1 / 21

SUSY Discovery at 10TeV?

SUSY Discovery at 10TeV?. SUSY working group meeting 21 st May 2008 Claire Gwenlan, UCL. Introduction. 10 TeV run coming soon (2-3 months? 100 pb -1 possible?) Studies show that, if SUSY is relatively light, it could be discovered very early at the LHC (based on 14 TeV Monte Carlo).

kasen
Download Presentation

SUSY Discovery at 10TeV?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SUSY Discovery at 10TeV? SUSY working group meeting 21st May 2008 Claire Gwenlan, UCL

  2. Introduction • 10 TeV run coming soon (2-3 months? 100 pb-1 possible?) • Studies show that, if SUSY is relatively light, it could be discovered very early at the LHC (based on 14 TeV Monte Carlo) EG: 0-lepton + 2-Jet + MET inclusive SUSY search (CSC5)  so what about at 10 TeV – could we hope to see something? 2

  3. PDFs  from 14TeV  10TeV • Currently no MC… BUT can re-weight existing 14 TeV samples • 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 proton PDFs hard subprocess cross section Plot from James Stirling: DIS08 ^ ^ ^ Re-weight MC to 10 TeV using: xi : x of parton i at 14TeV; x i’: x of parton i at 10TeV 3

  4. Check of Method EG: sample of SU3 SUSY events generated in ATLFAST • Good agreement between re-weighted and 10 TeV samples (bkgs also checked) PDF weights Effective Mass pTJet,1,2 >150,100 GeV example weights (all < 1) Meff = pTJet,1 + pTJet,2 + MET [GeV] • Good agreement between re-weighted and 10 TeV samples (bkgs also checked) • method rather general  can re-weight to any CM energy < 14 TeV 4

  5. Check of Method EG: sample of SU3 SUSY events generated in ATLFAST • Good agreement between re-weighted and 10 TeV samples (bkgs also checked) PDF weights Effective Mass pTJet,1,2 >150,100 GeV example weights (all < 1) Meff = pTJet,1 + pTJet,2 + MET [GeV] • Good agreement between re-weighted and 10 TeV samples (bkgs also checked) • method rather general  can re-weight to any CM energy < 14 TeV 5

  6. SUSY analysis • EG: CSC5-style, inclusive 2- and 3-Jet analyses (full details in note) • results shown in main part of talk are for the 2-Jet case (3-Jet results in backups) “Generic search for R-parity conserving SUSY in the inclusive 2-Jet + MET+0-lepton channel” no optimisation of cuts for 10 TeV – i.e. just a simple repeat of CSC5 analysis Effective Mass: Meff = ∑ pTJet,i + MET [sum runs over two highest-pT jets] 6

  7. Results: SU3 vs. SM bkg EG: CSC5 2Jet + MET + 0lepton SUSY analysis: • Integrated L = 100 pb-1 • BEFORE reweighting  NOTE: all MC predictions shown at LO (i.e. no k-factors applied) 7

  8. Results: SU3 vs. SM bkg EG: CSC5 2Jet + MET + 0lepton SUSY analysis: • 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 - QCD reduced by ~ 2.4 - tt reduced by ~ 2.6 - W/Z reduced by ~ 2 - diboson reduced by ~ 1.9 NOTE: all MC predictions shown at LO (i.e. no k-factors applied) 8

  9. Results: other mSUGRA points EG: CSC5 2Jet + MET + 0lepton SUSY analysis: • Integrated L = 100 pb-1 • Comparison of some other SUSY benchmark points (SUX) • all are mSUGRA, but cover quite a wide range of phenomenologies 9

  10. Statistical Significances 100 pb-1 • Numbers are maximum significances (taken above some Meff threshold) 10

  11. Discovery Significances 100 pb-1 • Numbers are maximum significances (taken above some Meff threshold) (don’t take too much notice of the actual values – it’s just to get a (very) rough feeling) * Zn is a measure of the significance (as used in CSC5) which tries to take into account systematic uncertainties on the bkg measurements. Numbers in the table are calculated assuming 50% uncertainty on QCD and 20% on all other bkgs – these are not the “right” numbers – dedicated bkg studies needed for those! 11

  12. Summary • Is there potential for discovery with small amounts of 10 TeV data?  YES – there does at least seem to be potential! • A 5x increase in centre-of-mass energy compared to previous experiments is still a lot !!! – and the discovery of light SUSY may not need much data (it doesn’t take much to give large S/B values for the models considered here) • 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 will of course be how well we can determine and understand the backgrounds with the small amount of data we expect. • Bonus Extra – method could be useful to allow studies to proceed before 10 TeV MC available? Or as an alternative for samples that will not be re-generated? 12

  13. BackUps

  14. Results: other mSUGRA points EG: CSC5 3Jet + MET + 0lepton SUSY analysis: • Integrated L = 100 pb-1 14

  15. mSUGRA Points • More details on the mSUGRA points considered 15

  16. MC Bkg Samples 16

  17. Method: Some Bkg Checks • some other example checks  all show good agreement (within statistical limitations) CSCID: 008094 CSCID: 005985 CSCID: 008190 CSCID: 008270

  18. Some Bkg Weight Examples Weights for all processed events i.e. no cuts imposed T1 Wenu J8MET Zee WW SU3 Znunu J5MET SU4

  19. Sensitivity to choice of Q2 Re-weighting technique not very sensitive to choice of factorisation scale Meff = pTJet,1 + pTJet,2 + MET [GeV] s, t, u are the usual Mandelstam variables

  20. EG. Re-weighting to Other s Values 5 TeV 7 TeV Meff = pTJet,1 + pTJet,2 + MET [GeV] • Should be able to re-weight to any CM energy < 14 TeV • but *not* to higher beam energies, since some regions of phase space accessible at higher s, will not be populated in the 14 TeV Monte Carlo

  21. “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 21

More Related