Double-Tag Analysis of e DDindico.ihep.ac.cn/event/6114/session/8/contribution/32/...Motivation (±...

Double-Tag Analysis ofe+e−→ π+(DD∗)−

Andreas PitkaBESIII Physics & Software Workshop September 16

1 / 44PhysSoft Sept16

N

Overview

1 Basic Event Reconstruction

2 Overview of analysed Data Samples

3 Background

4 Fit Results√s = 4.23 GeV






N

Motivation

)2) (GeV/cJ/±π(maxM3.7 3.8 3.9 4.0

2Ev

ents

/ 0.

01 G

eV/c

0

20

40

60

80

100

)2) (GeV/cψ±(max

2Ev

ents

/ 0.

01 G

eV/c

)2±(max

2Ev

ents

/ 0.

01 G

eV/c

Data

Total fitBackground fit

PHSP MC

Sideband

)2) (GeV/c−*D0M(D3.9 3.95 4 4.05 4.1

)2Ev

ents/

(4.0

MeV

/c

0

20

40

60

)2) (GeV/c*0D−M(D3.9 3.95 4 4.05 4.1

)2Ev

ents/

(4.0

MeV

/c

0

20

40

60

)2) (GeV/c−*D0M(D3.9 3.95 4 4.05 4.1

)2Ev

ents/

(4.0

MeV

/c

0

10

20

30

)2) (GeV/c*0D−M(D3.9 3.95 4 4.05 4.1

)2Ev

ents/

(4.0

MeV

/c

0

10

20

30

40

Nature of Zc(3885)± still unknown.DD∗ molecule.Hadro charmonium.Tetraquark.DD∗ threshold effect.. . .

JP = 1+ is favored but needs confirmation.Perform full PWA at XYZ datasets to better understand nature of Zc and confirm quantumnumbers.


N

Basic Event Reconstruction


Event Topology

Simulation and Analysis withBOSS 6.6.5.p01

Use (D0, D̄0)− and (D0, D−)− Tags

red:Measurement via missing fourmomentum.

D0 Decay ChannelsD0 → K−π+ (Br = 3.88 %)

D0 → K−π+π0 (Br = 13.9 %)

D0 → K−2π+π− (Br = 8.08 %)

D0 → K−2π+π−π0 (Br = 4.2 %)∑Br i = 30.06 %

D+ Decay ChannelsD+ → K−2π+ (Br = 9.13 %)

D+ → K−2π+π0 (Br = 5.99 %)

D+ → KSπ+ (Br = 1.47 %)

D+ → KSπ+π0 (Br = 6.99 %)

D+ → KS2π+π− (Br = 3.12 %)

D+ → K−K+π+ (Br = 0.954 %)∑Br i = 27.65 %


N


Basic Event Selection

Good TracksCut on interaction region: Rxy < 1 cm, Rz < 10 cm.

Cut on direction: | cosϑ| < 0.93.

π± from KS DecaysCut on interaction region: Rxy < 2 cm, Rz < 20 cm.

Cut on direction: | cosϑ| < 0.93.

Good Photons0 < t < 14 · 50 ns.Endcap: Eγ > 50 MeV.

Barrel: Eγ > 25 MeV.

min. angle to next charged track: 20◦.Kinematic fitSelection of topology by best χ2.

χ2 < 50.

Cut on π0 mass112 MeV < mγγc

2 < 145 MeV.

Cut on KS mass487.8 MeV < mπ+π−c

2 < 507.7 MeV.

Cut to suppress D∗+D∗− Backgroundpπ± > 150 MeV/c.

PID Pions (dE/dx, ToF1 and ToF2)L(π) > L(K).

PID Kaons (dE/dx, ToF1 and ToF2)L(K) > L(π).


