instrumentation of the very forward region of a linear collider
TRANSCRIPT
August 2005 Snowmass Workshop
Instrumentation of the Very Forward Region of a Linear Collider Detector
Wolfgang Lohmann, DESY
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 0.5 1 1.5 2 2.5 3 3.5 4
QD0
Inst. Mask
HCAL
ECAL YOK
E
WW
46mrad
113mrad
Support Tube
Pair-LuMon
BeamPipe
LowZMask Exit
radius 2cm @ 3.5m
WW
5 Tesla
SiD Forward Masking, Calorimetry & Tracking,20 mrad crossing angle
Simulation studieson several
designs
Used by H. Yamamoto
IP
VTX
FTD
300 cm
LumiCal
BeamCal
L* = 4m
Design for 0-2 mradcrossing angle (FCAL design)
Functions of the very Forward Detectors
•Fast Beam Diagnostics
•Detection of electrons and photons at small polar angles-important for searches(see talk by Philip&Vladimir
•Measurement of the Luminosity with precision O(<10-3) usingBhabha scattering(see talk by Halina)
LumiCal: 26 < θ < 82 mradBeamCal: 4 < θ < 28 mradPhotoCal: 100 < θ < 400 µrad
IP
VTX
FTD
300 cm
LumiCal
BeamCal
L* = 4m
PhotoCal downstram
•Shielding of the inner Detectors
•Measurement of the Luminosity (LumiCal)
Gauge Process:
Goal: <10-3 Precision
• Technology: Si-W Sandwich Calorimeter
• MC Simulations
e+e- e+e- (γ )
Optimisation of Shape and Segmentation,Key Requirements on the
Design
Physics Case: Giga-Z ,Two Fermion Cross Sections at High Energy, e+e- W+W-
Inner Radius of Cal.: < 1-4 µm
Distance between Cals.: < 60 µm
Radial beam position: < 0.7 mm
Requirements on Alignment
and mechanical Precision(rough Estimate)
LumiCal
LumiCalIP< 4 µm
< 0.7 mm
Requirements on the Mechanical Design
Decouple sensor framefrom absorber frame
Sensor carriers
Absorber carriers
Concept for the Mechanical Frame
)]}ln()([,0max{T
ibeami E
EEconstW +=∑
∑>=<i
ii
WWX
X
Constant value))(_( radmean genrec θθ −
))(( radθσ
value of the constant
0.11e-3 rad0.13e-3 rad
30 layers 15 rings
20rings
10rings
4 layers
15 layers
11 layers
10rings
Performance Simulations for e+e- e+e-(γ )
Event selection: acceptance, energy balance, azimuthal and angular symmetry.
Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread
•More in the talks by Halina Abramowicz
X- angle background
Christian Grah, DESY-Zuethen
Beamstrahlung pair background
using serpentine field
0.E+00
1.E+09
2.E+09
3.E+09
4.E+09
5.E+09
6.E+09
8 9 10 11 12 13 14 15 16
R min (cm)
Nmbe
r of B
habh
a ev
ets
per y
ear
0
500
1000
1500
2000
2500
3000
3500
Back
grou
nd (G
eV)
Events per yearBackground (GeV)
250 GeV
Number of Bhabha events as a function of the innerRadius of LumiCal
Background from beamstrahlung
•Fast Beam Diagnostics (BeamCaland PhotoCal)
e-e+
• 15000 e+e- per BX 10 – 20 TeV(10 MGy per year)
• e+e- Pairs from Beamstrahlung are deflected into the BeamCal
GeV
• direct Photons for θ < 200 µrad
Zero crossing angle
20 mradCrossing angle
total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries
Observables
Quantity Nominal Value Precision
σx 553 nm 1.2 nmσy 5.0 nm 0.1 nm
σz 300 µm 4.3 µm
∆y 0 0.4 nm
Beam Parameter Determination with BeamCal
Head-on or 2 mrad
√s = 500 GeV
Quantity Nominal Value Precision
σx 553 nm 4.8nmσy 5.0 nm 0.1 nm
σz 300 µm 11.5 µm
∆y 0 2.0nm
Beam Parameter Determination with BeamCal
PRELIMINARY!
20 mrad crossing angle
total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries
Also simultaneous determination of several beam parameter is feasible, but: Correlations!Analysis in preparation
Observables
nominal setting(550 nm x 5 nm)
>100mIP
L/R, U/D F/B asymmetriesof energy in the angulartails
Quantity Nominal Value Precision
σx 553 nm 4.2 nmσz 300 µm 7.5 µm
∆y 0 0.2 nm
Heavy gas ionisationCalorimeter
and with PhotoCal
Photons from Beamstrahlung
Heavy crystalsW-Diamond sandwich
sensorSpace forelectronics
Technologies for the BeamCal: •Radiation Hard•Fast•Compact
•Detection of High Energy Electrons and Photons
√s = 500 GeVSingle Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’)(talk by V. Drugakov and P. Bambade)
Detection efficiency as a function of the pad-size (Talk by A. Elagin)
Message:Electrons can be
detected!
