Supersymmetry searches at colliders

1
Supersymmetry searches at colliders

• L. Pape (CERN)
• Broad Outline
• Some basics, models, sparticle spectra
• (Low energy experiments)
• Present and future accelerators
• Higgs searches
• Sparticle decays
• Existing limits on sparticles
• Future searches

2
Some basic phenomenology

• Contents
• MSSM sparticle contents
• Gauge interactions
• Yukawa couplings
• (Unbroken MSSM Lagrangian)
• SUSY breaking models
• Sparticle spectroscopy
• See lectures by H.Haber

3
MSSM Particle content

• SUSY transforms fermions to bosons and vice
  versa
• QFgt Bgt , QBgt Fgt
• Symmetry ? supermultiplets with same number of
  fermionic and bosonic degrees of freedom
• SM fermion (2 dof) ? complex scalar
• SM gauge boson (2 dof) ? SUSY fermion (gaugino)

• MSSM minimal extension of SM
• Supermultiplet components
• Same gauge quantum
• numbers
• - Differ only by ½ unit of spin

Gauge multiplet Gauge multiplet Chiral multiplet Chiral multiplet
J 1 J 1/2 J 1/2 J 0



4
Quantum Numbers

• Chiral supermultiplet
• e.g. 1st family
• Charge is SU(3),SU(2),U(1)
• Q I3 Y/2
• Gauge supermultiplet
• After EW symmetry breaking
• Mixing
• charginos
• Mixing
• neutralinos

Charge Scalar
Q (3,2,1/3)
Uc (3,1,-4/3)
Dc (3,1,2/3)
L (1,2,-1)
Ec (1,1,2)
Hd (1,2,-1)
Hu (1,2,1)
Fermion VB Charge
(gluino) g (8,1,0)
(Wino) W (1,3,0)
(Bino) B0 (1,1,0)
5
From SM to MSSM interactions

• SM multiplets ? MSSM supermultiplets
• By including superpartners differing by ½ unit in
  spin
• Supermultiplets Chiral (y,f), Gauge (A,l)
• Same supermultiplet ? same couplings in
  interactions
• But amplitudes must be scalars in spin space
• To go from SM to MSSM interaction
• Will not produce all MSSM interactions,
• But it provides a useful mnemonic

Replace pair of SM particles by their
superpartners
6
Gauge interactions (trilinear)

• Trilinear interactions as they control production
  and decay

SM (Ayy)
(Aff)
(lfy)
SM (AAA)
(All)
More formally derived from covariant derivatives
7
Yukawa interactions
m dimensionful parameter
Top Yukawa can never be neglected
Bottom and Tau Yukawas for large tanb
More formally derived from Superpotential
8
Operator dimensions

• Supermultiplets Chiral (y,f), Gauge (A,l)
• Lagrangian dimension (E)
• In field theory Lagrangian density L
• L (E/L3) ? L (E4)
• Fermion fields
• kinetic term ? y (E)3/2
• Scalar fields
• Kinetic term ? f (E)1
• Vectro boson fields
• Kinetic term ? A (E)1

9
Superpotential

• Specifies the Yukawa couplings
• Invariance under SUSY transformations
• Polynomial of order 3 in scalar fields, analytic
  function
• hi Yukawa couplings (matrices in generation
  space)
• m dimension of mass ? mixing of Higgs fields
• eij to make SU(2) scalars (e12 -e211)
• Conserves B and L (Rp1 for SM particles, -1 for
  superpartners)
• But additional terms are allowed which violate
  Rp
• Note W is not a potential (dimension 3)
• Is a function from which to derive pieces of the
  Lagrangian
• Chiral fermions contribution and part of the
  scalar potential

10
Chiral fermions contribution

• Chiral fermions contribution
• Contains fermion mass terms and Yukawa
  interactions
• SM-like mass term after EW symm. Breaking
• mass mixing terms for higgsinos

11
Scalar potential

• F-term, or chiral contribution
• quadratic Higgs term
• mixing L and R sfermions
• D-term, or gauge contribution
• Forced by supersymmetry and gauge invariance
• Quartic Higgs interaction with gauge coupling
  strength
• as m2 gt 0, no vev is generated, masses are 0

