Recent BES charmonium resultsRecent BES charmonium results Frederick A. Harris

University of HawaiiJiangchuan CHEN

Institute of High Energy PhysicsBeijing, China

HEP2003Europhysics Conference on High Energy Physics

July 17 – 23, Aachen, Germany

Representing:

OUTLINE

Introduction J/ p p-bar c mass, width, and BFs c Λ Λ-bar (2S), J/ KSKL (3770) π+π -J/ψ Summary

The Beijing Electron Positron Collider

L ~ ~51030 /cm2s at J/ peak

Ecm~2-5 GeV

A unique e+e- machinein the -charm energyregion since 1989.

Beijing, China

BESII Detector

VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 % = 7.9 mr B field: 0.4 T p/p=1.7(1+p2) z = 2.3 cm

BESII Monte Carlo Simulation

•A Geant3 based package SIMBES for BESII simulation. •We check the data/MC consistency in J/ψ e+e-, μ+μ-, pp, ρπ, ΛΛ high purity channels. The consistency is reasonable.

•It is applied in the BES analysis at J/ψ energy region the first time.

Data Collected with BESI and BESII

This year: ~20 pb-1

below (2S) ~ 6 pb-1

World J/ and (2S) Samples (×106)

J/ (2S)

0

10

20

30

40

50

60

MarkI I I DM2 BES I BES I I

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII

NN bound states (baryonium)??

+ n +

deuteron:

loosely bound 3-q 3-q color singlets with Md = 2mp-

baryonium:

loosely bound 3-q 3-q color singlets with Mb = 2mp-?

attractive nuclear force attractive force??

There is lots & lots of literature about this possibility

study pp from J/pp

ppe+e

Bardin etal

e+ehadronsFENICE e+e6

2mp

2mp

Fit: M = 1870 ± 10 MeV= 10 ± 5 MeV

R. Calabrese PEP-N work-shop proceedings

DM2 unpub.

Motivations:Is there a narrow JPC=1 pp system near Mpp

=2mp?

study pp from J/pp•C-parity = +

•S (P?)-wave (for Mpp 2mp)

• probes JPC= 0(0?)states

•complements ppee and ee annihilation

•unpolluted (by other hadrons) environment

Use BESII’s 58M J/ decays

J/ppSelect J/pp4-C kinematic fit

dE/dx for proton id

non-pp bkg small

main bkg from J/pp

????

• J/ccpp (calibration reaction)

Study J/0pp bkg with MC & data

J/0pp (data)

three-bodyphase spaceMonte Carlo

J/0pppp (MC)

M(pp)-2mp (GeV)

no peak!!

Fit to data

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

J/pp

M(pp)-2mp (GeV)

0 0.1 0.2 0.3

3-body phase spaceacceptance

2/dof=56/56

fitted peak location

acceptance weighted BW +3 +5

10 25

PPbar cos distribution

1+cos2(expected for

J/)

sin2

M(pp)<1.9 GeV

PP

mass determination bias

threshold

observed peak

BW “peak”below-

threshold mass & widths measurement

s can be biased

when there is background

include possible biases as(asymmetric) statistical &

systematic errors

if what we see is an S-wave resonance:

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

+3 +510 25

Phys. Rev. Lett. 91, 022001 (2003).

J/pp Results

c ParametersPrecise (mJ - mc) needed for potential models.But c mass not well determined: PDG02 CL = 0.001

Previous BES Results •4 M(2S) Sample: Phys. Rev. D60 (1999)• 7.8 M J/ Sample: Phys Rev.D62 (2000)

Width Measurements

C measurements with BESII 58 M J/ sample

• Channels: J/ C , C K+K-+- , +-

+-, K+/- K0S-/+, , and pp.

• Use PID for /K/p separation.• Select events based on chisquare from

kinematic fit. • Use Umiss = Emiss – pmiss and P2

t (transverse momentum relative to ) to remove 0

background.

M(pp)

J/ C , C PP

M(K+K-+-) M(+- +-)

M(K+/- K0S-/+)

M()

Results: Mass and WidthResults: Mass and WidthCombined fit of five channels:M(C) = 2977.5 1.0 1.2 MeV/c2

(C) = 17.0 3.7 7.4 MeV/c2

PDGM(C) = 2979.7 1.5 MeV

(C) = 16.0 +3.6-3.2 MeV

Phys. Lett. B555, 174 (2003)Phys. Lett. B555, 174 (2003)

J/ ηc

Results: Mass and WidthResults: Mass and Width

PDG2002

BES2003

J/ ηc

Results: Branching Fraction Preliminary

Systematic Errors

Product BranchingFractions

J/ ηc

Results: Branching Fraction Preliminary

Results: Branching Fraction Preliminary

Dividing by B(J/ ηc ) = 1.3 ± 0.4 % (PDG2002)

B(ηc φ φ) is smaller than PDG and agrees with Belle

measurement (hep-ex/0305068).

