Why study Diffractive W Boson?

1
Why study Diffractive W Boson?
2
Data Samples
Central and forward electron W boson sample
Start with Run1b W en candidate sample
Z boson sample Start with Run1b Z ee
candidate sample
hep-ex/0308032Accepted by Phys. Lett B
3
Multiplicity in W Boson Events
Plot multiplicity in 3lt?lt5.2
Peak at (0,0) indicates diffractive W boson
signal (91 events)
4
W Boson Event Characteristics
Standard W Events Diffractive W Candidates
5
Observation of Diffractive W/Z
Diffractive W and Z Boson Signals

• Observed clear Diffractively produced W and Z
  boson signals
• Background from fake W/Z
• gives negligible change in gap
• fractions

nL0
ncal
nL0
ncal
Central electron W
Forward electron W
DØ Preliminary
Sample Diffractive
Probability Background
All Fluctuates
to Data Central W (1.08 0.19 - 0.17)
7.7s Forward W (0.64 0.18 - 0.16)
5.3s All W (0.89 0.19 0.17)
7.5s All Z (1.44 0.61 - 0.52)
4.4s
nL0
ncal
All Z
6
DØ/CDF Comparison
CDF PRL 78 2698 (1997) measured RW (1.15
0.55) for ?lt1.1 where RW Ratio of
diffractive/non-diffractive W (a significance of
3.8?) This number is corrected for gap
acceptance using MC giving 0.81 correction, so
uncorrected value is (0.93 0.44) , consistent
with our uncorrected data value We measured
(1.08 0.19 0.17) for ?lt1.1 Uncorrected
measurements agree, but corrections derived from
MC do not Our measured() gap acceptance is (21
4), so our corrected value is 5.1 ! ()
derived from POMPYT Monte Carlo Comparison of
other gap acceptances for central objects from
CDF and DØ using 2-D methods adopted by both
collaborationsDØ central jets 18 (q)
40(g) CDF central B 22(q) 37 overall CDF J/?
29 It will be interesting to see Run II
diffractive W boson results!
7
Run I Gaps

• Pioneered central gaps between jets, 3 papers,
  3 Ph. Ds
• Observed and measured forward gaps in jet
  events at ?s 630 and 1800 GeV. Rates much
  smaller than expected from naïve Ingelman-Schlein
  model.
• Require a different normalization and significant
  soft component to describe data. Large fraction
  of proton momentum frequently involved in
  collision.
• Observed jet events with forward/backward gaps
  at ?s 630 and 1800 GeV
• Observed W and Z boson events with gaps

8
Run II Improvements

• Larger luminosity allows search for rare
  processes
• Integrated FPD allows accumulation of large hard
  
• diffractive data samples
• Measure ?, t over large kinematic range
• Higher ET jets allow smaller systematic errors
• Comparing measurements of HSD with track tag vs.
  
• gap tag yields new insight into process

9
DØ Run II Diffractive Topics
Soft Diffraction and Elastic Scattering
Inclusive Single Diffraction Elastic
scattering (t dependence) Total Cross
Section Centauro Search
Inclusive double pomeron
Search for glueballs/exotics Hard
Diffraction Diffractive jet
Diffractive b,c ,t , Higgs
Diffractive W/Z
Diffractive photon Other
hard diffractive topics Double
Pomeron jets Other Hard Double Pomeron
topics
Rapidity Gaps Central gapsjets Double
pomeron with gaps Gap tags vs. proton tags
Topics in RED were studied with gaps only in Run
I
lt100 W boson events in Run I, gt1000 tagged events
expected in Run II
10
Run II Rapidity Gap System
VC 5.2 lt h lt 5.9
LM 2.5 lt h lt 4.4

• Use signals from Luminosity Monitor and Veto
  Counters (designed at UTA)
• to trigger on rapidity gaps with calorimeter
  towers for gap signal
• Work in progress (Mike Strang UTA, Tamsin Edwards
  U. Manchester)
• no time to present in this talk

11
Forward Proton Detector Layout
p
P1U
P2O
Q4
D
Q2
Q3
S
Q2
S
Q4
Q3
A1
A2
D2
D1
P1D
P2I
Veto
59
57
23
33
33
23
0
Z(m)

• 9 momentum spectrometers comprised of 18 Roman
  Pots
• Scintillating fiber detectors can be brought
  close (6 mm) to the beam to track scattered
  protons and anti-protons
• Reconstructed track is used to calculate momentum
  fraction and scattering angle
• Much better resolution than available with gaps
  alone
• Cover a t region (0 lt t lt 3.0 GeV2) never before
  explored at Tevatron energies
• Allows combination of tracks with high-pT
  scattering in the central detector

12
Castle Design
Worm gear assembly
50 l/s ion pump
Thin vaccum window

• Constructed from
• 316L Stainless Steel
• Parts are degreased
• and vacuum degassed
• Vacuum bettter than
• 10-10 Torr
• 150 micron vacuum
• window
• Bakeout castle, THEN
• insert fiber detectors

Detector
Beam
Step motor
13
Castle Status

• All 6 castles with 18 Roman pots comprising the
  FPD were constructed in Brazil, installed in the
  Tevatron in fall of 2000, and have been
  functioning as designed.

