Belle and Belle IIChristoph Schwanda

Institute of High Energy Physics (HEPHY)Austrian Academy of Sciences

RECFA Meeting Open Session - Austria

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KEK Tsukuba siteLinac

KEKB rings (HER+LER)Belle detector

Mt. Tsukuba

The KEKB collider• KEKB collides 8 GeV

electrons on 3.5 GeV positrons

• Center of mass energy:10.58 GeV (Y(4S) resonance) production of B pair at threshold

• One interaction point (Belle)

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e+ source

Ares RF cavity

Belle detectorSCC RF(HER)

ARES(LER)

First physics run on June 2, 1999Last physics run on June 30, 2010Lpeak = 2.1x1034/cm2/sLtotal > 1ab-1

m / KL detection 14/15 lyr. RPC+Fe

CsI(Tl) 16X0

Si vtx. det. 3(4) lyr. DSSD

SC solenoid 1.5T

8 GeV e-

3.5 GeV e+

Aerogel Cherenkov cnt. n=1.015~1.030

Central Drift Chamber small cell +He/C2H5

TOF counter

The Belle detector

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Belle: 772 million BB eventsBaBar: 470 million BB events

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B factories: a success story

B0→J/ψK0_B0→J/ψK0

Discovery of CP violationin the B meson system (2001)

Confirmation of CKM mechanism

Rate of the decay B0 (B0)

→J/ψK0 as a function of the decay time difference of the two Bs in Y(4S) → BB events

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“… As late as 2001, the two particle detectors BaBar at Stanford, USA and Belle at Tsukuba, Japan, both detected broken symmetries independently of each other. The results were exactly as Kobayashi and Maskawa had predicted almost three decades earlier.”

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Vienna’s contributions to Belle• Belle member since 2001• Hardware

– Readout system for the siliconvertex detector (SVD), installed 2003

– 110,592 readout channels in total– Worked flawlessly for 7 years

• Physics analysis– Leading the Belle CKM group

(measurements of |Vcb| and |Vub| withsemileptonic B decays, search for the charged Higgs)

– Charmed meson spectroscopy(semileptonic and leptonic D decays)

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Vienna results: B semileptonicFirst evidence for B wln [PRL 93, 131803 (2004)]

Hadronic mass moments in B Xcln [PRD 75, 032005 (2007)]

Measurement of|Vcb| and mb from inclusive semileptonic B decays [PRD 78, 032016 (2008)]

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Vienna results: charm spectroscopy

Measurement ofD K( )p ln[PRL 97, 061804 (2006)]

Measurement of Ds mn[PRL 100, 241801 (2008)]

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Most recently: |Vcb| from B0 ® D*- l+ n

The most precise measurement of |Vcb| using exclusive decays (3.0% experimental error)

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[PRD 82, 112007 (2010)]

KEK B factory upgrade• The KEK Super B factory aims at accumulating

50 times the Belle data set by 2022

0.6/ab/month(4x1035/cm2/s)

0.9/ab/month(6x1035/cm2/s)

1.2/ab/month(8x1035/cm2/s)

50/ab1/fb Y(4S) data =1.1 million BB events

1/ab Y(4S) data =1.1 billion BB events

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Searching for physics at the TeV scalewith precision flavor physics

???

Flavor changing neutral currents(virtual contributions of new, heavy particles in loops)

Precision test of CKM unitarity (search for new CP violating phases)

Search for the charged Higgs boson in B tau nu andB D(*) tau nu decays

Search for lepton flavor violation in B and tau decays (SUSY breaking mechanism, right-handed neutrino couplings)

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From Belle to Belle II

• The Belle II detector will be built by upgrading the present Belle spectrometer

• Requirements for Belle II– 40x higher physics rate faster detector– Higher backgrounds

more radiation damage, higher occupancy– Need better detector hermeticity for lepton flavor

violation searches

Particle IDring imaging Cherenkov devices(TOP in the barrel, ARICH in the forward)

