the d0 detector upgrade and physics with d0 in...
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John Ellison University of California, Riverside
The D0 Detector Upgrade andPhysics with D0 in 2000
• Introduction– Detector upgrade motivation
• The D0 Upgrade– Overview
– Elements of the Upgrade
– Details of the Upgrade systems
• Physics with the D0 Upgrade– Emphasis on electroweak and top
physics
• Conclusions
John EllisonUniversity of California, Riverside
John Ellison University of California, Riverside
• Motivation for upgrading D0:
1) Enhance physics capabilities
2) Luminosity Increase• D0 was designed for operation at 1030 cm-2 s-1
• Run II designed to ultimately achieve 2x1032 cm-2 s-1
3) Bunch structure change• Present minimum bunch spacing is 3.5 µs
• Run II will start with 396 ns minimum bunch spacingand eventually reach 132 ns
Introduction
John Ellison University of California, Riverside
Tevatron Upgrades
• Fermilab Tevatron Improvements– Linac upgrade, main injector, new antiproton storage
ring, pbar source improvements
• Detector challenges– large occupancies and event pile-up
– radiation damage– current L1 trigger takes ~ 3 µs
• Physics opportunities– precision measurements at high pT: top mass, mW, di-
bosons, Higgs search,...
– new phenomena: SUSY,...
– additional capabilities at low pT: B-physics
Ib (93-95) II (99) TeV33
Typ. Lum. (×1032 cm-2 s-1) 0.16 2.0 10.4Energy (GeV) 900 1000 1000Bunches 6 36 108Bunch spacing (ns) 3000 396 132Interactions / crossing 2.6 5.3 9.1
John Ellison
University of C
alifornia, Riverside
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John Ellison University of California, Riverside
The D0 Upgrade - Tracking
• Silicon Tracker– Four layer barrels (double/single sided)
– Interspreced double sided disks– 793,000 channels
• Fiber Tracker– Eight layers sci-fi ribbon doublets (z-u and z-v)
– 74,000 fibers with VLPC readout
• Solenoid– 2T super-
conducting
• Central Preshower– Scintillator strips,
stereo,WLS fiber readout
– 6,000 channels
• Forward Preshower– Scintillator strips,
stereo,
WLS readout– 16,000 channels
η
η = 1.7
John Ellison University of California, Riverside
Silicon Tracker
• Performance Goals– Provide very high resolution measurements of particle
tracks near the beam pipe
a) measurement of charged particle momenta
b) measurement of secondary vertices foridentification of b-jets from top and for b-physics
– Track reconstruction to η = 3– Point resolution of 10 µm
– Radiation hard to ~ 1 Mrad
– Maximum silicon temperature <15o C
7 barrel sections
FP
12 Disks“F”
8 Disks“H”
η = 3
John Ellison University of California, Riverside
Bar
rel v
iew
in r
-φ p
lane
F-d
isk
view
in r
-φ p
lane
Sili
con
Tra
cker
John Ellison University of California, Riverside
Silicon Tracker - Detectors
• Single and double-sideddetectors
• 50 µm pitch
• axial and 2o / 90o
stereo in barrel
• AC-coupled, Si02capacitors
• Polysilicon
resistors2.5 MΩ
• Radiation hardto >1Mrad
1
10
102
103
0.1 1 10 100 1000
Cap
acit
ance
(pF
)
before irradiation
after irradiation(~1Mrad)
Frequency [kHz]
Detector 1265-15-AStrip 11
0
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80Reverse Bias Voltage [V]
Res
ista
nce
[MΩ
]
Effective polysilicon resistanceAfter irradiation (~1 Mrad)
John Ellison University of California, Riverside
SVX IIe Chip
Each channel:• Integrator
– risetime adjustable from 100 ns to > 400ns
• Noise resultsσ = 450 e– + 65 e– / pF 105 ns risetimeσ = 283 e– + 49 e– / pF 320 ns risetime
