Outline Evidence for dark matter Dark matter candidates: WIMPs, the LSP Direct and indirect detection methods Determining the relic density from signals What information about the wimp is required? A method to compute a wimp mass from dark matter experiments alone If the wimp is the LSP, What collider data is required What we can learn about the MSSM without colliders Summary and outlook

Evidence for Dark Matter 1933: Fritz Zwicky studies the coma cluster Finds nearly 90% of the mass 'spherically distributed.' In the 1970s, more rotation curves were measured. The problem was found to be universal. Rotation curve for M33 (from astro-ph/9909252)

Dark Matter: Not a Problem! Plenty of candidates. Astronomy: 'Jupiters,' white dwarfs, black holes… Neutrinos? Particle Physics: The axion Weakly interacting massive particles (WIMPs): the LSP, right-handed neutrinos, CHAMPs, self-interacting dark matter (SIDM), wimpzillas, the lightest Kaluza-Klein particle, superweakly interacting massive particles (superWIMPs)…

Why WIMPs? Plenty of candidates. Almost any extension of the Standard Model of particle physics introduces massive particles that interact only weakly (otherwise we would have seen them already) How many wimps were produced in the big bang? estimate of the thermal production in early universe; 'freeze out' This gives weak scale:

How to Observe a WIMP Direct detection Indirect detection (DAMA, ZEPLIN, DRIFT, EDELWEISS, CDMS, ANAIS, CASPAR, CRESST, CUORE, GENIUS, HDMS, IGEX, LIBRA, MACHe3, Majorana, NAIAD, ORPHEUS, Picasso, ROSEBUD, UKDMC, &etc). Indirect detection Neutrinos from the sun/earth (AMANDA, ANTARES, IceCube, MACRO, Super-Kamiokande, Nestor, BAIKAL, DUMAND, &etc) Antimatter excess/cosmic rays (AMS, BESS, CAPRICE, GLAST, IMAX, NINA, PAMELA, &etc)

No-Lose Theorem vs. Our Ability to Win What is the cosmological relevance of discovering a wimp? No lose theorem: we can directly detect very small wimp components of the dark matter in some models. Therefore, we will not know the cosmological significance of a discovered wimp until we know its relic density [Dūda, Gelmini, Gondolo, Edsjö, Silk, etc.]

Direct Detection Rates Signal rate for wimp-scattering at energy Q Given the halo model, wimp mass, and signals at different energies from different detector materials, we can solve for

What if we Don't Know the Mass? Notice that fp,n and ap,n are constants. For each independent (minimal) set of data, we can compute these constants if the mass were known. Let us define the consistency function where i,j represent a minimal set of data used to compute the constants using the assumed value for m

Weighing a WIMP Clearly, (m) should have a minimum at the true mass. (Independent determinations of the constants should agree) (m) as a function of m for ATLAS SUSY point 2

Measuring the Density Therefore, direct detection experiments can be used to determine Notice that we must have a model which tells us fp, fn, ap, or an before we can determine ! (This isn't helped with indirect data for similar reasons)

Supersymmetry and the LSP In R-parity conserving supersymmetric standard models, the lightest super particle (LSP) will be stable: an excellent dark matter candidate! For most models within current constraints, the LSP is the lightest mass eigenstate of the neutralino: In the basis we have, So the LSP is

LSP Interaction Parameters Recall that we must compute fp, fn, ap, or an in order to measure  To tree-level, these correspond to the following

LSP Interaction Parameters For up quarks in a general (soft) MSSM,

LSP Relic Density Calculation We see that the axial-vector ('spin-dependent') parameters depend on: LSP mass (1) All squark masses and mixing phases to u, d, s (36) Gaugino and higgsino content of the Neutralino (8) tan (1) Total: 46 (real) parameters Why wait for colliders? Can't we do better than this?

LSP Relic Density Bounds One can compute bounds on the density by simply over- or under-estimating the interaction parameters For example, one can use a lower bound on the lightest squark mass and modest bounds for tan to arrive at This has only 6 free, real, bounded parameters and is completely independent of SUSY-breaking

LSP Relic Density Bounds Using the upper bound on ap,n, one arrives at a lower bound on the relic density: Upper bound: work in progress Bound calculated for 6050 randomly generated (physically allowable) MSSMs

Summer Research Advancements My research with Gordon Kane this summer: Developed a general algorithm to compute the mass of an arbitrary WIMP from direct detection data alone Proved the requirement of model input to measure the density (this also applies to indirect detection scenarios mentioned briefly) For the MSSM, Developed a robust method to compute a lower bound on the relic density from limited collider data or current bounds Investigated many ways to explore the MSSM parameter space with dark matter experiments This information can be used to complement and make predictions for the LHC and Tevatron More to come…

Work in Progress Making the mass calculation robust (non-ideal data and handling non-unique solutions) Getting an upper bound on the density from weak model input Observing halo irregularities (lumpiness, streams, triaxial components, &etc) Learning about the MSSM from dark matter direct detection data Comparing ap,n and fp,n should give insight and place bounds on Higgs/squark masses, tan, neutralino content, …?

Summary and Outlook BUT, Dark matter ~ 83% of the matter in the universe We can hope to detect wimps soon if they exist Dozens of experimental groups are competing to be the first to make discovery. (Some already have claims). BUT, Even if wimps are discovered, we cannot address their cosmological relevance until we know their density. Therefore, we must determine the density of any wimps observed before we can begin to understand dark matter.

Acknowledgements Research in collaboration with Gordon Kane Special thanks to Homer Neal, Jean Krisch, & Jeremy Birnholtz Steve Goldfarb University of Michigan Physics Summer REU Program Research supported by

Support Slides Evidence for the energy budget of the universe More direct detection rate analysis Obtaining nucleon interaction parameters from quark interaction parameters An 'Antonio Pich' supersymmetric standard model particle table

The Dark Side of the Universe How do we know what's in the universe? Cosmic microwave background Flatness of the universe Rotation curves of galaxies Big bang nucleosynthesis X-ray spectra from galaxy clusters Weak gravitational lensing Large scale structure formation Type 1a supernovae data …

Direct Detection Rates Signal rate is given by A function of model input nuclear physics depends on wimp mass depends on detector nucleus

LSP Interaction Parameters We scale these quark 'cross sections' to nucleon interaction parameters by

Supersymmetric Standard Model A symmetry between bosons and fermions Based on A. Pich's CERN summer student lectures 2004