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