Osservabili ‘soft’
in ALICE
Quark Matter Italia
Roma, 22-24 Aprile 2009
Luciano Ramello – Università del Piemonte Orientale & I.N.F.N.
for the ALICE Collaboration
Indice


L’esperimento ALICE a LHC
Osservabili ‘soft’ in ALICE:
Molteplicità di particelle cariche
 Flusso direzionato (v1) ed ellittico (v2)
 Spettri in pT, rapporti h/h, B/M, ...
 Risonanze
 Correlazioni HBT
 Fluttuazioni

L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
2
L’esperimento ALICE
Configurazione per le prime collisioni
p-p e Pb-Pb a LHC
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
3
ALICE: dedicated to H.I.
General purpose (as opposed to all SPS and some RHIC expt’s)
• In contrast to LHC experiments mainly devoted to (hard) p-p physics
ALICE is focussed on heavy-ion physics & therefore has:
•
1) Capability of coping with the high multiplicity generated in H.I.
collisions (~2000 charged particles per unit rapidity, designed for 6000)
• Not strictly necessary for selected hard probes (such as ),
but important to access the bulk of particle production, i.e.
to study soft observables
• Implies, in particular:
• High granularity
• Large bandwidth for Data Acquisition system
2) Possibility of pushing down as much as possible its pT reach
•
Implies a not too high B field for momentum measurement
(note: Conflicting requirement with accuracy for hard probes!)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
4
Zero-degree calorimeters
Central barrel
L. Ramello
Muon arm
Quark Matter Italia - Roma, 22-24 Aprile 2009
5
Size: 16 x 26 meters
Weight: 10,000 tons
TOF TRD
HMPID
ITS
PMD
Muon Arm
PHOS
ALICE
L. Ramello
TPC
Quark Matter Italia - Roma, 22-24 Aprile 2009
Added since 1997:
-V0/T0/ACORDE
- TRD (’99)
6
- EMCAL (’06)
ALICE configuration at start-up

Complete - fully installed & commissioned:


Partially completed:






ITS, TPC, TOF, HMPID, MUONS, PMD, V0, T0, FMD,
ZDC, ACORDE, TRIGGER, DAQ
TRD (20%) to be completed by 2009
PHOS (40%) to be completed by 2010
EMCAL (0%) to be completed by 2010/11
HLT (High Level Trigger) (~50%)
At start-up full hadron and muon capabilities,
Partial electron and photon capabilities
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
7
ALICE Detector Installation Goal 2009
Complete:
ITS, TPC, TOF, HMPID,
FMD, T0, V0, ZDC,
Muon arm, Acorde
PMD, Trigger, DAQ
ALICE Status
2008/09 Shutdown
used for additional
installation and repairs
Partial installation:
PHOS(3/5)
6-8/18 TRD
2-4/6 EMCAL
~ 50% HLT
P. Kuijer
QM 2009
P. Kuijer
Number of TRD & EMCAL modules depends on access conditions during LHC power test !
8
Alice tracking performance
• Central barrel tracking: ITS + TPC + TRD
• Robust, redundant tracking from < 100 MeV/c to > 100 GeV/c
• Very little dependence on dNch/dy up to dNch/dy ≈ 8000
TPC acceptance = 90%
drop due to
proton
absorption

