SUSY, UED, LHT at the LHCSUSY signatures at LHC ⋆ g˜g˜, ˜gq˜, q˜q˜ production dominant for m...

SUSY, UED, LHT at the LHC

Howard Baer

Florida State/ University of Oklahoma

⋆ SUSY at LHC

• SUSY signatures

• SM backgrounds

• cuts: optimizing signal/BG

• LHC reach for SUSY

• beyond discovery:

∗ precision measurements

⋆ UED at LHC

⋆ LHT at LHC

S. Abdullin Oct.2000

GEANT figure

mSUGRA : m 0 = 1000 GeV, m 1/2 = 500 GeV, A 0= 0, tan β = 35, µ > 0

m g ~ = 1266 GeV

m u ~ = 1450 GeV

m t ~ = 1026 GeV

m

~ = 410 GeV 1

L

Z 2

m ~ = 214 GeVZ

1

m h = 119 GeV

g ~

t ~

1 t -

W -

+ b -

T = 113 GeV)

s + c -

~W +

2 + b ~W +

1 + Z ν ν-

( jet4, E

T = 79 GeV) ( jet5, E

T = 536 GeV)( jet3, E

~Z

1 W +

+ τ e ν

+ +

u ~

L ~Z

2 + u T = 1196 GeV)( jet6, E

~Z

1 + h

b -

T = 320 GeV)( jet2, ET = 206 GeV)( jet1, E b

ν

S.

Abd

ullin

, A

. Nik

iten

ko

b-jet 1

b-jet 2 Z 1

Z 1

b-jet 3

b-jet 4

jet 5

jet 6

E T

miss= 380 GeV

~

~

5

Howie Baer, TASI 2008: SUSY, UED, LHT at LHC, June 19, 2008 1

SUSY signatures at LHC

⋆ gg, gq, qq production dominant for m<∼ 1 TeV

⋆ lengthy cascade decays of g q are likely

⋆ events characterized by multiple hard jets, isolated and non-isolated leptons

es and µs, and 6ET from Z1 or G or νs escaping

⋆ many jets are b (displaced vertices due to long B lifetime) and τ (1 or 3

charged prongs) jets

⋆ one way to classify signatures is according to number of isolated leptons


Classify event topologies according to isolated leptons

• 6ET + jets

• 1ℓ+ 6ET + jets

• opposite − sign (OS) 2ℓ+ 6ET + jets

• same − sign (SS)2ℓ+ 6ET + jets





Backgrounds to SUSY events at LHC

⋆ numerous SM processes give same signature as SUSY!

⋆ SM BGs include:

• QCD: multi-jet qq, qq, qg, gg production where 6ET comes from

mis-measurement, cracks, etc.

– tt, bb, cc

– W or Z+ multi-jet production

– WW , WZ, ZZ production, where Z → νν or τ τ

∗ all of above embedded in Isajet, Pythia, Herwig

– four particle processes: e.g. tttt, ttbb, etc.

– WWW , etc.

∗ the 2 → n for n > 2 processes usually need CalcHEP/Madgraph

– overlapping events; fake b-jets; fake leptons, etc


Background issues

⋆ The BGs must be estimated using full event simulation

– jet broadening, interaction of particles with detectors

⋆ Must also simulate detector: GEANT or toy or...

⋆ If possible, use complete 2 → n-body matrix elements

⋆ matching of PS and HO-ME results? avoid double counting

– VECBOS, AlpGEN, MCNLO , etc.

⋆ NLO QCD corrections?

⋆ matching the data: how well do we know SM BG rates?

⋆ first order of business at LHC: re-discover the SM!

