DCal for the ALICE experiment at LHC
Tatsuya Chujo
中條 達也
University of Tsukuba(for the ALICE D-Cal Project)
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

Outline	
1. Introduc/on	  – Jet	  quenching	  at	  RHIC	  and	  LHC	  2. Dijet	  Calorimeter	  (=DCal)	  in	  LHC-­‐ALICE	  3. Physics	  cases	  for	  DCal	  4. Current	  stats	  and	  plan	  5. Summary	  ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)2Jet quenching at RHIC
R AA =Phys. Rev. Lett. 91, 072304 (2003).

YieldAuAu / 〈Nbinary 〉 AuAuYieldpp

In	  Au+Au	  central	  collisions	  at	  RHIC:	  Trigger hadron: p > 4 GeV/c,– High	  pT	  yield	  suppression	  Associated hadron: p > 2 GeV/c• Gluon	  density:	  dNg/dy	  ~	  1100	  • Energy	  density:	  ε	  >	  100	  ε0	  	  • Precise	  measurement	  at	  very	  high	  pT.	  
– Disappearance	  of	  away	  side	  jet	  TT

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)?

Di-­‐hadron	  correla/on:	  surface	  bias	  • Δφ di-hadron correlations for d+Au, Au+Au at √sNN = 200 GeV (STAR).
• Trigger hadron pT (trig) > 8 GeV/c, andlook at associated hadron in different pT(assoc) class.
• Away side peak at highest pT (assoc) >6 GeV/c.
• Punch through jets at high pT• Away side yield: suppressed byfactor ~5, compared to d+Au.
• B-to-B, but tangentially emission.
• h-h correlations: strong bias
towards surface.
pT (trig) > 8 GeV/chadron(assoc)

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

hadron(trig)4Full	  jet	  reconstruc/on,	  and	  	  h-­‐jet	  correla/ons	  at	  RHIC	
Key to understand jet in HI collisions:(1) correlations, (2) fully reconstructed jet.

• Used fully reconstructed jet (by STAR TPC & EMC).
• Trigger high pT hadron, and look at recoil jet in away side, measureconditional yield in (Au+Au / p+p).
• Stronger suppression for lower recoil jet energy.
• indicating broadening of recoil jet cone size.
• “Controlled” surface bias.
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

5

RHIC	  vs.	  LHC	RHIC	

LHC	√sNN	  (GeV)	

200	5500	T/Tc	

1.9	

3.5-­‐4.0	

ε	  (GeV/fm3)	

5	15-­‐60	

τ	  QGP	  (fm/c)	

2-­‐4	>	  10	RHIC

• LHC:	  Jet	  produc/on	  dominant.	  
– Study	  the	  maVer	  by	  clean	  many	  hard	  probes,	  and	  look	  at	  response	  of	  bulk	  maVer	  in	  HI	  collisions.	  
LHC:	  Inclusive	  jets	  (R=0.4),	  annual	  yield;	  104	  @	  	  pT	  =	  200	  GeV/c	  (5.5	  TeV,	  Year-­‐1)
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

JPS 2010, Sep. 13, T. Chujo

ALICE	  experiment	  	  	  	  	  	  	  	  	  ALICE	  =	  A	  Large	  Ion	  Collider	  Experiment	  •Dedicated	  heavy	  ion	  experiment	  at	  LHC:	  	  ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

7Key	  detectors	  for	  jet	  measurement	  in	  ALICE	
•••TPC	  (+ITS)	  – Charged	  par/cles	  Δη	  =	  1.8.	  
– Excellent	  momentum	  resoluWon.	  
– Excellent	  PID	  and	  heavy	  ﬂavor	  tagging.	  
EMCal	  – Pb-­‐Scint	  sampling	  EMC.	  
– Δφ	  =	  107°,	  Δη	  =	  1.4	  – Energy	  resolu/on	  ~10%/√Eγ	– Jet	  and	  γ	  trigger	  PHOS	  – PWO	  crystal	  EMC.	  
– 220°	  <	  φ	  <	  320°,	  Δη	  =	  0.24	  – Energy	  resolu/on	  ~3%//√Eγ	

– γ trigger.	  

