Search for Resonant Slepton Production with the DØ-Experiment

Transcription

1 Overview Search for Resonant Slepton Production with the DØ-Experiment Christian Autermann, III. Phys. Inst. A R-parity violating Supersymmetry Resonant Slepton Production and Neutralino Decay Data selection and efficiencies Control plots Preliminary Results Supported by Christian Autermann Bad Honnef, 6.-. September 24

2 DØ Performance Effective Luminosity used for analysis: Ldt = 54± pb -.5 fb - End of 23 shutdown Christian Autermann Bad Honnef, 6.-. September 24 2

3 R-parity Violating Supersymmetry R - parity : W W R/ P = = W 2 MSSM ijk R P + i = ( ) W j R/ P k 3B+ L+ 2S ' λ L L E + λ L Q D + ijk i S is the particle spin, B is the baryon number, L is the lepton number j k '' λ ijk U i D j D k R-parity violating extension of the MSSM i,j,k =,2,3 generation indices Trilepton channel multi lepton final state Chiral superfields: L: lepton doublet superfield E: lepton singlet superfield Q: quark doublet superfield D: down-like quark singlet superfield Resonant production two muon and two jets final state Resonant production at hadronic accelerators λ, λ`, λ``: Yukawa couplings References: H. Dreiner, et.al., Search for R-Parity Violation at Run-II of the Tevatron, hep-ph/ N.Ghodbane, S.Katsanevas, P.Morawitz, E.Perez, SUSYGEN 3, hep-ph/ Christian Autermann Bad Honnef, 6.-. September 24 3

4 Neutralino Production & Decay resonant production decay R-parity violating production and decay Final state: two (isolated) muons two jets Other modes: sneutrino resonance 2 jets, MET & perh. µ Suppressed Modes: (not considered) neutralino pair production and decay over λ`2 t-channel slepton exchange Christian Autermann Bad Honnef, 6.-. September 24 4

5 Run I Exclusion Contour tan A ( β ) µ µ = = = 2. DØ Run I msugra parameters m scalar mass m /2 gauginos mass parameter A trilinear coupling term sign(µ) higgs mass mixing param. tan(β) ratio of the vacuum expect. of the neutral higgs fields m, m /2 and A are defined at the GUT scale Plots for this point, Limits for M~ χ = 75, GeV & M ~ µ = 2, 3 GeV DØ Collaboration, Phys.Rev.Letter 89 (22), hep-ex/53 Christian Autermann Bad Honnef, 6.-. September 24 5

6 Data Sample & Preselection Total delivered L dt = 29pb -, good & reconstructed L dt = 54pb - Data taking period April 22 September 23 Dimuon data sample ~2M events (~4% of all data) Preselection Any Dimuon trigger has fired Veto against cosmic muons (Scintillator timings) 2 muons with pt > 2 GeV, pt > 8 GeV 2 jets with pt > 5 GeV, pt > GeV 2 nd jet pt > 2 GeV OR 2 nd muon pt > 2 GeV central track match & isolation for both muons dimuon angle R µ,µ2 >. to reject QCD events 258 events (27.5 ± 8.[stat] ± 79.6[syst] expected) Christian Autermann Bad Honnef, 6.-. September 24 6

7 Control Plots of the Data Sample () Signal (red) is scaled up by a factor Christian Autermann Bad Honnef, 6.-. September 24 7

8 Control Plots of the Data Sample (2) Signal (red) is scaled up by a factor Christian Autermann Bad Honnef, 6.-. September 24 8

9 Dimuon Trigger Efficiency Weight all MC events according to muon (pt, η, φ), jet, MET to account for dimuon trigger inefficiencies Estimate systematic error by varying the correction factor by ± standard deviation efficiency.8.6 efficiency Z/γ Z/DY * incl. MC 6-3GeV Z/γ * Z/DY incl. MC 6-3GeV nd 2 muon p T [GeV] nd 2 muon η Christian Autermann Bad Honnef, 6.-. September 24 9

10 Isolation Efficiency SRC track cone core i hollow cone Σ E < T E iso i p T ε Data = 8.7% ε MC = 86.9% η φ Christian Autermann Bad Honnef, 6.-. September 24

11 σ = k σ NLO LO Z/γ * Cross Section Cross sections from Pythia are LO. weight Z-MC events with k(m µµ ) to account for higher order corrections k-factor 2.8 Correction Factor K for LO Z/γ Z/DY * x-section NNLO k NLO = + σ α ( 2 M S π 3 2π = k σ NNLO NNLO LO NNLO correction with CTEQ6 is used to weight the Z/γ * µµ ) NLO Λ + MeV NLO Λ = 29 MeV NLO Λ - MeV NNLO CTEQ6 NNLO CTEQ5 References: R. Hamberg et. al.: A COMPLETE CALCULATION OF THE ORDER ALPHA-S**2 CORRECTION TO THE DRELL-YAN K FACTOR., Nucl.Phys.B359:343-45,99 K. Hagiwara et al., Particle Data Group, Phys. Rev. D 66, (22) T. Nunneman, D Note * 3 (Z/γ) [GeV] M µµ Christian Autermann Bad Honnef, 6.-. September 24