dNch/dy=6000
Momentum resolution
~ 5% @ 100 GeV
p/p < 5% at 100 GeV with careful control of systematics
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
9
Alice particle identification
 ‘stable’ hadrons (π, K, p): 0.1<p<5 GeV/c; (π, p with ~ 80 % purity to ~ 60 GeV/c)
 dE/dx in silicon (ITS) and gas (TPC) + time-of-flight (TOF) + Cherenkov (HMPID)
 decay topologies (K0, K+, K-, Λ, cascades, D)
 K and Λ decays beyond 10 GeV/c
 leptons (e, μ ), photons, π0
 electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π0 in PHOS: 1<p<80 GeV/c
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
10
Cosmic event with SPD trigger
Probably a
muon
interaction in
the magnet’s
iron
about 350
tracks
reconstructed
in TPC
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
11
Cosmic event with ACORDE trigger
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
12
p beam in ALICE
LHC pilot beam at 450 GeV: p-Si
collision in the SPD (Sept. 12, 2008)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
13
Breve introduzione:
cosa ci aspettiamo di imparare
studiando le osservabili ‘soft’ a LHC?
Ovvero: dati i risultati ottenuti a RHIC
c’è ancora qualcosa da scoprire a LHC?
Reminder: space-time evolution
 Thermal
freeze-out
 Elastic interactions cease
 Particle dynamics
(“momentum spectra”)
fixed
Tfo (RHIC) ~ 110-130 MeV
 Chemical
freeze-out
 Inelastic interactions cease
 Particle abundances
(“chemical composition”)
are fixed (except maybe
resonances)
Tch (RHIC) ~ 170 MeV
 Thermalization
time
 System reaches local
equilibrium
teq (RHIC) ~ 0.6 fm/c
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
15
Introduction/1



Initial conditions: measuring dNch/d will be crucial
for evaluating energy/entropy density & confirm (or
reject) the saturation model (Lacey, QM 2009)
Thermo/hydrodynamics of QCD: at T ≥ 400 MeV
(LHC) a new regime should emerge (Wiedemann, QM
2009)
 consequences for v2, HBT correlations, pT spectra
Chemical composition: will statistical models still work
at LHC energy? Measuring hadron yields (& their
ratios) will give the answer (limiting temperature of 160
MeV?)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
16
Introduction/2


Nature of phase transition: at LHC (high T, low B) a
‘crossover’ transition is expected… it should be
verified by studying fluctuations of conserved
quantities (Mohanty, QM 2009), while other
experimental programmes (NA61/SHINE at CERN,
the RHIC Critical Point Search, CBM at GSI) will
explore other regions of the phase diagram
Lesson from RHIC: ‘know your reference’, in our case we will
have collected p+p data before Pb-Pb ones, but it will be
necessary later to collect p-A (d-A) data as well, to understand
cold nuclear matter effects
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
17
Molteplicità di particelle cariche
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
18
Charged multiplicity at the LHC

increasing s – decreasing x
Extrapolation of dNch/dmax vs s:



Fit to dN/d  ln s (limiting fragmentation)…
… or Saturation model (dN/d  s with =0.288)?
Clearly distinguishable with the first 10k LHC events
Central collisions
Models prior to RHIC
Saturation model
Armesto Salgado Wiedemann, PRL 94 (2005) 022002
dN ch / d
N part / 2
2
N part
 8.2 
 0
dNch
d
dN ch
d
 1650
 0
 N 0 s[GeV ]

