Luminosity Studies in Run 1b

1
Luminosity Studies in Run 1b Run 1b Tevatron
Lattice Parameter Measurements with Separated
Beams at D-Zero
Michael A. Tartaglia, Fermilab
Summary Motivated by a 10 difference in
luminosity at the two collider experiments,
during Run 1b after correction of a rolled CDF
low beta quadrupole, the D-Zero and Tevatron
Operations groups collaborated on a series of
experiments. Electrostatic separators were used
to explore the interaction rate and vertex
Z-distributions as a function of beam separation.
The resulting data sets were analyzed to
determine fundamental parameters of the Tevatron
optics at the D-Zero Interaction Region The
horizontal (X) and vertical (Y) beta functions
(s2 vs z) were measured with good precision and X
was found to be not as expected. Fits for
individual beam parameters were also performed,
to understand whether absolute luminosity
calculations could be made at a precision (5)
level from first principles (ans its hard).
EXPERIMENTS WITH SEPARATED BEAMS IN RUN I AT
THE TEVATRON COLLIDER by M.A. Tartaglia (for the
Dzero Collaboration) FERMILAB-CONF-97-184-E, Jun
1997 Published in Vancouver 1997, Particle
Accelerator, vol. 1 147-149
Table of emittance and beta function parameters
calculated in two ways (in Y)
Data Sets Separated Beam scans were performed at
the end of four stores during Run 1b Data
recorded only from the Level zero detector
(at high rate to measure collision vertex
distribution in z) Scan 1 X , scans 2
3 X,Y at b35cm scan 4 X, Y, diagonal
at b25cm Straightforward, small corrections made
for a) multiple interactions, b)
luminosity decay with time, c) z-distribution
and detector acceptance change with separation
RESULTS 1) Unexpected crossing angles seen in
both planes (50,20mrad in X,Y) 2) Beta in
Horizontal Plane greater than expected (45cm
instead of 35cm) 3) Beta in Vertical Plane as
expected
Example of data sets from scan 4
Analysis the Linear Model for luminosity There
are a LOT of parameters! This technique can
provide information on many of them (see table)
Get individual parameters by fitting dL/dz vs Z
(vs dX and dY) (global fit not done, would give
better results) Get s2 vs z directly by fitting
RATIOS of dL/dz taken at different dX and dY
agreement between ratios taken with different
dX,Y ? confirms gaussian distribution and
separations!
Calculated and Measured Luminosity vs separation
(data dont agree in X with the nominal beta
function)
Although Luminosity profile agrees with model,
absolute luminosity differs from calculation by
10-20