Recent Results on J/ψ, ψ and ψ Decays from BESII Xiaoyan SHEN (Representing BES Collaboration) Institute of High Energy Physics, Beijing shenxy@ihep.ac.cn Oct. 17 20, 2007, QWG5, DESY, Germany
Outline Results on Y(2175) Results on 0 ++ meson Results on KΛ mass threshold structure N X (1610) Measurements of ψ radiative decays Measurements of ψ to BB etc. ψ non-dd decays Summary
Beijing Electron Positron Collider (BEPC) L ~ 5 10 30 /cm 2 s at J/ψ E beam ~ 1 2.5 GeV BESI started running in 1989 BESII started in 1997 BESIII will start in 2008
BESII Detector World J/ψ and ψ(2s) Samples ( 10 6 ) 60 50 40 30 20 10 J/ψ BESII 58M J/ψ 0 30 CBAL MKII MKIII DM2 BESI BESII BESII 14M ψ(2s) VC: σ xy = 100 μm TOF: σ T = 180 ps MDC: σ xy = 220 μm BSC: ΔE/ E= 21 % σ de/dx = 8.5 % σ φ = 7.9 mr Δp/p=1.78 (1+p 2 ) σ z = 2.3 cm μ counter: σ rφ = 3 cm B field: 0.4 T σ z = 5.5 cm 25 20 15 10 5 0 ψ(2s) MKI MKII MKIII CBAL BESI BESII CLEOc 33 pb -1 ψ(3770) data
Observation of Y(2175) in J/ψ ηφf 0 (980) at BESII
Observation of a new 1 -- resonance Y(2175) at BaBar A structure at 2175MeV was observed in e + e - γ ISR φf 0 (980), e + e - γ ISR K + K - f 0 (980) initial state radiation processes Y(2175) 6.2 σ M = 2175 ± 10 ± 15 MeV Γ = 58 ± 16 ± 20 MeV Phys. Rev. D 74 (2006) 091103(R)
J/ψ ηφf 0 (980) η φ f 0 (980)
A peak around 2175 MeV/c 2 is observed in J/ψ ηφf 0 (980) 15 10 Entries Mean 152 2.262 phase space ε% 0.04 0.03 Entries Mean 468140 2.313 35.63 / 25 P1-1.960 0.1958E-02 P2 2.011 0.1130E-02 P3-0.4012 0.5356E-03 P4-0.1461 0.2239E-03 P5 0.4498E-01 0.7800E-04 events/20 MeV 0.02 5 0.01 0 1.9 2 2.1 2.2 2.3 M(φf 0 (980))(GeV/c 2 ) 2.4 2.5 2.6 M(φf 0 (980)) GeV/c 2 0 efficiency curve 1.9 2 2.1 2.2 2.3 2.4 2.5 M(φf 0 (980))(GeV/c 2 ) events/20mev 15 Entries Mean 152 2.262 10 Backgrounds from sideband estimation 5 0 1.9 2 2.1 2.2 2.3 m(φf 0 (980))(GeV/c 2 ) 2.4 2.5 2.6
M 2 (ηf 0 (980)) vs. M 2 (ηφ) (Dalitz plot) 5 4 3 5 data MC(1 -- resonance ) 2 2.5 3 3.5 4 4.5 5 M 2 (ηφ)(gev/c 2 ) 2 M 2 (ηf0 (980))(GeV/c2 ) M 2 (ηf0 (980))(GeV/c2 ) 4 3 M 2 (ηf0 M 2 (ηf0 (980)) GeV/c2 (980)) GeV/c2 M M 2 (ηφ) GeV/c 2 2 2 2.5 3 3.5 4 4.5 5 M 2 (ηφ)(gev/c 2 ) M 2 (ηφ) GeV/c 2
Fit with one resonance BG shape is fixed to sideband BG 5.5 σ M =2.186±0.010 ±0.006 GeV/c 2 Γ=0.065±0.023 ± 0.017 GeV/c 2 N events = 52±12 M(φf 0 (980)) GeV/c 2 + B(J/ψ ηy(2175)b(y(2175) φf (980))B(f (980) ππ) = (3.23 ± 0.75( stat) ± 0.73( syst)) 10 4 0 0
A resonance at 2175 MeV/c 2 is observed with significance 5σ in φf 0 (980) mass spectrum. Mass (GeV/c 2 ) Width (GeV/c 2 ) BES BABAR 2.186±0.010±0.006 0.065±0.023±0.017 2.175±0.010±0.015 0.058±0.016±0.020 Branching ratio obtained: + B(J/ψ ηy(2175)b(y(2175) φf (980))B(f (980) ππ) = (3.23 ± 0.75( stat) ± 0.73( syst)) 10 4 0 0
What is Y(2175)? Some theoretical interpretations: A conventional state? ss ssss ss An analog of Y(4260) ( )? An 4-quark state? ssg More experimental information needed.
