Supersymmetry at the LHC - Heidelberg University · Supersymmetry at the LHC Georg Weiglein IPPP Durham Heidelberg, 08/2007 Introduction Properties of SUSY theories What is the scale

Supersymmetry at the LHC

Georg Weiglein

IPPP Durham

Heidelberg, 08/2007

Introduction

Properties of SUSY theories

What is the scale of Supersymmetry?

SUSY Higgs physics at the LHC

SUSY processes at the LHC

Conclusions

Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.1

Introduction

The LHC will open up the new territory of TeV-scale physicsWhat can we learn from exploring the TeV scale?


Introduction

The LHC will open up the new territory of TeV-scale physicsWhat can we learn from exploring the TeV scale?

How do elementary particles obtain the property of mass:what is the mechanism of EWSB?

Do all the forces of nature arise from a single fundamentalinteraction?

Are there more than three dimensions of space?

Are space and time embedded into a “superspace”?

Can dark matter be produced in the laboratory?

. . .Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.2

What is the mechanism of electroweaksymmetry breaking ?

[see R. Barbieri’s talk]

Standard Model (SM), SUSY, . . . :Higgs mechanism, elementary scalar particle(s)

Strong electroweak symmetry breaking (technicolour, . . . ):

new strong interaction, non-perturbative effects,resonances, . . .

Higgsless models in extra dimensions: boundaryconditions for SM gauge bosons and fermions on Planckand TeV branes in higher-dimensional space

⇒ New phenomena required at the TeV scaleSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.3

The Standard Model cannot be the ultimate theory

The Standard Model does not include gravity

⇒ breaks down at the latest at MPlanck ≈ 1019 GeV





“Hierarchy problem”: MPlanck/Mweak ≈ 1017

How can two so different scales coexist in nature?







Via quantum effects: physics at Mweak is affected byphysics at MPlanck

⇒ Instability of Mweak

⇒Would expect that all physics is driven up to thePlanck scale







Via quantum effects: physics at Mweak is affected byphysics at MPlanck

⇒ Instability of Mweak

⇒Would expect that all physics is driven up to thePlanck scale

Nature has found a way to prevent thisThe Standard Model provides no explanation


Hierarchy problem: how can the Planck scale beso much larger than the weak scale ?

⇒ Expect new physics to stabilise the hierarchy




Supersymmetry:Large corrections cancel out because of symmetryfermions ⇔ bosons




Supersymmetry:Large corrections cancel out because of symmetryfermions ⇔ bosons

Extra dimensions of space:Fundamental Planck scale is ∼ TeV (large extra dimensions),hierarchy of scales is related to a “warp factor”(“Randall–Sundrum” scenarios)


Properties of SUSY theories

Supersymmetry: fermion ←→ boson symmetry,leads to compensation of large quantum corrections


The Minimal Supersymmetric Standard Model(MSSM)

Superpartners for Standard Model particles:[u, d, c, s, t, b

]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 1

2

[u, d, c, s, t, b

]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 0

g W±, H±

︸︷︷︸γ, Z,H0

1 , H02

︸︷︷︸Spin 1 / Spin 0

g χ±1,2 χ0

1,2,3,4 Spin1

2




]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 1

2

[u, d, c, s, t, b

]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 0

g W±, H±

︸︷︷︸γ, Z,H0

1 , H02


g χ±1,2 χ0

1,2,3,4 Spin1

2

Two Higgs doublets, physical states: h0, H0, A0, H±




]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 1

2

[u, d, c, s, t, b

]

L,R

[e, µ, τ

]

L,R

[νe,µ,τ

]

LSpin 0

g W±, H±

︸︷︷︸γ, Z,H0

1 , H02


g χ±1,2 χ0

1,2,3,4 Spin1

2

Two Higgs doublets, physical states: h0, H0, A0, H±

General parametrisation of possible SUSY-breaking terms⇒ free parameters, no prediction for SUSY mass scale

Hierarchy problem ⇒ expect observable effects at TeV scaleSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.7

Supersymmetry (SUSY)

SUSY: unique possibility to connect space–time symmetry(Lorentz invariance) with internal symmetries (gaugeinvariance):

Unique extension of the Poincaré group of symmetries ofD = 4 relativistic quantum field theories





Local SUSY includes gravity, called “supergravity”






Lightest superpartner (LSP) is stable if “R parity” is conserved⇒ Candidate for cold dark matter in the Universe






Lightest superpartner (LSP) is stable if “R parity” is conserved⇒ Candidate for cold dark matter in the Universe

Gauge coupling unification, MGUT ∼ 1016 GeV

neutrino masses: see-saw scale ∼ .01–.1MGUTSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.8

SUSY breaking

MSSM: no particular SUSY breaking mechanism assumed,parametrisation of possible soft SUSY-breaking terms

⇒ relations between dimensionless couplings unchanged

⇒ cancellation of large quantum corrections preserved

Most general case: 105 new parameters


SUSY breaking

MSSM: no particular SUSY breaking mechanism assumed,parametrisation of possible soft SUSY-breaking terms

