Physics at NICA, the view from

1
Physics at NICA, the view from the Institute for
Nuclear Research, Moscow

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NICA round table 6 ?????? 2008 ?. ????, ?????

2
Outline

• Introduction
• Problem of anomalous charmonium
• suppression
• Event-by-Event fluctuations
• Ultraperipheral interactions
• Conclusions

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Charmonium

• 33 years ago discovery of J/?, 21 years ago
  Matsui Satz
• colour screening in deconfined matter ? J/?
  suppression
• ? possible signature of QGP formation

• Experimental and theoretical progress since then
  
  ? situation is
  much more complicated
• cold nuclear matter / initial state effects
• normal absorption in cold matter
• (anti)shadowing
• saturation, color glass condensate
• suppression via comovers
• feed down from cc, y
• sequential screening (first cc, y, J/y only
  well above Tc)
• regeneration via statistical hadronization or
  charm coalescence
• important for large charm yield, i.e. RHIC and
  LHC

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J/? suppression from p-A to Pb-Pb collisions
J/? production has been extensively studied in
p-A, S-U and Pb-Pb collisions by the NA38 and
NA50 experiments at the CERN SPS
Projectile
J/y
Target
J/y normal nuclear absorption curve
NA60 is anomalous suppression present also
in lighter In-In nuclear
systems ? Scaling variable- L, Npart, e ?
5

Comparison of NA50 and NA60 results



An anomalous suppression is presented
already in In-In
The normal absorption curve is based on NA50
results. Its uncertainty ( 8) at 158 GeV is
dominated by the (model dependent) extrapolation
from the 400 and 450 GeV p-A data. ? need p-A
measurements at 158 GeV
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Suppression by produced hadrons (comovers)


The model takes into account nuclear absorption
and comovers interaction with sco 0.65 mb
(Capella-Ferreiro) EPJ C42(2005) 419


In-In 158 GeV
J/y / NColl
nuclear absorption
comover nuclear absorption
(E. Ferreiro, private communication)
Pb-Pb 158 GeV
NA60 In-In 158 GeV
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QGP hadrons regeneration in-medium effects


The model simultaneously takes into account
dissociation and regeneration processes in both
QGP and hadron gas (Grandchamp, Rapp, Brown EPJ
C43 (2005) 91)


In-In 158 GeV
fixed thermalization time
centrality dependent thermalization time
BmmsJ/y/sDY
Nuclear Absorption
Suppression Regeneration
QGPhadronic suppression
Regeneration
Number of participants
Pb-Pb 158 GeV
centrality dependent thermalization time
fixed thermalization time
NA60 In-In 158 GeV
8
Suppression due to a percolation phase transition

Model based on percolation (Digal-Fortunato-Satz)
Eur.Phys.J.C32 (2004) 547.


Prediction sharp onset (due to the disappearance
of the cc meson) at Npart 125 for Pb-Pb and
140 for
In-In
Pb-Pb 158 GeV
NA60 In-In 158 GeV
The dashed line includes the smearing due to
the resolution
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J/? suppression (SPS and RHIC)




J/? yield vs Npart, normalized on Ncoll.
Unexpected good scaling. Coherent
interpretation- problem for theory. Work start
- Karsch, Kharzeev and Satz., PRL637(2006)75
10
Invariant mass spectra (AuAu _at_ 35 AGeV)
Identified ee-
After all cuts applied
All ee- Combinatorial bg ? ? ee-? ? ee-f ?
ee-
p0 ? ?ee-? ? p0ee-? ? ?ee-
Central AuAu_at_35AGeV
Simulated statistics 65k events
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Invariant mass spectra J/? ?' combinatorial
background superevent 4x1010 central AuAu_at_25AGeV
UrQMD events with target 25mkm
J/?
?
Invariant mass spectra of tracks identified as
electrons by RICHTRD with reconstructed
Ptgt1.2GeV/c
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Dielectron J/? simulation
Table corresponds to 4x1010 central collisions
55 hours of beam time of full CBM interaction
range 1 MHz interation rate, 20 centrality Au
beam 10 9 1/sec, target 25 µ
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Counting rate of J/? production
35 AGeV CBM L1029 640 1/hour
v s 8AGeV MPD L1027 30 1/hour
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Segmented target
Target 25 mkm for J/? S/B 12 visible ?
' - more time to yield statistic
Target 250 mkm for J/? S/B 1 ?' are not
visible

