Dark Matter Experiments and Searches R.J.Cashmore Principal Brasenose College,Oxford and Dept of Physics,Oxford R.Cashmore Dark Matter 3 1
Dark Matter at LHC R.Cashmore Dark Matter 3 2
Satellite view of Geneva and CERN site LHC R.Cashmore Dark Matter 3 3
The Large Hadron Collider in the LEP Proton- Proton Collider Tunnel 7 TeV + 7 TeV Luminosity = 10 34 cm -2 sec -1 The Physics: Higgs boson (s) Supersymmetric Particles Quark-Gluon Plasma CP violation in B
LHC Experiments ATLAS, CMS: - Higgs boson(s) - SUSY particles -?? ALICE: Quark Gluon Plasma LHC-B: - CP violation in B CMS
Weakly Interacting Massive Particles The lightest of these new particles is an ideal candidate for dark matter Would have been created in the Big Bang A natural solution makes it extremely attractive! Particle type Fermion Particle Quark Neutrino Electron Muon Super partner Squark Sneutrino Selectron Smuon Tau Stau Now we need to detect these particles! Boson W Z Photon Wino Zino Photino Gluon Gluino Higgs Higgsino R.Cashmore Dark Matter 3 6
SUSY - sparticles SUSYMSSM and msugra parameter space cross sections decay BRs SUSY event topology and mass reach sparticle reconstruction SUSY DM particles R.Cashmore Dark Matter 3 7
MSSM Two mass parameters: m 0, m 1/2, one sign: µ Region in parameter space restricted by non-observation of SUSY signal at LEP and Tevatron Cosmological parameters reflecting cold dark mass properties Two Higgs doublets, physical scalar bosons: Neutral: h, H, A (m A and tanβ can be used as independent parameters) Charged: H ± SUSY partners of known particles: spin 0: squarks, sleptons, spin 1/2: gluinos, gauginos, Higgsino R-parity conservations: decay chains contain several neutral, invisible particles missing energy. R.Cashmore Dark Matter 3 8
SUSY - parameter space, cross sections R.Cashmore Dark Matter 3 9
Gluino/squark decay chains Typical decay chain for a massive gluino or squar Decay chain for a light gluino or squark (msugra) (MSSM) R.Cashmore Dark Matter 3 10 Vulcano 2004.6
SUPERSYMMETRY q q, qg, gg Large cross-section 100 events/day at 10 33 for: m ( q, g) 1 TeV 5σ discovery curves one year at 10 34 : up to 2.8 TeV Reach of Multijet + E T miss searches (most powerful and model-independent signature if R-parity conserved) one year at 10 33 : up to 2.3 TeV one month at 10 33 : up to 2 TeV SUSY could be found quickly plausible = typical R.Cashmore Dark Matter 3 11
m (λλ) spectrum end-point : 109 GeV exp. precision 0.3% Example of a typical chain: m (λλj) min spectrum end-point: 552 GeV exp. precision 1 % q L q χ 0 2 λ R λ λ χ 0 1 m (λλj) max spectrum threshold: 272 GeV exp. precision 2 % 0 0 ( ql, χ 2, λr, χ ) = m 1 ATLAS 100 fb -1 LHC Point 5 690, 232,157,121GeV m (λ ± j) spectrum end-point: 479 GeV exp. precision 1 % R.Cashmore Dark Matter 3 12
Benchmarking MSSMs restricted by Cosmological & Particle physics data M. Battaglia et al. R.Cashmore Dark Matter 3 13
Squark and gluino searches, reach in various topologies R.Cashmore Dark Matter 3 14
Sparticle reconstruction Jets+leptons+neutralin os in CMS R.Cashmore Dark Matter 3 15
Dilepton edges, sparticle reconstruction a) b) c) d) R.Cashmore Dark Matter 3 16