TPC

EMCal
PHOS

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

8Di-­‐Jet	  event	  @	  7	  TeV	  p+p	  (real	  data);	  used	  only	  charged	  tracks	  (ITS-­‐TPC)	

η-φ

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

9But,	  don’t	  forget	  the	  ﬂuctua/on	  by	  neutral!	  
Charged(2/3)~15@100Gev

EJET
Neutral(1/3)~7@100Gev

EJET=ECHARGED+ENEUTRAL
dECHARGED = -dENEUTRAL• Statistical fluctuation with total energy limitation– Total jet energy is fixed.
• fluctuation of neutral play significant role
• Need larger acceptance EMC on opposite side ofEMCal in ALICE.
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

10ALICE	  Dijet	  Calorimeter	  (DCal)	
•Extension of the acceptance ofEMCal .

•Lead-scintillator sampling type EMC
with APD readout.
– EMCal: Δφ = 110°
– DCal: Δφ = 60° (on opposite sideof EMCal)– Δη = 0.7 for both EMCal and DCal+ PHOS– ~10%/√E•
DCal

Allow back-to-back hadron-jet, di-jet
measurements in ALICE, with R =0.4, up to pT ~ 150 GeV/c.

PHOS

•

Enhance jet, γ trigger capability.

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

11DCal – 6 supermodules

Δη~0.74
32PHOS – 5 modulesshown
6 Super Module configuration was chosen to have alargest possible jet radii in DCal, together with PHOS,i.e. R=0.4
Workshop for ALICE upgrades by Asian countries, Yonsei Univ. Seoul, Nov. 6, 2009 (T. Chujo)

12ChinaHuazhong Normal UniversityFinland
University of Jyvaskyla
FranceLPSC Grenoble, Subatech Nantes, IPHC Strasbourg
Italy
INFN Catania, LNF Frascati,
Japan
Hiroshima University, University of Tokyo, University of Tsukuba,
Switzerland
CERN
USA
Lawrence Berkeley National Laboratory, Wayne State University, University ofHouston, University of Tennessee, Lawrence Livermore National Laboratory,
Yale University, Oak Ridge National Laboratory, Creighton University, Cal PolySan Luis Obispo, Purdue University
Workshop for ALICE upgrades by Asian countries, Yonsei Univ. Seoul, Nov. 6, 2009 (T. Chujo)

13Physics	  case	  of	  DCal	• Case1:	  Jet-­‐Jet	  in	  p+p	  • Case2:	  Jet-­‐Jet	  in	  Pb+Pb	  (quenching	  eﬀect)	  • Case3:	  π0-­‐Jet	  in	  Pb+Pb	  – Notes:	  • MC	  simulaWon	  study	  using	  qPYTHIA.	  
• “DCal”	  means	  including	  PHOS	  acceptance,	  i.e.	  DCal+PHOS.	  
• Uncertainty	  on	  data	  points:	  Pb+Pb	  (central	  0-­‐10%)	  @	  5.5	  TeV	  one	  year	  running	  staWsWcal	  uncertainty	  (=	  0.5	  nb-­‐1).	  
• Jet	  reconstrucWon:	  FAST	  jet	  anW-­‐kT	  algorithm,	  R=0.4.	
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

14Case1:	  Dijet	  in	  p+p	
Jet (trig)

Jet (assoc)(E TDCal − E TEMCal )Δ = DCal(E T + E TEMCal ) /2

• Dijet energy balance, Δ.
• No quenching (p+p)• True dijet peak Δ~0, except
without DCal.
• No clear peak EMC-TPC (noDCal).
• Asymmetric shape due to recoil
jet escape the acceptance ofDCal, and jet from BG.
•DCal is essential for better Δresolution.