N

Overview of Analysed Data Samples

Overview of analysed Data Samples

Event yield and rough estimate of signal cross sections√s (MeV) 4230 4260 4360 4420 4600∫Ldt (pb−1) 1047.34± 0.03 825.67± 0.13 539.84± 0.10 1073.56± 0.14 566.93± 0.11

(1 + δr) · (1 + δv) 0.838 0.957 0.828 0.866 0.971

e+e− → π+D0D∗−

Nrec [data] 1114 447 1285 3545 1298ε (%) [sig. MC] 5.38± 0.04 5.62± 0.04 6.38± 0.04 6.50± 0.04 7.04± 0.04Nbg [inc. MC] 27± 5 30± 4 79± 6 188± 8 98± 12σBorn (pb) 265.7± 2.3 108.4± 1.4 488.1± 3.9 640.9± 4.4 357.3± 4.9

σold anaBorn (pb) 264± 5± 15 154± 5± 9 495± 10± 30 707± 9± 42 460± 13± 28

e+e− → π+D−D∗0

Nrec [data] 868 394 974 2985 1192ε (%) [sig. MC] 4.73± 0.04 5.04± 0.04 5.84± 0.04 6.05± 0.04 6.55± 0.04Nbg [inc. MC] 56± 6 35± 4 80± 6 200± 9 113± 12σBorn (pb) 181.5± 2.6 95.7± 1.5 313.9± 3.6 474.6± 4.1 321.8± 5.2

Estimate of Born cross section

σ =Nrec −NBg

Br · (1 + δr) · (1 + δv) ·∫Ldt · ε

Selected events for PWAMinimum:312 (

√s = 4.26 GeV, D∗+ → D0π+)

Maximum:2533 (

√s = 4.42 GeV, D∗+ → D0π+)


N


Event yield and rough estimate of signal cross sections

0

200

400

600

800

1000

4200 4250 4300 4350 4400 4450 4500 4550 4600 4650

σ(p

b)

√s (MeV)

e+e− → π+D0D∗− + ccBESIII Measurement e+e− → π+D0D∗− + cc

e+e− → π+D−D∗0 + cc

Good aggreement with old BESIII analysis.Cross section for channel with D∗0 shows similar shape as channel with D∗+.


N


Dalitz plots for different√s (all D∗ channels)

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4230 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4260 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4360 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4420 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4600 MeV

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

Available Phasespace grows with center of mass energy.8 / 44

PhysSoft Sept16N


Dalitz plots for different√s (all D∗ channels)

4.6

4.8

5

5.2

5.4

5.6

3.9 4.2 4.5 4.8 5.1

√s = 4230 MeV

4.64.8

55.25.45.65.8

4 4.4 4.8 5.2

√s = 4260 MeV

4.5

4.8

5.1

5.4

5.7

6

6.3

4 4.5 5 5.5

√s = 4360 MeV

4.54.85.15.45.7

66.36.6

4 4.5 5 5.5 6

√s = 4420 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4600 MeV

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)9 / 44

PhysSoft Sept16N

Background from Open Charm Reactions

Background

Contributing Background Channels (inc. MC)√s (MeV) 4230 4260 4360 4420 4600

σ (nb) 6.5 4.4 10.6 10.6 7.8∫Ldt (pb−1) 43 + 1011 515 + 291 523 42 + 993 506

N (inc. MC) 1.1 · 107 1.1 · 107 1.7 · 107 3.4 · 107 3 · 106Scaling Factor 1.6 3.1 3.1 3.1 0.78

Signalπ+D0D∗− 1452 2148 8396 20638 2373π+D−D∗0 1258 1871 6984 18192 1988

Backgroundπ+D∗0D∗− 5 29 122 311 28π0D0D̄∗0 19 31 85 253 32π0D∗+D− 4 14 47 180 32π0D∗0D∗0 0 0 2 6 1π0D∗+D∗− 0 1 5 24 6D0D̄∗0 36 51 54 122 16D∗+D− 17 17 24 55 8D∗0D̄∗0 20 12 51 102 12D∗+D∗− 6 13 31 62 6D0D̄0 0 1 1 4 0D+D− 1 0 2 6 0D+s D