12
SUPERSYMMETRY BREAKING

• Unbroken MSSM
• Unbroken SUSY introduces new interactions but no
  new parameters
• All particles are massless
• Superpartners must be heavier than SM particles ?
  SUSY broken
• Soft SUSY breaking (soft no quadratic
  divergences)
• m0,i scalar masses (matrix in generation space)
• m1/2,a gaugino masses
• ? Effective Lagrangian to derive phenomenology

Parametrization of our ignorance of SUSY
breaking mechanism
13
Gauge coupling unification

• Renormalization Group Equations (RGE)
• Connect gauge couplings at some scale q0 to a
  scale q
• ba are constants related to the charges under
  groups U(1), SU(2), SU(3)
• summed over all particles entering the loops,
  e.g.
• SM particles only ba (41/10,-19/6,-7)
• Including MSSM particles ba (33/5,1,-3)
• RGEs allow extrapolation of couplings from weak
  scale,
• linear in a-1 (at 1 loop)

14
Gauge coupling unification

• Do couplings unify at some scale? (GQW1974)
• Precisely known since measurements at LEP (1991)
• Evolving with 2-loop RGEs
• - do not meet if SM only
• - meet if MSSM with
• sparticles around 1-10 TeV
• Gives support to the GUT idea and to MSSM
• With MGUT 2 1016 GeV, aGUT 1/24
• First experimental hint that there is something
  beyond SM

W.de Boer, 1998
15
Mass Universality, MSUGRA

• In general MSSM
• Many new parameters ? MSSM124
• Most parameters involve flavour mixing or CP
  violating phases
• Universal mass parameters
• Catastrophy is evaded by asuming Universality at
  GUT scale
• ? m0,I m0, common scalar mass
• ? m1/2,a m1/2, common gaugino masses
• ? A0,i A0,
• Remaining parameters
• Called MSUGRA

m0 , m1/2 , A0 , B0 , m
16
MSUGRA Spectroscopy(1)
Parameters defined at the GUT scale
Run down to EW scale by Renormalization Group
Equations (RGE)
W.de Boer, 1998

• Sfermions m0
• Squarks increase fast (aS)
• Sleptons increase slower
• Gauginos m1/2
• Gluino increases fast
• Bino/Wino masses decrease (mix with higgsinos)
• ? 2 charginos, 4 neutralinos

log10Q
Usually lightest c01 is Lightest SUSY Particle
(LSP) ? stable ? Emiss
17
MSUGRA Spectroscopy(2)
Higgs mass parameters Hu and Hd at the GUT scale

• Large Yukawa coupling of Hu to t-quark
• Drives mass2 parameter of Hu lt 0
• Triggers EW symmetry breaking
• Radiative EWSB occurs naturally
• in MSSM
• Minimization of Higgs potential
• reduces number of parameters
• tanb vu / vd

m0 , m1/2 , A0 , tanb , sgn(m)
log10Q
18
Focus Point scenario

• Focus Point
• If m0 gtgt Mi, Ai then RGE of MHu determined by
  Mi, Ai
• ? value of MHu at EW scale is independent of m0
• ? Large values of m0 do not imply fine tuning
• Needs tanbgt5 and mt175 GeV
• May have heavy sfermions
• But light gauginos

Feng, Matchev, Moroi, hep-ph/9909334
19
Gaugino mass RGEs

• Universal gaugino masses m1/2 at GUT scale
• Renormalization Group Equations (RGE)
• Weak scale values
• SU(3) unbroken M3physical gluino mass, up to
  QCD corrections
• After SU(2)xU(1) breaking, Wino and Bino masses
  are mixed
• Note same relations apply to GMSB

20
Chargino/neutralino masses

• Gauginos mix with higgsinos
• Off diagonal coupling
• Mass matrices
• Charginos (2x2) matrix M2, m, tanb
• Neutralinos (4x4) matrix M1, M2, m, tanb
• In limit where neglect terms in tanb, simplify to
• ? two extreme cases
• In MSUGRA (GMSB) usually gaugino-like,
  c10Bino, c20,c1Winos

Lightest c are gaugino-like
Lightest c are higgsino-like
21
Squark and slepton masses(1)

• First two families start from m0 at GUT scale
• Yukawas are negligible
• Running dominated by m1/2 and ais
• Splitting by D-term (sfermion)2(higgs)2 after
  SU(2)xU(1) breaking
• At weak scale (approx. formulae)

D-term sum rule
note that mgluino is at most 1.2 msquark (for
m00)
22
Squark and slepton masses(2)

