Post on 05-Jan-2016
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)