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Measuring Mass Difference at LHC using soft τ P T Slope

Measuring Mass Difference at LHC using soft τ P T Slope. Alfredo Gurrola in collaboration with Richard Arnowitt, Bhaskar Dutta, Teruki Kamon, David Toback, Abram Krislock, Nikolay Kolev (Regina, Canada). Outline. SUSY Signature at the LHC

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Measuring Mass Difference at LHC using soft τ P T Slope

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  1. Measuring Mass Difference at LHC using soft τ PT Slope Alfredo Gurrola in collaboration with Richard Arnowitt, Bhaskar Dutta, Teruki Kamon, David Toback, Abram Krislock, Nikolay Kolev (Regina, Canada) Measuring Mass Difference using soft τ PT Slope

  2. Outline • SUSY Signature at the LHC • Analysis Methods in 2t & 3t Papers • Gaugino Universality • Measuring DM in a Non-Universal SUGRA model • Simultaneous measurement of model parameters to test Universality Measuring Mass Difference using soft τ PT Slope

  3. Hard t p p p p Soft t Soft t Hard t Hard t SUSY at LHC 1. , Production is dominant SUSY process at LHC ( ) 2. Interested in events with or pairs 3. & Branching Ratios are ~ 97% 4. In Coannihilation Region of SUSY Parameter Space: GeV Soft t Measuring Mass Difference using soft τ PT Slope

  4. Looking Back at 2t & 3t Papers 1. Use Hadronically Decaying t’s 2. Sort τ’s by ET (ET1 > ET2 > …) & use OS-LS method to extract t pairs from the decays on a statistical basis 3. Use Counting Method (NOS-LS) & Ditau Invariant Mass (Mtt) to measure mass difference 4. 5. hep-ph/0603128 hep-ph/0608193 Measuring Mass Difference using soft τ PT Slope

  5. Non-Universal SUGRA SUSY Mass Hierarchy • Methods used in 2t & 3t papers depend on Gaugino Unification • Those methods can’t be used in • a Non-Universal SUGRA model • without using another observable! • How can we measure DM? Non-Universal SUGRA DM ~ 5 – 15 GeV Measuring Mass Difference using soft τ PT Slope

  6. PT STUDY Slope of PT distribution contains ΔM Information. hep-ph/0603128 Slope of the soft t PT distribution has a DM dependence Measuring Mass Difference using soft τ PT Slope

  7. Extracting t Pairs from Decays EVENTS WITH CORRECT FINAL STATE (2t OR 3t + ...) - 2t + 2j + ETmiss APPLY CUTS TO REDUCE SM BACKGROUND (W+jets, …) ETmiss > 180 GeV, ETj1 > 100 GeV, ETj2 > 100 GeV, ETmiss + ETj1 + ETj2 > 600 GeV ORDER TAUS BY PT & APPLY CUTS ON TAUS: WE EXPECT A SOFT t AND A HARD t PTall > 20 GeV, PTt1 > 40 GeV LOOK AT t PAIRS AND CATEGORIZE THEM AS OPPOSITE SIGN (OS) OR LIKE SIGN (LS) OS: FILLLOW OSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH OSPT HISTOGRAM WITH PT OF HARDER t LS: FILLLOW LSPT HISTOGRAM WITH PT OF SOFTER t FILLHIGH LSPT HISTOGRAM WITH PT OF HARDER t LOW OS-LS LOW OS LOW LS HIGH OS HIGH LS HIGH OS-LS Measuring Mass Difference using soft τ PT Slope

  8. PT STUDY • ISAJET 7.64 to simulate our model of SUSY production • TAUOLA to re-decay the t’s • Run generated particles through detector simulator, PGS4 (author: John Conway) using CMS parameter file • Used reconstructed jets • Used generator level t’s after being re-decayed by TAUOLA • - “visible” values of momentum and energy were used • Separate Monte Carlo routine in ROOT to simulate the effects of t identification efficiency and jet to t fake rate Measuring Mass Difference using soft τ PT Slope

  9. ETmiss + 2j + 2t Analysis: PTsoft [1] ETmiss , at least 2 jets, at least 2 t’s with PTvis > 20, 40 GeV [2] et = 50% , fake rate 1% [3] Cuts: ETjet1 > 100 GeV, ETjet2 > 100 GeV, ETmiss > 180 GeV ETjet1 + ETjet2 + ETmiss > 600 GeV OS OS-LS LS Measuring Mass Difference using soft τ PT Slope

