alice s tatus report 106 th lhcc meeting - open session

ALICE Status Report106th LHCC meeting - Open session

Andrea Rossi, on behalf of the ALICE collaboration

1

ALICE publications in pp collisions

2

• Multiplicity & distributions• 900 GeV; EPJC: Vol. 65 (2010) 111• 900,2.36 TeV; EPJC: Vol. 68 (2010) 89• 7 TeV EPJC: Vol. 68 (2010) 345

• pbar/p ratio (900 GeV & 7 TeV) PRL: Vol. 105 (2010) 072002• Momentum distributions (900 GeV) PLB: Vol. 693 (2010) 53• Bose-Einstein correlations (900 GeV) PRD: Vol. 82 (2010) 052001• Strangeness (K0, , , ,L X W f) at 900 GeV EPJC: Vol: 71, (2011) 1594• Identified charged particle spectra (900 GeV)

• http://arxiv.org/abs/1101.4110 accepted by EPJC• Pion Bose-Einstein correlations at 0.9 and 7 TeV

• http://arxiv.org/abs/1101.3665v1 submitted to Phys. Rev. D• J/Y production at 7 TeV :

• http://arxiv.org/abs/arXiv:1105.0380 submitted to Phys. Lett. B

In this talk, focus on PbPb

results

http://arxiv.org/abs/1101.4110

http://arxiv.org/abs/1101.3665v1

http://arxiv.org/abs/arXiv:1105.0380

QM2011 J. Schukraft 3

ALICE Talks atPlenary:ALICE overview: J. SchukraftGlobal properties: A. ToiaHBT: A. KisielFlow: R. Snellings

RAA: H. Appelshaeuser

Identified Particles: M. Floris

Correlations (IAA): Jan Fiete GO

J/Psi: G. Martinez GarciaHeavy Flavour: A. Dainese

Correlations & FluctuationsElliptic flow: A. BilandzicTriggered dihadrons: A. AdareUntriggered dihadrons: A. TimminsDihadrons pp: Y. MaopT fluctuations: S. HeckelHBT: J. Mercado

HBT K0s pp: T. Humanic

Global & Collective

Nch, centrality: C. Loizides

'strong CP viol': P. Christakoglou

directed flow v1: I. Selyuzhenkov

elliptic flow high pt: A. Dobrin

elliptic flow PID: M. KrzewickiUltra-peripheral: C. OppedisanoDiffraction pp: M. Poghosyan

Heavy FlavourHF m: X. ZhangHF e: S. MasciocchiJ/Y pp: R. ArnaldiJ/ Y Pb: P. Pillot

D mesons RAA: A. Rossi

Identified hadronsPID methods: A. Kalweitp/K/p in pp: M. Chojnackip0,h in pp: K. ReygersResonances: A. PulvirentiL/K0: I. BelikovX, W pp Pb: D. Chinellato

RAA L/K0 : S. Schuchmann

, , r w f pp: A. de Falco

JetsJet reconstruction: C. Klein-Boesing

RAA charged: J. Otwinowski

RAA p0: G. Conesa Balbastre

ExperimentsUpgrades: T. Peitzmanncross section pp: K. Oyama

22-28 May

In this talk: focus on

highlights of PbPb results

2011 runs

4

2.76 TeV pp run statistics

5

System Energy (√sNN) Trigger Integr. Lum.

pp 2.76 Min. Bias* 1.37 nb-1

pp 2.76Muon

SPD high mult.EMCal

20 nb-1

*w/o SDD (0.65 nb-1 w/ SDD)

2.76 TeV pp run: … not only a fundamental reference for PbPb analyses

ongoing 7 TeV pp run now Lint>400 nb-1 with unlike

sign muon pair trigger

- min. bias- single muon trigger

(x10)

~ 71 nb-1

Study of the QGP expanding fireball

6

HIC complex system of strongly interacting matter• Extended size• Local thermodynamical equilibrium

25 years experimental research to answer fundamental questions like:How does the system evolve? How does the collision geometry manifest itself and what can we learn from it?Can we access medium global properties (energy density, temperature, size)?How is particle production modified?How do high energetic partons interact with the medium?

