Outline Introduction to BEPCII and BESIII Motivation K

Outline • Introduction to BEPCII and BESIII • Motivation • ψ’ γη’ K+ K 1. The branching fraction of χc. J η’K+K 2. PWA of χc 1 η’K+K • J/ψ γη’ K+ K 1. The branching fraction of J/ ψ γη’K+K 2. PWA of ηc η’K+K • Summary 2

Dataset • Data Samples: ü Bes. II: 58 M J/ψ, 14 M ψ(2 S) ü Bes. III round one: 225 M J/ψ, 106 M ψ(2 S) The result in this talk are mainly based on the two data samples. ü Bes. III round two: 1 billion J/ψ, 0. 4 billion ψ(2 S) 5

Motivation u. History: Similar process，J/ψ γη’π+π- has been studied at BESII. BES Ⅲ BES Ⅱ X(1835) X(2120) X(2370) γη’K+K- has never been studied。The η’K+K- mass threshold is 1. 95 Ge. V, some higher resonance may be observed. 6

Motivation u. Measure the decay χc. J : color-octet mechanism(COM) Color singlet χc 0, χc 2 (cc) (gg) Color singlet χc 1 (cc) (gqq) Color octet (ccg) (gqq) 7

Motivation u. Search for exotic states: glueball, hybrid… Ø The QCD allow the existence of glueballs. The glueball mass spectrum predicted by LQCD. PRD 60, 034509 (1999) 8

Motivation Ø The abundance of scalar mesons: We observed much more scalar than theoretical predicted. Some of them may be exotic states. Experimental light flavoured meson spectrum. Phys. Rept. 454, 2007 Ø Radiative ψ decay is glueball rich process. 9

motivation u. Glueball is flavor blindness. u. Most of the glueball is expected to mix with nearby mesons. χc 1 PS is sensitive to the glueball-qq mixing scheme 10

Motivation Q. Wang, G. Li, Q. Zhao, Int. J. Mod. Phys. A 27, 1250135 (2012) Scheme 1 Scheme 2 K*0(1430) η’K hasn’t been observed by now. χc 1 η’KK and ηc η’KK might be the most suitable channel to observe K*0(1430) η’K. 11

Selection criteria for (ψ’ γη’ K+ K-, η’ γρ0, ρ0 π+π-) • Ngood=4, Q=0 Vr<1 cm, |Vz|<10 cm |cosθ|<=0. 93 l l Ngamma>=2 Eγ>=25 Me. V, For Barrel Eγ>=50 Me. V, For Endcap angleγ-ch>=50 0<=TDC time<=14 PID for K: prob(K)>prob(π) &&prob(K)>prob(p) NK+=NK-=1 • Select 2 gamma χ4 c 2(γγππKK)<40 select 1 gamma of η’ Minimize |m(γππ)-m(η’)| 0 l veto π |m(γγ)-m(π0)|>=15 Me. V l Veto J/psi |m(γγ)recoil-m(J/ψ)|>22 Me. V |m(ππ)recoil-m(J/ψ)|>8 Me. V l Mass windows cut |m(γππ)-m(η’)|<15 Me. V 12

Several invariant mass spectrum ρ0 η’ ηc, χc. J 13

Selection criteria for (ψ’ γη’ k+ k-, η’ ηπ+π-, η γγ) • Ngood=4, Q=0 Vr<1 cm, |Vz|<10 cm |cosθ|<=0. 93 l l Ngamma>=3 Eγ>=25 Me. V, For Barrel Eγ>=50 Me. V, For Endcap angleγ-ch>=50 0<=TDC time<=14 PID for K: prob(k)>prob(π) &&prob(k)>prob(p) Nk+=Nk-=1 • Select 3 gamma χ2(γγγππk k)<50 select 2 gamma of η Minimize |m(γγ)-m(η)| l veto π0 any combination of two γ |m(γγ)-m(π0)|>20 Me. V l Mass windows cut |m(γγ)-m(η)|<25 Me. V |m(ηππ)-m(η’)|<25 Me. V 14

Several invariant mass spectrum η η’ ηc, χc. J 15

The peaking background η’ γρ0 mode η’ ηππ mode χc. J η’ There are clear χc. J band out of η’ range. There are peaking background within η’ range. 16

The main background For η’ γρ0 mode: The main background is Øχc. J K+K-π+π- : peak higher Øχc. J K+K-π+π-π0: peak lower A gauss function is used to represent the overlap of this two kinds of background. For η’ ηππ mode: The main background is χc. J ηπ+π-K+K- 17

Simultaneous fit for η’ signal events and sideband events η’ γρ0 mode Signal range Sideband Ø The signal PDF: MC shape gauss. Ø Use the shape and event number of peaking background in sideband to constrain the peaking background in η’ signal range. η’ ηππ 18

DIY MC to get the selection efficiency with PWA result DIY MC: 用分波�出的截面��重� PHSP事例�行舍�法抽� The comparison between data and DIY MC. The red dot is real data. The black histogram is the MC. 数据与MC的不��量�和角分布都符合的很好 19

The systematic uncertainties 20

The combination of the measured result from two η’ mode The measured branching fraction from two measurements We use the weighted χ2 method to combine the result. And take the relation of uncertainties between two mode into consideration. σi 是两次�量各自独立的�差， εf 是两次�量相同的�差 21

The combination of the measured result from two η’ mode The formula for the combination of two measurement. The combined result 22

