Dheeraj Kumar Singh

2. Beauty in the Universe

3. Innermost Space
High Energy Particle
Physics is a study of the
smallest pieces of matter.
It investigates the deepest
and most fundamental
aspects of nature.
It investigates (among other
things) the nature of the
universe immediately after
the Big Bang.
It also explores physics at
temperatures not common
for the past 15 billion years
(or so).

4. Helium Neon
Periodic Table
All atoms are made
of protons, neutrons
and electrons
u u u
d
d d
Proton Neutron Electron
Gluons hold quarks together
Photons hold atoms together

5. u
d
While quarks have
b t
similar electric charge,
they have vastly s
different masses (but
c
zero size!)

7. e
rs
ve
ni
U
Why three dimensions?
m
n tu
What gives particles their
ua
Q mass?
he
Are there new forces and
t
symmetries that we don’t yet know?
of
s
rie
Are the forces and particles of which we do
te
know just different faces of a deeper,
ys
unifying principle?
M

8. α=e2/ħc

9. Fermi National Accelerator
Laboratory
(a.k.a. Fermilab)
• Begun in 1968
• First beam 1972
(200, then 400
GeV)
• Upgrade 1983
Jargon alert: 1 Giga Electron Volt
(GeV) is 100,000 times more energy (900 GeV)
than the particle beam in your TV. • Upgrade 2001
If you made a beam the hard way,
(980 GeV)
it would take 1,000,000,000 batteries

11. → The Main Injector upgrade was completed in 1999.
→ The new accelerator increases the number of
possible collisions per second by 10-20.
→ DØ and CDF have undertaken massive
Expected upgrades to utilize the increased
Number Huge statistics
of for precision physics collision rate.
Events at low mass scales
1000 → Run II began March 2001
Formerly rare processes
become high statistics
100 processes
10 Run II Increased reach
for discovery physics
at highest masses
1
Run I
Increasing ‘Violence’
of Collision

12. How Do You Detect Collisions?
• Use one of two large multi-purpose
particle detectors at Fermilab (DØ and
CDF).
• They’re designed to record collisions of
protons colliding with antiprotons at
nearly the speed of light.
• They’re basically cameras.
• They let us look back in
time.

13. Typical Detector
• Weighs 5,000 tons
(Now) • Can inspect
10,000,000
collisions/second
• Will record 50
collisions/second
• Records
30’ approximately
10,000,000 bytes/
second
• Will record 1015
(1,000,000,000,000,000)
30 bytes in the next
’ 50’ run (1 PetaByte).

14. Remarkable Photos
In this collision, a top and
anti-top quark were created,
helping establish their existence
This collision is the most violent
ever recorded (and fully
understood). It required that
particles hit within 10-19 m or
1/10,000 the size of a proton

16. Modern Cosmology
• Approximately 15 billion years
ago, all of the matter in the
universe was concentrated at
a single point
• A cataclysmic explosion (of
biblical proportions perhaps?)
called the Big Bang caused
the matter to fly apart.
• In the intervening years, the universe has been
expanding, cooling as it goes.

17. Now
(13.7 billion years)
Stars form
(1 billion years)
Atoms form
(380,000 years)
Nuclei form
(180 seconds)
Nucleons form
(10-10 seconds)
4x10-12
Quarks differentiate seconds
(10-34 seconds?)
??? (Before that)

18. e
rs
ve
ni
U
Why three dimensions?
m
n tu
What gives particles their
ua
Q mass?
he
Are there new forces and
Back to the
t
symmetries that we don’t yet know?
of
Mysteries
s
rie
Are the forces and particles of which we do
te
know just different faces of a deeper,
ys
unifying principle?
M

19. In 1964, Peter Higgs postulated a physics
mechanism which gives all particles their mass.
This mechanism is a field which permeates the
universe.
If this postulate is correct, then one of the
signatures is a particle (called the Higgs Particle).
Fermilab’s Leon Lederman co-authored a book
on the subject called The God Particle.
bottom
top
Undiscovered!

