Presentation at the LCWS 2005 Meeting

Transcription

1 LCD- Presentation at the 2005 Meeting The Importance of Positron Polarization and the Deleterious Effects of Beam/Bremmstrahlung on the Measurement of Supersymmetric Particle Masses and other Parameters March 2005

2 LCD- THE POSITRON POLARIZATION GROUP CERN-PH-TH/ , DCPT , IPPP G. Moortgat-Pick, et. al.

3 LCD- THE COLORADO GROUP Lisa Boyle, Shenjian Chen, Bradford Dobos, Keith Drake, Chris Geraci, Jack Gill, Jason Gray, Andrew Hahn, Kyle Miller, Martin Nagel, Uriel Nauenberg, Matthew Phillips, Joseph Proulx, Will Ruddick, Jesse Smock, Jinlong Zhang

4 LCD-I ACTIVITIES The Importance of Positron Polarization in Determining SUSY Masses and other Parameters. Simulation of Supersymmetry. New method to overcome the negative effects of beamstrahlung and bremmstrahlung.

5 LCD- Positron Polarization Helps e + Depends on Pol (e + ) Only from LR, RL e + J=1 e - Helicities not coupled Depends on Pol (e - ) e - J=0 Only from LL, RR

6 LCD- electron Left Pol 80% electron Right Pol 80%

7 LCD-ALCPG Electron, Positron Energy Spectrum from e + e - all e e e - Spect.e - 80%R e + Spect. e - Spect.e - 80%R e + Spect. e + 80% L e + 80% R e + 0 pol. e + 0 pol.

8 LCD-ALCPG Muon Energy Spectrum from e + e - μ + μ e - 80% R e + 80% L e 80% L e + 80% R μ R μ L WW Bkg WW Bkg

9 LCD- These selectron, smuon signals with various electron and positron polarization are clear evidence for supersymmetry.!!! These energy distributions can not be produced with Standard Model processes. Need positron polarization to observe dramatic energy distribution shape variations.

10 LCD- Measurement of the sfermion Mixing Angle ( θ ) f Varying the electron and positron polarizations

11 LCD- This is one case where removal of the 2 γ process is crucial The leptons from stau decays are soft.

12 LCD- E cm = 500 GeV σ (e + e t 1 t 1 ) fb M t = 200 GeV 1 (a) 1 (b) cos θ i =0.4 P + 0. P 0. + cos θ i = P P

13 LCD- (a) P = 0.9 (b) L = 500 fb -1 cos θ i A LR P = L=100 fb m t (GeV) P + = o cos θ i

14 LCD- Measuring the sfermion mixing angle The sfermion production goes via γ, Z exchange in the s-channel and the coupling constants depend on the sfermion mixing angle (θ i ). The cross section can be enhanced by varying the positron polarization and the sensitivity on the mixing angle can be determined more readily and measured.

15 LCD- Study of Chargino and Neutralino Production with Positron Polarization.

16 LCD- + - Ε cm = 1 TeV σ ( χ i χ j ) fb SPS1a P e -=-0.9 P e -= + 0.9

17 LCD- Ε cm =1 TeV σ (χ ι χ j )fb SPS1a

18 LCD- σ (χ 1 χ 2 ) X B.R.(χ 2 l R l 1 ) X B.R.( l R l 2 χ 10 ) fb Define T = {P(e )X P( l 2 )}. P( l 1 ) A(T) = σ(τ > 0 ) σ (Τ < 0 ) σ (Τ > 0 ) + σ (Τ < 0 ) A CP = Diff. in Pol. of τ Non-zero A T, A CP CP Violation

19 LCD- Determined the values of σ and A(T) as a function of electron and positron polarization for the following parameters M 0 = 100 GeV tan(β) = 10 M 2 = 400 GeV ϕ(m 1 ) = 0.2π A τ = 250 GeV ϕ(a τ ) = ϕ(μ)= 0 μ = 240 GeV

20 LCD- σ ( χ 10 χ 0 1 l 1 l 2 ) fb A T in % Pe Pe Pe Pe

21 LCD- σ (χ 10 τ 1+ τ ) fb A CP % Pe Pe Pe Pe

22 LCD- σ ( χ 10 τ 1+ τ ) fb A CP % Pe Pe Pe Pe

23 LCD- χ 10 χ 20, χ 20 χ 0 1 l + l χ 30 χ 20, χ 20 χ 0 1 l + l

24 LCD- WORD OF CAUTION All neutralino signals than end in 2 leptons without a mass constraint (like Z 0 ) are overwhelmed by selectron and sneutrino production channels because of t-channels and by 2 γ channels specially if the leptons come from τ decays. Needs careful simulation. Playing with positron polarization should help.

