SuperB and SuperKEKB * Y. Ohnishi KEK July 3, 2008 * SuperKEKB is the KEKB upgrade in the framework of the KEK roadmap 1

Collaboration of INFN-KEK SuperB (INFN Super B(Flavor)-Factory) – Beam-beam issues (simulation work) – Lattice issues (dynamic aperture, IR design) – Coherent synchrotron radiation(CSR) calculations Crab waist study at DA  NE – Commissioning of machine – Beam-beam issues (simulation work) – Optics calculations (dynamic aperture) – (Electron-cloud issues) 2

SuperB Accelerator CDR Contributors M. E. Biagini, M. Boscolo, A. Drago, S. Guiducci, M. Preger, P. Raimondi, S. Tomassini, C. Vaccarezza, M. Zobov (INFN/LNF, Italy) Y. Cai, A. Fisher, S. Heifets, A. Novokhatski, M.T. Pivi, J. Seeman, M. Sullivan, U. Wienands (SLAC, US) T. Agoh, K. Ohmi, Y. Ohnishi (KEK, Japan) I. Koop, S. Nikitin, E. Levichev, P. Piminov, D. Shatilov (BINP, Russia) A. Wolski (Liverpool University, UK) M. Venturini (LBNL, US) S. Bettoni (CERN, Switzerland) A. Variola (LAL/Orsay, France) E. Paoloni, G. Marchiori (Pisa University, Italy) from M. Biagini, SuperB 2008 meeting 3

Comparison of Machine Parameters symbol SuperBSuperKEKB unit E GeV C km I A nbnb N/bunch x10 10 xx nm  y/  x % x*x* mm y*y* mm zz 53 x*x* 4830 to 0 mrad xx yy RF Power 1764 MW L x10 35 cm -2 s -1 4

Two Approaches 5 (hourglass) (crab waist) (crab crossing) SuperB SuperKEKB with keeping N + N - n b Beam currents Attractive !  and   are reachable ! Huge power consumption. HOM/CSR No evident for tiny  and  .

Issues for SuperB Ultra-low emittance – 10 times smaller than the present KEKB – Small machine errors and good control of beam orbits – How to handle Bunch-by-Bunch feedback system ? Ultra-low beta at IP – 10 times smaller than the present KEKB – Short focal length generates a large chromatic effect – In order to compensate this, strong sextupoles are needed. – Strong sextupoles reduce dynamic aperture....short lifetime. Crab waist scheme – Dynamic aperture (Touscheck lifetime/injection or BG) Dynamic aperture deteriorates to be about half if the crab waist scheme is applied to the KEKB lattice (results from simulations). 6

Issues for SuperB (cont’d) Polarization of electron beam – longitudinal polarization ~80 %. – Need polarized rf gun in linac injector. – Extremely strong spin rotators and/or geometrical matching are needed. Are there any realistic solutions ? Flavor factory – Energy should go down for tau-charm physics. – Quality of magnetic field for bends, quads ? – XY-coupling is designed for a fixed energy in general. XY-coupling should be zero at IP. Machine tuning becomes very difficult unless a detector solenoid changes proportonl to the energy. 7

SPARX 1 st stage SuperB LINAC SPARX future SuperB footprint on Tor Vergata site 600 m 500 m S. Tomassini’s talk, Monday New tunnel ! New linac injector ! New infrastructures ! cooling system AC power station New buildings for many power supplies, klystrons! New tunnel ! New linac injector ! New infrastructures ! cooling system AC power station New buildings for many power supplies, klystrons!

Issues for SuperKEKB Ultra-high currents – a factor of 5 larger than the present KEKB – Strong synchrtron radiation – HOM heating – Can a bunch-by-bunch feedback system work ? – Electron-cloud in a positron ring ? Large beam-beam tune shift – a factor of 3 larger than the resent KEKB – Beam size in the vicinity of IP becomes large due to dynamic emittance and dynamic beta. – Difficulties in the IR design. Physical aperture and syncrtron radiation from IR magnets affect detector backgrounds. 9

Issues for SuperKEKB Short bunch length – half of the present KEKB – HOM heating – CSR instabilities Smaller beam pipe can suppress CSR. Down from  96 to  mm bunch length can suppress CSR. Luminosity deteriorates by 16%. Crab crossing scheme – Development of crab cavities for the ultra-high current LER: 9.4 A – Is large beam-beam tune shift feasible ?  y ~ No polarization scheme 10

11 KEKB on KEK Site Mt. Tsukuba

Question ? 12 ILC Damping Ring + ILC FF = SuperB ? ILC Damping Ring realizes small emittance, however NO IP and NO BEAM-BEAM ! ILC FF realizes small beta at IP, however colliding beams are SINGLE-PASS !