An expanding and cooling fireball

7

A challenging environment!

Particle Identification

8

TPC dE/dx Time Of Flight

ITS

Anti-Matter PID

9

Anti-Hypertriton


10




Triggered Azimuthal Correlations

11

• Triggered correlations: choose a particle from one pT region ("trigger particle") and correlate with particles from another pT region ("associated particles") where pT,assoc < pT,trig in bins of pT,trig and pT,assoc

• Lower pT

• Assess the bulk of the correlations• Dominated by hydrodynamics and flow• Ridge

• Higher pT

• Dominated by jets• Quenching/suppression, broadening

Away-side jet disappears

One of the main highlights

at Quark Matter 2011

Triggered Azimuthal Correlations

12

Clean double Hump (aka 'Mach Cone') appears for ultra-central(without any flow subtraction !)

Full correlation structure described by Fourier Coefficients v1,v2, v3, v4,v5 (for |h|>0.8)v3 very visible, indeed, v3 ≈ v2 for very central

'Mach Cone' & 'Near Side Ridge' shapes evolve smooth with magnitude of v2 and v3

2 Particle correlation C( )DhDf 'Near Side Ridge'

broad away side structurev2v3

Dh > 0.8

v1+v2+v3+v4+v5

Projection on Df for Dh > 0.8

Any function can be described with enough coefficients… can we interpret them?

Anisotropic transverse flow

13

Initial spatial anisotropy

py

py

€

dN

d(ϕ −ψ n )∝1+ 2 vn

n=1

∑ cos(n[ϕ −ψ n ])

Smooth matter distribution in the colliding nuclei

• Yn=YRP

• v2n+1 = 0 by symmetry

€

vn = cos(n[ϕ −ψ n ])

€

ε =y 2 − x 2

y 2 + x 2

€

v2 =py

2 − px2

py2 + px

2(elliptic flow)

Final momentum anisotropyReflected in azimuthal distribution


14


py

py

€

ε =y 2 − x 2

y 2 + x 2

€

v2 =py

2 − px2

py2 + px

2(elliptic flow)


yRP

y2

y3

Smooth matter distribution in the colliding nuclei

• Yn=YRP

• v2n+1 = 0 by symmetry Fluctuations in the matter distribution

→ event by event fluctuation of the plane of symmetry around YRP

→ non negligible odd harmonics

v3,v5,.. magnitude regulated by shear viscosity to entropy density ratio (h/s)

Higher Order Flow v3,v4,..

15

arXiv:1105.3865Accepted by PRL

v2

v3{2} = <cos(3(f1-f2))>

22

22

}4{

}2{

nnn

nnn

vv

vv

v3{4} 4 particle cumulant

v3 relative to reaction & participant planes

v4{2} = <cos(4(f1-f2))>

V3:small dependence on centrality

v3{4} > 0 => not non-flow

v3{4} < v3{2} => geometry fluctuations !

V3{YRP} ≈ 0 => Y3 indep. fluctuations w.r.t. YRP

Flow & Triggered Correlations

16

Any function can be described with enough coefficients- But not if we impose factorization C(pT

trig, pTassoc)=v(pT

trig)*v(pTassoc) (or take coefficients from flow

analysis).

Correlations (|h|>0.8) can be described consistently with 'collective flow' hypothesis

for pT < 3-4 GeV ( consistent with 'collectivity ')

only partially or not at all for pT > 5 GeV

≈ coefficients from flow analysis

coefficients from C(PT1,PT2) analysis

v3 : explain the 'near side long range ridge' and the away side 'Mach cone’ for |h| > 0.8 and pT < 3-4 GeV !