−s 0 0 2 0 0

D∗+s D−s 13 5 18 41 1

D∗+s D∗−s 0 2 1 2 0

S/B 22± 2 22± 2 34± 2 33± 1 31± 3S/√S +B 50.9± 0.5 62.1± 0.5 122.3± 0.5 194.2± 0.5 65.0± 0.5

B/S (%) 4.5± 0.4 4.4± 0.3 2.9± 0.2 3.0± 0.1 3.3± 0.3

Studied backround contamination with the available inc. MC samples.For most reactions the cross section is not known.Big systematic uncertainty by assumed σ in EvtGen model (EvtOpenCharm).


N

Background

Contributing Background Channels (inc. MC)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

4.26 4.36 4.42 4.6

NB

g/N

S(1

0−

2)

√s (GeV)

π+D∗0D∗−

π0D0D̄∗0

π0D∗+D−

π0D∗0D∗0

π0D∗+D∗−

D0D̄∗0

D∗+D−

D∗0D̄∗0

D∗+D∗−

D0D̄0

D+D−

D+s D−s

D∗+s D−s

D∗+s D∗−s

No large variation of NBg/NS by√s.

The variation is dominated by the variation of the assumed σ in the EvtGen model.


N

Background

Distribution of Background in Dalitz plot (inc. MC)

4.6

4.8

5

5.2

5.4

5.6

3.9 4.2 4.5 4.8 5.1

√s = 4230 MeV

4.64.8

55.25.45.65.8

4 4.4 4.8 5.2

√s = 4260 MeV

4.5

4.8

5.1

5.4

5.7

6

6.3

4 4.5 5 5.5

√s = 4360 MeV

4.54.85.15.45.7

66.36.6

4 4.5 5 5.5 6

√s = 4420 MeV

4.85.25.6

66.46.87.27.6

4 4.8 5.6 6.4

√s = 4600 MeV

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

Events not scaled to data.Distributions relatively flat.


N

Background

Why Extraction of Background Distribution frommD Side-bands does not work

0

100

200

300

400

500

1.75 1.8 1.85 1.9 1.95 2 1.75 1.8 1.85 1.9 1.95 2

events

mD0 (GeV/c2)

Signal MCπ+D∗0D∗−

π0D0D̄∗0

π0D∗+D−

D0D̄∗0

D∗0D̄∗0

D∗+D∗−

D∗+D−

mD+ (GeV/c2)

Distributions for 106 events per channel.Background is peaking under signal region.Sidebands are not representative for open charm background distribution.Tried also sidebands in mD∗ , Emiss, pmiss, mmiss, ED − Ebeam and mbc.Plot for

√s = 4.42 GeV.


N

√s = 4.23GeV

Fit Results√s = 4.23 GeV

Dalitz Distribution at√s = 4.23GeV

4.6

4.8

5

5.2

5.4

5.6

4.6

4.8

5

5.2

5.4

5.6

0 20 40 60 80

0

10

20

30

40

50

60

70

4 4.4 4.8 15 15.5 16 16.50

10

20

30

40

50

60

70

m2(πD∗)(G

eV2/c4

)

m2(πD∗)(G

eV2/c4

)

eventsdatainc. MC Bg

events

m2(πD) (GeV2/c4)

events

m2(DD∗) (GeV2/c4)

Channel: D∗+ → D0π+811 events


N


Resonances at√s = 4.23GeV

4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4 4.5 5 4 4.5 5 4 4.5 5 4 4.5 5

m2(πD∗)(G

eV2/c4

)

Production: aLSDecay: bLS

a01

b00

a21

b00D∗0(2400)

a10

b11D(2550)

a01

b01

a01

b21

a21

b01

a21

b21D1(2420)

a01

b20

a21

b20

a22

b20

a23

b20

a43

b20

D2(2460)

→ πDa22

b21

D2(2460)

→ πD∗

m2(πD) (GeV2/c4)

a01

b01

a01

b21

a21

b01

a21

b21Zc

Partial waves for possible resonances.Added a small phasespace term to show suppression (resonance out of phasespace, angularmomentum barrier).