1
3
N part
 0
Extrapolation of dN/d  ln s:
5500
L. Ramello
dN ch / d
N part / 2
Quark Matter Italia - Roma, 22-24 Aprile 2009
 5.5 
 0
dN ch
d
 1100
 0
19
dNch/d: PHOBOS extrapolation
W. Busza
QM 2009
Au+Au Data from PHOBOS,
Nucl. Phys. A757 (2005) 28
PHOBOS extrapolations to LHC energy, Wit Busza, J. Phys. G35, 044040 (2008):
Total Nch (Pb+Pb √sNN = 5.5 TeV): 15 000 ± 1 000
Mid-rap. dNch/d @ Npart=386 (Pb+Pb √sNN = 5.5 TeV): 1 200 ± 100
Total Nch for inelastic p+p @ √s = 14 TeV (10 TeV): 60 ± 10 (56 ± 9)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
20
Total particle production
PHOBOS: Nucl. Phys. A 757 28 (2005)
E178: PRL34(1975)836
Wit Busza: Acta. Phys. Pol. B35(2004)2873
Similarity of total particle production in
e+e-, pp, πA, KA, pA and AA collisions
“What is the mechanism that makes the
total particle production insensitive to the
intermediate state?”
W. Busza
QM 2009
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
21
Charged multiplicity in ALICE
Reconstructed dNch/d
with tracklets in SPD
(generated dNch/d = 3000)
ALICE PRELIMINARY
T. Virgili
Wide rapidity coverage provided
by ITS (SPD), TPC in the central
region & FMD in the forward region
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
22
dNch/d in p+p: SPD
ALICE PRELIMINARY
dNch/d from tracklets (vertex +
2 SPD layers):
• larger  and pT acceptance
• less stringent calibration/alignment needs
F. Prino
M. Nicassio
QM 2009
Several careful corrections needed to go from
Reconstructed to Corrected dNch/d:
• background
• algorithm + detector efficiency
• geometrical acceptance
… and also:
• vertexing efficiency
• Min. Bias trigger efficiency
L. Ramello
ALICE PRELIMINARY
Quark Matter Italia - Roma, 22-24 Aprile 2009
23
dNch/d in p+p: FMD
The FMD will complement the dNch/d measurement
for -3.4<η<-1.7 and 1.7<η<5
Background correction is most crucial since >50%
of particles crossing FMD are secondaries
ALICE PRELIMINARY
ALICE PRELIMINARY
H.H. Dalsgaard
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
24
Flusso direzionato (v1)
ed ellittico (v2)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
25
Anisotropic flow
Azimuthal asymmetry in coordinate space (transverse plane):
produces azimuthal asymmetry in momentum space:
Kolb + Heinz
The amount of observed flow
depends on centrality and on
the spatial eccentricity :
v1 = directed flow
L. Ramello
v2 = elliptic flow
Quark Matter Italia - Roma, 22-24 Aprile 2009
 
y2  x2
y2  x2
26
Flow and reaction plane
Produced particles’
angular distribution
in the transverse
plane (xy) 
Reaction plane (xz)


The Fourier expansion is referred to the
reaction plane angle (RP) which must be
located in the experiment’s reference frame
The reaction plane angle can be evaluated
at any particular order of the expansion,
using produced particles or even spectators
(e.g. ‘bounce off ’ of spectator neutrons,
which can provide both the first order
reaction plane and the amount of directed
flow v1)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
Figures courtesy F. Prino
27
Directed flow in ALICE

v1 can be measured in ALICE via spectator neutrons (>8.7),
namely by their centroids as obtained by the two zero-degree
‘ZN’ calorimeters
ZP
ZN
7.04 cm

2.76 TeV·A Pb-Pb
minimum bias events
HIJING simulation

For a range of plausible v1
values (10% 20% 30%) at
LHC, the first order event
plane resolution obtained by
combining both ZN’s is quite
adequate
In addition, this measurement
provides the sign of v2
N. Demarco
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
28
Elliptic flow: √s dependence
From the observed v2 dependence on √s
… one expects v2(0) @ LHC/ALICE ~ 0.08
Large signal  easy measurement, but..
beware of non-flow contributions (jets...)!
v2 (elliptic flow) is supposed to scale as
eccentricity  (more on this later);
from hydrodynamics calculations, it appears
that the contribution to v2/ by the QGP
phase (rather than from the cascade) is much
larger at LHC with respect to lower energies
T. Hirano, U. Heinz, D. Kharzeev, R. Lacey,
Y. Nara, QM 2008
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
29
Elliptic flow and eccentricity


The ‘experimental’ definition of eccentricity is tricky: from geometry (Glauber)
or taking into account event-by-event fluctuations in the actual number of
participants?
the Participant Plane (PP) must be distinguished from the Reaction Plane
(RP)
momentum space
coordinate space

A. Poskanzer
QM 2009
v2 fluctuations (in events of the same centrality class) are closely related to
fluctuations of part - which can be computed via Glauber MonteCarlo
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
30
Elliptic flow: different methods


