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Feasibility to Study the Bc Meson and Testing Anomalous Gauge Couplings of

Feasibility to Study the Bc Meson and Testing Anomalous Gauge Couplings of the Higgs Boson via Weak-Boson Scatterings at CMS. CMS Group Institute of High Energy Physics, Chinese Academy of Science. Guilin 2006.10.29. Feasibility to Study the Bc Meson at CMS. Outline Introduction

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Feasibility to Study the Bc Meson and Testing Anomalous Gauge Couplings of

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  1. Feasibility to Study the Bc Meson and Testing Anomalous Gauge Couplings of the Higgs Boson via Weak-Boson Scatterings at CMS CMS Group Institute of High Energy Physics, Chinese Academy of Science Guilin 2006.10.29

  2. Feasibility to Study the Bc Meson at CMS

  3. Outline • Introduction • Process & results • Production of Signal & Backgrounds • Event selection, by studying Bc signal & backgrounds • Results • Summary

  4. Introduction

  5. Bc Meson • The Bc meson is the lowest-massbound state of a charm quark and a bottom anti-quark. It is the latest such meson predicted by the Standard Model. • Because Bc meson carry flavor, it provides a new window for studying heavy-quark dynamics for the two different heavy quarks, which is very different from the window provided by quarkonium. • Its mass is predicted to be And its lifetime is predicted to be between 0.4 and 0.7 ps V.V.Kiselev, PACS number:13.20.Gd,13.25.Gv, 11.55.Hx

  6. TEVATRON: CDF (1998) 20 J/ψ lυ events, mass : 6.40±0.39±0.13 GeV life time : ps

  7. 1998 2004 2005 Recent results of Bc Meson Experimental observation (CDF & D0 , Tevatron)

  8. CMS Experiment Large Hadron Collider 2008 CMS

  9. CMS Experiment

  10. LHC (14TeV) p p Production of Bc at LHC g-g fusion

  11. Adavantages of study Bc at CMS 1. Higher Collide Energy LHC: PP collider 2. Larger detector region than CDF The CMS detector has the similar structure as CDF ,but it has larger detector region than CDF. CMS: eta~(-2.5,2.5) CDF: eta~(-1.0,1.0) (RUN I) eta~(-1.5,1.5) (RUN II) (Muon system) 3. A better identification ability to muons The CMS detector has a better identification ability to muons ,this is more useful for the channels which include muon/muons in the final state.

  12. Goal & status • The goal: to measure the mass and life time of Bc with a larger statistics. • The first channel to look: Bc→J/ψ π (J/ψ →µµ) • First publication at about 1 fb-1

  13. Process & results

  14. The CMS Analysis chain HEPEVTNtuple MC generator ORCA OSCAR OSCAR 1)digitization 2)reconstruction 3)analysis SimReader RecReader RecReader Ntuplesignal POOLSimHits/signal ROOTTree POOL Digis DST Ntupleminbias POOLSimHits/minbias “data summary tape” User

  15. The CMS Fast Simulation HEPEVTNtuple MC generator FAMOS Ntuple POOL Simulation, Digis, and DST ROOTTree analysis

  16. Generator of Bc signal • BCVEGPY IPT, Beijing, by Chang et al. • Russian package IHEP, Protvino, by Berezhnoy et al. • PYTHIA BCVEGPY is used: faster agrees well with PYTHIA

  17. Bc signal About 30 1/fb Bc events were produced for efficiency study with both OSCAR/ORCA and FAMOS kine cut : Bc Pt≥10GeV |eta|≤2.0 Mu Pt≥4GeV |eta|≤2.2 Pion Pt≥2GeV |eta|≤2.4 Another independent 1/fb Bc were produced as data OSCAR_3_7_0 ORCA_8_7_3 FAMOS_1_3_2

  18. Backgrounds 1. Other B hadrons’ decay include J/ψ 2. Prompt J/ψ 3. ccbar→μμx 4. bbbar →μμx 5. General QCD, W+jets, Z+jets

  19. Backgrounds (1,2,3)generated by CMKIN & produced by FAMOS

  20. Backgrounds (4,5)CMS official production with OSCAR/ORCA

  21. Data Selection Selection I J/Ψ candidates: 2 muons Pt ≥ 4.0 GeV , |η|<=2.2 2 muons share the same vertex 2 muons have different charge 2 muons’ invariant mass around the J/Ψ [3.0,3.2]GeV Bc →J/ψπ (J/ψ →µµ)

