Transcript Status of ALICE PLHC2011, Physics at the LHC 2011, Perugia, 5-11 June 2011 • • • • Detector status and performance Major achievements in pp-runs Highlights from Pb-Pb.

Status of ALICE
PLHC2011, Physics at the LHC 2011, Perugia, 5-11 June 2011
•
•
•
•
Detector status and performance
Major achievements in pp-runs
Highlights from Pb-Pb running
Outlook on the future
Johannes P. Wessels
University of Münster and CERN
Central Barrel
2 p tracking & PID
Dh ≈ ± 1
Muon Spectrometer
2.5 < h < 4
Detector:
Size: 16 x16 x 26 m
Weight: 10,000 t
Collaboration:
> 1200 Members
> 100 Institutes
> 30 countries
Detector Status
EMCAL
Complete since 2008:
ITS, TPC, TOF, HMPID,
FMD, T0, V0, ZDC,
Muon arm, Acorde
PMD , DAQ
HMPID
TOF
TRD
TPC
Partial installation (2010):
4/10 EMCAL* (approved 2009)
7/18 TRD* (approved 2002)
3/5 PHOS (funding)
ITS
~ 60% HLT (High Level Trigger)
2011
10/10 EMCAL
10/18 TRD
L3 Magnet
PHOS
*upgrade
to the original setup
3
PLC 20J. Schukraft
Particle Identification in ALICE
PHOS, EMCAL

‘stable’ hadrons (p, K, p): 100 MeV < p < 5 GeV (several 10 GeV)

dE/dx in silicon (ITS) and gas (TPC) + time-of-flight (TOF) + Cherenkov (HMPID)
 decay topologies (K, LWD)


K and L decays beyond 10 GeV
leptons (e, m), photons hp0

electrons TRD: p > 1 GeV, muons: p > 5 GeV, p0 in PHOS, EMCAL: 1 < p < 80 GeV
Particle Identification
ITS Silicon Drift/Strip dE/dx
TPC dE/dx
Ω  ΛΚ
TOF
Anti-Alpha Candidates in Pb-Pb
Work in Progress
Time of flight (sensitive to m/z-ratio):
Three candidates
confirmed by TOF
analysis
Se
Hy
on
dis
Momentum Resolution
• Combined TPC + ITS tracks
• Background/weak decays
excluded via DCA cut to
primary vertex
• Tracks within |η| < 0.8
• Resolution determined from
track residuals, verified with
cosmics and reconstructed
decay widhts (e.g. KS0)
Good resolution already with early
Pb+Pb calibration.
Particle ID with TOF
Central Pb-Pb collisions
|y| < 0.5
2s p/K separation up to 3 GeV/c
2s K/p separation up to 5 GeV/c
system time resolution in Pb-Pb (~85ps) – better than in p-p (~110ps)
Particle Identification in Pb-Pb
Raw yields: a global fit of Time-Of-Flight signal - mass hypotesis i (π, K, p)
constrains the integral of the fit to the total number of entries in the TOF PID
Central Pb-Pb collisions
|y| < 0.5
pions
kaons
protons
mismatch background
on the % - level
Protons : 0.95 < pT < 1.05 GeV/c
Reconstruction of Weak Decays
• resolution of d0 (impact parameter) is the key parameter
for the reconstruction of weak decays of D-mesons
decay length: ct= 300-500 mm (D+,-), ct=124 mm (D0)
D Meson Reconstruction in ALICE
•
•
•
Main selection: displaced-vertex topology
Tracking and vertexing precision is crucial here
Inner Tracking System (ITS) with 6 Si layers
–
•
two pixel layers at 3.9 cm (closest barrel layer at LHC!) and 7 cm
The ITS was aligned using cosmics and collisions
–
The inner pixel layer
current resolution for pixels: 14 mm (nominal: ≈11 mm)
Pb-Pb
pp
proton
kaon
pion
Same tracking
precision
in pp and Pb-Pb,
described in MC,
incl. mass dep.
TRD Electron-Pion Separation
• dE/dx measured in the TPC – dE/dx expected for electrons (from Bethe-Bloch)
• without likelihood information and with likelihood information from TRD
• little change in the number of identified electrons; large suppression of pions
p0 Reconstruction in EMCAL
Reconstruction of πo invariant mass in semi-central Pb-Pb collisions
p0 and h (and γ) Reconstruction
pp  p0 + Xn