Problem: measurement of v2 is affected by both non-flow and fluctuations
Different methods to extract v2 have been developed, based on event plane,
2-particle or many-particle correlations: they give different results…
published
corrected to PP
STAR, J. Adams et al., PRC 72, 014904 (2005)
A. Poskanzer QM 2009
L. Ramello
… but they agree on mean v2 in Participant Plane!
Quark Matter Italia - Roma, 22-24 Aprile 2009
31
Elliptic flow: one result?
 ‘A v2 for theorists’ (corrected to Reaction Plane):
reaction plane
corrected to RP
Glauber
CGC
Voloshin, Poskanzer, Tang, and Wang,
Phys. Lett. B 659, 537 (2008)
L. Ramello
Still, some dependence on the assumption
(Glauber vs. CGC) about fluctuations
Quark Matter Italia - Roma, 22-24 Aprile 2009
32
What about viscosity?


Relativistic viscous hydrodynamics is making nice progress (see e.g. D. Teaney,
R. Snellings & P. Romatschke at QM 2009), 2nd order theory (with zero bulk
viscosity) is under control
Shear viscosity () reduces v2: comparing hydrodynamics calculations with
RHIC data, with high confidence one can conclude: /s < 0.5 ~6/4
M. Luzum and P. Romatschke, 2008 (erratum 2009)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
33
More on data vs. hydrodynamics

Parametrization of v2/ deviation from ideal hydro:




v2/ = h / (1+B/(1/S· dN/dy)) = h / (1+Kn/K0)
h = ideal hydro limit for v2/
1/S· dN/dy inversely proportional to Knudsen number Kn = /L
(mean free path/system size)
The B parameter scales with
/s but is also sensitive to
the EoS:


STAR data are well described
using a CGC ε with soft EoS
and η/s ~ 2/4π or Glauber ε
with hard EoS and η/s ~ 4/4π
The shift of the peak of v2 as a
function of pT may be an
additional independent way of
extracting /s
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
R. Snellings, QM 2009
34
Elliptic flow in ALICE
ALICE Pb-Pb simulation:
the v2 flow signal (for 3
different extrapolations) is
clearly disentangled from
the non-flow contribution
over a wide range of
centrality (charged
multiplicity).
non-flow ~v2 (Hijing fit)
v2/ε=0.33
g~
~
v2 
hydro
v2/ε=0.22
M sub
LDL
Centrality class
Relativistic hydrodynamics prediction:
v2/ = constant [J. Y. Ollitrault – P.R. D 46 (1992)]
dNch/d =2000
Low Density Limit prediction:
v2/ = const. (1/S)dNch/dy
[Heiselberg, Levy – P.R. C 59 (1999); Poskanzer, Voloshin – P.L. B 474 (2000)]
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
35
Flow: event plane & other methods
event plane resolution (TPC)
vs. v2 for 1000 charged tracks
Reaction Plane
Cumulants
Lee Yang Zeroes
v2 vs pT
for v2 =0.0625
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
36
Flow with inner ITS layers
• SPD alone useful for low multiplicity
events, and has higher acceptance
wrt TPC (low pT threshold ~15 MeV)
• Simulations suggest
• flow for negative and positively
charged particles separately
• coarse pT binning may be
possible
In addition, FMD and PMD will measure flow
at forward rapidities
L. Ramello
Layer 1 ‫׀‬η ‫ < ׀‬2.0
Layer 2 ‫׀‬η ‫ < ׀‬1.4
Quark Matter Italia - Roma, 22-24 Aprile 2009
37
Spettri in pT e rapporti
Composizione chimica,
meccanismi di adronizzazione
Statistical hadronization



Statistical models assume that the hadronic system at freezeout can be
described as a Hadron Resonance gas in chemical and thermal equilibrium,
whose composition (ratios of particle species) follows statistical mechanics
and depends on two parameters: chemical freezeout temperature Tch and
baryonic chemical potential B
Other model parameters such as: fireball volume, I3, S are constrained from
initial state
These models have been remarkably successful in describing hadron yields
ratios up to RHIC - see e.g.: A. Andronic et al., Nucl. Phys. A772 (2006) 167
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
39
Statistical hadronization at LHC

