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Searches for Physics Beyond the Standard Model at LEP PowerPoint Presentation

Searches for Physics Beyond the Standard Model at LEP

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Searches for Physics Beyond the Standard Model at LEP

Andre Tilquin

CPPM Marseille

- What is the Standard Model
- Why to go beyond and how
- Supersymmetry
- Higgs sector
- Exotica
- Summary

DIS2003 A.Tilquin

One principle

Gauge symmetry or local invariance

,Z0,W,g

Exact symetry

Yukawa

m=0

Broken with a Higgs SU(2) doublet

One observable H0

What is Standard ModelThree families

Three groups

DIS2003 A.Tilquin

Why to go beyond ?

The NuTeV measurement:

-ratio of neutral current to charged current reactions in neutrino-nucleon scattering.

-When interpreted as a measurement of the mass of the W boson, a 2.9 standard deviations, from the other direct constraints is found.

Why not ?

DIS2003 A.Tilquin

How to go beyond SM

- New symmetries:
- -Super Symmetry
- -New Gauge bosons

- News Higgs fields: Doublets/triplets
- New fermions
- Anomalous coupling, contact interaction
- Compositeness
- More exotica:
- Technicolor
- Extra dimensions

DIS2003 A.Tilquin

DELPHI

L3

OPAL

LEP data setPer experiments:

LEP1: L175 pb-1

LEP2: L700 pb-1

Energies:

90209 GeV

DIS2003 A.Tilquin

~ ~

h,H

~

Z

In exact SUSY no new parameters

}

~

H±

~

01-4

~

W±

}

~

g

~

~

lL,R

±1,2

=

~

L

~

q L,R

~

G

SUSY should be broken

The word of SUSY- Additional symmetry between bosons and fermions
- Associates a SUSY partner to each SM particle

New multiplicative quantum number:

h,H,A

Z0

Rp=1 for SM particle

Rp=-1 for SUSY particle

H±

W±

g

Conserve

lL,R

L

LSP stable

Pair production

G

q L,R

DIS2003 A.Tilquin

Breaking down SUSY

- Its mechanism is unknown: Many models
- SUGRA (Super Gravity)
- LSP=neutralino

- GMSB (Gauge mediated Super symmetry breaking)
- LSP=gravitino

- AMSB (Anomaly Mediated Super Symmetry breaking)
- LSP=wino-like

- SUGRA (Super Gravity)

Standard MSSM

DIS2003 A.Tilquin

All final states characterised by missing energy

Standard MSSM- Supergravity inspired minimal models with R parity
- Heavy gravitino and gluino
- Stable, neutral and weakly interacting LSP 10

- Low energy parameters:
- Higgs mixing mass term
tan() v.e.v

mA CP odd higgs mass

m1/2 Common gaugino masse at GUT scale

m0 Common sfermion mass at GUT scale

A0 Common trilinear mass at GUT scale (mixing)

Production at LEP:

DIS2003 A.Tilquin

e+

,Z*

e+

e-

e-

Slepton searches2 acoplanar leptons + missing energy

Main background from WWll

DIS2003 A.Tilquin

Squark an gluino

qL and qR are mixingq1,q2

e+

,Z*

e-

To compare with Tevatron,LEP results are translated into an exclusion limit in gluino an squark masses

DIS2003 A.Tilquin

Neutralino

Chargino, neutralino slepton and Higgs results are combined.

LSP mass limit obtained at high tan()

DIS2003 A.Tilquin

e+

Observed limit in the mhmax scenario:

mh>91.0 GeV (94.6)

mA>91.9 GeV (95.0)

,Z*

e-

e+

,Z*

e-

MSSM Higgs- Two Higgs doublets:
- 5 physical states:
- h,H,A and H
- Two free parameters at tree level: mA,tan=v2/v1
- Searches by combining two complementary processes

Dominant at low tan()

Dominant at high tan()

DIS2003 A.Tilquin

=SM

Br(h hadrons) = 100%

mh>112.9 GeV/c2

Flavor independent Higgs search- Some extension of standard model:
- Two Higgs doublet (type II models), the mixing angle in the CP-even Higgs sector is a free parameters
- standard decay hbb or could be suppressed w.r.t hcc or gg
- Searches for hadronic decay without b tagging.

