Gagan Mohanty

Prospects of Super KEKB andBelle II Experiment

Tata Institute (TIFR), India

2

Talk outline

28-09-2009

• Physics case

• Accelerator Super KEKB in Japan

• Detector upgrade Belle → Belle II

• Current status of the project Timeline, collaboration, funding

• Closing remarks

3

Threefold Way

28-09-2009

Energy (Tevatron, LHC)

Today, breakthroughs in elementary particle physics are made possiblethrough the advances in three complementary directions

I shall concentrate on the right-most corner, i.e., luminosity frontier

Now: 10 years after the B factories

Discovery of CPV in B decaysDiscovery of CPV in B decays

Precision test of KM paradigmPrecision test of KM paradigm

Look for new physics (NP) signatureLook for new physics (NP) signature

Step1

Step2

Step3

2001 summer !

2008

28-09-2009 4

Kobayashi, Maskawa, PTP 49 (1973) 2

Need more than 50 times the data (50 ab−1) we have at present to decipherNP effects

What is so special about 50?

50 ab−1

Lu~

CKM UT triangleNow

New CP phaseNP effect

B K(*)l+l-: AFB

Theory error50 ab−1

50 ab−1

Flipped C7

28-09-2009 5

Xu et al., PRD 74 (2006) 114019

Is that all?

1, 2, 3s @ 50 ab−1

D0D0 mixingτ LFV decays X(3872)

Z+(4430)

Super B factories are really super flavor factories

28-09-2009 6

LFV in tau decays, CPV in D-mixing would be unambiguous signatures ofNP – beam polarization, operating @ threshold further benefit the cause

Good detector, huge data in a clean environment Rest assured

In fact a “treasure chest”

28-09-2009 7

Would be possible with a good amount data taken at ϒ(5S)

Complementary with the LHC

S.Stone

Bs

Com

mon

No IPg,n

50ab−1

NP flavor couplings

Diagonal: Energy frontier(LHC – ATLAS, CMS)

Off-diagonal: Lumi frontier(super flavor factory, LHCb)

• Settle NP models• Look for higher scale NP

Super flavor factory vs LHCb

28-09-2009 8

What about worst-case scenario?

28-09-2009 9

• Imagine the possibility, where NP follows the SM patternof flavor and CP violation (minimal flavor violation)

• Even in this most unfavorable scenario, super flavor factoriesare still sensitive up to NP mass range of 600-1000 GeV

D’Ambrosio et al., NPB 645 (2002) 155

• The model predicts all NP flavor couplings are zero – naturemay not be so much unkind to us!

• Going little up, in the next-to-minimal flavor violation, the to-beexploratory scale goes beyond 10 TeV LHC domain

• For generic flavor violation scenario, super flavor factoriesare sensitive up to ~1000 TeV

Explore luminosity frontier

2.1×1034

1.2×1034

28-09-2009 10

KEKB/Belle (Japan)

Super KEKB (Japan)

PEP II/BaBar (US)

SuperB (Italy)Peak luminosity ~1036 cm−2s−1

One eqn. – many ways to play around

L

2ere1

y*

x*

Iy

y*

RL

Ry

• Raise the beam current, I• Larger beam-beam par, xy

• Smaller b*y

× ~5~5

~1/2

~50

High current approach

< 1/20+ low emittance

Nano-beam approach

Brute forceRealizable

New schemeRisk?

Baseline:

(short bunch) (long bunch)

28-09-2009 11

Super KEKB (Japan) SuperB (Italy)

12

Crab cavities installed andundergoing testing in beam

Superconducting cavities willbe upgraded to absorb morehigher-order mode power upto 50 kW

The beam pipes and allvacuum components willbe replaced with higher-current design

Super KEKB

e− 4.1 A

e+ 9.4 A

High-current option (baseline)

L

2ere1

y*

x*

Iy

y*

RL

Ry

Damping ring

New IR: Belle II

Crab crossing

+ Linac upgrade

8 GeV

3.5 GeV

28-09-2009 12

Higher currentMore RFNew vacuum system

The state-of-art ARES coppercavities will be upgraded withhigher energy storage ratio tosupport higher current

Crab crossing and its impact

Crossing angle 22 mrad

Head-on (crab)

(Simulation: K. Ohmi)

2222 mradmradcrossingcrossing

crab crossingcrab crossing

28-09-2009 13

2007

2009Crab ON

2008

Crab OFF

Crabbing: successful!