• Third family Yukawa couplings cannot be
  neglected
• At weak scale (tanb 10)
• ? Yukawa couplings decrease mass
• Also L-R mixing SUSY breaking and F-term
• ?
• Similar for sbottom/stau replacing cotb by tanb

Lightest squark
23
Example MSUGRA spectrum

• Stable neutralino LSP
• Low m0 High m0 (Focus Point)

24
Gauge Mediated SUSY Breaking

• Gauge mediation (GMSB) 3 sectors
• Loops , for msoft at EW
  scale
• Gravitino is the LSP (m eV)
• Parameters
• M messenger scale (amount of RGE evolution)
• mass splitting of scalar messengers (F vev of
  X)
• N messenger index, where a 5 contributes with 1
  and a 10 with 3
• m and B obtained from gauge boson mass and tanb

L, M, N, tanb, sign(m)
25

• Gauginos
• Scalars (at messenger scale)
• With C34/3 (0 if singlet), C23/4 (0 if
  singlet), C13/5.(Y/2)2
• Note the different dependence on N

26
GMSB spectroscopy
Guidice,Rattazi, hep-ph/9801271

• LSPgravitino
• Who is NLSP?
• Sparticles decay to NLSP
• Low N
• c01 is NLSP
• High N
• Stau is NLSP
• Typical signature of GMSB
• Emiss g or t or long-lived particles

27
Anomaly Mediated SUSY Breaking

• Principle
• SUGRA Lagrangian has conformal (scale)
  invariance
• But broken at quantum level due to cut-off scale
  (regularization)
• Leads to residual couplings (anomaly) to
  observable fields
• Parameters
• In pure AMSB, only 1 parameter m3/2gravitino
  mass
• But leads to tachyonic sleptons ? introduce m0
  (universal scalar mass)
• Also tanb and m
• After imposing correct EWSB

m3/2, m0, tanb, sign(m)
28
AMSB Spectroscopy

• Charginos/neutralinos
• (M1,M2,M3)(2.81-7.1)
• Wino lighter than Bino
• c1 nearly degenerate with c10
• m (from EWSB) larger than in MSUGRA
• Scalars
• Sleptons L and R of 1st 2 families nearly
  degenerate (accidental) with mass m0
• Signature
• Emiss, like MSUGRA
• c1? p c10 (soft pion)
• may be long lived

Gheghetta, Giudice, Wells, hep-ph/9904378
(m3/236 TeV, tanb5, mlt0)
29
Comparison of Spectra

• Mass relative to c1

30
R-parity violation

• SUSY permits to add terms to Superpotential
• Yukawa couplings with i,j,kgeneration indices
• Violate conservation of R-parity Rp(-1)3BL2S
• 1st 2 terms DL1, last term DB1
• New parameters
• l antisymmetric by SU(2) invariance iltj, 9terms
• l 27 terms
• lantisymmetric by SU(3)C invariance jltk, 9
  terms
• ? 45 new free parameters

31
R-parity violation

• Constrained by proton lifetime
• l and l non zero
• Several other low energy constraints
• Review by H.Dreiner hep-ph/9707435
• LSP Neutralino decays
• Via fermion-sfermion pair, followed by RPV decay
• Missing energy signature is lost
• New signatures appear (additional leptons and/or
  jets)
• LSP could be sfermion, decaying via RPV
• Single production of sfermions
• E.g. sneutrino at LEP or squark at HERA

32
SUSY Signatures
Supersymmetry, MSUGRA
ETmiss, Inclusive searches Dileptons, Taus, Z0,
h0 Bottoms mass reconstruction
Gauge Mediated
Photon events ETmiss Multi-tau events
ETmiss Long-lived sparticles
R-parity violation
Multi-leptons Multi-jets
33
Low Energy Measurements

• Contents
• b ? s g decay
• Other FCNC decays of b and s
• gm 2 saga
• Many others
• Proton decay, K0-K0bar oscillations, lepton
  violating decays, CP violation, electric dipole
  moments, atomic parity violation, LEP/SLC
  precision measurements
• May bring first evidence for physics beyond the
  SM
• ? Keep eyes wide open!
• See lectures of D.Wyler and W.Hollik

34
Accelerators

• Contents
• Present accelerators
• Future funded accelerators
• Future proposed accelerators

