New Ideas for a Super B Factory
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Transcript of New Ideas for a Super B Factory
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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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