recent besii results of charmonium decays gang li ccast&ihep, beijing for Ψ(2s) group topical...
DESCRIPTION
Introduction P-wave charmonium decays c0, c1, c2 3M 14M 6.42 pb -1 data at Ecm=3.65 GeV for continuum study. 4M 2001.Nov.01to 2002.Mar.02TRANSCRIPT
Recent BESII Results of Charmonium DecaysGang LIGang LI
CCAST&IHEP, BeijingCCAST&IHEP, Beijing
for Ψ(2S) GroupTopical Seminar on Frontier of Particle Physics
2005: Heavy Flavor Physics August 13- 17, 2005
Outline
Introduction cJ Study ’ Decay to Multihadrons Summary
0
2
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10
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14
MKI MKII MKIII CBAL BESI BESII CLEOc
Introduction
P-wave charmonium decays c0 , c1 , c2
3M
14M
6.42 pb-1 data at Ecm=3.65 GeV for continuum study.
4M
2001.Nov.01to 2002.Mar.02
cJ Study --- Motivation 1. Compared with J/, relative little is known about P-wave triplet cJ(J=0,1,2) decays, more data on exclusive decays of them are important for understanding of the nature of cJ.2. The decays of cJ , in particular c0 and c2 , provide a direct window on glueball dynamics in 0++ and 2++, as the cJ hadronic decays may proceed via ccbar gg qqbar qqbar 3. PWA is an excellent tool to investigate the intermediate resonant decay account for the interferences when calculating Brs.
Partial Wave Analysis of c0 K K
cJ Study (I)
1. Qi = 0 ; 2. p()+p( ) > 650 MeV [BG:’ J/ ]; 3. Prob( K K )> Prob(
)& Prob( K K )> Prob(
K K K K );4. M( ) [497±50] MeV/c2
& second vertex <5mm
[BG: KS ];
Event
level
c0 K K
Avoid introducing a huge number of partial waves and also limited by statistics; our study is devoted to c0 K K
1371 eventsc0
c1(3511.3±1.3MeV)
c0(3414.7±0.6MeV)
c2(3556.4±0.9MeV)
5C-
fitdot with
error bar :data
In our final fit, all thesepartial waves have beenincluded, together withtheir interferences.For convenience of narration, we are todescribe following decay modes one by one:
1. ( )( K K )2. (K )(K )3. (K ) K
1371 events
( )( K K )f0(1710)
f0(2200)
f0(980)
f0(1370)
(770)
S:change in log likelihood
S.Flatte, Phys. Lett. B 63(1976)224; B.S.Zou &D.V.Bugg, Phys. Rev. D48(1993)R3948Flatte formula :
)( 22112980
1 ggMisM
f
i (s)=sqrt(1-4m2i/s) : phase space factor for &K K ;
g i : squares of coupling constants to &K K ;[B.S.Zou &D.V.Bugg, Phys. Rev. D48(1993)R3948]:M=0.9535; g1=0.1108 GeV; g2=0.4229 GeV;
For , formula once used by BES in analysis of J/ [ PLB598(2004)149-158]
MisMRBW 2
1Other resonances
Breit-Wigner formula :
( )( K K )
Positive values indicate poorer fits
Bad fit without scalar indicates that a scalar f0(2200) decays to K K is needed around 2.2 GeV .
( )( K K )
( )( K K ) ResultsBES II PDG2004
resonance Mass (M) and Width () [unit:MeV]
resonance Mass (M) and Width () [unit:MeV]
f0(1370) M:1265±30(+20–35) f0(1370) M:1200~1500
: 350±100(+105–60) : 200 ~500 f0(1710) M:1760±15(+15–10) f0(1710) M:1714±5
: 125±25(+10–15) : 140±10 f0(2200) M:2170±20(+15–10)
: 220±60(+10–15)
Significance : 5. 3
Significance : 7. 1
Significance : 6. 5
(K )(K )1371 events
MisMRBW 2
1BW formula:
with:3
022
20
20
0 11
pp
prpr
mm
m: mass of K system; m0 : mass of resonance; 0 resonance width; p: momentum of K in K system; p0: p evaluated at resonance mass; r=3.4: Interaction radius[D.Aston et al., NPB296(1988)493]
K*0(1430)
K*0(1950)
K*(892)0
Results
BES II PDG2004resonance Mass (M) and Width
() [unit:MeV]resonance Mass (M) and Width ()
[unit:MeV]K*0(1430) M:1455 ± 20 (+15–15) K*0(1430) M:1412 ± 6
: 270 ± 45 (+30–35) : 294 ± 23 K*0(1950) M:1945 ± 30 K*0(1950) M:1945 ± 10 ± 20
: ~500 : 201 ± 34 ± 79 #: 201 (fix to PDG in fit)
Significance : 7. 1
Significance : 7. 2
Significance : 8. 7
(K )(K )
(K )K
1371 events
M(K ) [896±60]
M( ) [700,800]
K1(1270)
K1(1270)
K1(1400)
K1 (1279): S-wave BW
K1(1400): S-wave BW
90% C.L.
