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Beyond the Standard Model
Oleg Ruchayskiy Relativity & cosmology-II 1
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Summary of the course
Successful application of the particle physics and gravity to theUniverse as a whole
X Laws of gravitation over the whole Universe ⇒ expansion of theUniverse. Hubble law
X Laws of thermodynamics. ⇒ Hot Big Bang theory.
X Atomic physics. Thomson scattering ⇒ properties of cosmicmicrowave background radiation
X Nuclear physics. Nuclear cross-section. Binding energy ⇒Primordial synthesis of elements. Helium abundance
X Particle physics. Weak interactions (Fermi theory) ⇒ decouplingof neutrinos (primordial element abundance)
X Particle physics of the curved space time ⇒ inflationary theory.Generation of primordial perturbations
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Did we succeed?
Oleg Ruchayskiy Relativity & cosmology-II 3
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CMB anisotropy map
CMB temperature is anisotropic over the sky with δT/TCMB ∼ 10−5
WMAP-5 results with subtracted galactic contribution (courtesy of WMAP Science team)
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CMB anisotropies (cont.)
• The temperature anisotropy δT (n̂) is expanded in sphericalharmonics Ylm(n̂):
δT (~n) =∑l,m
almYlm(n̂)
• alm’s are Gaussian random variables (before sky cut)
• CMB anisotropy (TT) power-spectrum: 2-point correlation function
〈δT (n̂) δT (n̂′)〉 =∞∑l=0
2l + 1
4πClPl(n̂ · n̂′)
Pl(n̂ · n̂′) – Legendre polynomials
• Multipoles Cl’s
Cl =1
2l + 1
l∑m=−l
|alm|2
probe correlations of angular scale θ ∼ π/l
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WMAP + small scale experiments
The WMAP 5-year TT power spectrum along with recent results from the ACBAR(Reichardt et al. 2008, purple), Boomerang (Jones et al. 2006, green), and CBI(Readhead et al. 2004, red) experiments. The red curve is the best-fit ΛCDMmodel to the WMAP data.
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Is this a success?
– Starting from ` ∼ 100 or so we do not even see error bars on the data points– Yet the model successfully predicts all the wiggles
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Is this a success?
Oleg Ruchayskiy Relativity & cosmology-II 8
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Is this a complete success?
• We understand only about 5% of the total composition of theUniverse
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Beyond the Standard Model problems
• Why is our universe devoid of anti-matter? What violatedsymmetry between particles and anti-particles in the earlyUniverse?
• Why neutrinos oscillate – disappear and then re-appear in adifferent form? What makes them massive?
• What is Dark Matter that accounts for some 86% of the total matterdensity in the Universe and have driven the formation of structurein the early Universe?
• What drives inflation?
• Why cosmological constant is almost zero?
BSM problems
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New dark matter particle?
• To create a dark matter particle is easy:
– assume heavy neutral particle, no interacting with the StandardModel.
– Assume its coupling to something in the very early Universe– Produce something that serves as cold dark matter but does not
have any observable signatures!
• Not a physical model – makes no predictions
• A model for baryon asymmetry of the Universe:
– Assume a lepto-quark (particle X that decays X → q̄ + ¯̀ andX → q + q′
– Assume that X freezes out non-relativistic (a la WIMP) and thendecays
– Assume CP-violation in the processes X → qq and X → q̄q̄
• Good baryogenesis scenario (all numbers may be made to work),but again not testable
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What we want?
A model that would allow to solve not one butseveral problems with few assumptions
(“Okkam’s razor”).
Testable predictions
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Status of particle physics
• Accelerator searches had confirmed Standard Model again andagain. Different experiments had verified each others findings
• All predicted particles have been found
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No new physics (Exotics)
× Proton decay: τp→π0+e+ > 8.2× 1033 yearsbaryon number violation
× New weakly interacting massive particles
× Axion searches
× Millicharges
× Paraphotons
5/12/2014 - Latest Results in Dark Matter Searches - Jodi Cooley
“Hints” for Low-Mass WIMPs
3
“Hints” for low-mass WIMPs in direct detection experiments
Low-mass Region
!3
LUX
CDMS II Si
CDMSlite
XENON10 S2
EDELWEISS (LT)CDMS II Ge
CRESST II
DAMA/LIBRACDMS II Ge
CoGeNT
What can we say about low-mass dark matter “hints”?