– calibrate detectors using Z+jets, W+jets, tt production


Example: calculate SUSY reach of LHC for 10, 100 fb−1

⋆ Cuts and pre-cuts:

⋆ 6ET > 200 GeV

⋆ Nj ≥ 2 (where pT (jet) > 40 GeV and |η(jet)| < 3

⋆ Grid of cuts for optimized S/B:

– Nj ≥ 2 − 10

– 6ET > 200 − 1400 GeV

– ET (j1) > 40 − 1000 GeV

– ET (j2) > 40 − 500 GeV

– ST > 0 − 0.2

– muon isolation

⋆ S > 10 events for 100 fb−1

⋆ S > 5√

B for optimal set of cuts


Sparticle reach of LHC for 100−1 fb

mSugra with tanβ = 10, A0 = 0, µ > 0

m0 (GeV)

m1/

2 (G

eV)

ET miss

0l

1l

2l SS

2l OS

3l

Z→l+l-

≥4l

γ

m(g~)=2 TeV

m(u~

L)=2 TeV

100200300400500600700800900

100011001200130014001500

0 1000 2000 3000 4000 5000


m0 (GeV)m

1/2

(GeV

)

ET miss

0l

1l

2l SS

2l OS

3l

Z→l+l-

≥4l

γ

m(g~)=2 TeV

m(u~

L)=2 TeV

100200300400500600700800900

100011001200130014001500

0 1000 2000 3000 4000 5000

HB, Balazs, Belyaev, Krupovnickas, Tata: JHEP 0306, 054 (2003)


Old sparticle reach of LHC for 10−1 fb incl. 2ℓ and 3ℓ

0 500 1000 1500 2000 0 500 1000 1500 20000

200

400

600

800

0

200

400

600

800

0

200

400

600

800

0

200

400

600

800

m0 (GeV) m0 (GeV)

2l,0j

2l,0j2l,0j

2l,0j

3l,0j

3l,0j3l,0j

3l,0j

1l

1l1l

1l

0l

0l0l

0l

SS

SSSS

SS

OS

OSOS

OS3l

3l

3l

3l

m1/

2 (

GeV

)m

1/2

(G

eV)

tan β = 10, µ > 0

tan β = 10, µ < 0

tan β = 2, µ > 0

tan β = 2, µ < 0

HB, Chen, Paige, Tata: PRD53, 6241 (1996)


Sparticle reach of LHC for 10−1 fb; RPV with Z1 → cds

HB, Chen, Paige, Tata: PRD55, 1466 (1997)


Sparticle reach of CMS; various∫Ldt

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0 500 1000 1500 2000

m0 (GeV)

m1/

2 (

GeV

)

mSUGRA reach in ET miss

+ jets final state

1 month, low lumi (1 fb -1)

1 year, low lumi (10 fb -1)

1 year, high lumi (100 fb -1)

3 years, high lumi (300 fb -1)

g~(500)

g~(1000)

g~(1500)

g~(2000)

g~(2500)

g~(3000)

q~(2500)

q~(2000)

q~(1500)

q~(1000)

q~(500)

h (114) mass limit

h(123)

A0 = 0 , tanβ = 35 , µ > 0

Cha

rged

LS

P

Chargino Searches at LEP

No symmetry breaking


Sparticle reach in AMSB model

tanβ = 35, µ > 0

m = 2 TeV

m = 2 TeV

m ≈ m

g~

u~

R

Z~

2 e~

R0 l1 lOSSS3 l

m0 (GeV)

m3/

2 (T

eV)


Sparticle reach in GMSB model: various model lines

Model NLSP Tevatron LHC

Line (25 fb−1) (10 fb−1)

A Z1 ∼ B Λ ∼= 115 TeV, Λ ∼= 400 TeV

Z1 → γG mg/q ∼ 0.87 TeV, mg/q ∼ 2.8 TeV,

llγγ + EmissT γγ + Emiss

T

B τ1 Λ ∼= 53 TeV, Λ ∼= 150 TeV

mg/q ∼ 0.82 TeV, mg/q ∼ 2.0 TeV,

Clean channels 3l + EmissT

3l + 1τ2l + 1τ3l

+2τ1l + 3τ2l


Sparticle reach of all colliders and relic density

200

400

600

800

1000

1200

1400

1600

0 1000 2000 3000 4000 5000 6000 7000 8000


m0 (GeV)

m1/

2 (G

eV)