The line-shape of states • All the line-shape of the states involved in the analysis are fixed in the fit. • f 0(980), flatte formula, M=0. 965 Ge. V, g 1=0. 165 Ge. V, g 2/g 1=4. 21(BES 2’s result) • K*0(1430), flatte formula, cleo’s measurement • All other states are fixed to PDG value with constant width Breit-Wigner. 25

The projection result of PWA f 0(1710) f 2(1525) f 0(980) η’ γρ0 mode K*0(1430) η’ ηππ mode Only four states are included in nominal fit. 26

The angular distribution comparison The χ2 check for the projection result. 27

The dalitz plot η’ γρ0 mode fit η’ ηππ mode fit data 28

The systematic uncertainty of PWA The banching fraction result with systematic uncertainty 30

Selection criteria for (J/ψ γη’ k+ k-, η’ γρ0, ρ0 π+π-) • Ngood=4, Q=0 Vr<2 cm, |Vz|<20 cm |cosθ|<=0. 93 l l Ngamma>=2 Eγ>=40 Mev angleγ-ch>=50 0<=TDC time<=14 PID for π: prob(π)>prob(K) &&prob(π)>prob(P) for K: prob(K)>prob(π) &&prob(K)>prob(P) Nk+=Nk-=1 • Select 2 gamma χ4 c 2(γγππKK)<40 select 1 gamma of η’ Minimize |m(γππ)-m(η’)| 0 l veto π |m(γγ)-m(π0)|>=20 Me. V l veto η |m(γγ)-m(η)|>=15 Me. V l Mass windows cut 0. 55<m(ππ)<0. 9 Ge. V |m(γππ)-m(η’)|<15 Me. V Optimized with the largest S/√(S+B) 31

Selection criteria for (J/ψ γη’ k+ k-, η’ ηπ+π-, η γγ) • Ngood=4, Q=0 Vr<2 cm, |Vz|<20 cm |cosθ|<=0. 93 l l Ngamma>=3 Eγ>=40 Mev angleγ-ch>=50 0<=TDC time<=14 PID for π: prob(π)>prob(K) &&prob(π)>prob(P) for K: prob(K)>prob(π) &&prob(K)>prob(P) Nk+=Nk-=1 • Select 3 gamma χ2(γγγππK K)<40 select 2 gamma of η Minimize |m(γγ)-m(η)| 0 l veto π any combination of two γ |m(γγ)-m(π0)|>10 Me. V l Mass windows cut |m(γγ)-m(η)|<25 Me. V |m(ηππ)-m(η’)|<25 Me. V Optimized with the largest S/√(S+B) 32

The fit of η’ peak η’ ηππ mode η’ γρ0 mode Blue line: fit result, the signal is represented by Double Gaussian function Red line: background of J/ψ η’K+K- (Br(J/ψ η’K+K- ) is measured simply) blackline: background of J/ψ π0η’K+K(Br(J/ψ π0η’K+K- ) is measured simply) Combined result: Br(J/ψ γη’K+K- )=(3. 65± 0. 35 ) × 10 -4 33

The m(η’K+K-) spectrum The black dot is real data. The red histogram is the PHSP shape from MC. There is no clear structure at the lower mass range. 34

The fit of ηc • Method 1： the fit is not so good. • Method 2: The mass and width of ηc is fixed to cleo’s measurement. M=2. 9822 Ge. V, Γ=31. 5 Me. V. 35

The fit of ηc • Method 3: consider the interference between ηc and non- ηc process. The phase angle The blue line is global fit result. The red line is signal. The green line is the interference 36

The branching fraction of ηc We use method 2 to give the preliminary result η’ γρ0 mode η’ ηππ mode Combined result 37

PWA for ηc η’K+K • 2 D plot M(η’K+K- ) vs. M(K+K- ) M(η’K+K- ) vs. M(η’K) The distribution is trival out of ηc range, we only perform PWA within ηc range. The method is very like χc 1 η’K+K-. 根据角�量以及宇称守恒. M(KK)�上可能的 � : f 0(0++), f 2(2++) M(η’K)�上可能的 � : K*0(0+), K*0(1 -), K*0(2+) 38

The PWA projection result f 0(1710) Black dot is realdata. f 0(980) Red histogram is fit result. K*0(1555) Dalitz plot f 0(1710) f 0(980) fit K*0(1555) data The projection of individual state. 39

The problems • The pole position of K*(1555) is much higher than PDG’s K*(1430). PDG value of K*(1430): M=1. 425 Ge. V, Γ=0. 27 Ge. V • The ηc line shape is greatly influenced by the barrier factor , R is the radius of the centrifugal barrier. R=1 fm R=0. 1 fm 40

PWA result with systematic uncertainty The parameters of resonance with systematic uncertainty The non-pwa part of systematic uncertainty The branching fraction with systematic uncertainty 41

Summary • We measured the branching fraction of χc. J η’K+K- for the first time with η’ γρ0 and η’ ηππ mode. • We performed the PWA for χc 1 η’K+K- , the intermediate process χc 1 η’f 0(980), χc 1 η’f 0(1710), χc 1 η’f 2(1525)， χc 1 K*0(1430)K is observed. K*0(1430) η’K is observed for the first time. • A preliminary result of J/ψ γη’K+K- is also given. The branching fraction of J/ψ γη’K+K- and ηc η’K+K- are measured. • PWA for ηc η’K+K- are performed. ηc η’f 0(980), ηc η’f 0(1710), ηc K*0(x)K. 42

Other works • Other works during the period for Ph. D degree. ü The partial wave analysis for Y(4260) D*Dπ. ü The partial wave analysis for Y π0π0 J/ψ to determine the JPC of Zc(3900) ü The TOF electronic on-call. 43