• Analog pipeline (32 cells) to store signalswhile L1 trigger is formed
• 8-bit ADC digitizes signal on-chip
• Sparse readout• Power 3 mW / channel typical
128channels
John Ellison University of California, Riverside
Ladder Production
• Single-sided ladder production has begun
• So far, we have ≈100 partially completed ladders
• Awaiting “HDI” flex circuits
John Ellison University of California, Riverside
Silicon Test Beam Results
• Test beam measurements of the performance of thesilicon detectors (June − September 1997)
125 GeV Pions
S/N ≈ 19:1
• Cluster chargedistribution
• Positionresolution
σ ≈ 9 µm
John Ellison University of California, Riverside
Scintillating Fiber Tracker
• Two Main Functions
1. With Silicon system
Track Reconstruction Momentum measurement
over η = ± 1.7
2. Fast Level 1 Triggering
combining information from muon and preshowersystem: single e, µ triggers
Z → µ+µ- + 1 min bias
Run 34 Event 2506/02/96 14.20.32
John Ellison University of California, Riverside
SFT Specifications
• Performance Strengths– Fast Response– High Resolution / granularity
– Level 1 trigger information
• 830 µm diameter fiber• 8 barrels: r = 20 → 51 cm
– 8 Axial Doublets
– 8 Stereo Doublets (constant pitch ≈ 2o)
– 4X (zu) + 4X (zv)
• Active length 2.8 m
• η coverage to 1.7• Approximately 74k channels
• Non active fiber (7-11 m) brings light to photodetectors(VLPCs)
SA
John Ellison University of California, Riverside
1 photoelectron
Readout - Visible Light PhotonCounter
• VLPC– HISTE I-III developed under SDC– HISTE IV-VI D0 initiative
• Si:As device• Excellent performance
– Hiigh QE - 80%
– High gain - 70,000
– Low noise - 10 kHz– Fast response, τr < 100 ps
– 8 element array
2
3
4
Pulse Height (ADC channels)
John Ellison University of California, Riverside
System Performance
A cosmic ray test of 3 superlayers, 3072 channels(HISTE IV), was performed in 1994-95.
Results:– 8.5 photoelectrons per fiber (light yield needed for full
tracker efficiency = 2.5 pe)
– Doublet position resolution ~ 100 µm
– Doublet efficiency > 99.9%
(a)
Pulse height (p.e.)
0
10000
20000
30000
40000
50000
0 5 10 15 20 25 30 35 40
(b)
σ=92µm
δx (mm)
0
500
1000
1500
2000
2500
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
8.5 p.e.
John Ellison University of California, Riverside
• Specifications– Provides fast energy and position measurements
for electron trigger and offline electron id
– 2X0 preradiator (solenoid + Pb)– Triangular scintillator strips (axial and 20o)
– VLPC readout
– Position resolution < 1.4 mm for 10 GeV electron
Central Preshower
Solenoid
SciFi
Silicon
Calorimeter
John Ellison University of California, Riverside
Forward Preshower
• Specifications– provides a factor of 2-4 rejection for electron trigger in
forward region 1.4 < |η| < 2.5– same technology as central preshower
John Ellison University of California, Riverside
Central Muon System
• Wide Angle Muon Proportional Drift Tubes (PDT)– use existing PDT’s for |η| < 1
– use faster gas (Ar-CF4-CH4) - drift time = 450 ns
– replace front-end electronics for deadtimelessoperation
• Cosmic Ray Scintillator– rejects out-of-time backgrounds
– add bottom layer to complete coverage
– time resolution 2.5 ns
• A-φ Barrel Scintillator– rejects out of time background (σ = 1.6 ns)
– provides φ measurement to match muon tracks to fibertracker
– 630 counters (80 in φ X 9 in z) matched to trigger φsegmentation
