PHOTON CONVERSION EFFICIENCY at CDF Focusing on: D ∗ 0 → D 0 γ D ∗ ± → D 0 π Paola Ruggiero Supervisor: Patrick Lukens 26th September 2013 Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 1 / 18
Introduction CDF detector Layers: • Silicon Detector • Central outer tracker • Electromagnetic Calorimeters • Hadronic Calorimeters • Muon Chambers Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 2 / 18
Introduction Conversion Process • Pair production when photons interact with matter • Probability of conversion almost constant at high energy • Precision of the tracking system for measurement of photon momentum Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 3 / 18
Introduction Why is it important? • Estimate the distribution and quantity of material in the detector • Looking at the conversion point we are able to “xray” the CDF detector • Application to the χ c 1 , 2 reconstruction: • recontruction of the charmonium states through the decay χ c 1 , 2 → J/ψ − γ • mass resolution sufficient to separate the χ 1 (3510) from the χ 2 (3555). Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 4 / 18
Introduction D ∗ 0 → D 0 γ vs D ∗ ± → D 0 π D MESONS: • D lightest particle containing charm quarks: • D ∗ is the first exited state: neutral and charged states • D ∗ 0 and D ∗ ± belong to the same isospin multiplet ISOSPIN SYMMETRY • Quantum number related to the strong interaction • Particles affected equally by the strong force but with different charges treated as being different states of the same particle • Isospin invariant production Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 5 / 18
Introduction Main goal of the project: Understanding whether the following expression can be used to obtain the conversion efficiency : ǫ D ∗ 1 = σ D ∗ = N D ∗ ± 0 0 σ D ∗ N D ∗ ǫ D ∗ ± ± 0 • N = number of candidates, from data • ǫ = efficiency, from simulations • Assumption : isospin invariant production (cross-sections ratio = 1) We expect the efficiency to be a strong functions of kinematics variables: • Transverse momentum • p T ( D ∗ ) bins (to use equality above) • p T ( γ ) (for each p T ( D ∗ ) bin, neutral case) Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 6 / 18
Introduction Efficiency ratio (from SIM): The photon efficiency is hidden in the efficiency ratio: ǫ D ∗ = N ( D ∗ ± → D 0 π ± [ reco ] ) ǫ D 0 ǫ π ✘ = ✘ ± N ( D ∗ 0 → D 0 γ [ gen ] ) ǫ ( γ ) ǫ D ∗ ǫ D 0 ǫ γ ✟ ✟ 0 • N ( D ∗ ± → D 0 π ± [ reco ] ) = reconstructed pions • N ( D ∗ 0 → D 0 γ [ gen ] ) = generated photons (small sample for γ [ reco ] ) • ǫ ( γ ) ⇒ UNKNOWN PARAMETER! Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 7 / 18
Introduction Efficiency for PHOTONS N ( D ∗ ǫ ( γ ) = N D ∗ ± → D 0 π ± [ reco ] ) 0 N ( D ∗ N D ∗ 0 → D 0 γ [ gen ] ) ± “Generated Photons” → Definition : • p T ( γ ) > 1 . 0 GeV • Conversion simulation (we generate the energy fraction taken by e + , e − , according to Rossi’s treatment for Bethe-Heitler conversion) • Acceptance simulation: p T ( e + , e − ) > 0 . 4 GeV • Efficiency simulation: ( π ) (CDF Note 8433) ⇒ ǫ ( γ ) = ǫ Reco ∗ ǫ Conv Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 8 / 18
Introduction Acceptance check: • Comparison (in simulations): • Reconstructed photons • Generated photons after acceptance and efficiency cuts N ( γ [ RECO ]) p T ( γ ) GeV N ( γ [ FAKE ]) N ( γ [ RECO ]) N ( γ [ F AKE ]) [1 . 0 , 1 . 3] 35851 ± 189 3743 ± 61 0.104 ± 0.002 [1 . 3 , 1 . 7] 47676 ± 218 4874 ± 70 0.102 ± 0.002 [1 . 7 , 2 . 2] 48252 ± 220 5144 ± 72 0.107 ± 0.001 [2 . 2 , 3 . 0] 54069 ± 233 5588 ± 75 0.103 ± 0.001 [3 . 0 , 4 . 0] 40603 ± 202 4420 ± 66 0.109 ± 0.002 [4 . 0 , 5 . 0] 23667 ± 154 2620 ± 51 0.111 ± 0.002 Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 9 / 18
