Probing the Connection Between Supersymmetry and Dark Matter Bhaskar Dutta Texas A&M University Physics Colloquium, OSU, March 30, 2006 March 30, 2006 Probing the Connection Between SUSY and Dark Matter 1
Faculty Members and Research Areas EXPERIMENT [Collider Physics - CDF, CMS, International Linear Collider] T. Kamon, P. McIntyre, A. Safonov, D. Toback [Neutrino Physics - MINOS, NOνA] R. Webb [Dark Matter - ZEPLIN] J. White THEORY [Phenomenology] R. Allen, R. Arnowitt, R. Bryan, B. Dutta, D. Nanopoulos [String Theory] K. Becker, M. Becker, D. Nanopoulos, C. Pope, E. Sezgin March 30, 2006 Probing the Connection Between SUSY and Dark Matter 2
THINKING ABOUT THE UNIVERSE Early Universe Cosmological Connection? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 3
Part 1: Theory Recent works on Collider Physics and Dark Matter Physics. Introduction to Standard Model (SM) Reasons for going beyond the SM Supersymmetric (SUSY) SM and SUGRA Model Existing experimental constraints Prospects of discovering SUSY at the Large Hadron Collider (LHC) and a future Linear Collider (LC) Conclusion March 30, 2006 Probing the Connection Between SUSY and Dark Matter 4
Standard Model (SM) Glashow 62, Weinberg 67, Salam 68 Underlying theory: a gauge theory (e.g., QED) Quantum Mechanics + Special Relativity 6 quarks, 6 leptons and gauge particles Unexpected results: a) Too heavy top quark b) Non-zero mass ν Otherwise, very successful March 30, 2006 Probing the Connection Between SUSY and Dark Matter 5
Too Heavy Top QUARK MASSES M top = 178 10 9 ev M up ~ 5 10 6 ev h Yet to be discovered March 30, 2006 Probing the Connection Between SUSY and Dark Matter 6
Non-Zero Neutrino Mass NEUTRINO MASSES M ν < 1eV Neutrino masses are non zero! The SM can not accommodate nonzero neutrino mass!!! See recent results from SuperKamiokande, SNO, KamLAND, K2K, MACRO. For future results, see MINOS, MiniBoone, T2K, March 30, 2006 Probing the Connection Between SUSY and Dark Matter 7
Very Successful at E~100 GeV Predictions were tested in various experiments: 1973 1983 1995 Remarkable accuracy: M M B.S. Neutral current @ CERN SPS (400 GeV p) M.S. W/Z discovery _ @ CERN SppS (540 GeV pp ) Ph.D. Top discovery @ Fermilab Tevatron (1.8 TeV pp ) exp Z theory Z = = 91.1876 ± 91.1874 ± 0.0021 0.0021 Explains most of the data! GeV GeV What happens at higher energy? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 8
Structural Defect in the SM Problem in Higgs Sector The Higgs mass becomes too large at scale of a few TeV (1000 x M proton ). There should be some new theory at this energy scale and this theory would keep the Higgs mass under control. The contribution to the Higgs mass Boson loop Fermion loop 2 λ B Λ 2 λ F Λ 2 Λ = Scale of new physics Solution: Supersymmetric SM March 30, 2006 Probing the Connection Between SUSY and Dark Matter 9
Supersymmetrized SM The fundamental law(s) of nature is hypothesized to be symmetric between bosons and fermions. Fermion (S = ½ ) Boson (S = 0 or 1) Have they been observed? Not yet. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 10
Looking into Higher Energy e.g., QCD 2 12π α s ( Q ) = 2 2 (11 n 2 n ) log( Q / Λ ) color flavor Running Coupling n f = 6 (quark flavors); n c = 3 (colors) The Nobel Prize in Physics 2004 α s Q (GeV) March 30, 2006 Probing the Connection Between SUSY and Dark Matter 11
3 Couplings at Higher Energy (Strength of Force) 1 1/α i (E) 1/α 1 1/α 2 1/α 3 log 10 (Energy) SM Three gauge couplings do do not not meet at at a single point. We need a theory which goes to to a higher scale. The SM works very well at ~100 GeV. The SM works very well at ~100 GeV. Grand Unified Theory with Supersymmetry March 30, 2006 Probing the Connection Between SUSY and Dark Matter 12
1/α 1 Sign of SUSY Unification SU(3) x SU(2) x U(1) α 3 α 2 α 1 G α GUT 1/α 1 SM SM + SUSY 1/α i (E) 1/α 2 1/α 3 1/α 2 1/α 3 1/α GUT log 10 (Energy) log 10 (Energy) M SUSY ~ 500-3000 GeV/c 2 and two (and only two) Higgs doublets M SUSY ~ 500-3000 GeV/c 2 and two (and only two) Higgs doublets What else? : ingredient for superstring theory March 30, 2006 Probing the Connection Between SUSY and Dark Matter 13
E Road Map to Unified Theory String Theory SUSY GUT x March 30, 2006 Probing the Connection Between SUSY and Dark Matter 14