e+e-e+e(mp0 = 0.135 GeV/c2, BR = 0.988)
e+
e-
pp  h + Xn

e+e-e+e(mh = 0.548 GeV/c2, BR = 0.393)
3 independent measurements:
Conversions, PHOS, EMCAL
run 104792, event 2248
Material Budget
-ray image of ALICE
photon conversion vertices
‘out-of-the-box’
total ~ 8%X/X0
p-Nucleus
absorption cross section
after several
iterations
p0 and h from Conversions
M  1 2  2 E 1 E 2 (1  cos   1 2 )
p0
h
Data Samples
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
2010
PbPb
2.76 TeV/N
~ 800 M MB
~ 50 M muons
~ 20 M high Nch
~ 30 M MB
pp
2.76 TeV
~ 70 M MB
~ 20 nb-1 (rare triggers)
2011, analysis started
2010
pp Physics in ALICE
•
‘comparison data’ for heavy ion program
– many signals measured ‘relative’ to pp
•
comprehensive study of MB@LHC
– tuning of Monte Carlo generators
(background to BSM)
– complementary to other LHC expts
– address specific issues of QCD
•
very high multiplicity pp events
– dNch/dh comparable to HI
=> mini-plasma ?
The 2010 Data Sample
• p+p@7TeV: >800M MB, >50M µ triggers, >10M high multiplicity
• [email protected]: ~30M nuclear collisions
Charged Particle Pseudorapidity Density
ALICE 7 TeV:
Eur.Phys.J.C68:345-354,2010;
ALICE 0.9/2.36 TeV:
Eur.Phys.J.C68:89-108,2010.
• Multiplicity increases faster than predicted by models
p, K, p at 900 GeV and at 7 TeV
K/p
p/p
Main Results:
- very large K/p ratio at high pT
- not reproduced by any event generator
- p/p: some MC do well at high pT, others at low pT
Details in talk of L. Ramello, Tu, 9:55
(Anti)-Proton Production
•
Excellent understanding of
material budget is pre-requisite
for p/p-ratio measurement on
the percent level
•
Proton cannot be fully stopped
at LHC
•
Little room for baryon number
transport over large rapidity
gaps
0.9 TeV: 0.957±0.006(stat) ±0.014(syst)
7 TeV: 0.990±0.006(stat) ±0.014(syst)
Details in talk of M. Broz, Tu, 15:15
Open Charm from ALICE
D0  K-π+
D+  K-π+π+
Study open charm production in as many channels as possible
D Meson Cross Sections:
pp 7 TeV, |y|<0.5
FONLL: Cacciari et al., private comm.
GM-VFNS: Kniehl et al., private comm.



2 < pt < 12 GeV/c, with 1.6 nb-1 (~20% of 2010 statistics)
y acceptance is pt-dep (Dy~1.01.6): data scaled to |y|<0.5
pQCD predictions (FONLL and GM-VFNS) compatible with our data
Charm in pp @ 7 TeV: Outlook


