S' Kraml CERN

1
The Quest for SUSY issues for collider physics
and cosmology

• S. Kraml (CERN)
• 1-3 Dec 2006

2

• Supersymmetry (SUSY)
• is the leading candidate for physics
• beyond the Standard Model (SM).
• Symmetry between fermions and bosons
• Qafermiongt bosongt

This combines the relativistic external
symmetries (such as Lorentz invariance) with the
internal symmetries such as weak isospin.
unique extension of relativistic symmetries of
space-time!
3
recall Arkani-Hameds comments on the unification
of space and time...
4

• __________________________________________________
  ______
• The motivations for TeV-scale SUSY include
• the solution of the gauge hierachy problem
• the cancellation of quadratic divergences
• gauge coupling unification
• a viable dark matter candidate
• __________________________________________________
  ______

• ... predicts a partner particle for every SM state

5

• The search for SUSY is hence
• one of the primary objectives
• of the
• CERN Large Hadron Colider
• and a future int. ee_ linear collider!

6

• This talk
• SM problems and SUSY cures
• Naturalness and hierachy problems
• Gauge coupling unification
• The minimal supersymmetric standard model
• Particle spectrum
• Collider searches LHC, ILC
• The cosmology connection
• Dark matter
• EW phase transition and baryon asymmetry

7

• SM problems
• and SUSY cures

8
The hierachy and naturalness problems

• To break the electroweak symmetry and give masses
  to the SM particles, some scalar field must
  acquire a non-zero VEV.
• In the SM, this field is elementary, leading to
  an elementary scalar Higgs' boson of mass mH.
  However,

where L is the scale (cut-off) up to which the
theory is valid.
9

• These large corrections to the SM Higgs boson
  mass,
• which should be mHO(mW), raise problems at two
  levels
• to arrange for mH to be many orders smaller than
  other fundamental mass scales, such as the GUT
  or the Planck scale ? the
  hierarchy problem,
• to avoid corrections dmH2 which are much larger
  than mH2 itself ? the
  naturalness problem.

10
The supersymmetric solution
XXX
XXX
11
A light Higgs
XXXX
XXXX
XXXX
c.f. talk by W. Hollik
12
c2 fit of the Higgs boson mass from EW precision
data as of Summer 2006
13
Radiative electroweak symmetry breaking
Heavy top effect, drives mH2 lt 0
EW scale
GUT scale
14
Grand unification
.

• GUTs attempt to embed the SM gauge group
  SU(3)xSU(2)xU(1) into a larger simple group G
  with only one single gauge coupling constant
  g.
• Moreover, the matter particles (quarks leptons)
  should be combined into common multiplet
  representations of G.
• Prediction Unification of the strong, weak and
  electro-magnetic interactions into one single
  force g at MX.
• NB If MX is too low ? problems with proton decay

15

• 1-loop renormalization group evolution of gauge
  couplings
• SM
• MSSM

16
(No Transcript)
17
One can also re-write this as
18
XX
Can also be turned into a prediction of the weak
mixing angle .....
19

• The MSSM

20
Minimal supersymmetric model

• MSSM minimal supersymmetric standard model

gauginos higgsinos mix to 2 charginos 4
neutralinos
Lightest neutralino LSP
2 Higgs doublets ? 5 physical Higgs
bosons neutral states scalar h, H
pseudoscalar A charged states H, H-
21
XXXX
22
(No Transcript)
23
(No Transcript)
24
Minimal supergravity (mSUGRA)
Universal boundary conditions _at_ GUT scale
Heavy top effect, drives mH2 lt 0
univ. gaugino mass
univ. scalar mass
25
Recall Light Higgs
XXXX
XXXX
XXXX
c.f. talk by W. Hollik
26
R parity symmetry under which SM particles are
even _
and SUSY particles are odd

• If R parity is conserved
• SUSY particles can only be produced in pairs
• Sparticles always decay to an odd number
• of sparticles
• the lightest SUSY particle (LSP) is stable
• any SUSY decay chain ends in the LSP,
• which is a dark matter candidate

