Probing 23% of the Universe at the Large Hadron Collider

1. Probing 23% of the Universe at the Large Hadron Collider Alfredo Gurrola R. Arnowitt •B. Dutta • T. Kamon • A. Krislock • D. Toback Texas APS Oct. 19, 2007

2. Outline • Dark Matter (DM), Supersymmetry (SUSY), and mSUGRA • Basics of the mSUGRA model • A methodology for measuring SUSY masses at the LHC • Measuring the Dark Matter Relic Density using 2 observables • Relax the assumptions of universal couplings • A methodoloy for measuring the SUSY masses and Dark Matter Relic Density in a less model independent environment • Testing Gaugino Universality

3. Dark Matter and Supersymmetry Standard Model (SM) does NOT provide a solution, but Supersymmetry (SUSY) extensions of SM naturally provide a weakly interacting massive particle that is stable: Lightest SUSY Particle (LSP) Co-Annihilation mechanism in the early universe is required to produce the cosmologically observed Dark Matter abundance (relic density) Cosmological observations indicate that a large fraction of the universe is Cold Dark Matter We choose to work with a theoretically and experimentally well motivated model : Minimal Supergravity (mSUGRA) A mass difference of ~ 5 -15 GeV is required! Measurement of DM would be a “direct” detection of CDM!! Can we measure DM at the LHC?

4. mSUGRA (Minimal Supergravity) Determines the particle masses at the electroweak scale by solving the Renormalization Group Equations Small effect on the phenomenology for tanb>15 At the Grand Unified Scale: 4 parameters + 1 sign m1/2 Common gaugino mass at MG m0 Common scalar mass at MG A0 Trilinear couping at MG tanb<Hu>/<Hd> at the electroweak scale sign(m) Sign of Higgs mixing parameter (W(2) = m HuHd)

5. Dark Matter Signature at LHC 2. Interested in events with or pairs 3. & Branching Ratios are ~ 97% 1. , Production is dominant SUSY process at LHC ( )

6. Event Selection a. b. c. d. • In order to target events with , we require ≥ 2 hadronic t’s • Require large Missing Transverse Energy to target events with • High PT jets are required to target events with squarks/gluinos [1] References • hep-ph/0603128, Phys. Lett. B639 (2006) 46. R. Arnowitt et al • hep-ph/0608193 R. Arnowitt et al

7. Observables Sort τ’s by ET (ET1 > ET2 > …) & use OS-LS method to extract t pairs from the decays on a statistical basis Number of OS-LS counts also decreases with smaller DM

8. Observables In general, Mtt will depend on . Nos-ls will depend on . Affects the production cross-section Affects the t acceptance 2 Masses —› 2 Observables

9. Dark Matter Relic Density We have 2 observables defined as functions of 2 masses For our reference point: Invert the equations to determine the masses as functions of the observables Determine mSUGRA parameters Determine Dark Matter Relic Density

10. Dark Matter Relic Density SUSY Mass Hierarchy Non-Universal SUGRA DM ~ 5 – 15 GeV What if Nature has chosen a Non-Universal world? • The previous methods depend on Gaugino Unification • Those methods can’t be used in • a Non-Universal SUGRA model • without using other observables!

11. More Observables Slope of PT distribution contains ΔM Information. hep-ph/0603128 Slope of the soft t PT distribution has a DM dependence What is the dependence on the other SUSY masses?

12. More Observables p p We can combine the t’s to the jet from the squark decay to provide another mass peak Peak depends on the squark mass! What is the dependence on the other SUSY masses?

13. Dark Matter Relic Density We have 4 observables defined as functions of 4 masses For our reference point: Invert the equations to determine the masses as functions of the observables Determine Dark Matter Relic Density