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Particle Physics and Cosmology in the Co-Annihilation Region

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1 Particle Physics and Cosmology in the Co-Annihilation Region
R. Arnowitt, A. Aurisano, B. Dutta, Gurrola, T. Kamon, A. Krislock, N. Kolev*, P. Simeon, D. Toback & P. Wagner Department of Physics, Texas A&M University *Department of Physics, Regina University PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

2 Introduction What problems are we trying to solve? Dark Matter
Hierarchy problem in the Standard Model Other Particle Physics problems… Is there a single solution to both of these problems? Minimal solution? Particle Physics solution to this problem? PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

3 The Players and their Roles
Cosmologists/ Astronomers Particle Theorists Particle Experimentalists PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

4 The Players and Their Roles
Experimentalists at FNAL/LHC do direct searches for SUSY particles Astronomy and Cosmology tell us about Dark Matter Particle Physics Theory Predicts Supersymmetry Dark Matter Candidate Convert the masses into SUSY model parameters and Wh2 Do we live in a world with Universal Couplings? Learn more about the universe with two separate measurements of Wh2 Discover SUSY and measure the masses of the superparticles PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

5 Outline of the Talk Supersymmetry and the Co-annihilation region
The important experimental constraints A Smoking Gun: Small DM = Mstau-MLSP Identifying events at the LHC Discovery and Experimental Observables Measurements of Particle masses: DM, MGluino & Mc2 Supersymmetry parameters: M0 and M1/2 Cosmological implications: WLSPh2 Conclusions PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

6 Structure of the Analysis
Use the current constraints/understanding to motivate the co-annihilation region of Supersymmetry in mSUGRA Assume this is a correct description of nature and see how well we could measure things at LHC Convert these results into useful numbers for both particle physics and cosmology PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

7 Hypothetical Timeline
Pre-2005: Strong constraints on Dark Matter density, the Standard Model and Supersymmetry 2005: Phenomenologists use these results to constrain a SUSY model  Tell the experimentalists at LHC where to look : Establish that we live in a Supersymmetric world at the LHC 2011: Precision measurements of the particle masses and SUSY parameters  compare Dark Matter relic density predictions to those from WMAP PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

8 SUSY, mSUGRA and Cosmology
Many models of Supersymmetry provide a Cold Dark Matter candidate Work in an Minimal Supergravity (mSUGRA) framework Build models from MGut to Electroweak scale Models consistent with all known experiments Universal Couplings Straight-forward predictions More on this later PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

9 mSUGRA in 1 Slide Translation for Experimentalists and Cosmologists:
PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

10 Example Translation PPC 2007 5/17/2007
Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

11 Experimental Constraints
Particle Physicists: Non-observation of the Higgs and the Gauginos and their mass limits Measurement of branching ratio of the b-quarksg Astronomers and Cosmologists: WMAP measurement of the Relic Density PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

12 Particle Physics Constrained Region
Higgs Mass (Mh) Branching Ratio b  sg Excluded Mass of Squarks and Sleptons Neutralino LSP Magnetic Moment of Muon If confirmed… Neutralino LSP Mass of Gauginos PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

13 “Vanilla” mSUGRA and Cosmology
mSUGRA parameters uniquely determine the LSP mass Interaction Cross Sections Sparticle abundances in the early universe Relic Density today Use WMAP Relic Density measurements to further constrain SUSY parameter space Typically the following annihilation diagrams are important… PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

14 Problem Most of mSUGRA space predicts too much Dark Matter today
Need another mechanism to reduce the predicted LSP relic density to be consistent with the amount of Dark Matter observed by WMAP PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

15 Co-Annihilation? If there is a second SUSY particle with small mass (similar to that of the LSP) it can have a large abundance in the early universe The presence of large amounts of this second particle would allow large amounts of the LSP to annihilate away and reduce the relic density observed today Co-annihilation effect (Griest, Seckel:92) Common in many models PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

16 Particle Physics and Cosmology in the Co-annihilation Region
PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

17 Add Dark Matter Constraints
Higgs Mass (Mh) Branching Ratio b  sg Excluded Mass of Squarks and Sleptons Magnetic Moment of Muon If confirmed… Neutralino LSP WMAP Favored region Mass of Gauginos PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

18 Aside on our Assumptions…
The WMAP constraints limits the parameter space to 3 regions that should all be studied: The stau-neutralino co-annihilation region Neutralino having large Higgsino component (focus point) Annihilation through heavy Higgs (funnel region) A small bulk region for large values of m1/2 If (g-2)m holds, mostly only this region is left Concentrate on this region for the rest of this talk… PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

19 What if the Co-Annihilation Region is realized in Nature?
Can such a small mass difference be measured at the LHC? The observation of such a striking small DM would be a smoking gun!  Strong indication that the neutralino is the Dark Matter If we can observe such a signal, can we make important measurements? PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

20 Outline Supersymmetry and the Co-annihilation region
The important experimental constraints A Smoking Gun: Small DM = Mstau-MLSP Identifying events at the LHC Discovery and Experimental Observables Measurements of Particle masses: DM, MGluino & Mc2 Supersymmetry parameters: M0 and M1/2 Cosmological implications: WLSPh2 Conclusions PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

