BESIII WorkshopBESIII Workshop

SummarySummary

Fred Harris

With help from many speakers

IHEP, Beijing, Oct. 15, 2001

I apologize for my primitive slidesI apologize for my primitive slides

I am a beginner with Power Point, and my progress with Power Point in

Chinese is slow.

Before I beginBefore 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.

OutlineOutline

1. Physics2. Preliminary Design3. Changes – no time to include4. Problems/questions5. Relationship of CLEOc – BESIII6. Time Schedule7. Summary

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 gl

ueballs, hybrids, and exotic states

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.

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

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

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 determinedDouble tags are pristine

B/B IncludesStat, sys& bkgd errors

Decay s L Double PDG CLEOc fb-1 tags (B/B %) (B/B %)

D0 K-+ 3770 3 53,000 2.4 0.6D+ K- ++ 3770 3 60,000 7.2 0.7Ds 4140 3 6,000 25 1.9

CLEO-c sets absolute scale for all heavy quark measurements

KD

tagD

MC

e

eD

eKD

eKD

eD

eD

eKD

eKD

eD

eD

eKD

eKD

c

s

s

s

:12

:11

:10

:9

:8

:7

:6

:5

:4

:3

:2

:1

0*

0

0

0

_0*

_0

0

0

*0

0

0102030405060708090100

1 2 3 4 5 6 7 8 9 10 11 12

Decay modes

Err

or (%

)

CLEO-c Impact semileptonic dB/B

CLEO-c

PDG

CLEO-c will make significant improvements in the precision with which each absolute charm semileptonic branching ratiois known

COMPARISON

0

5

10

15

20

25

30

Erro

r (%

)

Df

sDf

)KD(Br

)D(Br S

)KD(Br 0

BaBar 400 fb-1

Current

Comparison between B factories & CLEO-C

Systematics & Background limited

CLEO-c 3 fb-1

Statistics limited abcdefghi

Compare to B FactoriesCLEO- C BaBar Current2-4f b-1 400 f b-1 Knowledge

f _ D |Vcd| 1.5- 2% 10- 20% n.a.f _ Ds |Vcs| <1% 5- 10% 19%

Br(D+ -> K) 1.5% 3- 5% 7%Br(Ds -> ) 2- 3% 5- 10% 25%Br(D->l) 1.4% 3% 18%Br(c -> pK) 6% 5- 15% 26%

A(CP) ~1% ~1% 3-9%x'(mix) 0.01 0.01 0.03

Systematics & background limited.

2.3% 1.7%

0.7%1.9%0.6%

2-0 K 2%

6 – 9

Statistics limited.

UL14%

• 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)

CLEO-c Physics Impact (what Snowmass said)

Imagine a

World where

we have theoretical

mastery of non-

perturbative QCD

at the 2% level

Now

Theoryerrors = 2%

• Knowledge of absolute charm branching fractions is now contributing significant errors to measurements involving b’s. CLEO-c can also resolve this problem in a timely fashion

• Improved Knowledge of CKM elements, which is now not very good.

CLEO-c Flavor Physics Impact (what Snowmass said)

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(Snowmass:E2 Working Group)

CLEO-cdata andLQCD

PDGPDG

Expected Event Rates/Year at BES III

Particle Energy Single Ring （1.2fb

-1 ） Double Ring (4fb

-1)

D0 ’’ 7.0106 2.3107

D+ ’’ 5.0106 1.7107

DS4.14GeV 2.0106 0.72107

+- 3.57GeV3.67GeV

0.61062.9106

0.21070.96107

J/    1.6109 6109

’    0.6109 2109

ψ(2S) PhysicsBESII may collect 1.6 107ψ(2S) events.

and BESIII 2 109 ψ(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

c

Re-measure R-values in BEPC Energy RangeThe contribution to the (MZ

2) 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 (~1%level), 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

The Impact of BES’s New R-Values on the SM Fit

Searches and Possible New Physics• Lepton flavor violating J/ψ decays J/ψ e, e,

• J/ψ decay to D+X

• CP violation in J/ψ decays

• With more than 109 J/ψand ψ’ events, the upper limits for rare and forbidden decays,

Br measurements can reach the level of 10-6~10-7

BESIII Detector OverviewThe “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 everyone’s talk.

Schematic of BESIII detector

Major Upgrades in BESIII • Superconducting magnet• Calorimeter: BGO with E/E ~ 2.5 % @ 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

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: 0.3*0.3 mm2, L~60 cm• Clear fibers: 0.3*0.3 mm2, L~1.4 m• two side readout by APD (Φ3) (below –300)• Signal/noise: <6 p.e.> / <~1p.e.>• ~ 50 m z ~ 1mm• Total # of channels: 27 x 8 = 216

Main Draft Chamber• End-plates with stepped shape to provide space for SC quads and re

duce background– Inner part: stepped conical shape, cos θ= 0.93– Outer part: L = 190 cm, cosθ= 0.83 with full tracking volume

• cell size: ~ 1.4 cm x 1.4 cm• Number of layers (cell in R): 36• Gas: He:C2H6 , or He:C3H8

• Sense wire: 30 m gold-plated W , • Field wire: 110 m gold-plated Al• Single wire resolution : 130 m• Mom. resolution : 0.8 % @ 1GeV &1T, 0.67% @1GeV&1.2T• DE/dx resolution: 7%

The structure of MDC IV

Trackerr simulation of MDC,

pt as a function of pt in % for pion, wire resolution 130 m

BGO Barrel CalorimeterTo 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 % @ 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.  

