Tau – Charm Summary Frederick A. Harris June. 16, 2006 Workshop on US/PRC Cooperation in HEP

Workshop – Tau Charm § There were many very and very useful presentations. I will not try to summarize all of them. Many thanks to all the authors. § I will only make some general comments. BEPCII/BESIII Status: Approved and under construction; commissioning There has been tremendous progress. See overview talk by Li Weiguo and other more detailed talks. Design luminosity = 1 x cm -2 s -1

Changing face of BESIII

BEPCII linac installation complete(new electron gun; new position source; new rf power (klystrons and modulators); and others. Most design specifications reached at 1 st test run. Linac

Two thirds of storage ring magnets have been installed

BESIII Detector Be beam pipe SC magnet Muon Counter Drift Chamber CsI(Tl) calorimeter TOF

Detector

ResonanceEnergy(GeV)Peak Lum. (10 33 cm -2 s -1 ) Physics Cross Section (nb) Nevents/yr J/   10 9   10 6  (2S)  10 9 D 0 D 0 bar  10 6 D+D-D+D  10 6 DsDs  10 6 DsDs  10 6 Average Lum: L = 0.5×Peak Lum.; data taking time: T = 10 7 s/year N event /year =  exp  L  T Year Event Production Huge J/  and  (2S) samples at BESIII Design luminosity = 1 x cm -2 s -1

Physics: Importance of tau – charm region Tremendous variety: taus at threshold, R, charm, charmonium, transition region between perturbative and non-perturbative QCD, etc. Many new particles: X, Y, Z, etc. Hybrids? Glueballs?  (3770) charm threshold

§ Still much interest in this physics. § Good turn out at Charm06, held June 5-7. l 64 registered participants, more than 100 attendees. l 47 from abroad and 20 from United States. l about 50 talks given. § Much also being done at B factories and elsewhere. § EXAMPLES: Tau – charm physics

Radiative  decay is the ideal glueball hunting ground!

From Jim Napolitano But CLEOc will not produce enough events to study quantum correlations.

BESIII Upgrades § Particle ID. Need R&D on improved PID for pi/K separation. Important for D D-bar mixing. See: l Alan Schwartz “Particle upgrade plans for Super Belle”. l Yeukun Heng “PID upgrade of BESIII”. § Need beam energy measurement.

1.0 T magnet layers  counter Rich  T (ps) = /layer Double layer TOF 2.0% 0.3 cm /  E  E/  E( 0 / 0 ) = 2.5 %(1 GeV)  z (cm) = 0.5cm/  E EMC 6%  dE/dx ( 0 / 0 ) = % 0.5 %  P/P ( 0 / 0 ) = 0.5 %(1 GeV) MDC 90  m  XY (  m) = 130 CLEOcBES IIIDetector BESIII and CLEOc comparison

Tau mass measurement Novosibirsk performing a new tau mass measurement. (see “tau and psi mass measurement at KEDR”, talk at “e + e - collisions from phi to psi”, Feb. 28 – Mar. 2, Novosibirsk, Russia) Resonant depolarization Previously measured J/  and  (2S) masses. Very preliminary result: BES Goal δ(m) = 0.15 to 0.20 MeV/c 2 This will be an important measurement for BESIII. Must reduce systematic error.

Workshop on Future PRC/US Cooperation in High Energy Physics Alex Bondar 13 June 2006 Beam Energy Calibration Absolute Beam Energy Calibration at Novosibirsk Alex Bondar, Budker Institute of Nuclear Physics, Novosibirsk, Russia Motivation: Precise mass measurement of the  -lepton D 0,D +,D s -mesons

Workshop on Future PRC/US Cooperation in High Energy Physics Alex Bondar 13 June 2006 Beam Energy Calibration

Workshop on Future PRC/US Cooperation in High Energy Physics Alex Bondar 13 June 2006 Beam Energy Calibration

Workshop on Future PRC/US Cooperation in High Energy Physics Alex Bondar 13 June 2006 Beam Energy Calibration

KEDR Collab., depolarization method: Single energy scale at level of 0.8 keV, or 10 –4 MeV Total systematic error at level of 9 keV, or 10 – 3 MeV Absolute calibration of energy scale Fix, stable, regular, eliminate and controllable UNSTABLE and IRREGULAR, uncontrollable BESI:  E=0.2MeV Bottleneck Mo Xiaohu Slides

 Statistical and systematic uncertainties have been studied based on BESI performance experience.  Monte Carlo simulation and sampling technique are adopted to obtain optimal data taking point for high accurate  mass measurement. We found:  optimal position is located at large derivative of cross section near threshold ;  one point is enough, and 45 pb –1 is sufficient for accuracy up to 0.1 MeV.  Many factors have been taken into account to estimate possible systematic uncertainties, the total relative error is at the level of 1.3  10 – 5. However the absolute calibration of energy scale may be a key issue for further improvement of accuracy of  mass. Summary Thanks!

Other Topics to prepare for: (Besides R, tau, charm, and charmonium) § ISR Physics – Nice talk from Genia Solodov. § 2 gamma physics

Physics: Yellow Book Write a yellow book on BESIII physics: a summary of theoretical and experimental tau-charm physics and the BESIII physics reach. ook/book/book.html ook/book/book.html Organized by Li Haibo. Contributors include D. Asner and I. Bigi. Questions to answer: –Physics opportunities relative to other experiments? –Priorities? –Time Scale? Charm2006: Workshop on Tau-Charm Physics June 5 – 7, 2006, Beijing, China

Workshop Proposed by TD to encourage collaboration with US. Many CLEOc people attended CHARM06 and left! Met with them during Charm06 and started dialogue. Other interested parties attended this workshop. Workshop a success in beginning discussions between interested groups and BES. But need a further meeting with BES, interested groups, and DOE and NSF. Workshop a great success. Many thanks to Fred Gilman and Chen Hesheng for organizing the workshop,to DOE, NSF, and CAS for sponsoring it, and to IHEP for hosting it.

Thanks