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					             The V0 detector
   A device of the Forward Detector System
   V0, a detector with a central role to ALICE
•   Minimum bias trigger: p-p et Pb-Pb
•   Two centrality triggers: Pb-Pb
•   Background filter for the dimuon spectrometer
•   Luminosity control
•   Multiplicity measurement
   Description of the V0R array
   Test results and plans
   Conclusion


                      V0, jyg, mont dore 2002       1
         Forward detector overview
   Si-FMD (NBI, INR)
•   Forward Multiplicity Detector
•   Si-strip counters with 25600 channels
•   -5.1 < η < -1.7; 1.7 < η < 3.4
   T0 (Jyvæskyla, MEPhI, INR, Budker, Kurch.)
•   Vertex detector by fast timing (σ=50 ps)
•   2 arrays of 12 Cerenkov radiators + PM
•   -5.0 < η < -4.5; 2.9 < η < 3.3
   V0 (IPNL, Mexico)
•   Minimum Bias + Centrality Triggers
•   Background rejection

                             V0, jyg, mont dore 2002   2
                  The V0 localization
   V0 in both sides of the vertex
   V0L at –3.5 meters
•   -5.1 < η < -2.75
•   4.3 < R < 44.5 cm
   V0R at 0.9 meter
•   On the front absorber
•   1.7 < η < 3.8
•   4.0 < R < 33.6 cm




                               V0, jyg, mont dore 2002   3
Integration in ALICE




      V0, jyg, mont dore 2002   4
                 CERN Maquette 1:1
                                                             V0R
                                                       T0R




Absorber              Si inner
           Si outer
                             V0, jyg, mont dore 2002           5
V0R/T0R cut view




    V0, jyg, mont dore 2002   6
      View by Euclid

                Optical fibers




V0R                            Absorber




         V0, jyg, mont dore 2002          7
Euclid at the vertex




      V0, jyg, mont dore 2002   8
                   V0 segmentation
   Each array has 72 detectors according to 5 rings
•   Rings 1-4: 30° sectors (12)
•   Ring 5: 15° sectors (24)
   V0L
•   Maximum coverage allowed by the PMD
   V0R
•   In the FMD acceptance
•   Rings 1-3: in the dimuon arm acceptance




                              V0, jyg, mont dore 2002   9
 Coverage of the rings

                   V0L                                  V0R
Ring
       Rmin/Rmax    ηmax/ηmin/Δη            Rmin/Rmax    ηmax/ηmin/Δη

 1      43/69      -5.1/-4.6/0.47             40/60      3.8/3.4/0.42
 2     69/110      -4.6/-4.2/0.47             60/92      3.4/2.9/0.42
 3     110/174     -4.2/-3.7/0.46            92/141      2.9/2.5/0.42
 4     174/276     -3.7/-3.2/0.46           141/216      2.5/2.1/0.42
 5     276/445     -3.2/-2.8/0.47           216/336      2.1/1.7/0.42


                         V0, jyg, mont dore 2002                        10
Dimensions of the V0R elements


       Ring 5




       Ring 1




                V0, jyg, mont dore 2002   11
          V0 scintillator element
   Elementary channel
•   Plastic Scintillator
•   Wave Lenght Shifting fibers in groove
•   Clear optical fibers for light transport
•   Photomultiplier
   Present tests in laboratory and in beam:
•   Optimization of the light in PM
   choice of scintillator, fiber, reflector, …
•   Time resolution measurement
   about 1 ns expected
•   (x,y) impact dependence of light and timing


                          V0, jyg, mont dore 2002   12
Scint./fiber assembling




       V0, jyg, mont dore 2002   13
V0R sector




 V0, jyg, mont dore 2002   14
V0R sector cut view




      V0, jyg, mont dore 2002   15
               Trigger by the V0
   Level 0 trigger provided with fast electronics (25 ns)
   Signal dynamics: 1 - 1000
•   For a dynamics of 1- 300 MIP’s (expected in Pb-Pb)
•   And a 1 MIP efficiency > 97% (required for pp)
   PM signals from anode and last dynode (A/D = 6)
   Pipe-line technique for conversion (charge and time)
   Three trigger signals to the CTP
•   One MB in pp and Pb-Pb
•   One central and one semi-central in Pb-Pb



