KET-BSM meeting Aachen, April 2006

1. How does nature behave at 1TeV ? A search strategy for SUSY et al. Sascha Caron University of Freiburg (Note that this is a short and simple talk) KET-BSM meeting Aachen, April 2006 View from the Schauinsland in Freiburg a couple of weeks ago

2. The situation in 2005 • We still don’t know the origin of EW symmetry breaking • The Higgs boson is not discovered yet • Even with the SM Higgs: • ‘fine tuning’ is required in the model to remain valid to high energies?, • Gravity is not included?, Fermion masses? What is Dark Matter?,… •  typical solutions by increasing the number of • symmetries, dimensions, forces, … Higgs ? Something else? Sascha Caron page 1

3. The situation in 2005 Investigate if EW symmetry breaking is caused by the Higgs. Investigate if there is other physics beyond the Standard Model Part 1 Higgs working groups at ATLAS and CMS Part 2 This approach: Data mining strategies How to find something potentially interesting and previously unexpected in the data? Sascha Caron page 2

4. The situation in 2005 What do we expect to find at the LHC? One physicist's schematic view of particle physics in the 21st century (Courtesy of Hitoshi Murayama) Sascha Caron page 17

5. The situation in 2005 MSSM CMSSM MN2SSM SUSY with extra Dim Or SUSY with extra forces Or …. SUSY VERSIONSOF THE SM NMSSM (an additional Higgs singlet) Choose this point, look at the LHC data, exclude or not! Sascha Caron page 18

6. We found no deviation • We have excluded this point/area which is epsilon of the parameter space We found a deviation Does this mean that the ‘real’ modelis this parameter point?  Is it efficient to work like this?

7. Finding the unexpected – explaining the origin • New Strategy: START FROM THE DATA • Search for deviations in all final states(they are all interesting either as signal or to understand background) • Determine ‘deviation(s)’ or ‘inconsistencies’ (e.g. all muon final • states have problems) • 3) Determine their origin (detector effect, etc.) • Re-determine expectation and • Go to step 1) until publication in refereed journal (btw. it would be nice to speed up steps 1-4) Examples: General Search for new Phenomena at H1 (2004) and D0 Sleuth analysis (2002 but only top final states) Sascha Caron page 19

8. Example: H1 General Search • Event yields for HERA 1 • data • (all channels with SM exp. • > 0.01 event) • Good agreement for • (almost) all channels Channels which have not been syst. studied before Sascha Caron page 19

9. We investigated All Mall and ΣPT distributions We developed a simple algorithm to find and quantify deviations automatically Sascha Caron page 22

10. General Search I spend some time at the New Phenomena web pages at LHC experiments A count of final states planned to be studied leads to 100-500 However consider permutations of j,b,e,µ,τ,v,γ, + consider e.g. charge? Up to 8 particle final states lead to about 40000 Did you have events with 2 photons , a jet and a muon at your LEP exp.? Sascha Caron page 19

11. General Search I spend some time at the New Phenomena web pages at LHC experiments A count of final states planned to be studied leads to 100-500 However consider permutations of j,b,e,µ,τ,v,γ, + consider e.g. charge? Up to 8 particle final states lead to about 40000 Yes I know we do not want to start with 40000 final states at ATLAS  What is the strategy? Sascha Caron page 19

12. Is this possible at LHC? Is this the best strategy for ‘early discovery’? What do we need for this search? What can we learn from theory?

13. Is this possible at LHC ? Yes ! H1 has made the ‘proof of principle’

14. Is this the best strategy for ‘early discovery’? I’m not sure to be honest. We (Freiburg) start from a ‘simpler’ scenario and extend (after we know some of the physics at 1 TeV) Attempt : Start from channels where you expect something new but you don’t know what exactly • pT_miss channels (Dark Matter…?) Idea: less model dependent SUSY searches

15. What do we need for this search? • Theory (with uncertainty) in all channels (Multi purpose event generators) • Uncertainties and fudge factors from data (calibration with candles, use data without pt_miss, use fits to fudge factors, use a global strategy, make ‘fake data’ for each channel, use fast ways to go from 1-4) • Later: A way to learn what we have (LHC olympics, QUAERO, Bard) People interested to join such an effort in Germany

16. Theory and ‘Going the way into the other direction’… An General analysis of LHC data (Yes this is known as the ‘inverse problem’ now, but my transperancy is older)

17. What can we learn from theory? What are ‘model independent’ the best variables to measure (Et, mass, something else?) What do you need to determine nature@1TeV? Is their an interest to work together (background, signal determination)

18. A significant danger is finding correlations and signals that do not really exist. Many examples in particle physics history We are looking for deviations … How surprised should we be to find some? How likely is a 4-5 sigma deviation at LHC even if there is nothing in the data?  Unsolvable problem if you use 2000 PhD students Sascha Caron page 24

19. Quantify the deviations Step 1: Repeat the whole analysis with a pseudo data experiment (dice your own MC data) many times. Step 2: Count how many times you find deviations bigger than in those in your real data. 3% Number of channels 3% of the “Pseudo H1 experiments” have found a bigger deviation 1 10-1 10-2 Probability to find deviation in this channel I know that this is not a new idea, but we do not often use it Sascha Caron page 25

20. What are the numbers for ATLAS?

21. Summary I’ve tried to illustrate some ideas for the ‘searches’ at LHC (ATLAS) and what our group is interested to do