TESTING THE STANDARD MODEL

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TESTING THE STANDARD MODEL AT THE
DØ EXPERIMENT -at present and in the
future
Tulika Bose for the
Columbia-D? group
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Outline
The Standard Model HEPs burning questions
The Fermilab Tevatron The D? experiment

Acknowledgement Hal Evans for letting me steal
many of his slides!
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Particles and forces
Force Boson MassGeV Strength
Gravity G 0 10-39
E-M ? 0 10-2
Weak W? 80.419 10-5
Z0 91.1882
Strong g 0 10-1 (MZ)
E-W Sym H0 gt113 mf2
Particle Particle Particle Chge Mass MeV Mass MeV Mass MeV Mass MeV
Leptons Leptons Leptons Leptons Leptons Leptons Leptons Leptons
?e ?? ?? 0 O(lteV) O(lteV) O(lteV) O(lteV)
e ? ? -1 0.5 0.5 105 1777
Quarks Quarks Quarks Quarks Quarks Quarks Quarks Quarks
u c t 2/3 15 1300 1300 174300
d s b -1/3 39 150 150 4400
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Standard Model the good and the bad

• Hugely successful !
• But lots of problems/unanswered questions
• 19 arbitrary parameters
• The origin of mass ?
• Matter/antimatter asymmetry?
• Gravity ?

The Feedback Loop
Trash
HEP Experiments
Particle Theory
SM
Eureka !
Beyond the SM ???
Surprises
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The question of mass
Why is there mass ? Why do some particles have
mass while others are massless? Why does, say a
top quark, have about 40 times as much mass as a
bottom quark? etc.
Electric
Sheldon, Glashow, Weinberg
EM
Maxwell
Magnetic
Electroweak
Massless Bosons
Weak
Peter Higgs to the rescue
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HEPs Most Wanted

• Invents a set of particles with very special
  properties
• their interaction with all the standard
  particles ? mass
• one new particle the Higgs boson

But where is the Higgs???
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Higgs in cartoons
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Whats the matter with antimatter ?

Right after Big Bang
Antimatter
Matter
But we exist!!! Where did the
anti-matter go?
But
?some asymmetry between matter and antimatter
connects the Universes matter dominance with
elem. pcles
Proton decay
Sakharov
Rapid expansion
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• Theoretical framework CKM matrix
• atleast 6 quark flavors ?
  complex phase Quarks ? CP Violation in B0, K0
  decays, Mixing
• Leptons ? Neutrino Oscillations neutrino
  mass, mixing CP

? ?
Is it zero or non-zero
accomodates but does not
explain it!!! amount of not enough
to account for matter dominance Alternate models
include other CP viol. effects
experiments sensitive to physics beyond the SM
SM
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The gravity of the situation
Hierarchy problem
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SUSY to the rescue???

• Supersymmetry
• adds a Superpartner for every SM pcle
• and 5 Higgs h0, H0, A0, H
• Simplest SUSY models require
• Mh lt 135 GeV (!!!)

Standard Model Standard Model Superpartners Superpartners
Particle S Sparticle S
½ 0
½ 0
½ 0
1 ½
0 ½
1 ½
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Answers???

• new interactions analogous to the color force
• new technicolor fermions like quarks at TeV
  scale
• SM particles interact with techi-fermions
• the interaction ? mass to the SM pcles

Technicolor
Hierarchy problem solved!
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Large extra dimensions ??
String Theory
Graviton
Collision energy ?
disappears
Extra dimensions of a megaverse
Non-conservation of energy
sign of new physics
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The strategy

• Take your favourite beyond the SM theory
• it looks like the SM at low energies ,
  differences only at high E
• small corrections to SM predictions
• ? We need to look more precisely and at higher
  energies

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The truth is out there

• Precision measurements
• Electroweak Physics
• large sample of W Z bosons
• W mass (dM(W) 30 MeV/c2)
• W width, W/Z production properties
• tri-linear gauge boson couplings
• Any deviation ? new physics !
• Top Physics
• top only produced at the Tevatron
• top mass (dM(top) 2.8 GeV/c2)
• top pair production cross-section
• single top production
• W mass Top mass constrain Higgs mass

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The beauty of physics

• - Large rate
• CP violation and CKM angles
• Bs mixing
• Cross sections
• Rare decays

at 2 TeV
at Z0
at ?(4S)

• All species, including Bs, Bc, ?b, produced

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Tevatron
Fermilab Tevatron Circumference 4 mile 20
feet underground ECM2 TeV
collisions
p (E 1 TeV)
p (E 1 TeV)
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Tevatron

• Protons
• H- Source produce
• Linac 400 MeV
• Booster 8 GeV
• Main Injector 150 GeV
• Tevatron 980 GeV

• Antiprotons
• p-Ni ? s produce
• Accumulator 8 GeV
• Main Injector 150 GeV
• Tevatron 980 GeV
• Recycler recovery