'away side jet'

Triangular Flow v3

17

v3 shows mass splitting expected from hydro flow

Has the magnitude (and pT dependence) expected from geometry fluctuations

(and has different sensitivity to h/s than v2 )

v3 for p/K/p

p

p

v3 v4 v5 versus pT

v2

v3

v4

v5

Hydro calculation for v3

K

v3 : - Explain the 'near side long range ridge' and the away side 'Mach cone’ for |h| > 0.8 and pT < 3-4 GeV !- Compatible with hydrodynamic predictions- Induced by geometry fluctuations

https://aliceinfo.cern.ch/Figure/sites/aliceinfo.cern.ch.Figure/files/Figures/mkrzewic/2011-May-17-triangularity_1020.gif

More on v2: identified particle flow

p/K/p v2

RHIC

PID flow: - Mass splitting and ordering ≈ hydro - p and anti-p are 'pushed' further compared to

RHIC≈ expected from hydro (with larger radial flow)- p and K flow well described by hydro- anti-p flow not well described by hydro in more

central collisions

Centraliy 10%-20%

Centraliy 40%-50%


19




Transverse energy & energy density

20

ε t ≈16 GeV/(fm2c)factor 2.7 larger than RHIC

€

ε = 1

πR2τ

dETdy

R =1.12A1/ 3fm

Energy density (Bjorken)

Grow with power of CM system energy faster than simple logarithmic scaling extrapolated from

lower energy (similar trend than dNch/dh)

21

Hydro parameters from Blast Wave Fit

RHIC

Identified Particle spectra

Hydro Prediction

Very significant changes in slope compared to RHICMost dramatically for protons

Very strong radial flow, b ≈ 0.66 even larger than predicted by most recent hydro

RHIC

more central

-p

K-

K0

p-

22

Ratio at MaximumRHIC

L/K0

'Baryon anomaly': L/K0

Baryon/Meson ratio still strongly enhanced x 3 compared to pp at 3 GeV

- Enhancement slightly larger than at RHIC 200 GeV

- Still present at 6 GeV/c

- Maximum shift very little in pT compared to RHIC

despite large change in underlying spectra !

Recombination + Radial flow?

x 3


23



→ in-medium partonic energy loss → parton nature (quark/gluon), mass dependence?


24

Charged particle nuclear modification factor (RAA)

PLB 696 (2011) 30-39

Extrapolated reference=> large syst. error

€

RAA =# particle observed in Pb - Pb collisions

(#particle observed in pp collisions) × number of binary collisions

€

RAA (pt ) =d2Nch

AA /dηdptd2Nch

pp /dηdpt × Ncoll

Pb-Pb

pp reference

Charged Particle RAA: Ingredients

25

Measured reference, still needs extrapolation for pT> 30 GeV(but not in √s => smaller syst. error)

Note: measured spectrum somewhat different than previous extrapolation

(RAA goes down, but stays well within old systematic error bands)

pp spectrum

2.76 TeV

4-7 GeV

PHENIX

pT 4-7 GeV

<RAA > in pT bins vers. Nch

RAA: Results

26

Rise continues beyond 20 GeVGradual change of slope above 30-40 GeVNote: centrality dependence is independent of reference spectrum !

RAA versus pT

RCP L, K

L

K0

K ±

Identified particle RAA(K/L): - Interesting differences < 6 GeV

- RAA universal > 6 GeV

Charm RAA: Ingredients


D0→ K- p+

D0→ K-p+ D+→ K-p+p+ D*+→ D0 p+

- charm in pp @ 7 TeV- subtract B feed down- absolute cross section- scale (FONLL) to 2.76 TeV- check with CDF & data @ 2.76 TeV- compare with other expts

pp 2.76 TeV

Total Charm cross section

ALICEATLASLHCb

- charm central in Pb-Pb!- subtract B feed down

- absolute cross section (TAA)

=> prompt charm RAA (pT, centrality)- check consistency D0, D+

Charm RAA: results

28

D0→ K-p+ D+→ K-p+p+

Charm RAA: results

29

Qualitative expectation: RAA Charm > RAA Mesons- DE gluon > DE quark (Casimir factor)- DE massless parton > DE massive quark ('dead cone')

Needs quantitative comparison with quenching calculations

- RAA prompt charm ≈ RAA pions for pT > 5-6 GeV

- RAA charm > RAA p for pT < 5 GeV ?