Temperature Tch increases rapidly at low √s, then reaches about
160 MeV at 7-8 GeV and stays constant; chemical potential B
decreases continuously with increasing √s (A. Andronic et al.,
arXiv:0711.0974 [hep-ph])
TLHC = 161±4 MeV
L. Ramello
BLHC=0.8(+1.2,-0.6) MeV
Quark Matter Italia - Roma, 22-24 Aprile 2009
40
Particle spectra in ALICE

Transverse momentum ranges for particle identification in
ALICE (central barrel):
Expected charged hadrons yields for 107 Pb-Pb
central collisions (TPC PID on statistical basis)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
41
Antiparticle/particle ratios
Baryon asymmetry
AB = 2×(p–p)/(p+p)
Phys. Rev. C 77, 061901(R) (2008)
Phys. Rev. C 71, 021901(R) (2005)
ALICE PRELIMINARY
W. Busza
QM 2009
L. Ramello
Systematic error on asymmetry <1.5%
for a 10% material budget uncertainty
P. Christakoglou, M. Oldenburg
Quark Matter Italia - Roma, 22-24 Aprile 2009
42
Identified hadrons spectra (TPC)
ALICE–cosmics
real data
ALICE
simulation
A. Kalweit
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
43
Strange particle spectra
: optimized, pT-dependent selection cuts

L. Ramello

Quark Matter Italia - Roma, 22-24 Aprile 2009
44
How to fit spectra?
Crucial to obtain the total yield (extrapolation down to pT=0: 7-15%
of the yield is not measured directly)
The proposed functional forms include:
 Exponential in mT (Boltzmann)

 Levy
p  m  m 
(n  1)( n  2 )
1 d N
dN

 p 1 


2 dydp
dy 2nC nC  m (n  2 )
nC


 Tsallis blast-wave (power law in
mT)
2
t
2
2
0
n
0
t
t
0
B. Hippolyte, H. Ricaud
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
45
Baryon/meson ratios vs. pT/1
High baryon to meson ratio (~1) at intermediate
pT discovered at RHIC in Au+Au reactions,
inconsistent with pQCD predictions
Sarah Blyth (STAR) QM 2006
Baryon to meson ratio should be sensitive to:
• hadronization mechanism (quark count)
• radial flow of medium (hadron mass)
High B/M ratios may be explained by quark
coalescence, but not uniquely…
Au+Au 200 GeV
62 GeV
Timmins (STAR) QM 2009
L. Ramello
Staszel (BRAHMS) QM 2009
Quark Matter Italia - Roma, 22-24 Aprile 2009
46
Baryon/meson ratios vs. pT/2
−
The ratio (+)/K0 at mid-rapidity in p+p
collisions at RHIC energy is flat and below unity,
while at higher energies (UA1, CDF) it rises
above unity.
−
The maximum value of (+)/K0 at midrapidity in p+p collisions is not reproduced by
PYTHIA.
EPOS (with the mini-plasma option) predicts a
strong increase of this ratio at LHC energy.
L. Ramello
B. Hippolyte, H. Ricaud
Quark Matter Italia - Roma, 22-24 Aprile 2009
47
Risonanze
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
48
Why resonances?
Resonance
r(770)
++(1232)
f0(980)
K*(892)
S*(1385)
*(1520)
ω(783)
(1020)
Life-time [fm/c]
1.3
1.7
2.6
4.0
5.7
13
23
45
• Decay time comparable with (or
even shorter than) QGP lifetime
• Rescattering and regeneration
between chemical and kinetic freezeout will affect the final yields
• Comparing leptonic and hadronic
final states provides further insight
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
49
Resonances at RHIC
P. Fachini QM 2009
Mass shift ~45 MeV/c2 observed
M. Naglis QM 2009
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
50
Resonances in ALICE
Invariant mass reconstruction, background subtracted (like-sign method)
mass resolutions ~ 1.5 - 3 MeV/c2 and pT stat. limits from 8 (r) to 15 GeV/c (, K*)
r0(770)

