Physics Impact of Detector
Performance
Tim Barklow
SLAC
March 18, 2005
1
Outline
• General Considerations
–
–
–
–
Vertex Detector
Tracker
Calorimeter
Far forward detector
• Examples of parametric physics studies
– Calorimeter DEjet
– Tracker Dpt
• Summary
2
Vertex Detector
• Classic application of b,c
tagging to Higgs
branching ratios.
• But there’s more:
– vertex charge
• top, W helicity
• qq asymmetries
 t tagging
• stau analyses
• Higgs tau BR
• b jets with several n’s
bb
t t 
gg
cc
W W
*Talk by Chris Damerell 21Mar2005

M
(GeV)
3H
Vertex Detector – tau tagging example
e  e   nn tt is an important strong symmetry
breaking signal (WW  tt ).
The large e  e   e  e tt background can be
mostly supressed by vetoing the forward e 
and requiring unbalanced p t . But there remains
a seemingly irreducible background from
e  e   e  e tt  e  e bbW W  where one
of the b quarks undergoes the decay
b  ct n t  c  n tn t , ce n en tn t , etc.  b  t decays have at least 2 n 's
Tau tagging could reduce this background
(and help b jet energy flow analysis in general).
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Tracker
 pt
2
t
p
• Momentum resolution
set by recoil mass
analysis of ZH  l l  X
• K S0 ,  0 reconstruction
and long-lived new
particles (GMSB SUSY)
• Multiple scattering effects
• Forward tracking
• Measurement of Ecm,
differential luminosity
and polarization using
physics events
 pt
2
t
p
 2  105
 8 105
Recoil Mass (GeV)
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Calorimeter
• Separate hadronically
decaying W’s from Z’s in
reactions where kinematic
fits won’t work:
e e  nn W W , nn ZZ
 


sE/E =
0.6/E
e  e   1 1  10 10W W 
e  e    20  20  10 10 ZZ
• Help solve combinatoric
problem in reactions with
4 or more jets
e e  ZH  qqWW *  qqqqln
 
e e  ZHH  qqbbbb
sE/E = 0.3/E
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Far Forward Detector
• Electron veto down to 3.2
mrad in presence of very
large e  e  pair background
• Useful in general to
suppress   ff
backround. Takes on
added importance given
that the SUSY parameter
space consistent with Dark
Matter density includes
region with nearly
degenerate 10 , t
• Crossing angle
implications.
t signal
after 3.2 mrad e veto
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Far Forward Detector
 cross  20 mrad
M/Mstau (%)
 cross  0
Rel. stau mass error increases from 0.14% to 0.22% with 20 mrad cross angle
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Signal significance at
s = 500 GeV
for e e  ZHH  qqbbbb
C. Castanier et al. hep-ex/0101028
Error on BR( H  WW *) from
measurement of
e  e   ZH  qqWW *  qqqqln
at
s  360 GeV, L=500 fb 1
J.-C. Brient, LC-PHSM-2004-001
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e e  ZH  qqbb
Reconstructed Mbb
 E jet
E jet
4C Fitted Mbb
 0.3
0.5
Mbb (GeV)
0.4
 E jet
E jet
0.6
Mbb (GeV)
0.4
 0.3
0.5
Mbb (GeV)
0.6
Mbb (GeV)
10
 
e e  ZH
 qqbb
 E jet
E jet
 0.3
DM h  42 MeV
 E jet
E jet
 0.4
DM h  46 MeV
s  350 GeV
L  500 fb 1
Mbb (GeV)
Mbb (GeV)
 E jet
E jet
 0.5
DM h  48 MeV
Mbb (GeV)
 E jet
E jet
 0.6
DM h  50 MeV
Mbb (GeV)
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e e  ZH
 qqbb
s  350 GeV
L  500 fb 1
DM h (MeV)
 E jet
E jet
1
2
(GeV )
12
Simdet Fast MC with this parameterization of pt
resolution in place of Simdet’s emulation of LDC:
a  2.1105
 pt
pt2
b  1.0 103
p=3 GeV
 pt
pt2
 a
b
pt sin 
SiD Detector Resolution
p=20 GeV
p=100 GeV
p=20 GeV, SIMDET LDC
 log10 (1  cos )
 log10 (1  cos )
13
e e  ZH
  X
a  2.0 105
a  1.0 105
b  1.0 103
b  1.0 103
DM h  103 MeV
DM h  85 MeV
s  350 GeV
L  500 fb 1
 pt
b
 a
2
pt
pt sin 
Recoil Mass (GeV)
Recoil Mass (GeV)
a  4.0 105
a  8.0 105
b  1.0 103
b  1.0 103
DM h  153 MeV
DM h  273 MeV
Recoil Mass (GeV)
Recoil Mass (GeV)14
e e  ZH
  X


