Forward Calorimeter
upgrade in ALICE
Tatsuya Chujo
Univ. of Tsukuba
Oct. 29, 2016
France-Japan SAKURA Workshop on small-x physics at the LHC
Univ. of Tokyo, Komaba

Outline
1. Physics motivations
2. Forward Calorimeter Project in ALICE• Detector design, organization• MAPS detector• PAD detector
3. Schedule
4. Summary2

Gluon Density in nucleon/ nuclear at high energy
distribution function

high energy

hard process

momentum fraction

At small x and small Q2, the parton density
will become large by non-linear effects due to gluon fusion!Gluon density saturate, called;• Gluon Saturation, or• Color Glass Condensate (CGC)3

J'K9+"L>

CGC

Color Glass Condensate (CGC)./01'%2%"0(3'4#"-+"&① Saturated gluon state by the quantum fluctuation② Universal picture at high energy nucleus andnucleon③ But no clear experimental evidence for thecreation of CGC#"$"%&'(!"#$%&'$('')#*+,
To find/ test CGC by
experiment!

#"$"%&')（１）more forward（２）Higher energy（３）proton < nucleus（４）cleanness: h < gamma!")#"-+"&

56 ./01'!+"7/8,%'4,9:'+7'4#"-+"&'"%0/#2';6 </44/89,7'7#'=%+>9"%'&/"%87'!1#7#2'+7'4#"-+"&'?97@'! A%+>9"%=%27'/>'!#>>/$,%'$('B/'7%812/8>'
C*ADBEAFGB3'GF<H'I

Signal of CGC: RpA•

Two scenarios forforward ! production
in p+A at LHC:–

Normal nuclear effects
linear evolution,
shadowing–

Saturation/CGC running
coupling BK evolution

A. Rezaeian, PLB 718, 1058

• Strong suppression in direct ! RpA.
• Signals expected at forward ", low-intermediate pT.
5

QGP thermalization mechanism
QGP (known):
rapid thermalization, stronglyinteracting perfect fluid

M2L2#-2'I

CGC

collisions"*+,-.,

QGP

hadron gas/"$"'%"0.""""""""""""""""""/"$"&"0.""""""""""""""""""""""""""""""""""""""/$"&12"0.34""""""""""""""""""""/$"5&"0.34

7CGC• High energy nucleus ＝ What is the initial condition?
• Why so rapidly thermalized (t=0.6 fm/c)?
• Instability of strong color field？" need to determine

high density
color field

the initial condition clearly.
• Find the clear evidence for CGC formation as an initialcondition (or exclude it).
QGP rapid thermalization?

Long range correlations in AA and pA (“Ridge”)
RHIC (STAR, Au+Au 200 GeV)

LHC (ALICE, pPb, 5.02 TeV)

• long range !" correlations (ridge) at RHIC and LHC.
• Origin is still unknown.
• by CGC (initial condition) or others?
7photons vs. charm: D0 meson (LHCb)

8

RpPb for D0 (LHCb)

9

Isolated photons vs. hadrons
Isolated direct photons canprovide strong constraints on
the gluon PDFs

photons

R. Ichou and D. d’Enterria, Phys. Rev. D 82, 014015 (2010)• LO dominant process: quarkgluon Compton.
• Quark-anti-quark annihilation
contributing mostly at large x.
• NLO: At LHC, the majority ofprompt photons are produced in
the fragmentation process• Fragmentation photon can belargely suppressed by the isolation
cut.

→quark-gluon Compton
process dominant, more directaccess to the gluon PDFs andsaturation physics

hadrons

by T. Peitzmann10M2/K9%2%>>'#4'71/>'=%+>9"%=%27'./01'&%2>/7('0,9#2'=+77%"'N.#7'O9+"L'A+77%"

Nuclear effect:;<=4/"6>?/?@"A6B① Evidence for CGC
・direct photon ＝ most clean signal for CGC
・Forward direct photon: RpA " CGC or not.

② Nature of CGC
・Direct photon RpA: system, multiplicity, y & pT dep.

A. Rezaeian, PLB 718, 1058

CGC

676

" characterize CGC size, structure, onset.

③CGC and QGP thermalization mechanism

6789

・Size of CGC (direct photon) and QGP temperature,
expansion velocity, fluctuation.
・Forward photon /hadron vs. mid. photon / hadron! correlation between CGC size andQGP thermalization (e-by-e)" Mechanism of rapid thermalization④ Connection to other research fieldsFPQ*R')#"-+"&''!1#7#2'＝*S*'>7+7%*S*'>7+7%

・「strong field」: QCD color (gluon) field vs. QED field (Neutron star)
・「forward」：High energy cosmic rays

p+p 13 TeVHigh multiplicity event

FPQ*R'=/&'C<*+,3'G.DB3'TG*H
FPQ*R'=/&'C<*+,3'G.DB3'TG*H'!1#7#2'＝7%=!%"+79"%'
1+&"#2＝%:!+2>/#2'U%,#8/7(ALICE FoCal Project12

