ALICE ZDC STATUS REPORT

1
ALICE ZDC STATUS REPORT

• Responsabilities shared by
• Universita del Piemonte Orientale, Alessandria,
  Italy
• INFN-Cagliari and Universita di Cagliari, Italy
• INFN-Torino and Dipartimento di Fisica
  Sperimentale, Universita di Torino, Italy

• Summary
• Activities in the year 2003
• Construction of the second neutron Zero Degree
  Calorimeter (ZN2)
• Test at the CERN SPS with positive hadrons,
  positrons and 115In
• beam
• Test results
• Planning for the year 2004
• Construction of the first proton Zero Degree
  Calorimeter (ZP1)
• Test of ZP1 with hadron and electron beams at
  SPS
• Integration of ZDCs in the LHC tunnel (design
  of the support platform)

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ZDCs for the ALICE experiment
The ZDC detector is made by two sets of
calorimeters, each one composed by 2 hadronic
spaghetti calorimeters, 1 for spectator
neutrons (ZN) and 1 for spectator protons (ZP),
placed at 0 with respect to LHC axis, at about
116 m from the Interaction point where the beam
pipes are separated. They will provide the number
of spectator nucleons in the collision (Nspec
EZDC/EA) a forward EM calorimeter placed at about
7 m from I.P., covering the pseudorapidity range
4.8 lt h lt 5.7.
VACUUM CHAMBER
D1 DIPOLE SEPARATOR
QUADRUPOLES
EM ZDC
NEUTRON ZDC
PROTON ZDC
INTERACTION POINT
DIPOLE CORRECTOR
XY2001
7 m
116 m
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ZN2 for ALICE
The second calorimeter (ZN2) for ALICE was built
in June 2003 and tested with positive hadron,
positron and 115In beam at CERN SPS in autumn
2003.
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ZN for ALICE detector description
Passive material W alloy 93.5 W, 6.5 Ni-Fe,
? 17.6 g/cm3 44 grooved slabs, each of them
1.6 mm thick, stacked to form a parallelepiped
7x7x100 cm3.
Active material quartz fibers pure silica
core, silica fluorinated cladding, and a
hard polymer coat with a diameter of 365, 400,
and 430 ?m, respectively. The numerical aperture
is 0.22.
PMT 1 PMT 2 PMT 3 PMT 4 PMT c
The active part of the detector is made of 1936
quartz fibers embedded in the absorber with a
pitch of 1.6 mm. The fibers are placed at 0? with
respect to the initial particle direction and
come out from the rear face of the calorimeter.
One every two fibers are sent to a single
photodetector (PMTc), while the remaining fibers
are connected to four different photodetectors
(PMT1 to PMT4), collecting the light from four
towers. The chosen PMT is the Hamamatsu R329-02,
with quantum efficiency around 25.

• detection of the beam position
• redundant information

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Beam test at SPS experimental set-up

• Scheduled test beam period (12 days) at SPS H6
  beam line in July-August 2003 almost completely
  lost due to SPS vacuum problems
• Only 4 days recovered in September
• ZN2 was tested at CERN SPS in autumn 2003 with
• positive hadron beam ( E 50 150 GeV )
  at H6 beam line
• positron beam ( E 50 150 GeV ) at H6
  beam line
• 115In beam ( E 158A GeV ) at H8 beam line
• ?
• E 18.2 TeV equivalent to a central
  collision in ALICE (67 nucleons)

- S1, S2, S3, S4 plastic scintillators to
provide trigger - MWPC multiwire proportional
chamber to define impact point on
the ZN2 front face - MU1, MU2 plastic
scintillators to detect muons In the beam test
with 115In the MWPC, MU1, MU2 and the iron wall
have been removed
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ZN2 beam test results pions and positrons
ZN2 response to 120 GeV pion beam
ZN2 response to 120 GeV positron beam
Fit to data
where
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ZN2 beam test results linearity
ZN2 response shows a linear behavior as a
function of p and e beam energy in the range
from 50 to 150 GeV.