35
Present accelerators

vs, GeV pb-1/exp
LEP ee- ADLO
LEP 1 1989-95 91 150
LEP 2 95-2000 130-208 700
Tevatron ?p-p CDF,D0
Run 1 1800 110
Run 2 01-08 2000 ? (3-20.103)
HERA ep H1,Zeus
1993-97 300 50
98-07 318 ?(1.103)
36
Future accelerators

• LHC (funded, at CERN)
• Expected to start in Summer 2007, true data
  taking 2008
• Ecm 14 TeV, pp
• Run 3 years at luminosity1033cm-2s-1 (10
  fb-1/year)
• Continue at 1034cm-2s-1 (100 fb-1/year)
• ee- Collider
• 3 techniques proposed TESLA, NLC, JLC
• Start at 0.5, upgrade to 1 TeV
• Decision on technique this year
• Detailed TDR for 2007, site selection 2008(?)
• CLIC up to 3-5 TeV
• Feasibility to be demonstrated for 2010
• Construction could start in 2013 (last 7 years)
• Others m collider, VLHC

37
Sparticle production

• Two basically different approaches
• ee- collider
• Pure partonic interactions
• fixed Ecm partonic energy (kinematical
  constraints)
• allows E scans (e.g. thresholds) to be
  made/polarization
• ? precision measurements
• but limited Ecms
• Hadron collider (p-p or ?p-p)
• Variable partonic energy, e.g.
• but machine reaches higher energy
• ? exploratory machine

38
SUSY Higgses

• Contents
• Higgs mass in SM
• Higgs mass in MSSM
• Higgs mass radiative corrections
• Production in ee- colliders
• Limits from LEP and Tevatron
• Future searches Tevatron, LHC and LC

39
Higgs mass in SM (1)

• One Higgs field SU(2) doublet
• Masses generated by Higgs v.e.v.
• V(f) m2f2 l f4,
• with m2lt0 and lgt0
• Higgs mass MH2 2 v2 l(v) for v 175 GeV
• Parameters m and l are free in SM
• ? Higss mass is undetermined in SM

40
Higgs mass in SM (2)

• Limits on Higgs mass can be derived from
  rad.corr.
• RGE evolution of l due to Higgs and top
  (htYukawa) loops
• Perturbativity ht ltlt l
• l2 dominates ? strong coupling
• Upper limit on MH
• Vaccum stability ht gtgt l
• -ht4 dominates ? l(t) negative
• Potential unbounded from below
• Lower bound on MH
• SM valid up to Planck scale

Ridolfi, hep-ph/0106300
130 lt MH lt 180 GeV
41
Higgs in MSSM

• In MSSM 2 Higgs fields ? 8 degrees of freedom
• 3 are used to make W and Z0 massive
• MSSM contains 5 physical Higgs states
• 2 charged scalars H
• Mixture of Hd- and Hu, fixed by tanb
• 1 neutral CP-odd A0
• Mixture of Im(Hd0) and Im(Hu0), fixed by tanb
• 2 neutral CP-even h0 and H0
• Mixture of Re(Hd0) and Re(Hu0), with mixing
  angle a

42
Higgs mass at tree level

• From scalar potential, tree level masses are
• Higgs masses depend on only 2 parameters mA and
  tanb
• tanb?1 mh0, mH2MZ2mA2
• tanb?8mh, mH0min,max(MZ,mA)
• Mass hierarchy at tree level
• 0 mh MZcos2b
• mh mA mH0
• mH0 MZ
• mH MW
• Expect light h0 (coupling of f4 term of gauge
  strength)
• ? observable at LEP2
• But radiative corrections are large, especially
  on mh

43
Higgs mass radiative corrections

• Top loop corrections 1-loop leading log
  approximation
• Introduces a dependence on top and stop masses
• More accurate calculationalso on stop mixing
  XtAt-mcotb
• In MSSM, mh0 has upper bound
• Increases with tanb
• Increases from min Xt/MSUSY0
• To max (Xt/MSUSY)26
• (for MSUSY 1 TeV, mt175 GeV)
• ? Lower than preferred SM range

Carena et al., hep-ph/9504316
mh 130 GeV
44
Higgs masses, summary
45
Higgs decays

