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Searches for New Physics
Beyond the Standard Model (BSM)
• Problems of the Standard Model• Supersymmetry (SUSY)• Extra Dimensions• Further Alternatives
Standard Model Fermions
• Why 3 generations of quarks and leptons?• Why so strange hypercharges?
[Y = 2(Q − T3)]• Why flavour mixing for quarks (CKM)
and neutrinos (MNS)?• What to do with right-handed neutrinos?
(
ν′e
e
)− 12
L
(
ν′µ
µ
)− 12
L
(
ν′τ
τ
)− 12
L
e−1R µ−1R τ
−1R
(
ud′
) 16
L,r
(
cs′
) 16
L,r
(
tb′
) 16
L,r
u23R,r
d− 13R,r
c23R,r
s− 13R,r
t23R,r
b− 13R,r
(
ud′
) 16
L,g
(
cs′
) 16
L,g
(
tb′
) 16
L,g
u23R,g
d− 13R,g
c23R,g
d− 13R,g
t23R,g
d− 13R,g
(
ud′
) 16
L,b
(
cs′
) 16
L,b
(
tb′
) 16
L,b
u23R,b
d− 13R,b
c23R,b
d− 13R,b
t23R,b
d− 13R,b
Standard Model Fermions
• Why 3 generations of quarks and leptons?
• Why so strange hypercharges?[Y = 2(Q − T3)]
• Why flavour mixing for quarks (CKM)and neutrinos (MNS)?
• What to do with right-handed neutrinos?• What is the origin of fermion masses?
Why so huge fermion mass range?
Standard Model Bosons
• Does SM Higgs exist?• How can all gauge interactions be unified?
Standard Model Bosons
• Does SM Higgs exist?• How can all gauge interactions be unified?
• Why such an hierarchy of gauge fields?
EnergyTemperature
10 GeV
10 K 100 GeV
10 eV
10 K
10 K 10 GeV
Quantum Gravity Era
Present time
Neutrino transparency
EW scale
GUT scale
Quark confinement
Planck scale
Inflation
Tim
e (s
eco
nd
s)
Ele
ctr
om
ag
ne
tic
Gra
vity
Str
on
g
We
ak
32
27
15
14
19
−4
1010
1010
1010
101
1020
−40
−30
−20
−50
−10
2.7 K
Big Bang
Light transparency
Ele
ctr
ow
ea
k
Cosmological Problems
• What is dark matter?
• What is dark energy?
Attempts to Solve the Problems of the Standard Model
Many attemps going in different directions
• Extended gauge symmetries• New mechanisms of symmetry breaking
• More fundamental fields• Extra dimensions
• . . .
Radiative Corrections to Higgs Mass
• Higgs Self-energy corrections in perturbation theory: M2H = M2H,bare + ∆M
2H
Have to integrate over all particle momenta in loops⇒ Loop corrections to Higgs mass rise with UV cut-off Λ2
t
H Ht−
H HW,Z,γ
H HH
∆M2H,1 = −3
8π2g2fΛ
2
∆M2H,2 =1
16π2g2Λ2
∆M2H,3 =1
16π2λ2Λ2 V(φ) = −µ2|φ†φ| + λ|φ†φ|2
• Fine tuning to precision ∼ M2H/Λ2 is needed
For Λ = MPlanck, MH ∼ 100 GeV: (Λ/MH)2 ∼ 1034 – gauge field scale hierarchy
M2H = M2H,bare +
116π2
(−6g2t + g2+ λ2) · 1034M2H
︸ ︷︷ ︸
− . . .︸ ︷︷ ︸
≃ (130 GeV)2
SM New Physics
“Fine Tuning” Argument
• Current exp. limits on Higgs mass:114.4 < MH < 144 GeV
direct searches EW fits
• If SM is valid up to MPlanck, theor. limits:135< MH < 175 GeV
EW vacuum Triviality
EW vacuum stability: Higgs mass cannot be toolight or the potential will not have a Mexican hat
shape and will turn negative at large values
V(φ) = −µ2|φ†φ| + λ|φ†φ|2
Triviality: if the Higgs mass is too large, the Higgs
self-coupling drives the mass to infinity above cer-tain scale
Triviality and Vacuum Instability
with MH ∝ "(#2) #2
"(q)
q!q0
MH q
Upper bound: q! < !
Lower bound: q0 < ![Triviality, Landau Pole]
[Vacuum Instability]
Must be larger than scale ! at which SM breaks down}
From RGEand MH ∝ "(#2)
Higgsself coupling
depends on MH
scale[#: vacuum expectation value]
[Running self coupling]
Even if new physics appears atΛ = 10 TeV, fine tuning is significant
tree
top
gauge
Higgsm2
H
However: SM can be valid up to the Plank scale!Fine tuning is just a “stomach problem”.
