在Tevatron上测量前后不称性

【摘要】： This dissertation describes a measurement of the forward-backward asymmetry (AFB) in pp→Z/γ*→ee events using 5.0 fb-1 data collected by the D(?) detector at the Fermilab Tevatron. The AFB is measured as a function of the invariant mass of the electron-positron pair. Along with obtaining normalized differential cross section 1/σ×dσ/dM and Z to light quark couplings, we measured the Standard Model(SM) fun-damental parameter, the effective weak mixing angle sin2θefflept, with an unprecedented precise in light quark sector, namely the single D(?) measurement has surpassed the LEP combination of four experiment results of inclusive hadronic charge asymmetry. Publications as Primary Author ●"Measurement of the forward-backward charge asymmetry and extraction of sin2θWeff in pp→Z/γ*→e+e-+X events produced at (?)=1.96 TeV", V. M. Abazov et al. Phys. Rev. Lett.101,191801 (2008). ●"Search for scalar neutrino particles in e+μfinal states in pp collisions at (?)= 1.96 TeV", V. M. Abazov et al. Phys. Rev. Lett.100,241803 (2008). ●"Search for (?) sneutrino particles in the electron plus muon final state at D(?)", conference note 5894. ●"Search for high-mass narrow resonances in the di-electron channel at D(?)", con-ference note 5923. D(?) Notes as Primary Author ●Note 5603:Measurement of the forward-backward charge asymmetry in pp→Z/γ*+X→ee+X events produced at (?)=1.96 TeV (RunⅡa) ●Note 5867:Measurement of the forward-backward charge asymmetry in pp→Z/γ*+X→ee+X events produced at (?)=1.96 TeV (RunⅡb) ●Note 5299:Search for sneutrino resonance in the e+μ, final states in RPV SUSY at D(?) (RunⅡa) ●Note 5648:Search for sneutrino resonance in the e+μfinal states in RPV SUSY at D(?) (RunⅡb) ●Note 5894:Search for sneutrino resonance in the e+μfinal states in RPV SUSY at D(?) (RunⅡb conference note) ●Note 5564:A Study of electron charge misidentification in RunⅡa data ●Note 5635:Study of electron track matching parameters with RunⅡb data ●Note 5761:Electron and photon identification with p20 data Presentations ●"Measurement of AFB and Extraction of sin2θWeff in pp→Z／γ*→e+e-+X' APS April Meeting,St.Louis,MO,April 14th,2008. ●"Measurement of the Forward-Backward Charge Asymmetry(AFB)in pp→Z／γ*→e+e- events at (?)=1.96 TeV",Lake Louise Winter Institute 2010 Conference,Alberta,Canada, Feb.16th,2010. ●Major D(?) internal talks: —"Stability check of Calorimeter calibration",Calorimeter Algorithm meet-ing,Fermilab,Nov.27,2007 —"p20 electron track match study",Calorimeter Algorithm meeting,Fermi-lab,Feb.20,2008 —"Update on Diem trigger OR-V15 study",Trigger study Group meeting, Fermilab,Feb.21,2008 —"Measurement of AFB and Extraction of sin2θWeff pp→Z／γ*→+e+e-+X ",All D(?) meeting,Fermilab,April 4,2008: —"Stability check of Calorimeter calibration",Calorimeter Algorithm meet-ing,Fermilab,Oct.8,2008 —"Stability check of Calorimeter calibration",Calorimeter Algorithm meet-ing,Fermilab,Jan.7,2009 —"Energy scale lumi dependence", Electron identification meeting, Fermilab, Oct.1,2009 —"(?) inter-calibration of Calorimeter", Calorimeter calibration meeting, Fer-milab, Dec.10,2009 —"Measurement of Forward-Backward Asymmetry(AFB) in pp→Z/γ*→e+e-+X", Electroweak meeting meeting, Fermilab, Dec.10,2009 The main innovations in this thesis are listed blow: ●DI-ELECTRON TRIGGER EFFICIENCY: Determined the di-electron trigger efficiency for the first time at D(?). With increasing instantaneous luminosity, the OR of single electron triggers is not fully efficient for electrons with transverse momentum (pT) less than 30 GeV. This threshold (30 GeV) is too tight for many analyses. Di-electron trigger can be used to improve the trigger efficiency in low pT region, almost all analyses with di-electron or diphoton final state (precision measurements of Z boson properties using Z→ee events, search for new di-electron resonance and search for SM Higgs boson in H→γγchannel) benefit from this study. ●ELECTRON TRACK MATCH: Studied the electron track-matching requirement for RunⅡb data, the new re-quirement has greatly reduced the probability for a jet to fake an electron. ●ELECTRON ENERGY CORRECTION: Studied the electron energy scale versus instantaneous luminosity and derived correction factors. This correction helped to improve the electron energy resolu-tion for the whole RunⅡb data. ●INTER-CALIBRATION OF CALORIMETERS: Performed (?)inter-calibration for both the electromagnetic and hadronic calorime-ters after the 2009 shutdown. The (?) inter-calibration is mainly to uniformize the response of eachηring and reduce the constant term for the calorimeter energy resolution. This is very important for almost all analyses done at D(?). Performed the stability check of calibration constants every six months since July 2007 and monitored the calorimeter performance over time. ●ELECTRON ENERGY SCALE/RESULUTION: Studied the energy scale/resulution of electron, which make the Monte Carlo has a reasonable agreement with real data in the Z-pole region. The agreement in Z-pole mass region make the precise measurements of W and Z bosons'properties is possible. ●UNFOLDING: Distributions measured in high-energy physics(HEP) experiments are often dis-torted or transformed by limited acceptance and finite resolution of the detectors. The unfolding of measured distributions is an important, in this analysis, we used the response matrices method to do the unfolding. ●HIGH ORDER CORRECTIONS: The Geant Monte Carlo(MC) used in D(?) is PYTHIA, which is a leading or- der(LO) generator. In this analysis, in order to compare the measurements di-rectly with LEP and SLD results, we do the next-next-to-leading order(NNLO) k-factor correction at first, and then with the next-to-leading order(NLO) genera-tor ZGRAD2, we measured the NLO EW final state radiation (FSR) corrections, and apply 2D(MZ-cosθ*) reweighting on the signal, which make precise mea-surements on Tevatron can compared with LEP, SLD directly.