25 LCD- The Effect of Beam-Bremmstrahlung

26 LCD- CM Energy Distribution with Beamstrahlung

27 LCD-ALCPG Simulation of Selectron Production Case Study Consider Case SPS1, M 1/2 = 250 GeV, M 0 = 100 GeV. Mass of e R = GeV, Mass of e L = GeV, Mass of χ 0 1 = Compare Fits with Beam and Bremmstrahlung and without. We use the e + -e - Energy Spectra Substraction Technique to remove Standard Model Background.

28 LCD- Selectron Production e + -e - Energy Spectra

29 LCD- Chi-Square Fits for the SPS1 Snowmass Point M 1/2 = 250 GeV M 0 = 100 GeV tan(β ) fixed at 10

30 LCD- No Bremm Resultant Fits to Energy Edges Bremm

31 LCD- New Method to Determine Masses Compare Energy Spectrum to those Generated with different parameters encompasing the correct one. Do a Chi Square Fit to the Spectra Comparison. Choose the minimum and determine the masses.

32 LCD- M 1/2 = 400, M 0 = 90 expec. value. M 1/2 = 1.5% from 400, M 0 = 90

33 LCD- M 1/2 vs M 0 curves for M sel L values M 1/2 vs M 0 curves for M sel R values Not physical Not physical

34 M 1/2 vs M 0 curves for M (χ 10 ) LCD- No dependence on tan(β ) Not physical

35 LCD-ALCPG Simulation of Selectron, Smuon Production Case Study Consider Case SPS3, M 1/2 = 400 GeV, M 0 = 90 GeV. Mass of e R = GeV, Mass of e L = GeV, Mass of χ 0 1 = GeV. Compare Fits with Beam and Bremmstrahlung and without. For selectrons we use the e + -e - Energy Spectra Substraction Technique to remove Standard Model Background.

36 LCD- Chi Square Fit for the SPS3 Snowmass Point M 1/2 (expec.) = 400 GeV M 1/2 (fit)= GeV M fixed at 90 GeV tan(β ) fixed at 10

37 LCD-ALCPG Muon Energy Spectrum from e + e - μ + μ e - 80% R e + 80% L e 80% L e + 80% R μ R μ L WW Bkg WW Bkg

38 LCD- no brem/beamstrahl brem/beamstrahl

39 LCD_ SPS3 Point; E cm =750 GeV ; M 1/2 =400 GeV, M 0 =90 GeV

40 LCD- Resultant Masses from Fits Input Masses Mass fit E.P. Mas Fit ChiS. μ R μ L

41 LCD- Study of Sneutrino Productione A Very Interesting Case SPS6 Point E cm = 750 GeV M 0 = 150 GeV, M 1/2 = 300 GeV A 0 = 0 GeV, tan(β ) = 10 M ν = GeV; M = χ GeV ν e χ + 1 e ; χ 1+ χ 0 1 W + ; W + hadrons + 1

42 LCD- Energy Spectrum of Hadronic Jets after Hadronic Mass (W) Cut cut from SUSY proc. from WW SM process Sneutrino signal

43 LCD- No Beam/Bremmstrahl Beam/Bremmstrahl SUSY backgnd no beam/bremm Effect of beam/ bremmstrahl

44 LCD- Sneutrino Mass Dependence on Parameters M 0 M 1/2 tan ( β ) A 0

45 LCD- Chargino Mass Dependence on Parameters M 0 M 1/2 A 0 tan (β )

46 LCD- Chi-Square fits to the Electron Energy Distribution

47 LCD- Resultant Masses from Fits Input Mass Before Strahl After Strahl ChiS Fit End Point End Point ν e χ

48 LCD- CONCLUSION The slepton, sneutrino signals are easy to observe and easy to measure with positron polarization if the 2 photon process is tagged with excellent efficiency. The masses depend on all the parameters of the SUGRA model and hence we can determine consistency of M and 0 M with high accuracy (~ 0.2%) and determine 1/2 A 0 and tan (β).

49 LCD- Neutralino Production Study e + e - χ 0 χ 0 χ 0 2 ~ Z Z 0 l + l - one decay χ 0 1 Z 0 q q other decay

50 LCD- Energy Distribution of the Z

51 LCD- Dependence of χ 0 2 Mass on tan(β )

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