ALICE experiment at the LHCthe activity of the LNF group

Pasquale Di Nezza

40° LNF SC meeting 24/06/10

Alice in 1 slideWhat makes ALICE different from ATLAS, CMS and LHCb?

Experiment designed for Heavy-Ion collisionsVery robust tracking

high granularity detectors with many space points per track

very low material budget and moderate magnetic field

PID over a very large pT rangehadrons, leptons and photons

Very low pT cutoffExcellent vertexing

Prize ro be paidSlow detectorsLimited h and pT coverage

Complementary to other experiments

The spectrometer is up and running at very high efficiency

3 papers published + 5 circulating•First pp collisions at the LHC as observed with the ALICE detector: measurement of the charged particle pseudorapidity density at sqrt(s)=900 GeV [EPJ C 65 (2010) 11] - The first LHC paper on real data•Charged-particle multiplicity measurement in pp collisions at sqrt(s)=0.9 and 2.36 TeV with ALICE at LHC [accepted by EPJ, arXiv:1004.3034]•Charged-particle multiplicity measurement in pp collisions at sqrt(s)=7 TeV with ALICE at LHC [accepted by EPJ,

arXiv:1004.3514] – The first LHC paper (arXiv) on data at 7 TeV

The LNF Group

1. N.Bianchi (group leader)2. G.P.Capitani3. A.Casanova4. L.Cunqueiro5. P.Di Nezza6. A.Fantoni7. P.Gianotti8. S.Liuti9. A.Moregula10. V.Muccifora11. A.R.Reolon12. F.Ronchetti

A.Orlandi (tech)A.Viticchiè (tech)

12 researchers for 11.5 FTEAverage participation of 96%

1 expert on call2 shift leaders1 deputy spokesperson for calorimeter2 members of the calorimeter

Management Board1 calorimeter construction coordinator

The activity of the LNF group

The activity of the LNF group

Construction of thee.m. calorimeter

The activity of the LNF group

Construction of thee.m. calorimeter

•Online monitoring•Offline codes

•High Level Trigger

The activity of the LNF group

Jet physics

Jet reconstructionMC in QGP

The activity of the LNF group

L

Jets with associated L

TMDs in pp

10

France, Italy and USA Collaboration

– 7 US Super-Modules (SM)– 3 EU SMs (Italy and France)– Construct started in 2008– 4/10 SM installed in 2009– Complete installation in 2011

Lead-Scintillator Sampling Calorimeterh= 1.4, =100o, 20.1 X0

Shashlik Geometry, APD Photosensor12k Towers

EMCal

Basic Unit = 4 channels

Assembling station (2 on site)

Aluminization of200k fibers (WLS)

Quick overview on the calo performances

Quick overview on the calo performances

0.02E0.11/σ(E)/E

High Level Trigger for EMCal

PbPb collisions @ 8 kHz corresponds to2 kHz calo tower hit rate

HLT reduces to a 40% EMCal data occupancy

Main HLT strategy:•Reconstruction for calibration and monitoring•Event rejection using high-ET (cluster) trigger OR jet trigger

HLT study overlapping few hundreds of pp real events to simulate PbPb

collisions

DCal – 6 super modules

PHOS – 5 modules shown

h~0.7

From EMCal to DCalDCal, the first upgrade approved by the Alice collaboration:

extension of EMCal for jet-jet and g-jet physics

DCAL modules:same technology than EMCal

LNF contribution with tools, expertise and manpower

Jets to access to the QGP

High-pT partons produced in hard interactions undergomultiple interactions inside the collision region priorthe hadronization … so they loose energy throughmedium induced gluon radiation the jet quenchingas a golden channel to probe the QGP

Jet →Jet’ + soft gluons + soft hadrons from UE

• Decrease of leading particle pT (energy loss)• Increase of number of low momentum particles

(radiated energy)• Increase of pT relative to jet axis (jT)

– Broadening of the jet– Out of cone radiation (decrease of jet rate)

• Increased di-jet energy imbalance and acoplanarity.)

1ln()ln(

zp

E

Borghini,Wiedemann, hep-ph/0506218

Try to find something like this……

Try to find something like this……

in this !