Belle II detector

Pixel detector(2 layers)

Silicon strip detector(4 layers)

Drift chambersmaller cell size

Em. calorimeterwave form samplingpure CsI (endcaps)

Muons, neutralsscintillator strips (endcaps)

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Belle II Silicon Vertex Detector (SVD)

• Vienna is leadingfor the design,development andconstruction of theentire Belle II4-layer SVD system

• This includes– Double-side silicon sensors– Ladder mechanics and cooling– Readout electronics for 240,000 channels

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Challenges in the Belle II SVD design • Background

– The Belle II SVD must be able to handle trigger ratesup to 30 kHz

• Material– Charged particles down to a transverse momentum of

50 MeV must be tracked ® ultra-low mass design• Space

– The entire system including cabling, cooling, support and services must fit into a narrow, 10 cm wide gap.

Our design is documented in the Belle II TDR(KEK Report 2010-1, arXiv:1011.0352)

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4-layers of double-sidedsilicon sensors (DSSDs)

read out by afast front-end chip (APV25)

Flash analog-digitalconverter (FADC)

with hit time finding

Low mass ladder design:Carbon fiber ribs

CO2 coolingSlanted forward sensors

Belle II SVD design

• 1.2 m2 of double-sided silicon detectors

• 4 layers (r=3.8cm…14cm) – surrounding pixel detector

• 243k readout channels• CO2 cooling• Low-mass: 0.55% X0 per layer

(including services)

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Why hit time finding? Occupancy Reduction

Threshold

Threshold

Tim e over threshold ~ 2000ns (m easured)

Tim e over threshold ~ 160ns (measured)

Sensitive tim e window ~ 20ns

VA1TATp~800ns

APV25Tp~50ns

Pulse shapeprocessingRM S(tm ax)~3ns

Gain ~12.5

Gain ~8

Total gain ~100

With hit time reconstruction, we can cope with 50-fold increase in luminosity19

Origami chip-on-sensor concept

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Manpower and funding

• 12 FTE working in the Vienna Belle/Belle II group– 5 FTE on Belle physics analysis,

7 FTE on Belle II SVD construction– 3 female staff (25%)

• Funding– Belle physics analysis funded by the Austrian science

fund FWF– Funding for Belle II SVD construction has yet to be

secured

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Summary• The Vienna Institute of High Energy Physics plays

an active and visible role in both the Belle and the Belle II experiments

• Belle activity– Construction of the Silicon Vertex Detector readout

electronics– Now main focus on physics analysis

• Belle II– Leading the design, development and construction of

the entire 4-layer Silicon Vertex Detector system

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Backup

• Charged current interaction in the Standard Model

• VCKM is the unitary 3x3 matrix of coupling constants of weak transitions

• It also contains the KM phase, responsible for all CP violating phenomena observed so far!

The Cabibbo-Kobayashi-Maskawa theory

[Kobayashi, Maskawa, Prog. Theor. Phys. 49, 652 (1973)]

Existence of CP violation implies (at least) 6 quark flavors!

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Main physics goals of the B factories

• Find CP violation in B decays, as predicted by the CKM theory

• Confirm the unitarity of the CKM matrix

The CKM unitarity triangle

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The Belle collaboration

15 countries, 62 institutes, ~400 collaborators

HEPHY ViennaITEPKanagawa U.KEKKorea U.Krakow Inst. of Nucl. Phys.Kyoto U. Kyungpook Nat’l U. EPF Lausanne Jozef Stefan Inst. / U. of Ljubljana / U. of MariborU. of Melbourne

Aomori U.BINPChiba U.Chonnam Nat’l U.U. of CincinnatiEwha Womans U.Frankfurt U.Gyeongsang Nat’l U.U. of HawaiiHiroshima Tech.IHEP, BeijingIHEP, Moscow

Nagoya U.Nara Women’s U.National Central U.National Taiwan U.National United U.Nihon Dental CollegeNiigata U.Osaka U.Osaka City U.Panjab U.Peking U.U. of PittsburghPrinceton U.RikenSaga U.USTC