N


Fit with Zc and phasespace term: Dalitz

4 4.2 4.4 4.6 4.8 5

4.6

4.8

5

5.2

5.4

5.6

4 4.2 4.4 4.6 4.8 5

Data

4 4.2 4.4 4.6 4.8 5

Fit

−3−2.5−2−1.5−1−0.500.511.52

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 2 4 6 8 10

Fit Result at√s = 4.23 GeV

Resonance fit fraction (%) massMeV/c2 widthMeV

Z−c 48.6± 5.5 3895.0± 1.7 70.0± 6.9constant phasespace 51.4± 5.5 − −

Sum: 100.0± 7.4

Fit does not describe the structure at the border (bottom right) of the Dalitz plot.


N


Fit with Zc and phasespace term: m2ij

10

20

30

40

50

60

70

80

01020304050607080

−3−2−1

0123

02468

101214

4.2 4.5 4.8 4.8 5.1 5.4 15 15.5 16 16.5

events

DataFit

events

N−N

fit

√N

ε(%

)

m2πD (GeV2/c4) m2πD∗ (GeV

2/c4) m2DD∗ (GeV2/c4)

Enhancement in m2(πD) can not fully described by a kinematic reflection of Zc.


N


Fit with Zc and phasespace term: Helicity Angles

10

20

30

40

50

60

70

80

−3−2−1

0123

1

02468

101214

-1 -0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)

cos(θπR(πD)) cos(θπR(πD∗)) cos(θ

DR(DD∗))

Symmetric distribution in cos(θπRπD) could indicate dynamics in the πD system.To get a non flat distribution in cos(θπRπD): JRes ≥ 1.For a decay Res→ πD and J = 1 → Parity P = −1.No D∗∗ with JP = 1− in the mass region of interest!


N


Fit with D1(1−)+ and phasespace term: Dalitz

4 4.2 4.4 4.6 4.8 5

4.6

4.8

5

5.2

5.4

5.6

4 4.2 4.4 4.6 4.8 5

Data

4 4.2 4.4 4.6 4.8 5

Fit

−5−4−3−2−10

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 5 10 15 20 25



D1(1−)+ 27.8± 4.3 2223.4± 2.7 19.3± 5.4

constant phasespace 72.2± 5.4 − −

Sum: 100.0± 6.4

Fit with a (hypothetic) resonance D1(1−)→ π+D0.Let mass and width float: Startvalues m = 2430 MeV/c2, Γ = 25 MeV.


N


Fit with D1(1−)+ and phasespace term: m2ij

10

20

30

40

50

60

70

80

01020304050607080

−3−2−1

0123

02468

101214

4.2 4.5 4.8 4.8 5.1 5.4 15 15.5 16 16.5

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Good description of m2(πD) and m2(πD∗).Better description of m2(DD∗) might be gained by including D1(2420).


N


Fit with D1(1−)+ and phasespace term: Helicity Angles

10

20

30

40

50

60

−3−2−1

0123

1

02468

101214

-1 -0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Good description of angular distribution.


N

√s = 4.26GeV



4.64.85

5.25.45.65.8

4.64.855.25.45.65.8

0 10 20 30

0

5

10

15

20

25

30

35

3.9 4.2 4.5 4.8 5.1 15 15.5 16 16.5 17051015202530354045

m2(πD∗)(G

eV2/c4

)

m2(πD∗)(G

eV2/c4

)


events

m2(πD) (GeV2/c4)

events

m2(DD∗) (GeV2/c4)



N



4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4.85.25.6

4 4.5 5 4 4.5 5 4 4.5 5 4 4.5 5

m2(πD∗)(G

eV2/c4

)


a01

b00

a21

b00D∗0(2400)

a10

b11D(2550)

a01

b01

a01

b21

a21

b01

a21

b21D1(2420)

a01

b20

a21

b20

a22

b20

a23

b20

a43

b20

D2(2460)