Role of EMCal in the jet reconstruction100 GeV jet

100 GeV JetsFull simulationR=0.4

TPC+EMCal

F[rad]pp (14 TeV) 50 pb-1

PbPb (5.5 TeV) 0.5 nb-1Jets

Charged jets: 109 evts pp

107 evts cent. PbPb

Track + Calo

Charged only

Jet yield in 20 GeV bin

Jet reconstruction

dijets @ 7 TeV

1 Jet: h-0.39 2.15 pT= 48.3 Tracks 11
2 Jet: h-0.46 5.36 pT= 31.3 Tracks 5

Jet spectrum safely reconstructed up to 50 GeV

Jets within |h| < 0.5, Tracks within |η| < 0.9

Reconstructedglobal tracks

MC primaryparticles

MC primarycharged particles

UA1 R = 0.4 (default), 0.7 R = 0.4, 0.7 R = 0.4, 0.7

fastJET anti-kT R = 0.4, 0.7 R = 0.4, 0.7 R = 0.4, 0.7

fastJET kT R = 0.4, 0.7 R = 0.4, 0.7 R = 0.4, 0.7

fastJET SISCone R = 0.4, 0.7 R = 0.4, 0.7 R = 0.4, 0.7

CDF R = 0.4, 0.7 R = 0.4, 0.7 R = 0.4, 0.7

Deterministic Ann. R = 0.4, 0.7 R = 0.4, 0.7 R = 0.4, 0.7

Large set of jet definitions for many systematic studies/corrections

Jets @ 7 TeV

Pileup and UE background contaminate the jet proportionally to its area

•As a consequence, we will be forced to use a small jet resolution•A neat pp reference for the jet observables is strongly needed

pT shift correction due to the hadronization is important to compare data to parton level analytical calculation

Ratio=parton/h shows hadronizationdominates at small resolution and stronger at low-intermediate jet energies

eventsunderlying

T

radiationveperturbati

T

ionhadronizat

TT pppp__

Wealth of new intriguing phenomena in the medium!

What’s new for jets in the LHC (PbPb)

Background studies in PbPb: Fastjet method area based

Pileup and UE are distributed uniformly in h and

jetjetparton

T

jet

T AσAρp~(measured)p

r= diffuse noisesnoise fluctuations

QPythia: a Monte Carlo for the Jet QuenchingIn collaboration with the Santiago University theory group[Armesto, Cunqueiro, Salgado]

Distributions for different quenching

Comparison with RHIC data

Transverse L polarization in unpolarized pp scattering

L polarization is high only at large xF.At ALICE, restricted at midrapiditieswhere xF is very small (1/pt) … unless

This opens the new channel of the TMDs(Transverse Momentum dependent Distribution

and fragmentation functions)

Transverse L polarization in unpolarized pp scattering

L polarization is high only at large xF.At ALICE, restricted at midrapiditieswhere xF is very small (1/pt) … unless

This opens the new channel of the TMDs(Transverse Momentum dependent Distribution

and fragmentation functions)

q1f

unpolarised quarks and nucleons

q1g

longitudinally polarisedquarks and nucleons

q1h

transversely polarisedquarks and nucleons

F nxhxgxfx T15151L1Tw2Corr Sγγ)(γ)(S)(2

1)(

chiral-odd functions

Expected magnitude of the SSA(D.Boer et al. model, PLB 659 (2008))

pp@7TeV (EL up to 16 GeV)

L inside jets

Conclusions

Conclusions

Alice is running happily:

LNF group, working in:• hardware (EMCal+DCal)• online/offline software calorimetry• jet physics• QGP phenomenology• polarized physics in pp • various responsibilities

with 12 persons at 96% of FTE is fully involved in the project …

Pasquale Di Nezza

Conclusions

Alice is running happily:

LNF group, working in:• hardware (EMCal+DCal)• online/offline software calorimetry• jet physics• QGP phenomenology• polarized physics in pp • various responsibilities

with 12 persons at 96% of FTE is fully involved in the project … with great enthusiasm!

Pasquale Di Nezza