Transcript News from the Microscopic Universe and the Energy Frontier

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High Energy Physics at NIU
Jerry Blazey
Northern Illinois University
Departmental Colloquium
October 8, 2009
Cosmic Context
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Now (15 billion yrs)
Stars form (1 billion yrs)
Atoms form (300,000 yrs)
Nuclei form (180 seconds)
Protons and neutrons (10-10 s)
Domain of current accelerators
~10-12 seconds
The Universe at 10-12 s 
The Standard Model
• The essence (but vague): Bits of matter stick
together by exchanging stuff.
• The great achievement of particle physics is a nice
tidy model that describes all particles and particle
interactions. The model includes:
– 6 quarks (the particles in the nucleus) and their
antiparticles.
– 6 leptons (of which the electron is an example)
and their antiparticles
– 4 force carrier particles
• More precisely: “All known matter is
composed of composites of quarks
and leptons which interact by
exchanging force carriers.”
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The Bits: Periodic Table of Fundamental Particles
+2/3
-1/3
0
-1
Mass 
All point-like (down to
10-18 m) spin-1/2
Fermions
Families reflect
increasing mass and
a theoretical
organization
u, d, n, e are
“normal matter”
These all interact by
exchanging spin 1
bosons
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The Stuff: Standard Model Interactions
Mediated by Boson Exchange
Unification
10-37 weaker
than EM, not
explained
Explained by Standard Model
We could stop here ….
There are many open and compelling
questions that can be addressed by
particle physics…
• How do particles actually get mass?
• Are there hidden dimensions (perhaps
explaining the weakness of gravity)?
• What is the nature of dark matter and dark
energy?
• What is the origin of the matter –
antimatter asymmetry?
All properties of the submicroscopic world!
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How do we explore these ideas? First, with a particle source, for
example with the Fermilab Proton-Antiproton Collider or Tevatron
Chicago
Batavia, Illinois
DØ
DØ
You are here
DØ
Booster
1)Hydrogen Bottle
2)Linear Accelerator
3)Booster
4)Main/Injector
5)Antiproton Source
6)Tevatron @ 2 TeV
Tevatron
p source
Main Injector
& Recycler
p
p
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Second, with a particle detector,
here’s a schematic example
Tracking system
Magnetized volume
Interaction
point
p
Calorimeter
Muon detector
Induces shower
in dense material
p
Innermost
tracking layers
use silicon
EM layers
fine sampling
Hadronic
layers
Absorber material
Electron
Experimental signature
of a quark or gluon
Jet: q or g
Muon
Bend angle  momentum
“Missing transverse energy”
Signature of a non-interacting (or weakly
interacting) particle like a neutrino
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Calorimeters
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Tracker
A Real Experiment: DZero
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Proposed 1982
First Run: 1992-1995 1.8 TeV
Upgrade: 1996-2001
Run II: 2002-2011 2.0 TeV
Muon
System
antiprotons
20 m
Electronics
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Inner Tracking
Electron
Quark or gluon
Jet
Muon
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Collider Physics is International…
• 17 countries
• 88 institutions
• 500 physicists
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And 24/7….
• Proton-antiprotons collide at 7MHz or
seven million times per second
• Tiered electronics pick successively
more interesting events
– Level 1 2 kHz
– Level 2 1 kHz
• About 100 crates of electronics readout
the detectors and send data to a Level
3 farm of 100+ CPUs that reconstruct
the data
• Level 3: ~100 events or ~25 Mbytes of
data to tape per second
• Per year: 1 Trillion events
Event Analysis
• Events are “reconstructed”
offline by farms of ~100
CPUs.
• Each detector samples
position, energy, or
momentum, 1M+ channels
• Then computers build or
reconstruct full event
characteristics based
upon these samples
• Interesting events or
signals are culled from
the background usually
100’s out of millions.