CDMS%II%Si:%Phys.Rev.Le2.%111%(2013)%251301%CDMSlite:%Phys.Rev.Le2.%112%(2014)%041302%
2%
CDMS II Si: PRL 111 (2013) 251301!CDMSlite: PRL 112 (2014) 041302
SN1987a
SN Γ-burst
EBL
X-
Rays
Telescopes
xion
HB
Helioscopes HCASTLSolar Ν
KSVZ
axio
n
LSW
Hal
osc
opes
ALPS-II, REAPR IAXO
ADMX-HF
ADMX
YMCETransparency hint
WD cooling hint
axion CDM
ALP CDM
-12 -10 -8 -6 -4 -2 0 2 4 6-18
-16
-14
-12
-10
-8
-6
Log Mass @eVD
Log
Coupli
ng@G
eV-
1D
× Neutron electric dipole momentCP violation in strong interactions
× Neutrinoless double beta decayLepton number violation
× No µ→ e+ γ or µ+ → e+e−e+
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Cosmic rays
• Historically cosmic rays werethe first accelerators (positron,muons, . . . )
• Today we detect photons, electrons/positrons, protons/antiprotons,nuclei (iron), neutrinos up to very high energies
• Everything is consistent with our knowledge of astrophysics andparticle physics
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Neutrino physics
– Natural: The Sun; The Earth’s atmosphere; Supernovae within ourgalaxy; The Earth’s crust; Cosmic accelerators
– Man made: Nuclear power plants; Neutrino superbeams andfactories
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Neutrino oscillation experiments
• 40 years ago: neutrino werethought strictly massless andflavour lepton number wasconserved (no µ → e + γ, noτ → eee, etc.)
• Today: neutrino oscillationsconfirmed by many independentexperiments (both appearance anddisappearance data)
Neutrinodetection atSNO
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Neutrino oscillations
• Consider the simplest case: two flavours, two mass eigen-states.Matrix U is parametrized by one mixing angle θ
|νe 〉 = cos θ |1〉+ sin θ|2〉|νµ〉 = cos θ|2〉 − sin θ|1〉
• Let take the initial state to be νe (created via some weak process) at timet = 0:
|ψ0〉 = |νe〉 = cos θ |1〉+ sin θ |2〉
• Then at time t > 0
|ψt〉 = e−iE1t cos θ |1〉+ sin θ |2〉 e−iE2t
• We detect the particle later via another weak process(e.g. ν? + n→ p+ µ−/e−)
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Neutrino oscillations
• The probability of conversion νe → νµ is given by
P (νe → νµ) = |〈νµ|ψt〉|2 = sin2(2θ) sin2
((E2 − E1)t
2
)
• The probability to detect νe is give by
P (νe → νe) = |〈νe|ψt〉|2 = cos2(2θ) sin2
((E2 − E1)t
2
)
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Fermion number conservation?
• Apparent violation of flavour lepton number for neutrinos can beexplained by the presene of the non-zero neutrino mass
L =
ν̄eν̄µν̄τ
[i/∂ − VFermi
]︸ ︷︷ ︸
conserves flavour number
νeνµντ
+
ν̄eν̄µν̄τ
m11 m12 . . .m21 m22 . . .. . . . . . . . .
νeνµντ
• In this case only one fermion current (total lepton fermion number)is conserved:
Jµ =∑
i=e,µ,τ
ν̄iγµνi (1)
while any independent Jµi = ν̄iγµνi is not conserved.
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Neutrino oscillations
• The prediction is: neutrinos oscillate, i.e. probability to observe agiven flavour changes with the distances travelled:
Pα→β = sin2(2θ) sin2
(1.267
∆m2L
E
GeV
eV2 km
)(2)
Mass difference: ∆m2, Neutrinoenergy: E (keV-MeV in stars, GeV inair showers, etc. Distance traveled: L
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Neutrino oscillations
• Eq. (2) predicts that probability oscillates as a function of the ratioE/L. This is indeed observed:
in this plot the distance between reactor and detector is fixed and the energy ofneutrinos is different, therefore E/L is different
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Reactor neutrino anomalies?
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Three neutrino oscillation global fit
• Data from different experiments are consistent and allow to providea global fit to the neutrino oscillations parameters
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All anomalies together cannot be true!
All data would be consistent if red contours were to the left of both green and blue contours
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Beyond the Standard Model physicsExample
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Neutrino oscillations
�
WEAK SYMMETRY
FORBIDDEN
• Number of leptons is conserved in eachgeneration
• i.e. we know with high precision thatmuons µ cannot convert into electronse.
• By virtue of the electroweak symmetryneutrinos do not change their types (i.e.νe �����XXXXX←→ νµ)
• To break symmetry between electronand neutrino we need Higgs boson
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Mass term and Higgs
Higgs condensate
Left Right
• Higgs boson (spin-0 particle) couples left to rightchiralities of fermion
• In the absence of mass term left and rightcomponents are independent
• Gauge transformations should rotate left and rightby the same phase (otherwise mass term won’t begauge invariant)
ψ̄(iγµ∂µ − ���HHHm)ψ =
(ψ∗Rψ∗L
)(����*0−m i(∂t + ~σ · ~∇)
i(∂t − ~σ · ~∇) ����*
0−m
)(ψLψR
)= 0
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Oscillations ⇒ new particles!
