wwnd10 jamaica salur finalSevil&Salur& 6 E. Bruna%[STARCollabora=on],% QuarkMaVer%2009% Jet (GeV/c)...

31
Jets at RHIC Sevil Salur UC Davis & Rutgers U. η φ

Transcript of wwnd10 jamaica salur finalSevil&Salur& 6 E. Bruna%[STARCollabora=on],% QuarkMaVer%2009% Jet (GeV/c)...

Page 1: wwnd10 jamaica salur finalSevil&Salur& 6 E. Bruna%[STARCollabora=on],% QuarkMaVer%2009% Jet (GeV/c) T p 0 10 20 30 40 50 60-1) (GeV/c)d d T dN/(dp event 1/N 10-9 10-8 10-7 10-6 10-5

Jets  at  RHIC    

Sevil  Salur  UC  Davis  &  Rutgers  U.  

η φ

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Sevil  Salur   2  

Why  we  should  study  jets  in  heavy  ion  collisions?  

But  are  we  succeeding?    

Goal  is  Unbiased  Jet  Reconstruc=on:    

Reconstruct  partonic  kinema=cs  independent  of  fragmenta=on  details  -­‐  quenched  or  unquenched  and  study  the  QGP  dynamics.  

Full  Jet  Reconstruc=on:  Enables  study  of  jet  quenching  at  the  partonic  level.    

•   Uniquely  large  kinema=c  reach  

•   In  A+A  much  reduced  geometric  biases,  full  explora=on  of  quenching.    

•   Mul=ple  channels  for  consistency  checks:    Inclusive,  di-­‐jets,  h-­‐jets,  gamma-­‐jets    

•   Qualita=vely  new  observables:  energy  flow,  jet  substructure,  fragmenta=on  func=on  

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Sevil  Salur   3  WWND 08 South Padre -TX

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dNJet/dE

T  (pe

r  even

t)   Nbin  scaled  p+p  

STAR  Prelim

inary  

 MB-­‐Trig  O  HT-­‐Trig  

R=0.4  pT  cut  =1  GeV  Seed=4.6  GeV  

LOHSC  

S.  Salur  [STAR  Collabora=on],  Hard  Probes  2008  

p+p:  Phys.  Rev.  Lec.  97  (2006)  252001  

Sevil  Salur   4  

J.  Putschke  [STAR  Collabora=on],  Hard  Probes  2008  

Hard  Probes  2008    

Agreement  with  Nbin  scaled  p+p    

Resolu=on  effect  corrected  assuming  Pythia  Fragmenta=on.  

Trigger  Biases  due  to  event  recording  

Ra=o  of  A+A  to  pp  in  FF~1.    

Tower  energy  threshold  bias  No  modifica=on  in  FF…  

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Sevil  Salur   5  WWND 09 Big Sky - MT

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Sevil  Salur   6  

E.  Bruna  [STAR  Collabora=on],  Quark  MaVer  2009  

(GeV/c)JetT

p0 10 20 30 40 50 60

-1) (

GeV/

c) d T

dN/(d

pev

ent

1/N

-910

-810

-710

-610

-510

-410

-310

kt R=0.4

anti-kt R=0.4

kt R=0.2

anti-kt R=0.2

STAR Preliminary

=200 GeV/cNNsAu+Au at 10% most central events

M.  Ploskon  [STAR  Collabora=on],  Quark  MaVer  2009  

Quark  MaVer  2009  

Correct  via  unfolding:  

Exactly  the  same  algorithms  and  jet  defini=ons  used  as  in          p+p  collisions  

Remove  the  trigger  bias:  

Apparent  suppression  of        the  recoil  jet  of  Au+Au  with  respect  to  p+p.  

“recoil”     “trigger”  

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dNJet/dE

T  (pe

r  even

t)   Nbin  scaled  p+p  

STAR  Prelim

inary  

 MB-­‐Trig  O  HT-­‐Trig  

R=0.4  pT  cut  =1  GeV  Seed=4.6  GeV  

LOHSC  

S.  Salur  [STAR  Collabora=on],  Hard  Probes  2008  

p+p:  Phys.  Rev.  Lec.  97  (2006)  252001  

Sevil  Salur   7  

E.  Bruna  [STAR  Collabora=on],  Quark  MaVer  2009  

J.  Putschke  [STAR  Collabora=on],  Hard  Probes  2008  

(GeV/c)JetT

p0 10 20 30 40 50 60

-1) (

GeV/

c) d T

dN/(d

pev

ent

1/N

-910

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kt R=0.4

anti-kt R=0.4

kt R=0.2

anti-kt R=0.2

STAR Preliminary

=200 GeV/cNNsAu+Au at 10% most central events

M.  Ploskon  [STAR  Collabora=on],  Quark  MaVer  2009  

Y.  S.  Lai  [PHENIX  Collabora=on]  Quark  MaVer  2009  

PHENIX  can  reconstruct  jets!  Large  pT  range  within  restricted  PHENIX  acceptance!        

