Detection Methods and Detectors - GSI Wiki
Transcript of Detection Methods and Detectors - GSI Wiki
Detection Methods and Detectors
Energy Loss
TOF detectors
Gas Detectors
Cherenkov Detectors
Tracking
Dilepton Reconstruction
Range of charged particles
(E. Segrè, Nuclei and particles)
Particle through themedium:
1) Looses energy
2) is deflected
Alpha-particles in air (discovery of the proton)
(E. Segrè, Die großen Physiker...)
( )
2 4 2
2
2 2
0
2ln
4 21
e
e
ee mdE
dx
n
m
z v
v I=Bethe – Bloch formula:
Energy loss of charged particles due to ionisation
Range of charged particles
(aus: C. Grupen, Teilchendetektoren)
Muons in rock: Electrons in various
materials:
Energy loss of various charged particles in air
(C. Grupen, Teilchendetektoren)
Bragg curves
(E. Segrè, Nuclei and particles)
Energy loss of minimum ionising particles
-1 -1 2
min min
-3
Absorber MeVcm MeVg cm( )
Water 2.03 2.03
Xenon (gaseous) 7.3 10
dE dE
dx d x
1.24
Iron 11.7 1.48
Lead 12.8 1.13
Hy -4drogen (gaseous) 3.7 10 4.12
RAW Data
Beam: (1.17GeV/c) Beam: + + p
Counts
Counts
Charge [ADC chan.]
380 keV470 keV
Contributions to the energy loss of muons in iron (C. Grupen, Teilchendetektoren)
Multiple scattering of electrons
(W.R. Leo, Techniques...)
Beam broadening:
Backscattering:
High Acceptance Di-Electron Spectrometer
T. Eberl, TUM –E12
RICH in detail
pad plane
tank
window
mirror
tank shell
target
radiator gas
detector gas
beam
field plane
photon detector
Status 10/01Status 10/01PreShower
Magnet
CoilsRICH
ToF
Heavy-ion collisions atrelativistic energies (1÷2 AGeV)
p
n++
K
p
T 0, B 0
Physics Motivations
Light vector mesons
Probes for nuclear matter
2.9·10-4K+K-441019
7.1·10-5 + - 023783
4.5·10-5 1.3769
Branching
ratio e+e-
Main
decay
Mean life
[fm/c]
Mass
[MeV/c2]Mesons
e+
e-
LEPTONS
NO strong final interaction
Very low probability
Hadron properties inside the
nuclear matter M,
Organic Scintillator
(Leo, Techniques...)
Very rapid fluorescence signal (a few ns) timing
Production of light requires 100 eV per photon (NaI: 25 eV)
< 10 ps
ns
Scintillator – light guide – photomultiplier
(Leo, Techniques...)
Measurement of time-of-flight
(Grupen, Teilchendetektoren)
e.g. also as a veto detector
Photomultiplier tube
(Grupen, Teilchendetektoren)
Quantum efficiency of the photocathode: 10 – 30 %
Amplification: up to 107
The TOF Detector
• 6 x 64 Scintillators
tof : 90-140 ps
• In beam start detector
Diamond, d = 120μm,
t = 66ps
TDCt1 t2
Start-Detektor
Catania (INFN - LNS)
Milano (INFN, Univ.)
Rez (CAS, NPI)
Bratislava (SAS, PI)
2 radiation lengths Pb converter
Field
Sense
wires
Pads
Post1-conv Post2-conv.Pre-conv
Pre-Shower detector side view
TOFINO
Pre-Shower
target
3 pad chambers (20000 pads)
em. showers in Pb converters
beam
tof
measurement
t 0.35 ns
Pre-Shower/TOF system <450
esingle 80%
C+C 1.5 AGeVOne event: detector response
Pre-converter Post1-converter Post2-Converter
Shower
candidate
Pre-Conv
Post1-Conv
Pre-Conv
Post1-Conv
p beam e- beam
Ionisation chamber
(Grupen, Teilchendetektoren)
1 electron – ion pair per w 30eV
: 2.35 , 0.2Fw
Energy resolution R FE
= <
Yield of ions in a gas detector
(Leo, Techniques...)
Multiwire chamber (Charpak)
position sensitivity
Track Reconstruction:
1. Search for Wire Hit
2. Targetprojection
3. Straight-line-fit
Track Reconstruction in the Drift Chamber
Particle ID with the tracking chambers
t2 ~ dE/dx * Corr.
Correct time-above-threshold for track topology.
• Simulation (Garfield)• Use tracking information
Will be exploited for:
• Track matching• Close pair rejection
Momentum Calculation
1. Kickplane-Algorithm
„Impuls-Kick“ on one virtual
( parametrized via Simulations)
2. Numerical Integrations of the
equation of motion.