⇒ relations between dimensionless couplings unchanged

⇒ cancellation of large quantum corrections preserved

Most general case: 105 new parameters

Strong phenomenological constraints on flavour off-diagonalSUSY-breaking terms

⇒ Good phenomenological description for universalSUSY-breaking terms (≈ diagonal in flavour space)


Simplest ansatz: the CMSSM

Assume universality at high energy scale (MGUT, MPl, . . . )

Universal scalar masses: m2 = m20

Universal gaugino masses: Mi = m1/2 (“GUT relation”)

Universality of soft-breaking trilinear terms:

Ltri = A0(HUQyuu + HDQydd + HDLyle)

yu, yd, . . . are the same matrices that appear in Yukawacouplings (“proportionality”)


Radiative electroweak symmetry breaking

[see W. Bernreuther’s talk]Universal boundary conditions at GUT scale,renormalisation group running down to weak scale

q~

l~

H

H

g~

W~

B~

large corrections fromtop-quark Yukawacoupling

⇒ m2Hu

driven tonegative values

⇒ ew symmetrybreaking

emerges naturally atscale ∼ 102 GeV for100 GeV <

∼ mt<∼ 200 GeV


The Constrained MSSM (CMSSM)

Universality ansatz results in five parameters, if possiblephases are ignored:

m20, m1/2, A0, b, µ

Require correct value of MZ

⇒ |µ|, b given in terms of tan β ≡ vu/vd, sign µ

⇒ CMSSM characterised by

m20, m1/2, A0, tanβ, sign µ


SUSY-breaking scenarios

“Hidden sector”: −→ Visible sector:

SUSY breaking MSSM

“Gravity-mediated”: SUGRA“Gauge-mediated”: GMSB

“Anomaly-mediated”: AMSB“Gaugino-mediated”

. . .

SUGRA: mediating interactions are gravitational

GMSB: mediating interactions are ordinary electroweak andQCD gauge interactions

AMSB, Gaugino-mediation: SUSY breaking happens on adifferent brane in a higher-dimensional theory


SUGRA / CMSSM phenomenology

SUGRA with universality assumptions ⇒ CMSSMm0, m1/2, A0: GUT scale parameters

⇒ Spectra from renormalisation group running to weak scale

Lightest SUSY particle (LSP)is usually lightest neutralino

Gaugino masses run in sameway as gauge couplings⇒ gluino heavier than

charginos, neutralinos

“Typical” CMSSM scenario(SPS 1a benchmark scen.):

0

100

200

300

400

500

600

700

800

m [GeV]

lR

lLνl

τ1

τ2

χ0

1

χ0

2

χ0

3

χ0

4

χ±

1

χ±

2

uL, dRuR, dL

g

t1

t2

b1

b2

h0

H0, A0 H±


GMSB phenomenology

Gaugino and scalar masses arise from loop contributionsinvolving messenger fields

⇒ Typical mass hierarchy in GMSB scenario between stronglyinteracting and weakly interacting particles ∼ α3/α2/α1

LSP is always the gravitino(also possible in mSUGRA)

next-to-lightest SUSY particle(NLSP): χ0

1 or τ1

can decay into LSP inside oroutside the detector

GMSB scenario with τ NLSP(SPS 7 benchmark scen.):

0

100

200

300

400

500

600

700

800

900

1000

m [GeV]

lR

lL νl

τ1

τ2

χ0

1

χ0

2

χ0

3

χ0

4

χ±

1

χ±

2

qR

qL

g

t1

t2

b1

b2

h0

H0, A0 H±


Meta-stable vacua

Suppose we live in a SUSY-breaking meta-stable vacuum,while the global minimum has exact SUSY

Recent developments: meta-stable vacua arise as genericfeature of SUSY QCD with massive flavoursMeta-stable SUSY-breaking vacua are “generic” in localSUSY / string theory, can have cosmologically long life times[Intriligator, Seiberg, Shih ’07, . . . ]

⇒ Large activity in model buildingSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.16

Summary on SUSY-breaking scenarios

We have no “Standard Model of SUSY breaking”

There are many possibilities

⇒We have to be prepared for a wide range of possibleSUSY phenomenology


Generic features of SUSY theoriesMost general gauge-invariant and renormalizable superpotentialwith chiral superfields of the MSSM:

V = VMSSM +1

2λijkLiLjEk + λ′ijkLiQjDk + µ′iLiHu

︸︷︷︸

+1

2λ′′ijkUiDjDk

︸︷︷︸

violate lepton number violates baryon number

If both lepton and baryon number are violated

⇒ rapid proton decay

Minimal choice (MSSM) contains only terms in the Lagrangian witheven number of SUSY particles⇒ additional symmetry: “R parity”

⇒ all SM particles have even R parity, all SUSY particles have oddR parity


Phenomenological consequences ofR parity conservation

SUSY particles can only be pair-produced, e.g. gg → gg

Decay of SUSY particles into SM particles + odd number ofSUSY particles⇒ Lightest SUSY particle (LSP) is stable

All SUSY particles will eventually decay into LSP

⇒ Decay cascades of heavy SUSY particles

LSP stable⇒ some LSP must have survived from Big Bang

⇒Weakly interacting massive particle (“WIMP”)(otherwise ruled out from bounds on exotic isotopes etc.)