Minimal Supergravity (msugra) SUSY model with two Higgs fields (H u and H d ) in the framework of unification: 1) All SUSY masses are unified at the grand unified scale. m m 1/2 0 for gaugino for squarks masses and sleptons 2) Two more parameters: tanβ A 0 March 30, 2006 Probing the Connection Between SUSY and Dark Matter 15
Power of tanβ I always want you to be slimmer than your cousin SELECTRON. τ ~ tanβ e ~ This tanβ also controls the SUSY masses, especially, the 3 rd generation SUSY particles, ~ such as. t, b ~ and τ ~ March 30, 2006 Probing the Connection Between SUSY and Dark Matter 16
Feynman Diagrams for SUSY Decays SUSY partner of W boson: chargino SUSY partner of τ lepton: stau SUSY partner of Z boson: neutralino Lightest neutralinos are always in the final state! This neutralino is the dark matter candidate!! What do we gain if the theory is supersymmetric? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 17
Elegant Solution??? Many new particles (100 GeV a few TeV) and many new parameters. Whatever happened to elegant solutions? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 18
Part 2: Experimental Data Recent works on Collider Physics and Dark Matter Physics. Introduction to Standard Model (SM) Reasons for going beyond the SM Supersymmetric (SUSY) SM and SUGRA Model Existing experimental constraints Prospects of discovering SUSY at the Large Hadron Collider (LHC) and a future Linear Collider (LC) Conclusion March 30, 2006 Probing the Connection Between SUSY and Dark Matter 19
Cosmic Connection Astrophysics CDM = Neutralino ( ) SUSY χ ~ 1 0 CDM = The matter which is present without any electromagnetic interaction. To explain the amount of the CDM, there must be another SUSY particle whose mass must be closer to the neutralino. (see the next slide.) Is it possible to observe these features in other experiments (e.g., Dark matter detection, Collider experiments)? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 20
Existing Bounds from Experiments March 30, 2006 Probing the Connection Between SUSY and Dark Matter 21
Existing Bounds from Experiments March 30, 2006 Probing the Connection Between SUSY and Dark Matter 22
Existing Bounds from Experiments msugra naturally provides a lighter stau. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 23
Cosmologically Allowed Region Mass of Squarks and Sleptons Excluded Higgs Mass (M h ) Branching Ratio b sγ Magnetic Moment of Muon Mass of Gauginos CDM allowed region March 30, 2006 Probing the Connection Between SUSY and Dark Matter 24
Small and Large tanβ R. Arnowitt, B. Dutta, T. Kamon, M. Tanaka, Phys. Lett. B538, 121 (2002) R. Arnowitt, B. Dutta, B. Hu, hep-ph/0310103 (talk at BEYOND '03) Mass of Squarks and Sleptons Mass of Gauginos What are the signals from the narrow co-annihilation corridor? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 25
Part 3: Prospects Recent works on Collider Physics and Dark Matter Physics. Introduction to Standard Model (SM) Reasons for going beyond the SM Supersymmetric (SUSY) SM and SUGRA Model Existing experimental constraints Prospects of discovering SUSY at the Large Hadron Collider (LHC) and a future Linear Collider (LC) Conclusion March 30, 2006 Probing the Connection Between SUSY and Dark Matter 26
Colliders and Cosmology Small M ~ 0 1 τ χ 1 τ ~ M M ~ τ M ~ 0 = 5 ~ 15 1 χ 1 GeV We probe this narrow mass difference directly to establish the cosmological connection. What are the signals at colliders? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 27
How to Discover? Quarks. Neutrons. Mesons. All those particles You can t see. That s what drove me to drink. But now I can see them! A little bit more scientific way? 1) Tevatron (2 TeV pp ) 2) LHC (14 TeV pp) 3) ILC (500 or 800 GeV e + e ) March 30, 2006 Probing the Connection Between SUSY and Dark Matter 28
Collider 101 March 30, 2006 Probing the Connection Between SUSY and Dark Matter 29
E TEV LHC ILC LHC ILC Tevatron HERA LEP2 Precision March 30, 2006 Probing the Connection Between SUSY and Dark Matter 30
E TEV LHC ILC LHC ILC Tevatron HERA LEP2 Precision March 30, 2006 Probing the Connection Between SUSY and Dark Matter 31
E TEV LHC ILC LHC ILC Tevatron HERA LEP2 SHE IS SUPERSYMMETRIC! Precision March 30, 2006 Probing the Connection Between SUSY and Dark Matter 32