27
The scale of SUSY breaking
28
Goldstino and Gravitino
29
Gravitino mass
30

• SUSY _at_ colliders

31
Large Hadron Collider

• New accelerator currently built at CERN,
  scheduled to go in operation in 2007
• pp collisions at 14 TeV
• Searches for Higgs and new physics beyond the
  Standard Model
• discovery machine,
• typ. precisions O(few)

32
SUSY searches at LHC
33
Spectacular and large signal
From Meff peak ? first/fast measurement of
SUSY mass scale to ? 20 (10 fb-1, mSUGRA)
Caution also other BSM models lead to missing
energy signature ? need spin determination
34
Compare with Higgs search
c.f. talk by G. Dissertori
35
Mass measurements cascade decays
Mass reconstruction through kinematic endpoints
Allanach et al., hep-ph/0007009
Typical precisions (a) few
ATLAS, G. Polesello
36
International Linear Collider

• ee- collisions at 0.5-1 TeV
• Tunable beam energy and polarization
• Clean experimental env.
• Precision measurements of O(0.1), c.f. LEP
• Global initiative, next big accelerator after
  LHC?

37
ILC Precision measurements with tunable beam
energy and polarization
TESLA TDR
can reach O(0.1) precision
see talk by H.-U. Martyn
38
High-scale parameter determination
c.f. talk by W. Porod
39
The cosmology connection
Higgs?
SUSY?

• dark matter
• dark energy
• baryon asymmetry
• inflation
• ....

1 GeV 1.3 1013 K
40
What is the Universe made of?

• Cosmological data
• 4 0.4 baryonic matter
• 23 4 dark matter
• 73 4 dark energy
• Particle physics
• SM is incomplete expect new physics at the TeV
  scale
• Hope that this new physics also provides the
  dark matter
• Discovery at LHC, precision measurements at ILC ?

41
WIMPs (weakly interacting massive particles)

• DM should be stable, electrically neutral,
  weakly and gravitationally interacting
• WIMPs are predicted by most theories beyond
  the Standard Model (BSM)
• Stable as result of discrete symmetries
• Thermal relic of the Big Bang
• Testable at colliders!

Neutralino, gravitino, axion, axino, LKP, T-odd
Little Higgs, branons, etc., ...
BSM dark matter
42
Relic density of WIMPs (weakly interacting
massive particles)

• Early Universe dense and hot WIMPs in thermal
  equilibrium
• Universe expands and cools WIMP density is
  reduced through pair annihilation Boltzmann
  suppression ne-m/T
• Temperature and density too low for WIMP
  annihilation to keep up with expansion rate ?
  freeze out

Final dark matter density Wh2
1/ltsvgt Thermally avaraged cross section of all
annihilation channels
43

• Neutralino LSP
• as dark matter candidate

44
Neutralino system
Gaugino ms
Higgsino mass
Neutralino mass eigenstates
? LSP
45
Neutralino relic density
c0 LSP as thermal relic relic density computed
as thermally avaraged cross section of all
annihilation channels ? Wh2 1/ltsvgt
Wh2 0.1 with 10 acc. puts strong bounds on the
parameter space
46
Annihilation into gauge bosons

• cc ? WW / ZZ mainly through t-channel chargino /
  neutralino
• exchange typically also some annihilation into
  Zh, hh
• Does not occur for pure bino LSP needs
• to be mixed bino-higgsino (or bino-wino)
• Pure wino or higgsino LSP
• neutral and charged states
• are a mass-degenerate triplet,
• (co)annihilation too efficient
• Right relic density for
• (m-M1)/M1 0.3,
• (M2-M1)/M1 0.1

hep-ph/0604150
47
Coannihilations

• Occur for small mass differences between LSP and
  next-to-lightest sparticle(s) efficient channel
  for a bino-like LSP
• Typical case coann. with staus
• Key parameter is the mass difference
• DM mNLSP-mLSP
• Other possibilities Coannihilation with stops
  (DM20-30GeV), coann. with chargino and the 2nd
  neutralino (in non-unified models)

