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SUSY at LHC. Bhaskar Dutta Texas A&M University. Discovery Time…. We are about to enter into an era of major discovery. Dark Matter: we need new particles to explain the content of the universe. Standard Model: we need new physics. Supersymmetry solves both problems!.

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slide1

SUSY at LHC

Bhaskar Dutta

Texas A&M University

SUSY Theory at the LHC

slide2

Discovery Time…

We are about to enter into an era of major discovery

Dark Matter: we need new particles to explain the content of the universe

Standard Model: we need new physics

Supersymmetry solves both problems!

The super-particles are distributed around the weak scale

Our best chance to observe SUSY is at the LHC

LHC: The only experiment which directly probes TeV scale

Future results from Planck, direct and indirect detection in tandem with LHC will confirm a model

Model

SUSY Theory at the LHC

slide3

Collision of 2 Galaxy Clusters

1

2

3

4

splitting normal matter and dark matter apart

– Another Clear Evidence of Dark Matter –

(8/21/06)

Ordinary Matter

(NASA’s Chandra X

Observatory)

time

Approximately

the same size as

the Milky Way

Dark Matter

(Gravitational Lensing)

SUSY Theory at the LHC

3

slide4

SUSY at the LHC

High PT jet

[mass difference is large]

DM

The pT of jets and leptons

depend on the sparticle

masses which are given by

models

Colored particles get

produced and decay into

weakly interacting stable

particles

R-parity conserving

DM

(or l+l-, t+t-)

High PT jet

The signal : jets + leptons + missing ET

SUSY Theory at the LHC

slide5

Example Analysis

Kinematical Cuts, Event Selection - 4 jets +ETmiss

  • PTj1>100 GeV, PTj2,3,4> 50 GeV
  • Meff > 400 GeV (Meff  PTj1+PTj2+PTj3+PTj4+ ETmiss)
  • ETmiss > Max [100, 0.2 Meff]

Paige, Hinchliffe et al. , Phys. Rev. D 55 (1997) 5520

SUSY Theory at the LHC

slide6

Background

Typical SUSY events are

105 events for 10 fb-1, while

BG rate is 109-8 for

W, Z, t tbar production.

The cuts need to be optimized

Large amount of missing

energy, high pT jets, large

numbers of jets and leptons

are good handles on signal

SUSY Theory at the LHC

slide7

SUSY Models

MSSM has more than 100 parameters

The number of parameters can be reduced in different models

Minimal Model: minimal supergravity (mSUGRA)/CMSSM

Nonuniversal SUGRA model,

Anomaly mediated, NMSSM, Compressed- SUSY

Mixed Moduli, Gauge Mediated, non-critical string model, Split SUSY,

Long lived NLSP models, GUT less models, Planck scale SU(5), SO(10) models etc..

Once SUSY is discovered,

models will be searched

based on typical signals

These models also will be simultaneously tested at

the underground , satellite experiments from their

characteristic features.

SUSY Theory at the LHC

Let LHC Decide

slide8
MHiggs > 114 GeV Mchargino > 104 GeV

2.2x10-4 < Br (b s g)< 4.5x10-4

(g-2)m

Minimal Supergravity (mSUGRA)

Let us use the simplest model to describe the reach of LHC

4 parameters + 1 sign

m1/2 Common gaugino mass at MG

m0 Common scalar mass at MG

A0 Trilinear couping at MG

tanb<Hu>/<Hd> at the electroweak scale

sign(m) Sign of Higgs mixing parameter (W(2) = m HuHd)

Experimental Constraints

SUSY Theory at the LHC

slide9

Reach at the LHC

Use Jets + leptons + ETmiss discovery channel.

5s

5s

ATLAS

ATLAS

Sensitivity only weakly dependent on A0, tan(b) and sign(m).

Tovey’02

M. Tytgat (SUSY’07)

SUSY Theory at the LHC

slide10

Measurement of Masses

+…

We need to measure the masses of the particles.

Model parameters need to be determined to check the cosmological status. [Allanach, Belanger, Boudjema and Pukhov’04]

If we observe missing energy, then we have a possible dark matter candidate .

