Transcript SUSY searches at future colliders

SUSY 2
Jan Kalinowski
Outline
Constructing the MSSM
SUSY must be broken
SUSY: experimrental status
Prospects for the LHC
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Supersymmetry, part 2
MSSM: particles and sparticles
SM
Spin-1/2
Spin-1
Spin-0
SUSY
quarks (L&R)
leptons (L&R)
Spin-0
neutrinos (L&?)
gluon

Z0
W±
h0
H0
A0
H±
Extended higgs sector
(2
doublets)
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squarks (L&R)
sleptons (L&R)
sneutrinos (L&?)
gluino
Bino
B
W0
Wino0
Spin-1/2
Wino±
~0
H1
~0
H2
~±
H
Supersymmetry, part 2
After
Mixing
4 x neutralino
2 x chargino
Exact SUSY
Superpotential
But most general gauge-invariant and renormalisable admits also
If both present
rapid proton decay
Minimal choice (MSSM) : R-parity = (-1)2S+3B+L conserved
Consequences:
SUSY particles produced in pairs
SUSY particles decay into SM + odd number of SUSY particles
All SUSY particles will eventually decay into LSP
LSP stable
 some must have survived from Big Bang
 weakly interacting massive particle
 candidate for cold dark matter
LSP neutral
 typical collider signature: missing energy
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Exact SUSY
Exact SUSY => no new parameters
SUSY implies relations between masses and couplings:
gauge coupling
= Yukawa coupling
crucial for
hierarchy
problem
scalars and fermions from the same multiplet have equal masses
SUSY must be broken
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Supersymmetry, part 2
SUSY must be broken
Spontaneous breaking of global SUSY requires <0|H|0> > 0
V>0 implies that Fi or Da cannot simultaneously vanish for any
values of the fields
F-term breaking requires a singlet chiral superfield
not possible within the MSSM
D-term breaking via xa
does not work in the MSSM since gives charge and color-breaking
minima
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Supersymmetry, part 2
SUSY must be broken
Other problems with spontaneous susy breaking
Mass sum rule
not all superpartners could be heavier than SM particles
difficult to get phenomenologically acceptable masses
Difficult to give masses to gauginos
…..
Problems can be overcome with additional fields in ”hidden sector”
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Supersymmetry, part 2
SUSY must be broken
Invoke a hidden sector where SUSY breaking occurs
Hidden sector
Flavour blind
MSSM sector
mediators
In the hidden sector the F and/or D terms of some non-MSSM develop
VEV
phenomenology depends mainly on mechanism for communicating SUSY
breaking rather than on SUSY-breaking mechanism itself
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Unconstrained MSSM
No particular SUSY breaking mechanism assumed
L. Girardello, M. Grisaru ’82
No additional mass terms for chiral fermions
Relations between dimensionless couplings unchanged
Most general case: 105 new parameters
Question: what is the scale of SUSY breaking parameters (including mu)?
Phenomenology suggest the weak scale
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Why weak-scale SUSY ?
Naturalness => new TeV scale that cutts off quadratically divergent a
contributions from SM particles
predicts a light Higgs Mh< 130 GeV
as suggested by data Mh< 149 GeV @ 95%
Predicts gauge coupling unification
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Supersymmetry, part 2
Erler, 0907.0883
Why weak-scale SUSY ?
accomodates heavy top quark and provides radiative EWSB
dark matter candidate: neutralino, sneutrino, ...
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Supersymmetry, part 2
Unconstrained MSSM
No particular SUSY breaking mechanism assumed
L. Girardello, M. Grisaru ’82
No additional mass terms for chiral fermions
Relations between dimensionless couplings unchanged
Most general case: 105 new parameters
– masses, mixing angles, CP phases
 Good phenomenological description if universal breaking terms
 Scenarios for SUSY breaking
=> predictions in terms of small set of parameters
 Experimental determination of SUSY parameters => patterns of SUSY breaking
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Supersymmetry, part 2
different scenarios
mSUGRA
SPS1a
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GMSB
SPS7
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AMSB
SPS9
Higgs in the MSSM
SUSY breaking
needed to break
SU(2)xU(1)
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Higgs sector
Mh<MZ
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upper bound on light Higgs
FeynHiggs
Heinemeyer, Weiglein ’05
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Higgs couplings
to gauge bosons:
tree level; including loops change
to fermions:
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limits on Higgs from LEP
search at LEP
LHWG-Note 2005-01
exclusion limits depend on scenario
e.g. if CP violated
all h,H,A mix
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Electroweak precision tests: SM vs. MSSM
SM: MH varied
MSSM: susy parameters varied
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sfermions
Squark mixing
gauge invariance
off-diagonal terms ~ partner fermion mass => mixing important for
3rd generation sfermions
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gauginos
Higgsinos and EW gauginos mix
Mass matrices are given in terms of
=> MSSM predicts mass relations between charginos and neutralinos
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Prospects at the LHC
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Search path at the LHC
Establishing SUSY
discovery – signals for new physics, possibly SUSY?
measurements – masses, cross sections, couplings
parameter studies – MSSM Lagrangian, SUSY breaking?
