Date post: | 01-Jan-2016 |
Category: |
Documents |
Upload: | george-foster |
View: | 32 times |
Download: | 1 times |
General Review of BES Physics,
Achievement and Future
Representing BES collaboration
Weiguo Li
IHEP, CAS
MENU 2004
Beijing, Aug. 30, 2004
BEPC consists of Linac 、 Storage Ring 、 Detector(BES ) and Synchrotron Facility(BSRF). Ground breaking in 1984 , completed in 1988 within budget and according to the schedule. Soon after reached the designed performances.
BESII Detector BESII Detector ((1995-1997 upgraded1995-1997 upgraded))
VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 250 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.4 % = 7.9 mr B field: 0.4 T p/p=1.8(1+p2) z = 2.3 cm Dead time/event: 〈 10 ms
Korea (4)
Korea University Seoul National University
Chonbuk National UniversityGyeongsang Nat. Univ.
Japan (5)
Nikow UniversityTokyo Institute of Technology
Miyazaki UniversityKEK
U. Tokyo
USA (4)
University of HawaiiUniversity of Texas at Dallas
Colorado State University Stanford Linear Accelerator Center
UK (1)Queen Mary University
China (18)IHEP of CAS
Univ. of Sci. and Tech. of ChinaShandong Univ., Zhejiang Univ.
Huazhong Normal Univ. Shanghai Jiaotong Univ.
Peking Univ., CCAST Wuhan Univ., Nankai Univ.
Henan Normal Univ.Hunan Univ., Liaoning Univ.
Tsinghua Univ., Sichuan Univ. Guangxi Univ., Guangxi Normal Univ.
Jiangsu Normal Univ.
Data collected with BESI and BESII Ecm (GeV)
Physics BES Data Other Lab.
3.10 J/ 7.8106 8.6106
3.69 (2S) 3.9106 1.8106
4.03 1.0105 LEP
4.03 DS, D 22.3 pb-1 CLEO
3.55 m scan m 5 pb-1
2-5 R scan
2. 2.2,2.6,3.0
R value,
QED, (g-2)
QCD
6+85 points 2, MarkI Crystal Ball Pluto……
3.1 3.69 3.78
J/ (2S) (3770)
5.8107
1.46107
~27 pb-1
world largest J/ and ’ data samples (10(1066))
J/
0
10
20
30
40
50
60
MarkIII DM2 BESI BESII
01.11-02.399.11-01.3
0
2
4
6
8
10
12
14
MKI MKII MKIII CBAL BESI BESII CLEOc
BESII Detector Simulation
Understanding the detector simulation and Data/MC consistency are very important to the physics results,
BES simulation,
SOBER(BESI), detector gaussian response, no
hadron interaction (from MarkIII)
SIMBES(BESII), Geant3 based, better detector
responses
For example, the wire resolution is affected by the dE/dx of the MDC hits.
Example: Wire Resolution of MDC
dE/dx dependence Double Gaussian
Seems most difficult part!
Wire res. vs dE/dx (data)
Q OF HITS
Deviation
Important Variables To Be Checked
Main Drift Chamber
Reconstruction efficiency
Momentum resolution
Error matrix and chi2
dE/dx (PID efficiency)
TOF
TOF quality (efficiency)
Resolution &
PID efficiency for , K, p
Shower Counter
Reconstruction efficiency
Resolutions (E, z, phi)
Energy distributions for
e, mu and hadrons
Events used for Data/MC comparison
J/ e+e-, +-, pp, , ,
pp+-
(2S) J/ +- , etc.
Impacts on Physics Results (I)
BR(J/ +-0 ) from SIMBES is about 30%
higher than that from SOBER. It is also
about 30% higher than PDG.
Br(J/+-0) = (21.840.052.01)10-3
Babar’s new result confirms our result.
Hight lights of BESHight lights of BES Physics Results
Precise measurement of the mass of tau lepton
Precise measurement of R value in the energy ran
ge of 2-5 GeV
(2S) decays
Study many decay modes and the 12% rule
J/ decays
Light hadron spectroscopy, search for multi-quar
k candidates
(3770) decays and D physics
In 1992, BES made a scan over tau mass production threshold and measured the tau mass,
BES +0.18+0.25M = 1776.96 -0.21-0.17
PDG +0.29M = 1776.99 -0.26
Corrected a mass shift of 7 MeV from previous measurements, proved that tau is one of the leptons.
R Measurement
• With an average error of 6.6%, compare with 15-20% errors from previous measurements • fine measurement of the structure at 3.7-4.5GeV
Prediction of Higgs mass from standard model
GeVm
GeVm
H
H
212
98 5838
GeVm
GeVm
H
H
170
62 5330
(95% C.L.)
