1Alan Barr PASCOS 09 PASCOS 2009 DESY 9 July 2009 …AT THE LHC DARK MATTER … Alan Barr University of Oxford On behalf of the ATLAS and CMS collaborations

2Alan Barr PASCOS 09 You may have noticed there is a new collider starting operation

3Alan Barr PASCOS 09 Motivation stop higgs +SUSY Log 10 ( μ / GeV) 1/ α The value of prejudice rapidly decreasing

4Alan Barr PASCOS 09 The machine … km circumference 9300 magnets Four experiments (two general purpose) km circumference 9300 magnets Four experiments (two general purpose) ATLAS CMS Proton-proton – controlled environment – up to 14 TeV – 10 9 collisions/second – ~ decade operation Proton-proton – controlled environment – up to 14 TeV – 10 9 collisions/second – ~ decade operation

5Alan Barr PASCOS 09 Segment of 4π detector

6Alan Barr PASCOS 09

7Alan Barr PASCOS 09 Beam splash CMS

8Alan Barr PASCOS 09 Events… From Steve Meyers More info: More info:

9Alan Barr PASCOS 09 Dark Matter … Z 2 ? Events build from blobs with 2 “exotic legs” A pair of cascade decays results Complicated end result Events build from blobs with 2 “exotic legs” A pair of cascade decays results Complicated end result Time standard 2 exotics Production part Time standard heavy exotic lighter exotic Decay part Time Complete “event” = exotic = standard Candidates include: {Supersymmetry, UED, Little Higgs} + appropriate parity

10Alan Barr PASCOS 09 Assume R-parity Look for: –Jets from squark & gluino decays –Leptons from gaugino & slepton decays –Missing energy from (stable) LSPs Example SUSY search “Typical” SUSY spectrum Missing energy + Jets Mass (GeV)

11Alan Barr PASCOS 09 Cross-sections etc Lower backgrounds Higher backgrounds “Rediscover” “Discover” ZZ WW Prospino

12Alan Barr PASCOS 09 Caveats Current public results mostly: –√ S = 14 TeV –∫ L ≥ 1 fb -1 –no pile-up † Initial conditions will be different Work in progress for smaller √ S, ∫ L –10 TeV – pb -1 Current public results mostly: –√ S = 14 TeV –∫ L ≥ 1 fb -1 –no pile-up † Initial conditions will be different Work in progress for smaller √ S, ∫ L –10 TeV – pb -1 † some CMS physics TDR results include 5 pile-up events

13Alan Barr PASCOS 09 Typical search: inclusive distributions Jet p T > {100, 50,50,50} GeV p T > 100 GeV p T > 0.2 m eff S T > 0.2 Δ φ (p T,j) > 0.2 j = {1,2,3} No e or μ m eff > 800 GeV Jet p T > {100, 50,50,50} GeV p T > 100 GeV p T > 0.2 m eff S T > 0.2 Δ φ (p T,j) > 0.2 j = {1,2,3} No e or μ m eff > 800 GeV Signal BG Example 4 jet + p T distribution

14Alan Barr PASCOS 09 Standard Model backgrounds Statistics limited –Also use: –W ( μ ) + jet –γ + jet Statistics limited –Also use: –W ( μ ) + jet –γ + jet Measure in Z -> μ μ Use in Z -> νν R: Z -> νν B: Estimated R: Estimated

15Alan Barr PASCOS 09 W, t backgrounds Search region Control Region Good match to “true” background These are examples only Lots of detail about Z, top, QCD, detector BGs in further reading

16Alan Barr PASCOS 09 Multiple channels for discovery Different final states accessible Below the lines = discovered 1 fb -1, 14 TeV Systematics include BG determination

17Alan Barr PASCOS 09 Measuring masses Large literature exists Practical methods will be put to the test Large literature exists Practical methods will be put to the test SUS l + l - : p T > 10 GeV, | η |<2.4 3 jets | η | 120,80,30 GeV p T miss > 200 GeV l + l - : p T > 10 GeV, | η |<2.4 3 jets | η | 120,80,30 GeV p T miss > 200 GeV m ll = ½ m ll max (1 – cos θ )

18Alan Barr PASCOS 09 Dark matter relic density? “Predict” relic density of observed LSPs Caveats: –lifetimes beyond detector? –optimistic case (light sparticles) –many annihilation modes need to be checked “Predict” relic density of observed LSPs Caveats: –lifetimes beyond detector? –optimistic case (light sparticles) –many annihilation modes need to be checked Polesello Tovey Drees, Kim, Nojirihep-ph/ Polesello, Tovey hep-ph/ (cMSSM) Nojiri, Polesello, Tovey hep-ph/ (MSSM) Moulin et al.arXiv: (Focus point) Drees, Kim, Nojirihep-ph/ Polesello, Tovey hep-ph/ (cMSSM) Nojiri, Polesello, Tovey hep-ph/ (MSSM) Moulin et al.arXiv: (Focus point) f f

19Alan Barr PASCOS 09 ATLAS CERN-OPEN arXiv: To find out more… New results will appear at: Results for EPS and summer conferences in progress New results will appear at: Results for EPS and summer conferences in progress CMS CERN-LHCC J.Phys.G34: ,2007

20Alan Barr PASCOS 09 Conclusions

21Alan Barr PASCOS 09 Extras

22Alan Barr PASCOS 09 Importance of detailed detector understanding Simulation shows events with large fake missing energy Vital to remove these in missing energy tails Large effort in physics commissioning Simulation shows events with large fake missing energy Vital to remove these in missing energy tails Large effort in physics commissioning Lesson from the Tevatron Et(miss)

23Alan Barr PASCOS 09 Spin measurements… Neutralino spin from angles in decay chains l+l+ ~ θ q q _ l-l- ~ Slepton spin from angles in Drell-Yan production