Supersimmetria, naturalezza e selezione ambientale

1
Supersimmetria, naturalezza e selezione ambientale

• G.F. Giudice

• N. Arkani-Hamed, G.F.G., R. Rattazzi, in
  preparation
• N. Arkani-Hamed, A. Delgado, G.F.G., NPB 741, 108
  (2006)
• Delgado, G.F.G., PLB 627, 155 (2005)
• N. Arkani-Hamed, S. Dimopoulos, G.F.G., A.
  Romanino, NPB 709, 3 (2005)
• N. Arkani-Hamed, S. Dimopoulos, JHEP 0506, 073
  (2005)
• G.F.G., A. Romanino, NPB 699, 65 (2004)

2
Central problem of particle physics
?H2 very sensitive to high-energy corrections
No large tuning ? ? lt TeV
Can mH 180?220 GeV reduce the tuning? NO!
Abuse of effective theories finite (or log-div)
corrections at ? remain
Ex. in SUSY quadratic divergences cancel, but
3
(No Transcript)
4
Supersymmetry triumph of symmetry concept!

• Gauge-coupling unification
• Dark Matter
• Radiative EW breaking

5
Hierarchy a problem of criticality
Exact supersymmetry ? on critical point Small
breaking of supersymmetry ?
6
(No Transcript)
7
EW breaking computable as a function of soft terms
In natural supersymmetry MSltltQcltltMPl and
MZMS Little hierarchy only if QcMS
8

• A measure of the fine tuning
• A characterization of the tuning

9
(No Transcript)
10
DARK MATTER
Natural thermal relic with ?DMh20.127?0.010 Quant
itative difference after LEP WMAP For MSgtMZ
neutralino is almost pure state
B-ino annihilation through sleptons (too slow)
me lt 110 GeV (LEP me gt 100 GeV) H-ino, W-ino
annihilation through gauge bosons (too fast)


11

• DM is possible in special regions
• coannihilation
• Higgs resonance
• Well-tempered
• or non-thermal

Both MZ and ?DM can be reproduced by low-energy
supersymmetry, but at the price of some
tuning. Unlucky circumstances or wrong track?
12
What determines the physical laws?
The reductionists dream Unique consistent
theory defined by symmetry properties (no
deformation allowed, no free parameters)

• Monotheistic view ? God
• M-theoristic view ? 2nd string revolution

String theory ? low-energy susy ? SM
13
A different point of view
Vacuum structure of string theory 10500
vacua (N d.o.f in M config. make MN)
Expansion faster than bubble propagation
Big bang ? universe expanding like an inflating
balloon Unfolding picture of a fractal universe ?
multiverse
14
In which vacuum do we live?
Not a unique final theory with parameters
O(1) ? allowed by symmetry but a statistical
distribution
Determined by environmental selection

• Large and positive ? blows structures apart
• Large and negative ? crunches the Universe too
  soon

??
Weinberg
Is the weak scale determined by selection? Are
fermion masses determined by selection?
Will these ideas impact our approach to the final
theory?
I will show two examples relevant to
supersymmetry and LHC
15
A physicist talking about the anthropic
principle runs the same risk as a cleric talking
about pornography no matter how much you say you
are against it, some people will think you are a
little too interested S. Weinberg
In 1595 Kepler asked the question Why are there
6 planets? It seems a proper scientific
question ( Why are there 3 quark families? )
16
Mysterium Cosmographicum gives a geometrical
explanation
Planetary orbits lie within the only 5 Platonic
solids that can be both circumscribed and
inscribed within a sphere. It well matched
planetary distances known at that time.
We are confident about the anthropic explanation
because we observe a vast universe with a
multitude of stars
The ultimate Copernican revolution?
17
Assume mici MS, and MS scans Qc MPl f(ci,?a)
does not depend on MS MSgtQc ? ltHgt 0,
MSltQc ? ltHgt ? 0 Impose prior that EW is broken
(analogy with Weinberg)
Loop factor lt ln MS/Qcgt
Little hierarchy Supersymmetry visible at LHC,
but not at LEP (post-diction)
18
(No Transcript)
19
If ? and MS scan independently

• solution to ? problem
• prediction for ? and tan?

20
A more radical approach Split Supersymmetry
ABANDON NATURALNESS BUT REQUIRE

• Gauge-coupling unification
• Dark matter

21
Gauge-coupling unification as successful (or
better) than in ordinary SUSY
22
Not unique solution, however

• Minimality search for unification with single
  threshold, only fermions in real reps, and 1015
  GeV lt MGUT lt 1019 GeV ? SpS has the minimal field
  content consistent with gauge-coupling
  unification and DM
• Splitting of GUT irreps in SpS no need for new
  split reps either than SM gauge and Higgs
• Light particles R-symmetry protects fermion
  masses
• Existence and stability of DM R-parity makes c
  stable
• Instability of coloured particles coloured
  particles are necessary, but they decay either by
  mixing with quarks (FCNC!) or by interactions
  with scale lt 1013 GeV
• SpS not unique, but it has all the necessary
  features built in

23
Why Supersymmetry?
24
Split Supersymmetry determined by susy-breaking
pattern
25
Unavoidable R-breaking from CC cancellation
Potentially larger effect from anomaly med.
Eq. motion for conformal compensator
In theories where susy breaking is tied to
gravity and supersymmetry is restored in the flat
limit, Ff ? 0
26

• Higgs mass
• Gluino lifetime
• Gaugino couplings
• Electric dipole moments
• Dark Matter

How to test Split Supersymmetry
HIGGS MASS
27
ELECTRIC DIPOLE MOMENTS
Exp delt2 10-27 ecm dnlt6 10-26 ecm
Yale de 10-29 10-31 Sussex de 10-30 Los
Alamos de dn 10-31 10-35 BNL d? 10-24
28
GAUGINO COUPLINGS
29
GLUINO LIFETIME
Age of the universe
Gamma rays
Nucleosynthesis
Decays outside detector
Gluino hadronizes

• Charged R-hadrons. Time delay anomalous
  ionization energy loss. At LHC, Mlt2.5 TeV. Mass
  resolution better than 1
• Neutral R-hadrons. Tagged jet Mlt1.1 TeV. Once
  tagged, identify gluino small energy deposition
• Flippers. Difficulty in tagging
• Gluinonium. Mlt1 TeV, direct mass reconstruction
• Stopped gluinos. Possibility of measuring long
  lifetimes

30
DARK MATTER

• Higgsino ?1.0--1.2 TeV
• W-ino M22.0--2.5 TeV
• B-ino/Higgsino M1?

• B-ino/W-ino M1M2
• Higgs resonance M?mH
• Gravitino induced

Present limit 10-41 --10-42 cm2 Future sensib.
10-44 --10-45 cm2
31
CONCLUSIONS

• Supersymmetry is still the best candidate to
  overthrow the SM, but it suffers from tunings at
  the level of
• Absence of new discoveries at LEP, failure to
  explain the cosmological constant, and
  developments in string landscape suggest a
  possible change of approach to the final theory
• Can we test anthropic solutions?