SUSY 2 Jan Kalinowski. J. KalinowskiSupersymmetry, part 2 Outline Constructing the MSSM SUSY must be...

SUSY 2

Jan Kalinowski

J. Kalinowski Supersymmetry, part 2

Outline

Constructing the MSSM

SUSY must be broken

SUSY: experimrental status

Prospects for the LHC


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


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


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


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


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


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


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


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


Why weak-scale SUSY ?

accomodates heavy top quark and provides radiative EWSB

dark matter candidate: neutralino, sneutrino, ...


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


different scenarios

mSUGRA SPS1a

GMSB SPS7

AMSB SPS9


Higgs in the MSSM

SUSY breaking needed to

break SU(2)xU(1)


Higgs sector

Mh<MZ


upper bound on light Higgs

FeynHiggsHeinemeyer, Weiglein ’05


Higgs couplings

tree level; including loops change

to gauge bosons:

to fermions:


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


Electroweak precision tests: SM vs. MSSM

SM: MH variedMSSM: susy parameters varied


sfermions

Squark mixing

gauge invariance

off-diagonal terms ~ partner fermion mass => mixing important for 3rd generation sfermions


gauginos

Higgsinos and EW gauginos mix

Mass matrices are given in terms of

=> MSSM predicts mass relations between charginos and neutralinos


Prospects at the LHC


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)


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


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


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.


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


Exclusive measurements

Key decays are

Exploiting further pT of Z =>

edge 68.13 +/- 1 GeV

ATLASPoint 4


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


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?


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


Revisit ”typical” SUSY spectrum


Left Squarks-> strongly interacting-> large production-> chiral couplings

10


Right slepton(selectron or smuon)-> Production/decayproduce lepton-> chiral couplings

20 = neutralino2

–> (mostly) partnerof SM W0

10 = neutralino1


Revisit ”typical” SUSY spectrum

SUSY

mass/G

eV


First KK-quark-> strongly interacting-> large production

mass/G

eV

Revisit “Typical” KK-particle spectrum ?

10


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?


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


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


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


LCC benchmark points

American LCC + Snowmass05 benchmark points

Peskin, LCWS’06


The LHC will start testing cosmology

LCC points

a LC in a foreseeable future would greatly help

SUSY 2 Jan Kalinowski. J. KalinowskiSupersymmetry, part 2 Outline Constructing the MSSM SUSY must be...

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