Results on 0 ++ mesons
Lattice QCD predicts the 0 ++ scalar glueball mass in the range 1.5-1.7 GeV. f 0 (1500) and f 0 (1710) are good candidates.
PWA of J/ψ γπ + π - and γπ 0 π 0 at BESII Phys. Lett. B 642 (2006) 441
PWA of J/ψ γπ + π - and γπ 0 π 0 f 0(1500)? f 0 (1710)? + J /ψ γπ π The channels fitted in PWA: M(π + π - ) J 0 / ψ γπ π 0 M(π 0 π 0 )
PWA components: f 0 (1500) f 0 (1710)? f 0 (2020) f (1270) 2 f (1810 2 ) f 2 (2150) f (2050) 4 all 0 ++ all 2 ++
PWA results Lower 0 ++ : 0 ++ is strongly preferred over 2 ++ M = (1466 ± 6 ± 16) MeV Γ = (108 + 14 11 ± 21) MeV f 0 (1370) cannot be excluded. Higher 0 ++ : f 0 (1710) or f 0 (1790) or both? M = Γ = (1765 + 4 3 ± 11) MeV (145 ± 8 ± 23 ) MeV
J /ψ γπ + π J 0 / ψ γπ π 0 Phys. Lett. B 642 (2006) 441
About f 0 (1500) and f 0 (1710) It is first clearly observed in J/ψ radiative decays. Its production rate in J/ψ radiative decays: BR( J / ψ γf 0 (1500)) BR( f 0 (1500) ππ ) ~ 1 10 4 ( BESII) BR( f 0 (1500) ( PDG) ππ ) ~ 35% BR( J / ψ γf0(1500)) ~ 3 10 4
The production rate of f 0 (1500) in J/ψ radiative decays is lower than that of f 0 (1710): BR( J / ψ γf0(1500)) ~ 3 10 4 BR( J ( PDG) / ψ γf 0 (1710)) > 9 10 4 It may indicate: f 0 (1710) has stronger coupling to gluons than f 0 (1500) which one contains more glueball content?
New results on baryons at BESII
Observation of a strong enhancement near the threshold of K Λ mass spectrum at BES II N X * BES II J / ψ pkλ M K Λ (GeV/c2 ) PS, eff. corrected (Arbitrary normalization) M K Λ M K M Λ
Best PWA fit: (J P =½ - is favored) m Br( J = 1625 + / ψ + 5 13 7 23 MeV Γ = pnx) Br( Nx 43 + Fitted as N(1535) (becomes worse by about 5 σ (Δχ 2 =28 with d.o.f.=2)). + 10 28 7 11 MeV KΛ) = 9.14 1 10 + 1.30+ 4.25.25 8.28 5 Br( J / ψ pn(1535)) Br( N(1535) KΛ) = 4.26 0 10 + 0.15+ 4.22.14 1.70 4 Big Br.
Comparison between data and PWA fit projections MC data Fit results agree with data reasonably.
N x * is N(1535)? From BESII measurements: BR( J BR( J / ψ / ψ pn(1535)) BR( N(1535) pn(1535)) BR( N(1535) pπ ) ~ (1 ~ 2) 10 KΛ) ~ 4 10 4 4 If N x * is N(1535), its coupling to KΛ is much stronger than to pπ. Then N(1535) would have very large ssbar component (a 5-quark system).
Observation of ψ radiative decays Expected 1% BR, but only 0.05% observed. Potential channels for hadron spectroscopy study, including search for nonqqbar states, provided statistics is enough (BESIII?). ~ 0.1% more observed in this analysis. Mode BR ( 10-5 ) [m<2.9 GeV/c 2 ] γ pp-bar 2.9 ± 0.4 ± 0.4 γη 12.6 ± 2.9 ± 1.5 γ 2(π + π - ) 39.6 ± 2.8 ± 5.0 γ K S K + π - +c.c. 25.6 ± 3.6 ± 3.6 γπ + π - K + K - 19.1 ± 2.7 ± 4.3 γπ + π - ppbar 2.8 ± 1.2 ± 0.7 γ 2(K + K - ) < 4.0 γ 3(π + π - ) < 17 γ 2(π + π - )K + K - < 22 PRL99, 011802 (2007)
ψ γπ + π - and γk + K - hep-ex/07102324 Mode BR ( 10-5 ) γf 2 (1270) γπ + π - 22 ± 1 ± 2 γf 0 (1500) γπ + π - 1.5 ± 0.7 +0.9-0.4 γf 0 (1710) γπ + π - 2.4 ± 0.6 +0.8-1.1 γf 4 (2050) γπ + π - 2.8 ± 0.9 +0.8-0.6 γf 0 (2200) γπ + π - 4.6 ± 1.0 +4.5-0.9 γf 2 (1270) γk + K - 1.9 ± 0.6 +1.0-0.6 γf 2 (1525) γk + K - 0.69 ± 0.44 +0.41-0.21 γf 0 (1710) γk + K - 3.1 ± 0.6 +1.1-0.7 M(π + π - ) Fit with incoherent BWs ISR produced ρ and φ consistent with prediction γf 2 (1270) γπ + π - helicity amplitudes M(K + K - )
ψ BBbar PLB648, 149 (2007) First measurement by BESI, re-measure BR with a larger ψ data sample. SU(3) symmetry observed. 12% rule tested. Agree with CLEOc results!
