1. Discovery Potential in Jets + MET at 10 TeV ? ATLAS Monojets/Dijets Meeting 20 th May 2008 Claire Gwenlan

2. Introduction 10 TeV run coming soon (2-3 months? 100 pb -1 possible?) Studies at 14 TeV show that some new discoveries could be made very early at the LHC (eg. light SUSY (UED)? Black Holes? TeV- scale resonances?) – so what about at 10 TeV – could we hope to see something? – so what about at 10 TeV – could we hope to see something? 2 “Commissioning to 10 TeV should be fast, no quench being anticipated, giving us confidence that the experiments will be recording data at record high energies by the summer. In 1989, it was only a matter of weeks before LEP produced its first profound result – a measurement of the number of light neutrino families. In this respect at least, history will not be repeating itself. The LHC is a discovery machine, and the discoveries it is chasing will require a little more patience.” Robert Aymar, on the 10TeV run As a case study, I have used a search for SUSY in the dijets+MET channel (based on CSC note work)

3. Currently no MC… BUT can re-weight existing 14TeV samples hadronic cross section given by: hadronic cross section given by: For a particular kinematic configuration with s, t, u, should just need to change the probability that incoming partons *had* that configuration i.e. just a PDF re-weight PDFs  from 14TeV  10TeV proton PDFs Plot from James Stirling: DIS08 ^ ^ ^ ^ ^ ^ x i : x of parton i at 14TeV; x i ’: x of parton i at 10TeV Re-weight MC to 10 TeV using: 3 hard subprocess cross section

4. Check of Reweight Method Good agreement between reweighted and 10 TeV samples (bkgs also checked) EG: sample of SUSY signal (SU3) events generated in ATLFAST p T Jet,1,2 >150,100 GeV M eff = p T Jet,1 + p T Jet,2 + MET Effective Mass example weights (all < 1) 4 PDF weight

5. SUSY search in 2  Jet + MET final state analysis strategy based on SUSY CSC5 – full details found in note) analysis strategy based on SUSY CSC5 – full details found in note) Cut No. 2-Jet+MET Analysis Cuts 0 J70_XE70 trigger 1 p T Jet,1 > 150 GeV 2 p T Jet,2 > 100 GeV 3 MET > max(100,0.3*M eff ) 4 |phi(Jet1,2)-phi(MET)| > 0.2 5 no isolated lepton Case Study: 2  Jets + MET “Generic search for R-parity conserving SUSY in inclusive 2-Jet + MET+0- lepton channel” Effective Mass: M eff = ∑ p T Jet,i + MET [sum runs over two highest-p T jets] 5

6. Integrated L = 100 pb -1 BEFORE reweighting  6 Case Study: 2  Jet + MET Results: SU3 signal vs. SM bkg

7. Integrated L = 100 pb -1 BEFORE reweighting  AFTER reweighting  14 TeV  10 TeV:  SU3 signal reduced by ~ 2.9  SM bkg reduced by ~ 2.3 7 Case Study: 2  Jet + MET Results: SU3 signal vs. SM bkg

8. Integrated L = 100 pb -1 Comparison of some other SUSY benchmark points (SUX) all are mSUGRA, but cover quite a wide range of phenomenologies all are mSUGRA, but cover quite a wide range of phenomenologiesSU1 coannihilation region SU2 focus point region SU3 bulk region SU4 low mass point SU6 funnel region SU8.1 coannihilation region Results: other mSUGRA points 8 Case Study: 2  Jet + MET

9. numbers are maximum significances (taken above some M eff threshold) (don’t take too much notice of the actual values – it’s just to get a rough feeling) Statistical Significance (S/√B) 14 TeV 10 TeV SU12312 SU2 < 1 SU33922 SU410667 SU6168 SU82412 Some Example Numbers 100 pb -1 9 Discovery Significance (Z n ) * 14 TeV 10 TeV SU19.15.9 SU2<1<1 SU311.28.3 SU412.512.5 SU67.54.8 SU89.76.2 * Z n is a measure of the significance (as used in CSC5) which tries to take into account systematic uncertainties on the bkg measurements. The numbers in the table above are calculated assuming 50% uncertainty on QCD and 20% on all other bkgs – these are not necessarily the “right” numbers – dedicated bkg studies needed for those!

10. Summary Is there potential for discovery with small amounts of 10 TeV data?  YES – there does seem to be potential! A 5x increase in centre-of-mass energy compared to previous experiments is still a lot !!! – this case study has focussed on SUSY discovery in Jets+MET– and this may not need much data (i.e. it doesn’t take much to give large S/  B values for the models considered here!) BUT that data still needs to be understood BUT that data still needs to be understood This was really just a quick look for fun – to see if anything is even potentially feasible! It looks like it could be, but the limiting factor for Jets+MET searches will of course be how well we can determine and understand the bkgs with the small amount of data we expect 10

11. BackUps

12. 12 Method: other example checks  a few other example checks (currently low statistics, except for J8MET)  good agreement CSCID: 008270 CSCID: 008190 CSCID: 005985 CSCID: 008094

13. mSUGRA Points m0m1/2A0 tan  Region SU170350010 > 0 Coannihilation SU23550300010 Focus point SU3100300-3006 > 0 Bulk SU4200160-40010 Low mass SU6320375050 > 0 Funnel SU8.1210360040 Coannihilation More details on the mSUGRA points considered 13

14. MC Bkg Samples Sample CSC ID  (pb) N T1005200450 600 K TTbar005204383 100 K J4MET008090916.4070K J5MET008091655.85K J6MET00809267.4235K J7MET0080935.34K J8MET008094 2.21x10 -2 4K WW00598524.550K WZ0059862.150K ZZ0059877.850K Zee00819446.25K Zmumu0081959.605K Ztautau0081914.505K Znunu00819041.3335K Wenu00827049.0550K Wmunu00827128.6450K Wtaunu00827255.9150K 14