  22. Selection II Pion candidate: Be not identified as a lepton Pt ≥ 2 GeV |η|<=2.4 Share the same vertex with 2 muons (J/Ψ vertex) Bc →J/ψ π (J/ψ →µµ)

  23. Selection III • Signal selection cuts: • cos(thetasp)>0.8 • thetasp: • is the angle between • the direction from the primary vertex to the second vertex and • the direction of the reconstructed Bcmomentum • PDLxy >60 μm (Proper decay length) • PDLxy /σxy>2.5 P. V. S. V.

  24. 1fb-1

  25. Selection IV Bc mass window (6.25, 6.55) GeV

  26. Summary of the Number of Events Normalize to 1fb-1 Total Bkgs: 2.6±0.4

  27. Bc number uncertainty source: • LO only • color singlet only (no color-octet available) • Values of inputs mass of b quark, c quark ; parton distribution function (pdf).

  28. Kinematic fitting Bc→J/ψπ, J/ψ→μμ Totally 3 tracks: 2 muon tracks: J/ψ mass constraint all the 3 tracks: share the same vertex

  29. M(Bc): 6402.0±22.0 MeV Input:6400MeV cτ(Bc): 148.8±13.1 μm Input 150 μm

  30. Systematic error source: • Misalignment 1. muon momentum scale uncertainty 2. muon momentum resolution deterioration 3. vertex resolution deterioration • Efficiency uncertainty • Theoretical uncertainty • Cuts sensitivity

  31. Summary of systematic error

  32. Summary

  33. Summary • With MC data, the feasibility for CMS to measure the mass and the lifetime of Bc meson was studied. • The study focus on the decay channel Bc→J/ψπ. • 120 events can be selected with the first 1 fb-1data • Mass resolution is estimated to be • cτ resolution is corresponding to the lifetime error to be • Uncertainty: effects of misalignment, theoretical uncertainty on the Bc Pt distribution, and limited Monte Carlo statistics.

  34. Continue… • This study had been reported for 6 times at CERN. • This study had been written into 2 notes: CMS Notes & Analysis Notes And Physics TDR. • The results can be available from the following website http://cmsdoc.cern.ch/doc/notes/docs/NOTE2006_118

  35. Testing Anomalous Gauge Couplings of the Higgs Boson via Weak-Boson Scatterings at CMS Outline 1. Motivation 2. Extraction of anomalous coupling constants via Neural Network 3. Study of signal and backgrounds 4. Summary & to do list

  36. Motivation • whether there exists a sub-TeV Higgs Boson. 2. Discriminate the EWSB sector of the new physics model from that of the SM.

  37. Zhang Bin and Kuang Yuping et. al.(Tsinghua Univ.) proposed a sensitive way of testing AHVVC via VV (V = W+ , Z0 )scatterings, especially the WW scatterings at LHC and provided the matrix element level generator . It is d u v p + W + l + W --------- H + v W + + p u W l d

  38. among them, fw and fww are the most sensitive ones. Hence, only fw and fww are considered.

  39. To suppress backgrounds, the cuts suggested by theorists

  40. Distribution of the number of events with fw Normalized to 300 fb-1 mH=115 GeV

  41. For the small number of events, large fluctuation occurred. For the number of events fluctuated according Poisson distribution, the neural network can make the resolution of parameter fw better after taking the distribution of two leptons’ invariant mass as one of the inputs.

  42. Extract anomalous coupling constant fw via Neural Network

  43. Neural Network inputs: (1) number of events (2) distribution of the invariant mass of 2 leptons. outputs: anomalous coupling constants fw training: fw =0 ,1,2,3,4 evaluate: fw =1.5 ,2.5

  44. Distribution of two leptons’ invariant mass Normalized to 300 fb-1

  45. bin 1 2 3 4 two leptons’ invariant mass (GeV) 0 ~ 480 480 ~ 960 960 ~ 2200 2200 ~ 4000

  46. Evaluated f w = 1.5

  47. Evaluated f w = 2.5

  48. Study of signal and backgrounds

  49. Reconstruction results of the Signal

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