Post on 31-Dec-2015
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.
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
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
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.
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: 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
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)
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.
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