(p+ + p-) RAA

Strong suppression observed in central (0-20%) collisions,

factor ~4-5 for pt >5 GeV/c

little shadowing

Hot medium effect

p-Pb run at LHC crucial to understand the low-pt rise

Heavy Flavour decay muons

30

- single prompt muon cross section (c,b) pp @ 7 TeV

Inclusive Electrons pp

Background

Heavy Flavour Electrons


Inclusive electron spectrum pp 7 TeVBackground 'cocktail' based on measured p±

subtract => heavy flavour electrons (c, b)consistent with pQCD (and measured charm!)

impact parameter cut => select beautyconsistent with pQCD

Beauty Electrons Beauty + Charm

pQCD

Heavy Flavour decay Electrons

32

Inclusive Electrons Pb

Data / Background => hint of excess around 2 GeVinteresting region (thermal radiation ? seen at RHIC…)

33

Heavy Flavour decay Electrons & Muons RAA

- pp reference: 7 TeV measurement scaled (FONLL) to 2.76 TeV

Resulting HFe RAA consistent wit HFm for pT > 3-4 GeV

Heavy Flavour RAA Comparison


Consistent centrality dependence Muons ~ Electrons ~ CMS J/y from B (QM2011)

D mesons clearly lower (charm vs beauty?)

D0 pt > 6 GeV/c m pt > 6 GeV/c e pt > 4.5 GeV/c

J/y suppression: Ingredients


7 TeV pp J/y → mm

2.76 TeV pp

pp J/y Cross Section

7 TeV

2.76 TeV

7 TeV pp 4 LHC expts

Atlas

LHCb

CMS

mm

e+e-

J/y cross section ds/dydpT

7 TeV & 2.76 TeVAgreement with pQCDAgreement among 4 LHC experiments (in region of overlap)

7 TeV

2.76 TeV

J/y suppression: Results

36

PbPb

0-10%

Rather small suppression & centrality dependence

Di-muon channel

pT > 0, 2.5 <y<4

RCP

e+e-

J/y suppression: Compared to..

37

RCP(Alice/Atlas): suppression stronger at high pT ??

Phenix mm

RAA

ATLAS

RCP

Complementary measurements

Surprisingly (?) : less suppression than RHIC !

Progressing analyses

38

pp exclusive analyses: - Resonances in pp- Event shape

characterization in pp

Pb-Pb exclusive analyses:- Identified particle

- Including nuclei andanti‐nuclei- Azimuthal anisotropy- vn

- Chiral magnetic effects

- Event-by‐event fluctuations- HBT vs centrality

Analyses in both systems: - RAA - J/ψ (paper on pp results submitted)

- study of polarization- Single electron from heavy-flavor

decays- Single muons- Open charm- π0 production cross-section & RAA

- Azimuthal correlations

- Λ/K0s

- Multi‐strange particles

Extra slides

39

ResonancesResonances & Hyperons

40

Hyperons

Data Samples

41

Beam Energy # of Events

pp 900 GeV 300 k MB 2009, analysis finished

pp 900 GeV ~ 8 M MB 2010, partially analyzed

pp 2.36 TeV ~ 40 k MB 2009, only ITS, dNch/dh

pp 7 TeV ~ 800 M MB~ 50 M muons

~ 20 M high Nch

2010

PbPb 2.76 TeV/N ~ 30 M MB 2010

pp 2.76 TeV ~ 70 M MB~ 20 nb-1 (rare triggers)

2011, analysis started

30 h only

User activity – month on month increase

Average 7100 (+27%), 280 users (+16%) 1/4 of CPU resources

Average 5000 jobs, 190 usersFactor x2.5 increase over 2010 average

Average 5600 (+ 12%), 240 users (+20%)

Running jobs per user

43

User activity – month on month increase

Two weeks before final review - 10000 jobs in average• 5-6 May – all grid resources freed for users – 80% job slots

utilization ONLY from chaotic user analysis

Average 7500 jobs, 290 users

Stress-test for the GRID & Offline …OK!

