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Supersymmetry at LHC and beyond. ---Ultimate tagets--- Mihoko M. Nojiri YITP, Kyoto University. Why collider ??. Best way to 1. See existence of superpartners 2. Supersymmetric relations 3. Soft mass measurements Understand SUSY breaking mechanism ] Interactions at high scale

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Supersymmetry at lhc and beyond

Supersymmetry at LHC and beyond

---Ultimate tagets---

Mihoko M. Nojiri

YITP, Kyoto University

Why collider
Why collider ??

Best way to

1. See existence of superpartners

2. Supersymmetric relations

3. Soft mass measurements

Understand SUSY breaking mechanism

] Interactions at high scale

Impacts on the other physics

B, LFV, Dark matter

1 the existence
1. The existence

Large cross section.

No SM backgrounds

Search up to 2TeV squark or


1000 events/year

for 1TeV squarks and gluinos

We should try to extract

ALL physics information

from THIS experiment!

gaugino mass

(Not only) famous SPS1a …

scaler mass

2 supersymmetric relations i can t wait until lc operation
2. Supersymmetric relations (I can’t wait until LC operation)

  • chiral nature

  • No new dimensionless coupling


Chirality and m jl distributions richardson 2001 barr 2004 kawagoe goto nojiri 2004
chirality and m(jl) distributionsRichardson (2001), Barr(2004), Kawagoe Goto Nojiri(2004)

  • Chirality of slepton appears in m(jl) distribution

    • Right handed lepton goes same direction to the jet direction

    • Right handed anti-lepton goes opposite to jet

      Charge asymmetry!

Mc simulations left and right sleptons
MC simulations (left and right sleptons)

Kawagoe, Goto, Nojiri(2004)

Smuon l r mixing goto s talk
smuon L-R mixing(Goto’s talk)

visible in wide parameter regions

Proof of smuon F term mixing

Other examples?( m(bb) distribution of gluino->stop top)

Hisano, Kawagoe,MMN 2003

3 soft mass measurement collider signature of susy easy to hard

Long lived NLSP(~O(10m))

Neutral LSP





Too heavy


Gauge mediation

Supergravity and the variants





3.Soft mass measurement Collider signature of SUSY “easy” to “hard”

Easy case signature with long lived nlsp
“Easy case”Signature with long lived NLSP

  • Shorter life time (<O(1cm))

    lots of leptons and photons

    endpoint analysis.

  • Charged Long Lived NLSP

    • TOF for charged track

      • Dt~1ns at 10m-20m

    • Full reconstruction

  • Neutral Long Lived NLSP

    • No track

    • Fine time resolution at ECAL cDt~3cm at O(1m)

    • Gravitino momentum and decay position can be solved with the time info

      (Kobayasi, Kawagoe, Ochi,MMN(2003)

      Kawagoe’s talk)

  • No systematic study yet.

Hinchliffe and Paige

Moderate cases

Long lived NLSP(~O(10m))

Neutral LSP

sfermion<gaugino(2 body)

gaugino<sfermion(3 body )



Too heavy

Time delay Signals

TOF for charged track

Arrival time(photon)

Endpoint analysis(Giacomo’s talk)

Lepton mode

Tau and b modes

Jet selection

No good ideas


Summary of endpoint study at sps1a
Summary of endpoint study at SPS1a

Based on the endpoint analysis, sparticle

masses may be understood very well. The lepton channels are important.

LSP mass [dark matter mass

Slepton mass, neutralino mass[Dark matter density

Limitations of the end point method
Limitations of the end point method

  • unkonwn LSP momentum

    • No kinematical constraint even though you know the masses

  • Waste of statistics

    • Events off the end points are not used.

    • Need statistics enough to see the end point.

  • signals from different cascades to make a single broad end point.

Mass relation method apply mass shell constraints to solve events
Mass relation method apply mass-shell constraints to solve events

  • Full event reconstructions! we see peaks.

  • Use all events for mass and distribution study.

  • “In principle”, a few events are enough to determine the masses and LSP momentum (up to jet energy resolutions)

  • Kinematical constraints available.

