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SUSY 2
Jan Kalinowski
J. Kalinowski Supersymmetry, part 2
Outline
Constructing the MSSM
SUSY must be broken
SUSY: experimrental status
Prospects for the LHC
J. Kalinowski Supersymmetry, part 2
Extended higgs sector(2 doublets)
MSSM: particles and sparticles
SM SUSY
quarks (L&R)leptons (L&R) neutrinos (L&?)
squarks (L&R)sleptons (L&R)sneutrinos (L&?)
gluon Z0
W±
BW0
h0
H0
A0
H±
4 x neutralino
2 x chargino
AfterMixing
Spin-1/2
Spin-1
Spin-0
Spin-0
gluin
o
Bino
Wino0
Wino±
Spin-1/2
~
~2
H0
H0
H±
~1
J. Kalinowski Supersymmetry, part 2
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 conservedConsequences:
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
J. Kalinowski Supersymmetry, part 2
Exact SUSY
SUSY must be broken
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
Exact SUSY => no new parameters
J. Kalinowski Supersymmetry, part 2
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 superfieldnot possible within the MSSM
D-term breaking via a
does not work in the MSSM since gives charge and color-breaking minima
SUSY must be broken
J. Kalinowski Supersymmetry, part 2
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”
Other problems with spontaneous susy breaking
SUSY must be broken
J. Kalinowski Supersymmetry, part 2
SUSY must be broken
Invoke a hidden sector where SUSY breaking occurs
Hidden sector MSSM sectorFlavour blind
mediators
In the hidden sector the F and/or D terms of some non-MSSM develop VEV
phenomenology depends mainly on mechanism for communicating SUSYbreaking rather than on SUSY-breaking mechanism itself
J. Kalinowski Supersymmetry, part 2
Unconstrained MSSM
No particular SUSY breaking mechanism assumed
No additional mass terms for chiral fermions
Relations between dimensionless couplings unchanged
Most general case: 105 new parameters
L. Girardello, M. Grisaru ’82
Question: what is the scale of SUSY breaking parameters (including mu)?
Phenomenology suggest the weak scale
J. Kalinowski Supersymmetry, part 2
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%
Erler, 0907.0883 Predicts gauge coupling unification
J. Kalinowski Supersymmetry, part 2
Why weak-scale SUSY ?
accomodates heavy top quark and provides radiative EWSB
dark matter candidate: neutralino, sneutrino, ...
J. Kalinowski Supersymmetry, part 2
Unconstrained MSSM
No particular SUSY breaking mechanism assumed
No additional mass terms for chiral fermions
Relations between dimensionless couplings unchanged
Most general case: 105 new parameters
L. Girardello, M. Grisaru ’82
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
– masses, mixing angles, CP phases
J. Kalinowski Supersymmetry, part 2
different scenarios
mSUGRA SPS1a
GMSB SPS7
AMSB SPS9
J. Kalinowski Supersymmetry, part 2
Higgs in the MSSM
SUSY breaking needed to
break SU(2)xU(1)
J. Kalinowski Supersymmetry, part 2
Higgs sector
Mh<MZ
J. Kalinowski Supersymmetry, part 2
upper bound on light Higgs
FeynHiggsHeinemeyer, Weiglein ’05
J. Kalinowski Supersymmetry, part 2
Higgs couplings
tree level; including loops change
to gauge bosons:
to fermions:
J. Kalinowski Supersymmetry, part 2
limits on Higgs from LEP
search at LEP
exclusion limits depend on scenario
e.g. if CP violatedall h,H,A mix
LHWG-Note 2005-01
J. Kalinowski Supersymmetry, part 2
Electroweak precision tests: SM vs. MSSM
SM: MH variedMSSM: susy parameters varied
J. Kalinowski Supersymmetry, part 2
sfermions
Squark mixing
gauge invariance
off-diagonal terms ~ partner fermion mass => mixing important for 3rd generation sfermions
J. Kalinowski Supersymmetry, part 2
gauginos
Higgsinos and EW gauginos mix
Mass matrices are given in terms of
=> MSSM predicts mass relations between charginos and neutralinos
J. Kalinowski Supersymmetry, part 2
Prospects at the LHC
J. Kalinowski Supersymmetry, part 2
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)
J. Kalinowski Supersymmetry, part 2
LHC: signal and background
SUSY signal: 103-105 events per 10 fb-1
BG from W, Z and tt: 107-109 events per 10 fb-1
Exploit kinematics to maximum extent: mass reconstruction method
need strong rejection ~10-4
J. Kalinowski Supersymmetry, part 2
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, ET
miss) > 100 GeV to reduce W+jets ST > 0.2 to reduce dijet background
ATLAS TDR L=10 fb-1 CMS
J. Kalinowski 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
However, better to use partial reconstruction of exclusive final states to determine precise combinations of masses from kinematic endpoints of distributions
One may even attempt to fit all these to determine the SUGRA model parameters.