† H.C. Huang et al., hep-ex/0305068 * Calculated from results in F. Fang, et al., PRL 90:071801,2003.

J/ ηc

CJ Λ Λ-bar

Color octet mechanism (COM) important for P-wave quarkonium decays.

G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995).H.-W. Huang and K.-T. Chao, Phys. Rev. D54, 6850 (1996).J. Bolz et al., Phys. Lett. B392, 198 (1997).

COM and a nucleon wave function give reasonable agreement with BES Γ (cJ p p-bar) and other results.

The partial widths of other baryons can be predicted:

Γ (cJ Λ Λ-bar) ~½ Γ(cJ p p-bar) for c1 and c2

S. M. Wong, Eur. Phys. J. C14, 643 (2000).

CJ Λ Λ-bar

Here we study:(2s) cJ ΛΛ-bar

p- p-bar +.Select events with 4 charged tracks and > 0 ’s.Use PID for charged tracks. Prob > 0.014C kinematic fit. Select smallest chi-square and require Prob > 0.01.See clear Λ Λ-bar signal.

CJ Λ Λ-bar

Select events around cluster.

See clear lambda peak in m(p).

mΛ = (1114.3 ± 0.5) MeV/c2.

Agrees well with PDG.

CJ Λ Λ-bar

Sideband background Monte Carlo Comparison

Plot m(Λ Λ-bar)

CJ Λ Λ-bar

Main physics backgrounds:

(2s) Λ Λ-bar

0 0-bar

cJ , cJ 0 0-bar

Fit:

• Monte Carlo background shape.

• Background level floating.

Fix cJ widths to PDG values.

Use Monte Carlo mass resolutions.

Fitted masses agree with PDG.

CJ Λ Λ-bar

Results

B(CJ p p-bar)(10-4) 2.2 ± 0.5 0.72 ± 0.13 0.74 ±

0.10

Phys. Rev. D67, 112001 (2003).Phys. Rev. D67, 112001 (2003).

For N((2s) )use (2s) + - J/, J/ p p-bar.Many systematic errors cancel.

PDG

First Observation of ψ(2S) decay to KS0KL

0

and measurement of J/ψ decay to KS0KL

0

Motivations

--Phase between the 3-gluon and single photon annihilation amplitudes:

±90° at J/ψ180° at ψ(2S) two body decay

(M. Suzuki, Phys. Rev. D63 054021(2001)

--12% rule test Br(ψ (2S) KS0KL

0 )=Br(J/ψ KS0KL

0)*12% ?

Br(J/ψ KSKL) comes from DMII and MARK III more than 14 years ago, with relative errors 18%.

--

Here we report a measurement of ψ(2S) decay to KS

0KL0 to test above phase rule.

Event selection criteria

--Only two good charged tracks and assumed to be π+ and π –.

--Neutral clusters Eγtot < 1.0 GeV is used to remove the

backgrounds.

Only reconstruct KS, look at KS momentum for signal

PKs ~ 1.774 GeV

ψ (2S) KS0KL

0

KS0 momentum distribution. The KS

0 mass sideband background is shown by shaded histogram.

KS0KL

0 signal

KS sideband

ψ (2S) KS0KL

0

Background in KS0 momentum distribution. (f) the dots are

data, blue shaded histogram is background from(e), the green shaded region is the sum of the background from (a-d).

χc0 KS

0KS0

ccKKc .)892( 00*1 00

2 SSc KK

ccKKS .)892()2( 00* KS0 mass sideband (f)

Fit of the KS0 momentum

Spectrum: dots are data, andshaded histograms are fromsideband events and other MC simulated backgrounds.

The fit yields 164±14 events, and the efficiency for detecting

with is(41.44±0.49)% from MC.00)2( LKSKS

ψ (2S) KS0KL

0

0SK

(1768.5±3.3)MeV/c

PreliminaryPreliminary

Fit to the KS0 momentum

spectrum: dots are data, shaded histograms are from mass sideband and other MC simulated backgrounds.