→ πDa22

b21

D2(2460)

→ πD∗

m2(πD) (GeV2/c4)

a01

b01

a01

b21

a21

b01

a21

b21Zc



N


Fit with Zc and phasespace term: Dalitz

4 4.2 4.4 4.6 4.8 5 5.2

4.6

4.8

5

5.2

5.4

5.6

5.8

4 4.2 4.4 4.6 4.8 5 5.2

Data

4 4.2 4.4 4.6 4.8 5 5.2

Fit

−4

−3

−2

−1

0

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 2 4 6 8 10 12 14




Sum: 100.0± 7.9

Fit does not describe the structure at the border (bottom right) of the Dalitz plot.


N


Fit with Zc and phasespace term: m2ij

10

20

30

40

0

10

20

30

40

−3−2−1

0123

02468

101214

4.2 4.5 4.8 5.1 4.8 5.1 5.4 5.7 15 15.5 16 16.5 17

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Fitted width ΓZc = (27± 11) MeV.Much broader at

√s = 4.23 GeV: ΓZc = (70± 7) MeV.

Double-tag BESIII publication ΓZc = (31.5± 3.3) MeV.24 / 44

PhysSoft Sept16N


Fit with Zc and phasespace term: Helicity Angles

5

10

15

20

25

−3−2−1

0123

1

02468

101214

-0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Note: With only Zc the cos(θDRDD∗ ) distribution would be symmetric.

Compared to√s = 4.23 GeV: Less pronounced (cos2 +1) distribution in cos(θπRπD).


N


Fit with D1(1−)+ and phasespace term: Dalitz

3.9 4.2 4.5 4.8 5.1

4.6

4.8

5

5.2

5.4

5.6

5.8

3.9 4.2 4.5 4.8 5.1

Data

3.9 4.2 4.5 4.8 5.1

Fit

−6−5−4−3−2−10

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 2 4 6 8 10



D1(1−)+ 37.0 2241.3± 1.4 23.7± 6.2

constant phasespace 63.0 − −

Sum: 100

At√s = 4.26 GeV has moved into the available phasespace.

Does not describe data.26 / 44

PhysSoft Sept16N


Fit with D1(1−)+ and phasespace term: m2ij

10

20

30

40

0

10

20

30

40

−3−2−1

0123

02468

101214

4.2 4.5 4.8 5.1 4.8 5.1 5.4 5.7 15 15.5 16 16.5 17

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Very bad description in region of Zc.


N


Fit with D1(1−)+ and phasespace term: Helicity Angles

5

10

15

20

25

−3−2−1

0123

1

02468

101214

-0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Again: Good description of angular distribution.


N

√s = 4.36GeV



4.5

5

5.5

6

4.5

5

5.5

6

0 20 40 60 80 100

0

10

20

30

40

50

60

4 4.4 4.8 5.2 5.6 15.3 16.2 17.1 180

10

20

30

40

50

60

m2(πD∗)(G

eV2/c4

)

m2(πD∗)(G

eV2/c4

)


events

m2(πD) (GeV2/c4)

events

m2(DD∗) (GeV2/c4)



N



4.85.4

6

4.85.46

4.85.46

4.85.46

4.85.46

4.85.46

4.5 5.4 4.5 5.4 4.5 5.4 4.5 5.4

m2(πD∗)(G

eV2/c4

)


a01

b00

a21

b00D∗0(2400)

a10

b11D(2550)

a01

b01

a01

b21

a21

b01

a21

b21D1(2420)

a01

b20

a21

b20

a22

b20

a23

b20

a43

b20

D2(2460)

→ πDa22

b21

D2(2460)