Collider Experiments Questions: a) What are the signals from the narrow coannihilation corridor? ~ ± 0 1 τ ± χ 1 τ ~ M M ~ τ M ~ 0 = 5 ~ 15 1 GeV b) What is the accuracy of the measurement on M χ 1 Collider Experiments Tevatron (2 TeV pp ) LHC (14 TeV pp ) LC (500 or 800 GeV e + e ) Let s me summarize prospects at each collider. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 33
Tevatron s = 1.96 TeV Proton (p) _ Antiproton (p) CDF DØ March 30, 2006 Probing the Connection Between SUSY and Dark Matter 34
Signature at the Tevatron The reach of the direct search at the Tevatron is not high enough. V. Krutelyov, R. Arnowitt, B. Dutta, T. Kamon, P. McIntyre, Y. Santoso, Phys. Lett. B505, 161 (2001) We device to look into something different R. Arnowitt, B.Dutta, T. Kamon, M. Tanaka, Phys. Lett. B538, 121 (2002) V. Krutelyov, Ph.D. thesis (Texas A&M), December 2005 March 30, 2006 Probing the Connection Between SUSY and Dark Matter 35
Rare Decay B s µ + µ B 9 SM = 3. 4 10 6 B SUSY (tanβ ) Within the SM, we will not see any events even with 100 x 10 12 collisions. In the SUSY models (large tanβ), the decay can be enhanced by up to 1,000. The B s µ + µ event would look like this. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 36
Example Analysis: CDF Powerful Likelihood method to reduce BG events with LH > 0.99 N BG = 1.27± 0.37 N obs = 1 780 pb 1 ~ 40 x 10 12 collisions ±60 MeV/c 2 (2.5σ) See CDF and D0 Collaborations, hep-ex/0508058 (2005) March 30, 2006 Probing the Connection Between SUSY and Dark Matter 37
Results and Prospects CDF/DØ analyses are evolving and improving with more data. DØ Limit 2.3x10 7 (expected at 1000 pb 1 ) ~100 x 10 12 collisions March 30, 2006 Probing the Connection Between SUSY and Dark Matter 38 x? Tevatron Limit 1.5x10 7 CDF : 364 pb 1 DØ : 300 pb 1 Preliminary CDF Limit 1x10 7 CDF : 780 pb 1 Tevatron Limit 2x10 8? CDF : 2000 pb 1 DØ : 2000 pb 1
B (B s µµ µµ) ) and Cosmological Connection TeV LHC/ILC Cosmology M~ g Can we see the SUSY co-annihilation signals at LHC and ILC? ~ 1400 GeV/c2 Competitive to the LHC March 30, 2006 Probing the Connection Between SUSY and Dark Matter 39
Large Hadron Collider (LHC) C.M. Energy = 14 TeV New Energy Frontier 2 large detectors: ATLAS and CMS Performance: Bound to find or exclude Higgs Discover or almost exclude SUSY March 30, 2006 Probing the Connection Between SUSY and Dark Matter 40
SUSY Signature and BGs at the LHC Squark-Gluino Production Key decay: ~ 0 + χ τ ~ + + τ τ + τ ~ 0 2 1 χ 1 Signal: >2τ (one high and one low energy) + jets (q s, g s) + missing energy ( ~ 0 χ ) 1 tt Backgrounds: SM ( ) and other SUSY processes R. Arnowitt, B. Dutta, T. Kamon, N. Kelov, D. Toback, hep-ph/0603128, submitted to PLB R. Arnowitt, A. Aurisano, B. Dutta, T. Kamon, N. Kelov, D. Toback, P. Wagner, in preparation March 30, 2006 Probing the Connection Between SUSY and Dark Matter 41
The event might look like this CDF highest H T Event E T1 = 172 GeV E T2 = 153 GeV E T4 = 65 GeV + >2 x / E T = 223 GeV E T3 = 80 GeV H T = E T1 + E T2 + E T3 = 404 GeV τ March 30, 2006 Probing the Connection Between SUSY and Dark Matter 42
E miss T + 2j + 2τ2 Analysis Summary of Analysis [1] Select a generic sample of 2 jets and 2 taus with E T vis > 20 GeV for each of top and SUSY ( M = 10.6 GeV, M gluino = 830 GeV) events and compare various kinematic distributions. [2] Optimized cuts (see the next page) are: E T jet1 > 100 GeV E T jet2 > 100 GeV E T miss > 180 GeV E T jet1 + E T jet2 + E T miss > 600 GeV [3] Select SUSY events with at least 2 taus with p T vis > 40, 20, 20, 20 GeV and ε τ = 50%, fake = 1%. OS and LS histograms are filled with M 12 only for 2-τ event, M 12, M 13, M 23 for 3-τ event, M 12, M 13, M 14, M 23, M 24, M 34 for 4-τ event M = 10.6 GeV 10 fb 1 LS OS OS LS [4] Fill di-tau mass histograms for OS and LS events separately. [5] Subtract LS from OS. See the figure. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 43
SUSY vs Top The top quark production will be a serious background source for the SUSY searches. SUSY Top We can reduce the SM backgrounds by the appropriate choice of cuts. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 44
