BINP Tau-Charm Project E.Levichev For the BINP C-Tau team International Workshop on e+e- collisions from Phi to Psi (13-16 October 2009) IHEP, Beijing

Outline 1. Introduction of Crab Waist collision approach 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

Crab Waist in 3 Steps Large Piwinski’s angle F = tg(q)sz/sx Vertical beta comparable with overlap area by sx/q Crab waist transformation y = xy’/(2q) 1. P.Raimondi, 2° SuperB Workshop, March 2006 2. P.Raimondi, D.Shatilov, M.Zobov, physics/0702033 M.Zobov, Tau08, Novosibirsk

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

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

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 t→mg ► CP/T violation searches in  leptons decays ► Production of the polarized anti-nucleons E = 1 GeV (may be with reduced luminosity) Requirements: L > 1034 cm-2 s-1, longitudinal polarization, beam energy range from 1 GeV to 2.5 GeV

Specifications ► Variable energy Ecm= 2 – 5 GeV ► Luminosity L = 1÷2×1035 cm-2s-1 ► Electrons are polarized longitudinally at IP ► No energy asymmetry ► No beam monochromatization ► Energy calibration with medium accuracy is sufficient (Compton backscattering)

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

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

Main ring

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

Main accelerator parameters Energy 1.0 GeV 1.5 GeV 2.0 GeV 2.5 GeV Circumference 755.32 m Emittance hor/ver 10 nm/0.15 nm 10 nm/0.09 nm 10 nm/0.05 nm Longitudinal damping time 30 ms 15 ms Natural bunch length 10 mm Energy spread 8.5·10-4 10.5·10-4 8.8·10-4 7.4·10-4 Energy loss/turn 84 keV 251 keV 335 keV 420 keV Betatron tunes hor/ver 29.53/21.57 Momentum compaction 1.137·10-3 1.127·10-3 1.118·10-3 1.115·10-3 Synchrotron tune 0.012 0.014 0.010 Wiggler field 4.4 T 4.8 T 3.3 T RF frequency 500 MHz Harmonic number 1260 Particles/bunch 5·1010 7·1010 Number of bunches 416 312 Bunch current 3.18 mA 4.45 mA Total beam current 1.32 A 1.39 A 8 m of the SC wigglers with 20-cm-period are used to control the beam parameters at different energies

FODO but close to the theoretical minimum emittance Main ring: arc cell FODO but close to the theoretical minimum emittance  bx, by

Main ring: injection section bx, by

IR optics bx, by L1/2 = 85 m

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

Luminosity D.Shatilov y=760 mm, Θ=34, mrad, σz=1cm, x=10 nm·rad, 1% coupling

Polarization scheme At the nominal energy the magnets rotate the spin around the field direction by (2k+1), k is integer. Solenoids rotate the spin by /2 around the velocity vector: a polarization vector is longitudinal at IP and transverse outside the polarization insertion.

Polarization vs energy Longitudinal polarization degree, averaged on time and particle ensemble

Damping wigglers The damping wigglers keep the damping time tx =30 ms and the horizontal emittance (10 nm) in the energy range 1.5 – 2.5 GeV Field amplitude at 1.5 GeV 4.3 T Period length 0.2 m Total length 8 m Damping integral i2 at 1.5 GeV 2.76 m-1 Excitation integral i5 at 1.5 GeV 0.01 m-1 Wiggler with similar parameters produced by BINP Wiggler field amplitude vs energy

Na24 (1)=1368.625 keV Na24 (2)=2754.008 keV Na24 (1+2)=4122.633 keV Energy calibration Compton backscattering E calibration (~10-410-5) Na24 (1)=1368.625 keV Na24 (2)=2754.008 keV Na24 (1+2)=4122.633 keV Spectrum edge

Injection facility

Injection facility upgrade Today: 21010 e-/pulse  (1.5% conversion)  3 108 e+/pulse  50 Hz = 1.51010 e+/s Upgrade: e- current increase ( 3) Better focusing in positron linac ( 1.5) Debuncher usage ( 2) = 1.351011 e+/s Reserve: electron energy can be increased by 100 MeV ( 1.3)

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. Three projects (SuperB, SuperKEKB and BINP-SuperCT) adopt CW as a basic idea of design. ► 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 the end of 2009 we hope to prepare a CDR of the project and in 2010 clear the project funding with Russian Government. In parallel a TDR will be prepared