BESIII Workshop

1
BESIII Workshop Summary Fred Harris With
help from many speakers IHEP, Beijing, Oct. 15,
2001
2
I apologize for my primitive slides

• I am a beginner with Power Point, and my progress
  with Power Point in Chinese is slow.

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Before I begin

• I want to thank all the speakers, subgroup
  coordinators, organizers, and participants. I
  think the meeting has been a great success. The
  BESIII design will be greatly improved.

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Outline

• 1. Physics
• 2. Preliminary Design
• 3. Changes no time to include
• 4. Problems/questions
• 5. Relationship of CLEOc BESIII
• 6. Time Schedule
• 7. Summary

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Physics at BEPCII/BESIII

• Rich source of resonances, charmonium, and
  charmed mesons
• Transition between perturbative and
  non-perturbative QCD
• Charmonium radiative decays are the best lab to
  search for glueballs, hybrids, and exotic states

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Physics to be studied in ?-charm region

• Search for glueballs, quark-gluon hybrids and
  exotic states
• Charmonium Spectroscopy and decay properties
• Precision measurement of R
• Tau physics tau mass, tau-neutrino mass, decay
  properties, Lorenz structure of charged current,
  CP violation in tau decays
• Charm physics including decay properties of D
  and Ds, fD and fDs charmed baryons.

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• Light quark spectroscopy, mc
• Testing QCD, QCD technologies, CKM parameters
• New Physics rare decays, oscillations, CP
  violations in c- hadrons
• ..

• To answer these physics questions, need
  precision measurements with
• High statistics data samples
• Small systematic errors

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Advantages of Running on Threshold Resonances

• Charm events produced at threshold are extremely
  clean
• Large ?, low multiplicity
• Pure initial state no fragmentation
• Signal/Background is optimum at threshold

• Double tag events are pristine
• These events are key to making absolute branching
  fraction measurements
• Neutrino reconstruction is clean
• Quantum coherence aids D mixing and CP violation
  studies

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Absolute Branching Ratios
Zero background in hadronic tag modes Measure
absolute Br (D? X) with double tags Br of
X/ of D tags of D's is well determined Double
tags are pristine
MC
Decay ?s L Double
PDG CLEOc fb-1 tags
(dB/B ) (dB/B ) D0 ?K-p 3770 3
53,000 2.4 0.6 D ? K- pp 3770 3
60,000 7.2 0.7 Ds ?fp 4140 3
6,000 25 1.9
dB/B Includes Stat, sys bkgd errors
CLEO-c sets absolute scale for all heavy quark
measurements
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CLEO-c Impact semileptonic dB/B
PDG
CLEO-c
CLEO-c will make significant improvements in the
precision with which each absolute charm
semileptonic branching ratiois known
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Comparison between B factories CLEO-C
BaBar 400 fb-1
CLEO-c 3 fb-1
Statistics limited
abcdefghi
Systematics Background limited

Current
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Compare to B Factories
2.3 1.7

UL 14
6 9
0.7 1.9 0.6
2-
2
0 ???



Statistics limited.
Systematics background limited.
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CLEO-c Physics Impact (what Snowmass said)

• Crucial Validation of Lattice QCD Lattice QCD
  will be able to calculate with accuracies of
  1-2. The CLEO-c decay constant and semileptonic
  data will provide a golden, timely test. QCD
  charmonium data provide additional benchmarks.
  (E2 Snowmass Working Group)
• 
  

Imagine a World where we have theoretical mastery
of non- perturbative QCD at the 2 level
Now

Theory errors 2
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CLEO-c Flavor Physics Impact (what Snowmass
said)

• Knowledge of absolute charm branching fractions
  is now contributing significant errors to
  measurements involving bs. CLEO-c can also
  resolve this problem in a timely fashion
• Improved Knowledge of CKM elements, which is now
  not very good.

PDG
PDG
Vcd Vcs Vcb Vub Vtd Vts
7 16 5 25 36 39
1.7 1.6 3 5 5 5
B Factory Data CLEO-c Lattice Validation
CLEO-c data and LQCD
(SnowmassE2 Working Group)
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Expected Event Rates/Year at BES III
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• ?(2S) Physics
• BESII may collect 1.6 ? 107?(2S) events.
• and BESIII 2 ? 109 ?(2S)
  events/year.
• Hadronic decays, systematic study of decays with
  better BR measurements, 15 rule, VP, VT and
  other modes
• BR uncertainty 10-30 ? a few
• and 1P1 search.
• ?c decays, systematically measure BR
• BR uncertainty 10-30 ? a few
• Upper limits will be improved by two orders

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Re-measure R-values in BEPC Energy Range The
contribution to the ?(MZ2) from R-value remains
to be significant. After R values at lower energy
get measured accurately, from VEPP-2M in
Novosibirsk and ? factory in Frascati (1level),
it is worth while making the R measurement in
BEPC energy range with an uncertainty of 3,
should check if 1 level is possible? Should
try to maintain this possibility in the design of
BEPCII.