• Light Higgs h0 lt130 GeV
• B(bb)80-85, B(tt) 8, B(mm) 2.10-4, B(gg)
  1.5.10-3
• For mhgt120 GeV B(WW) and B(ZZ) increase
• H0/A0 (gt130 GeV)
• Large tanbgt10 B(bb) dominates, B(tt) 10,
• Small tanb H0?WW, ZZ, hh dominate
• and A0?Zh dominates
• but for m(H,A)gt350 GeV B(tt)90
• H
• m(H)ltmt B(tn)100
• For m(H)gt200 GeV B(tb) dominates, B(tn)10
• All can decay to gauginos (depends on parameters)

46
Production in ee- machines(1)

• Higgsstrahlung Fusion (small)
  Associated production

a is mixing angle of h0 and H0
The processes are complementary
47
Production in ee- machines(2)
48
Higgs search topologies

• h0 Z topologies
• B(h0?b-bbar)86, B(h0?t-tbar)8
• Also ,
  (B.R.5.4) included in search
• For mh gt 130 GeV WW and ZZ become important
• h0 A topologies
• For mAlt350 GeV
• For mAgt350 GeV may be
  important

B.R.9.3
B.R.64
B.R.18
49
Higgs mass limits from LEP
LEP 95 C.L. exclusion from ADLO
Maximal stop mixing (mhmax)
No stop mixing
Large mA
mh114.1 GeV
For mhmax
mh91.0, mA91.9 GeV
tanb 2.4
50
Non-conventional Higgses

• H?gg
• Crucial channel for LHC, but small BR (2.10-3)
• So far, insufficient sensitivity at LEP and
  Tevatron
• H invisible decays
• E.g. decay to neutralinos
• Easy at LEP, ADLO limit 114.4 GeV
• Flavour-blind H search
• Usually search H?bb, but BR may be suppressed
• Look for decays into 2 jets or tt in HZ channel
• LEP (preliminary) limit is 112.5 GeV
• Charged H
• Decays to cs or tn
• LEP (preliminary) limit about 80 GeV

51
Charged Higgs at Tevatron

• Searched in t-tbar, t?Hb
• BR large if tanb large or very low
• Indirect search
• Measure s(ttbar), t?Wb
• Theory ? limit on BR(t?Hb)
• At tanbgt1
• ? direct search
• At very low tanb
• Ratio method
• Evts 1ljets from WbWb or HbWb
• Evts 2ljets only from WbWb
• ? ratio gives limit BR(t?Hb)
• Caveat neglects other decays

CDF
52
Future searches Tevatron(1)

• Dominant cross-section
• Gluon fusion (top/bottom loop)
• Decay hopeless
• But with leptonic decays for
  large mh
• Also
• with , triggered by
• leptonic decay of W or Z
• for mh lt 140 GeV

Gluon fusion
s (pb)
NNLO
NLO
LO
mH
Anastasiou, Melnikov, hep-ph/0207004
2 curves mmH/2,2mH
53
Future searches Tevatron(2)

• Tevatron Run II
• After 2 fb-1
• Excl 120 GeV (95 CL)
• After 11 fb-1 for 2008
• Excl 180 GeV (95 CL)
• 3 s lt 130, 155-175 GeV
• 5 s lt 110 GeV
• Discovery up to 130 GeV
• would require 30 fb-1

Carena et al., hep-ph/0010338
54
Future searches LHC(1)

• Dominant cross sections
• Gluon fusion
• Higgsstrahlung, e.g. Hb-bbar at high tanb
• Gauge boson fusion (Hqq) low, especially at high
  tanb)
• Associated production with VB (strongly
  suppressed)

Spira, Zerwas
tanb1.5
pb
tanb30
pb
55
Future searches LHC(2)

• Low Higgs mass region
• H?gg most powerful
• Already with 30 fb-1 get 5s up to 150 GeV
• 60 fb-1
• gt60-100 fb-1
• ? several modes observable
• Higher masses gt 130 GeV
• H?WW,ZZ
• Already with 10 fb-1

SM(-like) Higgs
56
Future searches LHC(3)

• Up to highest masses,
• with lt 30 fb-1
• Using H?WW,ZZ

SM(-like) Higgs
57
Future searches LHC(4)

• h0?gg only for mAgt200 GeV
• Importance of
• tth, h?bb and qqh, h?tt
• Still mAlt130 GeV not covered (mhlt120 GeV, not
  SM-like)
• Hope to cover with
• gg?bbh, h?mm,tt
• (or sparticle decays)
• Caveat
• gg?h0 from loops with t or b
• In SUSY also stopsbottom
• Stop-top negative interference
• May preclude discovery by h0?gg if