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Tevatron upgrade
Linac upgrade, main injector, new antiproton
storage ring
Ib 92-96 IIa 01-03 IIb 03-07
Tot. Anti-p (x1012) 0.3 1.1 4-11
Bunches 6x6 36x36 140x103
Spacing ns 3500 396 132
E-CM GeV 1800 1960 1960
Typ. Lumi. cm-2s-1 (x1032) 0.016 0.86 25.2
Lumi/week pb-1 3.2 17.3 40105
Tot Lumi fb-1 0.125 2 1520
Ints/Xing 2.5 2.3 1.94.8
ÞExtensive upgrade of the DÆ detector
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The layers
General purpose high energy physics detector
T.Bose
10/12/01
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The international coalition

• gt500 people from 50 institutions (17
  countries)
• Run I (92-96)
• 104 publications
• EW Physics
• Top Physics
• Top quark co-discovered (w/ CDF) March 95
• New Phenomena
• B Physics
• QCD
• Run II started March 1, 2001 !
• Detector rolled in.
• All component detectors installed
• Electronics final production/installation

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On the home front
Faculty Post-docs Graduate students
Hal Evans John Parsons Mike Tuts Hal Evans John Parsons Mike Tuts Leslie Groer Christos Leonidopoulos Georg Steinbrueck Tulika Bose Shaohua Fu Mingcheng Gao Burair Kothari Jovan Mitrevski
Responsibilities
Hal Evans L2 muon trigger, Si Track Trigger, B phys group co-convener, Run 2b Cal. Trigger Upgrade leader
Leslie Groer Detector Commissioning
John Parsons Top/Higgs group
Georg Steinbrueck Electroweak group co-convener
Mike Tuts Calorimeter electronics, Run 2a upgrade co-leader
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DÆ upgrade
Forward Scint
Central Scintillator
Forward Mini-drift chambs
Central PDTs
Shielding
Calorimeter
Tracking Solenoid,Silicon,Fiber
Tracker,Preshowers
New Electronics,Trigger,DAQ
T.Bose
10/12/01
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The real thing!
T.Bose
10/12/01
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Tracking
Readout
VB
Si wafers charged pcle passes thru Si Þelectrons
holes charge collected on strip readout Þpcle
position Þpoints for track fit
p
50 mm

-
300 mm

-
n SiO2

-
n
reverse biased diode
Si Detector
Ionization of atoms by charged particles
electrons knocked out trajectory deduced by
measuring ionization at many points along the
path curvature of track measured Þparticle
momentum amount of ionization per unit length
(dE/dx) depends on particle type, p Þparticle
type identified
Tulika Bose
10/12/01
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Tracking upgrade

• Silicon Microstrip Tracker (SMT)
• Central Fiber Tracker (CFT)
• 2T superconducting solenoid

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SMT
Silicon Microstrip Tracker (SMT)

• 6 Barrels 4 layers of Si microstrip detectors
• axial strips (10mm resolution)
• Layers 1, 3 double-sided 90o strips (30mm
  res.)
• (single-sided on 2 outer
  barrels)
• Layers 2, 4 double-sided 2o stereo (15mm
  res.)
• 12 F-disks 4 H-disks

• 793k Channels
• SVX IIe Readout
• L2 Trigger (02)

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SMT CFT

• SMT
• high resolution measurements of particle tracks
  near the beam pipe (10mm res.)
• measurement of charged particle momenta
• measurement of secondary vertices for
  identification of b-jets from top, Higgs, and for
  b-physics
• CFT (Scintillating fiber tracker)
• Fibers (830 ?m) -Axial Stereo (3o) on 8
  concentric cylinders
• light from the fibers converted into electrical
  pulses by Cryogenic (LHe) Photon
  Detectors (new)
• VLPC Readout 77k Channels (SIFT SVX IIe)
• Hit Resolution (100 ?m)

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Calorimeters

• Calorimeter
• high density material particles slow down
  stop
• energy deposited measured
• showers
• shape of shower distinguishes e, g from hadrons
• electromagnetic electrons, positrons, photons
• hadronic hadrons which penetrate EM Cal.
• Detector unchanged from Run I
  (U-LAr)
• New electronics to cope with BX
  frequency

10/12/01
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Chasing muons

• Muon detectors
• tracking muons, measure momentum
• drift chambers
• parallel anode wires stretched between two
  cathode planes
• elec liberated by ionization moves towards anode
• energy gain further ionization avalanches of
  elec ions
• drift time (collection time of avalanches)measure
  of position
• scintillation counters
• excitation of atoms by ionizing
  particlesluminescence
• light converted into electrical pulses by Visible
  light photon counters

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Pictures
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Physics Rates
Physics Rates Physics Rates Physics Rates
Process X-Sector BR Rate (L2x1032)
Beam Xing 7.5 MHz (132ns)
Inelastic 50 mb 50 ?b 10 MHz 10 kHz
?WX ?ZX?bbX 22 nb 1 nb 4.4 Hz 0.2 Hz
?e/? jets ?only jets 7.2 pb 100 35 44 5 / hour
425 fb 22 56 7 / day
Too Much Physics
M(H) 100 GeV
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Signal Vs. Background

• Signals
• High PT Leptons
• W/Z, b...
• High ET Jets
• Massive Objs
• Missing ET
• us, LSP
• Displaced Vertices
• bs...