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dNJet/dE

T  (pe

r  even

t)   Nbin  scaled  p+p  

STAR  Prelim

inary  

 MB-­‐Trig  O  HT-­‐Trig  

R=0.4  pT  cut  =1  GeV  Seed=4.6  GeV  

LOHSC  

S.  Salur  [STAR  Collabora=on],  Hard  Probes  2008  

p+p:  Phys.  Rev.  Lec.  97  (2006)  252001  

Sevil  Salur   8  

E.  Bruna  [STAR  Collabora=on],  Quark  MaVer  2009  

J.  Putschke  [STAR  Collabora=on],  Hard  Probes  2008  

(GeV/c)JetT

p0 10 20 30 40 50 60

-1) (

GeV/

c) d T

dN/(d

pev

ent

1/N

-910

-810

-710

-610

-510

-410

-310

kt R=0.4

anti-kt R=0.4

kt R=0.2

anti-kt R=0.2

STAR Preliminary

=200 GeV/cNNsAu+Au at 10% most central events

M.  Ploskon  [STAR  Collabora=on],  Quark  MaVer  2009  

Y.  S.  Lai  [PHENIX  Collabora=on]  Quark  MaVer  2009  

Story  is  not  over  yet.    Experimental  &  Theore=cal  improvements    

IN  PROGRESS!  

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Reconstructed  Jets  at  RHIC:        What  to  do  next?    

Sevil  Salur  UC  Davis  &  Rutgers  U.  

η φ

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Experimental  Challenges    

1)  Data  taking  -­‐  Trigger-­‐bias      

   -­‐  Biased  fragmenta=on  func=ons  

2)  Par=cle  and  jet  level  correc=ons    

Calorimeter  calibra=on  

   -­‐  ~5%  uncertainty  on  calibra=on  translates  to  a  larger  uncertainty.  

Double  coun=ng  of  par=cle  energies:  

-­‐      electrons:  Include  energy  only  once!  

 -­‐    hadrons:  showering  correc=ons          such  as  MIP,  constant  E-­‐frac=on  

High  momentum  tracking  

   -­‐  Do  not  include  cosmics  

Unobserved  energy  

   -­‐    Energy  shio  (protons  for  neutrons)  

Jet  PT  resolu=on    

Sevil  Salur   10  

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Cone  Algorithm   kT  Algorithm    

hcp://www-­‐cdf.fnal.gov/physics/new/qcd/QCD.html  

11  Sevil  Salur  

Jet  Reconstruc=on  is  not  a  new  phenomena…  

Guidance  from  earlier  measurements  …  

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Cone  Algorithm   kT  Algorithm    

hcp://www-­‐cdf.fnal.gov/physics/new/qcd/QCD.html  

12  Sevil  Salur  

Jet  Reconstruc=on  is  not  a  new  phenomena…  

A.  Bhap  et.  al.  Nucl.Instrum.Meth.A566:375-­‐412  (2006)  

Frac=onal  energy  loss  vs  momentum  MC  comparisons…      

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Experimental  Challenges    

1)      Data  taking  -­‐  Trigger-­‐bias      

   -­‐  Biased  fragmenta=on  func=ons    

2)  Jet  Level  and  Par=cle  Correc=ons  High  momentum  tracking  

   -­‐  Including  cosmics  

Calorimeter  calibra=on  

   -­‐  ~5%  uncertainty  on  calibra=on  translates  to  large  uncertainty  in  cross-­‐sec=ons.  

Double  coun=ng  of  par=cle  energies:  

-­‐      electrons:  Include  energy  only  once!  

 -­‐    hadrons:  showering  correc=ons  

       such  as  MIP,  constant  E-­‐frac=on  

Unobserved  energy:  

   -­‐    Energy  shio  (protons  for  neutrons)  

Jet  PT  resolu=on    

Sevil  Salur   13  

Fundamental  Assump=on:  Two  separable  components:  signal  and  background.  

How  might  it  be  violated?  Biases  in  background  es=ma=on  due  to  presence  of  a  jet.  

a)  Ini=al  state  radia=on  (Expected  to  be  small  compared  to  jet  energy).    b)  Final  state  “out-­‐of-­‐cone”  radia=on.  