• ZN2 is not compensated
• This fact does not create any problems
• for using the detector in ALICE
• ZN measures the number of spectator neutrons,
  which have the same fixed energy as the beam
  nucleons.
• ? background is less than 10.

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ZN2 beam test results energy resolution
The black solid lines are the results of the
fit
Extrapolation to the ALICE neutron spectator
energy (2.7TeV)
Fulfills the ALICE requirements (TDR)
E 18.2 TeV equivalent to a central collision
in ALICE (67 nucleons)
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ZN1 - ZN2 comparison

• ZN1 tested in 2002
• with PM XP2020
• ZN2 tested in 2003
• with PM Hamamatsu R329-02
• improved coupling fibres-PM

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ZN2 beam test results 115In beam
ZN2 response to 158A GeV 115In beam
Energy resolution ?E/E (2.87?0.01)
N independent nucleons where
and from pion beam results
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ZN2 beam test resultslinearity as function of
number of spectators (1)
Central collision
spectators
12C 27Al 63Cu 119Sn
ZDC
participants
115In
115In
spectators
Projectile nucleus B
Target nucleus A
Central collision
Geometric approximation Nucleus rigid sphere
with uniform nucleon distribution
For central collisions
?
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Beam test resultslinearity as function of
number of spectators (2)preliminary
ADC spectrum for 115In 119Sn after pedestal
subtraction and calibration

• Analysis procedure
• Background subtraction (interaction in air)
• Fit of the end point of the spectra (with a
  gaussian)
• Calculation of the energy per participant from
  the end point of the Sn spectrum
• Correction for the participant energy for all the
  targets

Peripheral events
Central events
115In
Ezdc(e.p.) End point
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ZN2 beam test resultslinearity as function of
number of spectators (3)preliminary
Al
Sn
end point
end point
for central collisions 115In 119Sn Npart115
and Nspec0 Epart Ezdc(e.p.)./ 115 Espec 0
for central collisions 115In 27Al Npart 59
and Nspec 56 Espec EZDC(e.p) Npart
Epart where Epart is found with the Sn target
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ZN2 beam test resultslinearity as function of
number of spectators (4)preliminary
Espec EZDC(e.p.) NparEpar as a function of
number of spectators for all the targets Espec
for the 119Sn 0 from our assumptions
Preliminary fast and simple data analysis show a
linear behavior of the ZN response as function of
the number of incident nucleons
12C
115In beam
27Al

• Approximations
• Calculation of Nspec
• Evaluation of Epart
• Determination of end point
• of Ezdc spectrum

63Cu
119Sn
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ZDC integration in the LHC tunnel
VACUUM CHAMBER
NEUTRON CALORIMETER

• New design of vacuum chamber from D1 up to ZDC
  location
• checked with simulation
• Interaction between ZDC (used as luminometer in
  Pb-Pb) and luminometer used in p-p (proposed by
  BDI group)
• New design of the TDI (25/2/04)
• (removable collimator)
• To be checked with simulation
• Proposal for new collimators
• (TCDD,TCLI,TCT)

PROTON CALORIMETER
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ALICE ZDC Planning
ZDC activities up to the installation
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ZDC Milestones

• Construction of ZP1 May-June 2004
• Test of ZP1 at SPS July-August 2004
• Construction of ZP2 October 2005
• Construction of ZEM December 2005
• Test of ZP2 and ZEM first half 2006
• Installation into the tunnel second half 2006

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Summary

• ZN2 has been built and tested
• Detector performances according to expectations
• and the ALICE requirements
• Similar performances of ZN1 and ZN2
• Construction of ZP1 will start in April 2004
• Absorber will be machined (in Torino) and quartz
  fibres will be cut and polished (in Cagliari)
• Assembly of ZP1 to be done in May-June at Cern
  (Bld.167)
• The definitive project of the vacuum chambers
  from D1 up to the ZDC location has started
  together with the design of the support platform
• close interaction with CERN engineers to check
  different solutions and minimize material budget
  in front of the calorimeters