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Overview of CMS heavy -ion results. Raphaël Granier de Cassagnac for the CMS collaboration LLR – École polytechnique / IN2P3 ERC grant “ QuarkGluonPlasmaCMS ” LHC days , October 2 nd 2012, Split. A wealth of results. Affordable in a 20’ talk?.

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Overview of cms heavy ion results

Overview of CMS heavy-ion results

Raphaël Granier de Cassagnac

for the CMS collaboration

LLR – École polytechnique / IN2P3

ERC grant “QuarkGluonPlasmaCMS”

LHC days, October 2nd2012, Split


A wealth of results
A wealth of results

Affordable

in a 20’ talk?

[email protected] - Heavy ions in CMS - Split

  • Multiplicity and transverse energy

    • dNch/dη ≈ 1600 and dET/dη ≈ 2 TeV !

  • Particle correlations

    • Elliptic flow (incl. π0) and higher harmonics

    • Di-hadron correlations (the “ridge”)

  • Candles: Electro+weak bosons

    • Z and W bosons

    • Isolated photons

  • Jet quenching

    • Photon+Jet

    • Fully reconstructed jets

    • Jet fragmentation & shape

  • Quarkoniumsuppression

    • Five states disappearing


A wealth of results1
A wealth of results

All results available at

https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIN

Or google search “CMS heavy ions”

18 submitted PbPb papers (as many as ALICE)

+ 10 documented preliminary analysis (PAS)

Affordable

in a 20’ talk?

[email protected] - Heavy ions in CMS - Split

  • Multiplicity and transverse energy

    • dNch/dη ≈ 1600 and dET/dη ≈ 2 TeV !

  • Particle correlations

    • Elliptic flow and higher harmonics

    • Di-hadron correlations (the “ridge”)

  • Candles: Electro+weak bosons

    • Z and W bosons

    • Isolated photons

  • Jet quenching

    • Photon+Jet

    • Fully reconstructed jets

    • Jet fragmentation & shape

  • Quarkoniumsuppression

    • Five states disappearing


Particule detection 2 4
Particule detection |η|<2.4

Muons 1-2% resolution

up to 100 GeV/c

Photons 10% resolution

in central events at 20 GeV

EMCal

PbWO4 |η|<3

Muon: drift tubes + RPC |η|<2.4

Silicium: pixels (3)

and strips (10) |η|<2.4

HCal: Scintillators

|η|<5

+ high rapidity extension

[email protected] - Heavy ions in CMS - Split


Pb pb collision
Pb-Pbcollision

[email protected] - Heavy ions in CMS - Split


From the key concept centrality
From the key concept: centrality…

[email protected] - Heavy ions in CMS - Split

  • Collision centrality related to energy deposit in (forward) calorimeters

  • Then to geometrical quantities:

    • Ncoll = number of elementary NN collisions

    • or TAA = Ncoll / σpp

  • Hard probes are supposed to scale with Ncoll, in the absence of medium effect, RAA = 1


To the nuclear modification factor r aa
… to the nuclear modification factor RAA

dNAA

dNAA

RAA= =

dNPP

x

Ncoll

dσPP

x

TAA

[email protected] - Heavy ions in CMS - Split

  • Collision centrality related to energy deposit in (forward) calorimeters

  • Then to geometrical quantities:

    • Ncoll = number of elementary NN collisions

    • or TAA = Ncoll / σpp

  • Hard probes are supposed to scale with Ncoll, in the absence of medium effect, RAA = 1


Pbpb collisions @ s nn 2 76 tev
PbPb collisions @ √sNN = 2.76 TeV

Dec. 2011: ≈ 150 μb–1PbPb

x 20

Dec. 2010: ≈ 7 μb–1PbPb

  • Binary-scaled

  • equivalent

  •  as many

  • Z, W, photons…

+ Mar. 2011 ≈ 230 [email protected] TeV

[email protected] - Heavy ions in CMS - Split


New candles

Electro+Weak bosons should go through the colored medium without feeling it

New candles

[email protected] - Heavy ions in CMS - Split


Z boson centrality independence 150 b 1
Z boson centrality independence (150 μb–1)

dNAA

RAA =

dσPP

x

TAA

  • Very low pp statistics available at 2.76 TeV

    ≈ 20 times less Z than PbPb

[email protected] - Heavy ions in CMS - Split


Z boson centrality independence 150 b 11
Z boson centrality independence (150 μb–1)

  • (PRL 106 (2011) 212301)

  • CMS-PAS-HIN-12-008

  • Very low pp statistics available at 2.76 TeV

    ≈ 20 times less Z than PbPb

dNAA / TAA = dσppx RAA

[email protected] - Heavy ions in CMS - Split


Z boson centrality independence 150 b 12
Z boson centrality independence (150 μb–1)