20. Higgs: An
Analogy

21. Hunting for Higgs
For technical reasons, we look for Higgs
bosons in association with a W or Z boson.
b jet In the region where the
Higgs boson is
expected, we expect it
electron to decay nearly-
exclusively into b-
quarks
neutrino
(MET)
H → bb

22. Symmetries
Translational
Rotational

23. More Complex Symmetries
In a uniform gravitational field,
a ball’s motion is independent
of vertical translation.
The origin from where
potential energy is chosen is
∆h irrelevant.
1 2
mv = mg∆h
2
The equations of motion are
“symmetric under vertical or
horizontal translations.” v = 2 g∆h

24. Complex Familiar Symmetries
y
r
r2
r1
x
1 q1q12 2qq
V=
4πε o | r1 − r2 |
r

25. Complex Familiar Symmetries
y
Translations: r
x → x + ∆x
y → y + ∆y r2
r1
r2 x
r1
1 q1q2
V=
4πε o | r1 − r2 |

26. Complex Familiar Symmetries
y
Reflections: r
x → -x
y → -y r2
x r1
x
1 q1q2
V=
4πε o | r1 − r2 |
y

27. Complex Familiar Symmetries
y
Rotations: r
φ → −φ
r2
r1
x
1 q1q2
V=
4πε o | r1 − r2 |

28. Complex Familiar Symmetries
y
Charge Flip: r
q→−q
r2
r1
x
1 q1q2 1 (−q1 )(− q2 )
V= = =V
4πε o | r1 − r2 | 4πε o | r1 − r2 |

29. Complex Familiar Symmetries
y
r
Bottom Line:
Electromagnetic force r2
exhibits a symmetry
under:
r1
Translation
Rotation
Reflection x
Charge Congugation
1 q1q 1 (−q1 )(− q2 )
V=
(and many others) 2 = =V
4πε o | r1 − r2 | 4πε o | r1 − r2 |

30. Fermions and Bosons
Fermions:
matter particles
½ integer spin
Bosons:
force particles
integer spin

31. Unfamiliar Symmetries
One possible symmetry that is not yet observed is the
interchange of fermions (spin ½ particles) and bosons
(integral spin particles)
Known equation
Equation = Fermions + Bosons
Interchanged equation (pink ⇔ green)
Equation = Fermions + Bosons

32. Unfamiliar Symmetries
One possible symmetry that is not yet observed is the
interchange of fermions (spin ½ particles) and bosons
(integral spin particles) Fermions + Bosons
+
Known equation
Equation = Fermions + Bosons
Interchanged equation (pink ⇔ green)
+ Fermions + Bosons
This New=Symmetry+is called
Equation Fermions Bosons
SuperSymmetry (SUSY)

33. SUSY Consequence
• SUSY quark “squark”
• SUSY lepton “slepton”
• SUSY boson “bosino”

34. The Golden Tri-lepton
SuperSymmetry Signature
muons
This is the easiest to
observe signature for
SUSY. electron
No excess yet observed.
neutrino

35. The Conundrum of Gravity
• Why is gravity so much weaker
(~10-35×) the other forces?
– Completely unknown
• One possibility is that gravity can
access more dimensions than the other
forces

36. The Dimensionality of Space Affects
a Force’s Strength
Qencl  
• Gauss Law = ∫ E ⋅ dA
εo
1 Qencl 1 Qencl
E= E=
2πε o r 4πε o r 2
2D
3D

37. Are More Dimensions Tenable?
• Newton’s Law of Gravity
Gm1m2
F= 2
r
• Clearly indicates a 3D space structure.
Or does it?

38. Nature of Higher Dimensions
• What if the additional dimensions had a
different shape?
• What if the additional dimensions were
small?

39. Access to Additional Dimensions
• What if gravity alone had access to the
additional dimensions?

40. Access to Additional Dimensions
• What if gravity alone had access to the
additional dimensions?

41. A Model with “n” Dimensions.
• Gravity communicating with
these extra dimensions could
produce an unexpectedly
large number of electron or
photon pairs.
• Thus, analysis of the
production rate of electrons
and photon provides
sensitivity to these extra
dimensions.
• Large energies are required
to produce such pairs.
p e
q
q’ G
p e

42. Once again there are
interesting events!
(way out on the mass tail.)
ee pair γγ pair
electrons
photons

43. Data-Model Comparison

44. Data-Model Comparison

45. Summary
• Particle physics allows us to study some
of the deepest mysteries of reality.
• We know a whole bunch of stuff.
Send students.
• The things we don’t know, we’re studying
like mad.
• The mysteries mentioned here are
unsolved. We need help.

46. www-d0.fnal.gov/~lucifer/PowerPoint/Teacher_Colloquium.ppt

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