→ πD∗

m2(πD) (GeV2/c4)

a01

b01

a01

b21

a21

b01

a21

b21Zc



N


Fit with Zc, D1(2420)0 and phasespace term: Dalitz

4 4.5 5 5.5

4.5

5

5.5

6

4 4.5 5 5.5

Data

4 4.5 5 5.5

Fit

−4

−3

−2

−1

0

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 4 8 12 16 20 24



D1(2420)0 31.8± 4.6 2423.0± 2.7 41.3± 6.4


Sum: 95.5± 6.5

Already an acceptable fit with Zc, D1(2420)0 and phasespace term.31 / 44

PhysSoft Sept16N


Fit with Zc, D1(2420)0 and phasespace term: m2ij

102030405060708090

100

0102030405060708090100

−3−2−1

0123

02468

101214

4.2 4.5 4.8 5.1 5.4 4.8 5.2 5.6 6 15.2 16 16.8 17.6

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Main features of the distribution are well described.Systematic underestimation of data for small m2(πD).


N


Fit with Zc, D1(2420)0 and phasespace term:Helicity Angles

10

20

30

40

50

60

−3−2−1

0123

1

02468

101214

-0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Main features of the distribution are described.Including D̄∗2(2460)

0 → D∗−π+ might yield a better description.33 / 44

PhysSoft Sept16N

√s = 4.42GeV



4.5

5

5.5

6

6.5

4.5

5

5.5

6

6.5

0 100 200 300

0

20

40

60

80

100

4 4.4 4.8 5.2 5.6 15 16 17 180

20

40

60

80

100

120

m2(πD∗)(G

eV2/c4

)

m2(πD∗)(G

eV2/c4

)


events

m2(πD) (GeV2/c4)

events

m2(DD∗) (GeV2/c4)



N



4.85.66.4

4.85.66.4

4.85.66.4

4.85.66.4

4.85.66.4

4.85.66.4

4 5 6 4 5 6 4 5 6 4 5 6

m2(πD∗)(G

eV2/c4

)


a01

b00

a21

b00D∗0(2400)

a10

b11D(2550)

a01

b01

a01

b21

a21

b01

a21

b21D1(2420)

a01

b20

a21

b20

a22

b20

a23

b20

a43

b20

D2(2460)

→ πDa22

b21

D2(2460)

→ πD∗

m2(πD) (GeV2/c4)

a01

b01

a01

b21

a21

b01

a21

b21Zc



N


Fit with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ andphasespace term: Dalitz

4 4.5 5 5.5 6

4.5

5

5.5

6

6.5

4 4.5 5 5.5 6

Data

4 4.5 5 5.5 6

Fit

−6−5−4−3−2−10

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 5 10 15 20 25 30 35



D1(2420)0 42.9± 3.0 2447.8± 2.2 63.4± 1.2

D̄∗2(2460)0 → D∗−π+ 18.1± 2.4 2537.8± 6.0 54.5± 8.6

D∗2(2460)+ → D0π+ 5.0± 1.1 2401.7± 4.3 15.5± 3.5


Sum: 98.1± 4.3

Structure in lower half of Dalitz plot is most probable caused by background.Significant discrepancy to known D∗∗ masses.


N


Fit with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ andphasespace term: m2ij

20406080

100120140160180200220

020406080100120140160180200220

−3−2−1

0123

02468

101214

4 4.4 4.8 5.2 5.6 4.8 5.2 5.6 6 6.4 15.2 16 16.8 17.6 18.4

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Main features of the distribution are described by the fit.Significant discrepancy to known D∗∗ masses.Most probable caused by incomplete ampltiude model (possible contribution fromD∗0(2400)

+, D(2550)0).37 / 44

PhysSoft Sept16N


Fit with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ andphasespace term: Helicity Angles

20

40

60

80

100

120

−3−2−1

0123

1

02468

101214

-1 -0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Main features of the distribution are described by the fit.Systematic discrepancies might indicate the used model is too simple.