[ LHC experiments sensitive only to LSP lifetimes <1 ms (≪ tU ~ 13.7 Gyr) ]

Using the model parameters we need to calculate relic density

SUSY Theory at the LHC

slide11

Dilepton Edge Measurement

  • Deacy of results into dilepton invariant mass edge sensitive to combination of masses ofsparticles.
  • Can perform SM & SUSY background subtraction using distribution
  • e+e- + m+m- - e+m- - m+e-
  • Position of edge measured with precision ~ 0.5% (30 fb-1).
  • m0 = 100 GeV
  • m1/2 = 300 GeV
  • A0 = -300 GeV
  • tan(b) = 6
  • sgn(m) = +1

e+e- + m+m-

Point 5

ATLAS

30 fb-1

atlfast

Physics

TDR

SUSY Theory at the LHC

slide12

Measurements with Squarks

~

qL

~

~

c02

~

c01

q

l

l

l

~

qL

~

~

c02

c01

q

h

lq edge

llq edge

b

b

1% error

(100 fb-1)

1% error

(100 fb-1)

Point m0 m1/2 A0 tan(b) sign(m)

LHC Point 5 100 300 300 2 +1

  • Use Dilepton edge for reconstruction of decay chain.
  • Make invariant mass combinations of leptons and jets.
  • multiple constraints on combinations of four masses.
  • Measurement of individual sparticle masses.

bbq edge

llq threshold

1% error

(100 fb-1)

2% error

(100 fb-1)

TDR,

Point 5

TDR,

Point 5

TDR,

Point 5

TDR,

Point 5

ATLAS

ATLAS

ATLAS

ATLAS

SUSY Theory at the LHC

slide13

Model Independent Masses

Sparticle Expected precision (100 fb-1)

qL 3%

02 6%

lR 9%

01 12%

~

~

~

~

  • Measurements from edges from different jet/lepton combinations to obtain ‘model-independent’ mass measurements.

~

~

c01

lR

ATLAS

ATLAS

Mass (GeV)

Mass (GeV)

~

~

c02

qL

ATLAS

ATLAS

LHC

Point 5

Mass (GeV)

Mass (GeV)

Accuracies using many of such observables:

2% (m0), 0.6% (m1/2), 9% (tanb), 16% (A0)

Similar analysis, P. Beatle (SUSY 07); M. Rauch (SUSY 07)

SUSY Theory at the LHC

slide14

Higgsino vs Gaugino …

~

~

01

01

~

~

~

~

~

~

02

02

01

02

01

02

and : Higgsinos, three gaugino masses are very close

Kitano, Nomura’06

l+l-

With M( )-M( ) <MZ

Mslepton > Mz

Gaugino

Like and

The spectrum terminates at

m(l+l-)max

Using other

observables like

Mllq Mlq, MT, it is

Possible to measure

squark and the

neutralino mass with

An accuracy of

2% and 10%

Higgsino

Shapes looks different, 2 scenarios can be distinguished

SUSY Theory at the LHC

slide15

Dark Matter Allowed Regions

We choose mSUGRA model. However, the results can be generalized.

[Focus point region]

the lightest neutralino has a larger higgsino component

[A-annihilation funnel region]

This appears for large values of m1/2

[Neutralino-stau coannihilation region]

Bulk region-almost ruled out

SUSY Theory at the LHC

slide16

Focus Point : Jets+leptons

Typical mSUGRA point:m0=2910; A0=0; m1/2=350; m>0; tanb=30;

Large sfermion mass, smaller gaugino masses comparatively

LHC events characterized by high jet, b-jet, isol. lepton multiplicity

Baer, Barger, Shaughnessy, Summy, Wang ‘07

_

_

Gluino decays into t t c0, t b c+- (mostly)]

Higher jet, b-jet, lepton multiplicity requirement increase the

signal over background rate

SUSY Theory at the LHC

slide17

Focus Point : Jets+leptons…

Require cuts: n(j) ≥ 7, n(b) ≥ 2, AT≥ 1400 GeV

ETmiss+SETjet+SETlepton

Gluino mass can be measured with an accuracy 8%

Baer, Barger, Shaughnessy, Summy, Wang ‘07

SUSY Theory at the LHC

slide18

Focus Point: Leptons

~

~

~

~

c03 → c01 ll

c02 → c01 ll

Z0→ ll

ATLAS

300 fb-1

Preliminary

  • Large m0 sfermions are heavy
  • m0=3550 GeV; m1/2=300 GeV; A0=0; tanß=10 ; μ>0
  • Direct three-body decays c0n → c01 +2 leptons
  • Edges give m(c0n)-m(c01)

~

~

~

~

Tovey, PPC’07

Similar analysis: Error (M2-M1)~ 0.5 GeV

G. Moortgat-Pick (SUSY 07)

SUSY Theory at the LHC

slide19

Bulk Region

~

~

~

01

g

uL

~

~

l

02

The most part of this region in mSUGRA is experimentally (Higgs mass limit, bs g) ruled out

