Super B Overview P Raimondi for the Super

Super. B Overview P. Raimondi for the Super. B Team Super. B IRC Meeting Frascati, Nov. 13 th 2007

Basic concepts • B-Factories (PEP-II and KEKB) reach already very high luminosity (~10 34 s-1 cm-2 ). To increase of ~ two orders of magnitude (ex. Super. Ke. KB) it is possible to extrapolate the requirements from the current machines: Parameters : • Higher currents • Smaller damping time (f(exp 1/3)) • Shorter bunches • Crab collision • Higher Disruption • Higher power • Super. Ke. KB Proposal is based • on these concepts Increase of plug power ($$$$$. . ) and hard to operate (high current, short bunches) look for alternatives keeping constant the luminosity => new IP scheme: Small beams, ILC-like Large Piwinsky Angle and CRAB WAIST

Crossing angle concepts Overlapping region Sx Sz 1) Standard short bunches All colliders do need short bunches to decrease the hourglass effect and the beams disruption Both cases have the same luminosity, (2) has longer bunch and smaller sx With large crossing angle X and Z quantities are swapped: Very important!!! Overlapping region Sz 2) Crossing angle Sx

High luminosity requires: - short bunches - small vertical emittance - large horizontal size and emittance to mimimize beam-beam For a ring: - easy to achieve small horizontal emittance and horizontal size - Vertical emittance goes down with the horizontal - Hard to make short bunches Crossing angle swaps X with Z, so the high luminosity requirements are naturally met: Luminosity goes with 1/ex and is weakly dependent by sz

x b. Y e+ e- 2 Sx/q q 2 Sz*q z 2 Sx Crab waist removes bb betratron coupling Introduced by the crossing angle Vertical waist has to be a function of x: Z=0 for particles at –sx (- sx/2 q at low current) Z= sx/q for particles at + sx (sx/2 q at low current) Crab waist realized with 2 sextupoles in phase with the IP in X and at p/2 in Y

Crab Waist Advantages a) Geometric luminosity gain 1. Large Piwinski’s angle 2. b) Very low horizontal tune shift F = tg(q)sz/sx 3. 2. Vertical beta comparable 4. with overlap area by s x/ q 3. Crabbed waist transformation y = xy’/(2 q) a) Geometric luminosity gain b) Lower vertical tune shift c) Vertical tune shift decreases with oscillation amplitude d) Suppression of vertical synchro-betatron resonances a) Geometric luminosity gain b) Suppression of X-Y betatron and synchro-betatron resonances

Horizontal Plane Vertical Plane Collisions with uncompressed beams Crossing angle = 2*25 mrad Relative Emittance growth per collision about 1. 5*10 -3 eyout/eyin=1. 0015

KEKB Beams distributions at the IP Super. B Beams distributions at the IP Beams are focused in the vertical plane 100 times more than in the present factories, thanks to: - small emittances - small beta functions - large crossing angle - Crab waist Tune shifts and longitudinal overlap greatly reduced KEKB Super. B current 1. 7 A 2. A betay 6 mm 0. 3 mm betax 300 mm 20 mm sigmax ~80 mm ~6 mm sigma y ~3 mm 0, 039 mm Sigma z 6 mm L 1. 7 1034 1 1036

Parameters Optimization: Transparency condition • Due to the large crossing angle, new conditions, instead of unbalanced currents, for having equal tune shifts with asymmetric energies are possible • LER and HER beams can have different emittances and b* and equal currents

e+ sees a shorter interaction region, (4/7 of the e- one) e+ has a smaller by*, natural to acheive in the FF e+ has larger emittance, 2. 8 nm better for the lower energy beam, less toushek, better tolerance for instabilities ee+ LER sz HER sz

Beam-beam blow up weak-strong simulations Crab=0. 8 Geom_Crab=0. 9 Geom_Crab HER LER 1/e Density Contour lines L=1036 cm-2 s-1 D. Shatilov

• Beam lifetimes increased, injection rates reduced • Beam simulations shows very good results, no blow up is seen for HER, 1 -3% for LER, but some more optimization is possible: tunes, crabbing etc • L=10^36 is predicted • Upgrade parameters can be implemented in any order: - decrease the emittances first or - increase the bunch charge or - increase the number of bunches or - decrease the bunch length • Less RF Voltage is needed

Super. B Parameters (Nov. 2007) (In red the CDR values)

Possible site in the Tor Vergata University close to the Frascati Lab M. Sullivan

Super. B Luminosity Tune Scan (crab=0. 8/q, sz = 7 mm; 3 x 1010 particles) Lmax = 2. 2 x 1036 cm-2 s-1

Luminosity Tune Scan Qy 1 IP Lmin = 3. 95 x 1034 Qy cm-2 s-1 Lmax = 1. 02 x 1036 cm-2 s-1 M. Zobov, D. Shatilov Qx 2 IPs Lmin = 3. 37 x 1034 cm-2 s-1 Lmax = 1. 00 x 1036 cm-2 s-1 Qx

• The small emittance rings can be built by using all the PEP-II magnets, starting from the ILC DR design • The rings have circumference flexibility • The FF design complies all the requirements in term of high order aberrations correction, needs to be slightly modified for LER to take care of energy asymmetry • All PEP-II magnets are used, dimensions and fields are in range • RF requirements are met by the present PEP-II RF system

Dipoles Summary Lmag (m) 0. 45 5. 4 PEP HER - 194 PEP LER 194 - SBF HER - 130 SBF LER 224 18 SBF Total 224 148 Needed 30 0 Available • 130 (112 in Arcs+18 in FF) “PEP-II HER” dipoles are used in Super. B HER • 18 “PEP-II HER” dipoles are used in FF for Super. B LER • 224 “PEP-II LER” dipoles are used in Super. B LER need to build 30 new ones Super. B Magnets. Shopping list

Quadrupoles Summary Available Lmag (m) 0. 56 0. 73 0. 43 0. 7 0. 4 PEP HER 202 82 - - - PEP LER - - 353 - - SBF HER 165 108 - 2 2 SBF LER 88 108 165 2 2 SBF Total 253 216 165 4 4 Needed 51* 134 0 4 4 * Spare 0. 43 m long quadrupoles can be used (23)

All and just the Pep RF system fits the Super. B needs

Dafne Run with Crab Waist • • Machine upgrade almost completed Cold checkouts will start ‘round Nov. 20 Commissioning should last until Dec. 20 Physics run will begin in January until june -15 (goal Lint=1 fb-1) • Luminosity goal is >5 e 32 (present record is 1. 6 e 32) with crab sextupoles and >2 e 32 without

Conclusions • Super. B studies are already proving useful to the accelerators and particle physics community • We have a preliminary “Conceptual Design Report”, based on the reuse of all the Pep hardware, that might fit in one of the existing facilities, or in a new (and avalaible) site near Frascati • We hope to gather in the enterprise as many labs and institutions as possible (see the CDR for the ones already involved)

Possible fall back on the existing factories The crab waist seems to be beneficial also for the current factories Potential to simultaneously boost the performances of the existing machines and do Super. B R&D LHC Upgrade