⇒ Candidate for cold dark matter in the Universe

LSP neutral, uncoloured⇒ leaves no traces in colliderdetectors⇒ Typical SUSY signatures: “missing energy”


Relations between SUSY parameters

Symmetry properties of MSSM Lagrangian (SUSY, gaugeinvariance) give rise to coupling and mass relations

Soft SUSY breaking does not affect SUSY relations betweendimensionless couplings

E.g.:gauge boson–fermion coupling

=

gaugino–fermion–sfermion coupling

for U(1), SU(2), SU(3) gauge groups


Squark and slepton mixing

Mt =

(

M2tL

+ m2t + M2

Zc2β(T 3t −Qts

2W

) mtX∗q

mtXq M2tR

+ m2t + M2

Zc2βQts2W

)

⇒ mt1,mt2

, θt

Mb =

(

M2bL

+ m2b + M2

Zc2β(T 3b −Qbs

2W

) mbX∗q

mbXq M2bR

+ m2b + M2

Zc2βQbs2W

)

⇒ mb1

,mb2

, θb

with Xq = Aq − µ∗κ, κ = cot β, tan β for q = t, b, tan β ≡ vu/vd

Off-diagonal element is prop. to mass of partner quark

⇒ mixing important in t sector, for large tan β also in b, τ sect.Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.21

Squark and slepton mixing

Mt =

(

M2tL

+ m2t + M2

Zc2β(T 3t −Qts

2W

) mtX∗q

mtXq M2tR

+ m2t + M2

Zc2βQts2W

)

⇒ mt1,mt2

, θt

Mb =

(

M2bL

+ m2b + M2

Zc2β(T 3b −Qbs

2W

) mbX∗q

mbXq M2bR

+ m2b + M2

Zc2βQbs2W

)

⇒ mb1

,mb2

, θb

with Xq = Aq − µ∗κ, κ = cot β, tan β for q = t, b, tan β ≡ vu/vd

Gauge invariance ⇒ MtL= MbL

⇒ relation between mt1,mt2

, θt,mb1,m

b2, θ

bSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.22

Mass relations in the MSSM

SM: all masses are free input parameters (except MW-MZ rel.)

MSSM:

Sfermion mass relations, e.g.

m2eL

= m2νL−M2

W cos(2β)

Relations between neutralino and chargino masses

Upper bound on mass of lightest CP-even Higgs boson


Mass relations in the MSSM

SM: all masses are free input parameters (except MW-MZ rel.)

MSSM:

Sfermion mass relations, e.g.

m2eL

= m2νL−M2

W cos(2β)

Relations between neutralino and chargino masses

Upper bound on mass of lightest CP-even Higgs boson

All relations receive corrections from loop effects⇔ effects of soft SUSY breaking, ew symmetry breaking

⇒ Experimental verification of parameter relations is a crucialtest of SUSY!


The Higgs sector of the MSSM

‘Simplest’ extension of the minimal Higgs sector:

Minimal Supersymmetric Standard Model (MSSM)

Two doublets to give masses to up-type and down-typefermions (extra symmetry forbids to use same doublet forboth)

Supersymmetry imposes relations between theparameters


The Higgs sector of the MSSM

‘Simplest’ extension of the minimal Higgs sector:

Minimal Supersymmetric Standard Model (MSSM)

Two doublets to give masses to up-type and down-typefermions (extra symmetry forbids to use same doublet forboth)

Supersymmetry imposes relations between theparameters

⇒ Two parameters instead of one:

tan β ≡vu

vd, MA (or MH±)


Higgs potential of the MSSM

MSSM Higgs potential contains two Higgs doublets:

V = m21H1H1 + m2

2H2H2 −m212(ǫabH

a1Hb

2 + h.c.)

+g′2 + g2

8︸︷︷︸

(H1H1 −H2H2)2 +

g2

2︸︷︷︸

|H1H2|2

gauge couplings, in contrast to SM

Five physical states: h0, H0, A0, H±

Input parameters: tanβ ≡ v2

v1, MA

⇒Mh, MH, mixing angle α, MH±: derived quantities


Higgs mass bound in the MSSM:

⇒ Prediction for Mh, MH, . . .

Tree-level result for Mh, MH:

M 2H,h =

1

2

[

M 2A + M 2

Z ±√

(M 2A + M 2

Z)2 − 4M 2ZM 2

A cos2 2β

]

⇒Mh ≤MZ at tree levelMSSM tree-level bound (gauge sector): excluded by LEP!

Large radiative corrections (Yukawa sector, . . . ):

Yukawa couplings: e mt

2MWsW, e m2

t

MWsW, . . .