R.Cashmore Dark Matter 3 17 Sparticle reconstruction, end-points 0 1 0 2 2 2 2 2 max λ λ λ λλ m m m m m M = χ χ ( ) 0 2 0 2 0 1 0 2 2 2 2 2 max χ χ χ χ m m m m m M q q = λλ 0 1 0 2 0 1 2 max if χ χ χ m m m m m M q q q > = λλ 0 2 0 2 0 2 1 2 2 2 2 max χ χ χ m m m m m M q q = λ λ 0 2 0 1 2 2 2 2 2 max λ λ λ m m m m m M q q = χ χ g b q µ λ ± λ 0 1 χ 0 2 χ ± λ In a long cascade of decays a number of particular kinematical configurations generate end-points depending on sparticle masses, fitting these end points allows to constrain or determine these masses for ex.: largest dilepton mass: End-points depend on mass differences, thus strong correlations between masses; A fit of msugra predictions to the set of measured end-points can be performed, this yields model parameters and sparticle masses, neutralino mass and relic density, then check for consistency with terrestrial,cmb experiments.. q
Sparticle reconstruction, full chain R.Cashmore Dark Matter 3 18
Sparticle reconstruction, full chain R.Cashmore Dark Matter 3 19
Squark/gluino mass reach vs luminosity R.Cashmore Dark Matter 3 20
Dilepton edges at larger tanβ Evolution of inclusive dilepton spectra with increasing tanβ R.Cashmore Dark Matter 3 21
Observability of dilepton structures low tan β regime high tan β regime R.Cashmore Dark Matter 3 22
Sparticle reconstruction, use several edges Post-LEP SUSY benchmark point B, ATLAS/2004-007 A fit of msugra predictions to the set of measured end-points can be performed + eight other measurements Parameter Expected precision 30 fb -1 300 fb -1 Fit the best msugra point by minimizing the overall χ 2 Deduce the LSP mass (with 10% uncertainty) and relic density at the point Determine Ω χ h 2 and check for consistency with WMAP, terrestrial, astroparticle etc m 0 ± 3.2% ± 1.4% m 1/2 ± 0.9% ± 0.6% tan(β) ± 0.5% ± 0.5% 100 fb -1 0.192±0.00 0.00 5 ATLAS/2004-008 008 R.Cashmore Dark Matter 3 23 Ω χ h 2
Model-independent predictions Alternative approach to CMSSM fit to edge positions numerical solution of simultaneous edge position equations but interpretation of chain model dependent χ 0 1 Mass (GeV) χ 0 2 q L l R ATLA S Mass (GeV) ATLAS study results: Sparticle Expected precision (100 fb -1 ) q L ± 3% χ 0 2 ± 6% l R ± 9% χ 0 1 ± 12% Use approximations together with other measurements to obtain 'model-independent' estimates of Ω χ h 2, σ χp, φ sun etc. R.Cashmore Mass (GeV) Mass (GeV) Dark Matter 3 24
Dark matter: Dark Matter, SUSY, LHC (I) baryonic (machos, but represent no more than 20% of galactic halo DM), elementary particles, particle physics candidates: axion, neutralino (CDM), χ 0 parity 1 neutrino (HDM), ν τ, but too light, not more than few% of DM content the neutralino-1 (χ 0 1 ) is a viable DM candidate only so far as it is the Lightest Supersymmetric Particle (LSP) and R-parity is conserved i.e. is a stable particle DM detection: direct (ex.: relic neutralino (WIMP)-nucleon scattering) indirect (ex. relic neutralino annihilation in Earth or Sun giving, for example, two neutrinos: neutralino production, as at LHC (or the Tevatron): ATLAS, E t missing and R- R-Parity Violated LHC Point 5 (Physics TDR R-Parity Conserved R.Cashmore Dark Matter 3 25
Dark Matter, SUSY, LHC (I) DM detection: direct (ex.: relic neutralino (WIMP)-nucleon scattering) indirect (ex. relic neutralino annihilation in Earth or Sun giving, for example, two neutrinos: neutralino production, as at LHC (or the Tevatron): R.Cashmore Dark Matter 3 26
