ip characterization measuring the boost vector
DESCRIPTION
IP Characterization Measuring the Boost Vector. Matt Weaver PEP Meeting May 15, 2006. Motivation. Measure parameters contributing to luminosity to quantitatively verify that we’re generating all we can. Machine behavior in collision may have surprises that we can benefit from understanding. - PowerPoint PPT PresentationTRANSCRIPT
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IP Characterization Measuring the Boost Vector
Matt Weaver
PEP Meeting
May 15, 2006
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Motivation
• Measure parameters contributing to luminosity to quantitatively verify that we’re generating all we can.
• Machine behavior in collision may have surprises that we can benefit from understanding.
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Boost Trajectory Measurement
e+e-
LH
LLHHxB EE
xExEp
px
''
'Measure collision point {x,y,z}
and trajectories of pair {x’,y’}
z mean, spread, distribution x,y mean, spread, correlation with zx’,y’ mean, spread, correlation with z
correlation with x,y
B
z resolution ~ 60 mx,y resolution ~ 30 mx’,y’ resolution ~ 0.6 mrad
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Boost Vector Properties
Near the waist (z << *), x and x’ are uncorrelatedx
z *2
*22
'L
LL
H
HHX ff
B
LLHHB xfxfx '''
LH
LHLH EE
Ef
)()( this 9 times
greater than
Expect that X measurements behave like this (z << *X)Boost X’ spread largely reflects HER X’ angular spread
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Lu
min
ou
s X
-siz
e (
m)
HE
R X
’-sp
read
(m
rad
)
Move to half-integer x-tune
dynamic
dynamic
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Far from the waist (z >> *), x and x’ are highly correlated
x
z
**
**2'
L
L
H
H
L
L
H
H
X B
zx
x B '
Boost Vector Properties
Bunch lengths are small compared to *X and comparable to *Y,
so we never see these relations fully.
However, the transition must develop on a z-scale of *, so the z-dependence of these msmts must be a measure of *
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Boost Vector Z-Dependence
LH
LHBB
xx
'
' (luminosity-weighted)
22*22*'
z
zf
z
zfxx
L
L
H
HB
LH
LHBx
xB
2
2'
'
22
222
2
2'
2
2'
2
22
2
222'
LH
LH
L
L
H
H
LH
Bxx
xx
x
xxL
x
xxH
x
LL
x
HHx
ffff
*2*2
H
HHHH
x
xxxx z
*2'
H
HH
x
xxx z
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Monte Carlo Validation 14mm * 14mm *
10mm * 10mm *
6mm * 6mm *
y’dy’/dy
z (cm)z (cm)
mra
d-c
m
mra
d
~ 1 week data
5 fit parametersY*
y-waist z offsetH
L
2YY’ detector error
Fit 2 is a simple sumof the two 2s
No y’ dy’/dy} covariance terms included
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Example measurement of angular spread
Non-zero slope is reminiscentof lumi X-size measurements.
Implies X-waist offset.
“Width” is measure of *.“Height” is measure of *.
Value at z-centroid is well-determined.Limit for z>>* not reached.
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Example measurement of collision position-boost angle correlation
“Z >0”“Z <0”
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Run5 Fit Results*
(m
m)
z (
mm
)
H
(nm
)
L
(nm
)
waistlumi centroid
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Y
(m
)S
pec
ific
Lu
min
osi
ty
Y derived from combined-fit results shows good anti-correlation with specific luminosity
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X s
izes
(m
) X
/
XL
“X”
XL
1
2
2.5
Ratio
of b
eam x-s
izes
X derived from Y measurements
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Fit Results*
(m
m)
wai
st z
(m
m)
H
(nm
)
L
(nm
)
waistlumi centroid
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Plans
Separately determine HER, LER *Y and y-waist locations
Estimate impact of coupling, dispersion {Y, Y’}
Make a measure of coupling y’B(x), x’B(y)
What to do with x? 3 measurements { X,X’,x’B(x)}, at least 4 parms
Make quantitative comparisons to beam-beam simulationversus bunch current, tune?
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Extra Slides
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Boost Trajectory Measurement
e+e-
n
momenta poorly measured trajectories well measured
reconstruct decay plane normal n
z
x
y
n
n
tan = - x’Bcos – y’Bsin≈
x’(or y’)B = EH x’H – EL x’L EH - EL
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Y-Y’ Correlation in Run5 Data
y (cm)
y’ (
mra
d)
y (cm)
Y distribution
y’ vs y invarious z-bins
y’ vs y invarious z-bins
dy’
/dy
z (cm)
dy’/dyversus z
Shift in mean
Y-mean dependsupon
More work to do here
Less S-shape
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d
x’H
/ d
z (m
rad
/cm
)Slope of x’ angular spread
Need to know emittances and beta*s to convert into a waist shift
Move to half-integer x-tune
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X-w
aist
off
set
(cm
)From x-x’ correlation measurement assuming common waist
Move to half-integer x-tune
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*
(mm
)
wai
st z
(m
m)
H
(nm
)
L
(nm
)
generated value
Monte Carlo Fit Results
combined fity’(z) fit only
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Toy Monte Carlo Tests *= L*=10mmzH=zL=0
y’dy’/dy
z (cm)z (cm)
mra
d-c
m
mra
d
≤ 1 week data
7 fit parameters*H, *L
y-waist z offsets (H,L)H, L
2YY’ detector error
Correlated detector errorsare not modeled
*= L*=10mmzH=zL=0
*= L*=10mmzH=+4mmzL=-4mm
*= 8.23mmL*=13.72mmzH=zL=0
*= L*=10mmzH=+4mmzL=-4mm
*= 8.23mmL*=13.72mmzH=zL=0
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*H
(mm
)
*L
(mm
)
z H
(mm
)
z L
(mm
)
generated value
Toy Fit Results
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Fit Results*
(m
m)
wai
st z
(m
m)
H
(nm
)
L
(nm
)
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Y
(m
)S
pec
ific
Lu
min
osi
ty
Y derived from combined-fit results shows good anti-correlation with specific luminosity
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Y
(m
)