44

5x increase of read traffic from Jul-Aug 2010 to today

4545

Detector:Size: 16 x 26 metersWeight: 10,000 tons

Collaboration:> 1000 Members> 100 Institutes > 30 countries

ALICE

ACORDE (cosmics)V0 scintillator centrality| |:h 1.7-3.7, 2.8-5.1T0 (timing)ZDC (centrality)

FMD (Nch -3.4<h<5)

PMD (Ng, Nch)

Central Barrel2 p tracking & PID

Dh ≈ ± 1

Muon Spectrometer 2.5 < h < 4

46

Detector Status

PLC 20J. Schukraft46

Complete since 2008: ITS, TPC, TOF, HMPID,FMD, T0, V0, ZDC, Muon arm, Acorde PMD , DAQ

Partial installation (2010): 4/10 EMCAL* (approved 2009)7/18 TRD* (approved 2002)3/5 PHOS (funding) ~ 60% HLT (High Level Trigger)

2011 10/10 EMCAL10/18 TRD

TRD to be completed end 2011

*upgrade to the original setup

ITS

TPC

TRD

TOF

EMCAL

PHOS

HMPID

L3 Magnet

RCP

e+e-

J/y suppression: Compared to..

47

Surprisingly (?) : less suppression than RHIC !

RCP(Alice/Atlas): suppression stronger at high pT ??

Caveats:

- J/y (B) about 10% (LHCb) => RAA(prompt) lower by ≈ 0.05

- compare to Phenix e+e- ? => less difference, still significant

- shadowing(LHC) > shadowing(RHIC) ? => RAA goes up ?

- cold nuclear matter suppression ?

Phenix mm

RAA

ATLAS

RCP

shadowing range

Complementary measurements

More on v2 • Non-flow contribution (d)• Measure flow fluctuations (s)

• different cumulants

• Identified particle flow (sensitive to radial expansion)



py

py

€

ε =y 2 − x 2

y 2 + x 2

from last LHCC

€

v2{2} ≅ v22 +σ 2

2 + δ

v2{4} ≅ v22 −σ 2

2


€

v2 =py

2 − px2

py2 + px

2(elliptic flow)

More on v2

v2 no eta gap between particles

v2 |h|>1

both v2 corrected for remaining non-flow(Hijing or scaled pp)

Non-Flow corrections

€

v2{2} ≅ v22 +σ 2

2 + δ

v2{4} ≅ v22 −σ 2

2

https://aliceinfo.cern.ch/Figure/sites/aliceinfo.cern.ch.Figure/files/Figures/snelling/2011-May-15-v2_all.gif

More on v2 v2 Fluctuations Non-Flow corrections

€

v2{2} ≅ v22 +σ 2

2 + δ

v2{4} ≅ v22 −σ 2

2

Flow fluctuations:- comparable to RHIC (driven mostly by geometry)


More on v2 v2 Fluctuations Non-Flow corrections

€

v2{2} ≅ v22 +σ 2

2 + δ

v2{4} ≅ v22 −σ 2

2

p/K/p v2

RHIC

Flow fluctuations:- comparable to RHIC (driven mostly by geometry)

PID flow: - Mass splitting and ordering ≈ hydro - p and p are 'pushed' further compared to RHIC ≈ expected from hydro (with larger radial flow)


Triggered correlation at high pt & jets: IAA

52

• Extract near and away-side jet yields from per-trigger yields• Compare central and peripheral

collisions ICP

• Compare Pb+Pb and pp IAA

• Non-jet component (baseline) needs to be removed (no known assumption-free methods… pedestal at p/2, ALICE flow… )

