the d0 detector upgrade and physics with d0 in...

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


• 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


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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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


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


Bar

rel v

iew

in r

-φ p

lane

F-d

isk

view

in r

-φ p

lane

Sili

con

Tra

cker


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)


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


Ladder Production

• Single-sided ladder production has begun

• So far, we have ≈100 partially completed ladders

• Awaiting “HDI” flex circuits


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


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


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


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)


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.


• 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


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


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


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)


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)


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


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


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


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) + : : :


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)


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


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


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


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


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−


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

−


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


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

the d0 detector upgrade and physics with d0 in...

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