Status of Belle Super KEKB plan

Status of BelleSuper KEKB plan

SLAC seminarMarch 21st, 2003Nobu Katayama

KEK

March 21st, 2003March 21st, 2003 Nobu KatayamaNobu Katayama 22

Outline

§ Belle/KEKB status– General– Beam pipe accident– SVD2

§ Recent physics results § Super KEKB plan

– Physics– Detector study– Accelerator study


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


Best day (03/17/2003)462pb1/day recorded

NK on shift!


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


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


Pictures using optical fiber scope


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


Cutting Al part of the beam pipe


Inner Beryllium beam pipe

Direction of Helium gas

position of leak


Location of the leak


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


Photo before re-assembly (1999)


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


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)


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


SEM photos of Be surface

Beryllium is made by sintering, from a powder of 5~40m Be particles. Some of them are missing


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


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!


Daily Luminosity2002/92003/3/8

Current limit 2.4A

Old beam pipere-installed

Current limit 2.2A


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


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


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?


Beam pipe for SVD2

Smaller radius (1.5cm)

Better cooling with liquid

Heavier masks

Better mechanicalstructures


ForwardBackward

L#1

L#3

L#4

L#2

DSSDDSSDhybridhybridflexflex DSSDDSSDDSSDDSSD

Ladder Ladder constructionconstruction


Ladder mount completed on 13-Feb. 2003.

The last of the The last of the 54 ladders!54 ladders!


Track reconstructed!

ShibataShibata

Recent physics results

Just flashing…

VubBK

BK*, K


Fully reconstructed B mesons


Vcb measurement with tag


Vub measurements


Separating two B’s


Two inclusive Vub measurements

§ Two new tagging methods– Simulated annealing– D*l reconstruction

§ Can measure Mx distribution


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


BK* angular analysis


Projected angular distributions

We have just started!

More and more Bs

Super KEKB


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)


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


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


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)


Dominant Right-Right Mixing case


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


Rare decays of


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


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…


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!!


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”


/ 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


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


Does CDC work with L>1035 ?

§ Smaller cell§ Faster gas§ Larger starting

diameter

Yes !!


Small Cell Chamber (with SVD2)

~20cm


XT curve for small cell measured

Small cellNormal cell


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


Time of propagation (TOP) counter

20mm

time & X sensitive PMTs Fused silica(n=1.47)

Reflection mirror 200mm

A few meters

photon hits


Aerogel RICH for endcap

§ Single event display§ Hit distribution

Super KEKBAccelerator upgrades


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


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


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


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


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


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


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


(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


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


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


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

Status of Belle Super KEKB plan

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