IR design for SuperB and SuperKEKB 13 HER 7 GeV HER 8 GeV LER 3.5 GeV LER 4 GeV ? LER 4 GeV ? No detector solenoid No compensation solenoid Symmetric layout although asymmetric collider ! SuperB SuperKEKB Bz (T) 1.5 T e- e+ Beta    Bz (T) These are not latest version.

Crab waist study at DA  NE 2 people from KEKB visited DA  NE and joined commissioning in March We have a plan to send one or two people from KEKB for Autumn run to study the crab waist. We are very interested in a specific luminosity as a function of bunch current products between the crab sextupoles ON and OFF. – Both simulations and experimental data 14

SIDDHARTA K monitor Bhabha calorimeter  monitor IP LAYOUT AND LUMINOSITY MONITORS GEM Bhabha Monitor

SIDDHARTA K monitor Bhabha calorimeter  monitor IP LAYOUT AND LUMINOSITY MONITORS

CRAB SEXTUPOLES WORK !! e - sextupoles off e - sextupoles on Transverse beam sizes at Synchrotron Light Monitors LUMINOMETERS Sextupoles can change beta, XY-coupling, dispersion, namely beam size at IP. Quantitative evaluation ? from P. Raimondi

DA  NE Machine Parameters 18 KLOE Achieved Siddharta Design Siddharta Achieved IbIb mA nbnb xx nm y/xy/x % x*x* cm y*y* cm zz mm  x / mrad xx yy L 1.5> 52.6 x10 32 cm -2 s -1 Specific luminosity is still lower than the target for the crab waist. Smaller beta than KLOE ! E b = 500 MeV C ~ 100 m

Conclusions INFN SuperB is very attractive. – Smaller currents can get larger luminosity (above ). – a future generation for factory machine...Need more study. We keep the present design concept for the KEKB upgrade unless we obtain a good result of the crab waist at DA  NE. The KEKB upgrade is a natual extension of the present KEKB. We do not have to build the collider in a whole- new way. We have many resources and experiences for the high current scheme. We have studied the design of SuperKEKB since 2001 and already published LoI 2004 (corresponds to SuperB CDR). 19

20 5 years A. Suzuki SuperKEKB fits in with KEK roadmap !

Backup Slides 21

Geometric luminosity gain low vertical tune shift Geometric luminosity gain Very low horizontal tune shift No parasitic collisions short overlap region Crab waist transformation (realized with two  in x and 1.5  in y from IP) Geometric luminosity gain Suppression of X-Y betatron and synchrobetatron resonances Large Piwinski angle  P=  z /  x small  y * (  y *  x /  )

DA  NE (KLOE run) DA  NE Upgrade I bunch (mA)13 N bunch 110  y * (cm)  x * (cm)  y * (  m) 72.6  x * (  m)  z (mm) 2520 Horizontal tune shift Vertical tune shift  cross (mrad) (half)  Piwinski L (cm -2 s -1 )1.5x10 32 >5x10 32 DA  NE (KLOE run) DA  NE Upgrade BEAM AND NEW PARAMETERS

Old layout New layout splitters removed new vacuum IP Bending angles changed, new independent power supplies Crab sextupoles X X

Aluminum Window thickness 0.3 mm IP 5.5cm

Time schedule is restricted. Baseline is “HIGH current scheme”. Alternative is low beta+low emittance+crab waist scheme

Luminosity upgrade Luminosity gain and upgrade items (preliminary) ItemGainPurpose beam pipex 1.5 high current, short bunch, electron cloud IR( * x/y =20 cm/ 3mm) x 1.5small beam size at IP low emittance(12 nm)  x → 0.5 x 1.3 mitigate nonlinear effects with beam-beam crab crossingx 2 mitigate nonlinear effects with beam-beam RF/infrastructurex 3high current DR/e + sourcex 1.5 low  * injection, improve e + injection charge switchx ?electron cloud, lower e + current 3 years shutdown 27 KEK roadmap

operation time : 240 days/year Target for roadmap Target for roadmap Integrate luminosity (ab -1 ) Peak luminosity (cm -2 s -1 ) Year 3 years shutdown Damping Ring RF upgrade KEK roadmap Peak current (A) KEK roadmap includes RF/DR (after 3 years shutdown) Projected Luminosity (preliminary) 28

SuperKEKB I bunch (LER) = 1.87 mA I bunch (HER) = 0.82 mA Specific luminosity with crab crossing Beam-beam simulation (strong-strong)

Specific Luminosity Crab crossing 49-sp  x*=80, 84cm  x=18, 24 nm 3.5-sp  x*=80cm 3.06-sp  x*=80cm 3.06-sp  x*=90cm 22 mrad crossing y=-16.35x Green Ratio=100% Green line  y ~0.093 (HER) (4/3)

31  x * = 0.8m  x * = 1.5m  = 1%  x * = 1.5m  = 1.3% w/o crab  x * = 0.8m Machine study  x * = 1.5m