106 central Pb-Pb
K*(892)0
K
15000 central Pb-Pb
Mass resolution
~ 2-3 MeV
Invariant mass (GeV/c2)
 (1020)
K+K-
Mass resolution
~ 1.2 MeV
Generated & reconstructed
 for 107 central Pb-Pb
ALICE PRELIMINARY
A. Badalà, A. Pulvirenti
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
51
Correlazioni HBT
(Hanbury-Brown Twiss, a.k.a.
Femtoscopy)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
52
No more RHIC HBT puzzle?
RHIC HBT PUZZLE: 1st order phase transition
flow & spectra OK ideal hydro (no viscosity)
HBT radii NOT OK
0=1.0 fm/c
Solution:
Early acceleration (t < 1 fm/c)
Shear viscosity
EoS (crossover)
Initial energy profile
S. Pratt, QM 2009
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
53
Another solution to the HBT puzzle
1) semi-hard EoS
W. Florkowski
WPCF 2008
2) Single freezeout modeled by THERMINATOR
3) Initial conditions: 2-D gaussian in transverse plane,
from Glauber MC
Spectra, v2 and HBT radii well reproduced
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
54
Femtoscopy in ALICE/1
Projected 3-D two-pion correlation
function C2 for
LHC Pb+Pb collisions,
for b=8 fm centrality and
pT bin 0-200 MeV/c
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
55
Femtoscopy in ALICE/2
Anti-merging cut:
Tracks that would be
merged in the TPC if
they were in the same
event have to be removed
from the background
(mixed event sample)
Anti-splitting cut:
here the effect of the cut
on identical K
correlations is shown
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
56
Fluttuazioni
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
57
QCD phase transition / Critical Point
Lattice and other QCD based models :
B = 0  Cross-over transition
TC ~ 170-195 MeV
B > 160 MeV  QCD critical point
B. Mohanty QM 2009
Experiments:
See distinct signatures that relevant d.o.f. are quark and gluons
Tinitial(direct photons) > TC(Lattice) - PHENIX: direct photon arXiv:0804.4168
No signature of QCD critical point established, possible hints at SPS (see C.Hoehne’s talk)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
58
Phase transition at B ~ 0
1st order :
Peak height ~ V
Peak width ~ 1/V
Cross over :
Peak height ~ const.
Peak width ~ const.
2nd order :
Peak height ~ V
T grows with 6/g2, g : gauge coupling
No significant volume dependence (8 times diff. in vol.)
Phase transition at high T and  = 0 is a cross over
See also: Spontaneous strong
Parity violation at RHIC
B. Voloshin QM 2009
B. Mohanty QM 2009
Fluctuations at deconfinement transition visible through:
• Second moment of event-by-event distributions of multiplicity,
mean pT, mean ET after removing non-dynamical fluctuations
• Fluctuations in particle ratios: sensitive to particle numbers at chemical FO (not kinetic
FO), volume effects should cancel
• Fluctuations in conserved quantities: net charge, net baryon number, net strangeness
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
59
Fluctuation results (QM 2009)
Observable
Experiment (Beam energy in
GeV)
Conclusions
K/ and p/
NA49(6.3 - 17.3)
arXiv:0808.1237
M.I. Gorenstein et al,
arXiv:0811.3089
p/ fluctuations : similar results from UrQMD
K/ higher than UrQMD at lower energy
HSD transport gives similar energy dependence
K/ and p/
STAR(19.6 - 200 GeV)
arXiv: 0901.1795
G. Westfall - WWND09
K/ : Statistical hadronisation model (q>1) agrees.
HSD transport model similar results
p/ fluctuations similar to default UrQMD
Observable
Experiment (Beam energy in GeV)
Conclusions
Net-charge
STAR (19.6 - 200 GeV) p+p, Cu+Cu,
Au+Au arXiv:0807.3269
Lie between charge conservation effects and
resonance gas model.
Net-charge
NA49 (6 - 17 GeV) PRC 70,064903
(2004)
Consistent with charge conservation
Net-charge
PHENIX (130 GeV)
PRL 89, 082301 (2002)
Similar to RQMD calculations.
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
60
EbyE in ALICE/1
Particle ratios 
HIJING PbPb events @ √sNN = 5.5 TeV
C. Zampolli
Temperature fluctuations:
generated
reconstructed
protons from a single
HIJING central event:
T = 319±13 MeV
p
300 central events
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
61
EbyE in ALICE/2
The width of the BF was initially proposed
to be related to the time of hadronization.
Balance functions
Two dimensional differential analysis
1 N (y) N (y) N (y) N (y)
B(y)  