LHC

Tevatron

LC 500

LC 1000

Ωh2< 0.129

LEP2 excluded

200

400

600

800

1000

1200

1400

1600

0 1000 2000 3000 4000 5000 6000 7000

mSugra with tanβ = 45, A0 = 0, µ < 0

m0 (GeV)m

1/2

(GeV

)

LHC

Tevatron

LC 500

LC 1000

Ωh2< 0.129

LEP2 excluded

HB, Belyaev, Krupovnickas, Tata: JHEP 0402, 007 (2004)


Sparticle reach of colliders plus DM DD/IDD

200

400

600

800

1000

1200

1400

1600

0 1000 2000 3000 4000 5000 6000 7000 8000

mSUGRA, A0=0 tanβ=10, µ>0

m0(GeV)

m1/

2(G

eV)

LEP

no REWSB

Z~

1 no

t LS

P

Φ(p-)=3x10-7 GeV-1 cm-2 s-1 sr-1

(S/B)e+=0.01

Φ(γ)=10-10 cm-2 s-1

Φsun(µ)=40 km-2 yr-1

0<Ωh2<0.129

mh=114.4 GeV

σ(Z~

1p)=10-9 pb

LHC

LC1000

LC500

TEV

µD

D

200

400

600

800

1000

1200

1400

1600

0 1000 2000 3000 4000 5000

mSUGRA, A0=0, tanβ=45, µ<0

m0(GeV)

m1/

2(G

eV)

LEP

no REWSB

Z~

1 no

t LS

P

Φ(p-)=3e-7 GeV-1 cm-2 s-1 sr-1 (S/B)e+=0.01

Φ(γ)=10-10 cm-2 s-1 Φsun(µ)=40 km-2 yr-1

0< Ωh2< 0.129

mh =114.4 GeV

Φearth(µ)=40 km-2 yr-1 σ(Z~

1p)=10-9 pb

LHC

LC1000

LC500

TEV

µ

DD

HB, Belyaev, O’Farrill, Krupovnickas: JHEP 0408, 005 (2004)


Reach of Atlas for SUSY Higgs: 300 fb−1


Early SUSY discovery at LHC with just 0.1 fb−1?

• To make 6ET cut, complete knowledge of detector needed

– dead regions

– “hot” cells

– cosmic rays

– calorimeter mis-measurement

– beam-gas events

• Can we make early discovery of SUSY at LHC without 6ET ?

• Expect SUSY events to be rich in jets, b-jets, isolated ℓs, τ -jets,....

• These are detectable, rather than inferred objects

• Answer: YES! See HB, Prosper, Summy, arXiv:0801.3799


D0 saga with missing ET


Require simple cuts: plot jet multiplicity

• ≥ 4-jets ET > 100, 50, 50, 50 GeV; ST ≥ 0.2

5 10 15 20# of Jets

0.01

0.1

1

10

100

1000

10000

1e+05

1e+06

1e+07

σ (f

b)

SO10ptA(9202.87,62.498,-19964.500,49.1,171)QCD JetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

No. of JetsCuts C1a


Simple cuts: lepton multiplicity

0 5# of Isolated Leptons

0.1

1

10

100

1000

10000

1e+05

1e+06

1e+07

σ (f

b)SO10ptA(9202.87,62.498,-19964.500,49.1,171)QCD JetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

No. of Isolated LeptonsCuts C1a


Cuts C1′ plus ≥ 3ℓ

400 600 800 1000 1200m

g~ (GeV)

0

30

60

90

120

σ ≥3l (

fb)

m0 = 200 GeV

m0 = 1000 GeV

m0 = 70, A

0 = -300

Cuts C1am

t=171.0, A

0=0, tanβ=10, sgnµ>0

5σ level at 0.1 fb-1

5σ level at 1 fb-1


Cuts C1′ plus ≥ 2 OS/SF ℓ

0 50 100 150m

ll (GeV)

0

10

20

30

40

dσ/d

mll (

fb/G

eV)

