New Ideas for a Super B Factory

Steve Playfer

University of Edinburgh

ILC Forum, Cosener’s House, May 2006

The Current B factories

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Jul-99Jul-00Jul-01Jul-02Jul-03Jul-04Jul-05Jul-06Jul-07Jul-08

109 B meson pairs in each experiment by Autumn 2008 (1/ab)

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BaBar

BELLE

Current CKM Status

Unitarity Triangle angles and sides are all measured:

Vtd, Vcb, Vub, by BaBar and BELLE

Vts by CDF and D0

• The Standard Model triumphs again in the Heavy Flavour sector

• So why do we want to produce yet more B mesons?

• …and what has it got to do with a workshop on the International Linear Collider?

We don’t understand Flavour Physics!

• Why are there three generations?

• Why are the lepton and quark couplings different?

• Why are the Standard Model CKM parameters what they are?

• What is the flavour structure of new Physics at the Electroweak scale?– Most studies assume Minimal Flavour Violation, but this

has to be checked!

Physics Topics at SuperB

• Improve CKM constraints – angles are statistics limited

– Vub can also be improved

• Discrepancies in rare bs transitions?– sin2 in bs penguins

– AFB in bsl+l-

• Forbidden processes – D0 mixing and CP Violation

Comparison of Sin2

spectator diagrams

penguin diagrams

Penguin results are consistently lower(but never by more than 2)

“Naïve average” not reliable (different theory predictions for different decay modes)

b s

_d

u,c,t

_d

Low q2: AFB > 0.19 (95% C.L.)Standard Model: 0.03

BaBar

AFB in BK*l+l-

Belle

Low q2: AFB > 0 Standard Model fit shown

Recent activity

• CERN workshops on Flavour in the LHC era (November, February, May)

• Frascati workshops on Super B (November, March)

• Daresbury Meeting (April)

Things are evolving rapidly.

No baseline design. No version control.

I will do my best to summarize!

LHCb and SuperB are complementary!

Measurement LHCb SuperB

Phase of Vts s No

Rare Bs decays s Unlikely

Angle sDsK, KK DK

Angle Difficult bs penguins s Ks

bsl+l- BK*l+l- Inclusive

Vub No? Inclusive bul Exclusive B, c and decays with only at SuperB?

Super KEK-B

Higher beam currents

More RF cavities

Smaller * and crab crossing

Luminosity 2-5 x 1035

Integrate 20-50/ab by 2020

3-6 x 1010 B meson pairs

Proposal submitted to KEK by BELLE last year.

Linear Collider B factory

• “An electron-positron linear collider as a B-anti B Meson factory” (Amaldi & Coignet 1986)

• Idea resurrected at Hawaii Super B workshop (Pantaleo Raimondi, April 2005)

• “Super B: a linear high luminosity B factory”

(J.Albert et al, hep-physics/0512235)

Benefits from all the Linear Collider R&D that has been going on in the last 20 years.

Looks feasible to get luminosity of 1-2 x 1036 at Y(4S)

First Linear Super B scheme with accelerationand energy recovery (to reduce power)

e- Gun2GeVe+ DR IP

5GeV e+ SC Linac

e- Dump7GeV e+

4 GeV e-

4GeV e- SC Linac

2 GeV e+ injection

2 GeV Linac1.5 GeV Linac 1.5 GeV Linac

Linac

Damping Rings2 GeV

Linac

e+ Gun e- Gun

• Use Superconducting Linacs to recover energy

• Use low energy damping rings to reduce synchrotron radiation– Maybe no e- damping ring

• Use bunch compression and final focus a la ILC

• Energy and asymmetry tunable

• Polarized beams possible

Compressor

Decompressor Compressor

DeCompressor

IP

OptionalAccelerationand deceleration

OptionalAccelerationand deceleration

FF FF

ILC damping rings ILC final focusILC bunch compressorColliding every 50 turns

Acceleration optionalCrossing angle optional

Second design of Super B

Latest design has no acceleration and a crossing angle

Parameters of Super-B Designs

Collider y N y* s E F Lumin

Units 1010 mm m GeV (~Hd) 1035

PEP-II Normal 0.068 8 11 1.26 3.1 0.84 0.10

KEKB Normal 0.065 5.8 6 2.1 3.5 0.76 0.16

Super-PEP-II

High I low y

0.12 10 1.7 0.32 3.5 0.81 7

Super-KEKB

High I low y

0.28 12 3 0.59 3.5 0.76 5

Linear SuperB

Single pass

29. 10 0.5 250 4 1.07 10

SuperBBunch shorten

0.14 6 0.4 0.63 4 0.75 10

SuperBX’ing angle

0.045 2 0.08 0.5 5 0.8 9

John Seeman, FPCP 2006

Single Pass Linear Collider Scheme

• Collide each bunch once very hard and then recycle it– Vertical emittance blow up x300

• Use very small beta functions to achieve high luminosity

• Re-inject disrupted bunch into damping ring for ~6 damping times – Need very short damping time (~1ms)– High power requirement for damping ring

