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IP Measurements at PEP-II with BaBar. M.Weaver, C.O’Grady, J.Thompson (SLAC), W.Kozanecki (Saclay), B.Viaud (Montreal) Super-B III Workshop June 15, 2006. IP Characterization. BaBar’s tracking resolution and prime venue allow measurement of important parameters at the IP - PowerPoint PPT Presentation
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M. Weaver Super-B III Workshop, 15 June 2006
IP Measurements at PEP-IIIP Measurements at PEP-IIwith BaBarwith BaBar
M.Weaver, C.O’Grady, J.Thompson (SLAC), W.Kozanecki (Saclay), B.Viaud (Montreal)
Super-B III Workshop
June 15, 2006
M. Weaver Super-B III Workshop, 15 June 2006
IP CharacterizationIP Characterization
BaBar’s tracking resolution and prime venue allow measurement BaBar’s tracking resolution and prime venue allow measurement of important parameters at the IPof important parameters at the IP
Use
to measure production vertices and boost vector angles
(resolution)Production vertices (x,y,z ~ 30m)
Boost trajectories ( ~ 0.6 mrad)
e- beam
e+ beam
)(, eeee
M. Weaver Super-B III Workshop, 15 June 2006
VertexingVertexing
<X>, <Y> provide steering information<X>, <Y> provide steering information
)(, eeee
X (m)
Y (m)
100m
100m
M. Weaver Super-B III Workshop, 15 June 2006
<Z> measures relative RF phase<Z> measures relative RF phase
Z (mm)
2mm
M. Weaver Super-B III Workshop, 15 June 2006
d<X>/dz, d<Y>/dz is one measure of the collision axisd<X>/dz, d<Y>/dz is one measure of the collision axis
X’ (mrad)
Y’ (mrad)
1mrad
1mrad
M. Weaver Super-B III Workshop, 15 June 2006
X-size of luminous region determined by X-size of luminous region determined by emittances and IP-beta functionsemittances and IP-beta functions
(m)Lx
x-tune move towardshalf-integer
dynamic
M. Weaver Super-B III Workshop, 15 June 2006
Boost TrajectoryBoost Trajectory
TechniqueTechnique
ee
P
n
z
x
y
n
n
momenta poorly measured trajectories well measured
reconstruct decay plane normal n
M. Weaver Super-B III Workshop, 15 June 2006
tan = - x’Bcos – y’Bsin≈
x’(or y’)B = EH x’H – EL x’L EH - EL
Boost TrajectoryBoost Trajectory
M. Weaver Super-B III Workshop, 15 June 2006
<X’<X’BB>, <Y’>, <Y’BB> is another measure of the collision axis> is another measure of the collision axis
X’B (mrad)
Y’B (mrad)
1mrad
1mrad
M. Weaver Super-B III Workshop, 15 June 2006
Crossing AngleCrossing Angle
<X’<X’BB>-<X’>-<X’LL> => = '''22
22
2
1xLxHx
xHxL
xHxL
LEHELEHE
Run4 optimum
from x-ing angle
study<X’<X’BB>-<X’>-<X’LL> (mrad)> (mrad)<X’<X’BB>>,,<X’<X’LL>> (mrad) (mrad)
M. Weaver Super-B III Workshop, 15 June 2006
X’BX’B, , Y’B Y’B dominant contribution from electron beamdominant contribution from electron beam
(mrad)Hx'
x-tune move towardshalf-integer
dynamic
M. Weaver Super-B III Workshop, 15 June 2006
Studies on Luminosity TransientStudies on Luminosity Transient
Track time resolution (~2ns) allows Track time resolution (~2ns) allows event association to RF bucket event association to RF bucket
(476 MHz)(476 MHz)
Studied many IP parameters along Studied many IP parameters along bunch trainbunch train
z-centroid, size
x,y-centroids, x-size
x’,y’ means and spread
Events
z-centroid x-size
mini-train
mini-train
full-train
20%
63m
66m
mm
M. Weaver Super-B III Workshop, 15 June 2006
**yy Msmts I - Luminosity (Z) Msmts I - Luminosity (Z)
2
2221 exp
2
2)(
3z
z
zyx
NNz
L
)(, eeee
2,
2,
2LERzHERzz
LERyyHERyy
LERyyHERyy
LERyyHERyyy z **
**2**2
//1
2*1
effyZ-resolution (~ 30m) negligible compared to z,*y
Only acceptance/efficiency matterNeglecting complications from x-y coupling, dispersion,….
M. Weaver Super-B III Workshop, 15 June 2006
Luminosity (Z) FitsLuminosity (Z) Fits
Chisq: 108, for 100-5 d.o.f. Prob: 17%
Norm 1.02125e+00 1.47665e-03 Zc 3.68052e-02 2.66972e-03 CapSigzSqrd 2.45044e+00 1.03738e-02 BetaY 1.33328e+00 1.96984e-02 Waist -8.00839e-02 1.26765e-02
Chisq: 132, for 100-5 d.o.f. Prob: 0.7%
Norm 1.02514e+00 1.63293e-03 Zc 2.64888e-02 2.62672e-03 CapSigzSqrd 2.21443e+00 9.75603e-03 BetaY 1.18414e+00 1.71040e-02 Waist -4.35208e-02 1.11199e-02
Run 62101-62613 Run 62762-63049
M. Weaver Super-B III Workshop, 15 June 2006
**yy Msmts II - Luminous Y-Size (Z) Msmts II - Luminous Y-Size (Z)
2*
21)(2
y
z
yy
yyz
yLH
LH
L
ee
Assumes common y*
Ly (cm)Y-resolution (30m) large
compared to YL (~4m).