  • (PRL 106 (2011) 212301)

  • CMS-PAS-HIN-12-008

  • Very low pp statistics available at 2.76 TeV

    ≈ 20 times less Z than PbPb

  • Compare to POWHEG (NLO generator) instead

    • Well tested at Tevatron (2 TeV) and LHC (7 TeV)

    • 5% uncertainty from NNLO, pdfs, etc.

dNAA / TAA = dσppx RAA

[email protected] - Heavy ions in CMS - Split


Z boson centrality independence 150 b 13
Z boson centrality independence (150 μb–1)

  • (PRL 106 (2011) 212301)

  • CMS-PAS-HIN-12-008

  • Very low pp statistics available at 2.76 TeV

    ≈ 20 times less Z than PbPb

  • Compare to POWHEG (NLO generator) instead

    • Well tested at Tevatron (2 TeV) and LHC (7 TeV)

    • 5% uncertainty from NNLO, pdfs, etc.

dNAA / TAA = dσppx RAA

RAA = 0.95 ± 0.03 ± 0.13

[email protected] - Heavy ions in CMS - Split


W boson centrality independence 7 2 b 1
W boson centrality independence (7.2 μb–1)

dNAA / TAA = dσppx RAA

W

W+

W–

  • PLB 715 (2012) 66

[email protected] - Heavy ions in CMS - Split


W boson centrality independence 7 2 b 11
W boson centrality independence (7.2 μb–1)

dNAA / TAA = dσppx RAA

  • PLB 715 (2012) 66

[email protected] - Heavy ions in CMS - Split


W boson centrality independence 7 2 b 12
W boson centrality independence (7.2 μb–1)

2010 PbPb ≈ pp data

RAA(W) = 1.04 ± 0.07 ± 0.12

RAA(W+) = 0.82 ± 0.07 ± 0.09

RAA(W–) = 1.46 ± 0.14 ± 0.16

Consistent with pure isospin

dNAA / TAA = dσppx RAA

More d quarks in Pb make more W+ than in pp

  • PLB 715 (2012) 66

[email protected] - Heavy ions in CMS - Split


Photon centrality independence 7 2 b 1
Photon centrality independence (7.2 μb–1)

( isolated photons, after large background subtraction )

  • PLB 710 (2012) 256

[email protected] - Heavy ions in CMS - Split


Unmodified electro weak bosons
Unmodified electro+weak bosons

  • Within uncertainties, electro+weak bosons are not modified

    • Confirm the validity of Ncoll scaling

    • More precision may reveal nuclear PDF modifications

    • But let’s first use these calibrated probes…

[email protected] - Heavy ions in CMS - Split



Photon jet 150 b 1
Photon+jet(150 μb–1)

Area normalized to unity

Pythia+Hydjet

Photon-jet momentum balance

arXiv:1205.0206

[email protected] - Heavy ions in CMS - Split


Photon jet 150 b 11
Photon+jet(150 μb–1)

Area normalized to unity

0-10%

PbPb

Pythia+Hydjet

Photon-jet momentum balance

arXiv:1205.0206

[email protected] - Heavy ions in CMS - Split


Photon jet 150 b 12
Photon+jet(150 μb–1)

Pythia+Hydjet

Area normalized to unity

0-10%

Jet-photon

pT balance

14% drop

pp

PbPb

PbPb

Pythia+Hydjet

Pythia+Hydjet

20% lose

jet partner

Photon-jet momentum balance

pp

PbPb

arXiv:1205.0206

[email protected] - Heavy ions in CMS - Split


Modified jet r aa 150 b 1
Modified jet RAA(150 μb–1)

CMS-PAS-HIN-12-004

[email protected] - Heavy ions in CMS - Split


Jet r aa
Jet RAA

Cone size R = 0.3, but does not vary a lot for R = 0.2 or 0.4

CMS-PAS-HIN-12-004

[email protected] - Heavy ions in CMS - Split


Where does the energy go
Wheredoes the energy go?