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Oscillations ⇒ new particles!
Right components of neutrinos?!
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Neutrino Minimal Standard Model
• New particles (N1, N2, N3) carry no charges with respect to knowninteractions
that is why they are often called sterile neutrinos
• They have different mass from left neutrinos
that is why they are sometimes called heavy neutral leptons
• They are heavier than ordinary neutrinos but interact much weaker
Right N Left νµπ±
µ∓
〈Higgs condensate〉
µDs
N
ϑµνµ
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Neutrino Minimal Standard Model
Sterile neutrinos behave as superweakly interacting massiveneutrinos with a smaller Fermi constant ϑ×GF
• This mixing strength or mixing angle is
ϑ2e,µ,τ ≡
|MDirac|2M2
Majorana=Mactive
Msterile≈ 5× 10−11
(1 GeVMsterile
)
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So what?
Massive neutral particle
Interacting weaker than neutrino
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Baryogenesis with sterile neutrinos
Sterile neutrinos may provide all conditions necessary for successfulbaryogenesis:
• Their “weaker-than-weak” interaction (ϑGF ) means that they go outof equilibrium much earlier than even neutrinos
• Their mass matrix may contain additional CP-violating phases (a laCP violating phases of CKM matrix)
• Their Majorana masses violate lepton number
This class of scenarios is calledLEPTOGENESIS
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Sterile neutrino dark matter
• Sterile neutrino is a new neutral particle, interacting weaker-than-neutrino
• Never was in thermal equilibrium in the early Universe ⇒Dodelson &Widrow’93;Dolgov &Hansen’00
⇒ Its abundance slowly builds up but never reaches theequilibrium value
⇒ avoids Tremaine-Gunn-like bound
q q′
e∓W±
Nsν̄ ν ν̄
Z0
Ns
e+e−
1 MeV100 MeVT
0
135 Ζ(3)���������������������4 Π4 g*
n�����s
WDM Ρc�M1������������������������
s0
Hot thermal relic
’Diluted’ relic
non-thermal
production
• Once every ∼ 108 div 1010 scatterings a sterile neutrino is createdinstead of the active one
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Sterile neutrino dark matter
• Very hard/impossible to search at LHC
• Very hard/impossible to search in laboratory experiments
• Can be decaying with the lifetime exceeding the age of theUniverse
• Can we detect such a rare decay?
• Yes! if you multiply the probability of decay by a large number– amount of DM particles in a galaxy (typical amount ∼ 1070–10100
particles)
νNs
e± ν
W∓
γW∓
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Okkam’s razor
One assumption about physics behind neutrino oscillations(existence of new particles N1, N2, N3) may also explain theexistence of dark matter and matter-antimatter asymmetry of theUniverse
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Particles of the νMSMM. Shaposhnikovand manyothers
10−6
10−2
102
106
1010
10−6
10−2
102
106
1010tc
u
bs
d
τµ
ννν
N
NN
N
N
e 1
1
3
3
1
2
3
Majorana massesmassesDirac
quarks leptons
2N
eV
ν
ν
ν
2
+osc
BAU
DM
Masses of sterile neutrinos as those of other leptonsYukawas as those of electron or smaller
Neutrino Minimal Standard Model == νMSM
νMSM predicts that this picture holds up to the “Planck scaleenergies” (when Compton wavelength ∼ Schwarzschild radius of particle)
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How to test this model?
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Decaying dark matter signal
• Can be decaying with the lifetime exceeding the age of theUniverse
• Can we detect such a rare decay?
• Yes! if you multiply the probability of decay by a large number– amount of DM particles in a galaxy (typical amount ∼ 1070–10100
particles)
νNs
e± ν
W∓
γW∓
• Two-body decay into two massless particles (DM → γ + γ or DM →γ + ν) ⇒ narrow decay line
Eγ =1
2mDMc
2
• The width of the decay line is determined by Doppler broadening
Oleg Ruchayskiy Relativity & cosmology-II 40
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Detection of An Unidentified EmissionLine
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Detection of An Unidentified Emission Line
[1402.2301]
We detect a weak unidentified emission line at E=(3.55-3.57)+/-0.03 keV in a stacked XMM spectrum
of 73 galaxy clusters spanning a redshift range 0.01-0.35. MOS and PN observations independently
show the presence of the line at consistent energies. When the full sample is divided into three
subsamples (Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is significantly detected
in all three independent MOS spectra and the PN ”all others” spectrum. It is also detected in the
Chandra spectra of Perseus with the flux consistent with XMM (though it is not seen in Virgo). . .