• Study of QCD and hadron production in BEPC
  energy region

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The Impact of BESs New R-Values on the SM Fit
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• Searches and Possible New Physics
• Lepton flavor violating J/? decays J/? ? e?,
  e?, ? ?
• J/? decay to DX
• CP violation in J/? decays

• With more than 109 J/?and ? events, the upper
  limits for rare and forbidden decays,
• Br measurements can reach the level of 10-610-7

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BESIII Detector Overview The straw man detector
uses the retired L3 BGO crystals as the barrel
calorimeter. This workshop will help refine our
detector greatly. I apologize for not covering
everyones talk.
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Schematic of BESIII detector
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Major Upgrades in BESIII

• Superconducting magnet
• Calorimeter BGO with ?E/E 2.5 _at_ 1GeV
• MDC IV with small cells, Al wires, and He gas
• Vertex detector Scintillation fibers for
  trigger
• Time-of-flight ?T 65 ps
• Muon detector
• New trigger and DAQ system
• New readout electronics

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Scintillating fiber for Trigger

• 1.27 mm or thinner Be beam pipe may be used
• R 3.5 cm
• 2 double-layers one axis layer and one stereo
  layer
• Scintillating fiber 0.30.3 mm2, L60 cm
• Clear fibers 0.30.3 mm2, L1.4 m
• two side readout by APD (F3) (below 300)
• Signal/noise lt6 p.e.gt / lt1p.e.gt
• ?? 50 ?m ?z 1mm
• Total of channels 27 x 8 216

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Main Draft Chamber

• End-plates with stepped shape to provide space
  for SC quads and reduce background
• Inner part stepped conical shape, cos ? 0.93
• Outer part L 190 cm, cos? 0.83 with full
  tracking volume
• cell size 1.4 cm x 1.4 cm
• Number of layers (cell in R) 36
• Gas HeC2H6 , or HeC3H8
• Sense wire 30 ?m gold-plated W ,
• Field wire 110 ?m gold-plated Al
• Single wire resolution 130 ?m
• Mom. resolution 0.8 _at_ 1GeV 1T, 0.67
  _at_1GeV1.2T
• DE/dx resolution 7

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The structure of MDC IV
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Trackerr simulation of MDC, ?pt as a function of
pt in for pion, wire resolution 130 ? m
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BGO Barrel Calorimeter

• To provide minimum space for main draft chamber
  and TOF and to obtain the necessary solid angle,
  one must modify L3 BGO crystals, and add new
  crystals
• 13 X0 ?E/E 2.5 _at_ 1GeV
• Rin 75cm , Lin 200cm cos ? 0.83
• Cut L3 BGO crystals (10752) 22 X0 (24cm)
  into 13X0 (14cm) 8.5 X0(9.5cm)
• Making new bars of 14 cm
• by gluing 9.5cm new crystal of 4.5cm
• new BGO crystals needed.  

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BGO
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BGO Summary

• A basic design of BEMC is to use L3 BGO crystals
• after cutting, grinding and polishing, with
  nearly 13X0 in length
• Building BEMC with a size R77cm, L 194cm
• Readout adopt two PD S2662 in each crystal,total
  channels 19360
• Single crystal calibration will adopt ? source
  and
• Xenon flusher for monitoring
• MC ?E/E 3/vE, ?Mp0 6 MeV
• Expected performance
• ?E/E 3/vE , ??,? 3mm/vE
• Thanks

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PID Time of Flight Counters

• Double layers TOF ( or TOF CCT)
• plastic scintillator (BC-404)
• 80 pieces per layer in ?
• R 66 75 cm,
• Thickness 4 cm, length 190 cm
• Readout both sides by F-PMT
• Time Resolution 65 ps
• 2son k/? separation
• 1.11.5 GeV/c (for polar angle 00 450)

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Dimension

• Length 1906mm
• Coverage83
• Pieces 80 /layer
• Place
• Space 105mm
• Reserved 7mm
• Thickness 49mm /layer

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CCT Principle advantages

• Cherenkov radiation
• Improve PIDGreater mass, Smaller angle,Longer
  time
• Cheap
• Simple

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Comparison of K/? sep.

