Z

χ01

χ02

Decay in two bodies

3 bodies decays

Many leptons in the final states + missing transverse energy (fromLSP)

Mass eigenstates (4 neutralinos), combinations of photinos, higgsinos e Zinos

We can have 2 or 3 body decays

Final states from Z + Missing transverse energy

Neutralinos decays

χ± W±

χ01

Many leptons and jets in the final states + missing transverse energy (from LSP)

Charginos are a combination of Winos and Higgsinos

From the way the combination is done, it depends whether the chargino decays in sleptons or neutralinos.se decade in sleptoni o neutralino.

Eg: More Higgsino:

Final states from the W + missEt from LSP

Charginos decays

χ01

Z

χ02

f f~

Many leptons and jets in the final states + missing transverse energy (from LSP)

Final states from Z + quark or lepton + missing transverse energy

Leptons and squarks decays

Phenomenology

gluinos/squarks decay into

high PT jets Decay chains Jets emission Leptons from charginos /

neutralinos   LSP stable and neutral: huge

missing ET,

Golden channel for discovery: “multi-Jets + n-leptons + ET

miss”

Search strategy at LHC

5

Background to SUSY signal

6

  ≥ 2 high pt b jets

  ≥ 2 high pt isolated leptons

(leptons = e,µ)

  missing Et

g~ pp →

b~02χ

~

±

SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets

Squarks and gluinos reconstruction:

p

p

g~

b~

b

b

±

01~χ

02~χ

±~

bb~→

±→ 01~χ

Cascade decays

Neutralinos / charginos search at Tevatron

Squarks and sgluinos search at Tevatron

Phenomenology of the Higgs in the MSSM

Standard Model MSSM

•  1 Higgs doublet(v) •  1 final state H •  1 parameter MH •  radiative corrections quadratically divergent

•  2 Higgs doublets (v1 ,v2) •  5 final states h H A H+ , H-

charged •  2 needed parameters Mh tanβ=v2/v1 •  radiative corrections finite but depending from mtop, msusys At Ab µ

Prohibited From theory

Mh ~ MA

Higgs sector in the MSSM

At three level, all the Higgs masses are determined by two parameters: mA, tan β

2220 ±± += WAH mmm

( )β2cos4)( 22222222212

, 00000000 AZZAZAHh mmmmmmm −++=

mass of the neutral pseudoscalar

Ratio between v and v: <v>/<v’>

The radiative corrections modify this prediction . However..

Higgs masses in the MSSM

11

In the MSSM, there must be at least a light Higgs, h0 (mh0 ≤ 130 GeV for any value of mA, tan β):

H

f

• 

•  H f

Higgs couples to fermions

βα

sincos

0 ttth mg ∝

βα

sinsin

0 tttH mg ∝

• 

• 

_

βcot0 tttA mg ∝

• 

• 

βα

cossin

0

−∝ bbbh mg

βα

coscos

0 bbbH mg ∝

• 

•  βtan0 bbbA mg ∝

•  proportional to the mass→ 3rd generations favoured

•  tan β favours the coupling with down-type fermions

Coupling constants mixing stop-sbottom

Sezioni d’urto

Le sezioni d’urto dipendono drasticamente da tan β:

Limits from LEP extracted in the planes (MA,Mh) e (Mh tanβ)

Limits expressed at 95% CL: MA > 84 GeV/c2 Mh > 85 GeV/c2 Values 0.7 <tanβ<1.8 are excluded

To extend the exclusion region one needs a center of mass energy of 210-215 GeV

LHC

Z*

h

A e+

e-

Neutral higgs

MSSM @ LHC

The decays in τ play a critical role:

•  ττ → jet + jet •  ττ → lepton + jet •  ττ → lepton + lepton

The parameters space coverage is much better than at LEP

h0,A0,H0 → ττ

τ branching ratios: τ → l νl ντ : 35% τ → π± + n π0’s : 50% τ → 3π± + n π0’s : 15%

References

  Haber, Howard E. and Kane, Gordon L., Is Nature Supersymmetric?

  Schwarz, John H., String Theory, Supersymmetry, Unification, and All That, Reviews of Modern Physics, Vol. 71, No. 2, The American Physical Society, 1999

  Tata, Xerxes, What is Supersymmetry and How Do We Find It?, 1997

  Wagner, Carlos, SUSY Lectures I & II, Fermilab, June 2005 (http://www-cdf.fnal.gov/physics/lectures/)

  Supersymmetry, Wikipedia