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The study of 𝜓′ → 𝑒+𝑒−𝜒𝑐0,1,2

Zhang Jielei Zhang Jingzhi

Outline

1、Motivation

2、Data sets

3、The study of 𝜓′ → 𝑒+𝑒−𝜒𝑐0,1,2

Event selection

Data and Background study

Data and MC distributions

4、Summary

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Motivation

In theory, the transition process 𝜓′(′) → 𝛾𝜒𝑐𝐽 is not consistent with experiment measurement very well.

Q. Zhao et al consider open charm effects, many channels can consistent with experiment measurement very well except for 𝜓′ → 𝛾𝜒𝑐2.

In the process 𝜓′ → 𝑒+𝑒−𝜒𝑐𝐽, 𝑒+𝑒− from a virtual photon. To study the process can

provide more information for theory. Furthermore, we can get the distribution of form factor, from the distribution we can extract parameters as theoretical input.

Data sets

Boss Version : 6.6.4-p03

Data sets :

Signal MC :

𝜓′ → 𝑒+𝑒−𝜒𝑐0,1,2(DIY), 𝜒𝑐0,1,2 → 𝛾𝐽/𝜓, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

Inclusive MC (2009 and 2012 𝜓′ MC)

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106 M 𝜓′ of year 2009341.5 M 𝜓′ of year 2012continuum background study : ~44pb−1 data @ 3650

Background MC :

1.𝜓′ → 𝛾𝜒𝑐0,1,2, 𝜒𝑐0,1,2 → 𝛾𝐽/𝜓, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

2.𝜓′ → 𝜂𝐽/𝜓, 𝜂 → 𝛾𝛾, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

3.𝜓′ → 𝜂/𝜋0𝐽/𝜓, 𝜂/𝜋0 → 𝛾𝑒+𝑒−, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

Event selections

Charged tracks- 𝑅𝑥𝑦 < 1𝑐𝑚, 𝑅𝑧 < 10𝑐𝑚

- 𝑐𝑜𝑠𝜃 < 0.93- 𝑁 = 4, 𝑄 = 0

Good photon- 0 ≤ 𝑇𝐷𝐶 ≤ 14- Barrel :𝐸 > 0.025 GeV, 𝑐𝑜𝑠𝜃 < 0.8

- Endcap :𝐸 > 0.050 GeV, 0.86 < 𝑐𝑜𝑠𝜃 < 0.92

- ∆𝜃 > 200

- 𝑁𝛾 ≥ 1

Particle separation- 𝑒 from 𝜓′ ∶ 𝑃𝑚𝑑𝑐 < 1 GeV- 𝑒 from 𝐽/𝜓 ∶ 𝑃𝑚𝑑𝑐 > 1 GeV&&𝐸𝑒𝑚𝑐 >1 GeV- 𝜇 from 𝐽/𝜓 ∶ 𝑃𝑚𝑑𝑐 > 1 GeV&&𝐸𝑒𝑚𝑐 <0.4 GeV

4C kinematic fit- Choose the photon with least 𝜒2

- 𝜒4𝐶2 < 40

Other selections- 𝐽/𝜓 mass window : (3.08, 3.12) GeV- 0.16 < 𝑀 𝛾𝑒+𝑒− < 0.50 GeV- 𝑅𝑥𝑦 < 1.5||𝑅𝑥𝑦 > 7.0 cm

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𝜒4𝐶2 of kinematic fit

𝜒2 distribution from 4C : 𝜒4𝐶2 < 40

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𝐽/𝜓 invariant mass distributions7

𝐽/𝜓 mass window : 3.08 < 𝑀 𝑙+𝑙− < 3.12 GeV

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Background study

The main background :

1.𝜓′ → 𝛾𝜒𝑐0,1,2, 𝜒𝑐0,1,2 → 𝛾𝐽/𝜓, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

2.𝜓′ → 𝜂𝐽/𝜓, 𝜂 → 𝛾𝛾, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

3.𝜓′ → 𝜂/𝜋0𝐽/𝜓, 𝜂/𝜋0 → 𝛾𝑒+𝑒−, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇−

𝛾 conversion

Same final state

𝑅𝑥 VS 𝑅𝑦 distributions9

Background(𝛾𝜒1)

Background(𝛾𝜒2)

DATA(𝜒1)

DATA(𝜒2)

Some variables from GammaConv package.

MC(𝜒1)

MC(𝜒2)

𝛾 conversion MC

in 𝜒𝑐1 region

in 𝜒𝑐2 region

𝑅𝑥𝑦 distributions10 Remove 𝛾 conversion background

𝑅𝑥𝑦 < 1.5||𝑅𝑥𝑦 > 7.0 cm

From 𝛾 conversion MC, there are no events in the region. These events have large angle between 𝑒+ and 𝑒−. For signal MC, if the 𝑒+

and 𝑒− have large angle, the event will be reconstructed in the region.