Ks mass sideband background

ccKKJ .0)892(*/

(1488.2±0.7)MeV/c

PreliminaryPreliminary

The fit yields 2127±45 events, and the efficiency for detecting with is (37.57±0.22)% from MC.00/ LS KKJ

0SK

Data Analysis

J/ψ KSKL

(With the same way)

Preliminary ResultsPreliminary Results

---

With above branching ratio and the branching ratio of

, from PDG, phase angle

between strong decays and the electromagnetic of the ψ(2S)

to pseudoscalar meson pairs is found to be about 90°

--- )2( S KKS)2(

ψ (2S) KS0KL

0

Preliminary Results

(PDG value: Br(J/ψ KSKL)=(1.08±0.14)×10-4)

The interesting is that Qh is enhanced relative to the “12% rule”, while in most cases where it disagrees, it is suppressed.

J/ψ KSKL

Evidence of ψ(3770) non- decay to π+π – J/ψ

DD

Motivation---ψ(3770) is believed to be a mixture of the 23S1 and 13D1

states of the system and to decay almost entirely to pure .

ccDD

(P.A. Rapidis et al., (MARK-I), Phys. Rev. Lett. 39, 526(1978))

--- Recently, some theoretical calculations point out that ψ(3770) could decay to non- final states.DD

(H.J. Lipikin, Phys. Lett. B179, 278(1986), Y.P. Kuang, Phys. Rev. D65, 094024(2002) )

Data sample and Monte Carlo

-- Data sample: 6.6±0.4 pb-1 of data taken at Ecm=3.773 GeV 1.4±0.1 pb-1 at Ecm=3.738 GeV to 3.885GeV (by BESII/BEPC)

--Event generator: We developed a new generator isrpsi which included J/ψ and ψ(2S) and other resonance production due to initial state radiation effect.

Event Selection for ψ(3770) → π+π J/ψ, J/ψ→ll

4 good charged tracksPID for e and muRemove events with photon conversion4-c kinematic fit

In the figure open circles are data, and the histogram are MC. In the (b), the solid smooth curve is the fit to the data.

/)3770( J /)3770( J

/)2( JS /)2( JS

/)2( JS

/)3770( J

Results---Data sample: Number of ψ(3770) = (5.7±1.3)×104

---Signal events: Nevt= 6.8±3.0(Ntot= 9.0 ±3.0, in which 2.2 ±0.4 from backgrounds)

Efficiency: 0.171±0.002

ψ(3770) → π+π J/ψ

Summary

Observation of an enhancement in pp system near 2mp in J/pp. If S-wave:

M=1859 MeV/c2

< 30 MeV/c2 (90% CL)

Exclude all possibilities from known mesons. Baryonium?

+3 +510 25

Summary

New C mass and width:

M(C) = 2977.5 1.0 1.2 MeV/c2

(C) = 17.0 3.7 7.4 MeV/c2

New C Branching fractions - preliminary

Summary

New branching ratio results on B(cJ Λ Λ-bar). Disagrees with Color Octet Model?

First observation of KS0KL

0 in ψ(2S) decays:

Summary

•Measurement of the branching fraction for J/ψ decay to KS0KL

0

•Evidence of ψ(3770) non- decay to π+π -J/ψDD

(PDG value: Br(J/ψ KSKL)=(1.08±0.14)×10-4)

Thank You!

BESII Simulation

A Geant3 based package SIMBES for BESII. It agrees with data well and is applied in the BES analysis at Charm energy region first time.

J/ψ, ψ (2S) hadrons. Where shaded are BES data

and solid histograms are SIMBES results.

JJ//ψψ ψ(2S)ψ(2S)

Ks

KL

π+

π -

Event selection criteria--Only 2 good charge tracks

--The 2 charged tracks are assumed to be π+ and π -.

--Neutral clusters Eγtot < 1.0 GeV

is used to remove the backgrounds.

Only reconstruct KS, look at KS momentum for signal

PKs ~ 1.774 GeV

--Without extra photon

ψ (2S) KS0KL

0

Trigger

PKS>1.7 GeVFig.1 Scatter plot of π+π –

invariant mass versus thedecay length in the transverse XY plane forevents with KS

0 momentum greater than 1.7 GeV/c.

Fit of π+π – invariant mass distribution.

ψ (2S) KS0KL

0

Tigger effect

Fig.3 the comparison of the KS0

decay length. Since no triggereffect in the MC simulation now,use a correction factor (76.0±1.8)%to the MC efficiency for ψ(2S)decay to KS

0KL0

Cut here(LXY>1cm)

Fig.4 The KS0 momentum

distribution. The KS0 mass

sideband background isshown by shaded histogram.

KS0KL

0 signal

KS sideband

Psi(2S)->KSKL systematice erorr

PreliminaryPreliminary

PreliminaryPreliminary

Psi(2S)->KSKL Phase angle

C.Z. Yuan et al. Phys. Lett. B567 (2003) 67-72