J. Kalinowski Supersymmetry, part 2
Exclusive measurements
“typical” susy spectrum(mSUGRA)
Mass/GeV
ATLASPoint 5
Complicated cascade decays
Many intermediatesTypical signal
JetsSquarks and Gluinos
LeptonsSleptons and weak gauginos
Missing energyUndetected LSP
Model dependent
Start from the bottom of the decay chain
J. Kalinowski Supersymmetry, part 2
Exclusive measurements
Key decays are
Exploiting further pT of Z =>
edge 68.13 +/- 1 GeV
ATLASPoint 4
J. Kalinowski Supersymmetry, part 2
Reconstructing the LSP
Alternative method to measure masses: look at individual decaysNojiri, Polesello and Tovey, arXiv:hep-ph/0312317Kawagoe, Nojiri and Polesello, Phys.Rev. D71 (2005) 035008
SUSY states are quite narrow, approx. on-shell
the 4-momentum of A not measured, but:
and then reconstruct masses of A, B, C and D
write
Solve for i and EA
full reconstruction of the LSP 4-momentum
J. Kalinowski Supersymmetry, part 2
End of first few fb-1 of data taking
After careful calibration …
ATLAS and CMS observe excess of events
Missing transverse energyLeptonsJetsEdges in invariant mass distributions
determine masses
Scenario:BIs this really SUSY?
Bor Kaluza-Klein states ?
AAre we ready to claim SUSY discovery?
J. Kalinowski Supersymmetry, part 2
mass/G
eV
Some sparticles omitted
LHC point 5
Revisit “Typical” sparticle spectrum
Left Squarks-> strongly interacting-> large production-> chiral couplings
10
–> Stable-> weakly interacting
Right slepton(selectron or smuon)-> Production/decayproduce lepton-> chiral couplings
20 = neutralino2
–> (mostly) partnerof SM W0
10 = neutralino1
–> Stable-> weakly interacting
Revisit ”typical” SUSY spectrum
J. Kalinowski Supersymmetry, part 2
Left Squarks-> strongly interacting-> large production-> chiral couplings
10
–> Stable-> weakly interacting
Right slepton(selectron or smuon)-> Production/decayproduce lepton-> chiral couplings
20 = neutralino2
–> (mostly) partnerof SM W0
10 = neutralino1
–> Stable-> weakly interacting
Revisit ”typical” SUSY spectrum
SUSY
mass/G
eV
J. Kalinowski Supersymmetry, part 2
First KK-quark-> strongly interacting-> large production
mass/G
eV
Revisit “Typical” KK-particle spectrum ?
10
–> Stable-> weakly interacting
First KK- lepton(electron or muon)-> Production/decayproduce lepton
UED
First KK-photon–> Stable-> weakly interacting
q1
Z1
l1
First KK-Z–> partnerof SM Z0
1
What if KK spectrum similar?
J. Kalinowski Supersymmetry, part 2
Measure spin
SUSY/KK differ in spins in the decay chain need sensitivity to the particle spin
KK-like masses SPS1a-like masses
UED SUSY
Smillie, Webber hep-ph/0507170efficiency depends on sparticle masses
eg. lepton charge asymmetries
Barr hep-ph/0405052
J. Kalinowski Supersymmetry, part 2
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 Xh2 ~ 3 x 10-27 cm3s-1 / <v> requires typical weak interaction annihilation cross sections How well <v> can be predicted from LHC depends on model for NP
J. Kalinowski Supersymmetry, part 2
WMAP and SUSY DM
Co-annihilation
Bino LSP
Focus point
Higgs funnel
neutralino being a pure• bino: NN -> fermion pairs• higgsino: NN -> WW,ZZ• wino: NN-> WW,ZZ
Arkani-Hamed,Delgado, Giudice
DM models seem fine tuned
binohiggsino
wino
J. Kalinowski Supersymmetry, part 2
LCC benchmark points
American LCC + Snowmass05 benchmark points
Peskin, LCWS’06
J. Kalinowski Supersymmetry, part 2
The LHC will start testing cosmology
LCC points
a LC in a foreseeable future would greatly help