1. 1 BINP Tau-Charm Project 3 February 2010, KEK, Tsukuba E.Levichev For the BINP C-Tau team

2. 2 Outline 1. Introduction of Crab Waist collision approach 2. Scientific program and specifications 3. Optics 4. FF and QD0 5. Polarization insertions 6. Energy calibration

3. 3 1.Large Piwinski’s angle  = tg(  z /  x 2.Vertical beta comparable with overlap area  y  x /  3.Crab waist transformation y = xy’/(2  ) Crab Waist in 3 Steps 1. P.Raimondi, 2° SuperB Workshop, March 2006 2. P.Raimondi, D.Shatilov, M.Zobov, physics/0702033 M.Zobov, Tau08, Novosibirsk

4. 4 Crabbed Waist Scheme Sextupole (Anti)sextupole Sextupole strength Equivalent Hamiltonian IP M.Zobov, Tau08, Novosibirsk

5. 5 Collisions with and without Crab Sextupoles 1.Bigger blowup 2.Sharp lifetime reduction for bunch currents > 8 -10 mA February 2009 Courtesy G. Mazzitelli

6. 6 Frequency Map Analysis for CW

7. 7 Scientific case for the BINP C-tau project ► D-Dbar mixing ► CP violation searches in charm decays ► Rare and forbidden charm decays ► Standard Model tests in  leptons decays ► Searches for lepton flavor violation  →  ► CP/T violation searches in  leptons decays ► Production of the polarized anti-nucleons E = 1 GeV (may be with reduced luminosity) Requirements: L > 10 34 cm -2 s -1, longitudinal polarization, beam energy range from 1 GeV to 2.5 GeV

8. 8 Specifications ► Variable energy E cm = 2 – 5 GeV ► Luminosity L = 1÷2×10 35 cm -2 s -1 ► Electrons are polarized longitudinally at IP ► No energy asymmetry ► No beam monochromatization ► Energy calibration with medium accuracy is sufficient (Compton backscattering)

9. 9 Facility key features and principles ► Two rings with a single interaction point ► Crab waist collision ► SC wigglers to keep the same damping and emittance in the whole energy range (optimal luminosity) ► Polarized e- injector and spin control to get the longitudinally polarized electron beam at IP ► Wide re-using of the existing structures and facilities to save the cost

10. 10 Layout Injection facility exists Tunnel for the linac and the technical straight section of the factory is ready

11. 11 Main ring

12. 12 Main ring: tunnel Ready-built tunnel FF region Technical reg. (RF and injection) Damping wiggler sections

13. 13 Main accelerator parameters 6 m of the SC wigglers with 20-cm-period are used to control the beam parameters at different energies Energy1.0 GeV1.5 GeV2.0 GeV2.5 GeV Circumference783 m Emittance hor/ver10 nm/0.05 nm @ 0.5% coupling Damping time hor/ver/long30/30/15 ms Bunch length20 mm13 mm10 mm Energy spread10.5·10 -4 10.4·10 -4 8.8·10 -4 7.6·10 -4 Energy loss/turn174 keV261 keV349 keV430 keV Momentum compaction1.00·10 -3 1.06·10 -3 Synchrotron tune0.0130.0140.0120.010 Wiggler field5.4 T4.0 T2.8 T0 RF frequency500 MHz Harmonic number1260 Particles/bunch7·10 10 Number of bunches294 Bunch current4.3 mA Total beam current1.3 A Beam-beam parameter0.15 0.12 Luminosity0.55·10 35 0.81·10 35 1.08·10 35

14. 14 Main ring: arc cell FODO but close to the theoretical minimum emittance   x,  y

15. 15 Main ring: injection section  x,  y

16. 16 IR optics L 1/2 = 75 m  x,  y IP FF telescope Y Section of chroms correction X Section of chroms correction Crab Sext End of the telescope

17. 17 Luminosity D.Shatilov Crab ON: ξy=0.13 L beam =2.76·10 32 @ Np=7·10 10 Lmax=1.05·10 35 @ Nb=380 Crab OFF: ξy=0.06 L beam =4.94·10 31 @ Np=3·10 10 Lmax=0.44·10 35 @ Nb=890  y =750 um, Θ=50, mrad, σ z =1cm,  x =10 nm·rad, 0.5% coupling

18. 18 Polarization scheme IP snake1 snake2 snake3 damping wiggler1 damping wiggler2 Polarization scheme with 3 snakes (arc=120 0 +2 damping wigglers in the arc’s middle )

19. 19 Polarization vs energy 5 snakes 1 snake 3 snakes

20. 20 QD0 SC iron yoke twin aperture magnet Excitation current 1150 A Single aperture 2 cm Gradient 150 T/m

21. 21 Damping wigglers Field amplitude at 1.0 GeV 5.4 T Period length 0.2 m Total length 8 m Damping integral i 2 at 1.0 GeV 12.4 m -1 Excitation integral i 5 at 1.0 GeV 0.08 m -1 The damping wigglers keep the damping time  x =30 ms and the horizontal emittance ( ε x =10 nm) in the energy range 1.0 – 2.5 GeV Wiggler field amplitude vs energy Wiggler with similar parameters produced by BINP

22. 22 Energy calibration Compton backscattering E calibration (~10 -4  10 -5 ) Spectrum edge Na 24 (1)=1368.625 keV Na 24 (2)=2754.008 keV Na 24 (1+2)=4122.633 keV

23. 23 Injection facility

24. 24 Injection facility upgrade Today: 2  10 10 e - /pulse  (1.5% conversion)  3  10 8 e + /pulse  50 Hz = 1.5  10 10 e + /s Upgrade: e - current increase (  3) Better focusing in positron linac (  1.5) Debuncher usage (  2) = 1.35  10 11 e + /s Reserve: electron energy can be increased by 100 MeV (  1.3)

25. 25 Summary ► Crab Waist collision seems a very promising idea to enhance a circular colliders luminosity beyond the present value by factor of 10- 100 without current increase. ► CW approach was successfully proved experimentally at DAFNE in the end of 2008 ► Novosibirsk SuperCT project is under way. The key issues like IR design, DA optimization, polarization scheme, QD0 design, etc. seem solved successfully ► In 2010 we hope to finish a CDR and in parallel apply for funding to Russian Government.