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Search for TeV-scale bosons in the +- decay channel in CMS

Search for TeV-scale bosons in the +- decay channel in CMS. I. Golutvin, P. Moissenz, V. Palichik, M. Savina, and S. Shmatov Joint Institute for Nuclear Research, Dubna. Motivation Extensions of the Standard Model and Beyond the SM Extended Gauge Models (Z  )

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Search for TeV-scale bosons in the +- decay channel in CMS

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  1. Search for TeV-scale bosons in the +- decay channel in CMS I. Golutvin, P. Moissenz, V. Palichik, M. Savina, and S. Shmatov Joint Institute for Nuclear Research, Dubna • Motivation • Extensions of the Standard Model and Beyond the SM • Extended Gauge Models (Z) • RS1-scenario (KK-graviton resonance) • Cross-sections and expected rates • Background (DY) • Forward-backward asymmetry • Angular distributions • Conclusions

  2. General Motivations • the current measurements (D0, CDF) of the Drell-Yan cross- section at high dilepton invariant mass (up to 0.6 TeV) are in good agreement with the Standard Model predictions (NLO) • study of high mass dileptons at LHC allows one to test the SM at a new energy scale (Drell-Yan production up to 1  4 TeV invariant mass region) • dilepton continuum is very sensitive to any modifications of SM Lagrangian induced by new physics beyond the SM • Extended gauge models (Sequential Standard Model, Left-Right Model, E6-, S0(10)- based models) • new gauge bosons, W and Z • horizontal bosons, R • new Higgs bosons, H++, H-- • Large extra dimension scenarios (ADD, RS, NLED’s) • Compositeness models I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  3. Motivations for dimuon study • many models beyond the SM predicted new heavy (m ~ a few TeV) boson states • Extended gauge models (Z, spin1-state, from SSM, LRM, E6) C.-E. Wulz, CMS-NOTE 1993/107 • Large extra dimension scenarios, Randall-Sundrum RS1 (GKK-graviton, spin-2 state) P.Traczyk and G.Wrochna, CMS-NOTE 2002/003, M.-C.Lemaire and J.-P.Pansart, CMS-NOTE 2002/020 • di-muon channel is a clear and simple signature of resonances • concentrate within certain mass interval • good isolation • both muons come from the same vertex • good effective mass and angular resolution for high-pT muons • low background I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  4. Simulation Tools Signal (Z´) and background (DY) simulation Pythia 6.217, qqbar  Z´ (no jet veto, other production mechanisms qg  qZ´ will be added in the future), CTEQ5L, K(Z´)= 1, KDY = 1.38 Initial- and final-state radiation are switched on SSM: Br(+-) = 0.032 LRM:assume the same couplings for both left- and right-handed sectors: gL / gR= 1 (value as in the SM)  Br(+-) = 0.023 -, -, and -models:couplings from J.Rosner, Phys. Rev. D35, 2244 (1987) GKK simulation Pythia 6.217, qqbar  GKK, gg GKK, qqbar  gGKK, qg  qGKK, gg  gGKK Detector Response and Reconstruction Fast non-GEANT simulation: CMSJET 4.7 (detector response are taken into account by smearing of energy/momentum according to some resolution) I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  5. Background SM Background • main SM background comes from DY process with large invariant dilepton (+-) masses • an irreducible SM background goes down rapidly when M+- grows • at present, no exact NLO and NNLO matrix elements have been used, we have used K = 1.38 (from Tevatron data) for M > 1 TeV •  (M+- > 1 TeV) = 9.07 fb (Pythia 6.217) • Di-bosons: ZZ, WW, ZW (is not taken into account) •  (M+- > 1 TeV) = 0.4 fb, less then 4.5 % of Drell-Yan, K=1.4-1.9 • ttbar-quark (is not taken into account) •  (M+- > 1 TeV) = 0.3 fb, ~ 3 % of Drell-Yan, K=1.6 I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  6. Z-bosons

