1. Emily Thompson May 5 – UMass HEP Exp Group Meeting 1 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) 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 ) rec. muon p T (GeV/c) 1. 2.

2. Emily Thompson May 5 – UMass HEP Exp Group Meeting 2 example: eff(2.25 < η < 2.50) = n/N tag muon pT > 30 GeV/c n: probe found in MS N: all ID tracks

3. Emily Thompson May 5 – UMass HEP Exp Group Meeting 3 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: p T > 30 GeV/c truth matching to reconstructed track: –dR = (d η 2 + d Φ 2 ) ½ < 0.1 –might need to update the matching to include other parameters (ie: p T ) –use vertex eff is a function of truth p T or η, where in tag-probe, eff (ID track p T or η) combined muon truth muon passes truth muon fails dRcut

4. Emily Thompson May 5 – UMass HEP Exp Group Meeting 4 eff( probe η ) 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? Cuts: tag: p T > 30 GeV/c probe: p T > 8 GeV/c (errors scaled to correspond to 100 pb -1 ) N: (mu + any ID track) n: (mu + mu ID track) dimu mass (GeV/c 2 )

5. Emily Thompson May 5 – UMass HEP Exp Group Meeting 5 eff( probe η ) –> cleaned up Cuts: tag: p T > 30 GeV/c probe: p T > 30 GeV/c probe muon η - set background = 0 (totally suppressed by p T cut) - still no isolation cuts N: (mu + any ID track) n: (mu + mu ID track) dimu mass (GeV/c 2 )

6. Emily Thompson May 5 – UMass HEP Exp Group Meeting 6 eff( probe p T ) n N n N bin0 p T : 3->30 GeV/cbin1 p T : 30->38 GeV/c bin4 p T : 50->58 GeV/c n N bin: 012345678910 cuts: |η| < 2.5 Virtually no bckgnd after 30 GeV/c Besides background, there is an asymmetric tail due to p T binning …need an asymmetric fit dimu mass (GeV/c 2 ) uncertainty in tag-probe:2.0%4.0%2.4% 1.2% (errors scaled to correspond to 100 pb -1 )

7. Emily Thompson May 5 – UMass HEP Exp Group Meeting 7 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 Z (91 GeV): Z’ (1 TeV): rec. muon p T (GeV/c) MCtruth eff(p T ) Z (91 GeV) 0.934 ± 0.001 Z’ (1 TeV) 0.898 ± 0.004 Z’ (2 TeV) 0.906 ± 0.003 (p T = 15 – 60 GeV) (p T = 60 – 600 GeV) (p T = 600 – 1600 GeV) …some evidence of eff having a p T dependence (but also could be due to different η distributions)

8. Emily Thompson May 5 – UMass HEP Exp Group Meeting 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 p T dependence of eff for Z’ analysis cuts (ie: isolation cuts) move to AOD go further out in p T …beyond 200 GeV/c thanks!