LEP neutralino limits R.Cashmore Dark Matter 3 27
Dark Matter, SUSY, LHC (II) Two questions: - do present (WMAP) constraints on DM assure SUSY detection at the LHC, and what limits do they imply on sparticle masses? - can we measure the neutralino-1 mass? R.Cashmore Dark Matter 3 28
Relic densities in LHC msugra parameter space (pre-wmap) A,H coannihilation tail bulk region
Relic densities in LHC msugra parameter space (pre-wmap) R.Cashmore Dark Matter 3 30
Relic densities in LHC msugra parameter space (pre-wmap) coannihilation tail bulk region R.Cashmore Dark Matter 3 31
SUSY dark matter and present constraints from laboratory experiments and WMAP Relic neutralino DM contours, including constraints from LEP, b sγ, g µ -2 measurements and new WMAP cosmological DM constraints favored by g µ -2 at 2σ level J. Ellis,K.A.Olive,Y.Santoso,V.C.Spanos,hep-ph/0303043 co-annihilation region example at tanβ = 10 older cosmological constraint 0.1 < Ωχh 2 < 0.3 newer cosmological constraint 0.094 < Ωχh 2 < 0.129 excluded by b sγ bulk region not allowed only this tail is left! R.Cashmore Dark Matter 3 32
SUSY dark matter and present Full tanβ range favored by g µ -2 at 2σ level J. Ellis,K.A.Olive,Y.Santoso,V.C.Spanos,hep-ph/0303043 constraints older cosmological constraint 0.1 < Ωχh 2 < 0.3 newest cosmological constraint 0.094 < Ωχh 2 < 0.129 excluded by b sγ R.Cashmore Dark Matter 3 33 Islamabad 117.2
WMAP results mapped onto m 0 vs m 1/2 plane Compatibility between WMAP results and laboratory experiments - mapping of the WMAP constraint 0.094 < Ω χ h 2 < 0.129 onto the m 0 vs m 1/2 plane for tanβ from 5 to 55 (µ > 0) J. Ellis et al. hep-ph/0303043 tanβ = 55 tanβ = 5 blue region is favored by G µ -2 (µ + ) at 2σ level R.Cashmore Dark Matter 3 34
Updated Post-WMAP Benchmarks for Supersymmetry Fine-tuned M. Battaglia et al. hep-ph/0306219 CERN TH/2003-138 Typical (A, B, C..) R.Cashmore Dark Matter 3 35
WMAP DM results and compatibility with LHC SUSY reach high tanβ = 35, µ > 0 regime m = 0.4m χ 1/2
SUSY at SLHC (I) SLHC Higher integrated luminosity brings an obvious increase in mass reach in squark, gluino searches, i.e. in SUSY discovery potential; this is not too demanding on detectors as very high E t jets, E t miss are involved, large pile-up not so detrimental with SLHC the SUSY reach is increased by 500 GeV, up to 3 TeV in squark and gluino masses Notice advantage of a 28 TeV machine. but this is just the reach, the main advantage of increased statistics should be in the sparticle spectrum reconstruction possibilities, larger fraction of spectrum, more precision, but this would require detectors of comparable performance to present ones R.Cashmore Dark Matter 3 37
Model dependent tests, sparticle masses, neutralino mass - If a viable DM candidate is found initially (events with large missing Et, stable) assume specific consistent model e.g. CMSSM / msugra. - Measure model parameters (m 0, m 1/2, tan(β), sign(µ), A 0 for msugra). - Check consistency with accelerator constraints (m h, g µ -2, b sγ etc.) - Estimate Ω χ h 2 consistency check with astrophysics (WMAP etc.) - Ultimate test of DM only possible in conjunction with astroparticle experiments measure m χ, σ χp, φ sun etc.
