Download - Status of Belle Super KEKB plan
Status of BelleSuper KEKB plan
SLAC seminarMarch 21st, 2003Nobu Katayama
KEK
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Outline
§ Belle/KEKB status– General– Beam pipe accident– SVD2
§ Recent physics results § Super KEKB plan
– Physics– Detector study– Accelerator study
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KEKB status1999/102003/3/18
> 50 fb1 in a year 2002
>50 fb1 in 2002
LER>1.55AHER>1A withSRF
IP leak: Longest unscheduled shutdown Oct.30~Dec 2002
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Best day (03/17/2003)462pb1/day recorded
NK on shift!
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Beam pipe accident§ 6AM, Oct. 29, 2003:New
record:8.261033 § Oct. 30:A vacuum problem happened§ Oct. 31:A serious problem happened
– After an abort, HER beam could not be injected
– Leak check showed no leak– Resumed running (vacuum scrubbing)– But too much background to the detector– Beam aperture check: something inside?
§ Nov. 1: Opened the vacuum and inspected– No problem found
§ Nov. 5: Closed the vacuum to resume operation
§ Nov. 7: A serious leak occurred and identified– Leak is from the He cooling line of IR Be
beam pipe
Oct. 29, 2002-Nov. 8, 2002
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Structure of IP beam pipe for SVD1.410m gold by vacuum sputtering
10~30m gold by chemical plating
200~230m gold by chemical plating
Inner Surface
He
Beryllium part is cooled by Helium gas.
Aluminum part is cooled by water.
:to reduce SR BG
to reduce particle background
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Pictures using optical fiber scope
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Locating the leak§ After dismounting
the beam pipe, a leak check was performed to locate the leak point– Leak was confirmed
with a bubbling test– Bubbles were seen
on the inner gold sputtered surface of Beryllium beam pipe
– Leak is not at the joint of Be and Al
Leak
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Cutting Al part of the beam pipe
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Inner Beryllium beam pipe
Direction of Helium gas
position of leak
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Location of the leak
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Observations§ A large amount of a white powder was found
on the outer surface of the inner Beryllium cylinder and on those of Al rings– It looks like its following the flow of He gas
§ We found two types of powders– Color of one powder is clearly white– The other one looks slightly yellow
§ Thickness of the inner Beryllium cylinder was measured– No significant loss of Beryllium
§ The beam pipe was used for three months in 1999– The powder was there then although the amount
was much less
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Photo before re-assembly (1999)
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Preliminary results of element analysis
§ White powder– Main components are Be and O– Probably, it is BeO
§ Yellow powder– Main components are Al and O– Probably, it is Al2O3 and/or Al(OH)3
§ Commonly found are– Carbon– Small amounts of P, K, Ca, S, Cl, Si, Mn, Fe, and Cu were found.
§ S and Cl are dangerous elements for corrosion of Beryllium§ Si, Mn, Fe and Cu are components of Aluminum alloy
§ But, expert for element analysis says the amounts of S and Cl are small and are consistent with normal metal
§ No conclusion, yet
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Cause of corrosion§ Corrosion can occur on the Al and Be surfaces
– What caused the corrosion is not known yet§ Water, Cl or S?§ Radiation?§ Analysis of circulation gas is in progress
§ Before the accident, we had not paid attention to corrosion– Dew point had not been monitored in gas circulating syste
m– We have never analyzed impurity of the circulating gas
§ Currently, to avoid corrosion– Dew point is monitored(~20C)– An additional filter has been installed– Fresh Helium gas is added more frequently, to avoid accum
ulation of impurities (Most effective)
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Possible causes of Helium leak
§ Corrosion is most suspicious§ Heat stress caused by the temperature
difference between two walls– Resonant HOM heating during machine study– Helium circulation system troubles
§ Recycled Be pipe from BP#1 – Large stress at machining process (?)
§ Very high temperature (~300C) – When gold was spattered and the Be pipe
was welded with Aluminum sections
§ Defect of material (?)§ Still being actively investigated
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SEM photos of Be surface
Beryllium is made by sintering, from a powder of 5~40m Be particles. Some of them are missing
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History of Beam Pipe and SVD
1999
2000
2001
2002
2003
BP 1 + SVD 1
BP 2 + SVD 1.2
BP 3 + SVD 1.4
BP 2 + SVD 1.6
Summer 2003BP 4 + SVD 2!
BP3 reused BP1 Be pipe
SVD 1.4 electronics can survive up to 2M rad
SVD 1 damagedby back scatteredsynchrotron Rad
Dead wafers replaced
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BP#3(1) BP#2 BP#4cooling for
BeHe He Paraffin
Au on Be 10m inside 20m outside
10m inside
fwd/bwd Aluminum Aluminum Tantalum
Au in fwd 200m inside
20m inside no
Au in bwd 20m inside 20m inside no
Res. HOM 5 buckets 5 buckets No?