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

15Case1:	  Dijet	  in	  p+p	
Jet (trig)

Jet (assoc)

 DCal improves the energy balance
resolution from ~35% to ~25% @ETEMCal = 60 GeV, down to <20% forhigher ETEMCal.

 Small effect by gap between PHOS
and DCal.

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

16Case2:	  Dijet	  in	  Pb+Pb,	  quenched	  jet	
Jet (assoc)

Jet (trig)•••(E TDCal − E TEMCal )Δ = DCal(E T + E TEMCal ) /2

•Same	  as	  “Case1”	  but,	  required	  trigger	  jet	  in	  DCal	  side	  instead.	  
“Tail”	  on	  posiWve	  side	  due	  to	  trigger	  for	  DCal	  in	  this	  case.	  
In	  this	  case,	  <qhat>	  =	  50	  GeV2/fm,	  and	  	  DCal	  jet	  energy	  threshold	  of	  100	  GeV.	  	  Peak:	  true	  dijet	  with	  quencing.	  
–•look	  at	  sigma,	  and	  centroid	  to	  quanWfy	  the	  jet	  quenching	  eﬀect	  (see	  next	  slide).	  

Tail:	  recoil	  jet	  out	  of	  acceptance,	  BG.	  

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)17Case2:	  Dijet	  in	  Pb+Pb,	  quenched	  jet	WidthCentroid

Jet (assoc)

Jet (trig)

150 GeV

150 GeV• Red:	  <qhat>	  =	  50	  GeV2/fm,	  Black:	  <qhat>	  =	  0	  GeV2/fm.	  
• Broadening	  of	  peak	  is	  seen	  for	  jet	  quenching.	  
• Shiq	  of	  centroid	  -­‐>	  energy	  loss.	  
• Using	  one	  year	  Pb+Pb	  running	  (in	  this	  model	  &	  parameter	  set),	  possible	  to	  study	  jet	  	  	  quenching	  eﬀect	  up	  to	  ETDCal	  ~	  150	  GeV.	
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

18

Case	  3:	  π0-­‐jet,	  control	  path	  length	Geometry of π0 trigger and associated recoil jet

Jet (assoc)

π0 (trig)• Trigger	  π0	  in	  DCal,	  requiring	  jet	  in	  EMCal.	  
• Producing	  strong	  geometry	  bias	  by	  hand,	  i.e.	  “control”	  the	  path	  length	  of	  jet.	
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

19Case	  3:	  π0-­‐jet,	  control	  path	  length	Jet (assoc)

π0 (trig)• Hard scattering point (in x-y plane)of trigger π0 with associate recoil jet.
• The higher ET π0, the stronger
surface bias.
• <qhat> = 20 & 50 GeV2/fm• small difference.
 can be used as geometry
measure of emission point, without
knowing the quench parameters.
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

20Case	  3:	  π0-­‐jet,	  control	  path	  length	Jet (assoc)

Recoil jet (EMC)

Trig π0 (DCal)

π0 (trig)

Path Length [fm]••••Path Length [fm]Trigger	  π0	  (right):	  Minimizing	  path	  length.	  
Recoil	  jet	  (len):	  Maximizing	  path	  length.	  
Path	  length	  	  of	  jet	  medium,	  “control”	  experiment.	  
Eﬃcient	  trigger	  of	  π0	  (Level	  1)	  is	  the	  key,	  and	  it	  is	  capable	  by	  uWlizing	  exisWng	  level	  1	  21readout	  for	  EMC.	
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)Other	  interes/ng	  measurements	  with	  DCal	• γ-­‐jet:	  – Golden	  channel	  !!	  
– Complementally	  to	  h	  (π0)	  -­‐jet,	  jet-­‐jet.	  
• Ridge	  study	  with	  di-­‐jet	  &	  π0	  -­‐	  jet	  	  • Reac/on	  plane	  dependence	  of:	  – di-­‐jet	  energy	  balance	  – π0-­‐jet	  • Discrimina/on	  of	  quark	  jet,	  gluon	  jet	  – Study	  of	  energy	  loss	  mechanism.	  
– MulWplicity	  and	  other	  observables	  can	  be	  used.	  

