

0.9

0.95

1

contained

contained

extract cumulative distributions both per layer and integrated• some lateral leakage at higher energysmall Moliere radius: RM ≈ 11mm≈ 75% of hits within R = 5mm, 50% within R = 3mm, …

2 GeV e-

Energy(GeV)10 210

Cou

nts

1

10

210

310

410

Primary particle energy

Observed energy

Remaining pions

Energy(GeV)10 210

Rej

ectio

n fa

ctor

1

10

210

Interaction layer0 2 4 6 8 10 12 14 16 18 20 22

Nor

mal

ized

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

244GeV100GeV50GeV30GeV5GeV

Interaction layer0 5 10 15 20 25

Nor

mal

ized

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

244 GeV EXP pion

50 GeV EXP pion

R&D - Hadron Rejection

32

hadron rejection for realistic pion momentum spectrum:- cases of high deposited energy suppressed from low interaction

probability- additional rejection for low deposited energy from shower shape

longitudinal shower shape: cut on position of shower start

further discrimination via transverse shower shape: slope

π (Edep ≈ 30 GeV)

e (various energies)

m (GeV/c2)0 0.1 0.2 0.3 0.4

N

0

200

400

310×

ALICE SimulationPbPb 0-10%10M events

< 4.5η3.5 < c < 10.0 GeV/

T8.0 < p

More FoCal Physics Topics• low-x gluons (n)PDFs, saturation

• direct photon RpA

• π0-π0 correlations

• dijet correlations

• ridge/flow-like phenomena in pp, pA• correlations: forward photon – mid-rapidity hadron

• jet quenching at large y• neutral pion RAA

• miscellaneous• reaction plane in Pb–Pb

33

π0 in Pb-Pb

pT [GeV/c]

20 22 24 26 28 30

resolu

tion

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

PYTHIA pp 14 TeV

FoCal jets

pT resolution

[rad]

2 1 0 1 2 3 4 50

2000

4000

6000

8000

10000

ssf

truef

3.5 < η < 55 < pT < 15 GeV/c

PYTHIA pp 14 TeV

π0π0 correlation (bkg subtracted)co

un

ts