Particle Physics and Cosmology (PPC) - Are they...
Transcript of Particle Physics and Cosmology (PPC) - Are they...
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Particle Physics and CosmologyParticle Physics and Cosmology(PPC)(PPC)
-- Are they related? Are they related? --
Prof. Teruki Kamonand
Prof. Bhaskar DuttaDepartment of PhysicsTexas A&M University
REU Seminar(2007)
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PPC are related!!!
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Can particle physics help us understanding the Early Universe and the Big Bang?
Today, we speak about the connection from a view point of upcoming colliderexperiment: Large Hadron Collider
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http://ppc07.physics.tamu.edu/index.html
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HEP EXPERIMENT & THEORYHEP EXPERIMENT & THEORY[Collider Physics - CDF, CMS, International Linear Collider]
T. Kamon, P. McIntyre, A. Safonov, D. Toback [Neutrino Physics - MINOS, NOνA]
R. Webb [Dark Matter Detection - ZEPLIN, SIGN]
J. White[Phenomenology]
R. Allen, R. Arnowitt, R. Bryan, B. Dutta, D. Nanopoulos[String Theory]
K. Becker, M. Becker, D. Nanopoulos, C. Pope, E. Sezgin
ASTRONOMYASTRONOMY[Observational Astronomy]
N. Suntzeff, L. Wang, at least 2 more faculty members
Faculty Members and Research Areas
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PPC Graduate and Undergrad. Students
… and students working on accelerator physics and string theory.
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Thinking of Our Universe
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My Universe
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Cosmic Microwave Background (CMB) was emitted when the Universe was only 380,000 years old.
The Most Distant Light
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Message from the Universe
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4%
The 23% is still unobserved in the laboratory.. (This new matter can not be seen visually!)
We call this Cold Dark Matter..
Contents of the Universe
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Examples of observations:
We know the dark matter exists.
Rotation curves of the galaxies
Collision of the galaxies
Existence of Dark Matter
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3
2
1splitting normal matter and dark matter apart
– Another Clear Evidence of Dark Matter –(8/21/06)
Dark Matter(Gravitational Lensing)
Ordinary Matter(NASA’s Chandra X-ray Observatory)
Cosmic Collision of 2 Galaxy Clusters
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time
Approximately the same size asthe Milky Way
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Dark Matter Sandwich
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But we have a few clues. Let’s check what we know.
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What is Cold Dark Matter?
Can it be one of the known particles?Let’s check what we know.
It’s Doesn’t Matter.Right, it doesn’t shake hands with anyone easily. Two dark matter clusters (blue balls) are just passing each other.
It’s a Cold Matter.Yes, it is a “relativistically” slowly moving (“cold”) object.
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It’s a Charge-less Matter.Right, it doesn’t respond to your flash light. This means it is a neutral object.
So, It’s a Cold Dark Matter.Right, it is a neutral and long-lived (stable) object.
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Thinking of Elementary Particles
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Known Matter Particles
How many?
On
ion
Str
uct
ure
o
f M
atte
r
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12 Particle-Zoo Animals
All masses in MeV.ANIMAL MASSES SCALE WITH PARTICLE MASSES
6 Types o
f Lept
ons
6 Types of
Quarks
The 12 elementary particles are fundamental building blocks of matter.
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4 Zoo Keepers
NOTE : Graviton (G) ( not found) carries gravitational force.
g’s (gluons) strong forceQuarks experience them. Protons & neutrons are stick together.
γ’s (photons) electromagnetic forceQuarks, leptons (other than neutrinos) experience this force.
W’s (weak bosons) for weak forces Quarks, leptons experience this force.
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Heavy
Light
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Heavy
Light
Same force for all generationsAll reactions are explained by a single description (= theory).
Picture of Interactiond W + uW e ν
t W + bW e ν
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W W
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[100 points] The Standard Model describes all these particles and 3 of 4 forces by paring two elementary particles. We have confirmed the existence of those in the laboratory experiments. Choose a candidate for the Dark Matter particle. Explain why.
CDM in The Standard Model?
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We need a new model.
No!Quarks, electron, muon, tau particles, and force carriers can not be the dark matter, since their interactions are stronger than what we expect.
Neutrinos can, but they have other problems.