38 / 44PhysSoft Sept16N

√s = 4.6GeV



4.5

5

5.5

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6.5

7

7.5

4.5

5

5.5

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6.5

7

7.5

0 10 20 30 40 50

010203040506070

4.2 4.8 5.4 6 6.6 15 16 17 18 19 200510152025303540

m2(πD∗)(G

eV2/c4

)

m2(πD∗)(G

eV2/c4

)


events

m2(πD) (GeV2/c4)

events

m2(DD∗) (GeV2/c4)



N



5678

5678

5678

5678

5678

5678

4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7

m2(πD∗)(G

eV2/c4

)


a01

b00

a21

b00D∗0(2400)

a10

b11D(2550)

a01

b01

a01

b21

a21

b01

a21

b21D1(2420)

a01

b20

a21

b20

a22

b20

a23

b20

a43

b20

D2(2460)

→ πDa22

b21

D2(2460)

→ πD∗

m2(πD) (GeV2/c4)

a01

b01

a01

b21

a21

b01

a21

b21Zc



N


Fit with D∗1(2420)0, D∗2(2460)

0, D∗2(2460)+ and phases-

pace term: Dalitz

4 4.5 5 5.5 6 6.5

4.5

5

5.5

6

6.5

7

7.5

4 4.5 5 5.5 6 6.5

Data

4 4.5 5 5.5 6 6.5

Fit

−5−4−3−2−10

1

2

3

(N−N

fit)/√N

Residuals

m2(πD∗)(G

eV2/c4

)

m2(πD) (GeV2/c4)

0 2 4 6 8 10 12 14 16 18



D1(2420)0 8.7± 1.8 2425.9± 2.3 20.1± 5.6

D̄∗2(2460)0 → D∗−π+ 6.9± 1.7 2473.6± 3.9 24.4± 7.7

D∗2(2460)+ → D0π+ 37.1± 3.0 2470.9± 1.7 39.3± 4.4


Sum: 99.1± 5.0

Acceptable description of data with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ and phasespaceterm.


N


Fit with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ and phases-pace term: m2ij

102030405060708090

100110120

0

10

20

30

40

50

60

70

−3−2−1

0123

02468

101214

4 4.5 5 5.5 6 6.5 5 5.5 6 6.5 7 15 16 17 18 19

events

DataFit

events

N−N

fit

√N

ε(%

)


2/c4) m2DD∗ (GeV2/c4)

Biggest deviation between data and fit in m2(DD∗).Masses of D∗∗ are estimated in the fit with to high values (O(10 MeV)).


N


Fit with D1(2420)0, D∗2(2460)0, D∗2(2460)

+ and phases-pace term: Helicity Angles

10

20

30

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50

60

−3−2−1

0123

1

02468

101214

-1 -0.5 0 0.5 -0.5 0 0.5 1-0.5 0 0.5

events

DataFit

N−N

fit

√N

ε(%

)


DR(DD∗))

Improvent of logL for fit with Zc not very significant: 2.1σ (by likelihood ratio test).


N


Summary

What has been doneFirst PWA fits performed at

√s = 4.23, 4.26, 4.36, 4.42, 4.6 GeV.

ResultsMain features of the data can be described with D1(2420)0, D∗2(2460)

0 andD∗2(2460)

+.

Strong Zc signal at√s = 4.36 GeV.

Simple Breit-Wigner-Amplitude hypothesis of Zc with JP = 1+ fails to describe dataat√s = 4.23, 4.26 GeV.

What’s in progressOptimize cuts for each

√s.

Not only use D∗+ → D0π+ but also D∗+ → D+π0, D∗0 → D0π0 and D∗0 → D0γ.Compare different quantum numbers for Zc.

Allow in the fit a coupling of Zc to J/ψπ (Flatte, K-Matrix).

Check by MC if shift of D∗∗ resonances in mass is systematic.

Find a way to extract background shape from data.44 / 44

PhysSoft Sept16N

Basic Event ReconstructionOverview of analysed Data SamplesBackgroundFit Results s=4.23GeVFit Results s=4.26GeVFit Results s=4.36GeVFit Results s=4.42GeVFit Results s=4.6GeV

Double-Tag Analysis of e DDindico.ihep.ac.cn/event/6114/session/8/contribution/32/...Motivation (±...

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