BESIII Collaboration Meeting Summary Fred Harris June 6, 2002 IHEP, Beijing 1

Before I begin I want to thank all the speakers and organizers for their hard work and hospitality. I think this meeting has been very useful.

Outline 1. Physics 2. Progress 3. Relationship to CLEOc 4. Issues 5. 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 glueballs, 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

For much more physics motivation see talks by: 1.) Li Weiguo 2.) Wang Yifan 3.) Zhao Zhengguo But forget about discovery of ’ c

Progress since last workshop Machine: Machine parameters decided. Preliminary design is nearly finished. R&D of key systems in progress. Passed SLAC review (May 13-15). Detector BESIII: Decision on EM calorimeter: CsI crystals Detector parameters decided Preliminary design in good progress R&D of key systems in progress: SC magnet …

Major Upgrades in BESIII Superconducting magnet Calorimeter: Cs I with E/E ~ 3 % @ 1GeV MDC IV: with small cells, Al wires, and He gas Time-of-flight : T ~ 80 ps Muon detector New trigger and DAQ system New readout electronics

BESIII Detector

MDC structure design.

TOF Radius 81cm: 1.0GeV/c K/ time difference is only ~280ps Two layers, two independent times Two options: TOF+TOF TOF+CCT Our radius .. To get so high time resolution, the barrel TOF will be made up of two layers and each layer can give a independent time measurement. Here two options are considered: one is double TOF, the other is one layer of TOF and one layer of CCT(Cherenkov Correlated Timing Detector). .

Comparison of K/ sep. TOF+TOF TOF+CCT Fig. K / separation for Double TOF Fig. K / separation for TOF+CCT This is the comparison of K/pi separation for Double TOF or TOF plus CCT. If one layer of TOF time resolution is 100ps and one lyer of CCT time resolution is 120ps, Double TOF’s K/pi separation is to 1.0 GeV. While for the TOF plus CCT detector, the limit is over 1.1GeV.

Figure 5 Configuration of the electromagnetic calorimeter 3. Structure of EMC Figure 5 Configuration of the electromagnetic calorimeter

Figure 1. Effect of electronics noise on the energy resolution from Monte Carlo simulation.γrays pass through MDC and TOF. Energy is obtained by the sum of 3 x 3 CsI(Tl) crystals, and the sum of direct energy deposit in photodiodes with a factor of 40.

MUON Outmost subsystem Main function: Measure the muons of the end particles produced during reaction. Identify muons from hadrons (especially pions).

The RPC Structure (4) The two layers of RPC and one layer of aluminum pickup strip between the two layers of absorbing iron constitute a superlayer

Monte Carlo Simulation (5) The contamination of muon by pion will be increased, but to a very limited level. In the high momentum range, the contamination of muon by pion has no difference

The Expected Performance (2) Muon separation efficiency and contamination from pion versus momentum

Comments from Ian Shipsey Happy about our decision to use CsI. Worried about our PID. To improve on D mixing limits that CLEO-c will set will require K -  misidentification at high momentum below the 10^-3 level. Encourages us to pursue CCT - far simpler than RICH. We should continue to discuss ways to collaborate.

Important to compare BESIII with CLEOc and B Factories See talk by Zhengguo Should add in proposal We will be asked anyway

The detector of BESIII and CLEOc 1.0 tesla option 1 0.4 tesla option 2 magnet ---- 9- 10 layers m counter Rich T (ps) = 80 ps Double TOF 2.0% 0.3 cm / E  E/E(0/0) = 3 %(1 GeV) z(cm) = 0.3cm/ E EMC 6% dE/dx (0/0) = 7 % 0.5 % P/P (0/0) = 0.5 %(1 GeV) @1T 1.25 %(1 GeV) @0.4T MDC 90 m XY (m) = 130 CLEOc BES III Sub-detector

Why CLEOC in B Factory Era Some important measurements at B’s are limited by systematical uncertainty CLEOC enjoys threshold production, large production cross section, low multiplicity, low BG, high S/B. But limited by statistics

Why BESIII in CLEOC Era? BESIII BEPCII CESRC CLEOC: 2003: y(3770) -- 3 fb-1; 30 M 2004: 4100 -- 3 fb-1; 1.5M DsDs 2005: y(3100) -- 1 fb-1; 1 Billion J/y BESIII

Why BESIII in CLEOC Era? Three years CLEOC program does not cover all the interesting physics in c energy region - 2-3 GeV, 2-3% R scan in 2-5 GeV - physics of  and (2S) - Charmed baryon X Need higher statistics for searches (glueball, exotica), rare decay, D0-D0bar mixing, CP and further improve the precision measurements. New discoveries need to be confirmed or continued. New type of matters, need high statistics to study it’s properties.

Is BESIII Worth Doing? YES if L~1033 cm-2s-1 and BESIII is competitive to CLEC, and the commissioning is not too late Otherwise NOT really

Interesting Schedule of CLEOC/BESIII CLEOC phys. run ? BESII BESIII Construction Engineer & phys. run MARKIII CLEOC/CESRC: Wisely seizes the great opportunity; perfectly fills the gap in the frontier of weak and strong interactions BESIII/BEPCII: Natural extension. Will be a unique frontier of c physics for a decade after CLEOC.

Typical Peak Luminosity of CESR-C, BEPC and BEPCII (1/1030 cm-2s-1) L(BEPCII)  3 L(CESR-C)  50L(BEPC)

BESIII Collaboration Beijing University Budker Institute of Nuclear Physics University of Hawaii IHEP Nanjing University National Central University (Taiwan) Shandong University University of Science and Technology University of Tokyo Tsinghua University University of Washington

Important Tasks Check detector design. Make suggestions. Think about organizational structure: Institutional Board Executive Board Subdetector groups Spokespersons Think about your contribution. How to meet? How often? Set up communication: web, email lists, tech. notes, video conferencing.

Issues Cs I crystal length Magnet choice TOF + CCT? Do K longs in mu counter? Measure more than one coordinate in mu counter? Manpower Schedule Money

Concerns and Comments To achieve high precision, need excellent detector to reduce systematic errors. We must compare to CLEOc and B-factory experiments. Compare on key channels – those where BESIII has an advantage over B - factories. 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.

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 has made much progress. Need to optimize! Prepare for review in Sept. Then let’s go. Thanks