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

22

Current	  status	  and	  schedule	• DCal	  has	  been	  approved	  by	  the	  ALICE	  collaboraWon,	  Oct.	  2009.	  
• Finished	  parts	  order.	  Now	  (almost)	  all	  parts	  have	  been	  delivered.	  
• Module	  produc/on	  starts	  in	  Oct.	  2010,	  and	  will	  con/nue	  un/l	  early	  next	  year.	  
– 3.0	  SM	  from	  Wayne	  State	  Univ.	  (USA)	  – 1.5	  SM	  from	  Tsukuba	  (Japan)	  – 1.0	  SM	  from	  	  Wuhan	  (China)	  – 0.5	  SM	  from	  Nantes	  (France)	  • Total:	  6	  SM	  (192	  x	  6	  =	  1152	  modules)	  for	  DCal.	  
• Integrated	  SM	  in	  Nantes,	  Grenoble.	  	  • Installed	  in	  the	  ALICE	  experimental	  area	  during	  the	  long	  LHC	  shutdown	  in	  2011-­‐2012.	  
• Ready	  to	  take	  the	  ﬁrst	  5.5	  TeV	  Pb+Pb	  run,	  expected	  in	  2012-­‐2013.	  

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

23

Assembly	  of	  1st	  DCal	  module	  in	  Tsukuba	  (Oct.	  18,	  2010)	

Pb + scint.
(77 layers)

Assembly station(from WSU)
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

24

(almost)	  all	  parts	  in	  hands,	  ready	  to	  start	  produc/on	  !	

S. Kubota
Lab. at Univ. of Tsukuba (Oct. 18, 2010)

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

R. Funato25

Wuhan	  team	  is	  ready.	

two module assembly stations
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

26Summary	•Dijet Electromagnetic Calorimeter (DCal) in ALICE experiment
provide a powerful & unique tool to investigate hot and dense matterin HI collisions at LHC, through dijet and π0-jet measurements.
1. Di-Jet correlations:• Energy balance of jet.
2. π0-Jet correlations:• Control path length of jet.

••

DCal has an essential role to make these measurements.
Together with other measurements (e.g. γ-jet, reaction plane dep.),
one may obtain a complete understanding of jet quenchingmechanism at LHC energy, i.e. “jet tomography”.

•

DCal will be installed in the next LHC long shutdown (2011-2012), andwill be ready to take first 5.5 TeV data in 2012-2013.
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

27

BACKUP
ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

28

CDF, PRL94(2005)171802

As a new generation exp., fromParticle ID to Parton ID !

• According to CDF exp.,
charged/neutral works

Might be very difficult in heavy ion
gluon jetenvironment

quark jet

Nevertheless, challenge!
It becomes feasible for higher pt
jetWorkshop for ALICE upgrades by Asian countries, Yonsei Univ. Seoul, Nov. 6, 2009 (T. Chujo)

29

Fig.8.4 of TDR

Backgrounds
Rcone = 0.2
Ejet = 100 GeV50 GeV

With Rcone = 0.2, triggering jet of < 50 GeV

Rcone

becomes difficult.

Back-to backWorkshop for ALICE upgrades by Asian countries, Yonsei Univ. Seoul, Nov. 6, 2009 (T. Chujo)30Case	  3:	  π0-­‐jet,	  control	  path	  length	Jet (assoc)

semi-inclusive jet spectrum(π0-jet)Au+Au/p+p

ATHIC 2010, Wuhan, Oct. 20, 2010 (T. Chujo)

π0 (trig)

31