SO10ptA + BGQCD JetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

Cuts C1a


Precision measurements at LHC

• Meff = 6ET + ET (j1) + · · · + ET (j4) sets overall mg, mq scale

• m(ℓℓ) < m eZ2

− m eZ1

mass edge

• m(ℓℓ) distribution shape

• combine m(ℓℓ) with jets to gain m(ℓℓj) mass edge: info on mq

• further mass edges possible e.g. m(ℓℓjj)

• Higgs mass bump h → bb likely visible in 6ET + jets events

• in favorable cases, may overconstrain system for a given model

⋆ methodology very p-space dependent

⋆ some regions are very difficult e.g. HB/FP


Paige, Hinchliffe et al. case studies:

• examined many model case studies in mSUGRA, GMSB, high tanβ...

• classic study: pt.5 of PRD55, 5520 (1997) and PRD62, 015009 (2000)

• m0, m1/2, A0, tan β, sign(µ) = (100, 300, 0, 2, 1) in GeV

• dominant gg production with g → qqL → qqZ2 → q1q2ℓ1ℓ → q1q2ℓ1ℓ2Z1

(string of 2-body decays)

• can reconstruct 4 mass edges; allows one to fit four masses:

mqL, m eZ2

, mℓ, m eZ1

to 3 − 12%

• can also find Higgs h in the SUSY cascade decay events

• if enough sparticle masses measured, can fit to MSSM/SUGRA parameters


Meff = ET (j1) + ET (j2) + ET (j3) + ET (j4)+ 6ET

• rough estimate of mg, mq can be gained from max of Meff

10-13

10-12

10-11

10-10

10-9

10-8

10-7

0 1000 2000 3000 4000Meff (GeV)

dσ/d

Mef

f (m

b/40

0 G

eV)

Atlas TDR (F. Paige)


m(ℓ+ℓ−) mass edge from Z2 → ℓ+ℓ−Z1

• kinematically, m(ℓ+ℓ−) < m eZ2

− m eZ1

• for Z2 → ℓ+ℓ− → (ℓ+Z1)ℓ−, have

m(ℓ+ℓ−) < m eZ2

√1 − m2

ℓ

m2

eZ2

√1 −

m2

eZ1

m2

ℓ

< m eZ2

− m eZ1

0

100

200

300

400

0 50 100 150 200

mll (GeV)

even

ts/4

GeV

/30

fb−1

signal

SM backg

SUSY backg


m(ℓ+ℓ−q) mass edge from q → qZ2

• qL → qZ2 → qℓ±ℓ∓ → qℓ±ℓ∓Z1

0

500

1000

1500

2000

2500

0 200 400 600 800 1000mllq (GeV)

Eve

nts/

20 G

eV/1

00 fb

-1



m(ℓq) mass edge from q → qZ2

0

200

400

600

0 200 400 600 800 1000mlq (GeV)

Eve

nts/

20 G

eV/1

00 fb

-1



m(ℓq) mass edge from q → qZ2

0

100

200

300

0 200 400 600 800 1000mllq (GeV)

Eve

nts/

20 G

eV/1

00 fb

-1



m(bb) Higgs mass bump in SUSY jets + 6ET events

0

200

400

600

800

0 100 200 300 400mbb (GeV)

Eve

nts/

8 G

eV

signal

SM backg

SUSY backg



Case study of SUSY in the focus point region of mSUGRA

• m0 ∼ 3 TeV so squarks/sleptons decouple

• mg ∼ 1 TeV and µ ∼ 226 GeV so W1, Z2 light

• SUSY production: soft (W+1 W−, W±Z2) and hard (gg) component

200 300 400 500 600 700 800 900m

1/2 (GeV)

0

500

1000

1500

2000

Mas

s (G

eV)

mg~

mZ~

1

mZ~

2

mZ~

3

mZ~

4

mW~

1

mW~

2

HB/FP Sparticle Masses

mg~

mZ~

4, m

W~2

mZ~

2, m

Z~3, m

W~1

mZ~

1

HB, Barger, Shaughnessy, Summy and Wang


FP case study: cross sections

1000 1500 2000m

g~ (GeV)

