PHOTON CONVERSION EFFICIENCY at CDF Focusing on: D 0 D 0 D D - - PowerPoint PPT Presentation

▶
photon conversion efficiency at cdf
SMART_READER_LITE
LIVE PREVIEW

PHOTON CONVERSION EFFICIENCY at CDF Focusing on: D 0 D 0 D D - - PowerPoint PPT Presentation

Mar 09, 2023 561 likes •754 views

PHOTON CONVERSION EFFICIENCY at CDF Focusing on: D 0 D 0 D D 0 Paola Ruggiero Supervisor: Patrick Lukens 26th September 2013 Paola Ruggiero (Supervisor: Patrick Lukens ) PHOTON CONVERSION EFFICIENCY at CDF 26th

slide-1
SLIDE 1

PHOTON CONVERSION EFFICIENCY at CDF

Focusing on: D∗

0 → D0γ

D∗

± → D0π

Paola Ruggiero

Supervisor: Patrick Lukens

26th September 2013

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 1 / 18

slide-2
SLIDE 2

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

slide-3
SLIDE 3

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

slide-4
SLIDE 4

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 χc1,2 reconstruction:
  • recontruction of the charmonium states through the decay χc1,2 → J/ψ − γ
  • mass resolution sufficient to separate the χ1(3510) from the χ2(3555).

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 4 / 18

slide-5
SLIDE 5

Introduction

D∗

0 → D0γ vs D∗ ± → D0π 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

slide-6
SLIDE 6

Introduction

Main goal of the project:

Understanding whether the following expression can be used to obtain the conversion efficiency: 1 = σD∗ σD∗

±

= ND∗ ND∗

±

ǫD∗

±

ǫD∗

  • 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
  • pT (D∗) bins (to use equality above)
  • pT (γ) (for each pT (D∗) bin, neutral case)

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 6 / 18

slide-7
SLIDE 7

Introduction

Efficiency ratio (from SIM):

The photon efficiency is hidden in the efficiency ratio: ǫD∗

±

ǫD∗ = ✘ ✘ ǫD0 ✟ ✟ ǫD0 ǫπ ǫγ = N(D∗

± → D0π±[reco])

N(D∗

0 → D0γ[gen])ǫ(γ)

  • N(D∗

± → D0π±[reco]) = reconstructed pions

  • N(D∗

0 → D0γ[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

slide-8
SLIDE 8

Introduction

Efficiency for PHOTONS

ǫ(γ) = ND∗ ND∗

±

N(D∗

± → D0π±[reco])

N(D∗

0 → D0γ[gen])

“Generated Photons” → Definition:

  • pT (γ) > 1.0GeV
  • Conversion simulation (we generate the energy fraction taken by e+, e−,

according to Rossi’s treatment for Bethe-Heitler conversion)

  • Acceptance simulation: pT (e+, e−) > 0.4GeV
  • Efficiency simulation: (π) (CDF Note 8433)

⇒ ǫ(γ) = ǫReco ∗ ǫConv

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 8 / 18

slide-9
SLIDE 9

Introduction

Acceptance check:

  • Comparison (in simulations):
  • Reconstructed photons
  • Generated photons after acceptance and efficiency cuts

pT (γ) GeV N(γ[FAKE]) N(γ[RECO])

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

slide-10
SLIDE 10

Fitting Techniques

Fitting Techniques

DATA and SIMULATIONS

Signal:

  • 1 Gaussian
  • 2 Gaussians
0.05 0.1 0.15 0.2 0.25 0.3 5 10 15 20 25 30 (Gamma)<1.3 T )<25, 1.0<p * (D T ), 14<p π ) - M(#K γ π M(#K 0.05 0.1 0.15 0.2 0.25 0.3 5 10 15 20 25 30 35 40 45 (Gamma)<1.7 T )<25, 1.3<p * (D T ), 14<p π ) - M(#K γ π M(#K 0.05 0.1 0.15 0.2 0.25 0.3 20 40 60 80 100 (Gamma)> 1.7 T )<25, p * (D T ), 14<p π ) - M(#K γ π M(#K

Figure: D∗

0, example

Background:

  • Line: a + bx
  • Modified polynomial:

aP0(x) + bP1(x) + cP2(x)

0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 200 400 600 800 1000 1200 1400 1600 ) <11 * (D T ) , 7 < p π ) - M( π [RECO])-M(#K π π M(#k 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 100 200 300 400 500 600 ) <14 * (D T ) , 11 < p π ) - M( π [RECO])-M(#K π π M(#k 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 50 100 150 200 250 300 350 ) <25 * (D T ) , 14 < p π ) - M( π [RECO])-M(#K π π M(#k

Figure: D∗

±, example

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 10 / 18

slide-11
SLIDE 11

Results

Conversion efficiency: Results

pT (γ)pT (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 pT (γ) and to fall with pT (D∗)

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 11 / 18

slide-12
SLIDE 12

Results

Sources of error (1):

  • Distribution of the decay angle

for charged D*:

  • DATA: D∗ from different sources
  • SIM: D∗ from B decay only
  • thetaCM
  • 1 -0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1 100 200 300 400 500 600 700 800 900 1000 DATA hthetaCM

Entries 51974 Mean 0.2804 RMS 0.5191

DATA thetaCM

  • 1
  • 0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1 100 200 300 400 500 600 700 800 SIM, Vec D* hthetaCM

Entries 19388 Mean 0.3867 RMS 0.618

SIM, Vec D* thetaCM

  • 1
  • 0.8 -0.6 -0.4 -0.2

0.2 0.4 0.6 0.8 1 50 100 150 200 250 300 350 SIM, Sc D* hthetaCM

Entries 19635 Mean 0.2384 RMS 0.5202

SIM, Sc D*

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 12 / 18

slide-13
SLIDE 13

Results

Source of error (1):

  • Important effect : the acceptance strongly depends on pT (π) ⇐

⇒ θ

  • Range of full acceptance: pT (D∗

±) ∈ [14, 25]GeV

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 13 / 18

slide-14
SLIDE 14

Results

Sources of error (2):

  • Isospin invariance ⇔ pT (D∗

0) ∼ pT (D∗ ±)

  • Condition NOT satisfied because of correlation between pT (γ), pT (D∗

0)

⇒ We should have not divided into pT (γ) bins

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 14 / 18

slide-15
SLIDE 15

Results

Final Result for Photon Conversion Efficiency

  • Angular distribution: Range of full acceptance
  • Isospin invariance: no binning on pT (γ)

⇒ We are left with only one range: pD∗ ∈ [14, 25]GeV

⇒ ǫ(γ) = 0.057 ± 0.004

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 15 / 18

slide-16
SLIDE 16

Conclusion

Conclusions:

  • We know how to reconstruct the neutral D∗ ( ∼ 1300 events processing
  • nly 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

slide-17
SLIDE 17

Conclusion Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 17 / 18

slide-18
SLIDE 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)

B0 → D∗

−

π+ → D0π− B+ → D∗ π+ → D0γ

Paola Ruggiero (Supervisor: Patrick Lukens) PHOTON CONVERSION EFFICIENCY at CDF 26th September 2013 18 / 18