1. « The incredible progresses of particle physics and cosmology »
Does our knowledge of the laws of microscopic physics
help us to understand the universe at large?
P. Binétruy
AstroParticule et Cosmologie, Paris
XII International Workshop on « Neutrino Telescopes »
Venezia, Palzzo Franchetti, 9 March 2007

2. A microscopic world almost fully explored (in as much as it is known)

3. All ingredients of the Standard
Model as we know it have been
understood and confirmed except
for the Higgs

4. All observations on quark mixing are consistent
with a single CP-violating phase 

5. Neutrinos : most of the MNSP mixing matrix is known
Atmos. neutrinos
Solar neutrinos

6. Remaining unexplained :
mass hierarchies, i.e. a theory of Yukawa couplings
Horizontal symmetries?
strong CP-violating phase i.e.  < 10-9

7. A universe at large which remains largely unexplained in the
context of the Standard Model :
dark matter
acceleration of the universe
matter-antimatter antisymmetry

8. Dark matter
Galaxy rotation curves
Lensing

9. New particles may be valuable candidates25
109 GeV xf
 h2 ~
g*1/2 MP < ann v >
Number of deg. of freedom at time of decoupling
mass ~ MEW
< ann v > ~  EW/MEW 2
  h2 ~ 1
to be compared with
dark h2 =  0.009
Weakly Interacting Massive Particles
(absent in SM)

10. Recent acceleration of the Universe
Supernovae (Sn Ia) :
Hubble plot : magnitude vs redshift
astro-ph/

11. Matter-antimatter asymmetry
No working astrophysical model
From the point of view of fundamental physics, 3 necessary
ingredients (Sakharov) :
CP violation 
B violation 
out of equilibrium  first order phase transition
mHiggs > 72 GeV 

12. Will the theories of the microscopic world allow us to understand
better the Universe at large?

13. NO : the vacuum energy (cosmological constant) problem
Classically, the vacuum energy is not measurable. Only differences
of energy are (e.g. Casimir effect).
Einstein equations: R - R g/2 = 8G T
geometry
energy
Hence geometry may provide a way to
measure absolute energies e.g. vacuum
energy:

14. R - R g/2 = 8G T +  g 
 ~ 0.7 ~ 1  -1/2 ~ H0 -1 =10 26 m
size of the presently visible universe
A very natural value for an astrophysicist !
A high energy theorist would compute the vacuum energy and find
-1/2 ~ MW -1 ~ m electroweak scale
or -1/2 ~ mP-1 ~ m Planck scale
Related questions : why now? why is our Universe so large, so old?

15. Will the theories of the microscopic world allow us to understand
better the Universe at large?
YES : the example of dark matter

16. Connecting the naturalness of the electroweak scale with the
existence of WIMPs
naturalness
3mt2
22v2
6MW2 + 3MZ2
8 2v2
3mh2
8 2v2
mh2 = t g h2
v = 250 GeV
Naturalness condition :
|mh2 | < mh2
Introduce new physics at t (supersymmetry, extra dimensions,…) or raise mh to 400 GeV range

17. stable particles in the MEW mass range
New local symmetry
Standard Model
fermions
New
fields

18. stable particles in the MEW mass range
New local symmetry
Lightest odd-parity
particle is stable
New discrete symmetry
Standard Model
fermions
New
fields

19. Example : low energy SUSY
R symmetry
Stable LSP
R parity
Standard Model
fermions
Supersymmetric
partners

20. Bullet proof Ordinary matter Dark matter X-rays (Chandra)
Clowe, Randall, Markevitch
Bullet proof
astro-ph/
Dark matter
Gravitational lensing
Ordinary matter
X-rays (Chandra)

22. Going beyond : what might the infinitely small tell us in the
future about the infinitely large?
discovery of scalar particles
discovery of WIMPs
(discovery of extra dimensions)

23. Fundamental scalar fields
The discovery of the Higgs would provide
the first fundamental scalar particle.
Scalars are the best remedy to cure cosmological problems:
Inflation, dark energy, compactification radius stabilization…
Scalars tend to resist gravitational clustering and thus may provide a diffuse background
Speed of sound cs2 = p/ ~ c2

24. Can we hope to test the dark energy idea at colliders?
Most popular models based on scalar fields (quintessence) :
 has to be very light :
m  ~ H0 ~ eV V 
exchange would provide a long range force :
 has to be extremely weakly coupled to matter
HOPELESS FOR COLLIDERS

25. Dark matter: search of WIMPs at LHC
missing energy signal
Produced in pair : difficult to reconstruct,
in the absence of a specific model

26. search through direct detection
e.g. minimal sugra model

27. Going beyond : what might the infinitely large tell us in the future
about the infinitely small?
cosmological data and neutrino masses
gravitational waves and the electroweak phase transition
high energy cosmic rays and extra dimensions

28. Testing the scale of (lepton) flavour violations
Cosmology
 =m /(92.5eV)
Baryon asymmetry
Neutrino masses
m = MEW2 / MF
Flavor physics
MF ~ GeV ?
Flavour violations
Colliders