58
Future searches LHC(5)

• Heavy neutral Higgses
• Based on H,A?tt, mm
• No sensitivity for large mA and low/intermediate
  tanb
• Charged Higgs
• Based on H?tn, tb
• No sensitivity for large mA and low/intermediate
  tanb
• Overall conclusion for LHC
• Should discover Higgs, but
• Still holes for m(h0)lt120 GeV
• May miss H0/A0 if large mA and low tanb

59
Future searches LHC(6)

• Higgs from sparticle decays
• ? see later

60
Future searches LHC
Old figure
61
Future searches LC

• Cross-section
• Familiar from LEP200
• Increase of fusion

62
Future searches LC

• Light Higgs likely discovered before LC start
• LC for precision measurements
• 500 GeV LC measurements
• mass to 0.05
• determine spin/parity
• Branching ratio measurement
• for 500 fb-1 (2 years)
• May need multi-TeV machine for heavy Higgses

Battaglia et al., hep-ex/0201018
63
Future searches MuCOL

• MuCOL may produce Higgs in s-channel
• Expects 1 fb-1 per year
• can have very small beam energy spread
• Ideal for line shape measurement
• could measure
• Mass to 0.1 MeV (at 110 GeV)
• Width to 0.5 MeV
• Cross-section to 5

64
Sparticle decays

• Contents
• Chargino/neutralino
• Sleptons
• Squarks and gluinos

65
Chargino/neutralino decays
Chargino Chargino Neutralino Neutralino





Loop decay
Are couplings with gauge strength Dominant one
depends on spectrum and c/c0 composition
66
Slepton decays

• Slepton decay
• sleptonL prefers a Wino (c1 or c02 in MSUGRA ?
  cascade)
• sleptonR only decays to a Bino (c01 in MSUGRA)
• Stau decays may be more complicated
• At large tanb, Yukawa couplings contribute
• ? can decay to higgsino
• e.g.
• But only is possible
• and is forbidden, as
  higgsino requires helicity flip

67
Squark/gluino decays

• Squark strong decay for
• Preferred if kinematically allowed
• Electroweak decay
• squarkL prefers a Wino (c1 or c02 in MSUGRA ?
  cascade)
• squarkR only decays to a Bino (c01 in MSUGRA)
• Stop EW decay
• For light stop (m lt m(c1)) above decays
  forbidden
• ? Loop decay may dominate
• Gluino decay for
• If lighter than squarks
• Caveat only main decay modes
• Others in special regions of parameter space,
  e.g.
• For stop/sbottom Yukawa couplings may be relevant

68
Existing Limits, stable c01

• Contents
• From Tevatron and LEP direct searches
• LEP limits on LSP mass
• Constraints on MSUGRA parameter space
• Including CDM constraints
• (Limits also exist for)
• GMSB, AMSB scenarios
• R-p violating couplings
• (See http//lepsusy.web.cern.ch/lepsusy/Welcome.ht
  ml)

69
Slepton limits from LEP

• Sneutrino, LEP1
• Expect
• ? invisible in Z0 decays
• LEP1 limit DGinvlt 2 MeV
• Sneutrino width
• Limit on sneutrino mass (assuming 1 family)

• Charged sleptons, LEP2
• Based on

70
Squark/gluino limits

• Limits from LEP and Tevatron, examples

Complementarity between LEP and Tevatron
71
Chargino/neutralino production

• Charginos
• - s typically pb
• negative interference s- and t-channel
• For gaugino-like charginos
• s negligible for small sneutrino mass
• ? loss of sensitivity

• Neutralinos
• - s typically pb
• t-channel only gaugino-like
• increases for light selectron
• ?some compensation for x-sect loss
• in gaugino-like charginos

72
Chargino/neutralino topologies

• Chargino main decay mode for LEP
• Use acoplanarity
• Neutralino mainly
• ? acoplanar ll- or 2-jets
• Other production modes also considered (c02 c02,
  c02 c03, )

B.R.1/9
B.R.4/9
B.R.4/9
small background
73
Chargino limits

• Charginos large m0
• Gaugino-like
• Depends on sneutrino mass

• Small DMM(c1)-M(c10)
• Higgsino-like
• Stable, IP, 2nd Vx, ISR
• Is also a limit on LSP!