21 Structure of the Analysis
Use the current constraints/understanding to motivate the co-annihilation region of Supersymmetry in mSUGRA Assume this is a correct description of nature and see how well we could measure things at LHC Convert these results into useful numbers both particle physics and cosmology PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

22 A Smoking Gun at the LHC? High Energy Proton-Proton collisions produce lots of Squarks and Gluinos which eventually decay Identify a special decay chain that can reveal DM information high energy t low energy t PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

23 SUSY Signature at the LHC
low energy high energy t+t-’s+Jet(s)+Met Trigger on the jets and missing ET PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

24 Not just any t will do! Our t’s are special!
c2 decays produce a pair of opposite sign t’s Many SM and SUSY backgrounds, jets faking t’s will have equal number like-sign as opposite sign Each c2 produces one high energy t and one low energy t The invariant mass of the t-pair reflects the mass of the SUSY particles and their mass differences PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

25 Require a third t from one of the other gauginos (common)  3t+Jet+Met
The dominant background is typically ttbar, so we require an extra object and large kinematics to reject it Require a third t from one of the other gauginos (common)  3t+Jet+Met Require a second large jet from the other squark/gluino and large HT  2t+2Jets+Met More details in R. Arnowitt et al. Phys.Lett.B639:46,2006 and Phys. Lett.B649:72, 2007 PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

26 Some Technical Details
PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

27 Look at the PT distribution of our softest t
Slope of PT distribution contains ΔM Information Low energy t’s are an enormous challenge for the detectors Also, get more events for large DM Slope of PT distribution is largely unaffected by Gluino Mass PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

28 More Observables… Look at the mass of the t+t- in the events
Can use the same sample to subtract off the non-c2 backgrounds  Clean peak! Larger DM: More events Larger mass peak Clean peak Even for low DM PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

29 Depends on the number of observable events and the sparticle masses
Discovery Luminosity Depends on the number of observable events and the sparticle masses Above ~5 GeV get more events as more events pass kinematic cuts Fewer events as the production Cross Section drops PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

30 Discovery Luminosity 10-20 fb-1 Variation in gluino mass +5% -5% A small DM can be detected in first few years of LHC ~100 Events PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

31 Outline Supersymmetry and the Co-annihilation region
The important experimental constraints A Smoking Gun: Small DM = Mstau-MLSP Identifying events at the LHC Discovery and Experimental Observables Measurements of Particle masses: DM, MGluino & Mc2 Supersymmetry parameters: M0 and M1/2 Cosmological implications: WLSPh2 Conclusions PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

32 What are we trying to measure?
Measure these! Check these! PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

33 Measuring the SUSY Masses
For our sample of events we can make three measurements Number of events Slope of the PT distribution of the softest t The peak of the Mtt distribution Since we are using 3 variables, we can measure three things Since A, tanb and sign(m) don’t change the phenomenology much (for large tanb) we choose to use our three variables to determine DM, Mgluino and the c2 Mass Model parameters Universality Test PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

34 Measure DM and the Gluino Mass
The slope of the PT distribution of the t’s only depends on the DM The event rate depends on both the Gluino mass and DM Can make a simultaneous measurement An important measurement without Universality assumptions! Results for ~300 events (10 fb-1 depending on the Analysis) PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

35 Add in the Peak of Mtt As the neutralino masses rise the Mtt peak rises PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

36 Are we in a Universality World?
} ~15 GeV or ~3% PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

37 What if we Assume the Universality Relations?
Results for ~300 events (10 fb-1 depending on the Analysis) } ~15 GeV or ~2% } ~0.5 GeV or ~5% PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

38 } Outline Supersymmetry and the Co-annihilation region
The important experimental constraints A Smoking Gun: Small DM = Mstau-MLSP Identifying events at the LHC Discovery and Experimental Observables Measurements of Particle masses: DM, MGluino & Mc2 Supersymmetry parameters: M0 and M1/2 Cosmological implications: WLSPh2 Conclusions } PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

39 Infer m0 and m1/2 |~5 GeV or s~2%| |~10 GeV |
Use DM and Mgluino to measure m0 and m1/2 Assume Universality |~10 GeV | or s~3% M1/2 (GeV) |~5 GeV or s~2%| M0 (GeV) PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

40 Cosmology Measurements
PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

41 Conclusions If the co-annihilation region is realized in nature it provides a natural Smoking Gun The LHC should be able to uncover the striking small-DM signature with ~10 fb-1 of data in multi-t final states and make high quality measurements with the first few years of running The future is bright for Particle Physics and Cosmology as these precision measurements should allow us to measure the DM without Universality assumptions and make comparisons to the precision WMAP data with only minor assumptions PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

42 Backup Slides PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

43 Some caveats PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

44 Aside… We note that while the analysis here was done with mSUGRA, a similar analysis is possible for any SUGRA models (most of which possess a co-annihilation region) provided the production of neutralinos is not suppressed PPC 2007 5/17/2007 Particle Physics and Cosmology in the Co-annihilation Region Dave Toback et. al., Texas A&M University

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