The search for missing energy events at the LHC and ...Dark Matter 2012 Valery Andreev (UCLA) 6...

The search for missing energy events at the LHC and implications for dark matter search

(ATLAS and CMS)

Valery P. Andreev UCLA

representing the CMS collaboration

10th UCLA Symposium on Sources and Detection of Dark Matter and Dark Energy

in the Universe February 23, 2012 Marina del Rey, California

Dark Matter 2012 Valery Andreev (UCLA) 2

Outline

•  Introduction •  LHC, ATLAS and CMS detectors •  SUSY searches at LHC •  ATLAS and CMS results implications •  Conclusions

Lightest Supersymmetric Particle (LSP) ! is a possible candidate for the Cold Dark Matter "

Supersymmetry (SUSY)

•  to solve the hierarchy problem (EWK scale GUT scale) •  a framework for the unification of particle and gravity •  a broken symmetry •  provided R-parity conservation

–  pair production –  dark matter candidate (LSP = stable, neutral, weakly interacting)



Typical SUSY decay chains Typical event topology – •  missing energy •  multiple hadronic (b) jets •  number of leptons


LHC event rates

SUSY at 10-10 inelastic cross section


Large Hadron Collider (LHC)!

ATLAS

CMS

cm-2s-1 cm-2s-1

CMS 7 TeV Run Status, 2011 Maximum luminosity = 3.54 1033 cm-2s-1

Recorded luminosity = 5.2 fb-1 ATLAS 7 TeV Run Status, 2011 Maximum luminosity = 3.6 1033 cm-2s-1

Recorded luminosity = 5.25 fb-1


The CMS detector

Onion structure: • Tracker • Calorimeters • Muon system

Precise e, µ, γ, jets, ET

Efficient b tagging, τ detection


Muon detector

The ATLAS detector!

TRT and Si tracker

Tile CAL LAr CAL

Toroids 2T solenoid

Length: 46 m

Diameter: 22 m

Weight: 7,000 t

for precise and efficient measurements

ATLAS & CMS: first, rediscover the Standard Model


•  important for reliable background estimate in New Physics searches

SUSY search: analysis technology

•  define signal region (SR) to maximize sensitivity –  discriminating variables ( , meff, razor, …)

•  background estimate –  data-driven (control regions (CR), data vs MC) –  transfer factor , from data or MC

•  no excess of data over SM expectation, so far set a limit (model-independent or simplified model, CMSSM, MSUGRA, GMSB, …)


€

SRCR

€

TmissE

…, while each time hoping for an excess

Missing transverse energy


•  crucial variable in searches with R-parity conservation

an example: search in all-hadronic events with missing energy

(GeV)TH

0 500 1000 1500 2000 2500 3000 3500

Even

ts /

100

GeV

-110

1

10

210

310Data Bkg. expectation from MC

)+Jets!W(l )+Jets!!Z(

+JetsttQCD Susy LM4

= 7 TeVs, -1CMS Preliminary, L = 1.1 fb

(GeV)TH

0 500 1000 1500 2000 2500 3000 3500

Even

ts /

100

GeV

-110

1

10

210

310

(GeV)TH

0 500 1000 1500 2000 2500 3000 3500

Even

ts /

100

GeV

-110

1

10

210

310

(GeV)TH

0 500 1000 1500 2000 2500 3000 3500

Even

ts /

100

GeV

-110

1

10

210

310

(GeV)TH

0 200 400 600 800 1000 1200

Even

ts /

20 G

eV

-110

1

10

210



+JetsttQCD Susy LM4


(GeV)TH

0 200 400 600 800 1000 1200

Even

ts /

20 G

eV

-110

1

10

210

310

(GeV)TH

0 200 400 600 800 1000 1200

Even

ts /

20 G

eV

-110

1

10

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310

(GeV)TH

0 200 400 600 800 1000 1200

Even

ts /

20 G

eV

-110

1

10

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310

(GeV)TH

0 200 400 600 800 1000 1200

Even

ts /

20 G

eV

-110

1

10

210

310

) (GeV)TH+T

( = HeffM

0 500 1000 1500 2000 2500 3000 3500 4000

Even

ts /

100

GeV

-110

1

10

210



+JetsttQCD Susy LM4


) (GeV)TH+T

( = HeffM

0 500 1000 1500 2000 2500 3000 3500 4000

Even

ts /

100

GeV

-110

1

10

210

310

) (GeV)TH+T

( = HeffM

0 500 1000 1500 2000 2500 3000 3500 4000

Even

ts /

100

GeV

-110

1

10

210

310

CMS: PAS-SUS-11-004

ATLAS: arXiv:1109.6572

CMS: some SUSY searches results in CMSSM (m0,m1/2) plane


•  2010 vs 2011 exclusion contours, the area below the curves is excluded

m0 and m1/2 are universal scalar and gaugino masses, respectively

Search for SUZY in Z+jets+MET events


CMS: full 2011 data sample analyzed, 4.7 pb-1 ; two approaches 1) MET 2) JetZBalance

Simplified model

MET

JZB

Search for Stop and Sbottom at LHC


ATLAS: direct and gluino mediated production considered, 2 pb-1 source: X. Poveda, LHC Physics seminar, 14 Feb 2012; ATLAS-CONF-2012-002,3,4,5; arXiv:1112.3832

ATLAS SUSY searches status (exclusion limits)


CMS: SUSY searches results


P1

P2

g̃

g̃

q

q

!̃0

!̃0

q

q

P1

P2

q̃

q̃

q

!̃0

!̃0

q

excluded mass scale in Simplified Model spectra

ATLAS searches status (II) (exclusion limits)



Compatibility between laboratory searches and WMAP results

tanβ 55

5

J.Ellis,K.A.Olive,Y.Santoso,V.C.Spanos, hep-ph/0303043

favored by g – 2 (µ+) µ

at 2-σ level


Compatibility between laboratory searches and WMAP results

tanβ 55

5

J.Ellis,K.A.Olive,Y.Santoso,V.C.Spanos, hep-ph/0303043

favored by g – 2 (µ+) µ

LHC: ATLAS & CMS results implication for Dark Matter search


Dark matter production in association with mono-jet

P.J.Fox, R. Harnik, J. Kopp, Y. Tsai arXiv: 1109.4398v1, 20 Sep 2011

LHC: ATLAS & CMS results implication for Dark Matter search


Dark matter production in association with mono-photon

P.J.Fox, R. Harnik, J. Kopp, Y. Tsai arXiv: 1109.4398v1, 20 Sep 2011


SUSY spectroscopy Gluino, sbottom and squark reconstruction

reconstruction starts with χ20 → l+l-χ1

0

assuming


Conclusions •  Dark Matter provides an indication of a New Physics

–  SUSY LSP is a candidate for Dark Matter •  No signs of SUSY at LHC so far

–  a plenty of new (full statistics) measurements will be released at Moriond 2012. Stay tuned !

•  2012 LHC will run with increased energy of 8 TeV –  to deliver 15 fb-1 per experiment (ATLAS, CMS)

•  If there is a ~ TeV-scale SUSY dark matter particle ⇒ LHC will discover SUSY and allow detailed studies and parameters determination

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The search for missing energy events at the LHC and ...Dark Matter 2012 Valery Andreev (UCLA) 6...

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