John Ellison University of California, Riverside
Forward Muon System
• Forward Trigger Detectors– scintillator pixel counters provide time information and
match muon tracks in fiber tracker– 3 layers to reduce combinatorics
– 1/2” scintillator with WLS bar readout
• Forward Tracking Chambers– 3 layers of mini-drift tubes 1 < |η| < 2
– 1 x 1 cm2 cells in 8 cell extrusions– operated in proportional mode
– 60 ns drift time
– no measurable aging of materials or gas
– prototype measured in D0 run I (high rate)
John Ellison University of California, Riverside
Shielding
• Reduce backgrounds in muon detectors,
especially at low η• Main source is scattered proton and antiproton
fragments which interact with the exit of thecalorimeter, beam pipe and low beta quadrupoles
• Shield comprised of iron (39 cm), polyethylene(15 cm),lead (15 cm) casing surrounding beam pipe
WithoutShielding
EM energydeposition(GeV/cm3/sec):
With Shielding
r (cm)
z (cm)
John Ellison University of California, Riverside
Tracker Performance
• pT resolution vs pseudorapidity
• Important addition to D0 physics capabilities:– E/p matching for electron identification
– Muon momentum resolution– Charge sign determination
– Calorimeter calibration
John Ellison University of California, Riverside
Tracker Performance
• 2-d (r-φ) impact parameter resolution vs pseudorapidity
• Tagging efficiency per event vs cut on signed impactparameter significance b±/σ
b±/σ > 3 cut accepts:
50% of ttbar events2% of W+jets bckgnd
John Ellison University of California, Riverside
Upgrade Performance
• Muon System– lower thresholds (no prescale): single muon pT > 8
GeV/c, dimuon pT > 3GeV/c
– reduced backgrounds and triggering with additionalshielding
• Calorimeter– comparable performance at 2x1032 compared to
present performnace at 2x1031 (actually 17% worse)
– ability to calibrate (E vs p now available)
• Triggering– increase bandwidth: 10 kHz L1 accepts, 800 Hz L2
accepts, 10-20 Hz to tape -- more than an order ofmagnitude improvement over present system
• Preshowers– electron identification (central and forward)– forward electron triggering: additional x3-5 rejection
over calorimeter alone
John Ellison University of California, Riverside
Measurement of the W Boson Mass
• Fundamental parameter of the SM, sensitive to topquark and Higgs boson radiative corrections:
b
H0
WW
t
WW
−∆r ∝ Mt
2
∆r ∝ ln MH
• Current measurement from D0 (Run 1a +1b):
MW = (80.43 ± 0.11) GeV/c2
• How does this improve in Run 2 and beyond?
GF =
p2M2
W
1 M2
W
M2
Z
[1 + r (;MW ;MZ ;MH ;mt)]
r = r() +r(s) +r(2) + : : :
John Ellison University of California, Riverside
Current Results: MW vs Mt
80.1
80.2
80.3
80.4
80.5
80.6
80.7
140 160 180 200mt (GeV)
mW
(G
eV)
100
250
500
1000
INDIRECTLEP + SLC
80.1
80.2
80.3
80.4
80.5
80.6
80.7
140 160 180 200
MSSM
DIRECTmW: UA2+CDF+D0+LEP2mt: CDF+D0
SM Higgs M
ass (G
eV)
John Ellison University of California, Riverside
MW Errors
• Most errors scale like 1/√N, where N = no. events
• Multiple interactions result in smearing of thetransverse mass distribution:
0
500
1000
1500
2000
2500
3000
3500
4000
40 50 60 70 80 90 100 110 120
IC = 1IC = 3IC = 9
Transverse Mass (GeV/c2)
Eve
nts/
GeV
• Resulting error scales as √(IC / N) where IC =number of interactions per crossing
IC ≈ 3 for Run 2IC ≈ 9 for TeV33
John Ellison University of California, Riverside
Precision Measurement of MW
• Some errors do not scale as √(IC / N), e.g.uncertainties due to
– parton distribution functions and pTW model