Red – high BGblue – low BG
bunch #0 100 200 300 400 500
Em
ean
, GeV
0100200300400500600700800900
1000
mean energy in particular cell (high BG near BP)
real beams
ideal beams
mean energy in particular cell (high BG near BP)
bunch #0 100 200 300 400 500
Erm
s, G
eV
050
100150200250300350400
energy RMS in particular cell (high BG near BP)
real beamsideal beams
energy RMS in particular cell (high BG near BP)
Includes seismicmotions, Delay of BeamFeedback System, Lumi
Optimisation etc.(G. White)
Efficiency to identify energetic electrons and photons(E > 200 GeV)
Fake rate
√s = 500 GeVRealistic beam simulation
•Detection of High Energy Electrons and Photons
Sensor prototyping, Crystals
Light Yield from direct coupling
Similar results for lead glassCrystals (Cerenkov light !)
0 200 400
Eve
nts
0
10
20
30
40
50
Number of Photoelectrons0 200 400
0
10
20
30
40
and using a fibre
~ 15 %
Compared with GEANT4Simulation, good agreement
Sensor prototyping,Diamonds
ADC
Diamond (+ PA) Scint.+PMT&
signal gate
May,August/2004 test beams CERN PS Hadron beam – 3,5 GeV2 operation modes:
Slow extraction ~105-106 / sfast extraction ~105-107 / ~10ns (Wide range intensities)
Diamond samples (CVD):- Freiburg- GPI (Moscow) - Element6
Pm1&2
Pads
Linearity Studies with High Intensities
(PS fast beam extraction)105 particles/10 ns
Response to mip
Diamond Sensor Performance
Relative Intensity [a.u.]0 50 100
Dia
mo
nd
res
po
nse
[A
DC
ch
]
0
10000
20000
Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell.
Univ. Cracow,JINR, Dubna,
NCPHEP, Minsk,FZU, Prague,
IHEP, Protvino,TAU, Tel Aviv,DESY, Zeuthen
Workshop on the Instrumentation of the Very Forward Region of the ILC DetectorTel Aviv, Sept. 15.-20. 2005.http//alzt.tau.ac.il/~fcal/
Summary• Many (and promising) results in simulations/design studies • Concept for a Luminometer for small crossing angle isadvanced, 20 mrad needs a different design
• Mechanics design work ongoing
• Studies with sensors started- needs more effort
• High energy electron detection down to small polarangles is feasible with compact and fine segmentedcalorimeters; easier for small crossing angle
• calorimeters in the very forward region deliververy valuable information about beam parameters
• Prototype tests mandatory
Remarks
• The instrumentation of the forward region is relativelyindependent of the detector concept,
Backup Slides
Vertexdetector
FTD
297
mm55.5 mrad
83.1 mrad
27.5 mrad
3000 mm
LAT
Tungsten shield
Quadrupole
Graphite
IP
LCALInner Mask
Shower in LAT (TDR design)
Shower LEAKAGE in old (TDR) and new LumiCal design
Shower in LumiCal(new design)
Diamond performance as function of the absorbed dose
Linearity of a heavy gas calorimeter (IHEP testbeam)
Beam Energy [GeV]0 10 20 30 40 50
]- e6N
um
ber
of
Ion
izat
ion
Ele
ctro
ns
[10
0
0.5
1
1.5
atm)⋅E/P = 2000 V/(cm
Dose, Gy0 5 10 15
Me
an
, A
DC
ch
0
50
100
FAP21FAP22FAP23
Radius [cm]1 2 3 4 5 6
Eff
icie
ncy
[%
]
0
20
40
60
80
100
-100 GeV e
Sampling
Crystal
Comparison SamplingHeavy Crystal
Radius [cm]1 2 3 4 5 6
Eff
icie
ncy
[%
]
0
20
40
60
80
100
= 500 GeVs, -200 GeV e
= 1 TeVs, -400 GeV e
Comparison 500 GeV - 1TeVComparison Sampling
Heavy Crystal
Z
X
in-e
out-e
in+e
out+e
B = 4TB = 4T
Depositions on the calorimter frontface
Headon 20mradBeamPar MPI
resolution
26.789
11.201
0.893
1.648
13.018
18.780
5.918
0.536
327.312
0.109
0.043
MPI resolution
σx σx’ σy σy’ σz σz’ offx
offy
wy
N
1
1
0.887
0.168
0.017
0.039
0.149
0.720
1
-0.182
0.144
-0.016
0.056
-0.520
1
-0.748
-0.161
0.290
1
0.018 0.030
0.395
-0.032
0.004
0.414
-0.209
1
0.275
-0.496
0.581
0.481
1
-0.271
-0.369
0.101
-0.527
-0.488
0.237
0.434
0.316
0.631
1
0.700
0.852
0.080
0.127
-0.803
0.901
0.619
-0.048
1
0.441
-0.143
-0.125
-0.927
0.713
0.016
-0.119
1
-0.101
-0.036
-0.577
0.623
0.869
0.066
σy (diff) 1.839
σz (ave) 17.781
σz (diff) 14.747
Beam offset x 6.652
N per Bunch (ave)
0.080
Beam offset y 6.767
Vertical waist shift
σx (ave) 20.471
σx (diff) 16.615
σy (ave) 2.196
N per Bunch (diff)
159.172
0.054