  7. no detector response DY + Z ,/M ~ 3 % d/dM, fb/40 GeV Drell-Yan M, GeV Expected Z+-Rate we assume no exotic fermions (nG=0) for SSM, -, -, -models (Br = 0.032) number of extra fermion generations is nG=3 (right-handed fermions) for LRM (Br = 0.023) Pythia6.217 + CMSJET 4.7  no kinematics cuts I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  8. Discovery Limit for Z Nmin = max (5NB, 10) NB is the number of Drell-Yan background inside 3rec mass window after cuts Pythia 6.217 + CMSJET 4.7 Generated ||  2.4, pT  20 GeV d/dM, fb/GeV Response M, GeV Background, DY The search reach for CMS (in TeV) I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  9. Z Forward-Backward Asymmetry qqbar  Z +- F(y) is number of  with cos(*) > 0, B(y) is number of  with cos(*) < 0, * is the angle in the di-muon C.M. (Z rest frame) between the - and one (fixed) of the proton beams, y is Z rapidity P. Langacker, R.W. Robinett, J.L.Rosner, PR, D30, 1470 Z rapidity MZ’ = 2.0 TeV 100 fb-1 Z rapidity Z rapidity rapidity-dependence of forward-backward asymmetry in Z+- decays for various models has a very distinctive behaviour Z rapidity I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  10. GKK-resonance

  11. q q l- GKK /Z0 + q q l+ l- l- g GKK l+ l+ + g q g q GKK GKK g GKK GKK g q g g g q g g GKK graviton production (RS1) • virtual production • the SM exchange by  or Z boson interferes with the exchange by graviton (qq  GKK  +-) ~ 3 % of total graviton cross-section • there is also gluon-gluon initiated graviton exchange process which has no the SM analogue (gg  GKK  +-) ~ 10 – 11 % • real graviton production, i.e. graviton emission (qq  gGKK , qg  qGKK, gg  gGKK with +- + jet in the final state) ~ 7 % ~ 70 % I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  12. Expected GKK+-Rates 5 diagrams were computed (virtual and real graviton production) Br (GKK +-) = 0.0205 GKK +- rates were computed for the different coupling constants c = k/MPl = 0.01, 0.02, 0.05, 0.07, 0.1 k is the AdS5 curvature 100 fb-1 tot  Br  Lint 0.1 0.07 0.05 0.02 K=1 0.01 Mass, TeV I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  13. Discovery Limit for GKK The search reach for CMS (in TeV) CMS is able to test RS1 scenario up to 1.95 TeV and 3.74 TeV mass limit for c = 0.01 and c = 0.1, respectively, even at 10 fb-1 I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  14. GKK Events Z m = 1.5 TeV 6000 events cos* Angular Distributions * is the angle of ’s in the Z (GKK) rest frame Theoretical expectations: ||  2.4, pT  20 GeV,  3rec qq  Z  (K=1), 100 fb-1 qq, gg  GKK   (K=1, c=0.1), 10 fb-1 I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  15. Conclusions • CMS detector performance allows to perform precise measurements of di-muon pairs up to invariant masses of about 4 TeV or even higher • study of a Drell-Yan muon pair production enables to check-up the SM within this mass region • Any deviations from SM predictions (excess or deficit) • will indicate the new phenomena beyond SM • extra gauge boson Z can be observed in the dimuon channel with S/B  5 for masses up to 2.5  3.0 for 10 fb-1 TeV 3.5  4.1 TeV for 100 fb-1 integrated luminosity • on the assumption c=0.01 gKK can be observed in the dimuon channel with S/B  5 for masses up to 1.9 for 10 fb-1 and 2.6 TeV for 100 fb-1 • forward-backward asymmetry of muons (from Z) can be used for more detailed study of the Z origin model • spin-2 states (graviton) can be distinguished from spin-1 states (Z) by analyzing angular distribution of muons I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  16. Supplement