0.0001

0.01

1

100

10000σ

(fb)

W~1Z~

1

W~1Z~

2

W~1Z~

3

W~1W~

1

Z~1Z~

2

Z~2Z~

2

Z~2Z~

3

Z~1Z~

3

HB/FP Cross Sections

g~g~

Z~2Z~

2

Z~1Z~

2

Z~1Z~

3

Z~2Z~

3

W~1W~

1

W~1Z~

3

W~1Z~

1

W~1Z~

2


Apply cuts set C1

• 6ET > max(100 GeV, 0.2Meff

• nj ≥ 4; ST > 0.2

• ET (j1, j2, j3, j4) > 100, 50, 50, 50 GeV

0 1000 2000 3000M

eff (GeV)

0.0001

0.001

0.01

0.1

1

10

100

dσ/d

Mef

f (fb

/GeV

)

FP(3050,400,0,30,1,175)QCD jetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

Effective MassCuts C1


n(jets) distribution

0 5 10 15# of Jets

0.001

0.01

0.1

1

10

100

1000

10000

σ (f

b)FP(3050,400,0,30,1,175)QCD JetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

No. of JetsCuts C1


n(b − jets) distribution

0 5 10 15# of b-jets

0.001

0.01

0.1

1

10

100

1000

10000

σ (f

b)FP(3050,400,0,30,1,175)QCD JetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

No. of b-jets (60% eff.)Cuts C1


n(leptons) (isolated) distribution

0 5 10 15# of Leptons

0.001

0.01

0.1

1

10

100

1000

10000

σ (f

b)FP(3050,400,0,30,1,175)

QCD Jets

tt

W+jets

Z+jets

WW, WZ, ZZ

Sum of Backgrounds

No. of Isolated LeptonsCuts C1


Augmented effective mass AT

• n(jets) ≥ 7

• n(b − jets) ≥ 2

0 1000 2000 3000A

T (GeV)

0.001

0.01

dσ/d

AT (

fb/G

eV)

FP(3050,400,0,30,1,175)QCD jetsttW+jetsZ+jetsWW, WZ, ZZSum of Backgrounds

Augmented Effective MassCuts C1, n

b-jets>=2 (60% eff.)


Remaining signal vs. mg

• n(jets) ≥ 7; n(b − jets) ≥ 2; AT > 1400 GeV

• signal way above BG; purely from gg production

• extract mg from total rate to ∼ 8%

1000 1500 2000m

g~

0

10

20

30

40

σ (f

b)

TH

100 fb-1

errorTH ±15%TH ±15% ±100%BGBG

LEP

2 ex

clud

ed


Same flavor/opposite sign dilepton mass distribution

• cuts C1; n(leps) ≥ 2; n(jets) ≥ 4; n(b − jets) ≥ 2; AT > 1200 GeV

• two mass edges stand out

0 50 100m

ll (GeV)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

dσ/d

mll (

fb/G

eV)

Z~2- Z~

1Z~

3- Z~

1


Some aspects of Kaluza-Klein theory

⋆ Write down Lagrangian, but in 5 space-time dimensions

⋆ Unify gravity plus E&M?

⋆ Compactification on manifold (circle) leads to zero modes plus KK-excitations

with mass m =√

m20 + n2/R2 where R is compacification radius

• get 2 KK excited states for each n value

• excitations have same spin, couplings, charges as zero modes- just higher

masses

⋆ instead, compactify on orbifold, e.g. S1/Z2

⋆ virtues of orbifolding:

– reduction in # of KK excitations: no Z2-odd modes

– project out unwanted zero modes

– can break symmetries of D-dimensional theory zero modes: alternative

symmetry breaking mechanism to spontaneous SB


Universal Extra Dimensions (UED)

