The RPD and its numerous Thresholds

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The RPD and its numerous Thresholds 1 for
the trigger to select the  good  protons
low Threshold high Threshold 2- for
the ReadOut of TDCs with Thr1 and Thr2 ?
good timing resolution ? first analysis
with reasonable efficiency
These 2 kinds of Threshold have to be independent
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1- the proton trigger

• Online 2001 ? Beam
• 2?108 ?/spill of 5s

protons
e-?
EA gt SAHigh and EB gt SBLow or
EA gt SALow and EB gt SBHigh
SADOWN ? SAUP gt SAHigh and SBDOWN SBUP gt
SBLow
or SADOWN ? SAUP gt SALow and SBDOWN SBUP
gt SBHigh
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Distribution of energy losses in A and B for
protons and pions from 50 to 90 deg
Predicted thresholds SALow /SBHigh and SBLow
/SAHigh 52mV/52mV
26mV/1000mV Applied thresholds 30mV/60mV
30mV/60mV Low thr30mV High
thr60mV -- no limit for fast protons The MIP
are not cut (Guillaume, Kasia) -- no limit for
low protons
4V

SAH 1V
SAL 52mV
Detection of protons at minimum energy loss
1 MeV in A 2 MeV in B (?0.26 MeV 52 mV)
SBL 26mV
4V
Attenuation factor (?0.7,?LA0.50m, ?LB1.06m)
SBH 52mV
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trigger scheme and ToF measurement
Splitter 4413
SADC
TDC
Aido
S1
S2
FPGA
Coincidence OR
CFD-LowTh
test
4413-HighTh
AiL B2iH
SADC
TDC
Aiup
S1
trigger
Ai B2i
TDC
S2
4413-LowTh
test
AiH B2i L
4413-HighTh
12?3?2 COINC
SADC
TDC
B2ido
S1
TDC
S2
analogic sum
4413-LowTh
test
B2ido B2iup
4413-HighTh
B2iup
TDC
S1
TDC
S2
SADC
test
1-Proton Trigger SA_downLow (CFD) / S Low
(4413) / S High (4413)
30mV / 30mV / 60mV 2-TDC Time
measurement after S130mV and S260mV
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2. The ReadOut with SADC and TDC with Thr1 and
Thr2
EB
run69851 DT0?RPDBTveto raw analysis
Mult_A1
?
Obtained with a chunk of 1Gb Mult_A1 (to
suppress background
Guillaumes work) But which efficiency ?
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Position and time determination
zB tB
LB
lB
tBdownstream
tBupstreamB
zA tA
tAup A
tAdo
lA
LA
target
Z
zB (tupB - tdownB) (Coruptw Cordowntw) -
(tupB -tdownB) VB/2 LB/2 l B
tB (tupB tdownB) (Coruptw Cordowntw) -
(tupB tdownB)/2 LB/2VB
measured by F1 TDC at a given threshold
constant factors
Correction for the threshold
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Criteria for a ToF measurement
resolution 180ps on A 400ps on B
Time walk corrections
t


Thr1


Thr2
11ns
4.5ns
Methods Time over 2
thresholds ( TDC with Thr130 mV
TDC with Thr260 mV) Amplitude
measurement using SADC
Vmax
V
TDC Threshold as low as possible for a good
timing resolution but not too
low (above the background)
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Efficiency of a raw and quick analysis in COOOL
Tr130mV

• Number of DT0?RPDBTveto events 100
• AiDOWN and AiUP and (BiDOWN or BiUP) 94
• AiDOWN and AiUP and (BiDOWN and BiUP) 89
• Mult_TDC_A 1 79
• Mult_TDC_B 1 52
• Position Z in the scint 43
• MULT_A 1 35

6 ?
5
11
34
17
19
Maybe Thr130 mV and Thr260 mV is a good
compromise
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To be done Strange CFD behavior and the
double peak in the RPD trigger Insertion of our
COOOL in the COMPASS COOOL Booky Insertion
in CORAL and the final analysis Study of
resolution (precise constants determination
and stability)
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Full acceptance for recoil protons with -t gt 0.07
(GeV/c)2
From Andrea
Proton threshold -tgt0.07
Proton threshold -tgt0.07
?, ?e- can be mixed

• can
• be mixed

?, ?e- can be mixed
Easy proton selection
Easy proton selection
From Nicole

• can
• be mixed

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