2
N
N

Bass, Danielewicz, Pratt PRL 85 2689 (2000)

L. Ramello
P. Christakoglou WPCF 2008 (Cracow)
Quark Matter Italia - Roma, 22-24 Aprile 2009
62
Future explorations
C. Höhne QM 2009
complete scan of the QCD phase
diagram with modern, 2nd generation
experiments on the horizon!
• RHIC beam energy scan
- evolution of medium properties
- “turn-off” of established signatures
- search for CP and PT
• NA61 at SPS (2007 acc. by SPSC)
- search for CP and PT in energysystem size scan
• both essentially limited to high yield
observables
- RHIC: energy dependent
• FAIR and NICA
- new accelerator projects
- FAIR: high intensities! → rare probes!
L. Ramello
30A GeV
Quark Matter Italia - Roma, 22-24 Aprile 2009
63
Protone-protone
Alcuni esempi delle potenzialità di ALICE
con i dati p-p del primo giorno / primo
mese (Ecm = 10 TeV)
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
64
Charged multiplicity
After unfolding
ALICE PRELIMINARY
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
65
pT spectra:  and anti-
Tracking in ITS+TPC
Topological PID (decay vertex)
Gamma conversions partly removed
No correction for absorption
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
66
Resonances
With 100K - a few 100K events:
with PID,  and K* spectra feasible up
to 3-4 GeV
With 1M – a few M events:
 reconstruction feasible without PID,
being studied for K*
Example of “first day”  analysis
with TPC only, no PID
pp 10 TeV
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
67
EbyE particle ratios
M. Fragkiadakis
M. Vassiliou
ALICE PRELIMINARY
Simulated pp data at 10 TeV
ITS, TPC and TOF PID +
combined PID Effic. &
Contamination
K/π and p/π Event-by-Event
particle ratios extracted
 verified that (as expected)
dynamical fluctuations in pp
(PYTHIA) are zero …
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
68
Conclusions




ALICE detectors are installed, apart from full e.m.
calorimetry (due for completion in 2011)
All installed detectors are being commissioned with
cosmic muons: calibration and alignment are well under
way
Analysis procedures have been developed and tested on
the Grid, both for Pb+Pb and p+p first phyiscs
ALICE is well equipped, both detector-wise and
analysis-wise, to produce a wealth of soft physics
results with first p+p and Pb+Pb collisions
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
69
ALICE References

ALICE Physics Performance Report:
Volume 1: F. Carminati et al., J. Phys. G. Nucl. Part.
Phys. 30 (2004) 1517
 Volume 2: B. Alessando et al., J. Phys. G. Nucl. Part.
Phys. 32 (2006) 1295


ALICE Detector technical paper:


K. Aamodt et al., The ALICE Experiment at the
CERN LHC, 2008 JINST 3 S08002.
http://aliceinfo.cern.ch/
L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
70
Many thanks to…

ALICE collaborators, in particular for their
recent presentations/contributions:
Bruno Alessandro
 Panos Christakoglou
 Angela Badalà
 Boris Hippolyte
 Christian Kuhn
 Francesco Prino
 Alberto Pulvirenti
 Enrico Scomparin

L. Ramello
Quark Matter Italia - Roma, 22-24 Aprile 2009
71