100 GeV inclusive jet

Anti-kT R=0.3 jet in PYTHIA

95% of jet energy in r < 0.2

95% of jet energy in

pT > 4 GeV particles

PRC 84 (2011) 024906

G. Roland at QM’12

[email protected] - Heavy ions in CMS - Split

  • To large angle & low pT

    • Qualitative idea in the first 2010 (di)jet paper

  • Quantitatively

    • Low pT, fragmentation functions

    • Large angle, jet shape


Jet fragmentation
Jet fragmentation

arXiv:1205.5872 accepted by JHEP

vsCMS-PAS-HIN-12-013

ξ = ln(1/z) & z=pT(track)/pT(jet)

where pT(jet) is quenched already

( < pT(parton) )

ξ

[email protected] - Heavy ions in CMS - Split

At first sight (QM’11, run 1, pT(track) > 4 GeV & pT(jet) > 100 GeV), surviving jets are not modified

Looking closer (QM’12, run 2, pT(track) > 1 GeV & more energetic jets), modifications appear


Jet fragmentation and shapes
Jet fragmentation and shapes

PbPb/pp

distributions

No change at small r, high pT

Narrowing/depletion at intermediate pT

Broadening/excess at large r, low pT

CMS-PAS-HIN-12-013

[email protected] - Heavy ions in CMS - Split


Back to r aa of jets and b jet
Back to RAA of jets(and b-jet)

Note: first b-jet identification

in heavy-ion collisions

CMS-PAS-HIN-12-003

[email protected] - Heavy ions in CMS - Split


Back to r aa of jets and hadrons
Back to RAA of jets, and hadrons

Jets: CMS-PAS-HIN-12-004

Hadrons: EPJC 72 (2012) 1945

G. Roland at QM’12

Looking at the same

partonpT range

PbPb fragmentation function = pp for ξ <1

Charged particles with

pT= 50-100 GeV/c

z = pT(track)/pT(jet) = 0.4-0.6

x < 1

[email protected] - Heavy ions in CMS - Split



Quarkonium suppression
Quarkonium suppression

Matsui & Satz,

PLB168 (1986) 415

  • Old predicted signature of the QGP

    • Quarkonia should melt one after the other, depending on their binding energy

    • Recent example of melting temperatures 

  • @ SPS / RHIC, no / marginal access to the (yet unresolved) Upsilon family

  • @ SPS, J/ψ and ψ’ studied in detail

  • @ RHIC, J/ψ brought up surprises…

    • Though they are suppressed, the balance of various effects is not clear…

ϒ(1S)

χb

J/ψ, ϒ(2S)

χc, χ’b, ψ',

ϒ(3S)

Mocsy, EPJC61 (2009) 705

BNL workshop in June

[email protected] - Heavy ions in CMS - Split


Prompt j suppression
Prompt J/ψ suppression

centrality

  • CMS J/ψpT > 6.5 GeV/c

    • Material and B-field

    • Feed down from B  J/ψ is subtracted

  • More suppression than at RHIC

    • CMS < STAR (pT > 5 GeV/c)

  • More suppression than at low pT

    • CMS<ALICE (all pT)

  • Popular explanation: regeneration from uncorrelated and

    • Stronger at low pT

      > 100 pairs in a central event

JHEP05 (2012) 176 & CMS-HIN-PAS-12-014

[email protected] - Heavy ions in CMS - Split


Prompt j suppression1
Prompt J/ψ suppression

centrality

  • CMS J/ψpT > 6.5 GeV/c

    • Material and B-field

    • Feed down from B  J/ψ is subtracted

  • More suppression than at RHIC (at high pT)

    • CMS < STAR (pT > 5 GeV/c)

  • Less suppression at low pT

    • CMS<ALICE (inclusive, all pT)

  • Popular explanation: regeneration from uncorrelated and

    • Stronger at low pT

      > 100 pairs in a central event

JHEP05 (2012) 176 & CMS-HIN-PAS-12-014

[email protected] - Heavy ions in CMS - Split


First look at 2s
First look at ψ(2S)

CMS-PAS-HIN-12-007

[email protected] - Heavy ions in CMS - Split

  • Relatively less ψ(2S) than J/ψ, as expected

    @ midrapidity|y|< 1.6, thus high pT > 6.5 GeV

  • (a hint of an opposite behaviour at lower pT, but less than 2σ)


Upsilon 1s 2s and 3s
Upsilon (1S), (2S) and (3S)

(PRL107 (2011) 052302)

arXiv:1208.2826

[email protected] - Heavy ions in CMS - Split


Upsilons 1s 2s and 3s
Upsilons (1S), (2S) and (3S)

Upsilon(1S) and (2S) at LHC

Sequential disappearance

of the 3 states

For minimum bias

RAA (Y(1S)) = 0.56 ± 0.08 ± 0.07

RAA (Y(2S)) = 0.12 ± 0.04 ± 0.02

RAA (Y(3S)) < 0.10 @ 95% CL

(Remember a large part of Y(2S)

comes from higher state decays,

in particular the χb)

(PRL107 (2011) 052302)

arXiv:1208.2826

[email protected] - Heavy ions in CMS - Split


Five states to bind them all
Five states to bind them all

Forgetting low pT J/ψ

(regeneration)

for a while…

RAA(MB) vs binding energy

looks ordered…

TBD with more data vs

centrality and unfolding

cold effects (pA) & feeddown

could start acting as a

thermometer?