29. baryonh2 darkh2  in dark  mi Data ∑mi (95%CL) N 1.8 eV - 1.3 eV
astro-ph/
baryonh2
darkh2
fraction of
 in dark
matter
WMAP 3 yr: astro-ph/
 mi
Data
∑mi
(95%CL) N
WMAP
1.8 eV -
WMAP+SDSS
1.3 eV
WMAP+2dFGRS
0.88 eV
2.7  1.4
CMB+LSS+SN
0.66 eV
3.3  1.7
SDSS
WMAP

30. Electroweak phase transition and gravitational waves
If the transition is first order,
nucleation of true vacuum bubbles
inside the false vacuum
Collision of bubbles  production of gravitational waves

31. Pros and cons for a 1st order phase transition at the Terascale:
in the Standard Model, requires mh < 72 GeV (ruled out)
MSSM requires too light a stop but generic in NMSSM
possible to recover a strong 1st order transition by including H6 terms
in SM potential
other symmetries than SU(2)xU(1) at the Terascale ( baryogenesis)

32. Gravitons of frequency f produced at temperature T are observed .
Gravitons of frequency f produced at temperature T are observed
at a redshifted frequency
1/6
f = Hz ( ) ( ---- ) 1 T g 
1GeV
100
At production  =  H-1
Wavelength
Horizon length
g is the number of degrees of freedom

33. Gravitational wave detection
LF band 0.1 mHz - 1 Hz
Gravitational wave amplitude
VIRGO

34. LF band 0.1 mHz - 1 Hz
Gravitational wave amplitude
VIRGO
T in GeV
10 3
10 6
10 9

35. Electroweak breaking scale
LF band 0.1 mHz - 1 Hz
VIRGO
T in GeV
10 3
10 6
10 9

36. LISA
launch > 2015
ESA/NASA mission
Three satellites forming a triangle of 5 million km sides

39. High energy cosmic rays and extra dimensions
Black holes
Extra dimensions

40. More than 3 dimensions to our space?
Why ask?
Unification of gravity with the other interactions seems to require it :
unification electromagnetism-gravity (Kaluza 1921-Klein 1926)
unification of string theory (>1970)
For a theory in D=4+n dimensions with n dimensions compactified
on a circle of radius R :
mPl2 = MD2+n Rn
MD fundamental scale of gravity in D dimensions

41. ( ) If MD ~ 1 TeV, possible to produce black holes
matter
If MD ~ 1 TeV, possible to produce black holes
gravity
gauge inter.
Relevant scale for a black hole of mass MH is Schwarzschild radius:
1/1+n 1
MBH
rS ~ ( ) MD MD
Thorne: a black hole forms in a 2-particle collision if the impact parameter
is smaller than rS.
 ~  rS2

42. ( ) Hawking evaporation of the BH caracterized by the temperature n+1
4 rS
3+n/1+n
MBH 1 ( )
dE / dt  TH4+n gives
BH ~ MD MD
BH decays visibly to SM particles:
large multiplicity N ~ MBH / (2TH)
large total transverse energy
characterisitic ratio of hadronic to leptonic activity of 5:1

43. Search for BH formation in high energy cosmic ray events
Look for BH production by neutrinos in order to overcome the QCD background:
 horizontal showers

44.  ( N  BH) for n=1 to 7 and MD = 1 TeV
 N  BH  MD-2(2+n)/(1+n)
n=1
SM ( N  l X)
Anchordoqui, Feng, Goldberg, Shapere hep-th/

45. hep-ph/

46. Includes inelasticity :
MBH ≠ s
n=6
Auger : bkgd of
2SM 
+ 10 hadronic evts
xmin = MBHmin/MD
MBHmin smallest BH mass for which we
trust the semi-classical approximation.
hep-ph/

47. Does our knowledge of the laws of microscopic physics
help us to understand the universe at large?

48. Three and a half scenarios :
The orthodox scenario : discovery of supersymmetry at LHC
Pros : light Higgs
Cons : too orthodox
This would confirm the general features of the « fundamental »
universe as we understand it : role of scalars, nature of dark matter,
string theory probable quantum theory of gravity…
The standard scenario : discovery only of the Higgs
Pros : minimal
Cons : too standard, mass hierachies not addressed
This might be the end of large colliders. Only way of doing high
energy physics might be through neutrinos and astroparticles

49. The radical scenario : discovery of large extra dimensions
Pros : new ways of breaking symmetries
Cons : why large?
Revolutionize our perspectives on the Universe. String theory
probable quantum theory of gravity. BH production may
overcome any future collider signatures.
The favourite scenario: discovery of something unexpected

50. In any case, particles will provide a new way of studying the Universe
Ideally, one would like to study the same source (*) by detecting
the gravitational waves, neutrinos, hadrons and photons emitted :
gravitational waves give information on the bulk motion of
matter in energetic processes (e.g. coalescence of black holes)
high energy photons trace populations of accelerated particules,
as well as dark matter annihilation
protons provide information on the cosmic accelerators that have
produced them
neutrinos give information on the deepest zones, opaque to
photons (e.g. on the origin --hadronic or electromagnetic-- of ).
(*) Applies also to the primordial universe!