Relic density is satisfied by t channel selectron, stau and sneutrino exchange

Perform the end point analysis to determine the masses

mSUGRA point:

m0=70; A0=-300

m1/2=250; m>0;

tanb=10;

Nojiri, Polsello, Tovey’05

The error of relic density: 0.108 ± 0.01(stat + sys)

~

Includes: (+0.00,−0.002 )M(A); (+0.001, −0.011) tan β; (+0.002,−0.005) m(t2)

[With a luminosity 300 fb-1, tt edge controlled to 1 GeV]

SUSY Theory at the LHC

slide20

Coannihilation Signatures

Griest, Seckel ’91

Mass of another sparticle comes close to the neutralino:

both of them are thermally available.

This region appears for small m0 and m1/2 values and

therefore will be accessible within a short time

For smal tanb this region has e,m,t in the signals

For large tanb this region has t in the signals

SUSY Theory at the LHC

slide21

Coann. Signatures (tanb=10)

  • Small slepton-neutralino mass difference gives soft leptons
    • Low electron/muon/tau energy thresholds crucial.
  • Study point chosen within region:
    • m0=70 GeV; m1/2=350 GeV; A0=0; tanß=10 ; μ>0;
  • Decays of c02 to both lL and lR kinematically allowed.
    • Double dilepton invariant mass edge structure;
    • Edges expected at 57 / 101 GeV

Preliminary

ATLAS

100 fb-1

  • ETmiss>300 GeV
  • 2 OSSF leptons PT>10 GeV
  • >1 jet with PT>150 GeV
  • OSSF-OSOF subtraction applied

Tovey, PPC’07

SUSY Theory at the LHC

slide22

Coannihilation Region (tanb=40)

tanb = 40, m > 0, A0 = 0

Can we measure DM at colliders?

SUSY Theory at the LHC

slide23

Coann. Signatures (tanb=40)

Hard t

p

p

p

p

Soft t

Soft t

Hard t

Hard t

In Coannihilation Region of SUSY Parameter Space:

Soft t

Soft t

Final state: 3/4 ts+jets +missing energy

Use hadronically decayingt

SUSY Theory at the LHC

slide24

Four Observables

  • Sort τ’s by ET (ET1 > ET2 > …) and use OS-LS method to extract t pairs from the decays
  • NOS-LS
  • ditau invariant mass (Mtt)
  • PT of the low energy t to estimate the mass difference DM
  • jet-t-t invariant mass: Mjtt

D. Toback’s talk, parallel session

Arnowitt, B.D., Kamon, Toback, Kolev,’06; Arnowitt, Arusano,B.D., Kamon, Toback,Simeon,’06; Arnowitt,B.D., Gurrola, Kamon, Krislock, Toback, to appear; D. Toback, talk [this conf]

SUSY Theory at the LHC

slide25

SUSY Parameters

Since we are using 4 variables, we can measure DM, Mgluino and the universality relation of the gaugino masses

i.e.

Mgluino measured from the Meff method may not be accurate for this parameter space since the tau jets may pass as jets in the Meff observable.

The accuracy of measuring these parameters are important for calculating relic density.

EVENTS WITH CORRECT FINAL STATE : 2t + 2j + ETmiss

APPLY CUTS TO REDUCE SM BACKGROUND (W+jets, t-tbar,…)

ETmiss > 180 GeV, ETj1 > 100 GeV, ETj2 > 100 GeV, ETmiss + ETj1 + ETj2 > 600 GeV

ORDER TAUS BY PT & APPLY CUTS ON TAUS: WE EXPECT A SOFT t AND A HARD t

PTall > 20 GeV, PTt1 > 40 GeV

SUSY Theory at the LHC

slide26

Mttvisin ISAJET

ETvis(true) > 20, 20 GeV

ETvis(true) > 40, 20 GeV

Number of Counts / 1 GeV

ETvis(true) > 40, 40 GeV

ETt > 20 GeV is essential!

Version 7.69 (m1/2 = 347.88, m0 = 201.1)  Mgluino = 831

  • Chose di-t pairs from neutralino decays with
    • (a) |h| < 2.5
    • (b) t = hadronically-decaying tau

SUSY Theory at the LHC

slide27

Determination of m0 , m1/2

DM and Mgluinom0 , m1/2,

(for fixed A0 and tanb)

We determine dm0/m0 ~ 1.2% and dm1/2/m1/2 ~2 %

dWh2/Wh2 ~ 7% (10 fb-1)

(for A0=0, tanb=40)

SUSY Theory at the LHC

slide28

Higgs non-universality

The most common extension of mSUGRA

Case 2.