Anthropic principle: properties of the universe are so specialbecause we happen to exist and be able to ask these very questions
Electron in Classical Electrodynamics
• E.m. self-energy
∆ECoulomb=1
4πǫ0
e2
rere − “size”
must be a part of the electron mass:
(mec2)observed= (mec
2)bare+ ∆ECoulomb
• From experiments: re < 10−17 cm =⇒ ∆ECoulomb& 10 GeV
0.511= −9999.489+ 10000.000 MeV
◮◮ Classical e.m. is not valid for scales where ∆ECoulomb& mec2:
d <e2
4πǫ0mec2= 2.8 · 10−13 cm
Quantum Effect – e+e− Pair Production
• Self-energy e− e−e−γ ←
←
the same diagram in QED
• Positron exists. e+e− pair production
+ee−
e−γ
Vacuum fluctuations at ∆t ∼~
∆E∼
~
2mec2(Heisenberg’s uncertainty)
modify physics at d ∼ c∆t ∼ 200· 10−13 cm
∆Epair = −1
4πǫ0
e2
re+ . . . =⇒ ∆E = ∆ECoulomb+ ∆Epair =
3α4π
mec2log
~
mecre
• Mass correction
(mec2)observed= (mec
2)bare
[
1+3α4π
log~
mecre
]
Even for re ∼ 1/MPlank ∼ 10−33 cm mass increases by 9%
◮◮ Doubling d.o.f. + symmetry =⇒ divergency cancellation
Higgs Self-Energy
t
H Ht−
∆M2H,top = −3
8π2g2tΛ
2+ . . .
Bosons and fermions produce different signs in loops =⇒
Introduce “superpartner” for top = scalar top = “stop” = t̃
H Ht~−
t~
∆M2H,stop= +3
8π2g2tΛ
2+ . . .
Total correction
∆M2H,top + ∆M2H,stop= −
38π2
g2t (m2t̃ − m
2t )log
Λ2
m2t̃
◮◮ “Naturalness” argument: mt̃ should be not much larger than mt mt̃ ∼ TeV???
Supersymmetry (SUSY)
SUSY Particles
sleptons, squarks =sfermions = bosons
. . . -inos = fermionshiggsinos, gauginos
(photino, wino, . . . )= neutralinos,
charginos
Searches for New PhysicsStandard Model FermionsStandard Model FermionsStandard Model BosonsStandard Model BosonsCosmological ProblemsAttempts to Solve the Problems of the Standard ModelRadiative Corrections to Higgs Mass``Fine Tuning'' ArgumentTriviality and Vacuum InstabilityElectron in Classical ElectrodynamicsQuantum Effect -- e+e- Pair ProductionHiggs Self-EnergySupersymmetry (SUSY)SUSY ParticlesSUSY ModelsmSUGRATypical mSUGRA SpectrumR-ParityGrand Unification Theory (GUT)SUSY Production at LHCMissing ETSimulation: SUSY Event in ATLASSUSY Signatures at the LHCDiscovery Potential -- Example mSUGRADiscovery Potential -- Adding LeptonsSUSY Particle Mass ReconstructionSUSY Particle Mass ReconstructionSUSY Particle Mass Reconstruction(Quasi-)Stable Coloured Hadrons: R-Hadrons(Quasi-)Stable Coloured Hadrons: R-HadronsForest SketchArguments for SUSYChallenges for Low Energy SUSYScenarios for SUSY at the LHCExtradim SketchCompactified Extra DimensionsLarge Extra DimensionsNew Fundamental Planck ScalePossible Sizes of Extra DimensionsMotivation by the String TheoryKaluza--Klein Gravitons in ADDMonojetsMonojets -- Standard Model BackgroundsMonojets -- Standard Model BackgroundsMonojets @ Tevatron and LHCVirtual Graviton Exchange in ADDVirtual Graviton Exchange in ADD @ LHCLarge Extra Dimensions at LEPBlack HolesBlack Hole Formation @ Hadron CollidersBlack Hole Production @ LHCBlack Hole FactoryHawking RadiationBlack Hole Event Simulation @ ATLASBlack Hole Event SelectionBlack Hole Mass ReconstructionBlack Hole Discovery PotentialDemocratic Particle DistributionBlack Holes vs. SUSYExtraction of Model ParametersFurther AlternativesAdditional InformationWino Dark MatterProton Decay -- Higher OrdersAstrophysical Limits in ADD ModelsAstrophysical Limits in ADD ModelsWarped Extra DimensionsWarped Extra DimensionsKaluza--Klein Gravitons in RSRemark on RS Model ParametersRS Gravitons: Expectations for Tevatron and LHCKK Gravitons in RS: Reconstruction @ TevatronKK Gravitons in RS @ TevatronKK Gravitons in RS: Reach @ LHCKK Gravitons in RS: Reach @ LHCBlack Hole DecayCHARYBDIS MC Event GeneratorTriggering Black HolesHiggs in Black Hole DecaysBlack Holes in Cosmic RaysCosmic Ray Bounds in ADDFuture Bounds in ADDFuture Bounds in RSBlack Holes -- The End of The WorldBlack Holes as Energy Source