⇒ Dominant one-loop corrections: Gµm4t ln(

mt1mt2

m2t

)

, O(100%) !Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.26

Higgs mass bound in the MSSM:

Present status of Mh prediction in the MSSM:

Complete one-loop + “almost complete” two-loop result available

Upper bound on Mh (FeynHiggs):[S. Heinemeyer, W. Hollik, G. W. ’99], [M. Frank, S. Heinemeyer, W. Hollik,

G. W. ’02] [G. Degrassi, S. Heinemeyer, W. Hollik, P. Slavich, G. W. ’02]

Mh<∼ 135 GeV

Extensions of the MSSM: Mh<∼ 200 GeV (if couplings stay

perturbative up to high scale)

⇒ SUSY requires a light Higgs boson

Definite and robust prediction, testable at LHC and ILCSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.27

SUSY searches at the LHC

Dominated by production of coloured superpartners:gluino, squarks

Very large mass reach in the searches forjets + missing energy⇒ gluino, squarks accessible up to 2–3 TeV

⇒ very good prospects for discovering SUSY particles iflow-energy SUSY is realised in nature

Access to uncoloured superpartners (usually lighter thancoloured ones) mainly via cascade decays of squarks, gluino


SUSY production cross sections at the LHC

10-2

10-1

1

10

10 2

10 3

100 150 200 250 300 350 400 450 500

χ2oχ1

+

t1t−1

qq−

gg

νν−

χ2og

χ2oq

NLOLO

√S = 14 TeV

m [GeV]

σtot[pb]: pp → gg, qq−, t1t

−1, χ2

oχ1+, νν

−, χ2

og, χ2oq

Prospino2 (T Plehn)

Squark and gluino couplings ∼ αs

Cross sections mainly determined by mq,g, small residualmodel dependenceσ ≈ 50 pb for mq,g = 500 GeV, σ ≈ 1 pb for mq,g = 1 TeV


LHC discovery reach in m0–m1/2 plane of theCMSSM for jets + miss. energy, 1 fb−1 and 10 fb−1

[CMS ’06]

⇒ Large coverage even with 1 fb−1 of understood data[see G. Polesello’s talk] Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.30


Electroweak precision physics ⇔ sensitivity to loop effects



Electroweak precision physics ⇔ sensitivity to loop effects

Example: indirect constraints on MH in the SM[LEPEWWG ’07]

0

1

2

3

4

5

6

10030 300

mH [GeV]

∆χ2

Excluded Preliminary

∆αhad =∆α(5)

0.02758±0.00035

0.02749±0.00012

incl. low Q2 data

Theory uncertainty

mLimit = 144 GeV

⇒ Tension between indirect bounds on MH in the SM anddirect search limit has increased


Prediction for MW (parameter scan): SM vs. MSSM

Prediction for MW in the SM and the MSSM:

160 165 170 175 180 185mt [GeV]

80.20

80.30

80.40

80.50

80.60

80.70

MW

[GeV

]

SM

MSSM

MH = 114 GeV

MH = 400 GeV

light SUSY

heavy SUSY

SMMSSM

both models

Heinemeyer, Hollik, Stockinger, Weber, Weiglein ’07

[S. Heinemeyer, W. Hollik,A.M. Weber, G. W. ’07]

MSSM: SUSYparameters varied

SM: MH varied




160 165 170 175 180 185mt [GeV]

80.20

80.30

80.40

80.50

80.60

80.70

MW

[GeV

]

SM

MSSM

MH = 114 GeV

MH = 400 GeV

light SUSY

heavy SUSY

SMMSSM

both models


experimental errors 68% CL:

LEP2/Tevatron (today)

[S. Heinemeyer, W. Hollik,A.M. Weber, G. W. ’07]


SM: MH varied

⇒ Slight preference for MSSM over SMSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.33



160 165 170 175 180 185mt [GeV]

80.20

80.30

80.40

80.50

80.60

80.70

MW

[GeV

]

SM

MSSM

MH = 114 GeV

MH = 400 GeV

light SUSY

heavy SUSY

SMMSSM

both models


experimental errors 68% CL:

LEP2/Tevatron (today)

Tevatron/LHC

ILC/GigaZ [S. Heinemeyer, W. Hollik,A.M. Weber, G. W. ’07]


SM: MH varied

⇒ Slight preference for MSSM over SMSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.34

Sensitivity to the scale of Supersymmetry

CMSSM with restrictions from dark matter relic density: m1/2,m0, A0 (GUT scale), tan β, sign(µ) (weak scale)

⇒ Low-energy spectrum from renormalisation group running

Cold dark matter (CDM) density (WMAP, . . . ):0.094 < ΩCDM h2 < 0.129

⇒ Constraints on SUSY parameter space

⇒ χ2 fit in the CMSSM with dark matter constraintsElectroweak precision observables (EWPO):MW, sin2 θeff , ΓZ, (g − 2)µ, Mh

B-physics observables (BPO):BR(b→ sγ), BR(Bs → µ+µ−), BR(Bu → τντ ), ∆MBs


χ2 fit in the CMSSM, EWPO + BPO: MW, sin2 θeff , ΓZ, (g − 2)µ,

Mh, BR(b→ sγ), BR(Bs → µ+µ−), BR(Bu → τντ ), ∆MBs

[J. Ellis, S. Heinemeyer, K. Olive, A. Weber, G. W. ’07]

tan β = 10: tan β = 50:

0 200 400 600 800 1000m1/2 [GeV]

0

2

4

6

8

10

12

14

χ2 (to

day)

CMSSM, µ > 0, mt = 171.4 GeV

tanβ = 10, A0 = 0

tanβ = 10, A0 = +m1/2

tanβ = 10, A0 = -m1/2

tanβ = 10, A0 = +2 m1/2

tanβ = 10, A0 = -2 m1/2

0 200 400 600 800 1000 1200 1400 1600 1800 2000m1/2 [GeV]

0

2

4

6

8

10

12

14

χ2 (to

day)

CMSSM, µ > 0, mt = 171.4 GeV

tanβ = 50, A0 = 0

tanβ = 50, A0 = +m1/2

tanβ = 50, A0 = -m1/2

tanβ = 50, A0 = +2 m1/2

tanβ = 50, A0 = -2 m1/2

⇒ Good description of the dataPreference for relatively light SUSY scale


Fit results for particle masses, tan β = 10:mχ+

1≈ mχ0

2, mτ1

[J. Ellis, S. Heinemeyer, K. Olive, A. Weber, G. W. ’07]

0 200 400 600 800 1000mχ~0

2, mχ~+

1 [GeV]

0

2

4

6

8

10

12

14

χ2 (to

day)

CMSSM, µ > 0, mt = 171.4

tanβ = 10, A0 = 0

tanβ = 10, A0 = +m1/2

tanβ = 10, A0 = -m1/2

tanβ = 10, A0 = +2 m1/2

tanβ = 10, A0 = -2 m1/2

0 200 400 600 800 1000mτ~1

[GeV]

0

2

4

6

8

10

12

14

χ2 (to

day)

CMSSM, µ > 0, mt = 171.4

tanβ = 10, A0 = 0

tanβ = 10, A0 = +m1/2

tanβ = 10, A0 = -m1/2

tanβ = 10, A0 = +2 m1/2

tanβ = 10, A0 = -2 m1/2

⇒ Good prospects for the LHC and ILCSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.37

Global CMSSM fit, all CMSSM parameters anddark matter constraint included in the fit

68% (dotted) and 95% (solid) confidence level regions[O. Buchmueller, R. Cavanaugh, A. De Roeck, S. Heinemeyer, G. Isidori,P. Paradisi, F. Ronga, A. Weber, G. W. ’07]

0 100 200 300 400 500 600 700 800

-1000

-500

0

500

1000A0

m1/2

⇒ Best fit values: tan β ≈ 10, m1/2 ≈ 300 GeVSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.38

Indirect limits on the light Higgs mass in theCMSSM EWPO + BPO + dark matter constraints

χ2 fit for Mh, without imposing direct search limit [O. Buchmueller,R. Cavanaugh, A. De Roeck, S. Heinemeyer, G. Isidori, P. Paradisi, F. Ronga,A. Weber, G. W. ’07]

SM CMSSM

[GeV]Hm40 50 60 70 80 90100 200

2 χ∆

0

0.5

1

1.5

2

2.5

3

3.5

4

excludedLEP

[GeV]Hm40 50 60 70 80 90100 200

2 χ∆

0

0.5

1

1.5

2

2.5

3

3.5

4

arXiv:0707.3447

⇒ High sensitivity, less tension than in SMSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.39

Comparison of preferred region in m0–m1/2 planewith LHC discovery reach for 1 fb−1

[O. Buchmueller, R. Cavanaugh, A. De Roeck, S. Heinemeyer, G. Isidori,P. Paradisi, F. Ronga, A. Weber, G. W. ’07]

⇒ Preferred region would lead to early discoverySupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.40


MSSM Higgs sector: “simplest” extension of SM Higgs sector,two parameters instead of one




Many theories have over large part of their parameter space alight Higgs with properties very similar to those of the SMHiggs boson

Example: SUSY in the “decoupling limit”, MA ≫MZ




Many theories have over large part of their parameter space alight Higgs with properties very similar to those of the SMHiggs boson

Example: SUSY in the “decoupling limit”, MA ≫MZ

− How can one distinguish the SM-like state from theSM-Higgs?

− How can one detect / identify the other states?