12 Systematic Uncertainties cross sect. Uncertainty Trigger Z/γ* cross section Isolation & Tracking Jet energy scale tot. syst. error background +5.3% / 6.9% +3.% / 2.9% +3.6% / 3.6% +3% / 27% tot. syst. error signal 6% 9% 4% 8% 33% Effect on the pre-selection sample Jet Energy Scale uncertainty is the dominating systematic error (Two jets in the final state) 6.5% 3% uncertainty per jet depending on jet p T, η, φ jet p T > 25 GeV jet 2 p T > 5 GeV jet 2 p T > 2 GeV muon 2 p T > 2 GeV Christian Autermann Bad Honnef, 6.-. September 24 2

13 Signal MonteCarlo (SUSYGEN) Invariant mass of 2 jets and the lower energetic muon muon is from ~ χ-decay muon is from ~ µ-decay neither nor Invariant mass of 2 jets and 2 muons mass χ ~ = 2 GeV mass µ ~ = 262 GeV Generated with Susygen and passed through full detector simulation & reconstruction. Christian Autermann Bad Honnef, 6.-. September 24 3

14 Final Selection cut range. p T (µ ) > 2.25 GeV +.88 (M µ ~ - M χ ~ ) p T (µ )+p T (µ 2 ) > 6 GeV p T (jet ) > 25 GeV π < φ (µ,jet i ) < π +.5 < φ (µ 2,jet i ) < GeV (5 GeV+M~ χ /9) < M µµ < 9 GeV+(5 GeV+M χ ~ /9) M χ ~ 4 GeV < M µ2,jet,jet2 < M χ ~ + 2 GeV M µ ~.2 M ~ µ < M µ,µ2,jet,jet2 < M µ ~ +.2 M ~ µ Christian Autermann Bad Honnef, 6.-. September 24 4

15 Signal Efficiencies signal efficiency [%] Constant slepton mass (2, 3 GeV) Signal Efficiency vs. Neutralino mass Efficiency µ =2 GeV µ =3 GeV Constant Signal neutralino Efficiency mass vs. Slepton (75, mass GeV) signal efficiency [%] Efficiency χ =75 GeV χ = GeV Neutralino mass [GeV] Slepton mass [GeV] The neutralino decays only with ~5% BR into two muons and two jets. Christian Autermann Bad Honnef, 6.-. September 24 5

16 Signal Region (m χ ~ =2GeV, m µ ~ =263GeV) Invariant dimuon mass Reconstructed smuon mass (Inv. mass of muon, muon 2, jet & jet 2 ) After all cuts for this msugra point:.±.3±.2 SM evts expected 2 data events found (4.4±.5±.8 signal events) Cut to remove the remaining Z background good agreement between data and standard model background Christian Autermann Bad Honnef, 6.-. September 24 6

17 Cross Section Limits limit / σ [pb] Limit for a fixed neutralino mass = 75GeV and Excluded Run I λ 2 =.7 σ, χ =75 GeV, λ =.7 2 Limit 95%CL, χ =75 GeV limit / σ [pb] Limit for a fixed neutralino mass = GeV and λ 2 =.7 Excluded no Run I limit σ, χ = GeV, λ 2 =.7 Limit 95%CL, χ = GeV Control plots for this point 2 D RunII preliminary 2 D RunII preliminary Slepton mass [GeV] Slepton mass [GeV] Christian Autermann Bad Honnef, 6.-. September 24 7

18 Cross Section Limits limit / σ [pb] 9 8 Limit for a fixed slepton mass = 2GeV and Excluded Run I =.7 λ 2 σ, µ =2 GeV, λ 2 =.7 Limit 95%CL, µ =2 GeV limit / σ [pb] 9 8 Limit for a fixed slepton mass = 3GeV and D RunII preliminary no Run I limit =.7 λ 2 σ, µ =3 GeV, λ 2 =.7 Limit 95%CL, µ =3 GeV D RunII preliminary Neutralino mass [GeV] Neutralino mass [GeV] Christian Autermann Bad Honnef, 6.-. September 24 8

19 Limits on LQD coupling λ 2 λ 2 LQD coupling Limit for a fixed neutralino mass = 75GeV Limit 95%CL, χ =75 GeV D Run I Γ(π e ν)/γ(π µ ν) λ 2 LQD coupling Limit for a fixed neutralino mass = GeV Limit 95%CL, χ= GeV no D Run I limit Γ(π e ν)/γ(π µ ν).2 Excluded.5..5 D RunII preliminary Slepton mass [GeV] Excluded Control plots this point D RunII preliminary Slepton mass [GeV] Theoretical Limit from lepton universality in the pion decay Christian Autermann Bad Honnef, 6.-. September 24 9

20 Limits on LQD coupling λ 2 λ 2.4 Limit for a fixed slepton mass = 2GeV Limit 95%CL, µ =2 GeV λ 2.4 Limit for a fixed slepton mass = 3GeV Limit 95%CL, µ =3 GeV LQD coupling Excluded D Run I Γ(π e ν)/γ(π µ ν) LQD coupling Excluded no D Run I limit Γ(π e ν)/γ(π µ ν) Run I.5.5 D RunII preliminary Neutralino mass [GeV] D RunII preliminary Neutralino mass [GeV] Christian Autermann Bad Honnef, 6.-. September 24 2

21 Conclusions Search for RPV SUSY through the LQD coupling λ 2 in the two muons plus two jets final state Data agrees well with Standard Model expectation Exclusion limits with 95% CL have been presented, improving on Run I results Already.5 fb - data on tape: 3 times more than used for this analyses Presented at ICHEP and DPF Conference Note 4535 with more detailed information is available at Improve analysis by using more luminosity adding the neutralino (missing ET) channel Better signal selection Christian Autermann Bad Honnef, 6.-. September 24 2