Courageous analysis using track miss-distance to estimate
per-event resolution.
Some systematics not resolved.
M. Weaver Super-B III Workshop, 15 June 2006
Luminous Y-Size (Z)Luminous Y-Size (Z)
Specific luminosity
Specific luminosity
*y
(cm
)L y,
z=0
(cm
) Nicely anti-correlated
withSpecific luminosity
M. Weaver Super-B III Workshop, 15 June 2006
**yy Msmts III - Boost Y-Angular Spread (Z) Msmts III - Boost Y-Angular Spread (Z)
2Y’B(z) =
(H+L)(f2H + f2L) + z2 H L
(1 + z2 / 2)H + (1 + z2 / 2)L
Depends upon vertical emittances and beta-stars
collisions withuncorrelatedtrajectories
collisions withvery correlated
trajectories
(all s are at IP)
y
z
collisions withvery correlated
trajectories
2*
2*
2
LEHE
y
yLE
y
yHE
L
L
H
H
**
**
L
L
H
H
L
L
H
H
y
y
y
y
y
y
y
y
M. Weaver Super-B III Workshop, 15 June 2006
Boost Y-Angular Spread (Z)Boost Y-Angular Spread (Z)
y*
y/y*
M. Weaver Super-B III Workshop, 15 June 2006
**yy Msmts Compared Msmts Compared
dL/dz Fit
σy(z) method
Boost method
βy*(eff) from phase
advance. Courtesy of Jerry Yocky.
M. Weaver Super-B III Workshop, 15 June 2006
**yy Msmts Compared Msmts Compared
BaBar results are significantly higher than PEP BaBar results are significantly higher than PEP measurements.measurements.
Possibilities:Possibilities:
•Analysis errors
•Optics different low current vs in-collision
•X-Y coupling
promising; under investigation
M. Weaver Super-B III Workshop, 15 June 2006
Boost Angle-Position CorrelationBoost Angle-Position Correlation
x’B = x(z-zH) fH – (z-zL) fL
H+(z-zH)2
L+(z-zL)2
Depends upon beta-stars and waist locations
Negative x-x’B
correlation here
(all s are at IP)
x (y)
z
Positive x-x’B
correlation here
M. Weaver Super-B III Workshop, 15 June 2006
Boost Angle-Position CorrelationBoost Angle-Position Correlation
Z<0
Z>0
Adds an additional measured constraint upon vertical emittances and beta-function
M. Weaver Super-B III Workshop, 15 June 2006
Vertical EmittancesVertical Emittances
y’(z) fit only
y’(z) + yy’(z) fit
Systematic shift not yet understood – coupling
also possible explanation
M. Weaver Super-B III Workshop, 15 June 2006
IP Coupling MeasurementsIP Coupling Measurements
X-Y Coupling may explain systematic effects in our X-Y Coupling may explain systematic effects in our measurements and (more importantly) degrade luminosity.measurements and (more importantly) degrade luminosity.
Can we measure coupling parameters?Can we measure coupling parameters?
Measurements to exploreMeasurements to explore X-Y Tilt of Luminous Region Ellipsoid
X’-Y’ Tilt of Boost Vector Ellipse
X-Y’ Boost Vector Position-Angle Correlation
Y-X’ Boost Vector Position-Angle Correlation
M. Weaver Super-B III Workshop, 15 June 2006
BaBar IP measurements reported onlineBaBar IP measurements reported online
Luminous RegionLuminous Region centroids { x, y, z}
sizes { x, z } every 10 minutes
tilts { dx/dz, dy/dz }
dL/dz fit { z, *y } every ~hour
Boost TrajectoryBoost Trajectory mean { x’, y’ } every 10 minutes
spread { x’HER, y’HER } every 30 minutes
}
M. Weaver Super-B III Workshop, 15 June 2006
IP Measurements at Super-BIP Measurements at Super-B
yyLL will be much smaller (20 nm) will be much smaller (20 nm)
xxLL will be smaller than PEP-II will be smaller than PEP-II yyLL
Z-resolution still ~< “effective” bunch lengths and Z-resolution still ~< “effective” bunch lengths and yy**
Boost angular spread similarBoost angular spread similar
Boost angle-position correlationBoost angle-position correlation larger intrinsic correlation (1/2)
smaller x,y coordinates x-may be possible, y-not may lose due to systematic effects (alignment)
All online measurements still possible (except All online measurements still possible (except xxLL))
Some offline analyses won’t work; replace with new ideasSome offline analyses won’t work; replace with new ideas
Statistics will come much faster!Statistics will come much faster!
M. Weaver Super-B III Workshop, 15 June 2006
SummarySummary
BaBar is trying to contribute to the understanding of the BaBar is trying to contribute to the understanding of the PEP-II colliderPEP-II collider
New ideas for measurements keep accumulatingNew ideas for measurements keep accumulating
Understanding of IP parameter analyses seems to be Understanding of IP parameter analyses seems to be converging.converging.
Hope that (this and) future experiment/accelerator Hope that (this and) future experiment/accelerator combinations can benefit from our effortscombinations can benefit from our efforts
M. Weaver Super-B III Workshop, 15 June 2006
Spare SlidesSpare Slides
M. Weaver Super-B III Workshop, 15 June 2006