MSSM Higgs discovery contours ( mmax

hscenario)

ATLAS

LEP 2000

ATLAS

mA (GeV)

tan

β

1

2

3

4

56789

10

20

30

40

50

50 100 150 200 250 300 350 400 450 500

0h

0H A

0 +-H

0h

0H A

0 +-H

0h

0H A

00

h H+-

0h H

+-

0h only

0 0Hh

ATLAS - 300 fbmaximal mixing

-1

LEP excluded

⇒ Discovery of at least one Higgs state “expected”Significant region where only one SM-like Higgs can bedetected at the LHC Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.42

Higgs couplings: sensitivity to deviations fromthe SM

SM vs. BSM physics (ILC precisions):

⇒ Precision measurement of Higgs couplings allowsdistinction between different models


Higgs coupling determination at the LHC

LHC does not provide a measurement of the total productioncross section (no recoil method like LEP, ILC: e+e− → ZH,Z → e+e−, µ+µ−)

Production × decay at the LHC yields combinations of Higgscouplings (Γprod, decay ∼ g2

prod, decay):

σ(H)× BR(H → a + b) ∼ΓprodΓdecay

Γtot,

Large uncertainty on dominant decay for light Higgs: H → bb

⇒ LHC can directly determine only ratios of couplings,e.g. g2

Hττ/g2HWW


Higgs coupling determination at the LHC

Absolute values of the couplings at the LHC can be obtainedwith an additional (mild) theory assumption:[M. Duhrssen, S. Heinemeyer, H. Logan, D. Rainwater, G. W., D. Zeppenfeld ’04]

g2HV V ≤ (g2

HV V )SM, V = W,Z

⇒ Upper bound on ΓV

Observation of Higgs production⇒ Lower bound on production couplings and Γtot

Observation of H → V V in WBF⇒ Determines Γ2

V /Γtot ⇒ Upper bound on Γtot

⇒ Absolute determination of Γtot and Higgs couplingsSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.45

Access to the Hbb coupling via central exclusivediffractive (CED) Higgs production, pp→ p⊕H ⊕ p

Protons remainundestroyed, forward pro-ton tagging in “roman pot”detectors

exchange of colour-singlet

no hadronic activitybetween outgoing protonsand Higgs decay productsJz = 0 selection rule

⇒ Good mass resolution, access to H → bb decay mode

⇒ Experimentally very challenging (pile-up, in particularat high lumi, . . . ), but may yield interesting information

[see talks by A. Martin, M. Grothe, C. Royon]Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.46

3σ contours for CED production of the light MSSMHiggs boson in the h→ bb channel

[S. Heinemeyer, V.A. Khoze, M.G. Ryskin, W.J. Stirling, M. Tasevsky, G. W. ’07]

[GeV]Am100 120 140 160 180 200 220 240

βta

n

5

10

15

20

25

30

35

40

45

50

= 115 GeV hM = 125 GeVhM

= 130 GeVhM

= 131 GeVhM

-1L = 60 fb 2 ×, eff. -1L = 60 fb

-1L = 600 fb 2 ×, eff. -1L = 600 fb

⇒ Almost complete coverage with high integrated luminosity⇒ CED channel may yield crucial information on hbb coupling


5σ discovery contours for CED production of theheavy CP-even MSSM Higgs, H → bb channel

[S. Heinemeyer, V.A. Khoze, M.G. Ryskin, W.J. Stirling, M. Tasevsky, G. W. ’07]

[GeV]Am100 120 140 160 180 200 220 240

βta

n

5

10

15

20

25

30

35

40

45

50 =

132

GeV

HM

= 1

40 G

eVH

M

= 1

60 G

eVH

M

= 2

00 G

eVH

M

= 2

45 G

eVH

M

2 ×, eff. -1L = 60 fb -1L = 600 fb

2 ×, eff. -1L = 600 fb

⇒ Significant discovery reach, discovery of a 140 GeV Higgsfor all values of tan β with high integrated luminosity


"Typical" features of extended Higgs sectors

A light Higgs with SM-like properties, couples with aboutSM-strength to gauge bosons

Heavy Higgs states that decouple from the gauge bosons

For “non-standard” Higgs states:

⇒ Cannot use weak-boson fusion channels for production

⇒ Possible production channels: gg → H, bbH, . . .

Cannot use LHC “gold plated” decay mode H → ZZ → 4µ

⇒ Search for heavy Higgs bosons H,A,H± is very differentfrom the SM case


We cannot take a SM-type Higgs for granted

Higgs phenomenology can be drastically different from theSM case even in the MSSM:




Higgs may be much lighter than 114 GeV

Example: SUSY with CP-violation

⇒ no firm experimental lower bound on MH

⇒ LHC needs to look also for light Higgs bosons




Higgs may be much lighter than 114 GeV

Example: SUSY with CP-violation

⇒ no firm experimental lower bound on MH

⇒ LHC needs to look also for light Higgs bosons

Significant suppression / enhancement of variouscouplings possible with respect to the SM

Example: large enhancement of Hbb coupling

⇒ large suppression of BR(h→ γγ), BR(h→ WW ∗), . . .Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.50


Higgs decays into SUSY particles, H → invisible,

H → soft jets, . . .

SUSY decays into Higgs, . . .






NMSSM: h→ aa, singlet dominated light Higgs, . . .

More exotic scenarios:Higgs–radion mixing, “continuum” Higgs models, . . .






NMSSM: h→ aa, singlet dominated light Higgs, . . .

More exotic scenarios:Higgs–radion mixing, “continuum” Higgs models, . . .