– higher order electroweak corrections
Scaling of W-mass error
1
10
10 2
10 102
103
104
105
∫ L dt (pb -1)
∆MW
(M
eV)
Run 1A, CDF, DØ, UA2 (preliminary)
Run 1b, CDF, DØ (anticipated)
Scaling
+ resolution
+ systematics
• TevatronRun II (1 fb-1) ∆MW ≈ 50 MeV/c2
TeV33 (10 fb-1)∆MW ≈ 30 MeV/c2
TeV33 (100 fb-1) ∆MW ≤ 20 MeV/c2
• LEP II500 pb-1 ∆MW ≈ 40 MeV/c2
John Ellison University of California, Riverside
Anomalous WWγ Couplings
• Can probe the WWγ coupling via p pbar → Wγ → ν γ• Sensitive to the W magnetic dipole and electric
quadrupole moments:
1 fb-1
|∆κγ0| < 0.38
|λ| < 0.12
10 fb-1
|∆κγ0| < 0.21
|λ| < 0.057
• Limits for run II at 95% CL:
( )µ κ λγ γWW
e
m= + +
21 ( )q
e
mWW
= − −κ λγ γ
TevatronRun II:
Comparable (and complementary) to LEP II
with Ecm = 190 GeV and 500 pb-1
John Ellison University of California, Riverside
Anomalous ZZγ and Zγγ Couplings
• D0 limits from run 1a for Λ = 0.5 TeV at 95% CL(prelim.):
| h30,10 Z,γ
|< 0.9
| h40,20 Z,γ
| < 0.2
. . . utilizes p pbar → Ζγ → ννγAdvantages compared with γ mode:
– absence of radiative decay– High branching ratio B(Z→νν) = 20%– High detection efficiency
-0.007
-0.006
-0.005
-0.004
-0.003
-0.002
-0.001
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
-0.15 -0.1 -0.05 0 0.05 0.1 0.15
hZ30 (h
γ30)
hZ 40 (
hγ 40)
95% C.L. limits
1 fb-1
10 fb-1
100 fb-1
SM
ZZγ unitarity limitsZγγ unitarity limits
ΛFF = 1.5 TeV
pp_ → νν
_γ, √s
¬ = 1.8 TeV
In Run II the Tevatronwill probe the couplingsat the level ofh0
Z,γ ~ 10-3
sensitive to radiativecorrections involvingnew particles, e.g.Higgs, SUSY,…
as well as Zcompositeness
Compare: LEP limits ≈0.5
John Ellison University of California, Riverside
Higgs Search
• What is the discovery reach for Higgs at theTevatron?
• Most promising modes are WH and ZH with H → bb
• TeV2000 study showed feasibility of detecting a lightHiggs in the WH → ν bb channel:
−
−
10 fb−1
mH = 80 GeV
signal
background
Two-Jet Mass (GeV)
WH → lν bb−
John Ellison University of California, Riverside
Higgs Search
• Snowmass 96 updated WH study and included ZHchannel with Z → l+l− or νν; H → bb
• Expected numbers of events for 30 fb−1:
For an integrated luminosity of 30 fb−1 can observe aHiggs signal up to mH ≈ 125−130 GeV
mH = 100 GeV mH = 120 GeVWH Signal (S) 228 117Background (B) 789 456S=B 0.29 0.26
S=pB 8.1 5.5
ZH Signal (S) 92 51Background (B) 495 378S=B 0.19 0.13
S=pB 4.1 2.6
−
John Ellison University of California, Riverside
Search for Supersymmetry
• Gaugino pair production– cleanest signature is 3 leptons + missing ET
– upgrade provides good lepton acceptance andenhanced triggering on leptons at lower pT
• Sqaurk - Gluino pairs– D0 limit of 229 GeV for mq = mg is from decay
signature of multiple jets + mising ET
– improvements to trigger system will increase thebandwidth and allow unprescaled missing ET trigger
Current limits and mass reach for discovery in Run II:
~ ~
Signal Production cross-section
(over accessiblemass range)
Currentmasslimit
(GeV)
2 fb-1
(GeV)10 fb-1
(GeV)
squark and gluinopairs
5-1000 pb 229 390 400
Chargino -Neutralino pairs
0.5-10 pb 47 210 230
John Ellison University of California, Riverside
Summary
• The D0 Upgrade will allow us to take full advantageof the exciting physics program at the Tevatron withdata sets of > 2 fb-1
• All subsystems are now under construction and weare on schedule for Run II to begin in the spring of2000
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