(„Runge-Kutta: Method“)
Anfangsbed.:
Momentum Reconstruction
0rr
MDC1
MDC2
MDC3
MDC4
( )= )(2
2
lrBdl
rd
p
kq
dl
rd rrrr
0
,,,,
rrdl
dy
dl
dxyxp
rr=
Momentum* charge [MeV/c]
Ve
loc
ity
[c
]
Relative Momentum Resolution with
All tracking Chambers: ~ 3% for p < 800 MeV
tan( ) ~ 1/p
Cherenkov - Effect
> thr =1
n= 1
1
thr
2
cos C =1
n
1
1
n
p = m0v = m
0c
1 m
0c
thr =18
for e : pthr = 0.511MeV /c 18 = 9MeV /c
for pions : pthr =135MeV /c 18 = 2.43GeV /c
Cherenkov-radiators
Material 1 -min -min
solid Sodium 3.22 0.24 1.029
Diamond 2.91 0.26
n
1.034
Flintglas 0.92 0.52 1.17
Water 0.33 0.75 1.52
Aerogel 0.025
-3
-4
- 0.075 0.93 - 0.976 4.5 - 2.7
Pentane 1.7 10 0.9983 17.2
Air 2.93 10 0.9997 41.1
Helium 5 3.3 10 0.99997 123
The HADES RICH Detector
Photon Detector :
• CH4 MWPC
• CsI cathode
• 28.600 pads
• 10 μs readout
CaF2 window
VUV mirror
The RICH Detector
Photon Detector :
• CH4 MWPC
• CsI cathode
• 28.600 pads
• 10 μs readout
Photon Detector
Single events in the RICH
Lepton identification: C+C @ 2 AGeV
tof [ns]tof [ns]
q*
mom
ent
um
q*m
oment
um
Log z!
= 18o - 50o = 50o - 85o
RICHon
RICHoff
T. Eberl, TUM –E12
Online Lepton ID
• Fast readout of all PID -detectors (10μs)
• Real time processing with
– Calibration
– Pattern recognition
– Position calculation
• Transfer to Matching Unit
• Decision and second leveltrigger distribution
Matching UnitSecond
Level
Trigger
TOFShowerRICH
Efficiency calibration(OEM)
beam
Photons produced by 600 AMeV 12C
beam particles passing two different
solid radiatorspad plane
tank
window
mirror
tank shell
target
radiator gas
detector gas
beam
field plane
photon detector
1
0.8
0.6
0.4
0.2
0.0120 140 160 180 200 220
SiO2
MgF2T
ransm
issio
n
[nm]
OEM Radiator
2cm
beam
beam line
beam pipe shadow
Nph ~ N0 * Z2
500 evt accumulated
MgF2
SiO2
Detector Response to VUV Photons
1 evt
C12 ions, E = 600 AMeV
Pulse Height Analysis
Class 1 Class 2 Class 3
Pad X Coordinate
Primary and feedback photons
Feedback
Primary
Pa
d Y
Co
ord
ina
te
1 Event
Puls
e H
eig
ht
1 primary
photon?
Pulse Height Distribution
• Pulse Height AnalysisQ Mean = 5 * 10 4 e-
SE ~ 90%
Anode Voltage = 2450 V
CH4 atmos. press.
Coupling to Neighbouring Pads
Along the wire
photon impact
resolution ~ 0.5 mm
Perpendicular to wire
Only Class 1 clusters are used!!
Charge Distribution of Single Photons
Simulation
Experiment
single photon response
well understood
Analysis of Photon Yield
Experimental Data Simulation Input ((HGeantHGeant))
– Optical parameters (all independently measured)
– Simulation of single photon response
– Electronic noise
N0=102100 Events
Beam pipe
shadow
N0 Calculation
20
0
20
2
1
2
1
)()(.
102
)(.
=
=
=
i
Sim
i
Exp
Sim
i
Sim
i
Sim
RconstN
N
constN
98/
130
88/
100
102102
78/
88
102
80/
99
102
96/
110
94/
106
92/
106
78 /
88
102102102102
Sector 6
MgF2 SiO2
Sector 3
MgF2 SiO2
Sector 2
MgF2 SiO2
Sector 1
MgF2 SiO2
NSim0
NExp0
e+/e- from different Sources!
Same-event like-sign (LS) CB
• Correlations under Mee = 150MeV/c2
• Low Statistic above Mee~ 450 MeV/c2
Event-Mixing (EM) CB
• Good statistics
• The correlation is not described
e+e+
e-e-
e+e+
e-e-
++=eeeeCB
N*N*2N
Mee < 150 MeV/c2 - Like-sign CB
Mee > 150 MeV/c2 - Event mixing CB
Mee [MeV/c2]1/N
0 d
N/d
M [
Me
V/c
2]-
1
Same Event
Mixed Event
Hybrid
Hybrid Method
Normalization of the EM-CB on top of the
LS-CB [150 MeV/c2 < Mee < 550 MeV/c2]
Combinatorial Background
Dilepton Spectroscopy
Comb. Backgr.
Suppression
Close pair
recognition !!!!
&
rejection
2 close rings
in RICH
2 close tracks
in MDC0 200 400 600 800 1000
10-1
1
10
102
103
104
dalitzη
dalitzΔ
pn bremstr.combin. back.
ρ
dalitzω
ω
dalitz0π
φ
C + C�E = 2*A GeV
]2 [MeV/c-e+eM
/ 10
col
l.2
coun
ts /
20 M
eV/c
9
HADES : Study of in-medium hadron properties via low mass e+e- pairs from , p, A + A collisions
full scale HGEANT simulation
Example:
Data vs. PLUTO cocktail: C+C@2AGeV
Cocktail A: 0 + +
= “long-lived” components only
Cocktail B: Cocktail A + +
Large excess yield!
Efficiency corrected spectra!
SSystematic errors:ystematic errors:
15% efficiency correction10% combinatorial background11% 0 normalization
21% TotalAgakishiev et al., Phys. Rev. Lett. 98, 052302 (2007)