neutralino mass in exclusive chargino-neutralino final states the edge can be measured with better than 1 GeV precision and thus neutralino masses within this model - and where the edge is visible! R.Cashmore Dark Matter 3 39
Evolution of inclusive dilepton spectra with increasing tanβ Inclusive dilepton edges R.Cashmore Dark Matter 3 40
WMAP- DM contours and dilepton structures low tanβ regime high tanβ regime R.Cashmore Dark Matter 3 41
Sparticle reconstruction, use several edges Post-LEP SUSY benchmark point B, ATLAS/2004-007 M qll M ql (min) M ql (max) 100 fb -1 M qll (thresh) R.Cashmore Dark Matter 3 42
SUMMARY LHC and Direct Searches will allow an understanding of DM The next 4 years should be an exciting time R.Cashmore Dark Matter 3 43
Particular Thanks Alex Murphy and Tim Sumner Colleagues at the Gran Sasso Daniel Denegri and Numerous theorists R.Cashmore Dark Matter 3 44
Worldwide Scientific Collaboration 92 41 34
The History of the Universe Time Particle Accelerators are Time-Machines that bring us back to the Early Universe LHC R.Cashmore Dark Matter 3 46 BIG BANG
Perspectives for Dark Matter Searches in ATLAS Dan Tovey University of Sheffield R.Cashmore Dark Matter 3 47
Dark Matter Strategy SUSY Dark Matter studies at ATLAS will proceed in four stages: 1)SUSY Discovery phase (discussed by Marco for CMS) success assumed! 2)Inclusive Studies (measurement of SUSY Mass Scale, comparison of significance in inclusive In this channels). talk focus on Stages 2, 3 and 4 3)Exclusive studies and interpretation within specific model framework (e.g. Constrained R.Cashmore Dark Matter 3 48
Following any discovery of SUSY next task will be to test broad features of potential Dark Matter candidate. Non-pointing Question 1: Is R-Parity photons from χ 0 1 Gγ Conserved? Inclusive Studies GMSB Point 1b (Physics TDR) If YES possible DM candidate ATLAS LHC experiments sensitive only to LSP lifetimes < 1 ms (<< t U 13.7 Gyr) R-Parity Violated LHC Point 5 (Physics TDR) ATLAS Question 2: Is the LSP the lightest neutralino? Natural in many MSSM models If YES then test for consistency with astrophysics If NO then what is it? R-Parity Conserved e.g. Light Gravitino DM from GMSB models (not considered here) R.Cashmore Dark Matter 3 49
If a viable DM candidate is found initially assume specific consistent model e.g. CMSSM / msugra. Model-Dependent Tests msugra A 0 =0, Measure model parameters (m 0, m 1/2, tan(β), sign(µ), A 0 for CMSSM). Disfavoured by BR (b sγ) = (3.2 ± 0.5) 10-4 (CLEO, BELLE) Ellis et al. hep-ph/0303043 Favoured by g -2 µ (E821) Assuming δα µ = (26 ± 10) 10-10 from SUSY (± 2 σ band) 0.094 Ω χ h2 0.129 (WMAP) Forbidden (LSP = stau) R.Cashmore Dark Matter 3 50 Check consistency
Terrestrial Dark Matter Terrestrial Dark Matter experiments: Experiments 1.E-03 Direct searches for elastic scattering of Dark Matter particles from atomic nuclei (σ χp ) Indirect searches via selfannihilation products from e.g. centre of sun (e.g. high energy neutrino flux φ sun ) Direct search experiments can measure neutralino 1.E-04 1.E-05 1.E-06 1 10 100 1000 10000 Mass GeV R.Cashmore Dark Matter 3 51 χ-nucleon cross section pb 10-3 10-4 10-5 10-6 CDMS ZEPLIN I DAMA IGEX EDELWEISS Current world-best limits (ZEPLIN-I, EDELWEISS): σ χp < 10-6 pb (m χ 100 GeV)