Basic objects at the LHC
jets, isolated leptons and photons, displaces vertices
energies and transverse momenta
missing transverse momentum
Search strategies
inclusive
 canonical searches – jet multiplicity, isolated leptons,
large missing energy, ...
counting, identifying an excess
exclusive
 specific processes – measure energy and combinations
of invariant mass spectra
determine SUSY masses and couplings
(modulo reasonable assumptions)
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LHC: signal and background
BG from W, Z and tt:
107-109 events per 10 fb-1
SUSY signal:
103-105 events per 10 fb-1
need strong rejection ~10-4
Exploit kinematics to maximum extent:
mass reconstruction method
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Inclusive searches
Require: at least two jets with pT> Ec and ETmiss > Ec, Ec to maximise S/pB
pT >20 GeV for any lepton
M(l, ETmiss) > 100 GeV to reduce W+jets
ST > 0.2 to reduce dijet background
ATLAS TDR
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L=10 fb-1
CMS
Supersymmetry, part 2
After inclusive searches
Observe excess in inclusive ETmiss + jets, + 1 lepton, + 2 leptons, ...
•
•
•
•
•
•
ETmiss => undetectable particles in the final state
Meff + xsection => strongly interacting heavy particles
jets => colored particles
excess of SS leptons => some of them Majorana
OS-SF leptons => lepton flavor conserved
...
First glimpses of new physics emerge: global analyses show
• that physics beyond SM exisitsI
• what its mass scale is
One may even attempt to fit all these to determine the SUGRA
model parameters.
However, better to use partial reconstruction of exclusive final states
to determine precise combinations of masses from kinematic
endpoints of distributions
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Exclusive measurements
Complicated cascade
decays
Mass/GeV
Many intermediates
Typical signal
Jets
Squarks and Gluinos
Leptons
Sleptons and weak
gauginos
Missing energy
Undetected LSP
Model dependent
“typical” susy spectrum
(mSUGRA)
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ATLAS
Point 5
Start from the bottom of
the decay chain
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Exclusive measurements
Key decays are
ATLAS
Point 4
edge 68.13 +/- 1 GeV
Exploiting further pT of Z =>
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Reconstructing the LSP
Alternative method to measure masses: look at individual decays
Nojiri, Polesello and Tovey, arXiv:hep-ph/0312317
Kawagoe, Nojiri and Polesello, Phys.Rev. D71 (2005) 035008
SUSY states are quite narrow, approx. on-shell
the 4-momentum of A not measured, but:
write
Solve for i and EA
full reconstruction of the
LSP 4-momentum
and then reconstruct masses of A, B, C and D
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End of first few fb-1 of data taking
Scenario:
BIs this really SUSY?
After careful calibration …
ATLAS and CMS observe excess of events
Missing transverse energy
Leptons
Jets
Edges in invariant mass distributions
determine masses
Bor Kaluza-Klein states ?
AAre we ready to claim SUSY discovery?
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Revisit
”typical”sparticle
SUSY spectrum
Revisit
“Typical”
spectrum
Left Squarks
-> strongly interacting
-> large production
-> chiral couplings
LHC point 5
mass/GeV
20 = neutralino2
–> (mostly) partner
of SM W0
10 = neutralino1
–> Stable
-> weakly interacting
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Right slepton
(selectron or smuon)
-> Production/decay
produce lepton
-> chiral couplings
Some sparticles omitted
Supersymmetry, part 2
Revisit ”typical” SUSY spectrum
Left Squarks
-> strongly interacting
-> large production
-> chiral couplings
SUSY
mass/GeV
20 = neutralino2
–> (mostly) partner
of SM W0
Right slepton
(selectron or smuon)
-> Production/decay
produce lepton
-> chiral couplings
10 = neutralino1
–> Stable
-> weakly interacting
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What
if KK spectrum
similar?
Revisit
“Typical”
KK-particle
spectrum ?
q1
First KK-quark
-> strongly interacting
-> large production
UED
mass/GeV
First KK-Z
–> partner
of SM Z0
First KK- lepton
(electron or muon)
-> Production/decay
produce lepton
Z1
l1
First
10 KK-photon
–> Stable
-> weakly interacting
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1
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Measure spin
Barr hep-ph/0405052
SUSY/KK differ in spins in the decay chain
need sensitivity to the particle spin
eg. lepton charge asymmetries
UED
KK-like masses
SUSY
SPS1a-like masses
Smillie, Webber hep-ph/0507170
efficiency depends on sparticle masses
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Cosmological connection
• Extremely tempting to assume that EWSB and Dark Matter
.
., n characterised by the same energy scale
• Likely that new physics contains a stable particle that can be n n
, copiously produced at the LHC
There are counterexamples, but
if above true => large cross sections for jets + missing
,
energy events at the LHC
=> LHC will provide data for astrophysics
=> infer DM properties from masses and
cross sections
Relic density
WXh2 ~ 3 x 10-27 cm3s-1 / <sv>
requires typical weak interaction annihilation cross sections
How well <sv> can be predicted from LHC depends on model for NP
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WMAP and SUSY DM
bino
neutralino being a pure
• bino: NN -> fermion pairs
• higgsino: NN -> WW,ZZ
• wino: NN-> WW,ZZ
higgsino
Arkani-Hamed,
Delgado, Giudice
wino
DM models seem fine tuned
Focus point
Co-annihilation
Bino LSP
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Higgs funnel
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LCC benchmark points
American LCC + Snowmass05 benchmark points
Peskin, LCWS’06
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LCC points
The LHC will start testing cosmology
a LC in a foreseeable future would greatly help
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