Heavy-Quarks with ALICE Some Highlights from the ALICE Physics Week in Prague March 2008

1 HD lunch talk, 30 Apr 2008 Kai Schweda

Heavy-Quarks with ALICE

Some Highlights from the ALICE Physics Week in Prague March 2008

Kai Schweda, University of Heidelberg / GSI Darmstadt


Outline

Motivation

Total charm cross section with ALICE

B J/ + X feeddown

1st day Detector Performance in p+p

Summary

HD lunch talk, 30 Apr 2008 Kai Schweda

Quark Masses

1) Higgs mass: electro-weak symmetry breaking. (current quark mass)

2) QCD mass: Chiral symmetry breaking. (constituent quark mass)

Strong interactions do not

affect heavy-quark masses.

Important tool for studying properties of the hot/dense medium at RHIC and LHC.

Test pQCD predictions at RHIC and LHC.

Total quark mass (MeV)

X. Zhu, M. Bleicher, K.S., H. Stoecker, N. Xu et al., PLB 647 (2007) 366.


Heavy Quark Production

1) Charm x 10

2) Beauty x 100

3) Heavy-quarks abundantly produced at LHC !STAR data: A. Suaide, P. Djawothoto QM2006;Calcs.: R. Vogt.


J/ Production

suppression,compared to scaled p+p

regeneration,enhancement

Low energy (SPS): few ccbar quarks in the system suppression of J/

High energy (LHC): many ccbar pairs in the system enhancement of J/

Signal of de-confinement + thermalization of light quarks !

(SPS)

P. Braun-Munzinger and J. Stachel, Nature 448 (2007) 302.


Predictions for LHC

large ccbar production at

LHC

corona effects negligible

regeneration of J/

dominates

striking centrality

dependence

Signature for QGP

formation !

Initial conditions at LHC ?

A. Andronic et al., nucl-th/0701079.

cc

ηηddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

=


Charm at the LHC:testing pQCD at s = 14 TeV

• Important test of pQCD in a new energy domain• D production not yet fully understood at Tevatron and RHIC• Need displaced vertex technique for precise heavy-flavor measurements

Tevatron data: CDF PRL91 (2003) 241804, RHIC data: Y. Zhang, QM2008,FONLL calcs. R. Vogt, Eur. Phys. J.ST 155 (2008) 213.


Hadronic charm in ALICEHadronic charm in ALICE

TPC (tracking)

TOF (K/ id)

ITS (vertexing)

K

D0 KD+ K Ds KK D* D0 D0 K c Kp

understudy


Plot: A. Shabetai

D0 + + K- Reconstruction

D0, c= 123 m

+

K-


Charm cross section in pp

D0 KExpected sensitivity in comparison to pQCD:

1 year at nominal luminosity(109 pp events)

Detector configuration:ITS + TPC + TOF

~1 month

stat. err. vs # events

Slide: A. Dainese, INFN - Italy.


Inner Tracking System (ITS)Silicon Pixel Detector (SPD):• ~10M channels• 240 sensitive vol. (60 ladders)

Silicon Drift Detector (SDD):• ~133k channels• 260 sensitive vol. (36 ladders)

Silicon Strip Detector (SSD):• ~2.6M channels• 1698 sensitive vol. (72 ladders)

SPDSSD

SDD

ITS total:2198 alignable sensitive volumes 13188 d.o.f.



Effect of ITS misalignment on d0 resolution

• Impact parameter resol:

track = ascatter/pt bmeas cmisalign

• Effect studied with full simulation of exptected initial (full+) and residual (after realignment) misalignments

• See talk tomorrow• Effect on D0 measurement

studied (next slides)

nullresidualfullfull+



Effect of misalignment on S/B and significance (S/S+B)

• Residual misalignment: negligible effect• “Full” misalignment: 15-20% worsening of statistical errors


Kinematical distributions: prompt J/ versus secondary J/

• rapidity and transverse momentum(all distribution normalized to 1 m.b. event)

y

%8.40 /tot

b from /=

JJ

but pT dependent

Primary J/

Secondary J/

Slide: Giuseppe E Bruno, Università di Bari and INFN - Italy.

B J/ + X


• product of impact parameters d0xd0

Kinematical distributions: prompt J/ versus secondary J/

Primary J/

Secondary J/

Slide: Giuseppe E Bruno, Università di Bari and INFN - Italy,also: Wolfgang Sommer, Uni Frankfurt.

• Disentangle

primordial J/

from

B J/ decay

• Determine bbar


J/ e+ + e- Reconstruction

J/ e+ + e-

(BR = 6%)

Reconstruct

invariant mass

TRD identifies

electrons

4/18 SM

installed for first

p+p run

Identify

quarkonia

J/: c c : b b


Summary

Heavy-quarks (c,b) carry important information on

de-confinement and light-quark thermalization

Measure yield, spectra, correlations and v2 of:

D0, D+, D*+, Ds, J/b,

to identify and characterize QGP !

ALICE is well suited for these studies


Average Momentum Correlator – angular dependence

Enhanced correlations

Only FC produces correlations

at high Distinction of the baseline at

middle – flat to 0

Average Momentum Correlator

as a sensitive measure of

back to back correlations

Same eventMixed event

At full : <pt,1pt,2> = 199.5 +/- 6 (MeV/c)2

or pt~30 %


D Meson Pair Correlations : Some Results

= (D) – (Dbar)

• E791 : Eur. Phys. J. direct C1 (1999) 4• WA92 : Phys. Lett. B385 (1996) 487• NA32 : PLB257 (1991) 519 , PLB302 (1993) 112, PLB353 (1995) 547

Correlation variable studied:

103 /

N *

dN

/d(

)

•At low energies, D-Dbar production correlated!

•Pythia describes these correlations!

How about LHC energies?

p

p c

c D

DGeorgios Tsildeakis,HD.


Charm correlations

c-cbar are correlated

• Flavor creation: back to

back

• Gluon splitting: forward

• Flavor excitation: flat

Correlations vanish

frequent interactions

among partons !

probe light-quark

thermalization !

Documents

Heavy-Quarks with ALICE Some Highlights from the ALICE Physics Week in Prague March 2008