3)    Heavy–Ion  Background  

Some  others  like  Fake  Jets…  

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Various  Jet  Reconstruc=on  Algorithms  

Cone  jet  An=-­‐kT  jet  

KT  jet  

Jet

outgoing parton

Fragmentation process

Hard scatter

1.  Mid  Point  Cone:  Merging  &  Splipng  2.  SIS  CONE    

•  Insensitive to “soft” radiation •  Splitting doesn’t change jets  

3.  Leading  Order  High  Seed  Cone  (LOHSC)    

4.  KT  (star=ng  point:  low  pT  par=cles)  5.  An=-­‐KT  (star=ng  point:  high  pT  par=cles)  

Cone Algorithm:    

Sequen=al  recombina=on:  Cluster  pairs  of  objects  close  in  rela=ve  pT  

14  Sevil  Salur  

6.  Gaussian  filtering.  Y.  Lai,  B.  Cole  arXiv:0806.1499    

Different  Algorithms  respond  differently  to  background!    

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The  FastJet  Algorithms  

Suite  of  modern  Collinear  and  infrared  safe  jet  algorithms  •   sequen=al  recombina=on:  kT,  Cambridge/Aachen,  an=-­‐kT  •   cone:  SISCone  (Seedless  Infrared-­‐safe  Cone)  

Mo=vated  by  high  precision  jets  in  high  luminosity  p+p  at  LHC  (pileup)  •   but  directly  applicable  to  heavy  ion  collisions  

Two  important  algorithmic  advances:  1.   Large  improvements  to  processing  =me  vs.  event  mul=plicity  2.   Rigorous  defini=on  of  jet  area  for  subtrac=on  of  diffuse  event  background  

M.  Cacciari,  G.  Salam  0707.1378  [hep-­‐ph]  

M.  Cacciari,  G.  Salam,  G.  Soyez    0802.1188  [hep-­‐ph]  FastJet  –  hcp://www.lpthe.jussieu.fr/~salam/fastjet  

pT  (Jet  Measured)  ~  pT(Parton)  +  ρ  ×  A(Jet)  ±  σ√A(Jet)  

15  Sevil  Salur  

A,  ρ,  σ  are  all  measurable  quan==es!  

A= Jet Area ρ = Diffuse noise, σ=noise fluctuations

Assume:  Signal  and  background  can  be  separated  

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Sevil  Salur   16  

Jet  Measurements  

1)  Minimize  the  kinema=c  cuts.  2)  Data  driven  correc=ons  :  

a.  Experimental  characteriza=on  of  background  fluctua=ons.    b.  Detailed  unfolding  of  fluctua=ons  &  energy  resolu=on.    Correc=ng  for  pT  smearing  

Correc=on  depends  highly  on  the  background  model.      

LOHSC  

seed=4.6  GeV  R=0.4  

PyDet  PyEmbed  PyTrue  

ET  [GeV]  

dNJet/dE

T  (a.u.)  

STAR  Preliminary  

S.  Salur  [STAR  Collabora=on],  arXiv:0809.1609  [nucl-­‐ex]  

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Sevil  Salur   17  

(GeV/c)JetT

p0 10 20 30 40 50 60

-1) (

GeV

/c)

d T d

N/(d

pev

ent

1/N

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-810

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STAR Preliminary

=200 GeV/cNNsAu+Au at 10% most central events

kt R=0.4

anti-kt R=0.4

(GeV/c)JetT

p

0 10 20 30 40 50 60)

-1) (

pb (G

eV/c

)T

dp

/(d2

) d1/

(2

-110

1

10

210

310

410

510

kt R=0.4

anti-kt R=0.4

Published STAR p+p

=200 GeV/cNNsp+p at

STAR Preliminary

Jet  Measurements  

An=-­‐kT  and  kT  jet  spectra  are  consistent.  

Unfolding  uncertainty  corresponds  to  a  factor  of  2  in  jet  cross-­‐sec=on.  

Jet Energy Scale Uncertainty

1  σ  Unfolding  Uncertainty  

Jet Energy Scale Uncertainty

M.  Ploskon  [STAR  Collabora=on],  Quark  MaVer  2009  

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RAA  of  Jets  

(GeV/c)JetT

p10 15 20 25 30 35 40 45 50

Jet

AA

R

-110

1

STAR Preliminary

=200 GeV/cNNsAu+Au and p+p at Au+Au: 10% most central

kt R=0.4

anti-kt R=0.4

R  =  0.4  

A  large  frac=on  of  jets  are  reconstructed!    (Compare  pion  RπAA  =  0.2)      

Sevil  Salur   18  

Jet Energy Scale Uncertainty

We  need  to  constrain  the  approxima=on  of  the  Jet  Energy  Scale  Uncertainty…    

RAA  <  1  :  unable  to  recover  complete  jet  energy  -­‐  jet  broadening  

RAA  =  1  :  recover  complete  jet  energy    

M.  Ploskon  [STAR  Collabora=on],  Quark  MaVer  2009  

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What  happens  at  high  pT?    

