Transcript Slide 1

News from ALICE
Jan PLUTA
Heavy Ion Reaction Group (HIRG)
Warsaw University of Technology
July 20, 2015
XIII GDRE Workshop, SUBATECH,
Nantes
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Technologies:18
Tracking: 7
PID:
6
Calo. :
5
Trigger, Nch:11
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July
20, 2015
Detector:
Size: 16 x 26 metres
Weight: 10,000 tons
XIII GDRE Workshop, SUBATECH,
Nantes
Collaboration:
> 1000 Members
> 100 Institutes
> 30 countries
ALICE web page
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ALICE - PHYSICS WORKING GROUPS
PWG-PP Detector Performance
PWG-CF Correlations Fluctuations Bulk
PWG-DQ Dileptons and Quarkonia
PWG-HF Heavy Flavour
PWG-GA photon and pion working group
PWG-LF Light Flavour Spectra
PWG-JE Jets
PWG-UD
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Ultraperipheral, Diffractive
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1) PWG-CF Correlations Fluctuations Bulk
v2(pt) for the centrality bin 40-50%
from the 2 - and 4-particle cumulant
methods for this measurement and
for Au-Au collisions at 200 GeV.
b) v2{4}(pt) for various centralities
compared to STAR measurements.
No flow contributions to v2{4}
are negligible
Contribution from flow
fluctuations is positive for
v2{2} and negative for v2{4}
Value of v2(pt) does not change within uncertainties from 200 GeV to 2.76 TeV
The transverse momentum dependence is qualitatively similar for all three
centrality classes.
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Elliptic flow integrated over the
Pt range 0:2 < pt < 5:0 GeV/c,
as a function of event centrality
The larger integrated elliptic flow at the LHC is caused by the
increase in the mean pt.
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Integrated elliptic flow at 2.76 TeV in Pb-Pb 20-30% centrality class
compared with results from lower energies
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Anisotropic flow of charged hadrons, pions and (anti-)protons measured
at high transverse momentum in Pb-Pb collisions at √sNN = 2.76 TeV
Anisotropic flow provides valuable information on the particle production mechanism
in different transverse momentum
 pt < 2−3 GeV/c - hydrodynamic model calculations
 3 < pt < 6 GeV/c - flow of the baryons is larger than that of the mesons
 pt > 8 GeV/c - the fragmentation of high-energy partons, resulting from initial hard
scatterings, is expected to play the dominant role.
While traversing the hot and dense matter these partons experience collisional
and radiative energy loss
Due to event-by-event fluctuations of the positions of the participating nucleons inside
the nuclei, the shape of the initial energy density of the heavy-ion collision in general
is not symmetric with respect to the reaction plane and the n may deviate from the
reaction plane
 n ( pt , )  cosn  n 
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Unidentified charged particle v2, v3, and v4 as a function of transverse momentum
for different centrality classes.
WHDG model calculations for v2 of neutral pions including collisional and radiative energy loss of partons
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Unidentified charged particle v2, v3, and v4 integrated over the transverse
momentum range 10 < pt < 20 GeV/c as a function of collision centrality
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v2 (top) and v3 (bottom) of charged pion
and proton as a function of transverse
momentum for 10-50% centrality class
compared to unidentified charged particles
results from the event plane method.
Particle type dependence, which is typical
at low pt, persists out to high transverse
momenta.
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2)
Particle-yield modification in jet-like
azimuthal di-hadron correlations in
Pb–Pb collisions at psNN = 2.76TeV
Distributions of central and peripheral
Pb–Pb collisions compared to that of pp
collisions.
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Yield ratio IAA for central (0-5% Pb–Pb/pp) and peripheral (60-90% Pb–
Pb/pp) collisions using the three background subtraction schemes
In central collisions, on the
away-side - a suppression
is observed as expected from
strong in-medium energy loss.
On the near-side, a significant
enhancement is observed
for the first time.
Yield ratio ICP
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Charged particle RAA
Difference of peripheral and central seen in pt distributions
Stronger parton energy loss in central collisions compared to RHIC
Clear increase for pT > 7 GeV/C !
Not observed in RHIC
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PLB 696, 30 (2011)
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Particle ratios – from RHIC to LHC
STAR, PRC 79, 034909 (2009)
PHENIX, PRC 69, 03409 (2004)
BRAHMS, PRC 72, 014908 (2005)
At LHC particle-antiparticle ratios at mid-rapidity are
compatible with 1, as expected.
No centrality dependence was observed
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 μB ~ 0
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Strangeness enhancement
July 20, 2015
Strangeness enhancements with respect to pp collisions
increases
following
hierarchy of strangeness content
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The future
● 2012: p-Pb and Pb-p
initial state effects, shadowing, nuclear absorption, ...
● 2013-14: LHC long shutdown 1
● 2015-17: FULL ENERGY !!
pp @ 7 TeV, Pb-Pb @ √sNN = 5.5 TeV
● 2018: LHC long shutdown 2
● ≥ 2019: HIGH LUMINOSITY → 50 kHz Pb-Pb collisions
LHC experiment upgrades to cope with the higher rates!!
New vertex detectors
Faster readout, pipelining, high level triggers,
TPC with continuous readout ...
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Wait much more from Alice
in future
JP
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