Kinematic reach by FoCal13

FoCal-E prototypes• Si/W sandwich calorimeter layer structure:- W absorbers (thickness 1X0)+ Si sensors• Longitudinal segmentation:- 4 segments low granularity (LG)
- 2 segments high granularity (HG)
• LG segments- 4 (or 5) layers- Si-pad with analog readout- cell size 1 x 1 cm2- longitudinally summed• HG segments- single layer- CMOS-pixel (MAPS*)- pixel size # 25 x 25 $m2- digitally summed in 1mm2 cells*MAPS = Monolithic Active Pixel Sensor (cm)14

FoCal project (Institutes)

15

High Granularity (HG) 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 $m pixels- 640 $s integration time(needs upgrade – too slow for experiment)• 39 M pixels total• Test with beams at DESY, CERN PS, SPS

Event Display:measurement (DESY) of
pile-up of two 5.4 GeV
electrons, demonstrates
two-shower separation
capabilities
16

High Granularity (HG) Prototype, MAPS

Linearity

Energy resolution

Shower profile17

Low Granularity (LG) Prototype, PAD (JP, US))#*+,'GF<'!"#7#'7(!%3'5'>%0=%27'CDVWP3'T>9L9$+3'*WBET#L(#H

18

summing board

APV25

beam

FOCal PAD (4 segments)

MAPSTest	  beam	  setup	  @	  PS	  (same	  for	  SPS)	  in	  2015

Linearity and energy resolution (2015 beam test, Tsukuba)• Good linearity
within ~3%from PS to SPS
energies.

• Stochastic term: close to
the expected value.
• Constant term: < 10%France-Japan SAKURA Workshop on small-x physics at the LHC, Oct. 29, 201620*RVW'BGB'7%>7'$%+='C;Y5[6Y\Hbeam

FOCal detector
T"/00%"'CGF<]AFGBH

2 staff members from Tsukuba (Motoi Inaba, TC)
4 undergrad students from Tsukuba
1 master student from Nara W. U.
4 from Utrecht (MAPS)
Total: 112016 SPS test beam (Sep. 7-12)Signals from new SBs• New summing board (by M. Inaba)
installed for all 4 LGLs, tested with beams(<140 GeV/c).
• Wider dynamic range and• Also the data matching between MAPS
and PAD (LGL) is possible by the trigger
bits recording in the both data stream
22

Pulse	  Hight	  (a.u.)Electron signals at 130 GeV/c
LGL	  1SPS;	  130	  GeV/c,	  e+LGL	  2time	  (1	  time	  bin	  =	  25	  ns)LGL	  3

LGL	  4

Y. Kawamura, T. Suzuki
23

YAG	  laser	  	  +	  postion	  scan	  system	  for	  Si	  PAD

Si	  PAD	  I-­‐V,	  C-­‐V	  measurements

5	  x5	  mm^2	  Si	  PAD

Hex	  Si	  PAD

Visited	  the	  ILC	  group	  @	  Kyushu	  Univ.	  (2016.09)

R&D for fast readout: RD51 (VMM2/3)• R&D and test for VMM2 and VMM3 hybrid boards with SRS +DATE (ALICE DAQ) system.
• R&D of combined design; on-board VMM2/3 on FoCal summingboard, and modification for FoCal needs (dynamic range & triggercapability)^AA;SRS readout

ALICE DATE for VMM (developed by RD51)

France-Japan SAKURA Workshop on small-x physics at the LHC, Oct. 29, 201625

Tentative schedule

finalize detector
LOI (2016) spec (2017)

final prototype (MiniFoCal), TDR(2018/2019)

final design(2020)

production & test
(2021-2023)
physics
w/ Mini-FoCal(2021-2023)

Physics prototypes, beam test and analysis(2016-2019)pre-assembly(2023)
production & test
(2021-2023)
physics w/ Mini-FoCal(2021-2023)

installation andcommissioning(2024-2025)

physics(2026-2029)

physics(2026-2029)

France-Japan SAKURA Workshop on small-x physics at the LHC, Oct. 29, 201626

Summary and Future Plan
• Rich physics and unexplored region @ forward
rapidity at LHC• CGC, nature of CGC (size, structure, .. ).
• Connection to QGP thermalization mechanism andstrong field (origin of QGP, initial condition).
• Long range delta eta correlations (origin of ridge)• Extensive ongoing R&D efforts, well defined targets.

• PLAN:• beam background study (and hopefully initial physicsmeasurement) by the prototype during the Run-2(2018).
• mini FoCal (3 <η<4) in Run-3 (2021-2023).
• full FoCal (3.2 <η < 5.3) in Run-4 (2026-2029).
France-Japan SAKURA Workshop on small-x physics at the LHC, Oct. 29, 201627