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Muon Fake Rates

Muon Fake Rates. Concept: determine rate of fake muons due to pion/kaon punch-through (PT) muons out of pion/kaon decay-in-flight (DIF) METHOD 1: Use source of identified high-pt pions/kaons: reconstruct K s pp reconstruct D 0 K p

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Muon Fake Rates

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  1. Muon Fake Rates • Concept: determine rate of • fake muons due to pion/kaon punch-through (PT) • muons out of pion/kaon decay-in-flight (DIF) • METHOD 1: Use source of identified high-pt pions/kaons: • reconstruct Kspp • reconstruct D0 Kp • METHOD 2: Use generic tracks (min bias) • METHOD 3: Use simulated pions and kaons (fake event)

  2. Ks Selection • Use B_CHARM dataset: • L1: (2 XFT tracks, opp. charge, Df < 1350 , SPt > 5.5) or (7 tracks w/ Pt > 2) • L2: 2 SVT tracks, c2 < 25, Pt > 2, 100 mm < |d0| < 1 mm • L3: 2 SVX-COT hybrid tracks, Pt > 2, |h| < 1.2, 120 mm < |d0| < 1 mm, • opp. charge, |DZ0| < 5 cm, 20 < |Df| < 900, Lxy > 200 mm, SPt > 5.5 • Offline selection: • Track cuts: Nax > 24, Nst > 24, |Z0| < 60 cm, |h| < 1.2, Pt > 2 • Track pairs: opp. charge, |DZ| < 5 cm, 20 < |Df| < 900, 1 leg Pt > 5 • Secondary vertex fit: CTVMFT algorithm, x2 < 8, Lxy > 1 cm, • d0(Ks) < 0.3 mm (SVX) / d0(Ks) < 0.3 cm (COT)

  3. Ks Peak – BCHARM sample Peak: 0.46 < Mpp < 0.53 SB: 0.425 < Mpp < 0.46 0.53 < Mpp < 0.565 Mpp [GeV]

  4. Pions – Kinematics d0 (COT) d0 (SVX) peak sideband eta d0 (SVX) : both legs have silicon hits d0 (COT) : only one leg or none have silicon hits Pt [GeV]

  5. Muon Cuts • Use same cuts as in s(W mn) analysis (summer): • Tracking: Nax > 24, Nst > 24 • Calorimeter, isolation: E(R<0.4)corrected for track < 2 • (will apply this later, study fake rate as function of iso) • Calorimeter, MIP: Eem < max(2, 2+0.0115 (Pt – 100)) • Ehad < max(6, 6+0.028 (Pt – 100)) • Matching: |Dx|CMU < 3 cm, |Dx|CMP < 6 cm, (no cut for CMX)

  6. Fake Rate – Ks • Ks in peak: 74,843 • (Pt>2): 149,686 [%] • is m: 598 = 0.40 +- 0.02 Muon fake rate from • is CMU m: 405 = 0.27 +- 0.01 PT and DIF [%]: • is CMP m: 183 = 0.12 +- 0.01 • is CMUP m: 133 = 0.09 +- 0.01 peak – SB: • is CMX m: 146 = 0.10 +- 0.01 all m: 0.38 +- 0.02 CMU m: 0.26 +- 0.01 Events in SB: 2,925 CMP m:0.11 +- 0.01 p (Pt>2): 5,850 [%] CMUP m: 0.08 +- 0.01 p is m: 52 = 0.89 +- 0.12 CMX m: 0.09 +- 0.01 p is CMU m: 26 = 0.44 +- 0.09 p is CMP m: 19 = 0.32 +- 0.07 p is CMUP m: 13 = 0.22 +- 0.06 p is CMX m: 21 = 0.36 +- 0.08

  7. Fake Rate – differential distributions eta Pt [GeV] Muon phi [degrees]

  8. Fake Rate – different datasets ELECTRON BTST2 BCHARM PHOTON DIPHOTON ALL

  9. Fake Rate – data and MC BCHARM ELECTRON PHOTON DIPHOTON JETS DATA MC

  10. Other samples electron sample photon sample Mpp [GeV] Mpp [GeV]

  11. Physics Bias ? Study physics bias in different data samples: fakerate dependent on “business” of the event… In muon enriched samples the pion track gets accidentally matched to the stub from a real muon nearby Check 1:loosen / tighten |Dx| cut on CMU, CMP : fake rate / Check 2: difference between isolated/non-isolated tracks/muons ?

  12. Muon Matching Tendency also seen in electron dataset…but within statistical error… |Dx|<15 cm |Dx| < 3 / 6 cm |Dx| < 1 cm ELECTRONS BCHARM BCHARM dataset (=two-track trigger) is muon enriched (heavy flavor…)

  13. Track Isolation track iso < 2 GeV track iso > 2 GeV pions from Ks pions from D0 kaons from D0 BCHARM PHOTONS ELECTRONS DIPHOTONS

  14. D0 Selection • Based on same BCHARM dataset as Ks selection • Selection close to the one in the D0 branching ratio analysis • Use only SVT matched offline tracks: • | foffline – fSVT | < 0.015 , | curvoffline – curvSVT | < 0.00015 , c2SVT < 25 , NSVXrf >= 3 • Extra cleanup: • d01 * d02 < 0 (for K-p pair) • not used: reconstruct D* peak (D*->D0ps) , cut on q(ps) != q(K) , • cut on Dm = m(Kpps)-m(Kp)

  15. D0 Peak Peak: 1.83 – 1.90 GeV Sidebands: 1.765 – 1.80 & 1.93 – 1.965 GeV MKp [GeV]

  16. Fake Rate – D0 Muon fake rates fromPT and DIF [%]: pions Kaons pions from Ks all m: 0.46 +- 0.03 0.75 +- 0.03 0.38 +- 0.02 CMU m: 0.31 +- 0.02 0.56 +- 0.03 0.26 +- 0.01 CMP m:0.08 +- 0.010.14 +- 0.01 0.11 +- 0.01 CMUP m: 0.03 +- 0.01 0.10 +- 0.01 0.08 +- 0.01 CMX m: 0.10 +- 0.01 0.14 +- 0.01 0.09 +- 0.01

  17. Fake Rate – diff. distr. • from Ks • from D0 K from D0

  18. Fake Rate – charge dependence Q>0 Q<0 • from Ks • from D0 K from D0

  19. Comparison to Run1 Numbers • Method in Run1: • use inclusive photon sample, look for isolated high-pt tracks therein • compute probability for PT per track from hadronic interaction lengths • compute probability for DIF per track from ctp / ctK • sum over all high-pt tracks in sample • see: Thesis by J.Berryhill, PRD of note 5569; no dedicated note found • Results: • In Run1: • 1.87 +- 0.99 PT background events • 1.08 +- 1.20 DIF background events • 2.95 +- 2.19 background events DIF+PT • Using (0.49 +- 0.04)% fake rate for Run2 (1/3 K + 2/3 p) • Combine with 398 high-Pt tracks: • 1.95 +- 0.16 +- 0.88 background events estimated with this method (DIF+PT)

  20. METHOD 3 – Single Pions and Kaons - 1 Simulate single pions and kaons with fake-event generator 10 particles per event ; flat pt spectrum ; apply track and muon cuts as in METHOD 1: Pions Kaons 0.24 +- 0.02 % (all tracks) 0.58 +- 0.03 % 0.31 +- 0.06 % (pt<5 GeV) 0.68 +- 0.09 % 55.5 % are DIF 67.9 % are DIF

  21. METHOD 3 – Single Pions and Kaons - 2

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