K1(1270)
Strange axial meson mixing(K )K
K1(1270) =KA sinK + KB cos K ,K1(1400) = KA cos K – KB sin K ,
KA = K1(1270) sin K + K1(1400) cos K ,KB = K1(1270) cos K – K1(1400) sin K ,
Here is an interesting problem involving K1(1270), K1(1400), that is the mixing of the two strange axial mesons
In the quark model , there are two ground-state axial vector nonets, one is (3P1) state (KA) , the other is (1P1) state (KB). For a strange quark mass is greater than those of up and down quarks, so SU(3) is broken
which lead to mixing of KA and KB states to give a physical K1 state: viz.
or
In SU(3) limit, only KA couples to the weak current, and the degenerated twooctets before mixing lead to mixing angle ( K )equal to 45° which means that
there should be equal amount of K1(1270) and K1(1400).
Flavor-SU(3)-violating of K1(1270) -K1(1400) asymmetry is observed.
However, our PWA yields :K1(1270)K [Br:(42±6)%] signal of 68.3±11.0 events;K1(1400)K* [Br:(94±6)%] signal of 19.7±6.9 events;
Strange axial meson mixing(K )KAnother interesting problem here is about the mixing angle K. According to
present BES results, the mixing angle K >57º for c0
More interesting fact is from decay. By virtue of K1 measurement together with relativized quark model estimation, the mixing angle should be within a range:–35º< K <45º at 68% C.L. [H.G.Blundell et al. ,PRD53,3712(1996)]
But according to previous BES results, K <29º for [PRL83,1918(1999)]
K >48º for J/ [PRL83,1918(1999)]
All discrepancies displayed here indicate that more further theoretical and experimental works are needed.
Summary of PWA of c0 K K
Events: (1371-29) ; efficiency: (5.85 ± 0.01)%
CLEO:PRD70,112002(2004)
B(K*(892)K )=100%
=
BES:PRD70,09002(2004)
B(’ c0 f0(980) f0(980) )=(6.5 ± 1.6 ± 1.3) 10 –5
B(’ c0)=(9.22 ± 0.11 ± 0.46) 10 –3
Summary of PWA of c0 K K (con’t)
From these c0 K K fit results, it is found that scalar resonances have larger decay fractions compared to those of tensors, and such decays provide a relatively clean laboratory to study the properties of scalars, i.e. f0(980),f0(1370),f0(1710),f0(2200), K*0(1430), and so forth.
B(’ c0)=(9.22 ± 0.11 ± 0.46) 10 –3CLEO:PRD70,112002(2004)
First evidence of c0, c2
cJ Study (II)
•Kinematic fit6-C fit is required, the additional 2-C is that two pair photons all satisfy M
=M0, Furthermore, 2(6C)<12 •Prob(6C)> Prob(7C) is added if N>5 so that the background from the potential 0,2 +00 can be suppressed.
Removing the recoil J/ events by minimizing |M+-(recoil)-MJ/|, the recoiling mass of the candidate pion pair can’t fall into J/ peak region(3.08-3.12GeV).
Event selectionEvent selection
Some distributions in 0,2 from data
Sideband region: 200 MeV wide aroun
d peak
Event levelEvent level
Signal region
c0c2
0 +0+054(=1.66%)MC simulationMC simulation
c0
Fit mass spectrum
No obvious signal is found in sideband.
M(c0)=3420.1±9.0MeVM(c2)=3553.3±11.9MeV
(BW fit ;width fixed)
c0
c2
Backgroundsideband
N(c0)= 38.19.9Sif. 4.4
N(c2)= 27.77.4Sif. 4.7
(Mass & width fixed)
dot with error
bar :data
The signal is described by BW convoluted with double-Gaussian obtained from MC simulations and background shape is determined by sideband shape.
Summary of c0, c2 decay
)()()( 02BBN
NBcJ
obscJ
• We first observed 0,2 decay and measure their branching ratios. • We did not see obvious evidence below 3.2 GeV energy region.
