1. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 CHARMONIUM AT Agnes Lundborg Uppsala University Sweden

2. Background We thought that we understood charmonium quite well. Positronium of QCD, medium heavy quarks, potential model, narrow states. Perfect laboratory! In the last few years the B-factories and CLEO-c have been making unexpected discoveries. BESIII is coming up. E835 and Crystal Barrel are done. PANDA as next generation (2011) What, why and how can PANDA do better? CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Charmonium spectrum potential models vs.data dashed: nonrel (left), Godfrey-Isgur (right)

3. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Formation The two particles fuse into the intermediate state. Proton-antiproton versus electron-positron Production The state is reached through decays or nonresonant production.

4. 35003520 MeV3510 CBall ev./2 MeV 100 E CM CBall 1000 E 835 ev./pb  c1 E835 CBall, Edwards et al. PRL 48 (1982) 70 E835, Ambrogiani et al., PRD 62 (2000) 052002 CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Typical resolution in production Crystall Ball e+e- Resolution of nonvector charmonium depends on the detector. B-factories and other current e+e- experiments (BES, CLEO-c) Typical resolution in formation Proton-antiproton E835 Energy spread in beam

5. E CM CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Discovery in production and precision measurement in scanning. Important for: cross section shape measurements Precision measurements on mass and widths both at resonance-energies and two-meson thresholds. Resonance shape (Breit Wigner?) Beam momentum profile Measured cross section Scanning mode

6. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Storage ring for p High density target pellet,cluster jet, wire High luminosity mode stochastic cooling High precision mode Electron cooling to 8 GeV HESR at FAIR High Energy Storage Ring

7. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Calculation flux-tubemodel, latticeQCD, bag-model, constituent gluonmodel. Observations in the light quark sector: Exotic qn. 1-+ Hybrid? Difficult to identify in the light quark sector, many overlapping states which mix. Charmonium energy region Light quark form a structureless continuum with few heavier states on top. A spin exotic can be seen in production but not formation and would then immediately be identified as interesting. Model independently! Without a complicated formalism! QCD conceptually allows for states where gluons contribute to the quantum numbers

8. Nonrelativistic decay: charmquarks stay as they are. Gluonic excitation goes into a light scalar. Production mode JPC=1-+ CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Lowest energy charmonium hybrid (spin-exotic) [C.Bernard, Phys.Rev. D56 (1997) 7039] [F.E. Close, Phys. Rev. 1998] [P.R. Page, Acta Phys. Polon. 1998] [P. Page, Phys Lett.B402(1997)] [UKQCD, McNeile, Phys. Rev. D56(2002)] Good experimental tag! Final state: 7 photons! 1 lepton pair! We need: 1 Excellent calorimeter with full angular range coverage. A possible exotic charmonium hybrid channel:

9. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 We need an excellent: Electromagnetic Calorimeter (EMC) Almost -acceptance barrel plus endcaps Compact material (PWO, BGO) Granularity (Molière radius) Low threshold tens of MeV Readout inside magnetic field: APD Also high energy photons GeV 22 radiation lengths of crystal Timing 1 ns – triggering And high count rate (10 annihilations per s) Radiation hardness (less radiation than CMS) Last thing to solve: High resolution requires a large light output!

10. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Cooperation with manufacturers in Bogoroditsk and Shanghai working with doping and crystal growth processes has produced better crystals. Third generation PWO with much larger light yields and therefore better resolution. But that is not enough! Cooling gives overall good performance. Already at acceptable resolutions! Panda becomes a Polarbear

11. Complicated QCD process! Only theoretical guideline PCAC for only one channel. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Charmonium production

12. Use experimental data We know this decay width… It’s a kinematical extrapolation, not very far.. [A.Lundborg, T.Barnes, U. Wiedner PRD73 (2006) 096003.] Integrate Width proportional to Dalitz area We want to know this cross section. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006

13. Constant amplitude? First estimates. Cross section in the order between 10 pb to 1 nb 200 to 20 000 events per day. Background 10 000 000 events per second. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Results

14. Technical Progress Report simulations All neutral channel No significant structures or regions of poor efficiency for the calorimeter setup. Charmed hybrid – red curve 7 photons, 2 oppositely charged tracks Mass window cuts on the intermediate particles. Gives 12% detection efficiency. Any possible background would includes a and many photons. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006

15. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Signal Background [E835, PLB 566 (2003) 45-50] Measured at E835 about 50 pb in the region Major background sources [E835, PRD 56, 5 (1997) 2509(23)] Event selection Exactly two neutral tracks. No charged tracks. No pion candidates Invariant mass energy window Momentum of candidate <0.4 GeV/c Opening angle >178.5 Momentum angle o

16. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 PANDA Identification and tracking of: MVD Cherenkovs and TOF Muon chamber Trackers and B-fields EMC

17. Micro vertex detector Displaced vertices of open charm and strangeness Build on ALICE, ATLAS and CMS experience with hybrid detectors. Silicon pixel (3 layers) and strips (2 layers) 7.2 million barrel pixels, 2 million forward pixels R&D: Requirements on pixel size and orientation. Investigate photon conversions (cooling system, electronics, detector). CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 14cm

18. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Time projection chamber +Low material budget. +dEdx particle ID. High rates events per second ->Ungated TPC -Space charge from ions -Overlaying events requires very good resolution for disentangling +GEM-foils (Gas electron multiplier) Central tracking – two alternatives 2 T axial B-field, same space, forward direction MWPCs. Straw tube tracker 10000 straws Z-coordinate from either: -Skew angle 7-15 mm -Charge sharing 3 mm -Maximum material +Handles rates and has no space charge problem 74 cm TPC prototype in Munich

19. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 To conclude: Panda will provide the next generation of charmonium knowledge! Precision – state of the art detectors, formation versus production. Rates – pellet target, beam. Proton-antiproton. Scope - detection of charged and neutral particles over (almost) full phase space Charmonium energy region Charmonium Charmonium hybrids Glueballs DD-thresholds Meson molecules Other topics: hypernuclei, drell-Yan, charm in nuclei, di-baryons, crossed channel compton scattering. Hardware R&D, software optimization and civil construction on-going. Beam-on in: (Maybe) 2011

20. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 PANDA 2006: 300 people, 15 countries, 46 institutes Technical Progress Report in february 2005 timelines, plans, simulations, technical solutions and R&D-work. [PANDA technical progress report http://www-panda.gsi.de]

21. CHARMONIUM AT Agnes Lundborg QWG workshop Brookhaven June 2006 Accessible physics