L = 2.11×1034 (17 July)higher than without crab(new skew sextupoles)

Specific luminosityhas increased ~30%

Nano-beam scheme

Present KEKB

SuperB

L NN f

4 x* y

*RL

L

2ere

1 y

*

x*

I y

y*

R L

R y

5mm

1mm

100mm

(w/o crab)L

Hourglass condition:β*

y >~ L=sx/f

Half crossingangle: f

1mm

5mm100mm

28-09-2009 14

15

Replace long TRISTANdipoles with shorter ones

Tin coated beam pipeswith antechambers Nano-beam option

e− 2.1 A

28-09-2009 15

Low emittanceelectrons to inject

Low emittancepositrons to inject

New positron targetand capture section

Add/modify RF systems

New superconducting /permanent final focussing quads

New IR: Belle II

e+ 3.7 A

Super KEKB

Comparison of parameters

High-current option includes crab crossing and travelling focusNano-beam option does not include crab waist

KEKBdesign

KEKB achieved(with crab)

Super KEKBhigh-current

option

Super KEKBnano-beam

option

by* (mm)(LER/HER) 10/10

6.5/5.9(5.9/5.9)

3/6 0.24/0.37

ex (nm) 18/18 18(15)/24 24/18 2.8/2.0

sy (mm) 1.9 1.1 (0.84) 0.85/0.73 0.084/0.072

xy 0.0520.108/0.056

(0.101/0.096)0.30/0.51 0.09/0.09

sz (mm) 4 ~ 7 5(LER)/3(HER) 5

Ibeam (A) 2.6/1.11.80/1.45

(1.62/1.15)9.4/4.1 3.6/2.1

Nbunches 5000 1387 (1585) 5000 2119

Luminosity(1034 cm−2 s−1)

1 1.76 (2.11) 53 80

28-09-2009 16

Luminosity projection

3-year shutdownfor the upgrade

L~2×1035

L~8×1035

50ab−1 by ~2020

~10ab−1 by 2016

28-09-2009 17

Requirements for the detector

28-09-2009 18

• Will be built by upgrading the current Belle spectrometertaking the following points into account

1) Higher background

2) Higher event rates

3) New requirements

− Radiation damage, higher occupancy

− Higher DAQ rate

− Improved hermiticity for LFV searches and study of final states involving neutrinos

Super KEKB baseline detector

Belle

Belle II

SVD: 4 layers g 2 DEPFET + 4 DSSD layersCDC: small cell and long lever armPID: ACC+TOF g TOP+A-RICHECL: waveform sampling, pure CsI for endcapKLM: RPC g Scintillator+SiPM (endcap)

28-09-2009 19

Progress and planJun 2004: LoI for Super KEKBJan 2008: KEK Roadmap

Super KEKB is identified as high priorityDec 2008: New collaboration (Belle II) officially formed

13 countries, 43 institutesElection of the spokesperson

Mar 2009: BPAC (Chair: T.Nakada) endorsement

Mar 2009: FY2008/9 supplemental budget:~5M$ for the Belle upgrade

May 2009:~27M$ for KEKB upgrade R&DJuly 2009: 3rd Open Belle II collaboration meeting

28-09-2009 20

Current organizational setup

28-09-2009 21

22

Closing Remarks

• Super KEKB in Japan is one of the candidates Baseline design (high-current option) is finalized, work

in progress for the nano-beam option Belle II collaboration is formed Partial funding is already secured

28-09-2009

• Both the B factories – Belle and BaBar – have performedexceptionally well, beyond their original design

• CKM paradigm has been established as the only source ofCP violation in the SM

• Proposal for two super flavor factories with raison d’être toprobe NP effects (complementary to LHC)

Your active support and participation are most welcome