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A Sample Event:
Ze+e-
p
p
q
q’
l
Z
l
Sample Distribution: Z mass
CDF and DØ Run II
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Collect events and calculate mass for each event, then plot
distributions
Extract or measure properties such as mass or production rate
as a function of beam brightness or luminosity.
For example 1pb-1 of luminosity means 1 event will be
produced for a process of 1pb cross section.
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A Second Example: the Higgs Particle
(it was on the “compelling” list)
• Electroweak unification required the assistance of
the Higgs field.
• This field interacts with all other
particles to impart mass - think
of walking through molasses.
• The field is a microscopic
property of space-time, at
least one real particle will result,
as an excitation of the field.
• The collider programs at
Fermilab and CERN
are
dedicated, in part, to
the discovery and
study of this particle.
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Tevatron Searches
• For any given Higgs mass, the
production cross section,
decays are calculable within
the Standard Model
• There are dozens of ongoing
searches in a number of
production and decay channels
• For example:
p
p
q
q’ W*
W
H
– At low mass the Higgs could decay
to a b quark/b antiquark pair and
– At high mass to a WW pair
• Combining all searches there
are no events above
background, so limits are set.
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Or turn it around… and look for a
signature relevant to several signals…
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Study events with 1 or 2
jets identified as coming
from b-quarks using
either the silicon vertex
detector or a muon
Require an energy
imbalance (“missing
energy”) --> IDs
neutrinos or possible LSP
Such events maybe
related to new physics:
for instance ZH or leptoquark production
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DZero History/Highlights
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1982 initial proposals
1983 D0 group formed
– 12 US institutions, 71 collaborators)
1986 NIU joins D0
1992-1996 Run I (100 pb-1)
1993 first top quark observed
1995 top quark discovered
1996-2001 upgrade
2001 Start of Run II
2006
– BS mixing and single top observed
– Precision measurements of top mass
2008
– First exclusion of Higgs Mass
2011 ~12 fb-1
Through 2015 analyses
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NIU/NICADD DZero Personnel
• Current Faculty/Scientists
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Pushpa Bhat (Fermilab)
Jerry Blazey
Dhiman Chakraborty
Sasha Dychkant
Mike Fortner
Dave Hedin
Sergey Uzunyan
• Current Students
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Martin Braunlich
Kenen Caymez
Diego Menezes
Rick Salcido
• Doctoral Degrees
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Mike Eads, Search for Massive
Stable Particles
Xiaofei Song, Search for second
generation leptoquarks
Andriy Zatserklyaniy, Search for
third generation leptoquarks
Sergey Uzunyan, Search for
third generation leptoquarks
Mike Arov, Measurements of
the top cross section in the tau
mode
• Master’s
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Linda Bagby, Layer 0 silicon
detector and Higgs search,
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NIU Contributions
Past (1986-2008)
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DESIGN: muon and trigger
systems
CONSTRUCT: calorimeter,
muon tracker, silicon vertex,
L2 trigger
DEVELOP: muon, tau, L2
trigger software
COORDINATE:
jet, muon, tau ID groups,
QCD, B, top, New Phenomena
physics groups
MANAGEMENT: trigger
upgrade and collaboration
Now
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Detector Operations
– Shifts
– L2 Expert
– Muon software
Analyses
– Studies of top quark decay
– Searches for new
phenomena.
• Standard model Higgs
• Extensions (MSSM) 
H+,H-,h0,H0,A0
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DZero Prospects
• Tevatron running extremely well
– Record integrated luminosity in the last year
– Just restarted after 12-week shutdown
– Six inverse femtobarns delivered (100 X top quark discovery)
• DZero detector operating smoothly
– Upgraded in 2006 to handle current high rates
– Still requires constant attention –
• four physicists on shift 24/7
• experts on call for every subsystem
• Calibration and analysis continuously under refinement.
• Continue running through 2010, probably through 2011 at
least
– Expect one more data doubling by end of 2011
– no more major shutdowns or upgrades planned – emphasis is on
physics, physics, physics
– Publishing ~1 paper/week