⇒ Need to be prepared for non-standard phenomenology



LHC: scattering of composite objects, strongly interacting

⇒ Very large QCD backgrounds, low signal–to–backgroundratios

Signal cross sections for SM QCD, SUSY, Higgs, . . .[see talks by S. Moch, R. Cousins]

⇒ Search for SUSY, Higgs, . . . at the LHC:



LHC: scattering of composite objects, strongly interacting

⇒ Very large QCD backgrounds, low signal–to–backgroundratios

Signal cross sections for SM QCD, SUSY, Higgs, . . .[see talks by S. Moch, R. Cousins]

⇒ Search for SUSY, Higgs, . . . at the LHC:

“Like the search for a needle in 100,000 haystacks”[J. Ellis, SUSY07]


SM backgrounds to missing energy signals

[M. Mangano, SUSY07]


Instrumental backgrounds

[see R. Cousins’ talk] [M. Mangano, SUSY07]


Determining backgrounds from data



Role of theoretical predictions



SUSY signals at the LHC

LHC: good prospects for strongly interacting new particles

long decay chains ⇒ complicated final states

e.g.: g → qq → qqχ02 → qqτ τ → qqττ χ0

1

Many states are produced at once, difficult to disentangle






1


⇒ It quacks like SUSY!






1


⇒ It quacks like SUSY!

But ist it really SUSY? Which particles are actually produced?

Main background for determining SUSY properties at the LHCwill be SUSY itself!


It quacks like SUSY, but . . .


It quacks like SUSY, but . . .

does every SM particle really have a superpartner?

do their spins differ by 1/2?

are their gauge quantum numbers the same?

are their couplings identical?

do the SUSY predictions for mass relations hold, . . . ?


Even when we are sure that it is actually SUSY,we will still want to know:


Even when we are sure that it is actually SUSY,we will still want to know:

is the lightest SUSY particle really the neutralino, or thestau or the sneutrino, or the gravitino or . . . ?

is it the MSSM, or the NMSSM, or the mNSSM, or theN2MSSM, or . . . ?

what are the experimental values of the 105 (or more)SUSY parameters?

does SUSY give the right amount of dark matter?

what is the mechanism of SUSY breaking?

We will ask similar questions for other kinds of new physicsSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.59

SUSY searches at the LHC

Cascade decays: complicated decay chains for squarks andgluinos

qL χ02

q1 `2˜`R

`1χ0

1

Main tool: dilepton “edge” fromχ0

2 → ℓ+ℓ−χ01

m(ll) (GeV)0 10 20 30 40 50 60 70 80 90 100

0

100

200

300

400

500

600

700

800


Information from kinematical edges andthresholds

`

m2ll

édge=

`

m2χ0

2

− m2

lR

´`

m2

lR− m2

χ0

1

´

m2

lR

`

m2qll

édge=

`

m2qL

− m2χ0

2

´`

m2χ0

2

− m2χ0

1

´

m2χ0

2

`

m2ql

édge

min=

`

m2qL

− m2χ0

2

´`

m2χ0

2

− m2

lR

´

m2χ0

2

`

m2ql

édge

max=

`

m2qL

− m2χ0

2

´`

m2

lR− m2

χ0

1

´

m2

lR`

m2qll

´thres= [(m2

qL+ m2

χ0

2

)(m2χ0

2

− m2

lR)(m2

lR− m2

χ0

1

)

−(m2qL

− m2χ0

2

)

r

(m2χ0

2

+ m2

lR)2(m2

lR+ m2

χ0

1

)2 − 16m2χ0

2

m4

lRm2

χ0

1

+2m2

lR(m2

qL− m2

χ0

2

)(m2χ0

2

− m2χ0

1

)]/(4m2

lRm2

χ0

2

)

⇒ Precise information on mass squared differencesFrom overconstrained system⇒ absolute mass determination


Dilepton edges


Dilepton edges

“Experimentalist’s definition” of a lepton: e±, µ±

τ ’s are much more challenging


Dilepton edges



However, most of the leptons are in fact τ ’s, completelydominate at high tan β

E.g.: SPS1a, tanβ = 10:BR(χ0

2 → e±e∓) = BR(χ02 → µ±µ∓) = 6%

BR(χ02 → τ±τ∓) = 88%

Use more information than just the kinematic edges:complete shapes?


Dilepton edges



However, most of the leptons are in fact τ ’s, completelydominate at high tan β

E.g.: SPS1a, tanβ = 10:BR(χ0

2 → e±e∓) = BR(χ02 → µ±µ∓) = 6%

BR(χ02 → τ±τ∓) = 88%

Use more information than just the kinematic edges:complete shapes?

What is the impact of Monte Carlo uncertainties,higher-order contributions?


Particle spins and CP properties

Determination of spin and CP prop. of observed new stateswill be crucial for establishing the SUSY nature of the signal

Spin: establish fermion–boson symmetry, distinguish fromuniversal extra dimensions (can have similar spectrum asin SUSY, but different spins), spin 2 excitations, . . .

CP properties: pseudo-scalar Higgs, mixed states, . . .

CP violation:Measure CPV effects in CP-conserving observables?Access to CP-violating observables: CP asymmetries,triple products, . . . ?

