The Life of a Graduate Student Phenomenologist

1
The Life of a Graduate Student Phenomenologist

• Matt Bowen
• February 23rd, 2007
• Physics 528, UW

2
A Humble Outline

• Road to Glory 2001-2005
• Current project Measuring Vtb at the LHC
• A Day in the Life of
• Sagely Advice

3
In the Beginning...
Maybe Ill be a screenwriter...

• Fall 2001 Had no idea what I wanted to do
• Winter 2002 Thought about being a screenwriter
  in LA
• Worked with HEP group for a while
• Fall 2002 Did a reading course with Steve Ellis

4
Since then...

• January 2003 Began single top quark research
  with Steve and Matt Strassler
• Discovered how much fun research is
• professors have no idea what the right answer
  is and are sometimes dead wrong
• god, I love it when that happens
• April 2004 Spoke at Pheno 2004 conference in
  Madison, WI
• December 2004 Finished first paper

5
A Humble Outline

• Road to Glory 2001-2005
• Current project Measuring Vtb at the LHC
• A Day in the Life of
• Sagely Advice

6
Vtb in the Standard Model

• Fundamental parameter in the Standard Model of
  Particle Physics
• Never been directly measured

One Single Top Quark Production Channel
Top Quark Decay
Vtb
b
Vtb
t
ve
W
e
Focus on Single Top Quark Production, so...
7
Hadronic Collisions

• Initial state partons in collision are X,Y
  where X,Yg, u, u, d, d, s, s, c, c, b, b
• Each parton carries some fraction of protons
  total momentum
• 2 valence up quarks, 1 valence down quark

g
s
s
u
u
u
u
d
d
d
d
g
Proton
Proton
8
The Large Hadron Collider

• Just outside of Geneva
• 27 km ring with 7000 GeV proton beams colliding
• Due to turn on in 2007
• The ATLAS detector (UW is a member of this
  collaboration) is about the size of a 5-story
  building
• ATLAS alone has 150 universities from 34
  countries working on it

ATLAS Detector
My opinion Will be the coolest experiment in the
world!
9
What do Single Top Quark Events Look Like to
Detectors?
jet

• 1 lepton
• 1 neutrino
• 2 jets of energy

jet
b
t
neutrino
ve
W
e
not seen
lepton
Because Vtb appears in cross-section calculation,
measuring the cross-section for single top quark
production gives a measurement of Vtb

• Ideally, just count up number of single top quark
  events

10
What else has this signature?
Top quark pair production
W boson production with associated jets
jet
b
q
e
t
u
e
W
W
ve
ve
W-
s
jet
g
q
t
q
jet
c
jet
b
q
g
jet
jet
d
11
Signal and Background Calculations
Theoretical numbers of events for 100 fb-1
Ask for

• 1 lepton
• 1 neutrino
• 2 jets of energy

Any systematic uncertainty in the prediction of
top quark pair production will prevent discovery
(and measurement) of the signal
12
Top and Antitop Quark Production
Single Top Quark Production

• More up quarks in proton than down quarks leads
  to 70 more top quarks than antitop quarks

d
u
t
W
g
b
Single Antitop Quark Production
u
d
t
W-
g
b
Arrow are backwards!
13
Top Quark Decays

• Top quarks decay to positively charged leptons
• Antitop quarks decay to negatively charged leptons

b
Top Quark Decay
t
ve
W
e
Antitop Quark Decay
b
t
e-
W-
ve
14
Definitions

• N Number of events with only 1
  positively-charged lepton
• N- Number of events with only 1
  negatively-charged lepton
• ? N - N-
• Charge Asymmetry

Single Top Quark Production has a 25 charge
asymmetry
15
Charge Asymmetry Calculations

• Top pair production is largely charge symmetric
• Single Top Quarks have significant charge
  asymmetry to them
• This can be used to reduce systematic
  uncertainties and make a precision measurement of
  Vtb

Number of events for 100 fb-1
Done
16
A Humble Outline

• Road to Glory 2001-2005
• Current project Measuring Vtb at the LHC
• A Day in the Life of
• Sagely Advice

17
A Day in the Life of...

• Particle Theory (PT) group still have to teach
  10 hours teaching, 10 hours of research
• Regular weekly meeting with Matt and Steve
  sporadic meetings
• PT Seminar on Tuesday and Elementary Particle
  Experiment Seminar on Thursday
• PT Journal Club every Friday
• Weekly meeting with High Energy Experimental
  Group...

18
The Weekly Meetings
Theory
Henrys picture goes here
Experiment
19
Whats left to do?

• Took General Exam last month
• Put out LHC paper in next few days
• Finish other paper with collaborator in Rochester
  (soon? two months?)
• Go to Europe in April for 3 weeks to give a talk
  at the LHC and do a workshop in France
• Study, write up thesis, look at post-docs
• Graduate in May, 2006

20
A Humble Outline

• Road to Glory 2001-2005
• Current project Measuring Vtb at the LHC
• A Day in the Life of
• Sagely Advice

21
Sagely advice

• Check out peoples research go to Spires and
  type find author lubatti, h (goes back all they
  way to 1974!)
• Ask other graduate students (mentors, esp!) to
  introduce you to graduate students, professors
  working in different groups
• Take the time to find the right professor to
  work with

22
And thats it...

• Apologies for how All About Me this
  presentation was, but hopefully it gave some
  picture of what life is like as a phenomenologist