• TOFTOF

• TOFCCT

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Muon Counter

• Barrel (L 3.6m ) Endcap cos? 0.9
• Consist of 12 layers streamer tube or RPC
• Rin 145cm (yoke thickness 40cm)
• Iron plate thickness 2-6 cm
• ? counter thickness 1.5 cm
• Readout hits on strips 3cm
• total weight of iron 400 tons

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The Plastic Streamer Tubes (PST)

• Larger signal pulse, good signal noise ratio
• Taking ALEPH m detector as an example
• Typical strip signals around 6 mV (at BESIII m
  detector, the strips are shorter than ALEPH, so
  the signal maybe larger than 6 mV )
• Rise time 10 ns and width at the base 100ns
• Have a rather long plateau
• Stable operation , ALEPH has stop working,
  however the PST still works very stably
• More experience
• At IHEP, Beijing, some people ever made many
  PSTs for ALEPH

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Muon acceptance
Pion contamination
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Superconducting Magnet for BESIII

• B 1 1.2 T,
• L 3.2 m
• Rin 105 cm, Rout 145 cm
• Technically quite demanding for IHEP,no
• experience before, need collaboration from
• abroad and other institutes in China, both for
• coil and cryogenic system. Also the design and
• manufacture are on critical pass.

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Superconducting Solenoid Magnet
Magnetic Field Design
The field uniformity and forces on the coil are
strongly influenced by the proximity of the iron
yoke. We will calculate the field and forces
using the ANSYS program.
B along Z axis (B01T, Poisson method)
BESIII Workshop
Zian Zhu
Beijing, Oct.13,2001
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• Luminosity Monitor
• Because the situation at the IR, the luminosity
  has to either
• be located quite far away from the IR (3-5m), or
  in front of
• Machine Q magnet, to be designed carefully.
• Accurate position determination
• Multiple detection elements at each side to
  reduce the
• variation of luminosity when the beam position
  shifted
• BGO crystals ?

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LUM Type I Extremely Forward Luminosity Monitor

• The Defining and Complimentary Counter
• Dimension of ? Scintillation fiber
• or Silicon
  Strips
• Dimension of f Plastic scintillator
• The Calorimeter
• BGO / PWO Crystal

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LUM Type IIZero Degree Luminosity Monitor

• Luminosity Monitor Based on e-(e)single
  Bremsstrahlung(SB)
• The photons ? are emitted along the e-(e)
  direction within a cone of total aperture of
  (me/Eb) with cylindrical symmetry, where Eb and
  me is energy of beam and mass of electron
  respectively.

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The photo-diode Hamamstsu S3584-09 will be
coupled through the air light guide and concave
mirror to the GSO like the Belle design
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• Interaction Region
• It is very compact at IR, very close cooperation
  is needed in the designs of detector and machine
  components at IR
• Understand the space sharing, the support,
  vacuum tight
• Understand the backgrounds from machine and how
  to reduce them,
• - Beam loss calculation (masks)
• - Synchrotron radiation (masks)
• - Heating effect (cooling if necessary)
• Understand the effects of the fringe field from
  SCQ to the detector performances

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IR Summary

• IR design is very preliminary
• Due to the background issues we must do more
  detail IR design
• Many items are not taken into account such as
  background from the loss particle, vacuum, beam
  diagnostics,

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• Trigger
• 1. Trigger rate estimation
  (using the
  same trigger conditions as now)
• Background rate, with 40 times beam current and
  half of the beam lifetime, the rough estimation
  for the background is 80 times the current rate
  (10-15), or 800-1200 Hz, taking 1500 as a design
  number
• Good event rate

When leave room for maximum luminosity to be as
calculated, 1?1033, 200 times as current event
rate, to be 1500 Hz

• Cosmic ray background can almost be negligible

Total peak trigger rate can be more than 3000 Hz,
additional trigger (software) is needed to reduce
the event rate to 2000Hz.
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The principle of BESIII trigger(2)
Time Reference
Detector
0 s

• Hardware trigger software filter
• FEE signal splitted
• trigger FEE pipeline
• Trigger pipeline clock 20MHz
• Level 1(L1) 2.4 ?s
• FEE Control Logic checks L1 with pipeline clock
• L1 YES
• moves pipeline data to readout buffer
• L1 No
• overwritten by new data