⇒ Very important information, but experimentally challengingat the LHC [see G. Polesello’s talk]


SUSY parameter determination

Need a comprehensive and precise determination of as manySUSY parameters as possible in order to− establish SUSY experimentally− disentangle patterns of SUSY breaking




SUSY contains many parameters that are not closely relatedto a specific experimental observable:mixing angles, tan β, complex phases, . . .Most observables depend on a variety of SUSY parameters⇒ SUSY parameters need to be determined by global fits to

a large set of observables




SUSY contains many parameters that are not closely relatedto a specific experimental observable:mixing angles, tan β, complex phases, . . .Most observables depend on a variety of SUSY parameters⇒ SUSY parameters need to be determined by global fits to

a large set of observables

How well can we identify particles in different decay chains?Theory uncertainties?


How precisely do we need to know the SUSY parameters?

Dark matter relic density: measurement vs. prediction

Aim:match the precision of the relic density measurement with theprediction based on collider data

⇒ sensitive test of SUSY dark matter hypothesis

Relic density measurement:

current (WMAP): ≈ 10%

future (Planck): ≈ 2%


Prediction of the dark matter density

We cannot assume a certain SUSY scenario (CMSSM), wehave to test it

Need precision measurements of:





LSP mass — the dark matter particle






LSP couplings






LSP couplings

NLSP–LSP mass difference (“coannihilation region”),down to 0.2 GeV






LSP couplings


Higgs masses, Higgs couplings (“Higgs funnel region”)






LSP couplings


Higgs masses, Higgs couplings (“Higgs funnel region”)

Prediction for “focus point region” depends extremelysensitively on mt through RGE running: would need mt

with accuracy of O(20 MeV)

. . . [see M. Drees’ talk]Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.66

Determination of SUSY parameters: global fit

Comparison: LHC only vs. LHC ⊕ ILC for SPS1a’ point

m0 = 100 GeV, m1/2 = 250 GeV, A0 = −100 GeV, tan β = 10, µ > 0

“bulk” region of mSUGRA scenario ↔ “best case scenario”

[P. Bechtle, K. Desch, P. Wienemann ’05]

LHC input:

mass measurements and precisions from detailedexperimental studies at ATLAS and CMS

+ assumption on t1,2 mass measurement

+ ratios of Higgs branching ratiosSupersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.67

Fittino: LHC only vs. LHC ⊕ ILC

Parameter “True” value ILC Fit value Uncertainty Uncertainty(ILC+LHC) (LHC only)

tan β 10.00 10.00 0.11 6.7µ 400.4 GeV 400.4 GeV 1.2 GeV 811. GeVXτ -4449. GeV -4449. GeV 20.GeV 6368. GeVMeR 115.60 GeV 115.60 GeV 0.27 GeV 39. GeVMτR 109.89 GeV 109.89 GeV 0.41 GeV 1056. GeVMeL 181.30 GeV 181.30 GeV 0.10 GeV 12.9 GeVMτL 179.54 GeV 179.54 GeV 0.14 GeV 1369. GeVXt -565.7 GeV -565.7 GeV 3.1 GeV 548. GeVXb -4935. GeV -4935. GeV 1284. GeV 6703. GeVMuR 503. GeV 503. GeV 24. GeV 25. GeVMbR

497. GeV 497. GeV 8. GeV 1269. GeVMtR

380.9 GeV 380.9 GeV 2.5 GeV 753. GeVMuL 523. GeV 523. GeV 10. GeV 19. GeVMtL

467.7 GeV 467.7 GeV 3.1 GeV 424. GeVM1 103.27 GeV 103.27 GeV 0.06 GeV 8.0 GeVM2 193.45 GeV 193.45 GeV 0.10 GeV 132. GeVM3 569. GeV 569. GeV 7. GeV 10.1 GeVmArun 312.0 GeV 311.9 GeV 4.6 GeV 1272. GeVmt 178.00 GeV 178.00 GeV 0.050 GeV 0.27 GeV

χ2 for unsmeared observables: 5.3× 10−5

⇒ most of theLagrangianparameters canhardly beconstrained byLHC data alone(even for SPS1a)

⇒ need LHC ⊕ ILCfor determinationof SUSYparameters

[see K. Desch’s talk]


Conclusions

LHC will open the new territory of TeV-scale physics,where we firmly expect ground-breaking discoveries


Conclusions


SUSY can show up in many different ways: we have to beprepared for a wide range of possible phenomenology


Conclusions



Detection of a BSM signal will only be a first step


Conclusions




Large experimental efforts + accurate theory predictionswill be necessary to determine the nature of TeV-scalephysics


Conclusions




Large experimental efforts + accurate theory predictionswill be necessary to determine the nature of TeV-scalephysics

Looking forward to very exciting times!Supersymmetry at the LHC, Georg Weiglein, Heidelberg 08/2007 – p.69

Documents

Supersymmetry at the LHC - Heidelberg University · Supersymmetry at the LHC Georg Weiglein IPPP Durham Heidelberg, 08/2007 Introduction Properties of SUSY theories What is the scale