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e- 2.6 A

e+ 3.6 A

To get x40 higher luminosity

Colliding bunches

Damping ring

Low emittance gun

Positron source

New beam pipe& bellows

Belle II

New IR

TiN-coated beam pipe with antechambers

Redesign the lattices of HER & LER to squeeze the emittance

Add / modify RF systems for higher beam current

New positron target / capture section

New superconducting /permanent final focusing quads near the IP

Low emittance electrons to inject

Low emittance positrons to inject

Replace short dipoles with longer ones (LER)

KEKB to SuperKEKB

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Machine design parametersparameters

KEKB SuperKEKBunits

LER HER LER HER

Beam energy Eb 3.5 8 4 7 GeV

Half crossing angle φ 11 41.5 mrad

Horizontal emittance εx 18 24 3.2 4.3-4.6 nm

Emittance ratio κ 0.88 0.66 0.27 0.25 %

Beta functions at IP βx*/βy

* 1200/5.9 32/0.27 25/0.31 mm

Beam currents Ib 1.64 1.19 3.60 2.60 A

beam-beam parameter ξy 0.129 0.090 0.0886 0.0830

Luminosity L 2.1 x 1034 8 x 1035 cm-2s-

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• Small beam size & high current to increase luminosity • Large crossing angle• Change beam energies to solve the problem of LER short lifetime

New Physics reach with 50/abcompared to energy frontier experiments

See T. Aushev et al.,“Physics at Super B Factory”,arXiv:1002.5012 [hep-ex]for more details

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Complementarity LHC/Super B factory

• Precision flavor data allows to exclude wide areas of the NP parameter space

• This allows to focus searches at the LHC and properly interpret the results

MSSM with minimum flavor violation

G. Eigen, arXiv:0907.4330

LFV and New Physics

( )e

0

( )e223(13)l

(m )

tlg

SUSY + Seasaw Large LFV Br(tmg)=O(10-7~9)

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4

262

( a101

) t nL

L

SUSY

BTeV

m

mr

m

t3l,lh

Neutral Higgs mediated decay. Important when MSUSY >> EW scale.

462

7 322

tan 100

60

( 3 )

4 10A

L

L

B

G

m

r

m

m

eV

( )s

( )s

h

model 　 Br(t→mg) Br(t→lll )mSUGRA+seesaw 　 10-7 10-9

SUSY+SO(10) 　　　　 10-8 10-10

SM+seesaw 　　　　 10-9 10-10

Non-Universal Z’ 　 10-9 10-8

SUSY+Higgs 　　　　 10-10 10-7

=

Rare t decaysLF violating t decay?

Integ. Lum. （ ab-1 ）Reach of B factories

Super B factories

Upper limits

tmg

meg

teg

T.Goto et al., 2007

Theoretical predictions compared to present experimental limits

LP 2009

Charm FCNC

Charm mixing and CPB Physics @ Y(4S)

Bs Physics @ Y(5S)t Physics

M. Giorgi, ICHEP2010

Belle II SVD readout electronics

Full readout chain to DAQ• To be designed and built by HEPHY• Prototypes exist for all stages

Origami module

Repeater box

FADC+PROC VME

Data processing and hit time finding (~3ns) in

FPGA firmware

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Belle-II collaboration

2004.06 SuperKEKB LoI2008.01 KEK Roadmap2008.03 1st Proto collaboration meeting2008.10 Detector study report2008.12 New collaboration, Belle-II, started~300 collaborators from 43 institutions in

13 countries~2010.11 Technical Design Report available

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SuperKEKB/Belle II costs• Construction Cost : $340M

– Appropriated• FY2009 stimulus money $35M• FY2010 line item : $5M for a positron accumulator ring• FY2010 stimulus money $100M

– Soon to be approved• FY2011 ~$200M

• Operation cost ~$70M/year• Belle II SVD costs ~EUR 2.6M

(Vienna share ~EUR 450.000)