Mironov at QM’12

[email protected] - Heavy ions in CMS - Split


To conclude
To conclude

1/ Being interpreted in

terms of Quark-Gluon

Plasma properties…

2/ Once we have checked

what happens in pPb

(2013…)

[email protected] - Heavy ions in CMS - Split

Three unmodified control probes (photon, Z and W)

Detailed studies of jet quenching

Five quarkoniumsuppressions

And more!



W boson production
W boson production

@ LO : &

Less W+ and more W– in PbPb than in pp (isospin effect)

  • Cancels for W+ + W–

  • W boosted towards the valence quark (higher rapidity)

  • Spin conservation μ+ (μ–) boosted back to (awayfrom) midrapidity

  • Different muon rapidity distributions (not heavy-ion specific) between W+ and W–

  • ud

    p

    p

    W+

    μ+

    ν

    [email protected] - Heavy ions in CMS - Split


    Muon charge asymmetry
    Muon charge asymmetry

    N+ – N–

    N+ + N–

    |ημ|

    • PLB 715 (2012) 66

    [email protected] - Heavy ions in CMS - Split

    Less up quarks make less W+ in PbPb than in pp

    Isospin effect bringing down asymmetry by 0.2 to 0.4

    (EPS09 modifications are 0.03 at most)


    How to find photons
    How to find photons?

    Δϕ

    • Trigger on ECAL clusters

      • Uncorrected ET > 15 GeV, fully efficient for ET > 20 GeV

    • Subtract underlying event

      • From same pseudorapidity strip, event by event

    • Look for isolated cluster

      • Remove photons from bremsstrahlung and jet fragmentation…

    • Look at shower shape in the highly segmented ECAL

      • Further remove isolated π0, η

    Δη

    photon-like

    π,η 2γ

    [email protected] - Heavy ions in CMS - Split


    Photon spectrum 2010
    Photon spectrum (2010)

    • PLB 710 (2012) 256

    Consistent with JETPHOX

    With unmodified pdf (CT10)

    [email protected] - Heavy ions in CMS - Split


    Unmodified photons
    Unmodified photons

    • PLB 710 (2012) 256

    • Normalised by pp!

    • Consistent with unity!

    • Uncertainties still

    • larger than modified

    • pdf uncertainties…

    [email protected] - Heavy ions in CMS - Split


    Jet reconstruction performances
    Jet reconstruction performances

    Resolution

    Responce

    [email protected] - Heavy ions in CMS - Split





    M odified hadrons 150 b 1
    Modified hadrons (150 μb–1)

    EPJC 72 (2012) 1945

    [email protected] - Heavy ions in CMS - Split


    B jet
    b-jet

    [email protected] - Heavy ions in CMS - Split


    J at rhic all p t
    J/ψat RHIC (all pT)

    • Two surprises:

      • At midrapidity, same suppression at RHIC and at SPS, while density must be higher

      • More suppression at forward rapidity at RHIC, while density must be lower

    • Two popular answers:

      • Cold: shadowing / saturation brings forward yields down

      • Hot: recombination of uncorrelated cc brings midrapidity yield up

    PHENIX, PRL98 (2007) 232301, also 1103.6269

    SPS from Scomparin @ QM06

    [email protected] - Heavy ions in CMS - Split


    J at rhic all p t1
    J/ψat RHIC (all pT)

    • Two surprises:

      • At midrapidity, same suppression at RHIC and at SPS, while density must be higher

      • More suppression at forward rapidityat RHIC, while density must be lower

    • Two popular answers:

      • Cold: shadowing / saturation brings forward yields down

      • Hot: recombination of uncorrelated cc brings midrapidityyield up

    PHENIX, PRL98 (2007) 232301, also 1103.6269

    SPS from Scomparin @ QM06

    [email protected] - Heavy ions in CMS - Split


    First look at 2s1
    First look at ψ(2S)

    CMS-PAS-HIN-12-007

    [email protected] - Heavy ions in CMS - Split

    More forward 1.6 < |y| < 2.4, down to pT = 3 GeV

    Relatively more ψ(2S) than J/ψ?


    Pbpb pp
    (ψ’/ψ)PbPb/ (ψ’/ψ)pp

    CMS-PAS-HIN-12-007

    HIN-12-007

    Heavy Ions in CMS - [email protected]

    ψ(2S) more suppressedthanJ/ψ@ high pT

    ψ(2S) lesssuppressedthanJ/ψ@ lowpT? (<2σ)


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