1. Yaxing Tan (BESIII-USTC Group)
Study of e+ e- → ϕ(1020)π+ π-
Yaxing Tan
(BESIII-USTC Group)

2. Introduction (Cross section Line shape)
Cross section line shape of e+ e- → ϕ(1020) π+ π-.
Property of Y(2175) → ϕ(1020) f0(980)(π+ π-).
PHYSICAL REVIEW D80, (R) (2009)
PHYSICAL REVIEW D86, (2012)
Belle
BABAR
(a)
(b)
(c)
(d)
M1 = 2.079±0.013GeV
Γ1= 0.192±0.023GeV
M2 = 2.180±0.011GeV
Γ2 = 0.077±0.018GeV
Large error around 2.1GeV:
15%~30%.
With R-scan data sets: improve precision (<5~10%).
Parameters of Y(2175):
Large difference between two results.

3. Data sets and MC simulation
1.BOSS665p01. 2.R-scan data sets:（in 2015） 3.100K Signal MC at each energy poing. e+ e-→ϕ π+π-
3.08
2.8
1.008
2.3864
22.549
2.125
108.49
3.02
17.29
2.7
1.034
2.3094
21.089
2.1
12.167 3
15.881
2.6464
33.722
2.2324
11.856
2.05
3.343
2.981
16.071
2.6444
34.003
2.2
13.699 2
10.074
2.95
15.942
2.5
1.098
2.175
10.625
2.9
2.396
66.869
2.15
2.841

4. Event selection Good Charged Track: PID: Vertex fit (K+K-π+π-).
|Vz| < 10.0 && |Vr|< 1.0 && |cosθ|<0.93;
NGood = 4 && NCharge=0;
PID:
N(π+)=N(π-) = 1; prob_π >prob_K && prob_π >prob_p;
N(K+)=N(K-) = 1; prob_K>prob_p && prob_K>prob_π;
Vertex fit (K+K-π+π-).
4C kinematic fit (K+K-π+π-).
χ24C(K+K- π+π+) < 50;

5. @2125MeV：L=108.49pb-1 (1) X24C(K+K-π+ π- )<50;
(2) ϕ(1020) Fitting :
Signal: MC shape Convoluted Gaussian function
Background: Argus function
NSignal=3419.0±82.0;

6. ϕ(1020) Fitting

7. ϕ(1020) Fitting

8. ϕ(1020) Fitting

9. Cross section: σ(e+e-→ ϕ(1020) π+π-)
Lum.(pb-1) 2
10.074
198.0±24.8
1.0067
17.921
48.9
223.0±27.9
2.05
3.343
85.3±17.3
1.0587
18.463
266.4±54.0
2.1
12.167
381.2±28.3
1.0004
20.315
315.5±23.4
2.125
108.49
3419.0±82.0
1.0046
18.483
346.8±8.3
2.15
2.841
85.3±12.4
1.0568
18.192
320±46.4
2.175
10.625
273.9±23.0
1.0013
22.21
237.2±19.9
2.2
13.699
282.7±22.6
1.1638
19.968
181.3±14.5
2.2324
11.856
176.6±17.5
1.259
18.876
128±12.7
2.3094
21.089
350.8±24.7
1.2477
18.513
147.4±10.4
2.3864
22.549
420.9±26.3
1.122
19.345
176.3±11
2.396
66.869
1351.5±47.1
1.1338
22.681
160.6±5.6
2.4 -
1.1381
23.734
2.5
1.098
12.7±4.5
1.2613
21.812
86±30.5
2.6444
34.003
372.4±24.1
1.236
22.993
79.4±5.1
2.6464
33.722
288.9±22.7
1.2456
22.703
61.4±4.8
2.7
1.034
16.9±5.2
1.6953
17.111
115.3±35.5
2.8
1.008
10.0±3.7
1.4964
19.848
68.5±25.3
2.9
533.2±29.4
1.3625
21.873
34.7±1.9
2.95
15.942
83.1±11.0
1.2314
22.784
38±5
2.981
16.071
68.0±10.6
1.6956
17.204
29.7±4.6 3
15.881
54.0±9.7
1.6885
17.119
24.1±4.3
3.02
17.29
53.5±9.4
1.7004
16.658
22.4±3.9
3.08
482.7±26.7
1.7368
15.212
29.6±1.6

10. Possible intermediate states (R-scan data sets in 2015) @2125MeV

11. @2125MeV: L=108.49pb-1 (e+e-→ ϕ(1020) π+π- )
ϕ(1020) Signal Region

12. @2125MeV: L=108.49pb-1 (e+e-→ K*(892)0K- π+ +c.c. )

13. Thank you

14. Numbers of NGoodCharge