Measuring CMSSM First indication of CMSSM parameters from inclusive channels Parameters Compare significance in jets + E T miss + n leptons channels Detailed measurements from exclusive channels when accessible. Point m 0 m 1/2 A 0 tan(β) sign(µ) LHC Point 5 100 300 300 2 +1 SPS1a 100 250-100 10 +1 Sparticle Mass (LHC Point 5) Mass (SPS1a) q L 690 GeV 530 GeV Consider χ here two specific 0 2 233 GeV 177 GeV l example R 157 GeV 143 GeV χ points studied 0 1 122 GeV 96 GeV previously: LHC Point 5 (A 0 =300 GeV, tan(β)=2, µ>0) Point SPS1a (A 0 =-100 GeV, tan(β)=10, µ>0) ATLAS R.Cashmore Dark Matter 3 52
Fit reconstructed Mass mass Measurements combinations to obtain parameters Helped by p long SUSY p cascade decay chains Starting point usually χ 0 2 decays χ 0 to llχ 0 2 1 (below) or hχ 0 1 g q χ 0 1 l R q q l l R.Cashmore Dark Matter 3 53 Two neutral LSPs escape from each event
When kinematically accessible χ 0 2 can undergo sequential two-body decay to χ 0 1 via a rightslepton (e.g. LHC Point 5). Dilepton Edge Measurements Results in sharp OS SF dilepton invariant mass edge sensitive to χ 0 2 e + e - + µ + µ - Point 5 ATLAS R.Cashmore Dark Matter 3 54 l 30 fb -1 atlfast Physics TDR l l χ 0 1 e + e - + µ + µ - - e + µ - - µ + e - 5 fb -1 FULL SIM ATLAS Modified Point 5 (tan(β) = 6)
Measurements Dilepton edge starting point Involving for reconstruction Squarks of decay chain. Make invariant mass combinations of leptons and jets. Gives multiple constraints on combinations of four masses. Sensitivity to individual sparticle masses. q L q χ 0 2 l llq edge 1% error (100 fb -1 ) l l χ 0 1 lq edge 1% error (100 fb -1 ) q L q χ 0 2 b h llq threshold 2% error (100 fb -1 ) b χ 0 1 bbq edge 1% error (100 fb -1 ) TDR, Point 5 TDR, TDR, TDR, Point 5 ATLAS Point 5 ATLAS Point 5 ATLAS ATLAS R.Cashmore Dark Matter 3 55
Measuring CMSSM Parameters Within CMSSM most direct approach is to calculate edge positions using sparticle masses and formulae Point m (using a global fit). 0 m 1/2 A 0 tan(β) sign(µ) LHC Point 5 100 300 300 2 +1 SPS1a 100 250-100 10 +1 Parameter Expected precision 30 fb -1 300 fb -1 m 0 ± 3.2% ± 1.4% m 1/2 ± 0.9% ± 0.6% tan(β) ± 0.5% ± 0.5% R.Cashmore Dark Matter 3 56
Measurement precision for Ω χ h 2 depends strongly on region of parameter space. e.g. Ω χ h 2 Micromegas 1.1 = 0.2247 ± (Belanger et al.) 0.0035 (Point 5) + ISASUGRA 7.58 Point 5 e.g. Ω χ h 2 = 0.111 ± 0.018 ATLAS (SPS1a) 300 fb -1 Relic DensityBaer et al. hep-ph/0305191 SPS1a Battaglia et al. hep-ph/0306219 (based on ATLAS study of SPS1a) LHC Point 5: 10σ error (300 fb -1 ) LEP 2 SPS1a: 2σ error (100 fb -1 ) (Battaglia et al. hep-ph/0306219) σ χp =10-11 pb σ χp =10-10 pb σ χp =10-9 pb No REWSB R.Cashmore Dark Matter 3 57
Dark Matter Sensitivity Also use model parameters to predict signals observed in terrestrial dark matter searches (Point 5) Direct detection (assumed µ<0) ATLAS σ χp DarkSUSY 3.14.02 e.g. σ χp (Gondolo = (1.3 et al.) ± 0.3) x 10-9 ATLAS + ISASUGRA 7.58 pb Neutrino flux from φ sun sun (µ<0) φ sun 8 x 10 7 km -2 yr -1 (spread in A 0 ) LEP 2 Baer et al. hep-ph/0305191 LHC Point 5: 10σ error (300 fb -1 ) SPS1a: 2σ error (100 fb -1 ) (Battaglia et al. hep-ph/0306219) σ χp =10-11 pb σ χp =10-10 pb σ χp =10-9 pb No REWSB R.Cashmore Dark Matter 3 58