ψ (J/ψ) ΛΛ+π 0 /η arxiv: 0707.1127 [hep-ex] To appear in PRD BESI/DMII: B(ΛΛπ 0 )~2x10-4 : Isospin-violation! Peaking background from one Λ modes signal First measurement!
ψ(3770) non-dd decays ψ(3770) decays most copiously into DD. ψ(3770) is a mixture of the 1 3 D 1 and 2 3 S 1, other ψ(2s)-like decays for ψ(3770) are expected. (mixing angle 12±2 o ). Many theoretical calculations estimate the partial width for ψ(3770) π + π - J/ψ. (Lipkin, Yan, Lane, Kuang, Rosner) BES observed ψ(3770) π + π - J/ψ decays. Further confirmed by CLEO-c.
Determination of BF[ψ(3770) D 0 D 0,D + D -,DD and non-dd] with the measured R values at 3.650, 3.6648 and 3.773 GeV obs σ DD Single tag method σ obs = D D ND tag 2 L Br ε = 6.14 ± 0.12± PLB 603(2004)130 0.50nb Radiative correction factor g BES II = 0.770 ± 0.014 Born σ ψ (3770) = 9.323 ± 0.253 ± 0. 801 nb BF( ψ(3770) DD) = g σ = σ obs B N N prd DD prd ψ(3770) = σ σ Born DD Born ψ(3770) = g σ obs DD Born BES II σψ (3770) Some systematic uncertainties can be canceled out Radiative correction factor obtained based on new ψ(3770) resonance parameters measured by BES-II, hep/0605107. 0 0 BF( ψ (3770) D D ) = (49.9 ± 1.3 ± 3.8)% + BF( ψ (3770) D D ) = (35.7 ± 1.1± 3.4)% BF ( ψ (3770) DD) = (85.5 ± 1.7 ± 5.8)% BF( ψ (3770) non DD) = (14.5 ± 1.7 ± 5.8)% PLB641(2006)145
Line shape of the cross sections for hadron and DD-bar production Inclusive hadrons Inclusive hadrons D 0 D 0 Inclusive hadrons D + D Mar. 2003 data set PRL(2006)121801 Simultaneously.fitting to the inclusive hadron and the DD-bar production cross sections BF Branching fractions 0 0 ( ψ (3770) D D ) = (46.7 ± 4.7 ± 2.3)% + BF ( ψ (3770) D D ) = (36.9 ± 3.7 ± 3.1)% BF ( ψ (3770) DD) = (83.6 ± 7.3 ± 4.7)% BF( ψ (3770) non DD) = (16.4 ± 7.3 ± 4.7)%
Summary Y(2175) at BESII Light 0 ++ mesons are studied in J/ψ radiative decays KΛ threshold enhancement is observed in J/ψ pkλ The measurements of ψ decays are presented. ψ non-ddbar decays We are expecting more new results at BESIII.
Backup Slides
Fit with one resonance BG is represented by a 3rd-order polynomial 4.9 σ M =2.182±0.010 GeV/c 2 Γ=0.073±0.024 GeV/c 2 N events = 61±14 + B(J/ψ ηy(2175)b(y(2175) φf (980))B(f (980) ππ) = (3.79 ± 0.87( stat)) 10 4 0 0
Fit with two resonances BG shape is fixed to sideband BG the mass and width of the second peak are fixed to those of from BaBar. 5.8 σ 2.5 σ M =2.186±0.010GeV/c 2 Γ= 0.065±0.022GeV/c 2 N1 events= 47±14 N2 events= 22±11 + B(J/ψ ηy(2175)b(y(2175) φf (980))B(f (980) ππ) = (2.92 ± 0.87( stat)) 10 4 0 0
Fit with two resonances BG is represented by a 3rd-order polynomial the mass and width of the second peak are fixed to those of from BaBar. 5.2 σ 1.7 σ M = 2.186±0.010GeV/c 2 Γ = 0.085±0.027GeV/c 2 N1= 69±21 N2= 19±11 + B(J/ψ ηy(2175)b(y(2175) φf (980))B(f (980) ππ) = (4.29 ± 1.30( stat)) 10 4 0 0