’ decay to Multihadrons
’ 3(+-)
’ +-0K+K-
Strong decay of ’ 3(+-) suppressed due to G-parity violation.
e+e- 3(+-) EM process (continuum contribution) will be estimated by off-resonance data @3.65 GeV.
X-sections @3.65 & 3.686 GeV give the EM form factor for 3(+-) state.
BR of J/ 2(+-) determined via ’ +-J/ , J/ 2(+-).
’ 3(+-)
’ 3(+-)
ψ’ π+π-J/ ψ, J/ψ 2(π+π-) bkgd removed by requiring
3.06< <3.14 GeV
MππrecM
recM
4C fit for ψ’ π+π- π+π- π+π-
ψ’ KsKs π+π- bkgd removed by requiring 2 π+π- pairs satisfyi
ng 0.47<M ππ<0.53 GeV
PRD71(2005)072006
Ks bkgdJ/ bkgd
’ 3(+-)
ψ’ 3(π+π-) @3.686 GeV
Histogram = signal [email protected] GeV + continu
um @3.65 GeV
Hatched histogram = e+
e-3(π+π-) [email protected] GeV
4C fit for π+π- π+π- π+π- final state
e+e-3(π+π-) @3.65 GeV
Histogram = MC simulation
BR of J/ 2(+-)Systematic error reduced by
comparing 2 processes:
Difference between MC & DTdue to the simulation of error matrix in
track fitting.Taken into account in systematic error.
Confidence level distribution for kinematic fitting of
+- J/ , 2(+-)
recM
’ 3(+-) RESULTS ’ 3(+, - ), J/ 2(+, - ) BRs measured with improved accuracies. B[’ 3 (+, -)]= (5.450.42 0.87) x 10 –4
greater than Mark I result (1.51.0) x 10 –4 {PRD17(1978)1731} B[J/ 2(+, -)]= (3.530.12 0.29) x 10 –3
consistent with Mark I result (4.01.0) x 10 –3 {PRL 36(1976291} and BaBar result (3.610.26 0.26) x 10 –3 { hep-ex/0502025 } • pQCD 12% rule tested. Q[3(+, -) ]= (148)% Q[2(+, -) ]= (133)% • Form factors for e+e- 3(+, - ) at Ecm=3.65, 3.686 GeV determined F3.65 [3(+, -) ] = 0.190.02 F3.686 [3(+, -) ] = 0.240.02
’+-0K+K-
• PID for π and K• 4C kinematic fit for ’+-γγK+K-
• | -3.096 | >0.05 GeV/c to reject ’+- J/• removed by identifying Ks+-
• Fit M(γγ) to obtain ’+-0K+K- evts.
0 KK s
recM
Mγγ @ Ecm=3.686 GeV Mγγ @ Ecm=3.65 GeV
0: 69841 evts. 0: 357 evtsPreliminary
’ωK+K-
• | Mγγ – 0.135 | <0.03 GeV/c2 to select ’+ - 0K+K- evts. ’ωK+K- evts are obtained by fitting M(+ - 0).
M(+-0) @ Ecm=3.686 GeV M (+-0) @ Ecm=3.65 GeV
Preliminary
ω: 7811 evts. ω: [email protected]% C.L.3.100
’ωf0(1710)
Dalitz plot
for ’ωK+K- candidates
M(K+K-) for ’ωK+K- candidates
Preliminary
’ ωf0(1710)
18.9 6.2 evts.
’+-0K+K-
Preliminary resultsChannel BΨ’ h(10-4) BJ/Ψ h(10-4) Qh(%)
K + K - π + π -π0
12.4 1.8 120 28 10.3 2.9
ωK + K - 2.38 0.47 16.8 2.1 14.2 3.4
ω f0(1710) ωK + K -
0.59 0.22 6.6 1.3 8.9 3.8
The PWA on c0 K K in ’ c0 decay is preformed. We fit the significant contributions from f0(980) f0(980) , f0(980) f0(2200) , f0(1370) f0(1710) , K* (892) 0 K* (892) 0 , K*
0 (14
30) K* 0
(1430) , K* 0
(1430) K* 2(1430) +c.c.
Flavor-SU(3)-violating of K1 (1270)-K1(1400) asymmetry is obs
erved and the mixing angle between two strange axial mesons is determined to be greater than 57 degree.
First observed c0, c2 decay and their branching ratios are measured.
Summary
BRs of ’ 3(+–), J/ 2(+–) with improved accuracy.
F[3(+–)] determined at Ecm=3.65, 3.686 GeV.
BRs of ’ +–0K+K–; ωK+K–; ωf0(1710)ωK+K– with improved accuracy.
Summary ( cont’d )
Thanks a lot !