74
Direct search limits
Channel M gt (GeV) DM
43.7 EW measts ADLO
99 10 GeV ADLO
95 10 GeV ADLO
85 10 GeV ADLO
95 20 GeV ADLO
96 20 GeV ALO
94 20 GeV ADLO
195 - CDF
103.5 Large m0 ADLO
92.4 Small DM ADLO
75
Indirect limits on LSP(1)

• No full coverage from neutralinos only
• ? no direct limits on c10 mass
• Requires to combine results from
• Chargino searches weak if gaugino and low
• Neutralino searches weak if not higgsino,
• but improves if gaugino for low
• Slepton searches
• -LEP2 limit on using sum rule
• -LEP1 limit on
• Scalar mass universality
• ? Allows exclusion of low regions of M2 for
  fixed m0
• Higgs searches excludes low tanb

76
Indirect limits on LSP(2)

• Example of interplay of these constraints
  (MSUGRA)
• Yellow no REWSB
• Light blue inconsistent with LEP1 measurements
• Green excluded by chargino
• Red excluded by slepton
• Blue excluded by hZ
• Regions depend on tanb

77
Indirect limits on LSP(3)

• In MSSM

• In MSUGRA

M(c01LSP) gt 45-50 GeV
78
Constrained MSUGRA

• GUT universality of gauginoscalar masses REWSB
• m0 , m1/2 , A0 , tanb , sgn(m)

Weakens at large tanb
Depends weakly on tanb
Stronger at large tanb
79
Constrained MSUGRA

• CDM constraints after WMAP

80
CMSUGRA allowed regions

• More quantitavely

J.Ellis et al.,hep-ph/0303043

• -red stau LSP
• -green excluded by
• -cyan CDM constraint
• -blue CDM constraint
• -pink region preferred by
• (gm-2) of Davier02

81
CMSUGRA allowed lines

• With WMAP narrow tanb dependent lines

• Main c20 decaysdileptons

Battaglia et al.,hep-ph/0306219
BR
J.Ellis et al.,hep-ph/0303043
0.1
m1/2
0.1
m1/2
Importance of tt decays (at large tanb)
82
Sparticle production at LHC

• Contents
• Squark and gluino production
• Stop production
• Slepton production
• Direct chargino/neutralino production

83
Squark and gluino production

• Contributing LO processes

84
Squark/gluino cross sections
Beenakker et al., hep-ph/9610490

• NLO cross sections at LHC
• NLO calculation is important
• sNLO (1.1-1.9) sLO
• Remaining scale dependence
• 15 (uncertainty)
• At 1 TeV, summed s gt 1 pb
• 1 fb at 2.5 TeV

85
Stop cross section

• NLO cross section at LHC
• SUSY-QCD corrections
• sNLO 1.4. sLO
• remaining scale dependence
• 10-15 (uncertainty)
• Only diagonal production is relevant,
• At 1 TeV, summed s 20 fb

Beenakker et al., hep-ph/9906298
86
Slepton pair production
Baer et al., hep-ph/9712315

• Slepton pair production at NLO
• Drell-Yan process
• mediated by Z or W
• With QCD corrections at LHC
• sNLO (1.25-1.35) sLO
• Cross section is small
• lt1 fb at 500 GeV

(pb)
87
Chargino/neutralino production

• Chargino/neutralino direct production
• With QCD corrections at NLO
• sNLO (1.1-1.4) sLO
• Interesting
• with
• ? trilepton final state

(pb)
Beenakker et al., hep-ph/9906298
88
Future Searches

• Contents
• At LHC (discovery reach mass reconstruction)
• At ee- Linear Colliders (precision measurements)
• Extrapolation to the GUT scale

89
Sparticle production at LHC
90
LHC inclusive reach (1)

• Using ETmiss jets signature
• s 1 pb at 1 TeV
• After 1 year 10 fb-1/year
• at low luminosity
• ? already significant reach
• High lumi 100 fb-1/year
• With 300 fb-1,

Discovery at 5 s.d.
CMS
squarks and gluinos up to 2.5 TeV
91
LHC inclusive reach (2)

• Using ETmiss leptons signature
• In large area,
• Several topologies are
• simultaneously observable

CMS
But does not uniquely identify SUSY
ETmiss likely to be a first hint
92
Decay signatures in (m0,m1/2)

• To prove SUSY (MSUGRA)
• Need more specific signatures
• 100
• significant

More general than strict MSUGRA
93
Decay chain to dileptons
94
Final states with dileptons (1)
ATLAS

• M(ll) very sharp end point
• ?
• M(llq) softer edge,
• Obtained by extrapolation
• ?