48
mSUGRA parameter space

• GUT-scale boundary conditions m0, m1/2, A0
• plus tanb, sgn(m)
• 4 regions with right Wh2
• bulk (excl. by mh from LEP)
• co-annihilation
• Higgs funnel (tanb 50)
• focus point (higgsino scenario)

49
Prediction of Wh2 from colliders

• Requires precise measurements of
• LSP mass and decomposition
• bino, wino, higgsino admixture
• Sfermion masses (bulk, coannhilation)
• or at least lower limits on them
• Higgs masses and widths h,H,A
• tanb

Required precisions investigated in, e.g.
Allanach et al, hep-ph/0410091 and Baltz et al.,
hep-ph/0602187
c.f. talks by H.U. Martyn B. Allanach
NB determination of ltsvgt also gives a prediction
of the (in)direct detection rates
50

• For a precise prediction of Wh2
• we need precision measurements
• of most of the SUSY spectrum
• (masses and couplings)
• ? LHCILC ?

51

• Gravitinos

52
Recall

• If m3/2 gt mLSP, the gravitino does not play any
  role in collider phenomenology
• However, it is possible that the gravitino is the
  LSP
• Phenomenology as before, BUT all SUSY particles
  will cascade decay to the next-to-lightest
  sparticle (NLSP), which then decays to the
  gravitino LSP.
• Note 1 the NLSP may be charged
• Note 2 since the couplings to the gravitino are
  very weak, the NLSP can moreover be
  long-lived
• ? Gravitino as dark matter candidate
• ? Collider pheno characterized by the nature and
  lifetime of the NLSP

53
Implications from cosmology

• The most popular model for explaining the
  apparent baryon asymmetry of the Universe is
  LEPTOGENESIS
• ? out-of-equilibrium decays of heavy singlet
  neutrinos
• Leptogenesis requires
• a reheating temperature
• TR gt 109 GeV
• At high TR an unstable G is
• severely constrained by BBN
• ? Leptogenesis is OK
• if the gravitino is the LSP

Buchmüller et al
54
Gravitino dark matter

• Neutralino NLSP is excluded by BBN
• Best studied alternative stau NLSP
• Need to confirm spin-3/2 L. Covi et al

c.f. talk by H.-U. Martyn
55

• instead of conclusions ...

56

• Since its discovery some ten years ago,
  supersymmetry has fascinated many physicists
• Hans-Peter Nilles, Phys. Rept. 110 (1984)

57

• The discovery of supersymmetry is
• tantamount to the discovery of
• quantum dimensions of space-time
• David Gross, CERN Colloq., 2004

58

• whether or not it is SUSY ....
• The exploration of the TEV energy scale
• at the LHC and a future ILC
• will lead to
• fundamental new insights on physics
• at both the smallest and the largest scales.

59

• PS SUSY phenomenology is extremly rich,
• and this talk could only scratch on the surface.
• SUSY at this meeting
• MSSM predictions W. Hollik
• Charginos at the ILC T. Robens
• Parameter determination H.-U. Martyn,
  W. Porod
• SUSY CP violation T. Kernreiter, K.
  Rolbiecki
• Neutrino masses F. Deppisch
• SUSY breaking N. Uekusa
• SUSY dark matter A. Provenza, B.
  Allanach

60

• backups

61
Assume we have found SUSY with a neutralino LSP
and made very precise measurements of all
relevant parameters What if the inferred Wh2
is too high?
62
Solution 1Dark matter is superWIMP
e.g. gravitino or axino
63
Solution 2R-parity is violated after all

• RPV on long time scales
• Late decays of neutralino LSP reduce the number
  density actual CDM is something else
• Very hard to test at colliders
• Astrophysics constraints?

64
Solution 3Cosmological assumptions are wrong

• Our picture of dark matter as a thermal relic
• from the big bang may be to simple
• Universe after Inflation radiation dominated?
• Non-thermal production?
• Assumptions in WMAP data ? Wh2 ?