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Detection of An Unidentified Emission Line
[1402.4119]
We identify a weak line at E ∼ 3.5 keV in X-ray spectra of the Andromeda galaxy and the Perseus
galaxy cluster – two dark matter-dominated objects, for which there exist deep exposures with the
XMM-Newton X-ray observatory. Such a line was not previously known to be present in the spectra
of galaxies or galaxy clusters. Although the line is weak, it has a clear tendency to become stronger
towards the centers of the objects; it is stronger for the Perseus cluster than for the Andromeda galaxy
and is absent in the spectrum of a very deep ”blank sky” dataset. . .
Oleg Ruchayskiy Relativity & cosmology-II 43
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Data
Our dataM31 galaxy XMM-Newton, center & outskirts
Perseus cluster XMM-Newton, outskirts onlyBlank sky XMM-Newton
Bulbul et al. 201473 clusters XMM-Newton, central regions
of clusters only. Up to z = 0.35,including Coma, Perseus
Perseus cluster Chandra, center onlyVirgo cluster Chandra, center only
Position: 3.5 keV. Statistical error for line position ∼ 30 eV.Systematics (∼ 50 eV – between cameras, determination of knowninstrumental lines)
Lifetime: ∼ 1028 sec (uncertainty O(10))
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Perseus galaxy cluster
Bulbul et al. took only 2 central XMMobservation – 14′ around the cluster’scenter
We took 16 observations excluding 2central XMM observations to avoid
modeling complicated central emission
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Andromeda galaxy (zoom 3-4 keV)[1402.4119]
0.22
0.24
0.26
0.28
0.30
0.32
0.34
0.36
Normalized count rate
[cts/sec/keV]
M31 ON-center
No line at 3.5 keV
-4⋅10-3
-2⋅10-3
0⋅100
2⋅10-3
4⋅10-3
6⋅10-3
8⋅10-3
1⋅10-2
3.0 3.2 3.4 3.6 3.8 4.0
Data - model
[cts/sec/keV]
Energy [keV]
No line at 3.5 keV
Line at 3.5 keV
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Full stacked spectraBulbul et al.[1402.2301]
0.6
0.7
0.8Fl
ux (c
nts
s-1 k
eV-1
)
-0.02
-0.01
0
0.01
0.02
Res
idua
ls
3 3.2 3.4 3.6 3.8 4Energy (keV)
300
305
310
315
Eff.
Area
(cm
2 )3.57 ± 0.02 (0.03) XMM-MOS
Full Sample6 Ms
1
1.5
Flux
(cnt
s s-1
keV
-1)
-0.02
0
0.02
0.04
Res
idua
ls
3 3.2 3.4 3.6 3.8 4Energy (keV)
980
1000
1020
Eff.
Area
(cm
2 )
3.51 ± 0.03 (0.05) XMM-PN Full Sample
2 Ms
-0.002
0
0.002
0.006
0.008
Res
idua
ls
3 3.2 3.4 3.6 3.8 4Energy (keV)
290
295
300
305
310
315
Eff.
Area
(cm
2 )
XMM-MOSRest of the
Sample(69 Clusters)
4.9 Ms
• All spectra blue-shifted in thereference frame of clusters
• Instrumental backgroundprocessed similarly andsubtracted
Oleg Ruchayskiy Relativity & cosmology-II 47
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A dedicated experiment[arXiv:1310.176]
W. Bonivento, A. Boyarsky, H. Dijkstra, U. Egede, M. Ferro-Luzzi, B. Goddard, A.Golutvin, D. Gorbunov, R. Jacobsson, J. Panman, M. Patel, O. Ruchayskiy, T. Ruf,N. Serra, M. Shaposhnikov, D. Treille
��
��Proposal to Search for Heavy Neutral Leptons at the SPS
Expression of Interest. Endorsed by the CERN SPS council
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π , K
NOMAD
γProton beam
Target
νe+
e−
ν
Decay region
Rock Fe Rock
ν
ν
CHORUS
ν
Fe
VShielding
Oleg Ruchayskiy Relativity & cosmology-II 48
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A dedicated experiment
N2,3
Oleg Ruchayskiy Relativity & cosmology-II 49
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Energy & Intensity frontier
Inte
ract
ion
str
eng
th
Energy
known physics
unknown physics
LHC
Generic beam dump
facility at CERN
Energy frontier:
Weak coupling frontier:
Oleg Ruchayskiy Relativity & cosmology-II 50
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Other examples?
• Grand Unification theory (combine all gauge interactions into onebig gauge group):
Oleg Ruchayskiy Relativity & cosmology-II 51