M(ll)
M(llq)
95
Final states with dileptons (2)

• M(l1q)
• M(l2q) leptons in same
• configuration as for M(ll)max
• ?Can distinguish M(l1q)max from M(l2q)max
• 4 unknown masses
• 4 endpoints
• ? all masses can be determined
• More information available constraints
• (other end points, gluino decay)

96
End points and configurations
97
Decay chain to h0 or Z0
98
Final states with h0 or Z0

• Higgs can be reconstructed
• from b-bbar jets
• Could be a h0 discovery channel
• Z0 reconstructed from di-lepton decay
• Decay chain is shorter than for di-leptons
• Either need start from gluino
• M(q1h0),M(q2h0),M(qq),M(qqh0)
• to determine 4 masses
• 2. Or start from squark and combine with another
  channel

ATLAS
M(bb)
99
Multiple end points in decays

• Multiple decay modes
• Multiple heavy c0i decays
• D1
• D2
• D3
• D4
• ATLAS, Point SPS1A
• (m0100, m1/2250, tanb10)

CMS
ATLAS
100
LHC summary

• LHC could discover SUSY quite early
• With 10 fb-1 squarks/gluinos up to 1.5-2 TeV
• Ultimate reach (300 fb-1) up to 2.5 TeV
• LHC can also reconstruct sparticle masses
• For all decay modes of c02, even in tt decays
• Reasonable accuracy
• (ATLAS, Gjelsten et al., ATL-PHYS-2004-007,
  SPS1A)
• DM 5 GeV for neutralinos and sleptons (2.5-5)
• DM 10-15 GeV for gluino and squark (jet
  E-resolution) (2-3)
• Futher work needed
• (cross-sections, spin correlations, flavour
  identification, )

101
Comparison LHC/LC/CLIC

• Complementary reach
• LHC h0, squarks, gluino
• eeCOL sleptons, gauginos
• Ecms limited
• Not fully representative
• Precision is also important
• May need gt3 TeV to unravel whole spectrum

M.Battaglia et al.,hep-ph/0306219
102
Lepton Colliders

• More precise than LHC
• E.g. smuon pair production
• 2 edges?determines both masses
• Precision 2-3 at 1 TeV mass
• Threshold scan improves precision further
• Precision 1-2 at 1 TeV mass
• Improves over LHC by 5-10 for neutralino and
  slepton
• Can use beam polarization
• Increase/decrease cross section selectively
• for signal and background
• But

CLIC 3 TeV
Limited by beam energy
103
Identifying the model

• Topology photons, excess leptons or jets,
• Taus from MSUGRA or GMSB
• Distinguish higgsino-like from AMSB?
• Distinguish MSUGRA from UED?
• Use decay BR? Production cross-sections?

104
Extrapolation to GUT scale

• LHC only LHC LC

Blair, Porod, Zerwas, hep-ph/0011367
105
Conclusion

• Today completely in the dark (SM works too well)
• Something must exist beyond the SM
• But large number of candidate models
• Among them, SUSY is a respectable candidate
• Which SUSY? MSUGRA, GMSB, AMSB, RPV, NMSSM,
• Hope to see something at LHC (light Higgs!)
• Then, will require another generation of
  accelerators
• LC, CLIC, MUCOL, VLHC,
• It is time that we discover something!

Eagerly need experimental guidance
106
Further reading (biased sample)

• Basic MSSM
• Perspectives on Supersymmetry, World Scientific,
  Singapore 1998, ed. G.L.Kane
• S.P.Martin, A Supersymmetry Primer,
  hep-ph/9709356 v.3
• H.Haber and M.Schmitt, Supersymmetry, PDG2004,
• http//pdg.lbl.gov/
• Higgs
• The Higgs Hunters Guide, Addison-Wesley 1990,
  ed. J.F.Gunion, H.E.Haber, G.Kane, S.Dawson
• Perspectives on Higgs Physics, World Scientific,
  Singapore 1993, ed. G.L.Kane
• M.Spira, P.M.Zerwas, Electroweak symmetry
  breaking and Higgs physics, hep-ph/9803257