Extend pt range with full 2010 statistics: 1—20 GeV/c (e.g. D* shown)
The shy charming: Ds and Lc
ALICE Performance
10/05/2011
Heavy Ion Collisions Evolution of the Fireball
soft
hard
probes
global observables:
multiplicities, rapidity distributions
geometry of the emitting source:
HBT, impact parameter via
zero-degree energy flow
early state collective effects:
elliptic flow
chiral symmetry restoration:
neutral to charged ratios,
resonance decays
fluctuation phenomena - critical behavior:
event-by-event particle composition and
spectra
degrees of freedom as a function of T:
hadron ratios and spectra,
dilepton continuum, direct photons
deconfinement:
charmonium and bottonium spectroscopy
energy loss of partons in QGP:
jet quenching, high pt spectra,
open charm and open beauty
First Measurements in
Heavy-Ion Collisions at LHC
• Particle production
– Multiplicities – how does the particle production depend on energy and
impact parameter of the collisions? Are we able to describe it?
• Emission of particles – collectivity – dynamical evolution
– Azimuthal anisotropy – how the initial spatial anisotropy manifests itself
in final momentum anisotropy? – Collective flow at LHC?
– Collectivity? How do the source dimensions evolve with energy?
• Parton energy loss
– Is QCD medium at LHC opaque to high energy partons?
– Evolution of jet quenching with energy?
Details in talk of A. Morsch, Tu, 12:25
+
!
#
Centrality Selection – Glauber Model
"
'
D
:;
#
7"
& / * 7production is
• I Assume
particle
factorizes into
"
"
number
of participants
Npart
7 collisions
' .Ncoll !
number of
• Assume
Negative Binomial Distribution
6; B
@; B "
for both
f*Npart + (1-f) Ncoll '
$
#!
3 '
&F;
F; C+ '
3
F; *
• Relation of percentile classes to
Glauber
" values (<Npart>, etc)
purely
' geometrical
&J7 " byKslicing in
*
impact parameter
#
"
A
!
"
#
!
%9
Particle Production in Pb-Pb
PRL 106, 032301 (2011)
Energy dependence
Centrality dependence
PRL 105, 252301 (2010)
Energy dependence
p-p ~ sNN0.11
A-A ~ sNN0.15 (most central)
Multiplicity dependence on centrality: similar trend as at RHIC
Particle Production in Pb-Pb:
Measurement of Source Dimensions
Derived from HBT-Interferometry of identical bosons (ππ)
• Energy dependence:
system twice the size and 30% longer lived w.r.t RHIC
follows the trend of multiplicity
faster expansion <=> larger collective flow
• Important constraints on [hydrodynamical] modelling
Particle Production in Pb-Pb:
Azimuthal Anisotropy – Elliptical Flow
py
Reaction plane
px
z
y
v2 
x