a  2.0 105
a  2.0 105
b  1.0 103
b  0.5 103
DM h  103 MeV
DM h  96 MeV
s  350 GeV
L  500 fb 1
 pt
b
 a
2
pt
pt sin 
Recoil Mass (GeV)
Recoil Mass (GeV)
a  2.0 105
a  2.0 105
b  2.0 103
b  4.0 103
DM h  124 MeV
DM h  188 MeV
Recoil Mass (GeV)
Recoil Mass (GeV) 15
e e  ZH
  X
s  350 GeV
L  500 fb 1
DM h vs a
DM h vs b
DM h (MeV)
 pt
pt2
 a
b
pt sin 
a 105 or
b 103
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e  e    R  R
 pt
2
t
p
 a
a  2  105
a  4  105
Muon Energy (GeV)
DM   34 MeV
M  R  224 GeV
b
pt sin 
Fit for M 
s  500 GeV L  500 fb 1
only
a  1105
b  1 103
b  0.5 103
a  8 105
b  2 103
b  4 103
Muon Energy (GeV)
Muon Energy (GeV)
Muon Energy (GeV)
No dependence on a or b in the range
1.0 105  a  8.0 105 , 0.5 103  b  4.0 10 3 17
Branching Ratio of H  CC
e e  ZH
 l l  X
* Talk by Haijun Yang
in TRK session 20Mar2005
 DBr/Br ~ 39% (120GeV), 64% (140GeV) for Zl+l-, 1000 fb-1
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Beam Energy Profiles
Before Collision
s Ecm  0.1%
Ebeam (GeV)
E beam (incoming)  250 GeV
After Collision
bias
50 ppm < E CM
< 250 ppm
 B  4.3%
Lumi Weighted
 B  1.6%
Ebeam (GeV)
Ebeam (GeV)
Center of Mass Energy Error Requirements
• Top mass:
• Higgs mass:
• Giga-Z program:
200 ppm (35 Mev)
200 ppm (60 MeV for 120 GeV Higgs)
50 ppm
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Reconstructed E cm using Z events and
measured angles. Z   +  
s  350 GeV
L  100 fb 1
DEcm = 47
MeV
* Talk by Klaus Moenig
in MDI session 20Mar2005
Ecm (GeV)
20
The momentum resolution is set by Higgs recoil mass
measurement in e  e   ZH      H
In the reaction e  e   Z       we know the mass
of the photon. Why not invert the problem and use
the excellent momentum resolution to solve
for
s instead of the mass of the system opposite     ?
21
Reconstructed E cm & M Z using Z events and
measured momenta & angles. Z   +  
DE cm =  2 GeV
DE cm =  2 GeV
Ecm (GeV)
M (GeV)
22
Reconstructed E cm & M Z using Z events and
measured momenta & angles. Z   +  
Trk mom scale factor = 0.996
Trk mom scale factor = 1.004
Ecm (GeV)
M (GeV)
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Lumi  100 fb1
E cm  350 GeV
E Z = Measured E cm assuming Z boson recoil against single photon
E  = Measured E cm using full energy e e     
measured var
a
b
E Z ang only
DE cm (GeV) DE cm (GeV) DE cm (GeV)
DE cm
(ppm)
E cm
stat
sys(E scale)
total
total
.0473
0
.0473
135
E Z |p| & ang
2 105
1103
.0085
.0206
.0223
64
E Z |p| & ang
2 105
.5 10 3
.0054
.0124
.0135
39
E Z |p| & ang 34 105
4 103
.0375
.0313
.0488
139
2 105
1103
.0056
.0124
.0136
39
E  |p| & ang
24
Ecm Resolution
in MeV vs a or b
DE vs a
angles only
DEZ vs b
e e  
 


DEZ vs a
DE vs b
DE SIMDET LDC
DEZ SIMDET LDC
 pt
pt2
 a
b
pt sin 
a 105 or
b 103
25
Ecm Resolution
in MeV vs a or b
angles only
e e  
 


DEZ vs b
DE vs b
DE vs a
DEZ vs a
DE SIMDET LDC
DEZ SIMDET LDC
 pt
pt2
 a
b
pt sin 
a 105 or
b 103
26
Simdet Fast MC with this parameterization of pt
resolution in place of Simdet’s emulation of LDC:
a  2.1105
 pt
pt2
b  1.0 103
p=3 GeV
 pt
pt2
 a
b
pt sin 
SiD Detector Resolution
p=20 GeV
p=100 GeV
p=20 GeV, SIMDET LDC
 log10 (1  cos )
 log10 (1  cos )
27
Summary
• Current detector designs appear well
matched to envisioned physics program
• Choices will have to be made as realitities
of detector engineering and cost are
confronted – physics benchmark studies
will play a crucial role. The examples of
parametric studies shown here are just the
beginning.
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