  17. Z-bosons

  18. Mass, GeV Number of muon pairs at 100 fb-1 Z’SSM Z’LR Z’ Z’ Z’ 500 5.9105 4.2105 5.3105 1.88105 1000 4104 3.1104 3.6104 1.26104 1200 1.8104 1.4104 1.6104 5700 1500 6800 4970 6000 2100 2000 1730 1200 1522 535 2500 670 360 470 166 3000 190 124 170 60 4000 30 20 26 9 5000 8 4 5 Expected Z+-Rate we assume no exotic fermions (nG=0) for SSM, -, -, -models (Br = 0.032) number of extra fermion generations is nG=3 (right-handed fermions) for LRM (Br = 0.023) no kinematics cuts I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  19. Signal/Background Events for Z Pythia 6.217 + CMSJET 4.7, ||  2.4, pT  20 GeV Generated d/dM, fb/GeV d/dM, fb/GeV M, GeV M, GeV Response Background, DY I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  20. Z Forward-Backward Asymmetry pp  Z +- F(y) is number of  with cos(*) > 0, B(y) is number of  with cos(*) < 0, * is the angle in the di-muon C.M. (Z rest frame) between the - and one (fixed) of the proton beams, y is Z rapidity P. Langacker, R.W. Robinett, J.L.Rosner, PR, D30, 1470 Z rapidity MZ’ = 2.0 TeV 100 fb-1 Z rapidity Z rapidity rapidity-dependence of forward-backward asymmetry in Z+- decays for various models has a very distinctive behaviour Z rapidity I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  21. Z Forward-Backward Asymmetry ||  2.4, pT  20 GeV,  5rec strong mass-dependence of forward-backward asymmetry in Z+- !!! I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  22. GKK-resonance

  23. Large Extra Dimensions: RS1 L.Randall and R. Sundrum, Phys. Rev. Lett. 83,3370 (1999), Phys. Rev. Lett. 83,4690 (1999) • Our world is one of the branes embedded into the 5 dimensional anti-de Sitter space (non-factorizable geometry) with curvature k ds2 = e-2krc dxdx + r2cd2 • Configuration assumes 2 branes on the distance zC each from other: one with the positive tension  at z = 0, and the other with the negative tension - what is located at zC • SM matter lives on the 4-brane with induced Minkowski metric and the negative brane tension (RS1 scenario). The 4-al gravity in our World is induced by zero graviton mode • A fundamental scale parameter of the theory (not Planck scale) • Kaluza-Klein excitations of the graviton states (GKK) should be observable at collider energies as spin-2 individual resonances with masses mn = ke-krc xn , where are xn roots of the Bessel functions J1(xn) = 0. First excitation is • m1 = k x1e-krc = 3.83(k/MPl)~ a few TeV , where 0.01 < k/MPl < 1 I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  24. GKK graviton production (RS1) • virtual graviton: the SM exchange by  or Z boson interferes with the exchange by graviton (qq  GKK) • there is also gluon-gluon initiated graviton exchange process which has no the SM analogue (gg  GKK) • for real graviton production, i.e. graviton emission (qq  gGKK, qg qGKK, gg  gGKK) I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  25. GKK selection efficiency Pythia 6.217 + CMSJET 4.7, ||  2.4, pT  20 GeV, 3rec G ~ mGc2  I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  26. Signal/Background Events for GKK Pythia 6.217 + CMSJET 4.7, ||  2.4, pT  20 GeV Generated c = 0.1 d/dM, fb/GeV d/dM, fb/GeV c = 0.1 M, GeV M, GeV Response Background, DY I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  27. Detector response for GKK Pythia 6.25 + CMSJET 4.7, ||  2.4, pT  20 GeV I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  28. GKK Events Z m = 1.5 TeV 6000 events cos* Angular Distributions * is the angle of ’s in the Z (GKK) rest frame Theoretical expectations: ||  2.4, pT  20 GeV,  3rec qq  Z  (K=1), 100 fb-1 qq, gg  GKK   (K=1, c=0.1), 10 fb-1 F(x) = A0 + A1x + A2x2 +A3x3 + A4x4 I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  29. Angular Distributions * is the angle of ’s in the GKK rest frame qq, gg  GKK   (K=1, c=0.1) 100 fb-1 Events all  m = 1.5 TeV N  5.8104 pT > 20 is equivalent to pT > 100 GeV || < 2.4 || < 1.4 cos* I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  30. Mass reconstruction in ORCA 6.3.0 Full ORCA (L3, muon system + tracker) reconstruction Pythia ORCA Z (500) GKK (3000) ORCA reconstruction of high-pT muons still to be tuned !!! I. Golutvin, P. Moissenz, V. Palichik, M. Savina, S. Shmatov Prague, July 10, 2003

  31. Mass reconstruction in ORCA 6.3.0 Invariant mass of muon pairs from Pythia Full ORCA reconstruction of invariant mass Z (500) Z (500) Z (1200) Z (1200) gKK (3000)

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