BGO

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: R~77cm, L~ 194cm• Readout: adopt two PD S2662 in each crystal,total channels: 19360 • Single crystal calibration will adopt γ source and Xenon flusher for monitoring• MC: E/E ≤ 3%/√E, Mπ0 ~ 6 MeV • Expected performance:

E/E ≤ 3%/√E , , ≤ 3mm/√E Thanks

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 • 2σon k/ separation: 1.1~1.5 GeV/c (for polar angle 00~ 450)

Dimension• Length: 1906mm• Coverage:~83%• Pieces: 80 /layer• Place:• Space: 105mm• Reserved: 7mm• Thickness:

49mm /layer

CCT Principle & advantages

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

Comparison of K/ sep.• TOF+TOF • TOF+CCT

Muon Counter

• Barrel (L ~ 3.6m ) + Endcap: cos ~ 0.9• Consist of ~ 12 layers streamer tube or RP

C• 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

The Plastic Streamer Tubes (PST)

• Larger signal pulse, good signal noise ratio Taking ALEPH detector as an exampleTypical strip signals around 6 mV (at BESIII 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

01020

3040506070

8090

100

0. 3 0. 5 0. 7 0. 9 1. 1 1. 3

Muon acceptance

Pion contamination

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.

Superconducting Solenoid Magnet

BESIII Workshop Zian Zhu Beijing, Oct.13,2001

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.

Magnetic Field Design

B along Z axis (B0=1T, Poisson method)

Luminosity MonitorBecause 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 ?

LUM Type I Extremely Forward Luminosity Monitor

• The Defining and Complimentary Counter

Dimension of θ : Scintillation fiber or Silicon Strips Dimension of φ : Plastic scintillator• The Calorimeter BGO / PWO Crystal

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.

The photo-diode Hamamstsu S3584-09 will be coupled through the air light guide and concave mirror to the GSO like the Belle design

Interaction RegionIt 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

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, …

Trigger1. 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, 11033, 200 times as current event rate, to be 1500 Hz

• Cosmic ray background can almost be negligibleTotal peak trigger rate can be more than 3000 Hz, additional trigger (software) is needed to reduce the event rate to 2000Hz.

The principle of BESIII trigger(2)• 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

Detector

switch

BESIII FEE pipeline and Data flow

Level 1FEEpipeline

Readoutbuffer

Farms

Disk

Time Reference

0 s

2.4s

Ev.Filter

Glo

bal T

rigge

r Log

ic

2.4 s

Schematic of BES III Trigger

VC

TOF

MDC

EMC

MU

DISC

DISC

DISC

Mu trackDISC

BTE Sum

Hit Count

Track Finder

Tile Processor

Total Ener Sum

Hit/Seg Count

Track Seg. Finder

L0 trigger Logic

DAQ

RF TTC

Tile Sum

FEE

L1P

L0P

CLOCK

Data Acquisition SystemEvent builder 3000 Hz 6 K bytes ~ 20 Mb/s

Event filtering

Data storage

Run control

Online event monitor

Slow control

Switch network

Configuration and Software Structure

branch 1 branch n

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 SystemSoftware trigger. Selects events for storage

• Online System– Run environment monitoring and controlling – Experiment monitoring and controlling– Human interface

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

Substantial manpower needed for software

Total CPU 36000 MIPS

Data storage 500 Tbytes/y on tapes, 24 Tbytes/y on disks

Bandwidth for data transfer 100 Mbps

3.2 A Prototype of SAN Computing Environment of IHEP

BESIII requirements:

Rec. CPU power ofPC Farm: increased bya factor of 100

Tape Lib.:Volume:∽ 484 Tbytes/yrI/O rate:∽3.6 Tbytes/dayRAID Disk:∽ 24 Tbytes/yr

Network:GE and FC system fordata transfer ,data serverand PC Farm

Endcap DetectorTwo possible technologies can be used,

1. 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.

Subsystem BES III CLEOc

Vertex XY (m) = 50 ?

MDC

XY (m) = 130 90

P/P (0/0) = 0.8 %

0.35 %

dE/dx (0/0) = 7 % 5.7 %

BEMC

E/√E(0/0) = 2.5 % 2%

z(cm) = 0.3 cm/√E ? cm /√E

TOF T (ps) = 65 ps

counter 12 层 (?)

Magnet 1.0 tesla 1.0 tesla

BESIII – CLEOc Comparison

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.

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 R&D, 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?

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

CLEOCCLEOc 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?

Schedule• Feasibility Study Report of BEPC II has been submitted to t

he 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 installatio

n : Spring of 2005• Tuning of Machine : Beginning of 2006• BESIII detector moved to beam line, May 2006• Machine-detector tunning, Machine-detector tunning, test run at end of 2006test run at end of 2006

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.

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