• Backgrounds
• Low ET Jets
• ET Balanced
• No High PT Leptons
• No Displaced Vertices

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Where is the needle?
Out of every trillion proton-antiproton
collisions, about ten top-antitop quark pairs are
produced!!!
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DÆ Trigger System

Crossing frequency 7MHz
p

p
But data acquisition rate is 50 Hz
ÞNew 3 Level Trigger System
L3
L1
L2
50 Hz
7 MHz
10 kHz
1 kHz
Decision time 100ms
Decision time 25ms
Decision time 4.2ms

• Single Sub-Dets
• Towers, Tracks, ET-miss
• Some correls
• Not deadtimeless

• Correlations
• Calibrated Data
• Physics Objects e,?,j,?,ET-miss

• Simple Reco
• Physics Algos

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L1 L2
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The importance of beauty

• Some Run II physics programs
• Search for the Higgs Boson ( )
• Studies of the top quark ( )
• B Physics (CP violation etc.)
• Search for new particles
• b quarks appear in the final
  state
• Tagging of b-quark jets is of utmost importance
  !

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Impact parameter
Interesting physics is tagged by b-quarks
Impact parameter is a good b-tag
Need sensitivity at level of 10's of microns
CFT (100mm res.) , SMT (10mm res.)
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Trigger thresholds

• Momentum Resolution
• Interesting evts ? High PT
• Bgrd dominated by Low PT

• soft thresholds allow a fraction of the particles
  with pT below threshold to fire (BAD!)
• increase in trigger rate
• sharp threshold cuts out this background below
  threshold
• decrease in trigger rate (VERY GOOD!)
• precise tracking ? more efficient use of the
  data acquisition bandwidth

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Physics benefits

• New Phenomena
• increase Higgs sensitivity 20 ZH???bb
• double sensitivity hA?bbbb
• Top
• Trigger on Z?bb (increase yield x6)
• Cut Mt systematics in half
• B-Physics
• Increase B??KS yield by 50

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Silicon Track Trigger

STC
FRC
Tracks from CFT
Define search region in Si
TFC
Re-fit track with Si clusters
Associate clusters to tracks
Data from SMT detectors
Form Clusters
Global L2 Trigger
via L2CFT

• impact parameter trigger
• Res 30mm at PT2GeV 15mm at
  PT15GeV
• improved momentum resolution (factor 2-3)
• sharper thresholds

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The STT Integration
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Status
Dates Tevatron DØ
1/Mar/01 Official Run II Start Detector Open
3/Apr/01 First Colliding Beam (1x8) Timing In Detectors
27/Apr/01 36x36 stores Final mu-chamber gas
3-17/May/01 2-week shutdown All Si cabled Close det.
May-Aug/01 36x36 stores w/ shutdowns Install electronics as avail
Jul/01-Sep/01 L2 Cal and Muon
Oct/01-Nov/01 1-month shutdown Fully instrument
Nov/01-2003 Run IIa 2 fb-1
Jun/2002 STT installed
2003 Long Shutdown Install new silicon, etc.
2003-2007 Run IIb gt15 fb-1
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Status
Action
Dates
Continue 36 x 36 running With detector as
described before.
July 26
Done

• Increase L3 rate from 4 Hz to 100Hz
• Complete L1 Cal
• Start bringing up L2 trigger partially

By August 15
In Progress
NOW
Done
Run until Oct 8
Take data commission Offline software with real
data Calibration Alignment
Install AFE8 boards other completion
Oct 8 - Nov 16
In Preparation
36x36 stores Commission CFT L1 track trigger
November
36x36 fine tune stabilize ? stable operation
December January 2002
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Data!
Muon
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Di-muon candidate
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Outlook

• Exciting times ahead!
• D? is the place to be at!

DØ vs. The Standard Model DØ vs. The Standard Model DØ vs. The Standard Model DØ vs. The Standard Model DØ vs. The Standard Model DØ vs. The Standard Model
Precision (2 fb-1) Precision (2 fb-1) Searches (20 fb-1) Searches (20 fb-1) Quark M vs Weak (2 fb-1) Quark M vs Weak (2 fb-1)
MW 30 MeV HSM 180 sin2? 0.03
Mt 1.6 GeV tan?,MA most 5? xs 30
Vtb 12 rare top ?1040 K??- 700 evts
etc etc etc
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I.P. resolution with STT

• I.P. Resolution 30 mm at pT2GeV
• 15 mm at pT15GeV

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Tulika Bose
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Momentum resolution

• Si precision 10 mm , CFT precision 100 mm
• improved momentum resolution (factor 2-3)

Tulika Bose
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Improved rates

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