X X XX X X
X X XX X X
XXXX
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We need an idea, based on a new symmetry.Supersymmetry or SUSY
Supersymmetrizing the Standard ModelNeutral-ino
This new charge-less (neutral) particle is the leading candidate for the dark matter.
New Idea
1) What is the new model? 2) Attractive?3) Can the neutralino be detected and consistent
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Mirror Reflection
Ferm
ilab
Bo
sela
b
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Supersymmetric Reflectionγ
νe νµ ντ
e µ τ
But, one of them is neutralino. This is the lightest SUSY particle and stable.
Lots of new particles!!!!
Renamed as
“chi-o
ne zero
”
01χ~
02χ~
Renamed as
“chi-tw
o zero
,”
heavier than
chi-one ze
ro.
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Heavy
Light
SUSY decays can be described in the same way as the Standard Model.
Picture of Interaction (Again)t W + bW e ν
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01χ~
~~Heavy
Light
The SUSY nature will be preserved through the entire decay chain. We graphically show this by yellow lines from the beginning to the ending.
tSUSY WSUSY + b
WSUSY χSUSY + e ν
WW
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YES. Physicists always dream about unification of all the forces.
Attractive?
We can construct a SUSY model with a stable neutralino to have the grand unification of the forces.
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SUSY is an interesting class of models to provide a massive neutral particle (M ~ 100 GeV) and weakly interacting (WIMP).
SU
SY
SU
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CDM = Neutralino ( )CDM = Neutralino ( )01χ~
Ast
rop
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Ast
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~0.0000001 seconds
When Were the Dark Matter Particles Created?
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Now
CMB~380,000 years
(You = 20 yrs old)
(You = 4.8 hrs old)
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My Universe
Thinking of Dark Matter Detection
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One promising way: In particle collisions
E = Mc2
Proton and ant-proton collision can produce the Standard Model particles like heavy top quarks (~180 times heavier than a proton!)
Physics Magic: PingPhysics Magic: Ping--pong balls pong balls Steel BallsSteel Balls
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Tevatron Large Hadron Collider Linear Collider
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Large Large HadronHadron ColliderCollider (LHC)(LHC)
Two large international collaborations.
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7 times powerful than the Tevatron
ATLAS
CMS
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““UndergroundUnderground”” ExperimentsExperiments
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ATLAS
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CMS(*)
(*) The TAMU group is a member of the CMS collaboration.
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CMS CMS -- Particle DetectorParticle Detector
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Compact is a Relative
Term
CMS is significantly smaller than
ATLAS but heavier
Anatomy of CMSAnatomy of CMS
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Collision as We Imagine Collision as We Imagine ……
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We study blue and red dots and yellow lines to figure out what happens in the collision!
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Reconstruction as We Imagine Reconstruction as We Imagine ……
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We have to extract this reaction out of many trillion pp collisions.
Key Reaction at the LHCKey Reaction at the LHC
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LSOS
OS−LS
Mpeak = 47.1 GeV
Mmax(true) = 78.7 GeV
OS−LS counts with Mττ < 100 GeV:Top : 6 countsW+jets : 1 countSUSY : 125 counts
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Anatomy Anatomy –– Mass DistributionMass Distribution
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OS
LS
OS−LS
Probing squark mass
Anatomy Anatomy –– Mass Distribution (2)Mass Distribution (2)
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GOAL: Establish the technique before the experiment starts in 2008.
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We measure the masses (M) of the
particles at the LHC.
How do you know that the neutralinos (we will observe) at the collider are responsible for the dark matter content?
We calculate the dark matter content (Ω)in the new model of
the Universe.
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Ωχ
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χ~
τ~
χ~
g~
M
M
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M We establish the dark allowed regions from the detailed features of the signals, and accurately measure the masses.
We calculate the relic density and compare with WMAP.
Work in progress
Example TranslationExample Translation
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SUSYModel
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With R. Arnowitt, B. Dutta, T. Kamon, D. Toback
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So far in the laboratories we have seen theparticles responsible for 4% of the universe.
The upcoming experiments (e.g., LHC) will tryto probe the nature of 23 % of the universe:dark matter.
Challenge:
73% of the universe is still a major puzzle.Not yet understood theoretically!
Conclusion
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