Forward Calorimetry in
ALICE at LHC
Tatsuya Chujo 1)
for the ALICE Collaboration

M. Inaba 2), W. Sato 1), M. Hirano 1) ,H. Yokoyama 1), K. Ito 1)
1) University of Tsukuba
2) Tsukuba University of Technology
Hawaii 2014, 4th APS-DNP/JPS joint meeting
Oct. 11, 2014

CGS picture at LHC• From the results in d-Au (RHIC)

RHIC

LHC

and p-Pb (LHC) collisions, there
are indications of Color Glass
Condensate (CGC), but notconclusive yet.

• Many observables are usedhadrons, which include final stateinteractions.

• A cleaner probe at forward

rapidity is necessary, such as
direct photons
Advantage at LHC : Larger
kinematic reach in saturation
region at LHC, compared to RHIC.

Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 2

Initial condition and thermalization%Ini(al%condi(on,%CGC,%%early%thermaliza(on%Color%Glass%
Collision%
Condensate%(CGC)

“Glasma”

sQGP%produc<on,%thermal%
dynamics%QGP

strongly%coupled%%
Quark%Gluon%Plasma%% Hadron%gas
(sQGP)

t%=%@1%fm%%%%%%%%%%%%%%%%%%t%=%0%fm%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%t=%0.6%fm/c%%%%%%%%%%%%%%%%%%%%t=%20%fm/c%
Time

RHIC/LHC data suggests an early thermalization of QGP(< 0.2 fm), and it is still a big missing link between initialcondition to QGP.
➠ Direct access to initial condition by direct photon
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 3

Forward Calorimeter (FoCal) in ALICE•Electromagnetic calorimeterfor γ and π0 measurements,with Hadron Calorimeter.
• At z ≈ 8m (outside magnet)
3.3 < η < 5.3

Main challenge: separate γ/π0 at high energy• Need small Molière radius, high-granularity read-out• Si-W calorimeter, granularity ≈ 1mm2
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 4

FoCal-E Strawman Design• Si/W sandwich calorimeter layer structure:- W absorbers (thickness 1X0)+ Si sensors• Longitudinal segmentation:- 4 segments low granularity (LGL)- 2 segments high granularity (HGL)• LGL segments (PAD)- 4 (or 5) layers of Si/W
- Si-PAD with analog readout- cell size 1 x 1 cm2- 8 x 8 = 64 PADs per layer- signal are longitudinally summed• HGL segments (MAPS)- single layer with W.
- CMOS-pixel (MAPS*).
- pixel size ≈ 25 x 25 μm2- digitally summed in 1mm2 cells*MAPS = Monolithic Active Pixel Sensor
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 5

Detector Performance (simulation)
Energy resolution (FoCal-E)

Pion rejection factor•

Reasonable energy resolution, extremely good two-shower separation
with HG segments (~0.2 mm position resolution at Eγ > 100 GeV)

•Efficient for pion rejection (via shower shape analysis)

Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 6

High Granularity Layer (HGL) Prototype, MAPS
MAPS prototype• 4x4 cm2 cross section, 28 X0 depth• 24 layers: W absorber + 4 MAPS each
• MIMOSA PHASE 2 chip (IPHC Strasbourg)- 30 μm pixels- 640 μs integration time(needs upgrade – too slow for experiment)• 39 M pixels total• Test with beams at DESY, CERN PS, SPS๏ Responsibility: Utrecht, NIKHEF, Bergen
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

Event Display:measurement (DESY) ofpile-up of two 5.4 GeV
electrons, demonstrates
two-shower separation
capabilities
T. Chujo (U. Tsukuba) 7

Low Granularity Layer (LGL) Prototype, PAD•LGL	  (PAD)	  prototype	  (ORNL):- Si-PAD (Hamamatsu S10938)- cell size 1x1 cm2- longitudinally summed (4 segments),
analog readout.
- W layer per Si-PAD•Readout	  system:– ORNL	  ASICs,	  on	  a	  summing	  board.
– RD-­‐51	  SRS	  readout	  system:• APV25	  hybrid	  (128	  ch,	  pre-­‐amp,	  shaper)• SRS	  Front	  End	  Card	  (FEC)	  and	  ADC.
๏ SRS:	  Scalable	  Readout	  System	  (point-­‐to-­‐point	  readout)๏ Responsibility:	  Tsukuba,	  ORNL

APV 25 hybrid (master, slave)Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 8

RD51 SRS FEC/ADC for LGL(PAD)
LAN cable(FEC⇿DAQ) FoCal LGL

APV25 hybrid

HDMI cable(APV ⇿ ADC)DAQ (mmDAQ**)

RD-51 FEC/ADC* SRS-ADC:12 bit 128 ch. ADC 40MS/s , 8x HDMI ports)* mmDAQ: Micromegas DAQ system for SRS.
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 9

Prototype of “a strawman design”

LGL (PAD), 4 segments
w/ summing board•

LGL PAD:LGL (PAD) + HGL (MAPS x2)“strawman detector”– Importance of proper grounding and shielding on (i) detectors, (ii) APV, (iii) LV
power supply to summing board.
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 10

CERN PS beam test (2014)✓ Beam time:– Sep. 17 - Oct. 1, 2014
✓ Beam line: PS T9 beam line•

Beam energy:– 2 - 10 GeV/c (negative)✓ Trigger: 10x10 cm2 & 1x1 cm2 Scinti. +Cherenkov (ON/OFF)✓ Responsibility:– LGL (PAD) :Tsukuba, ORNL– HGL (MAPS) Utrecht, NIKHEF, Bergen✓ LGL:

Drawing by Brink, A. van den (Utrecht Univ.)– PAD Silicon pad bias voltage: -100V– Operated in the black box.
– First time exposed by beam.
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 11

Some plots from PS test; LGL (PAD)(1) Online display (e- enhanced, 2 GeV/c beams)
pedestal

ADC
(ch.)
ADC
(ch.)

signal25 ns
Time bin(2) Offline analysis(e- enhanced, 2 GeV/c beams)- Looked at a hit candidate PAD only.
- Clear electron like shower is seen.

Oct 11,2014

Time bin (25 ns/bin)
Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 12

4. Summary• Proposing a Forward Calorimeter in ALICE for direct photon
measurement at η= 3.3 - 5.3.
• A prototype has been build, and it consists of LGL (PAD) andHGL (MAPS) as the EMCal part.
• The integrated system of FOCAL-E (HG+LG) has beentested for the first time at PS (Sep. 2014).
• First look at the data, analysis is ongoing.
Outlook↑ Beetle hybrid chip•

Results from PS test beam.

•SPS beam test in Nov. 2014, integrated
readout for LGL and HGL.

•Upgrade readout chip from APV to Beetle(trigger andhigh rate capability) w/ RD51.
FoCal•

LoI is under preparation.

Special thanks to: T. Tamagawa, T. Kitaguchi (RIKEN)
Oct 11,2014

Hawaii 2014 APS-DNP/ JPS joint meeting

T. Chujo (U. Tsukuba) 13