                          V0, jyg, mont dore 2002            16
Electronic diagram

                                  MB trigger




                                       CTP




                               Centrality triggers




     V0, jyg, mont dore 2002            17
           Tests in T10 in 2001
   Light from one MIP through elements of the rings 1, 2, 3
   Fast scintillator from BICRON (BC408)
•   425 nm maximum emission, 2.1 ns decay constant
   Optical glue for embedding the fibers (BC600)
   Reflector paint as envelope on scintillator and fiber ends (BC620)
   Shifting fibers directly on PM XP2020 (Y11 and BCF92)




                          V0, jyg, mont dore 2002                  18
                     First results
 V0R      BC408             WLS                Y11        BCF92        BCF92
Sector    scint.           fibers            1.2 mm      1.0 mm       1.2 mm

         Th. (mm)   nbr.     L. (mm)        p.e./σp.e.   p.e./σp.e.   p.e./σp.e.
           10        5           95                                    16/4.6
Ring 1
           20        5           95          59/11.8      26/6.5       27/6.6
Ring 2     20        5          185           52/9.9      22/5.7
                    11          682                                    31/6.9
Ring 3     20
                     5          310           34/7.1      19/5.5


                            V0, jyg, mont dore 2002                          19
                Tests with cosmics
  Optimization of the light
 • With scintillator envelopes, reflectors on fiber ends, …



                                 Scintillator envelope/fiber end
   Ring 3
Scint./Fibers
                BC620 paint/       Teflon film/          Al sheet/     Al coating/
17.5/1.2 mm
                BC620 paint        Teflon film           Al sheet      Al coating
                 Nb. of p.e.        Nb. of p.e.          Nb. of p.e.   Nb. of p.e.
BC404/BCF92                           35 ± 2              31 ± 3
 BC408/Y11         30 ± 1             67 ± 2              63 ± 3

                               V0, jyg, mont dore 2002                        20
                     Ongoing work
   With scintillator BC408 (BICRON) and shifting fiber Y11 (Kuraray)
•   Coupling without optical glue
•   Light attenuation by connectors
•   Light attenuation by optical clear fiber
   Test of low noise PM R7400P from Hamamatsu
   Electronics specification
   Test of sector(s) in T10 in September 2002 (final choice)
•   V0R as defined in lab.
•   V0L as defined by Mexican teams



                            V0, jyg, mont dore 2002                 21
                    Project plan…
   System baseline design to be decided by June 2002 (ALICE note)
   Electronics development in Lyon and in beam tests → end of 2003
   Tests of sector(s) → end of 2003
•   Response to multi-particles
•   GIF exposure, …
•   Test in real situation (LHC clock) with final electronics
   Construction in 2004/2005




                           V0, jyg, mont dore 2002               22
                  … Project plan
   Construction
•   V0L by Mexico
•   V0R by Lyon
•   Electronics by Lyon
   Final system commissionning → middle 2005
   Ready for installation in early 2006
   Budget in MOU
•   100 KFS, corresponding to the 3 V0R inner rings (dimuon arm)
•   V0 cost will be re-estimated by June 2002
•   Mexico contribution (to be defined)



                          V0, jyg, mont dore 2002                  23
                      Conclusion
   Meeting in Lyon on the V0, March 14-15, 2002
•   Two colleagues from Mexico (mechanics)
•   Engineers from Lyon (electronics)
•   F. Lefèvre (DAQ)
   Requests for the V0 installation
•   Optical fibers as short as possible
    > One rack for PM’s and electronics on the left side (V0L)
    > One rack for PM’s and electronics on the right side (VOR)
        …. and close to the CTP (for timing constraints)
    > The two crates on the same side of the beam pipe


                          V0, jyg, mont dore 2002                 24

				
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posted:2/27/2012
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