Fitting Techniques Fitting Techniques DATA and SIMULATIONS Signal: Background: • 1 Gaussian • Line : a + bx • 2 Gaussians • Modified polynomial : aP 0 ( x ) + bP 1 ( x ) + cP 2 ( x ) * * M(#k π π [RECO])-M(#K π ) - M( π ) , 7 < p (D ) <11 M(#K π γ ) - M(#K π ), 14<p (D )<25, 1.0<p (Gamma)<1.3 T T T 30 1600 1400 25 1200 20 1000 800 15 600 10 400 5 200 0 0 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 0.05 0.1 0.15 0.2 0.25 0.3 M(#k [RECO])-M(#K ) - M( ) , 11 < p (D * ) <14 M(#K ) - M(#K ), 14<p (D * )<25, 1.3<p (Gamma)<1.7 π π π π π γ π T T T 45 600 40 500 35 400 30 25 300 20 200 15 10 100 5 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 M(#k [RECO])-M(#K ) - M( ) , 14 < p (D * ) <25 M(#K π γ ) - M(#K π ), 14<p (D )<25, p * (Gamma)> 1.7 π π π π T T T 350 100 300 80 250 200 60 150 40 100 20 50 0 0 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 0.05 0.1 0.15 0.2 0.25 0.3 Figure: D ∗ Figure: D ∗ ± , example 0 , example Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 10 / 18
Results Conversion efficiency: Results p T ( γ ) � p T ( D ∗ ) [7 , 11] [11 , 14] [14 , 25] [1 . 0 , 1 . 3] 0.066 ± 0.007 0.042 ± 0.009 0.037 ± 0.009 [1 . 3 , 1 . 7] 0.13 ± 0.04 0.080 ± 0.009 0.049 ± 0.009 > 1 . 7 0 ± 0 0.11 ± 0.06 0.072 ± 0.009 • We would expect to see similar results for photons with the same momentum (rows) • We would expect similar results too for different momentum of the photon (acceptance cuts included) • Efficiency seems to raise with p T ( γ ) and to fall with p T ( D ∗ ) Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 11 / 18
Results Sources of error (1): • Distribution of the decay angle for charged D* : � ��� � �� • DATA: D ∗ from different sources • SIM: D ∗ from B decay only � � ��� � hthetaCM SIM, Vec D* SIM, Vec D* hthetaCM SIM, Sc D* SIM, Sc D* hthetaCM DATA DATA Entries 51974 Entries 19388 Entries 19635 Mean 0.2804 Mean 0.3867 Mean 0.2384 800 1000 RMS 0.5191 RMS 0.618 RMS 0.5202 350 900 700 300 800 600 700 250 500 600 400 200 500 300 400 150 300 200 100 200 100 50 100 0 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 thetaCM thetaCM thetaCM Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 12 / 18
Results Source of error (1): • Important effect : the acceptance strongly depends on p T ( π ) ⇐ ⇒ θ • Range of full acceptance: p T ( D ∗ ± ) ∈ [14 , 25] GeV Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 13 / 18
Results Sources of error (2): • Isospin invariance ⇔ � p T ( D ∗ 0 ) � ∼ � p T ( D ∗ ± ) � • Condition NOT satisfied because of correlation between p T ( γ ) , p T ( D ∗ 0 ) ⇒ We should have not divided into p T ( γ ) bins Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 14 / 18
Results Final Result for Photon Conversion Efficiency • Angular distribution : Range of full acceptance • Isospin invariance : no binning on p T ( γ ) ⇒ We are left with only one range: p D ∗ ∈ [14 , 25] GeV ⇒ ǫ ( γ ) = 0 . 057 ± 0 . 004 Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 15 / 18
Conclusion Conclusions: • We know how to reconstruct the neutral D ∗ ( ∼ 1300 events processing only 4 periods) • We found a first estimate for the photon conversion efficiency: ǫ ( γ ) = 0 . 057 ± 0 . 004 • We found out acceptance issues that need to be fixed: • D ∗ ± → θ - distribution Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 16 / 18
Conclusion Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 17 / 18
Conclusion BACKUP (1): DATA and SIMULATION SAMPLES DATA: • xbhd0k , 4 periods out of 38 SIMULATIONS: • 2 Samples: equal number of events • Standard Event Generator used for B -decays • D ∗ allowed to decay naturally (PDG listings) D ∗ D ∗ B 0 → π + B + → π + 0 − → D 0 π − → D 0 γ Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 18 / 18
Recommend
More recommend