Saw tooth bwd no bwd
Material (IP) 0.6% X0 0.9% X0 0.7% X0
Particle mask
standard tolerable? better
Much better BP4!
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Daily Luminosity2002/92003/3/8
Current limit 2.4A
Old beam pipere-installed
Current limit 2.2A
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Short term plan§ 3/24~26: Belle general meeting
– Will discuss beam current limit. – LER+HER<2.6A till May?– HER 1A + LER 1.55 A is the max. in last Oct.
§ Keep running till end of June– Hope to get >150 fb1 in total– Increase LER current to 2A, then 2.6A and
see what happens
§ This summer– Install SVD2– Add last two ARES RF cavities so that HER
current can reach 1.2A
§ Operation will start from mid October
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SVD 1 SVD 2
6+12+18+18=54 ladders
8+10+14=32 ladders
SVD1 SVD2
RBP 1.5 cmRBP
2.0cm
RL1
3.0cm
RL1
2.0cm
Rout
6.0cm
Rout
8.8cm
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SVD 1.6 SVD2.0RBP / RL1 / Rout 20/30/60 mm 15/20/90 mm
Acceptance 23º<<139º 17º<<150º
# of layer/# of ladders
3 / 32 4 / 54
Max. length (mm) 220 460
Orthogonal readout Built in double metal layer
Flexible printed circuit
Isolation of detector bias
Integrated capacitor on DSSD
Optical isolator in a buffer circuit
Fast trigger No Yes
Shaping time ~1s ~0.5s
z (90deg.,p=2GeV/c) ~35m ~25m
Measured Signal to Noise ratio
~20 25(lyr4)~36(lyr1)
Radiation tolerance ~2Mrad ~20Mrad
How much improved?
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Beam pipe for SVD2
Smaller radius (1.5cm)
Better cooling with liquid
Heavier masks
Better mechanicalstructures
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ForwardBackward
L#1
L#3
L#4
L#2
DSSDDSSDhybridhybridflexflex DSSDDSSDDSSDDSSD
Ladder Ladder constructionconstruction
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Ladder mount completed on 13-Feb. 2003.
The last of the The last of the 54 ladders!54 ladders!
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Track reconstructed!
ShibataShibata
Recent physics results
Just flashing…
VubBK
BK*, K
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Fully reconstructed B mesons
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Vcb measurement with tag
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Vub measurements
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Separating two B’s
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Two inclusive Vub measurements
§ Two new tagging methods– Simulated annealing– D*l reconstruction
§ Can measure Mx distribution
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First observation of
§ Br()=(2.6+1.10.90.3)106 – M < 2.85 GeV/c2 to exclude c
§ Only penguin (b sssss) can contribute§ Asymmetry in this decay mode is sensitive to NP d
ue to interference with cK, c
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BK* angular analysis
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Projected angular distributions
We have just started!
More and more Bs
Super KEKB
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Mission 1: 300 fb1
Precision test of KM unitarity
Search for new physics in B and decays
Identify SUSY breaking mechanism
Bread’nd butterfor B factories
See quantum effect in penguin and box
loop
Very important if New physics =
SUSY
Mission 2: 3,000 fb1
Mission 3: 30,000 fb1
Mission of Super B Factory(ies)
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In which processes can we find New Physics?
§ Rare decays– B Xs,– B K*
§ CP violations– B KS and ’KS
– B Xs 、§ b c emitting charged Higgs§ Forbidden decays by SM§ Forbidden/rare decays of
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CPV in penguin decays
Belle (July 2002)
ACP(KS)=0.73±0.64
ACP(’KS)=0.76±0.36
ACP(J/KS)=0.719±0.074
Expected errors in ACP’s
ACP(KS, ’KS)=ACP(J/KS)
In SM,
New phase in penguin loop may change this relation
KEKBPEP-II
Next B factory
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Atmospheric Neutrinos Can Make Beauty Strange?