Nojiri, Polesello, Tovey hep-ph/0312318 (Les Houches)

Supersymmetry at lhc and beyond

Example of mass relation method

5 Dim mass space M

A event<-> 4 dim hypersurface

in M

gluino mass

For simplicity Assume we know mass of

sbottom mass

Each event corresponds to a curve in the mass plane

Two events is enough to give the masses, and

LSP momentum.

a distribution of the solution in the previous plot

Sbottom mass determination plot lighter solution for fixed gluno mass
Sbottom mass determination(plot lighter solution for fixed gluno mass)



Background level







Sbottom2 contribution

Kawagoe, MMN, Polesello…

Msugra and 3 rd generation mass spectrum
mSUGRA and 3rd generation mass spectrum

  • FCNC constraints are weak for 3rd generation.

    non-universal squark and slepton masses for the 3rd generation.

  • Yukawa RGE running breaks the universality at at the GUT scale.


  • Left-right squark mixing

    SPS1a tanb=10 sbottom mass 492GeV

    tanb=20 479GeV

  • Implication to higgs mass, B physics….

A event a probability density for true masses l
A event aprobability density for true masses(L)

log L(1) + logL(2) + log L(3)+ logL(4)

= log L(~Dc2)



Spin off from the mass relation method
Spin off from the mass relation method

Neutralino momentum also solved.

Transverse momentum

of the 2nd LSP

  • For the 2nd LSP, transverse

  • Momentum is known

  • a event Corresponds to 1 dim line in the

  • mass space.

  • Even shorter cascade can be solved.

2nd LSP

Total missing


reconstructed LSP


New channels using missing pt hep ph 0312317 18
New channels using missing pT (hep-ph/0312317,18)

Example I

chargino reconstruction

Example II heavy higgs reconstruction 4lepton channel


Getting more difficult

Large tanb


squark->gluino jets

Then 3 body

Losing statistics

Tau mode dominate.

(giacomo’s talk)

All squarks decays into gluino, information loss

Jet selection? B modes?

“getting more difficult”

  • Degenerated (no hard jets…)

Handle signal without leptons
Handle signal without leptons

  • Sometimes SUSY signature is not hard leptons.

  • Still stop, sbottom may be lighter than other sparticles

    due to top Yukawa RGE

    SUSY -> events with many b jets.

  • Gluino decays dominantly into

    btc- ,bbc0and ttc0

  • b tagging efficiency is 60%

    Looking for non-b jets from SUSY decay is difficult.

    many QCD jets

Reconstructing top from gluino decays
Reconstructing top from gluino decays

  • t a bW a bjj

  • N(jet) a7 typically. Many BG

    to W a jj

  • Background to t abWabjjis estimated from events in the



    mjj>mW+15 GeV.

  • Reconstructed top quarks are used to study tb distribution .

Supersymmetry at lhc and beyond

Difference between two body and three body

Branching ratio is biggest for tb final state.

SPS1a: edge with DMtb ~4GeV for 100fb-1

SPS2 :(focus points M=300GeV), distribution may reflect

But cross section is small….

(from the plots in

Hisano, Kawagoe, Nojiri PRD68.035007)

1000 fb-1 but cut is not optimized


  • LHC starts soon ! (2007, I hope!)

  • SUSY is polarized. m(jl) distribution is

    easy to study. Want more example. Jet charge


  • New “full reconstruction” technique. It works even for small statistics.

    • Note: If event contains many neutrinos, the method cannot be applied. Go back to the end points?

    • How to combine end points and “full reconstructions”

  • We need more thoughts and works. “Crazy theorists” are especially welcome.

Supersymmetry at lhc and beyond

LHC: gluino and two sbottom masses

For the wino like second –lightest neutralino

If WEAK SUSY parameters are known

precisely enough, decay pattern of sbottom

may be understood as

the function of q.

Hisano, Kawagoe, Nojiri (for LHC/LC)

Precise susy with lhc lc
Precise SUSY with LHC/LC

  • LC can change “silver” to “gold”

    • Interaction measurements

    • Checking universality O(1)%

      O(10%) for GUT scale scalar masses.

  • Need more precise estimation of running from GUT to weak scale

  • Fix low energy parameters for DM, Higgs, B, LFV. Ex. O(1%) thermal relic density