Sevil  Salur   19  

W.  Vogelsang  Private  Communica=on  

p+p  

Rela=ve  contribu=ons  of  quark  and  gluon  vary.  

What  about  quenching  dependence  on  parton  species?    

Rela=ve  contribu=on  of  sub-­‐processes  to  inclusive  jet  produc=on  

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What  happens  at  high  pT?    

Sevil  Salur   20  

The  EMC  Effect:  Devia=on  between  structure    Func=ons  of  Au  and  deuterium.    

W.  Vogelsang  Private  Communica=on  

p+p  

Ini=al  state  effects  at  large  x  ~15%  σΑ/σ

d  

What  about  other  high  effects?  

Rela=ve  contribu=on  of  sub-­‐processes  to  inclusive  jet  produc=on  

Rela=ve  contribu=ons  of  quark  and  gluon  vary.  

J.  Gomez  et  al.,  SLAC–PUB–5813  June  7,  2001    D.F.  Geesaman  et  al.,  Ann.  Rev.  Nucl.  Part.  Sci.  45,  337  (1995)  B.  A.  Cole.  et  al,    arXiv:hep-­‐ph/0702101  

SLAC  E139  

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Nicolas  Borghini  arXiv:  0902.2951  Ivan  Vitev  et  al  JHEP  0811:093  (2008),    arXiv:0810.2807  

21  Sevil  Salur  

JEWEL  (Jet  Evolu=on  with  Energy  Loss):  K.  Zapp,  G.  Ingelman,  J.  Rathsman,  J.  Stachel,  U.  A.  Wiedemann    arXiv:0805.4759  Parton  shower  with  microscopic  descrip=on  of  interac=ons  with  medium  –  random  process  of  scacering  is  used  to  modify  the  forma=on  =me  of  the  radiated  gluon.        

Q-­‐Pythia:    N.  Armesto,  L.  Cunqueiro  and  C.  A.  Salgado    arXiv:0809.4433[hep-­‐ph]  MC  implementa=on  in  Pythia  of  medium-­‐induced  gluon  radia=on  through  an  addi=ve  term  in  the  vacuum  splipng  func=ons.  

Analy=c  Calcula=ons:  

Theore=cal  Challenges:  Rigorous  calcula=ons  of  full  jet  variables?    Model  building  of  in-­‐medium  modifica=ons…    

Many  more….  Mar=ni  (S.  Jeon),  PYQUEN  (Lokh=n,  Snigriev),  PQM  (Dainese,  Loizides,  Paic),  HIJING  (Gyulassy,  Wang)…  

YaJEM:  T.  Renk  arXiv:0808.1803  

Ivan  Vitev  DPF  2009  

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RAA  of  Jets  at  RHIC  

Vary  Resolu=on  Parameter    Implica=on  of  broadening  of  jets  

 I.  Vitev  et  al.  arXiv:0910.1090v1  [hep-­‐ph]  

NLO  Calcula=on:  

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RAA  of  Jets  at  RHIC  

Vary  Resolu=on  Parameter    Implica=on  of  broadening  of  jets  

But  before  can  do  this:  constrain  systema=c  uncertain=es  &  jet  energy  resolu=on      

 I.  Vitev  et  al.  arXiv:0910.1090v1  [hep-­‐ph]  

NLO  Calcula=on:  

(GeV/c)JetT

p10 15 20 25 30 35 40 45 50

Jet

AA

R

-110

1

STAR Preliminary

=200 GeV/cNNsAu+Au and p+p at Au+Au: 10% most central

kt R=0.4

anti-kt R=0.4

R  =  0.4  

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(GeV/c)Jet

Tp

15 20 25 30 35 40 45 50

Yie

ld R

ati

o:

R=

0.2

/R=

0.4

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

STAR Preliminary

=200 GeV/cNN

sAu+Au and p+p at

Au+Au: 10% most central p+p kt

p+p anti-kt

Vary  Resolu=on  Parameter:  R=0.2/R=0.4  

24  

p+p:  “Narrowing”  of  the  jet  structure  with  increasing  jet  energy  

Sevil  Salur  

QM  09  

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(GeV/c)Jet

Tp

15 20 25 30 35 40 45 50

Yie

ld R

ati

o:

R=

0.2

/R=

0.4

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

STAR Preliminary

=200 GeV/cNN

sAu+Au and p+p at

Au+Au: 10% most central p+p kt

p+p anti-kt

Vary  Resolu=on  Parameter:  R=0.2/R=0.4  

25  

p+p:  “Narrowing”  of  the  jet  structure  with  increasing  jet  energy  

Sevil  Salur  

NLO Calculation W. Vogelsang – priv. comm. 2009

Broader  jet  profile  further  inves=ga=on  is  required  

QM  09  

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Vary  Resolu=on  Parameter:  R=0.2/R=0.4  

26  

p+p:  “Narrowing”  of  the  jet  structure  with  increasing  jet  energy  

Sevil  Salur  

QM  09  

Au+Au:  Broadening  of  the  jet  energy  profile  

Suppression  in    Au+Au  collisions  -­‐>  loss  of  jet  yield  for  R=0.2  

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PT  Cut  

KT   KT   KT  

STAR  Prelim

inary  

STAR  Prelim

inary  

STAR  Prelim

inary  

Au+Au  0-­‐10%                

 MB-­‐Trig          Nbin  Scaled  p+p  

Au+Au  0-­‐10%                

 MB-­‐Trig          Nbin  Scaled  p+p  

Au+Au  0-­‐10%                

 MB-­‐Trig          Nbin  Scaled  p+p  

Vary PT Cut : Bias or Physics?

A  good  test  for  quenched  Monte  Carlo’s  and  heavy  ion  background.    

Highly  sensi=ve  to  fragmenta=on  …  

S.  Salur  [STAR  Collabora=on],  arXiv:0810.0500  [nucl-­‐ex]  

27  Sevil  Salur  

STAR  Preliminary  

Au+Au  Central  

η φ

pTcut

R=0.4  

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K.  Zapp,  G.  Ingelman,  J.  Rathsman,  J.  Stachel,  U.  A.  Wiedemann  arXiv:0804.3568  

Significant  uncertain=es  due  to  the  sensi=vity  to  hadronisa=on:  Look  for  new  observables  unaffected  by  the  hadronisa=on.    

Fragmenta=on  func=ons:  Parton  vs  Hadron  

Clear  increase  in  mul=plicity  due  to  radia=ve  energy  loss  

28  Sevil  Salur  

See  talks  of  Elena  Bruna  Ant  Timmins    Yue  Shi  Lai  

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fmed = 3

Ecut = 0 GeV

medium1 jet vacuum2 jets vacuum3 jets vacuum

0.2

0.4

0.6

0.8

1.2

n-jet

frac

tion

0

1

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0log10(resolution scale)

Sevil  Salur   29  

QCD  JET  Observables    

pT  cut  infrared  safe  insensi=ve  observables!  :    number  of  subjets,  thurst  …      

K.  Zapp,  G.  Ingelman,  J.  Rathsman,  J.  Stachel,  U.  A.  Wiedemann  arXiv:0804.3568  

In  vacuum  (LEP)  data  well  understood  in  pQCD    

Medium  Induced  Radia=on    More  Coarser  Jet  Structure    

Cone  jet  An=-­‐kT  jet  

KT  jet  

We  need  to  confront  with  data….  

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• Full  jet  reconstruc=on  at  RHIC  is  possible.  A  new  tool  to  study  partonic  energy  loss…  

• First  studies  indicate  significant  broadening  of  the  jet  energy  profile  due  to  quenching  

•   Experimental  &  Theore=cal  challenges  

•   Consistency  Checks  Mul=ple  channels:    Inclusive,  di-­‐jets,  h-­‐jets,  γ-­‐jets    

•   New  observables:  energy  flow,  jet  substructure…    

LONG  ROAD  AHEAD….  

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Sevil  Salur   31  

• Full  jet  reconstruc=on  at  RHIC  is  possible.  A  new  tool  to  study  partonic  energy  loss…  

• First  studies  indicate  significant  broadening  of  the  jet  energy  profile  due  to  quenching  

•   Experimental  &  Theore=cal  challenges  

•   Consistency  Checks  Mul=ple  channels:    Inclusive,  di-­‐jets,  h-­‐jets,  γ-­‐jets    

•   New  observables:  energy  flow,  jet  substructure…    

LONG  ROAD  AHEAD….  

 …  MORE  TO  COME  SOON!