§ R. Harnik, D. Larson, H. Murayama and A. Pierce (hep-ph/0212180), D. Chang, A. Masiero and H. Murayama (hep-ph/0205111)
§ Leptogenesis models inspired by the naïve SO(10) unification exist where the near-maximal mixture of and results in large mixing of RH super-b and super-s, giving O(1) effects on bs transitions such as– Asymmetry in B Ks (effect is in first order)– Bs mixing– b s(effect is of the order of |Cg(NP)|2)
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Dominant Right-Right Mixing case
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SUSY effect in B K*
§ These measurements are excellent probe to search for SUSY§ Inclusive decay, bsll, is much less model dependent. An e+e B fact
ory provides a unique opportunity to measure this by pseudo reconstruction technique
A.Ali
m()2 distribution
F/B asymmetry
SM
SUSY models with various parameters set
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Rare decays of
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Charged Higgs in tree decay
BD(*)vsD
- Large branching fraction: ~1%- Uncertainty in form factor cancels in the ratio (BgD)/(BgD).- polarization is more sensitive to H±.
M.Tanaka
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Comparison with an LHC experiment
(BD)/(BD)at B factory with5,000 fb-1
B factories don’t really do tree diagrams of new particles with the exception of charged Higgs…
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KEKB upgrade strategy
Present KEKB L=1034
2002
03 04 05 080706 09 10 11
L=103
5
L~1036
dt =500fb1
One year shutdown to: replace vacuum chambers double RF power upgrade inj. linac g C-band
larger beam currentsmaller y*long bunch optioncrab crossing
ILER=1.5A2.6A
ILER=9.4A
ILER=20A
Constraint:8GeV x 3.5GeVwall plug pwr.<100MWcrossing angle<30mrad
dt =3000fb1
beforeLHC!!
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Detector upgrade
§ Higher luminosity collider will lead to:– Higher background
§ radiation damage and occupancy in the vtx. detector§ fake hits in the EM calorimeter§ radiation problem in the tracker and KL detector
– Higher event rate§ higher rate trigger, DAQ and computing
§ Require special features to the detector– low p identification for s reconstruction eff.– hermeticity for “reconstruction”
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/ KL detection 14/15 lyr. RPC+Fe
Tracking + dE/dx small cell + He/C2H5
CsI(Tl) 16X0
Aerogel Cherenkov counter + TOF counter
Si vtx. det. 3 lyr. DSSD
SC solenoid1.5T
8GeV e
3.5GeV e
Detector upgrade: an example
2 pixel lyrs. + 3 lyr. DSSD tile scintillator
pure CsI (endcap)
remove inner lyrs.
“TOP” + RICH
New readout and computing systems
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SVD occupancy and CDC hit rate
§ Current most inner layer of SVD’s occupancy is 3~5%
§ Current most inner layer of CDC’s occupancy is 2~3%
§ With 1035 luminosity, two layers of pixel + silicon (~15cm R) + CDC survives
§ With 1036 luminosity, Pixel + Silicon a la super BaBar design?
Radius = 15cm
Cathode
Inner
Main
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Does CDC work with L>1035 ?
§ Smaller cell§ Faster gas§ Larger starting
diameter
Yes !!
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Small Cell Chamber (with SVD2)
~20cm
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XT curve for small cell measured
Small cellNormal cell
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New PID detector
Present Belle: Aerogel Cherenkov counter both for barrel and endcap.
TOP counter for barrel &Aerogel RICH for endcap
Requirements: - Thin detector with high rate immunity - >3/K separation up to 4GeV/c - low p / separation
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Time of propagation (TOP) counter
20mm
time & X sensitive PMTs Fused silica(n=1.47)
Reflection mirror 200mm
A few meters
photon hits
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Aerogel RICH for endcap
§ Single event display§ Hit distribution
Super KEKBAccelerator upgrades
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What’s impressive about KEKB
§ KEKB and PEP-II have achieved the highest luminosities in history of particle accelerator/collider
§ KEK and PEP-II have recorded more than 100 fb1 of data and continue to accumulate Thanks to tremendous efforts by and ingenuity of the commissioning and operation groups
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Features of KEKB
§ Super conducting RF cavities and ARES cavities– Holds more than 1A of beam current with
SRF
§ IR region– 3m100m: the smallest beam size
among the storage rings– Finite crossing angle
§ Solenoids for positron ring– Suppress photo-electron clouds
