Upload
ownah
View
34
Download
0
Embed Size (px)
DESCRIPTION
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 1 st day Detector Performance in p+p Summary. - PowerPoint PPT Presentation
Citation preview
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
2 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
4 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
5 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
6 HD lunch talk, 30 Apr 2008 Kai Schweda
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
=
7 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
8 HD lunch talk, 30 Apr 2008 Kai Schweda
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
9 HD lunch talk, 30 Apr 2008 Kai Schweda
Plot: A. Shabetai
D0 + + K- Reconstruction
D0, c= 123 m
+
K-
10 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
11 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
Slide: A. Dainese, INFN - Italy.
12 HD lunch talk, 30 Apr 2008 Kai Schweda
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+
Slide: A. Dainese, INFN - Italy.
13 HD lunch talk, 30 Apr 2008 Kai Schweda
Effect of misalignment on S/B and significance (S/S+B)
• Residual misalignment: negligible effect• “Full” misalignment: 15-20% worsening of statistical errors
14 HD lunch talk, 30 Apr 2008 Kai Schweda
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
15 HD lunch talk, 30 Apr 2008 Kai Schweda
• 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
16 HD lunch talk, 30 Apr 2008 Kai Schweda
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
17 HD lunch talk, 30 Apr 2008 Kai Schweda
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
18 HD lunch talk, 30 Apr 2008 Kai Schweda
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 %
20 HD lunch talk, 30 Apr 2008 Kai Schweda
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.
21 HD lunch talk, 30 Apr 2008 Kai Schweda
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 !