A Very High Momentum Particle Identification Detector for the ALICE experiment at the LHC.

Dorado del mar Puerto Rico, April 8, 2012

Edmundo GarcíaChicago State University

for the VHMPID Group

28th Winter Workshop on Nuclear Dynamics

Cherenkov Radiation2

symmetric dipole distribution incoherent destructive interference

symmetric dipole distribution coherent Cherenkov radiation

The 1958 Physics Nobel Prize was awarded jointly to P. A. Cherenkov, I. M. Frank and I. Yevgenyevich “for discovery and interpretation of Cherenkov effect”

From the Physics to the Detector3

First used by E605Fermilab

Helium RadiatorCaF2 window

Recent Cerenkov Detectors4

COMPASS

LHCb

ALICE

HMPID

High Momentum Particle Identification Detector5

MIP

Cherenkov Ring

Outline

• Introduction• The Detector• Technical Notes• Physics Possibilities• Final Notes

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HMPID

A Large Hadron Collider Experiment7

EMCAL

HMPID

TOF

TRD

PMD

TPC

PHOS

ITS

MUON

Selected Detector PID in ALICE

ALICE PID

separation @ 2s

VHMPID

separation @ 3s

VHMPID

Existing gap between low and high pT ALICE for detailed (3 s) hadron PID

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Very High Momentum Particle Identification Detector10

3s PID of π, K, p on a track-by-track basis

ALICE rdE/dx and VHMPID

rdE/dx• Statistical, reaching high-pT

• Clean π sample• Protons are difficult• No kaon PID

VHMPID• Track-by-track• Difficult at low pT

• Limited acceptance (maximum 30% of central barrel)

Estimated improvements in Particle Production

• Error bars statistical plus systematic• Lager yield of protons

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• Pytha• Medium modification prediction

by Wiedemann et al

Flow Jet Fragmentation

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• TPC based on analysis of 2010 data• Improvement based on VHMPID stat

& syst. error

• Ratio of fragmentation functions• Errors depend on PID

systematics, statistics, and jet energy determination

ALICE Integration

• VHMPID + (DCaL) or PHOS system in 5 sector (20o each)

• 30% central barrel acceptance• C4F10 (C4F8O) at gas pressure

3 atm, 40o C• Radiator length 50 cm keeping

basic performance

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tracking layer 3 cm

photo detector 9 cm

radiator 50 cm

mirror and insulation 9 cm

tracking layer 3 cm

Triggering TRD

• Transition Radiation Detector trigger

• 6 tracking layers 400 – 600 resolution

• Readout 200 Hz 5% dead time• Trigger based on matching at

least 4 track segments, track threshold 5 GeV/c pT

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Triggering HPTD16

• Close Cathod Chambers*

• Provides L0 trigger for pp• Provides of L1 trigger PbPb• MIP detection *G. Hamar, G. Kiss, D. Varga: Nucl.Instrum.Meth. A648 163-167 (2011)

Performance Simulations17

0 . 0 0 0 0

0 . 0 7 1 6

0 . 1 4 3 1

0 . 2 1 4 7

0 . 2 8 6 2

0 . 3 5 7 8

0 . 4 2 9 4

0 . 5 0 0 9

0 . 5 7 2 5

0 . 6 4 4 1

0 . 7 1 5 6

D e t e c t o r I m a g e : I n c o h e r e n t I r r a d i a n c e

3 / 7 / 2 0 1 2D e t e c t o r 1 , N S C G S u r f a c e 1 : S i z e 2 0 0 0 . 0 0 0 W X 2 0 0 0 . 0 0 0 H M i l l i m e t e r s , P i x e l s 2 5 0 W X 5 0 0 H , T o t a l H i t s = 1 2 0 0 0 0 0P e a k I r r a d i a n c e : 7 . 1 5 6 2 E - 0 0 1 W a t t s / c m ^ 2T o t a l P o w e r : 1 . 2 0 0 0 E + 0 0 1 W a t t s

Mirror misalignment simulation

Center 1

Center 2 10 GeV/c pions and

kaons

Chromatic dispersionlimited detector resolution

Reconstructed Cherenkov angle in PbPb background

VHMPID prototype 18

High-pT physics in proton-proton collisions

• Preset FF set are extracted from global data fits from and RHIC spectra

• NLO calculations uncertainty is large in the comparison to experimental data

• Improved PID in ALICE could significantly contribute to improve the constraints on the FFs with through high-pT identified particle spectra

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F

S. Albino, A Kniehl, G. Kramer Nucl.Phys.B803, 42-104,2008

S. Albino, A. Kniehl, G. Kramer Phys. Rev. Lett 104, 242001, 2010CDF et al Phys. Rev. D. 79, 112005 , 2009

S. Albino, A Kniehl, G. Kramer Nucl.Phys. B803, 42-104,2008

Track - by - Track PID and Jets application20

• Investigate the production mechanism of heavy prompt quarkonia by studying the kinematics of jet associated particles.

• Characterize of the jets accompanying the J/ production in p-p collisions such as the scalar sum of transverse momentum, the fragmentation function, the cone radius, or jet composition.

• Compare jet characteristics in p-p and A-A collisions

A.C. Kraan, arXiv:0807.3123v1 [hep-ex]

Study of Hadronization and Jet Quenching in Pb-Pb21

• Need more differential probes to understand hadronization in medium and medium properties.

• Particle identification at high pT , should be the basis for most potentially new measurements

Sapeta, Wiedemann Eur.Phys.J.C55:293-302,2008

P. Levai, D. Berenyi, A. Pasztor, and V.V. Skokov, Jour. Phys. G38 (2011)

High-momentum resonance production

• Reconstructed - meson peak in invariant mass distribution for k+k- pairs in min. bias PbPb collisions at 5.5 ATeV

• VHMPID acceptance based on 5 Million central HIJING events

• S/B 10 : 1

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23

Backup Transparencies

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The ‘golden cuts’ on rdE/dx distributions for TPC25

Present vs. ideal TPC performance

Kaon contamination in pp slightly higher at similar pT compared to PbPb

Resolution in pp (5.4%) slightly better (6.1% in PbPb)

Photoelectrons

Charged particle at saturation in 50 cm of C4F10 at 3 atm

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C4F10 dependence vs resolution 50 cm radiator