1. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Prague LCD Presentation Status of SPS1 Analysis at Colorado Uriel Nauenberg for the Colorado Group November 15, 2002

2. NLC – The Next Linear Collider Project Colorado Univ. - Boulder ZEUTHEN LCD PRESENTATION Supersymmetric Particles and the Need for Tagging in the Very Forward Direction Uriel Nauenberg for the Colorado Group November 13, 2002

3. NLC – The Next Linear Collider Project Colorado Univ. - Boulder The Colorado Group Toshinori Abe, James Barron, Samantha Carpenter, Shenjian Chen, Eric Jurgenson, Luke Hamilton, Anthony Johnson, Liron Kopinsky, Uriel Nauenberg, Joseph Proulx, William Ruddick, David Staszak, Chris Veeneman

4. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Colorado SUSY Simulations At Snowmass 2001 the International Collaboration generated 9 simulation points; 6 SUGRA model points with high tan (  ), 2 GMSB points and 1 AMSB to determine how well they can be determined. The tan (  ) = 10 is particularly difficult because it generates a large number of  s in the final state. This leads to a large number of low momentum tracks which get overrun by the large 2 photon process.

5. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Colorado SUSY Simulations This discussion presents the analysis of the first point. We discuss the selectron, sneutrino, neutralinos, and smuon studies status.

6. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Introduction This discussion presents how the SUSYsignals are observed above the background and the observed mass resolution after the background is removed. The background considered is the full complement of SUSY background, the Standard Model WW background and 2 photon background where the two fast electrons have an angle < 20 mrads. We have not included the background from Beamstrahlung  collisions producing the appropriate final state particles.

7. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SUGRA Model Parameters We studied the SUGRA case with the SPS1 parameters given below. The parameters were agreed to by the International Collaboration. M = 100 GeV M = 250 GeV A = -100 tan(  ) = 10  = 352.39 The main characteristic of this point is due to the large value of tan (  ) which leads to final states with  ’s and hence low energy tracks. 0 1/2

8. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SUSY Masses SPS Masses           ISAJET Baer Paige Protopopescu Tata

9. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SUSY Cross Sections SPS1 Cross Sections (fb) ISAJET Baer Paige Protopopescu Tata   

10. NLC – The Next Linear Collider Project Colorado Univ. - Boulder The New Result Selectron Mass Measurement e e, e e, e e, e e New Method X 10 Resolution Improvement e R,L ~  e ± +  ~ 1 0 RRLLRLLR ~~ ~ ~ ~~~~ + -_ + _ + _ + _ e    L      1 e

11. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Background The distribution in the next slide fairly much describes what we observe if we are looking at the final states that contain single leptons, like in the search for selectrons, sneutrinos, smuons, etc. The large low momentum distribution is due to the large cross section for the 2 photon process e + e  e + e +  +  e + e + lepton pair where the 2 e’s are very forward and the lepton pairs are present in the detector. + -

12. NLC – The Next Linear Collider Project Colorado Univ. - Boulder INITIAL VIEW All dimuons Except e e    Ecm = 750 GeV Pt(  from  )<14 GeV Lum = 50 fb 11

13. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Background issues The simulation of the background in the previous slide does not include the 2nd order processes shown in the next slide. Hence it is possible that the background in the energy region above 20 GeV might be larger. This needs to be corrected.

14. NLC – The Next Linear Collider Project Colorado Univ. - Boulder BACKGROUND SIMULATION

15. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Spectrum Positron Energy Spectrum 80% L Pol80% R Pol L L + R R + L R + L R + SUSY bkg      

16. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Spectrum Positron Energy Spectrum SUSY + W W +    e e +   (e e ) * * + - 80% L 80% R + -

17. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Spectrum Electron Energy Spectrum L L +R R +L R +L R + SUSY bkg       80% L Pol 80% R Pol

18. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Spectrum Electron Energy Spectrum SUSY + W W +    e e +  (e e ) * * + - 80% L 80% R + -

19. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Pt of Background    e e * * + - Pt of the e e Vector Sum + -

20. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Pt of the Background       e e * * + - + - - Pt of the e e Vector Sum + -

21. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Pt of the Selectron Signal PtPt Pt of the e e Vector Sum + -

22. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron The mass of the SUSY particles depend on observing the minimum and maximum energy of the final state particle. The case discussed now is the selectron and neutralino. See one of our last slides showing the equations. In the distributions before this the edges are obscured by SUSY background channels. We use the large differences in the Pt distributions of some of the large background to remove it. In the next slide where we take differences we get the correct edges because what background remains cancels out.

23. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Nevertheless the low energy edge of the distribution gets degraded by the Pt cut. Thye main background that remains is the WW  e e   which is mostly removed by demanding that neither electron be more that 200 GeV, The remaining background is cancelled by taking the difference since the electron and positron energy spectrum of WW decays is the same.

24. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Energy Spectrum No Bremms Bremms Energy Spectrum (e - e )(R-L)  

25. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SELECTRON MASSES RESULTS Name Input Mass Measured Mass GeV Lum = 500 fb R  L  1 0  e 143.00 No Brem 141.57  0.80 Brem 146.3  0.8 e 202.12 No Brem 201.51  0.80 Brem 208.6  0.8  96.05 No Brem 95.4  4.0 Brem 99.9  3.9

26. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Higher Neutralinos e e    ;    Z ; Z  l l   23   0 0 3 0  2,1 0    Lum = 2000 fb 11 No Strahlung With Strahlung

27. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SUSY Particle Masses e + e   +  ;    + Z ;    + Z 34 0 0 + _   31 32 L = 1500 fb

28. NLC – The Next Linear Collider Project Colorado Univ. - Boulder L=5000 fb More on Neutralinos  34  

29. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Discussion on Neutralinos We still need to separate the   and   signals Not clear that it can be done. 233 34   

30. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Electron Sneutrinos e + e  + + - ee     + 87.9% e  1 0 ~ e   + e 8.8% e  1 +  -

31. NLC – The Next Linear Collider Project Colorado Univ. - Boulder SUSY Cross Sections SPS1 Cross Sections (fb) ISAJET Baer Paige Protopopescu Tata 

32. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Electron Sneutrinos Search Procedure for Electron Sneutrinos Plot energy distribution of e when we have only an e and   Selectron and Smuon background removed Except for Left Selectrons, Smuons that Decay into a Neutrino and Chargino and Chargino decays into Staus or Taus. Only      and e e  W W remain **   Use  energy spectrum to remove e background

33. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Electron Sneutrinos e energy spectrum for e +  events  No Brem Brem 80% Left Pol., Lum - 500 fb 11

34. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Electron Sneutrinos  Energy Spectrum This spectrum comes from  decays and represents the electron background from this source.

35. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Pt of e +  From Sneutrinos From    e  * *

36. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Selectron Sneutrinos Electron Sneutrinos Energy Spectrum of e’s from e  events After  Spectrum Subtraction P=80  L

37. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Sneutrino Mass Results E lowhigh No Brem Brem 4.11 .04 21.10 .09 GeV 4.22 .08 20.40 .12 GeV Masses (GeV) M M   1   Input No Brem Brem 186.00 176.38 184.7  0.7 175.1 188.4  0.7 178.9

38. NLC – The Next Linear Collider Project Colorado Univ. - Boulder With     e Lum = 500 inv fb * * Total Electron Spectrum Total Muon Spectrum

39. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Sneutrinos e /e - SM  Energy Spectrum Pt (e+  ) > 4 GeV; E (e or  ) < 50 GeV + - P=80  L

40. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Sneutrinos e /e -- (SM+SUSY)  Energy Spectrum + - Pt (e +  ) > 4 GeV ; E (e or  ) < 50 GeV P=80  L

41. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Sneutrinos Pt (e +  ) > 4 GeV; E (e or  ) < 50 GeV e /e - (SM + SUSY)  Energy Spectrum + - P = 80% R

42. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Sneutrinos Sneutrino production can occur via a t-channel. Hence it is sensitive to the longitudinal polarization of the electron. The previous two slides show how the signal disappears when you have a right handed electron polarization because the coupling becomes very small in this case.

43. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Smuons Backgrounds W W Decays into       * * e e    or     e e     e e    +   + - L L R R     Signal   

44. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Smuon Backgrounds Muon Energy versus Angle

45. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Smuon Background WW Background Reduction Remove events with energy of either muon  200 GeV Remove events with muons in the energy vs  band   Background Rough cut at present

46. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Smuons  Energy Spectrum Pol=80%R, Lum=500 fb -1  L  Pure Smuons Smuons+WW+Cuts

47. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Smuons  Energy Spectrum Pol=80%L, Lum=500 fb

48. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Beam Energy Resolution A  B + C M = E { E (min) E (max) } Acm c c 1/2 ————————— {E (min) + E (max)} c c M = M { 1 – 2[E (min) + E (max)]} cc ————————— E cm B A 1/2  (M)  0.35  (E ) cm

49. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Conclusions The large number of low energy events is due to the 2 photon background. This can be removed by having a detector in the very forward region that detects all tracks with angles > 20 mrad to the beam direction. Then requiring that the Pt of the tracks in the detector add to > 10 GeV removes this background. In the case of the e  final state the 2 s from the  decay makes this limit more diffuse. Restricting to lower than 20 mrad is useful to reduce this background. This should be an R&D effort.

50. NLC – The Next Linear Collider Project Colorado Univ. - Boulder Conclusions SUSY masses can be measure to a fraction of 1 GeV in a few cases and to about 1 GeV in the others. The tracker should measure momenta to about 1 GeV or better. This leads to similar errors in the mass due to an uncertainty of 0.5% in the center of energy.

51. NLC – The Next Linear Collider Project Colorado Univ. - Boulder More Conclusions The selectron masses can be measured as long as the right and left selectron masses are different. The electron sneutrino mass can measured but the 2 photon into  s background affects the accuracy of the measurement. The right smuon mass can be measured but the left smuon is obscured by the WW   background.

52. NLC – The Next Linear Collider Project Colorado Univ. - Boulder More Conclusions The neutralinos signals are seen but there are overlapping channels. We are investigating how to separate them. We are investigating how to use the full energy spectrum to determine the masses. Looks like it will work. Very useful for decays which are not 2 body where the energy spectrum edges are not well defined.

53. NLC – The Next Linear Collider Project Colorado Univ. - Boulder

54. NLC – The Next Linear Collider Project Colorado Univ. - Boulder