FEE pipeline
Level 1
2.4?s
Readout buffer
switch
Farms
Ev.Filter
Disk
BESIII FEE pipeline and Data flow
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Schematic of BES III Trigger
VC
DISC
Hit Count
L0 trigger Logic
FEE
L0P
TOF
DISC
Hit/Seg Count
Global Trigger Logic
MDC
DISC
Track Finder
Track Seg. Finder
DAQ
EMC
BTE Sum
Tile Processor
Tile Sum
Total Ener Sum
L1P
MU
DISC
Mu track
CLOCK
RF
TTC
2.4 ?s
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Data Acquisition System Event builder 3000 Hz ? 6
K bytes 20 Mb/s Event filtering Data
storage Run control Online event monitor Slow
control
Switch network
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Configuration and Software Structure
branch 1
branch n

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On-Line System Tasks

• Event rate 2000Hz after L2 filter
• 16MBytes/sec to persistent store
• Event Builder System
• Transport information from readout crate to
  Online(L2) farm
• L2 trigger System
• Software trigger. Selects events for storage
• Online System
• Run environment monitoring and controlling
• Experiment monitoring and controlling
• Human interface

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• Offline Computing and Analyses Software
• Computing, network, data storage, data base,
  processing management
• Supporting software package, data offline
  calibration, event reconstruction, event
  generators, detector simulation

Total CPU 36000 MIPS Data storage 500 Tbytes/y
on tapes, 24 Tbytes/y on disks Bandwidth for data
transfer 100 Mbps
Substantial manpower needed for software
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• Endcap Detector
• Two possible technologies can be used,
• CsI crystals as in the detector figure, similar
  technology as in the barrel, need endcap TOF.
• 2. Similar technique as KLOE using lead-fiber
• technique, may not need TOF counters.
• The first choice is preferred.

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BESIII CLEOc Comparison
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• Concerns and Comments
• To achieve high precision, need excellent
  detector to reduce systematic errors.
• Our design is very preliminary. More detector
  simulation to achieve design optimization. Is
  BGO the right solution?
• Need more simulation to study the physics reach
  with BESIII. We must compare to CLEOc and
  B-factory experiments. Compare on key channels
  those where BESIII has an advantage over B -
  factories. Physics group?
• Is the Pid good enough? Can do DCS decays
  cleanly?
• BESIII is comparable to the B-factory
  experiments is difficulty. We need to borrow as
  much technology, experience, software, etc. as
  possible from them and CLEOc.

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• Concerns and Comments (continued)
• Much more study about the interplay between
  detector and machine, especially in IR.
  Instrumentation. Radiation budget?
• Need 12 layers in muon system? Use for KL
  catcher?
• Each system (detector components, DAQ and
  electronics) needs RD, prototypes. Test L3 BGO.
  
• Need good communication and documentation. Web
  based.
• Refine cost and schedule.
• When to have the next workshop?
• Need BESIII review panel. When?

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• Major issues related with BESIII design
• The radius of crystal calorimeter, affecting
  performance and cost. Possibility of using CsI
  crystals as EMC.
• Backgrounds associated with machine operation,
  the design of interaction regions, vacuum, masks,
  etc.
• Critical detector sub-sys. affecting the overall
  schedule
• - SC magnet, including magnet supporting
  structure
• - EMC calorimeter
• - Main drift chamber

Experienced man power big issue
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• CLEOC
• CLEOc project has already benefited BEPCII now
  2 ring collider.
• Collaboration/cooperation between BES and CLEO?
• BESIII follows CLEOc.
• BESIII can benefit greatly from CLEOc expertise
  and experience. How to optimize? BESIII
  physicists join CLEOc at Cornnell?
• CLEOc physicists join BESIII? High luminosity
  tau charm physics after CLEOc.
• Ideas?

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Schedule

• Feasibility Study Report of BEPC II has been
  submitted to the funding agency .
• Technical Design Report of BEPC II to be
  submitted by first
• half of 2002.
• Construction started from Summer of 2002
• BESII detector moved away Summer of 2004, and the
  BESIII iron yoke started to be assembled, mapping
  magnet early 2005
• Preliminary date of the machine long shutdown
  for installation Spring of 2005
• Tuning of Machine Beginning of 2006
• BESIII detector moved to beam line, May 2006
• Machine-detector tunning, test run at end of 2006
  

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Intl. Cooperation on BEPC II / BES III

• Intl. cooperation played key role in design,
  construction and running of BEPC/BES.
• Intl. cooperation will play key role again in
  BEPC II / BES III design, review, key
  technology, installation, tuning
• Participation of foreign groups is mostly
  welcomed.
• BESIII should be an international
  collaboration.

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• Summary
• BEPC energy region is rich of physics, a lot of
  important physics results are expected to be
  produced from BESIII at BEPCII.
• Detector design is started, need a lot of
  detailed work to finish detector design!
• Very interesting and very challenging project.

Thanks