y
2
 x
2
y2  x2
Initial spatial anisotropy
Elliptical flow
p x2  p y2
p x2  p y2
Final momentum anisotropy
Reaction plane defined by
“soft” (low pT) particles
0
.3
0
.2
5
tant [12,15–18].
i
i
i
In
i summary we have presented the first elliptic flow
0
.0
8ment at the LHC. The observed similarity at
me
a
sure
f l elliptic flow at low
RHIC and thefLHC off pt -differentia
f
0
.
0
6
pt is consistent with predictions of hydrodynamic models
[7,14]. We find that the integrated elliptic flow increases
p fiffiffffi
p fiffiffffi
0
.0
4
about
30% from sNN ¼ 200 GeV at RHIC to sNN ¼
f
i
i
0
.0
2
ALICE
(a
)
v2{2} 40%-50%
) P2(?>KJ(=K=I >=(_=>?>`(qI >g(8:#"HT
Particle Production in Pb-Pb:
Q#+4B:( &) +*C$B4*5&95&Q@7Q@R&
Elliptical Flow v2
< K9? $"/ #:&#59%*"+*) F&
v2{4} 40%-50%
D
0
.2
o
I
0
.1
5
week ending
R
SI CA L REV I EW L ET TERS
17 DECEMBER 2010
0
.1
D
e in excellent
(
a
)
C
v {2}
0
.0
5
0
.3
PRL
105,
252302
(2010)
)
P2(?>KJ(=K=I
>=(_=>?>`(q
I
>g(8:#"7+&
r
tions for the
0
.0
8
i v {4}
H
STAR
0
.
2
5
using the TPC
v {4} (ST
AR)
E
0
1
3
4
5
PHOBOS
er.
0
.0
6
i 2
.2
10%-20%0
p(G
e
V
/c
)
(
b
)
t
O
PHENIX
for differe
nt 20%-30%
f0.15
0
.2
5
semi-central
echniques. In 30%-40%
0
.0
4
O
-0
.0
2
NA49
f
.1 f
(STAR)
and4-particle 10%-20%0
N
CERES
0
.2
(STAR)
0
.
0
2
ALICE
v2f4g. To cal- 20%-30%
0
.0
5
M
-0
.0
4
i f
i
STAR E877
new fast and 30%-40%(STAR)
0
.1
5
A
0
1
3
4
5
PHOBOSEOS
2f4gmeasurei 2
p(
G
e
V
/c
)
(
b
)
PHENIX
f
N
ctuations and
0
.2
5
-0
.0
6
E895
0
.1
0
.0
2
NA49
the initial geA
f
CERES FOPI
0
.2
central
f simulations
f
f
S
0
.0
4
E877
0
.0
5
-0
.
0
8
i f
are negligible
0
.1
5
EOS
T
3
2
ns is positive
1
0
0
1
0
.
0
6
E895 1
1
1
0
0
.1
R
he integrated
0
1
2
3
4
5
FOPI
f f
ution[38] and
F
0
.0
5
0
.0
8
s
(G
e
V
)
p(G
e
V
/c
)f i
N
N
t
wedenoteby
3
2
4
I
1
0
1
0
1
0
1
1
0
n addition to
0
1
2
3
4
5
E
FIG.we
2 a(color
online). (a) v2ðpt Þfor the
centrality
bin 40%– FIG. 4 (color online). Integrated
esults
lso
s
(
G
e
V
)
fi
p(
G
e
V
/c
)
N
N
elliptic
flow
at
2.76
TeV
X
aring
to corre
50%
from- the 2- and 4-particle cumulant methods
i f for this Pb-Pb 20%–30% centrality class compared with results fr
f
p
f
i
f
f
i
f
ff
i
&
i – FIG. 4 (color online). Integrated elliptic flow at 2.76 TeV in C
gecorre
lations and
FIG. 2 (color online). (a) v2ðpt Þfor the centrality bin 40%
measurement
for Au-Au collisions at sNNnt¼m200
GeV.
50% from the 2- and 4-particle cumula
ethods
f
for
this
i
weak decays,
i
RHIC
p fiffiffffi mea- lower
;
taken
atlity
similar
[40,43].
Pb-Penergies
b 20%–30%
centra
class centralities
compared (+0.3
with
results
from
' )1 =2NE
vla
f4gðpt Þfor
compared
vHO&
meavarious
surement centralities
and for Au-Au
collisionsto
at STAR
sNN ¼ 200 GeV. i
2tions
er (b)
corre
2
LbE
i
;
T
f mea- lower energies taken at similar centralities [40,43].
(b)data
v2f4g
ðpt Þforin
vathe
rious20%–30%
centralities compa
red tobin
STAR
points
centrality
are
an surements.
like charge The
f re
surements. The data points in the 20%–30% centrality bin a
ff
shifted
inI pt for
visibility.
;
shifte
d
in
p
for
vis
ibility.
;
I t
y class 40%–
252302omparison, we
2
40%-50%
2
40%-50%
v
2
v
2
v2{4} (STAR)
v
2
v
{
4
}
2
v
2
2
10%-20%
t
20%-30%
30%-40%
v
{
4
}
2
10%-20%(STAR)
20%-30%(STAR)
30%-40%(STAR)
