why study diffractive w boson?. data samples z boson sample: start with run1b z ee candidate sample...
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Why study Diffractive W Boson?Why study Diffractive W Boson?
Data SamplesData Samples
Z boson sample: Start with Run1b Z ee candidate sample
Central and forward electron W boson sample: Start with Run1b W e candidate sample
hep-ex/0308032;Accepted by Phys. Lett B
Multiplicity in W Boson EventsMultiplicity in W Boson Events
-2.5 -1.5 0 1.1 3.0 5.2
Minimum side
Peak at (0,0) indicates diffractive W boson signal (91 events)
Plot multiplicity in 3<||<5.2
W Boson Event CharacteristicsW Boson Event Characteristics
MT=70.4
ET=36.9
ET=35.2
Standard W Events Diffractive W Candidates
ET=35.1
ET=37.1
MT=72.5
Observation of Diffractive W/ZObservation of Diffractive W/Z
Observed clear Diffractively produced W and Z boson signals
Background from fake W/Z gives negligible change in gap fractions
Sample Diffractive Probability Background All Fluctuates to Data Central W (1.08 + 0.19 - 0.17)% 7.7Forward W (0.64 + 0.18 - 0.16)% 5.3All W (0.89 + 0.19 – 0.17)% 7.5All Z (1.44 + 0.61 - 0.52)% 4.4
ncalnL0
Diffractive W and Z Boson Signals
Central electron W Forward electron W
All Z
ncalnL0
ncal
nL0
DØ Preliminary
DØ/CDF ComparisonDØ/CDF Comparison
CDF {PRL 78 2698 (1997)} measured RW = (1.15 ± 0.55)% for ||<1.1 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 ||<1.1
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 collaborations:DØ central jets 18% (q) 40%(g)CDF central B 22%(q) 37% overallCDF J/ 29%
It will be interesting to see Run II diffractive W boson results!
Run I Gaps Run I Gaps
• Pioneered central gaps between jets, 3 papers, 3 Ph. D’s
• 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
Run II Improvements 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
E
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 gaps+jets
Double pomeron with gaps
Gap tags vs. proton tags
Topics in RED were studied
with gaps only in Run I
<100 W boson events in Run I, >1000tagged events expected in Run II
DØ Run II Diffractive TopicsDØ Run II Diffractive Topics
Run II Rapidity Gap SystemRun II Rapidity Gap System
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
VC: 5.2 < < 5.9
LM: 2.5 < < 4.4
Forward Proton Detector LayoutForward Proton Detector Layout
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 < t < 3.0 GeV2) never before explored at Tevatron energies
Allows combination of tracks with high-pT scattering in the central detector
D SQ2Q3Q4S A1A2
P1U
P2I
P2O
P1D
p p
Z(m)
D2 D1
233359 3323057
VetoQ4Q3
Q2
Castle DesignCastle Design
50 l/s ion pump
Beam
Worm gear assembly
Step motor
Detector
• 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
Thin vaccum window
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.
Castle StatusCastle Status
AcceptanceAcceptance
Quadrupole ( p or )p
Dipole ( only)p
MX (G
eV)
450
400
350
280
200
GeV2
GeV2
450
400
350
20
200
MX (G
eV)
Geo
met
ric
A
ccep
tan
ce Dipole acceptance better at low |t|, large Cross section dominated by low |t| Combination of Q+D gives doubletagged events, elastics, better alignment, complementary acceptance
FPD Detector DesignFPD 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
0.8 mm
3.2 mm
1 mm
17
.39 m
m
17.39 mm
UU’
XX’
VV’
Trigger
Detector ConstructionDetector ConstructionAt 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 PMT’s is attached.
• 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.
P2 Quadrupole castle withup and down detectors installed
Detector StatusDetector Status
M.Strang
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.
Pot Motion SoftwarePot Motion Software
FPD Trigger and ReadoutFPD Trigger and Readout
Stand-alone DAQStand-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 PMT’s, 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 MAPMT’s.
•With this configuration we can read the fiber information of only two detectors, although all the trigger scintillators are available for triggering.
In-time hits in AU-PD detectors, no early time hits, or LM or veto counter hits
A1U A2U
P2DP1D
P
Pbar Halo Early Hits
LMVC
bp
bfpxp
bpp
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
Elastic TriggerElastic Trigger
Segments to HitsSegments to Hits
yx
10
ux
v
Segments
(270 m)
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
=p/p should peak at 0 for elastic
events!!Dead Fibers due to cables that have since been fixed
P1D
P2D
beam
Y
X
Y
Reconstructed
beam
Initial ReconstructionInitial Reconstruction
DØ Preliminary
Spectrometer AlignmentSpectrometer Alignment
Good correlation in hits between detectors of the same spectrometer but shifted from kinematic expectations– 3mm in x and 1 mm in y
P1D x vs. P1D x (mm) P1D y vs. P2D y (mm)
DØ Preliminary
After alignment and multiplicity cuts (to remove background from halo spray):
Events are peaked at zero, as expected, with a resolution of = 0.019
Elastic Data DistributionsElastic Data Distributions
dN/dtdN/dt=p/p
Acceptanceloss Residual halo
contamination
The fit shows the bins that will be considered for corrected dN/dt
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 thecontribution of the unsmearing errors in progress
219.002.4 GeVb
“Final” dN/dt Results“Final” dN/dt Results
Dr. Jorge Molina, (LAFEX, Brazil)defended his thesis on these results 10/31/03 (first FPD thesis!)
Dipole TDC ResolutionDipole TDC Resolution
Can see bunch structure of both proton and antiproton beam
Can reject proton halo at dipoles using TDC timing
CDF does not have this capabilityD1 TDC
D2
TD
C
p
p halo frompreviousbunch
Standalone Readout vs. AFE ReadoutStandalone 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
Dipole Diffraction ResultsDipole Diffraction Results
Geometrical Acceptance 14σ (Monte Carlo) Data
|t| (GeV2 )
Flat-t distribution
0.
0.02
0.06
0.04
0.08
|t| (GeV2 )
MZ all
MZ gap
Tagged Z event in FPD
Event Display
gapmuons
Run II Diffractive Z → µµRun II Diffractive Z → µµ
Summary and Future PlansSummary 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