DIS2003 A.Tilquin

e+

,Z*

e-

mH>78.6 GeV/c2

Charged HiggsPredicted by 2 HDM models.

Decays:H/cs

B(H) free parameter

Main background WW

DIS2003 A.Tilquin

For =SM and B(hInv.)=100%

Mh>114.4 GeV/c2

Invisible Higgs- Predicted in different models:
- In MSSM:
- h00

- Majoron
- hJJ

- Cross section can be different from standard model.
- Search for acoplanar jets and leptons from Z decay

DIS2003 A.Tilquin

Fermiophobic:

mh>109.7 GeV/c2

h

W(*)

Fermiophobic Higgs:h- In some models:
- Type I 2HDM

- No couplings to fermions. Coupling to photons through W loop:
- Anomalous couplings

DIS2003 A.Tilquin

OPAL: mH>98.5 GeV/c2

Double charged HiggsPredicted by LR super symmetric model (Higgs triplet):

Decay in two charged leptons, mainly in tau’s. Yukawa coupling to lepton is free parameter.

h>10-7 : look for 4 ’s close to interaction point

h<10-7 : search for kick of charged tracks

h<10-8 : search for anomalous ionisation

DIS2003 A.Tilquin

W

,q

e+

t

b

e-

Anomalous top quark coupling SM10-9fbSingle top production at LEP (FCNC)

R-parity violation

kZ ,kg

Delphi

DIS2003 A.Tilquin

f/

,Z,W,g

e+

e*

e-

Excited fermionsIn composite models, fermion & boson are composite with and associated energy scale .

gauge group weights factor

Lot of decay channel at LEP:

From differencial x-section

DIS2003 A.Tilquin

e+

,Z

LQ

LQ

e-

I3

OPAL Preliminary

OPAL

e+

LQ

e-

Lepto-quark- Very similar to excited leptons:
- New color triplets bosonic fields mediating interaction between quark and leptons (LQ)

DIS2003 A.Tilquin

L+(N)

e+

,Z

e-

L-(N)

l,L(stable)/l+

L±/N

f

W*

Heavy Leptons- One way to explain the mass in the see-saw mechanism
- New heavy leptons with

DIS2003 A.Tilquin

e+

e+

e-

e-

TechnicolorAlternative mechanism of Electro-weak Symmetry Breaking:

- Breaking of global chiral symmetry of technifermions generates Golstone boson used for longitudinal polarisation of massive W and Z bosons.
- Techniquark condensate replace non zero VEV of Higgs field
- Need a large number of technidoublets (ND=9)

- Vector states r0T, w0T p+T p-T or g p0T
- Technipions couple to quarks and leptons µmass

DIS2003 A.Tilquin

Planck mass

Planck mass in ED

Radius of extra dimensions

Extra dimensions- Trying to solve the hierarchy problem:
- Weakness of Gravity at electroweak scale

- Our word confined to four dimensions
- Gravity propagates in extra dimensions (ADD)

By choosingMDEWNo hierarchy problem

Small but large number of states (GKK)

1/MPl

f,V

d=1 R=1013 m Excluded

d=2 R=1 mm

d=3 R=1 nm

….

d=7 R=1 fm Max in M-theory

G

f,V

DIS2003 A.Tilquin

MD>1.36 TeV

Extra dimensions (cont)Direct search: missing energy

LEP average:

MS>1.2 TeV (=+1)

MS>1.09TeV (=-1)

Indirect: look for deviation from (d/d)SM

DIS2003 A.Tilquin

Conclusions

Lot of searches performed by the 4 LEP experiments

SUSY: No evidence at LEP and CMSSM fully covered

Chargino: m>94 GeV

Neutralino: m>45 GeV

Sparticles:m>100 GeV

Higgs sector: No evidence of non standard Higgs

mHiggs 100 GeV/c2

Exotica:

New particles: m>100 GeV/c2

New scales > 1 TeV

New coupling < 10% SM couplings

No deviation from standard model, and no evidence of new physics.

Hope that something will happened at LHC

DIS2003 A.Tilquin

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