Dark The LHC Yi Cai KITPC, Beijing June 20, 2012 June 2012 Yi Cai, SJTU Disclaimer Unspoken rules( ): your own work Unfortunately none is presented here. Please dont mobilize the masses to ban me!( ) Yi Cai, SJTU Why do we care? Astrophysical evidences Rotation curve Bullet cluster Cosmic microwave background Energy budget Yi Cai, SJTU What could it be? Modify gravity itself? MACHOs? Hot dark matter? Cold or warm dark matter? Axions Gravitinos WIMPs Yi Cai, SJTU What can we do? Theory: maybe already more than enough on the market Experiment Direct detection Indirect detection Collider experiments Yi Cai, SJTU Comparison Direct Local DM densities Velocity distribution Less sensitive to spin Indirect Profile of DM halo Cosmic ray propagation Collider Light DM Spin dependent Yi Cai, SJTU LHC Basics Location:the Swiss and French border Depth: m Circumference: 27km Beam energy: 7? TeV Yi Cai, SJTU What can we see? Standard signals Missing transverse energy Jets Leptons Photons New physics: a needle buried deep in a haystack Challenge: control the background Yi Cai, SJTU Model Dependent Approach The most studied theories Supersymmetry Extra dimensions Little Higgs Signature: new stuff+MET Yi Cai, SJTU SUSY Basics Particle number: doubled Parameters > 100 in the MSSM Various SUSY breaking mechanisms mSUGRA AMSB GMSB Split SUSY DM candidate Yi Cai, SJTU mSUGRA 5 parameters: m0, m1/2, tanbeta, A0,sign(mu) Different regions Bulk region Focus point Co-annihilation region Rapid annihilation funnel Yi Cai, SJTU Bulk Region Annihilation via slepton exchange Solve from endpoints in dilepton mass and dilepton+jet mass, min value of dilepton+jet mass and max value of single lepton+jet mass Yi Cai, SJTU Pros and Cons very sensitive pheno changes drastically with modifications Only DM candidates found Yi Cai, SJTU Model independent Assumption Fermionic dark matter & heavy mediator Effective operators with a universal cutoff Two parameters: DM mass and the cutoff Yi Cai, SJTU CMS Pair production Requirements: Photon: Pt > 145 GeV In the central region || 130 GeV Remove events jet with Pt > 40 GeV and || < 3 nearby tracks or pixel stubs significant hadronic activity significant electromagnetic calorimeter activity Aggressive isolation-based clean-up. Yi Cai, SJTU Major Background Bkg from pp collision pp-> Z-> irreducible pp->W->e e misidentified as photon pp->jets->+MET j mimics , MET from j mis-measurement pp->+jet MET from j mis-measurement pp->W->l l escapes pp-> mis-measured Bkg also comes from cosmics, neutron and beam halo Yi Cai, SJTU Limits CLs limits calculated for an integrated luminosity of 4.67 fb^- Assumption:cross section scales as ^4 SI SD Yi Cai, SJTU Combined with Direct Detection Yi Cai, SJTU Monojet Event selection MET>200 GeV (>350 for DM search) # of jets 1 or2 pT(1) >110 GeV, ||30 GeV (1,2)350 GeV, 1124101 bkg, 1142 data Yi Cai, SJTU Monojet and Monophoton Yi Cai, SJTU Then? Other operators? Mediator not so heavy? One more parameter. A special case: Higgs portal With indirect search? More!! Yi Cai, SJTU Summary DM is an important topic beyond the Standard Model. Various DM searching strategies have their own pros. and cons. LHC can in principle produce DM, place stringent constraints or even find good DM candidates. Future LHC data may eventually shed some real light on this puzzle. Yi Cai, SJTU References arXiv: , , , , , , JHEP 1012:048(2010) Phys. Rev. D82: (2010)