! &] 9( G) *95"R&<&k09v :( &d#56l &#++9E( %&#"&"/( &01 2&@F&>CG#+C&!/$
< Q!
&] 9( &
G
)( *9
5"R&<*+&
&k09
v :(
&d#56l
&
#++9
E( 7Q@
%&#"&
"/
( &01%2&
@F&>CG#+C&
! /Lb$+F#A
2*::(
B4E(
@
/#E9
*@
%
(
+E(
C&
9
5&
Q@
&
B*::9
9
*5%
&
#"&
01
2&
HO&E
• ,Collective
behavior
observed
in
Pb-Pb
collisions
at
LHC
H 2*::( B4E( &@( / #E9*+&*@%( +E( C&95&Q@7Q@&B*::9%9*5%&#"&01 2&
&
E L) –>N&%
9?L) 9:#+&
' 1"*&
=2&
#:?
*%*%
"&9"&
C(
rr $9
C&
#"&
2&
behavior
Eideal
Nfluid
&%9?"*&
9:#+&
' 1p&
=2&
p&#:?
9C(#:&
#:&
$9C&
#"&
0101
2&
q&q&
hydrodynamical
evolution
;Testing
H&[ ( G &9i"*&
5)
$"&
5( +6F&
C(
( 5C(5B(
5B( &
&
*D&
B*::(
&r *G
&
& maximumvalueinthe50%–60%and40%–50%centrality
( •G&
"/("*&
&("/5(( &(+6F&
C(
) ()5C(
*D
&
B*::(B4E(
B4E(
&r *G&
f 95) $"&
• fofOH
Precision
measurement
for
viscosity/entropy
ratio
&
<
CC9
4*5#:&
"+#9
*5&
>s
7
8
D
7!
"#"(
&
#5C&
"+#5%
) *+"&
) +*)
( +4(( %
&& %
class
0:106
0:001ð
statÞB*5%
0:004ð
systÞ5"%
and &
0:087
&<CC94*5#:&B*5%"+#95"%&*5&>s 78 D7! "#"( &#5C&"+#5%
) *+"&
) +*)
+4(
samece
f ntralGeV, indicated
f
of v2ðpt Þdoes
t
i
f
maximumva
lueinthe50%
–60%and40%–50%centrality
f
class of 0:106 0:001ðstatÞ 0:004ðsystÞ and 0:087
0:002ðstatÞ 0:003ðsystÞfor the 2- and 4-particle cumu-
Hard Processes to Probe the Medium
• initial parton-parton scattering
with large momentum transfer
– calculable in pQCD
• particle jets follow direction of
partons
 nucleus-nucleus collisions
 hard initial scattering
 scattered partons probe
traversed hot and dense
medium
 ‘jet tomography’
Medium modification quantified via
nuclear modification factor RAA
Charged Particle RAA
Pb-Pb
pp reference
pp reference extrapolated beyond pT>30 GeV
• change of slope beyond pT>40 GeV
• decreasing dependence centrality and pT
with increasing pT
• up to 20 GeV comparable to RHIC
Heavy Quark RAA: D-Mesons
• RAA prompt charm ≈ RAA pions
for pT > 5-6 GeV
• RAA charm > RAA p for pT < 5 GeV ?
(p+ + p) RAA
• Qualitative expectation:
RAA Charm > RAA Mesons
– DE gluon > DE quark (Casimir factor)
– DE massless parton > DE massive
quark ('dead cone')
J/Y Suppression: Ingredients
7 TeV pp J/Y → mm
7 TeV pp 4 LHC expts
pp J/Y Cross Section
Atlas
7 TeV
CMS
e+e-
2.76 TeV
mm
LHCb
2.76 TeV pp
PbPb
J/Y cross section ds/dydpT
7 TeV & 2.76 TeV
agreement with pQCD
ALICE≈ATLAS≈CMS≈LHCB
(in region of overlap)
QM2011 J. Schukraft
For details: C. Hadjidakis, Th, 18:00
0-10%
Heavy Quark RAA – J/ψ
• Rather small suppression
for inclusive J/ψ production
• little centrality dependence
The Future
• 2011
– Pb-Pb at higher luminosity (~1.4x1026 cm-2s-1)
3.5 TeV at intermediate (200ns) or nominal (100ns) bunch
spacing
– Feasibility test for p-Pb running scheduled
• 2012
– Either p-Pb/Pb-p or further Pb-Pb running
• 2013/14
– Shutdown
• pp, p-Pb and PbPb at top energy
– Shutdown
• d-Pb and lighter ions
Conclusions
• Detector performance according to (and
exceeding) specifications
• pp reference well measured
• Fireball at LHC larger and longer-lived wrt RHIC
• Confirmed very low viscosity of QGP
• Now on to quantitative determination of η/s
• Strong leading hadron suppression found out to
very large pT
• Heavy quark energy loss similar to light partons
• ALICE is ideally suited to measure total cross
sections for heavy quarks