𝛾 conversion events

𝑀(𝛾𝑒+𝑒−) distributions11

0.16 < 𝑀 𝛾𝑒+𝑒− < 0.50 GeV

Remove 𝜓′ → 𝜂/𝜋0𝐽/𝜓, 𝜂/𝜋0 → 𝛾𝑒+𝑒−, 𝐽/𝜓 → 𝑒+𝑒−/𝜇+𝜇− process

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Background study

From inclusive MC, we find only one events survived.

From 44 pb−1 3650 data sample, only one event survived the event selections.

𝑀(𝛾𝐽/𝜓) distributions13

Clear 𝜒𝑐1 and 𝜒𝑐2 signal, and some 𝜒𝑐0 signal

𝜓′ → 𝛾𝜒𝑐𝐽 , 𝜒𝑐𝐽 → 𝑒+𝑒−𝐽/𝜓 process

𝑅𝑀(𝑒+𝑒−) distributions14

𝑒+𝑒− recoiling invariant mass distribution 𝑅𝑀(𝑒+𝑒−)

(before 4C kinematic fit)

Clear 𝜒𝑐1 and 𝜒𝑐2 signal, and some 𝜒𝑐0 signal

𝜃𝑒+𝑒−distributions15

The angular distribution between 𝑒+ and 𝑒− in 𝜒𝑐1

and 𝜒𝑐2 signal region

Momentum distributions16

𝑒+ and 𝑒− momentum distribution in 𝜒𝑐1 and 𝜒𝑐2

signal region

𝑐𝑜𝑠𝜃 distributions17

𝑒+ and 𝑒− 𝑐𝑜𝑠𝜃 angular distribution in 𝜒𝑐1 and 𝜒𝑐2

signal region

Invariant mass distributions18

𝑀(𝑒+𝑒−), 𝑀(𝑒+𝜒𝑐1,2) and 𝑀(𝑒−𝜒𝑐1,2) distribution in 𝜒𝑐1

and 𝜒𝑐2 signal region

Helicity 𝑐𝑜𝑠𝜃 distributions19

𝑒+ and 𝑒− helicity angular distribution in 𝜒𝑐1 and 𝜒𝑐2

signal region

Scatter plots20

𝜃𝑒+𝑒− VS 𝑅𝑥𝑦, 𝑀(𝑒+𝑒−) VS 𝑅𝑥𝑦 and 𝜃𝑒+𝑒− VS 𝑀(𝑒+𝑒−)

distributions for data.

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Signal extraction from data

Signal : MC-determined shape to describe signal 𝜒𝑐0,1,2, the 𝑁𝜒𝑐0,1,2 is float

Background : 1、1-st order polynomial, the 𝑁𝑏𝑘𝑔1 are float2、𝜓′ → 𝛾𝜒𝑐0, 𝜒𝑐0 → 𝑒+𝑒−𝐽/𝜓 process MC-determined shape, the 𝑁𝑏𝑘𝑔2 are float

𝑁𝜒𝑐0 = 62 ± 10 𝑁𝜒𝑐1 = 884 ± 30 𝑁𝜒𝑐2 = 229 ± 16

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Summary

1、The process 𝜓′ → 𝑒+𝑒−𝜒𝑐0,1,2 is studied, there are clear 𝜒𝑐1 and 𝜒𝑐2signal and some 𝜒𝑐0 signal.

2、The most of events focus on the small angle between 𝑒+ and 𝑒−, and there are some events focus on the large angle between 𝑒+ and 𝑒−, these events can’t be understood.

3、The process 𝜒𝑐𝐽 → 𝑒+𝑒−𝐽/𝜓 also be observed.

Next to do1、Further analysis of the background

2、Study generator to get more accurate efficiency for data and give branching fraction

3、Study the process 𝜒𝑐𝐽 → 𝑒+𝑒−𝐽/𝜓 in detail

Thanks for your attention!

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BACK UP

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Some distributions for large angle between 𝑒+ and 𝑒−

𝑀(𝛾𝐽/𝜓) 𝜒2

𝑒+ track 𝜒2 𝑒− track 𝜒2

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Efficiency curve

26 Some events for large angle between 𝑒+ and 𝑒−

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Branching fraction

ℬ 𝜓′ → 𝑒+𝑒−𝜒𝑐0,1,2 =𝑁𝜒𝑐0,1,2

𝑁𝑡𝑜𝑡 ∙ ℬ(𝜒𝑐0,1,2 → 𝛾𝐽/𝜓) ∙ ℬ(𝐽/𝜓 → 𝑙+𝑙−) ∙ 𝜀0,1,2

ℬ 𝜓′ → 𝑒+𝑒−𝜒𝑐1 = (5.9 ± 0.2) × 10−4

ℬ 𝜓′ → 𝑒+𝑒−𝜒𝑐2 = (6.2 ± 0.5) × 10−4

1. 𝜀0 = 11.7%

2. 𝜀1 = 8.1%

3. 𝜀2 = 3.5%

ℬ 𝜓′ → 𝑒+𝑒−𝜒𝑐0 = (6.7 ± 1.3) × 10−4

Need further studyPHSP MC