⋆ Write down SM action in 5-d

⋆ expand SM fields in terms of Z2 odd/even functions

⋆ Compactify on S1/Z2 orbifold with radius R

⋆ Orbifolding eliminates “wrong helicity” SM zero modes to give chiral SM as

zero mode theory

⋆ Aµ has zero mode; A4 does not

⋆ low energy theory is SM zero modes

⋆ also get KK excitations starting at m ∼ 1/R

⋆ KK-parity conserved: get DM candidate LKP

⋆ spectrum: Q1, u1, d1, L1, e1, W 1±, Z1, g1, B1, H0, A0, H±



• tree level mass spectra nearly degenerate:

• radiative corrections give some splitting (Cheng, Matchev, Schmaltz)



• decay modes (CMS)


LHC reach for UED theories in 4ℓ+ 6ET channel

• pp → Z1Z1 → L1ℓL1ℓ → 4ℓ+ 6ET , etc.


Little Higgs theories

• for expert advice, see our TASI organizer, Prof. Tao Han!

• New approach to EWSB: Arkani-Hamed, Cohen, Georgi, 2001

• Higgs field arises as pseudo-Nambu-Goldstone boson from “collective”

symmetry breaking

• Symmetry ⇒ quadratic divergences to m2H cancel at 1-loop (2-loop and

higher quad. divergences remain)

• Natural cut-off of theory is ∼ 10 TeV to avoid “little hierarchy problem”

• All LH theories predict new particles at 1-10 TeV scale

– new gauge bosons AH , W±H , W 0

H to cancel gauge boson loops in m2H

– new top partner fermions T to cancel top loop in m2H

– new scalars to cancel Higgs self coupling loops

• precise details model-dependent: most popular: littlest Higgs with

SU(5)/SO(5)


Spectrum from Little Higgs theories

φφφ

A H

+++0

HW HZ

h

1 TeV

γ

T

tW,Z

gauge sector top sectorscalar sector


T-parity in Little Higgs theories (LHT)

• It was found that LH models tend to give large corrections to precision EW

observables unless mLH → 10 TeV

• This re-introduces fine-tunings in Higgs sector

• EWPOs can be saved by introducing T -parity (Cheng and Low)

– SM particles: t-even

– new GBs, scalars, some top-partners: t-odd

– then contributions to EWPOs only occur at loop level

– can allow much lighter new particle states

• t-odd particles produced in pairs

• todd particles decay to other t-odd states

• Lightest t-odd particle absolutely stable: DM candidate, usually AH (but see

Hill+Hill anomalies paper)


LHT models at LHC

• main search channel: pp → T T with T → tAH

• search for tt+ 6ET states

• see Cheng, Low and Wang, PRD74, 055001 (2006)

• Matsumoto, Nojiri, Nomura, PRD75, 055006 (2007)

• Belyaev, Chen, Tobe and Yuan, PRD74, 115020 (2006)

• Carena, Hubisz, Perelstein, Verdier, PRD75, 091701 (2007)

• Han, Mahbubani, Walker, Wang, arXiv:0803.3820 (2008)


T T production at LHC


600 800 1000 1200 1400m

T (GeV)

0.001

0.01

0.1

1

10

100

Pro

duct

ion

cros

s-se

ctio

n (p

b) QCD top production

Fermionic T production

Scalar T production

ttZ


T T discovery at LHC


• significance after cuts with 100 fb−1 at LHC

MT

MA

H

10

5

1

0.1

FERMIONIC TOP PARTNER

400 600 800 1000 1200 1400

400

200

600

800

1000

1200


Conclusions

⋆ SUSY at LHC

• event signatures

• backgrounds

• reach

• precision measurements

⋆ UED at LHC

⋆ LHT at LHC

⋆ We now have a good idea of what 6ET signatures will look like at the LHC for

a variety of models

⋆ in 2008, the road to discovery begins at the LHC: time to either

discover or rule out models such as SUSY, UED, LHT at the

weak scale, and resolve the physics behind electroweak

symmetry breaking!


SUSY, UED, LHT at the LHCSUSY signatures at LHC ⋆ g˜g˜, ˜gq˜, q˜q˜ production dominant for m...

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Transcript of SUSY, UED, LHT at the LHCSUSY signatures at LHC ⋆ g˜g˜, ˜gq˜, q˜q˜ production dominant for m...