Recent Physics Results
J/ Decays
Threshold enhancements in pp and pK
in +- ; in K*(892)0K+- / K+K- +-
Study of scalars in J/ decays
Many BF measurements
See SHEN, Xiaoyan’s talk for details
(2S) decays
12% Rule; (2S) ;
in (2S) J/ +-;
Many decay BF measurements of (2S) and CJ
(3770) decays
D BF measurements, (semi-leptonic, purely leptonic, hadronic decays)
DD cross-section;
(3770) resonance parameters from scanning
Anomalous enhancement of pp near thresholdPhys. Rev. Lett., 91 (2003) 022001
Mass: M=1859 MeV/c2
Width: < 30 MeV/c2 (90% CL)
J/pp
M(pp)-2mp (GeV)0 0.1 0.2 0.3
BG curve Eff. curve
2/dof=56/56
Fitted peak
Fitted curve +3 +510 25
BES II
Observation of an enhancement near p mass threshold in J/pK
process
The clear Λ signal in data shows high purity of signal.
Data/MC
Accepted by P. R. L., hep-ex/0405050
Phase Space
Data Data
pM pM
pK Kp
S-wave BW fit results
M = (2075 12 5) MeV
Γ = (90 35 9) MeV
BR = (5.9 1.4 2.0) 10-5
2/d.o.f = 31.1/26 About 7σ effect
Phase space
Near K threshold enhancement inJ/pK
)(GeV/c2KΛM
Eve
nts
/10
MeV
Nx
Nx
Nx
)(GeV/c2 MMM KKΛ
PS, eff. corrected
(Arbitrary normalization)
• Its mass and width:
(large uncertainty near threshold, high statistics is crucial!)Mass 1500~1650MeV
Width 70~110MeV
JP favors 1/2-
• large BR(J/pNx)Br(NxK) (2*10-4). What is it??
Possibly N*(1535) with large coupling to K K molecular state ??
BRs for (2S)(,,)(,,’),K*K
measured
PWA for (2S)+ - 0
Background from continuum considered
using Ecm=3.65 GeV data sample
(2S) decays and 12% Rule
VP Modes
BESII Preliminary
VP Mode (Con’t)
Dalitz plot for J/ and (2S) 3 are very different
J/ Ψ 3 Ψ(2S) 3
PRD70 (2004) 012005
hep-ex/0408047 submitted to PRL
Results on BRs____________________________________________________________________________________________________________________________________________
BR BESII (10 – 5 ) PDG04 (10 – 5 )
Ψ(2S) + - 0 18.1 1.8 1.9 8 5
Ψ(2S) 5.1 0.7 0.8 < 8.3
Ψ(2S) (2150) + - 0 19.4 2.5____________________________________________________________________________________________________________________________________________
# 1st measurement or precision much improved
# Interference taken into account
BESII Preliminary ( PWA )
1. VP Mode (Con’t)
1.1 (Con’t)
2.111.2
D BF Measurements
Semi-leptonic decays
BF(D0 K-e+e) = (3.820.400.27)%, PDG (3.58 0.18)%
BF(D0 -e+e) = (0.330.130.03)%, PDG (0.36 0.06)%
Phys. Lett. B597(2004)39-46
preliminary
BF(D+K0e+e) = (8.471.920.66)%, PDG (6.7 0.9)%
= 1.15 0.290.09 PDG 1.4 0.2
Purely Leptonic decays,
Three D+ + candidates,
)(
)(0
0
e
e
eKD
eKD
MeV)365( 3212128113D
f
(3770) productionTo get right resonance parameters, the two resonance productions and decays should be considered simultaneously. In this way the “correct” QED background ( ) can be determined correctly !
udsR
'
)3770(
BES-II Preliminary !
[GeV] cmE
obshad
0.142.24udsR
Fitting results
M(3770) =3772.51.3 MeV
PDG: 3769.92.5 MeV
tot= 25.5 4.0 MeV
PDG: 23.6 2.7 MeV
ee= 22536 eV
PDG: 260 40 eV
M((3770)- (2S)) =86.8 1.3M eV
PDG: 83.9 2.4 MeV
nb 99.011.9|MeV 8.3772)3770(
sprd
D Cross-section
preliminary
From D0K-+, K-+ + -
D+K- + +
obs(DD)=6.140.120.50 nb
tree(DD)=7.880.150.74 nb
Evidence for (3770)J/ +-
preliminary
BF( (3770)J/ +- )=(0.3420.142 0.083)%
( (3770)J/ +- )=(8032 21)KeV
BEPCIIBEPCII Design GoalsDesign Goals
Beam energy 1 – 2.1 GeV
Optimal energy 1.89 GeV
Luminosity 1 x 10 33 cm-2s-1 @ 1.89 GeV
Linac requirements Full energy injection: 1.55 1.89 GeV Positron injection rate > 50 mA/min
Dedicated SR 250 mA @ 2.5 GeV
Physics
Channel C. M. Energy
(GeV) Peak Lumi.