Alternative 'Model-Independent' approach to CMSSM Predictions fit to edge positions. Numerical χ solution of simultaneous edge 0 1 l R position equations. q Note interpretation of chain L ± 3% model dependent. ATLAS Mass (GeV) χ 0 2 ATLAS Mass (GeV) q L ATLAS ATLAS Sparticle Expected precision (100 fb -1 ) χ 0 2 ± 6% l R ± 9% χ 0 1 ± 12% Similar process for τ 1 mass at high tan(β) Use approximations together with other measurements to obtain 'model-independent' estimates of Ω χ h 2, σ χp, φ sun etc. Mass (GeV) Mass (GeV) R.Cashmore Dark Matter 3 59
'Focus point' region (significant h component to LSP ): v. difficult, need m(χ 0 1 ), µ, m A tan(β) etc. + m(t) to high precision. More study needed 'Bulk' region (tchannel slepton exchange - LSP mostly Bino): need m(χ 0 1 ), m(l R ), m(τ 1 ). 'Bread and Butter' region for LHC Expts. Relic Density msugra Scenarios A 0 =0, Ellis et al. hep-ph/0303043 Representative MSSM scenarios present within e.g. CMSSM χ 0 1 χ 0 1 Slepton Coannihilation region (LSP pure Bino): need m(χ 0 1 ), m(τ 1 ). Small mass difference makes measurement difficult however. Also 'rapid annihilation funnel' at Higgs pole at high tan(β): m(χ 0 1 ), m A, µ, tan(β), m(t) etc. needed. R.Cashmore Dark Matter 3 60 l R l l χ 0 1 τ 1 τ τ 1 γ/z/h
Dark Matter Searches Scalar elastic neutralino-nucleon scattering (DM direct detection) dominated by Higgs and squark exchange σ χp function of squark mass, M(χ 0 Scalar (spin independent) 1), m A, tan(β) and µ (χ 0 couplings (tree-level) 1 composition). Jungman, Kamionkowski and Griest, Phys. Rep 267:195-373 (1996) R.Cashmore Dark Matter 3 61
tan(β) via H/A m A = 300 GeV Other Measurements Further input regarding the weak scale SUSY parameters needed. m A ATLAS measured from direct search (although difficult for m A > 600 GeV). H/A ττ m A = 300 GeV Physics TDR ATLAS Higgsino mass parameter µ (governs higgsino content of χ 0 1) measurable from heavy neutralino edges. tan(β) accessible from σ.br(h/a ττ,µµ ττ,µµ) or BR(χ 0 2 ττ 1 )/BR(χ 0 2 ll R ). More work needed. R.Cashmore Dark Matter 3 62
Summary Following a SUSY discovery ATLAS will aim to test the SUSY Dark Matter hypothesis. Conclusive result only possible in conjunction with astroparticle experiments (constraints on LSP life-time). Estimation of relic density and direct / indirect DM detection cross-sections in modeldependent This scenario would be will major be triumph first goal. for both Particle Physics and Cosmology! Less model-dependent measurements will follow. R.Cashmore Dark Matter 3 63 Ultimate goal: observation of neutralinos at
Earth from Apollo 17 (NASA) R.Cashmore Dark Matter 3 64
The Fundamental Particles Leptons υ e 0.0 MeV 0 e 0.5 MeV -1 e e υ µ 0.0 MeV 0 e 0.1 GeV -1 e µ υ τ 0.0 MeV 0 e 1.8 GeV -1 e τ Quarks uuu 5.0 MeV +2/3 e 10.5 MeV -1/3 e ddd ccc 1.3 GeV +2/3 e 0.2 GeV -1/3 e sss ttt 175 GeV +2/3 e 4.3 GeV -1/3 e bbb R.Cashmore Dark Matter 3 65