Anatomy of Di-tau Mass Distribution M peak = = 47.1 GeV M max = 78.7 GeV 10 fb 1 OS LS OS LS How to Establish the Discovery [1] N OS LS : Number of OS LS pairs 5σ significance where Significance = N OS LS / N OS+LS Required luminosity (how many pp collisions are required) ~ 0 + 0 2 τ ~ + + τ 1 τ + τ χ 1 χ ~ M M ~ τ M ~ 0 = 10. 6 1 χ 1 GeV [2] M peak and M max : Clear peak and end point in di-tau mass distribution for OS LS pairs Are they consistent with the decay kinematics? Since M peak is related to M, the accuracy of M peak determines the accuracy of M. δm peak = r.m.s / N OS LS March 30, 2006 Probing the Connection Between SUSY and Dark Matter 45
Discovery Luminosity 10-20 fb 1 We assume δm/m gluino = ±5%, since the peak position changes as the M gluino changes. A small M can be detected in first few years of LHC. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 46
Accuracy in M M peak 10 fb 1 OS LS OS LS We extract M from M peak. We assume δm/m gluino = ±5%, since the peak position changes as the M gluino changes. M = 10 ± 1. 2 + 1. 4 1. 2 GeV March 30, 2006 Probing the Connection Between SUSY and Dark Matter 47
LHC Summary and Future Plan ATLAS and CMS experiments should be able to observe the SUSY signals in the coannihilation region if they identify hadronically decaying tau leptons with p T (visible) > 20 GeV How do we know the stau-neutralino co-annihilation is responsible for the relic density? There are three regions allowed cosmologically. They are: (i) bulk, (ii) annihilation funnel, (iii) focus points regions. We have to develop experimental techniques to detect the SUSY signals (if exists) from three region. Can we study them at the LHC? Future Projects March 30, 2006 Probing the Connection Between SUSY and Dark Matter 48
International Linear Collider (ILC) March 30, 2006 Probing the Connection Between SUSY and Dark Matter 49
SUSY Signature and BGs at ILC Stau-pair production M ~ χ M ~ τ M 0 = 5 ~ 15 1 1 GeV Final State: + τ τ ~ ~ 0 0 χ 1 χ 1 E(τ) is small because M is small. E(τ) is small because M is small. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 50
M(j 1,j 2,E miss ) 2 o Mask 2 o Mask Experimental Data (500 fb 1 ) m 0 = 210 ( M = 9.53 GeV) Small χ 2 value suggests the data sample likely contains m 0 = 210 SUSY events. δσ/σ ~ 4% (same for 1 o mask) V. Khotilovich, R. Arnowitt, B.Dutta, T. Kamon, Phys. Lett. B618, 182 (2005) March 30, 2006 Probing the Connection Between SUSY and Dark Matter 51
Prospects at ILC March 30, 2006 Probing the Connection Between SUSY and Dark Matter 52
ILC Summary and Future Plan Only ~ χ ~ 10 χ 20 and ~ τ ~ 1 τ 1 production are kinematically allowed at 500- GeV LC in cosmologically allowed msugra parameter space (large tanβ). LCD with 1 o active mask is important to detect forward electron/ positron to suppress γγ events, especially for the small M cases. RH polarization is crucial to reduce the SM (ννττ) events and to study the ~ τ ~ 1 τ 1 production. In this channel, we have the maximum reach for m 1/2 in the allowed region. M(j 1,j 2,E miss ) is proposed to measure the difference between ~ χ 0 1 and ~ τ 1 masses. NEXT: Is 1 o active mask good enough at 800-GeV ILC? March 30, 2006 Probing the Connection Between SUSY and Dark Matter 53
Part 4: Conclusion Recent works on Collider Physics and Dark Matter Physics. Introduction to Standard Model (SM) Reasons for going beyond the SM Supersymmetric (SUSY) SM and SUGRA Model Existing experimental constraints Prospects of discovering SUSY at the Large Hadron Collider (LHC) and a future Linear Collider (LC) Conclusion March 30, 2006 Probing the Connection Between SUSY and Dark Matter 54
Conclusion SUSY cures the problems of the SM, and fulfills the dream of Grand Unification and explains the dark matter (DM) content. The minimal supergravity (msugra) model, based on the unification framework, is already constrained by many experiments. The DM content of the universe requires some specific features of the msugra parameter space e.g. coannihilation. The signal in the coannihilation region at the colliders will confirm the model. The LHC will be able to probe this signal and measure the masses. An ILC will improve the accuracy and will help to make many new measurements of SUSY models. March 30, 2006 Probing the Connection Between SUSY and Dark Matter 55