A2 Quadrupole castle installed in the beam line.
14
Acceptance
Dipole acceptance better at low t, large
x Cross section dominated by low t
Combination of QD gives double tagged events,
elastics, better alignment, complementary
acceptance
15
FPD Detector Design

• 6 planes per detector in 3 frames and a trigger
  scintillator
• U and V at 45 degrees to X, 90 degrees to each
  other
• U and V planes have 20 fibers, X planes have 16
  fibers
• Planes in a frame offset by 2/3 fiber
• Each channel filled with four fibers
• 2 detectors in a spectrometer

17.39 mm
V
V
Trigger
X
X
U
U
17.39 mm
1 mm
0.8 mm
3.2 mm
16
Detector Construction
At the University of Texas, Arlington (UTA),
scintillating and optical fibers were spliced and
inserted into the detector frames.
The cartridge bottom containing the detector is
installed in the Roman pot and then the cartridge
top with PMTs is attached.
17
Detector Status

• 20 detectors built over a 2 year period at UTA.
• In 2001-2002, 10 of the 18 Roman pots were
  instrumented with detectors.
• Funds to add detectors to the remainder of the
  pots have recently been obtained
• from NSF (should acknowledge funding from UTA
  REP, Texas ARP, DOE,
• and Fermilab as well).
• During the shutdown
• (Sep-Nov. 2003), the final eight
• detectors and associated readout
• electronics have been installed.

M.Strang
P2 Quadrupole castle with up and down detectors
installed
18
Pot Motion Software
Pot motion is controlled by an FPD shifter in the
DØ Control Room via a Python program that uses
the DØ online system to send commands to the step
motors in the tunnel.
The software is reliable and has been tested
extensively. It has many safeguards to protect
against accidental insertion of the pots into
the beam.
19
FPD Trigger and Readout
20
Stand-alone DAQ

• Due to delays in DØ trigger electronics, we
• have maintained our stand-alone DAQ first
• used in the fall 2000 engineering run.
• We build the trigger with NIM logic using
• signals given by our trigger PMTs, veto
• counters, DØ clock, and the luminosity monitor.
• If the event satisfies the trigger requirements,
  the CAMAC module will process the signal given
  by the MAPMTs.
• With this configuration we can read the fiber
  information of only two detectors, although all
  the trigger scintillators are available for
  triggering.

21
Elastic Trigger
In-time hits in AU-PD detectors, no early time
hits, or LM or veto counter hits

• Approximately 3 million elastic triggers
  taken with stand-alone DAQ
• About 1 (30,000) pass multiplicity cuts
• Multiplicity cuts used for ease of reconstruction
  and to remove halo spray background

22
Segments to Hits

• Combination of fibers in a frame determine a
  segment
• Need two out of three possible segments to get a
  hit
• U/V, U/X, V/X
• Can reconstruct an x and y
• Can also get an x directly from the x segment
• Require a hit in both detectors of spectrometer

23
Initial Reconstruction
P1D
beam
Y
Reconstructed ?
X
DØ Preliminary
P2D
beam
Y
??p/p should peak at 0 for elastic events!!
Dead Fibers due to cables that have since been
fixed
24
Spectrometer Alignment
P1D x vs. P1D x (mm)
P1D y vs. P2D y (mm)
DØ Preliminary

• Good correlation in hits between detectors of the
  same spectrometer but shifted from kinematic
  expectations
• 3mm in x and 1 mm in y

25
Elastic Data Distributions
After alignment and multiplicity cuts (to remove
background from halo spray)
??p/p
dN/dt
Acceptance loss
Residual halo contamination
?
The fit shows the bins that will be considered
for corrected dN/dt
Events are peaked at zero, as expected, with a
resolution of ?? 0.019
26
Final dN/dt Results
After unsmearing and acceptance corrections,the
data points were normalized to the points
obtained by the E710 experiment
The results are in excellent agreement with the
model of M. Bloch showed in the figure
Warning error bars need the contribution of the
unsmearing errors ? in progress
Dr. Jorge Molina, (LAFEX, Brazil) defended his
thesis on these results 10/31/03 (first FPD
thesis!)
27
Dipole TDC Resolution
p
D2 TDC
p halo from previous bunch

• Can see bunch structure of both proton and
  antiproton beam
• Can reject proton halo at dipoles using TDC
  timing
• CDF does not have this capability

D1 TDC
28
Standalone Readout vs. AFE Readout

• Standalone Readout
• Uses a trigger based on particles passing through
  trigger scintillators at detector locations
• No TDC cut
• this cut removes lower correlation (halo) in y
  plot
• Diffracted pbars fall in upper correlation of y
  plot

• AFE readout
• Similar correlations
• Uses trigger
• one jet with 25GeV and North luminosity counters
  not firing
• This trigger suppresses the halo band

29
Dipole Diffraction Results
Geometrical Acceptance 14s (Monte Carlo)
Data
?
Flat-t distribution
?
0.08
0.06
0.04
0.02
0.
t (GeV2 )
t (GeV2 )
30
Run II Diffractive Z ? µµ
Event Display
MZ all
gap
MZ gap
muons
Tagged Z event in FPD
31
Summary and Future Plans

• Early FPD stand-alone analysis shows that
  detectors work,
• will result in elastic dN/dt publication
  (already 1 Ph.D.)
• FPD now integrated into DØ readout (detectors
  still work)
• Commissioning of FPD and trigger in progress
• Full 18 pot FPD will start taking data after
  shutdown (12/03)
• Tune in next year for first integrated FPD
  physics results