• Collision frequency 120Hz x 10000bunches is ~1MHz

Single pass Super B collider

Nbunches=12000 in two 6km damping rings E(e+) = 7GeV E(e-) = 4 GeV

x=30m y=10nm

z=100m z=4mm in DR

e=100MeV e/e=2*10-2 e/e=5*10-4 in DR

e_Luminosity=7MeV

x=0.8nm x_norm=8m

y=0.002nm y_norm=20pm

z=2.0m Stored time between collision = 1msec = 50turns

Luminosity (50 turns) = 0.9*1036 Luminosity better with single turn = 1.5*1036

Colliding every turn with Bunch Compression

• Install ILC like final focus in the damping rings– Room for long enough straight section or use an

arc inside the ring

• Choose a much lower disruption to avoid blowing up the bunch too much

• Use bunch compression/decompression to shorten bunches for the final focus

• Use monochromator scheme to compensate the energy spread at the IP to match the Y(4S) resonance

Comparison of Rings (Andy Wolski)SuperB ILC e-(e+) PEP-II e+ PEP-II e-

Circumference 3 km 6.7 km 2.2 km 2.2 kmBeam energy 4(7) GeV 5 GeV 3.1 GeV 9 GeVBunch charge 2×1010 1×1010 6.9×1010 4.3×1010

Nobunches 5000 5800 1588 1588Current 1.6 A 0.4(0.2) A 2.4 A 1.5 ABunch length 4 mm 6 mm 11 mm 11 mmEnergy spread 0.11% 0.13% 0.07% 0.07%Horiz. emit. 0.4 nm 0.5 nm 35 nm 60 nmVert. emit. 0.002 nm 0.002 nm 1.4 nm 1.4 nmDamping Time 10 ms 27 ms 70 ms 37 ms

Contradictory requirements at IP

• Disruption

• Luminosity

• Energy spread - important at Y(4S)!

( )yx

zN

Dσσ

σ≈

( )yx

NL

σσ

2

≈

( )zx

E

N

σσδ

2

2

≈

Decrease number of bunches

Decrease bunch length

Increase spot size

Increase number of bunches

Decrease spot size

Decrease number of bunches

Increase bunch length

Increase spot size

Most recent Ideas

• Optimum is to collide every turn • Use bunch compression/decompression• Use double rings

– First ring for damping– Second ring for compression and final focus

• Use crossing angle (2x25mrad)• Compensate disruption at IP using a travelling focus

Some of these ideas are also relevant to ILC

Some tests are planned at Frascati (DAFNE)

Large Crossing Angle Scheme

• Collide with 2x25mrad crossing angle• Only small longitudinal part of bunch gives

luminosity, but various solutions possible:– Compensate with very small vertical beta function using

an ILC type final focus – Use travelling focus in horizontal plane– Crab cavities

• In this scheme the disruption is small and strong damping is not needed.

SYNERGY BETWEEN ILC and SuperB?

“Synergy …is frequently described as the 2 + 2 = 5 effect to denote the fact that the combined performance is greater than the sum of its parts.”

Corporate Strategy, H.I.Ansoff (1965)

Synergy between PEP-II and KEK-B

If only the first of these statements is true the SuperB factory is parasitic to the ILC

The second statement is what sells SuperB to the ILC community!

Synergy between SuperB and ILCshould also be a win/win situation

• The SuperB factory will be a better machine because of the ILC

AND

• The Linear Collider will be a better machine because of SuperB

Damping RingsILC 5 GeV SuperB 4-7 GeV

Electron rings almost identical Positron rings somewhat different Same lattice Similar damping times Different sizes (3km - 6km) Different currents Different RF frequencies Similar bunch patterns Final focus inserted into rings (SuperB)

Final Focus Same bunch compression Similar IP geometry Different beam energies! CM energy resolution (SuperB) Different sources of backgrounds Different crossing angles (2-25 mrad) Different bunch trains (ILC) Different disruption parameters Different currents Final focus inserted into rings (SuperB)

Comments on Timescales• ILC construction assumed to begin

somewhere between 2010 and 2020• SuperB construction assumed to begin

somewhere between 2010 and 2014• They may be operating in sequence

and/or in parallel: – SuperB may precede the ILC– SuperB is unlikely to be after ILC

Does it help more to have SuperB before ILC, or is it the same if they are in parallel?

Comments on Sites

• SuperB and ILC at different sites– Large difference in location of damping rings?– Differences in detailed design parameters– Both need the full currents of the damping rings for

luminosity

• Frascati’s idea, and Italy is keen to host.– Need new tunnel

• There are existing 2-6 km rings– PEP, KEK, Tevatron, HERA

• ILC have plans for new damping ring test facilities

Searching for New Physics• Method I - Go to higher energies (LHC, ILC)

– Produce new particles.– Measure masses and main decay modes.

• Method II - Go to higher precision (LEP, B, ILC)– Produce lots of known particles. – Make accurate measurements of couplings– Measure rare decays.

• Method III - Look for “forbidden” things ( …)– Neutrino masses, mixing and CP violation. – Lepton flavour violation. – Electric dipole moments.

To get a complete picture we should do all of these