Segmented target 5 x 50mkm
-7 -3.5 0 3.5 7 cm
300µm
beam
2.5
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Invariant mass distribution of background
electrons with Ptgt1GeV originated in target
Target 250mkm
Target 5x50mkm
Target 1x50mkm
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2. Event-by-event fluctuations

• Total multiplicity Ns-
  number of sources,
• mi-
  multiplicity from a single source.

Geometry of collision
physics! QGP?
Second component is not interesting and must be
removed
Number of interacting nucleons must be known
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ZDC geometry.
Z
Transverse sizes 1x1 m2 Distance from target -
15 m Number of modules 107 Module dimensions
10x10x1600 cm2
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Design and readout
Modular Lead/Scintillator sandwich compensating
calorimeter. Sampling
ratio PbScint41. Expectation For thickness
dPb16 mm and dScint4 mm sE/E 50/vE .
Conception Light readout with WLS-fibers for
reliable and uniform light collection. Signal
readout with Micropixel APD (MAPD) to avoid
nuclear counter effect, detection of a few
photons signal, compactness, low cost.
Longitudinal segmentation for permanent
calibration of scintillators in radiation hard
conditions, rejection of secondary particles.
Modular design transverse uniformity of
resolution, good reconstruction of reaction
plane, flexible geometry, simplicity.
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Measurement of centrality

• Impact parameter bNp ,
• Np is number of interacting (participant)
  nucleons.
• NpA - NspectA - Es/EA ,
• Es is sum of spectator energies, measured by Zero
• Degree Calorimeter (ZDC)
• EA is beam energy.
• This technique is used in most heavy ion
  experiments at CERN (WA80, NA49, NA50, ALICE)
  and RHIC.

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Reconstruction of Reaction Plane
? ? M rk rk
position vector Q ? ----- , of the
particle k k1 ? in
perpendicular rk to the
beam axis plane
M particles in the event
used for reconstruction
Input UrQMD reaction plane at 00
Good accuracy is due to fine transverse ZDC
granulation. To be improved by
taking deposited energy weights.
21
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22
?????? ????????????? ??????? ? ???????
?????????????? ???????????????? ?? b
23
?????? RELDIS Relativistic ELectromagnetic
DISsociation

• (???,1995-2008,?.???????,?.????????? )
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  ???? ?????? SMM ??????????? ????????? ????????
  ? ????????? - ??????? - ??????????????????

24
?????????? ?????? ??? ???? ??????? ?????????? ?
????????? ???????????
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????????? ? ??????????? 1-2
?????????? ??????? 98-99
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25
??????? ????????? ? ???????????????? ???????????
???? ?????? ? ??????
????????????? ?????? 10-30 b
????? ????? RHIC LHC 100-200 b
??? ??????????? geff 2g2beam-1, ??? LHC
1.7107
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Schematic view of experimental setup for forward
neutron emission measurements for 30 A GeV Pb
ions _at_ CERN SPS
S0, S1, SS plastic scintillator detectors.
MBPL and MBPL - Magnets
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Energy spectra of the neutron calorimeter in
proton and Pb runs
1n
ADC spectrum for 30 GeV protons
2n
3n
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New dataforward neutron emission measurements
for 30 A GeV Pb ions _at_ CERN SPS
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Latest dataforward neutron emission
measurements for 158 A GeV In ions _at_ CERN SPS
1n
2n
3n
4n
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Conclusions

• 1. Measurement of charmonium production
• at MPD NICA is possible
• 2. For event-by-event physics the development
  of
• ZDC is indispensable
• 3. Electromagnetic interactions at NICA
  energies
• will provide new insight to nuclear
  structure