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Tag-probe method: Fitting Z → μ + μ - mass peaks

rec. muon p T (GeV/c). Tag-probe method: Fitting Z → μ + μ - mass peaks. Motivation: 1. Want to use long p T tail of muon from Z to extrapolate to high p T regime where Z’ might live (1TeV - 2TeV) 2. Also include low p T muons (< 30 GeV/c)

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Tag-probe method: Fitting Z → μ + μ - mass peaks

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  1. rec. muon pT (GeV/c) Tag-probe method:Fitting Z →μ+μ-mass peaks • Motivation: 1. Want to use long pT tail of muon from Z to extrapolate to high pT regime where Z’ might live (1TeV - 2TeV) 2. Also include low pT muons (< 30 GeV/c) • need loose selection criteria to allow for softer muons • so far no hard cuts or isolation on ID probe track • CBNT level analysis, using MuidCombined muons so far • Release 12 sample Pythia Z →μ+μ- (using ~250K events corresponding to ~150 pb-1) 2. 1.

  2. N: all ID tracks example: eff(2.25 < η < 2.50) = n/N tag muon pT > 30 GeV/c n: probe found in MS

  3. dRcut combined muon truth muon passes truth muon fails eff crosscheck with MCtruth • compare tag-probe fits with truth • would like to count only muons which came from Z • # true muons > 1 (within |η|<2.7) • Hard cut on truth muons: pT > 30 GeV/c • truth matching to reconstructed track: • dR = (dη2 + dΦ2)½ < 0.1 • might need to update the matching to include other parameters (ie: pT) • use vertex • eff is a function of truth pT or η, where in tag-probe, eff (ID track pT or η)

  4. N:(mu + any ID track) dimu mass (GeV/c2) n:(mu + mu ID track) dimu mass (GeV/c2) eff( probe η ) Cuts: • tag: pT > 30 GeV/c • probe: pT > 8 GeV/c (errors scaled to correspond to 100 pb-1) probe muon η - Bias may come from MCtruth method not corresponding exactly to tag-probe? - in mu+mu plot: asymmetry in histo from background or signal?

  5. N:(mu + any ID track) dimu mass (GeV/c2) n:(mu + mu ID track) dimu mass (GeV/c2) eff( probe η ) –> cleaned up Cuts: • tag: pT > 30 GeV/c • probe: pT > 30 GeV/c probe muon η • set background = 0 • (totally suppressed by pT cut) • - still no isolation cuts

  6. bin: 0 1 2 3 4 5 6 7 8 9 10 eff( probe pT ) cuts: • |η| < 2.5 • Virtually no bckgnd after 30 GeV/c Besides background, there is an asymmetric tail due to pT binning …need an asymmetric fit 1.2% uncertainty in tag-probe: 2.4% 4.0% 2.0% (errors scaled to correspond to 100 pb-1) bin4 pT: 50->58 GeV/c bin0 pT: 3->30 GeV/c bin1 pT: 30->38 GeV/c N N N dimu mass (GeV/c2) dimu mass (GeV/c2) dimu mass (GeV/c2) n n n

  7. Z (91 GeV): rec. muon pT (GeV/c) Z’ (1 TeV): (pT = 15 – 60 GeV) (pT = 60 – 600 GeV) rec. muon pT (GeV/c) (pT = 600 – 1600 GeV) MCtruth efficiency Z to Z’ • Quick check (on release 11) • How does the eff scale at higher energies? • Look at MCtruth eff in a wide bin from Z, Z’ • |η| < 2.5 …some evidence of eff having a pT dependence (but also could be due to different η distributions)

  8. to do list: • better fit? • signal and background separation • use asymmetric fit function rather than BW? • is asymmetry coming from signal or resolution? • examine the shape of the diMu background dist. • look at new release 12 Z’ samples • examine pT dependence of eff for Z’ analysis cuts (ie: isolation cuts) • move to AOD • go further out in pT…beyond 200 GeV/c thanks!

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