Case 1.

Drees’00;

Baer

Belyaev,

Mustafayev,

Profumo,

Tata’05

Ellis,

Olive,

Santoso’03

LHC signal:

A, H and H+- will be relatively light, and more accessible to direct LHC searches

~

There can be light uR, cR squarks, small m: leads to light and

oi

+i

SUSY Theory at the LHC

slide29

Moduli-Mediation

KKLT model: type IIB string compactification with fluxes

MSSM soft terms have been calculated, Choi, Falkowski, Nilles, Olechowski, Pokorski

Ratio of the modular mediated and anomaly mediated is given by

a phenomenological parameter a

Choi, Jeong, Okumura, Falkowski, Lebedev, Mambrini,Kitano, Nomura

Baer, Park, Tata, Wang’06,07

SUSY Theory at the LHC

slide30

GUT-less and Moduli Mediation

Ellis,

Olive,

Sandick’07

m is smaller

in the GUT -

less case

for this

Example.

MM-AMSB

GUT-less

SUSY Theory at the LHC

slide31

Other Examples…

~

~

~

01

01

02

g

Stop NLSP: stop charm+

Bino-wino Coannihilation,

Mixed Wino coannihilation

In these cases, the lightest chargino and the second lightest neutralino are

very close to the lightest neutralino

: decay opens up along with other three

body decay modes

Baer et. al.’05

Gravitino LSP (mass around 100 GeV…)

and sleptons NLSP

Long-lived charged particles:

One can find that the sleptons to decay after a long time

Feng, Su, Takayama, ’04

Gladyshev, Kazakov, Paucar’05’07

NMSSM: This model can have extra Z’, sneutrino as dark matter candidate,

In the context of of intersecting Brane Models [ Kumar, Wells’ 06]

Higgs signal at the LHC

Dermisek, Gunion’05

Moretti et al ‘06

SUSY Theory at the LHC

slide32

Other Examples…

Martin,’07; Baer et al,’07

“Compressed” MSSM:

− m2Hu = 1.92 M 23 + 0.16 M2 M3 − 0.21 M 22 − 0.33 M3 At − 0.074 M2 At +…

Naturalness argument : M3 is small, use M3<(M2,M1) at the GUT scale

Relic density is satisfied by neutralino annihilation via t –t bar production,

stop coannihilation etc.

The GUT scale

parameters are

M1,2,3= 500, 750, 250,

A0 = -500, m0 = 342GeV

A typical sample of

``compressed"

mass spectrum with

W h2 = 0.11

Reduction of

leptons in the signal.

Inflation and MSSM :Flat directions LLE, UDD etc. Smaller sparticle masses are

needed once the constraints from ns, dH are included

Allahverdi, Dutta, Mazumdar,07

Little Hierarchy :Smaller stop mass is needed

Ratazzi et al’06,

Dutta, Mimura’07

SUSY Theory at the LHC

slide33

EGRET-SUSY

EGRET excess of diffuse galactic gamma rays is explained as a signal of supersymmetric dark matter annihilation

Fitted SUSY parameters

m0=1400 GeV tanβ=50

m1/2=180 GeV A0=0.5m0

De Boer, Sander, ZhukovGladyshev, Kazakov’05,’06

ATLAS

Gluino decays have a clear

signature (4μ + 4jets + PT +

up to 4 secondary vertices). Expected # of events for ATLAS after 1year of running with LHC luminosity 1034 cm-2s-1is around 150

CMS tri-lepton discovery potential of this region

DeBoer, Zhukov, Nigel ,Sander,’06, ‘07

Bednyakov, Budagov, Gladyshev, Kazakov, Khoriauli, Khramov, Khubua’06’07

SUSY Theory at the LHC

slide34

Conclusion

LHC is a great machine to discover supersymmetry which would

solve problems in particle physics and cosmology

Signature contains missing energy (R parity conserving) many

jets and leptons : Discovering SUSY should not be a problem!

Once SUSY is discovered, attempts will be made to connect particle physics to

cosmology

The masses and parameters will be measured, models will be investigated

Four different cosmological motivated regions of the minimal SUGRA model

have distinct signatures

Based on these measurement, the dark matter content of the universe

will be calculated to compare with WMAP/PLANCK data.

SUSY Theory at the LHC

slide35

Conclusion…

I hope not…

The search for Weapons of Mass Destruction

SUSY Theory at the LHC

ad