§ Flexible Optics– Real time monitor and correction system
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Challenges with Super KEKB
§ High beam currents (LER 9.4A+HER4.1A)– Heating, breakdown will occur– Ultra high vacuum, beam lifetimes– Power consumption (80~100MW)– Stability of the beam/photo electron clouds– Injection– Noise/Background to detector
§ Beam-beam effect (tune shift of 0.05 assumed for 1035)– Beam-beam tune shift; unknown– For a double ring machine, more than 50 parameters must
be optimized simultaneously– Hard to maintain the optimum beam conditions due to
disturbances§ Optics with very small focusing depth (3mm)
– KEKB vertical beta is <6mm (world record)– Shorter bunch length:=more peak current gives more
power dissipation, shorter lifetime
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Towards Super KEKB
§ LER 9.4A + HER 4.1A (4~6 times as now)– Rewind solenoids– Double RF systems– Replace vacuum chambers of the both rungs– Cooling system
§ More focusing and shorter bunch (half as now)– New IR
§ Charge switch and better/faster injection– 8GeV positron injection with a C-band linac– Damping ring– New positron production target
§ Crab crossing
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Machine parameters
Energy : 3.1/9 GeVOptions April 2002from SBF Luminosity
Head-on collision(effective)Need crab cavityS-S, S-W simulation
LER HER LER HER LER HER
Horizontal emittance 33 33 33 33 92 92 nm
Vertical emittance 2.1 2.1 0.33 0.33 0.92 0.92 nm
x-y coupling 6.4 6.4 1 1 1 1 %
Beam current 9.4 4.1 17.2 7.8 27 9.3 A
Number of bunches 3400 3400
Bunch current 1.87 0.817 3.43 1.55 7.94 2.74 mA
Bunch spacing m
Half crossing angle mrad
Luminosity reduction RL
x reduction Rx
y reduction Ry
Bunch length 3 3 3.5 3.5 1.8 1.75 mm
Radiation loss U0 1.23 3.48 MeV/turn
Betatron tunes x/y 45.515/43.57 44.515/41.57
Beta at IP x*/ y* 30/0.3 30/0.3 15/0.3 15/0.3 15/0.15 15/0.15 cm
Beam-beam parameters x/y 0.068/0.05 0.068/0.05
Beam lifetime ~150 ~150 min
Luminosity 1035/cm2/sec
unit
10
0.83
0.65
0.1
0.6
0
0.1~0.2
4~10
SuperKEKB HyperKEKB SuperPEP-II
5018 5018
1
0.6
15
0.748
0.691
0.916
Baseline design of Super KEKB
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Crab crossing
§ Recent beam-beam simulation gives =0.10.25 with
x ≈ 0.5Head-on (crab) collisionz=y=3 mm
• yielding 0.8~2.01032 luminosity per bunch
>>1035cm2s1
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Crab cavity§ Crab crossing is powerful scheme to achieve high luminosity§ It is hard to develop crab cavity for extremely high beam current§ Test of crab crossing at KEKB in 2005~6
– 1 crab : 11 mrad/HER x=200 m– or 2 crabs: for both rinfs
Crab cavity
Nikko section
Magnetreconfiguration
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(Each building for 4〜 6 RF units.)
D8 D7
D4
D1
0D
11
new newn
ew
new
new
D1 D2D
5LER-RF(ARES)
HER-RF(ARES)HER-RF
(SCC)
5 buildings should be added.
50% more RF cavitiesDouble # of Klystrons
#RF/#SRF30/8
44/12
#Kly/ACPW(MW)23/45
56/73
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Energy exchange(HER : e+/LER : e)
§ Advantage :– Effect of photoelectron cloud can be reduced.
■ Positron energy increases.– Injection time can be reduced.
■ Intensity of injector : e- > e+
■ Beam current : e- > e+ § Unknown :
– Multipactering occurs in e+ at HER or not ?■ Height of vacuum chamber is smaller than LER.
– Is fast ion instability safe for e- in LER ?■ Electron energy decreases.
§ Major upgrade of injector linac is needed.– Energy upgrade : C-band scheme
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Linac upgrades for 8 GeV e+
AB
HER1 2 3 4 5C
e- Gun
DampingRing1.7-GeV
J-arc for e–
LER
e+ target
E(e–)=3.5 GeV, Q(e–)=10 nC to targetQ(e–)=5 nC for Injection
E(e+)=1.0 GeV
E(e–)=3.5GeV, Q(e–)=5 nC
E(e+)=8.0 GeV, Q(e+)=1.2 nC
Q(e+)=1.2nC
New C-band units
2-Bunches for Simultaneous Injection 1-st bunch -> e- Injection 2-nd bunch -> e+ production
S-band accl. units are replacedwith C-band units.Accl. Field 21 -> 41 MV/m
e+ Damping Ring for loweremittance
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Summary§ Belle and KEKB have resumed operation
after the He leak accident– Even with a current limit of less than 2.4A,
we have achieved new integrated luminosity records, for example, 462pb1 /day
§ We hope to accumulate >150fb1 by June– Expect to have a lot of physics results
§ We will install SVD2, two more RF cavities and come back in October
§ We are hoping to upgrade KEKB and Belle to reach 1035 luminosity and to accumulate 3000fb1 before 2010 when LHC starts producing results– Simulation tells us that we may reach 1036
with head-on collision with crossing angles using the crab cavities