  10. PT STUDY Can we still see the dependence of the PT slope on DM using OS-LS Method? Measuring Mass Difference using soft τ PT Slope

  11. What is the dependence of PT slope on mass & mass? PT Slope is insensitive to mass & mass!! PT STUDY: ETmiss + 2j + 2t • Luminosity = 40 fb-1 What is the dependence on DM? Measuring Mass Difference using soft τ PT Slope

  12. PT STUDY: ETmiss + 2j + 2t Measuring DM from the PT Slope • Luminosity = 40 fb-1 Measuring Mass Difference using soft τ PT Slope

  13. PT STUDY: ETmiss + 2j + 2t • How accurately can DM be measured for our reference point? • Considering only the statistical uncertainty: We can measure DM to ~ 6% accuracy at 40 fb-1 & ~ 12% accuracy at 10 fb-1 for mass of 831 GeV. Measuring Mass Difference using soft τ PT Slope

  14. Simultaneous Measurement of Model Parameters • Can parameterize the our observables as functions of DM, , & • NOS-LS , to first order, does not depend on mass. A large increase or decrease in mass is needed to obtain a point that lies outside the error bars • Cross-Section is dominated by the gluino mass Measuring Mass Difference using soft τ PT Slope

  15. Simultaneous Measurement of Model Parameters Measuring Mass Difference using soft τ PT Slope

  16. Testing Gaugino Unification CONTOURS OF CONSTANT VALUES ( L = 40 fb-1 ) • Intersection of the central contours • provides the measurement of DM, • , & • Auxilary lines determine the 1s • region • 1st order test on Universality Measuring Mass Difference using soft τ PT Slope

  17. SUMMARY • Soft t PT distribution is sensitive to DM • PT slope is independent of gluino mass and neutralino mass • DM can measured to ~ 12% accuracy at 10 fb-1 for our reference point • Methods used in 2t and 3t papers can’t be used in a Non-Universal SUGRA model • We can combine counting method, ditau invariant mass measurement and PT slope to test the idea of gaugino unification to first order Measuring Mass Difference using soft τ PT Slope

  18. PT STUDY PROBLEM: OS-LS method does NOT give the “true” slope Measuring Mass Difference using soft τ PT Slope

  19. PT STUDY – Method I • How accurately can we measure DM with this method? • Assuming the theoretical dependence (‘True’ Fit) of DM on Slope: Slope does NOT change with ~ 10% change in gluino mass, but the uncertainty changes due to change in NOS-LS We can measure DM to ~ 8-9% accuracy at 40 fb-1 for mass of 831 GeV. Measuring Mass Difference using soft τ PT Slope

  20. PT STUDY What causes this difference? • BACKGROUND: SM, SUSY, soft t’sfrom the • t’s from the is the dominant background! How can the slope be corrected? Measuring Mass Difference using soft τ PT Slope

  21. Correcting the Slope: Method I • Defining the measured PT slope by and the theoretical (“true” identification) PT slope by , the mean statistical uncertainty on the slope is with the mean statistical uncertainty of . The shift S due to background effects is given by the mean difference of the theoretical slope and the measured slope: The root-mean-square uncertainty is With these definitions, the CORRECTED measured Slope is Measuring Mass Difference using soft τ PT Slope

  22. Correcting the Slope: Method I A plot of the distribution of the shift S between theoretical and measured values. The shift S is fairly close to being constant. A summary of the calculated uncertainties and shift in GeV. Measuring Mass Difference using soft τ PT Slope

  23. Correcting the Slope: Method II • Soft t’s from is the dominant background • By increasing the second t PT cut, this source of background can be reduced • Other Background (SM & other SUSY Background) is reduced Measuring Mass Difference using soft τ PT Slope

  24. Correcting the Slope: Method II Measuring Mass Difference using soft τ PT Slope

  25. Optimizing t PT Cut Optimized Cut would be ~ 70 – 80 GeV for DM = 10.6 GeV Measuring Mass Difference using soft τ PT Slope

  26. Measuring Mass Difference using soft τ PT Slope

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