• Measure in a region where the signal dominates over pedestal and v2 modulation(8 GeV/c < pT,trig < 15 GeV/c)

near

away

53

Triggered correlation at high pt & jets: IAA

• Peripheral events consistent with unity

• Near-side of central events slightly enhanced

IAA ~ 1.2 … unexpected and interesting• Away side of central events suppressed:

IAA ~ 0.6 … expected from in-medium energy loss

central

central

peripheral

Near Side

Away Side

Multiplicity & system size

54

• Multiplicity at central rapidity (Ingredient for many models)

• Study of system “size” at decoupling & decoupling time (within hydrodynamic scenario) via HBT analysis (quantum interference of

identical bosons emitted close in phase space from a common source) Phys.Lett.B 696:328-337,2011

Multiplicity at forward rapidity Total multiplicity

} Last LHCCK. Aamodt et al. (ALICE), Phys. Rev. Lett. 105, 252301 (2010)K. Aamodt et al. (ALICE), Phys. Rev. Lett. 106, 032301 (2011)

~linear increase with Npart

Tracking & Vertexing

55

SDD at nominal resolution

p±,p0 RAA

56

p0 from reconstruction of gamma conversions Being cross-checked with p0 spectra measured with EMCal & PHOS calorimeters

RHIC

Pb-Pb: K/p

STAR (including feed down)

PHENIX, Brahms (feed down corrected)

p/p

Particle Ratios

57

- pp: Thermus thermal fit rather poor (wasn't this better for pp at lower energies ??)

- K/p grows slightly from pp value- p/p ≈ like pp

Pb: p/p off by factor > 1.5 from predictions !but very compatible with RHIC !!

?

pp: 900 GeV & 7 TeV

Range of Thermal model prediction

Before we can conclude anythingwe need more particle species..

Comparing vn with en

58

CGC

GlauberGlauber

CGCCGC

CGC

v2 Fluctuations

v2 & v3 ultra-central (0% →5%) v2 {2}/e{2} & v2{4}/e{4}

v2 /e2 & v3/e3

Glauber

Glauber

'Flow Tomography' has thepotential to constrain geometry

improved precision on h/swhen comparing full hydro to measurements

Heavy Flavour decay muons

59

- single prompt muon cross section (c,b) pp @ 7 TeV- scaled (FONLL) to 2.76 TeV

- RAA (pT, centrality) with inclusive muons

Semi-peripheralPb-Pb 40-80%

Central Pb-Pb0-10%

Geometry of AA collisions

60

Centrality

61

2.8<h<5.1

-3.7<h<-1.7

Charm RAA: results

62

Strong suppression observed in central collisions (0-20%) wrt TAA-scaled pp reference

Significant suppression also in semiperipheral (40-80%) wrt TAA-scaled pp reference

• Can LHC solve the puzzle (measuring J/y and U families) ?

– suppression only: suppression for Y'(2S) ≈ y', Y''(3S) ≈J/y– suppression + recombination: Y', Y'' ~unaffected, J/y less suppression than @ RHIC

J/y Suppression

63

QM 2008 (P. Seyboth)

y’ c Y’’(3S) Y’(2S) J/y Y

Td/Tc1-1.2 1-1.2 1.1-1.3 1.2-2 1.5-2.5 3-5

Lattice QCD based predictions

of 'melting' temperature Td

(a bit dated..)

SPS ≈ RHIC

T/TC 1/-r-

-

J/-, -’

-c

y’

-b’

-’’

4

2

1

LHC??

Chiral Magnetic Effect ('strong parity violation')

64

RP 2cos

B

+-

Same charge correlations positiveOpposite charge correlations negative

RHIC ≈ LHCsomewhat unexpected

should decrease with Nch

may decrease with √s

RHIC : (++), (+-) different sign and magnitude

LHC: (++),(+-) same sign, similar magnitude?

cos

+ -

B

?

RHIC

RHIC

Local Parity Violation in strong magnetic Field ?

alice s tatus report 106 th lhcc meeting - open session

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