(1033cm-2s-1)
Cross Section
(nb)
Events per
Year
J/ 3.097 0.6 ~3400 10109
3.670 1.0 ~2.4 12106
3.686 1.0 ~640 3.0109
D 3.770 1.0 ~5 25106
Ds 4.030 0.6 ~0.32 1.0106
Ds 4.140 0.6 ~0.67 2.0106
Expected Number of Events in One Year’s Running
With such a data sample, a precise measurements are expected
BEPCII/BESIII Physic Goals
• Precise measurements of J/、 (2S) 、 (3770 )Decays
• Precise measurement of CKM parameters
• Light quark hadron spectroscopy
• Excited baryon spectroscopy
• Other D and Ds physics: – precise measurement of D and Ds decays– measurement of fD, fDs – D0 –D0 mixing
• Check VDM, NRQCD, PQCD, study puzzle
BEPCII/BESIII Physics Goals ( 2 )• Mechanism of hadron production , low energ
y QCD : precise R measurement• physics : charged current , m and m
• Search for new particles: 1P1 、 c ? 、 glueballs 、 quark-gluon hybrid 、 exotic states…
• Search for new phenomena: – rare decays;– lepton number violation; – CP violation in J/ and (2s) decays;
system BES III
XY = 130 m
MDC P/P = 0.5 %(1 GeV)
dE/dx = 6-7 %
EMC E/√E = 2.5 %(1 GeV)
z,= 5-6mm (1 GeV)
TOF T = 90-100 ps Barrel
110 ps endcap
counter 9- 8 layers
Magnet 1.0 tesla
BESIII Main Parameters
BESIII Status• Design has been finished
• Most of the R&D work successful
• Detailed Budget and CPM available
• Most of the budget have been contracted
• Mass production has been started:– CsI Crystals– RPC muon chambers– Support structure and Yoke– Superconducting magnet– Drift chamber structure
BESIII Schedule
• 11/2004: supporting structure/yoke installation• 2-3/2005: endcap muon chamber installation• 5/2005: magnet installation• 10/2005: magnetic field mapping• 2/2006: EMC installation• 3/2006: MDC/TOF installation• 7/2006: BESIII debug and commissioning,
Cosmic ray• 10/2006: BESIII detector in beam-line• 11/2006: commissioning detector/machine
A few items are on critical path for BESIII
• Mechanical support and Yoke
• Mechanical support of Barrel EMC; Crystal
production
• Super-conducting Magnet
• Offline software
Technical Challenge
• Background issues
• PID, MDC, EMC performance;
• DAQ system
BESIII Collaboration
There are about 18 Chinese institutes in BES collaboration, about 10 are actively involved in BESIII project,
Physicists from US and Japan are participating in BESIII project,
More foreign participants are welcome.
Summary
BES has produced many interesting results, a good place to study light hadron spectroscopy, excited baryons, etc.
BEPCII/BESIII project will provide data wit
h hundreds more statistics, with a better dete
ctor, should play an important roll in underst
anding the mesons and baryons.
子系统 BES III BESII
XY (m) = 130 250
MDC P/P (0/0) = 0.5 %(1 GeV)
2.4% (1 GeV)
dE/dx (0/0) = 6-7 % 8.5%
电磁量能器 E/√E(0/0) = 2.5 %(1 GeV)
z,(cm) = 0.6cm/√E
22% (1 GeV) 3 cm /√E
飞行时间 T (ps) = 90-100 ps barrel 110 ps endcap
180 ps barrel
350 ps endcap
计数器 9- 10 layers 3 layers
磁场 1.0 tesla 0.4 tesla
BESIII 和 BESII 比较
Trk. eff. -- Lamda Lamdabar
CUT Data SIMBES SOBER
Trk Rec. 94.7% 95.0% 99.1%
Good Trk 94.6% 94.6% 98.9%
CUT Data SIMBES SOBER
Trk Rec. 94.4% 94.2% 99.3%
Good Trk 94.1% 93.8% 99.2%
proton
antiproton
Trk. eff. -- Lamda Lamdabar
CUT Data SIMBES SOBER
Trk Rec. 88.8% 88.6% 93.0%
Good Trk 80.8% 81.7% 88.8%
CUT Data SIMBES SOBER
Trk Rec. 90.0% 90.2% 94.0%
Good Trk 85.6% 84.9% 90.5%
pion+
pion-
Good trk eff. (including hadron interaction
cross section) is fine in SIMBES.
Good trk. eff. has also been checked in e+e- and pipiJ/psi channels, all fine in SIMBES (NOT for SOBER)
See also Feng’s talk
Summary of SIMBES Checks
SIMBES is an ‘effective’ simulation of detector. Data/MC consistency has been greatly improved.
SIMBES has big impacts on physics results, not only on BRs. Many PDG results will be systematically renewed.
No big problems are observed in the systematic checks of SIMBES for the variables used in the physics analysis, although it is not perfect.
BESIII needs much more careful checks. Hope our experience may help the BESIII simulation.
nb 0.310.093.58 00 obs
DD
nb 0.260.082.56 obs
DD
nb 0.500.126.14 obsDD
Observed cross sections for DD-bar production at 3.773 GeV
KD0
KD0
KD
Preliminary !