Prospects and Status of Belle II experiment Yoshiyuki Onuki High Energy Physics group The 3rd Tohoku University GCOE International Symposium 1
Outline KEKB and Belle experiment Physics motivation for Belle2 experiment SuperKEKB accelerator Belle2 detector Contributions from Tohoku University Construction schedule 2
Quark transition coupling constant in SM u c t V CKM : Cabibbo-Kobayashi- Maskawa Matrix d s b V CKM V CKM =1 f 3 arg V udv ub * V cd V cb * (0,0) V ud V ub* V cd V cb* f 3 (r,h) f 2 V td V tb* V cd V cb* f 1 (1,0) B-meson system is the best place to measure the matrix elements 3 since the three sides of the bottom related triangle is same order of magnitude.
KEKB e + e collider and Belle detector KEKB ~1 km in diameter Mt. Tsukuba Belle 8 GeV e - and 3.5 GeV e + collided on resonance of Y(4S)~10.58GeV Y(4S) consists of bounding state of bottom and unti-bottom quark and almost all Y(4S) decay into B-meson and anti B-meson pair. 15countries,63 institutes,429people L peak = 2.1 x 10 34 sec -1 cm -2 >Twice of the design Luminosity! Producing enormous BB pairs copiously called B-factory Detecting the produced particles and reconstruct the interaction by Belle 4
The last beam abort of KEKB on June 30, 2010 First physics run on June 2, 1999 Last physics run on June 30, 2010 L peak = 2.1x10 34 /cm 2 /s L > 1ab -1 Corresponds to 1.1 Billion BB pairs! 5
Physics outputs from Belle Established the mixing-induced time-dependent CP violation(tcpv) with B 0 J/yK S and related decays in 2002. This provides sin2f 1. No.55 Yutaro Sato Study of B-pi tagging method at the Y(5S) resonance for the measurement of CP-violation parameter sin2f1 Measured TCPV of B 0 fk S and related penguin-dominated decays Discovered a new resonance named X(3872) and exotic hadrons. The studies cotributes nuclear physics. Measured f3, an angle of CKM unitary triangle, with various methods No.53 Yasuyuki Horii First Evidence of the Suppressed B Meson Decay B - DK -, D K + p - No.5 Kennosuke Itagaki Study of the B D*pi decay for CP violation measurement No.23 Zenmei Suzuki Study of decay B->DK,D->KsKpi for the measurement of the CP-violating angle phi3 6
Motivation for upgrade To observe beyond the Standard Model phenomena, New physics contribution via Tunnel effect using penguin-dominant decays b sss transition b sg,sll transition B tn decay At the same time, well constrained CKM unitary triangle works as the Standard Model reference 7
b sss transition S J/yKs =sin2f 1 DS fks S fks -S J/yKs In SM, DS fks ~0 DS fks 0 indicates NP Experimental determination of DS fks can constraint flavor violation in SUSY model under the some approximation. 8
b sg&sll transition Model independent new physics search Both mode can compare SM model prediction with experimental measurements. For example: Forward backward asymmetry in B K*l + l - 657 million BB pairs arxiv:0810.0335 Belle collaboration I.Adachi et al. The solid (dashed) curve shows the SM (C 7 = C SM 7 ) prediction. 9
KEKB and Belle upgrade plan 10
KEKB to SuperKEKB SuperKEKB 10 36 40 times higher luminosity KEKB Next generation B-factories 11 E.Kikutani / M. Masuzawa
Strategies for increasing Luminosity (1) Smaller b y * (2) Increase beam currents Nano-Beam scheme (3) Increase x y Collision with very small spot-size beams 12
SuperKEKB collider e + 4GeV 3.6 A Belle II Colliding bunches New beam pipe & bellows e - 7GeV 2.6 A SuperKEKB New IR New superconducting /permanent final focusing quads near the IP Replace short dipoles with longer ones (LER) Redesign the lattices of HER & LER to squeeze the emittance Low emittance positrons to inject Damping ring Add / modify RF systems for higher beam current Positron source New positron target / capture section TiN-coated beam pipe with antechambers Low emittance gun Low emittance electrons to inject Target: L = 8x10 35 /cm 2 /s 13
How to reconstruct B-meson:B 0 J/yK S PID ECL KLM Extrapolate tracks from outer to inner detector Particle identification Energy measurement CDC Reconstruction of charged particle Determination of the momentum SVD Insert tracks to the Silicon Vertex Detector Determine energy and momentum and vertex in each particle 14
Belle to Belle II upgrade SVD: 4 DSSD lyrs g 2 DEPFET lyrs + 4 DSSD lyrs CDC: small cell, long lever arm ACC+TOF g TOP+A-RICH ECL: waveform sampling (+pure CsI for end-caps) KLM: RPC g Scintillator +MPPC(end-caps) 15
DEPFET pixel detector(pxd) DEPFET pixel detector: Baseline for innermost pixel Acceptance Radiation tolerance Radiation length Hit occupancy 17 <θ<150 >10MRad 0.16%/layer 1-2%(layer1) 16
DEPFET(DEPleted Field Effect Transistor) Full depleted Bulk CMOS. Electron-hole pairs generated by charged Particle accumulates in the Internal gate. Electric field generates between Gate Internal gate The situation is as same as applying Gate voltage in the MOSFET. Drain-Souce current I ds is flowing. Instead of readout electron-hole pair, readout DI ds of MOSFET A full depleted MOSFET with Internal gate acts like a pixel detector(50mm 56mm 50mm) 17
Silicon strip vertex detector(svd) Acceptance 17 <θ<150 Radiation tolerance Radiation length 30MRad ~0.58%/layer Hit occupancy 6.7%(layer3) 6 DSSD 187 DSSDs rf- strips e e 1D+1D strip sensor acts as 2D detector z- strips h h Double Sided Strip Detector (DSSD) 18
Origami module Flexible print circuit board Conventional readout scheme(belle) R/O chips in both side Bonding wires rf- strip z- strip APV25 Doesn t work in Belle2@40 times Lum. of Belle Origami readout scheme(belle2) - Replacing fast R/O chip: VA1TA APV25 - Adapting chip on sensor method for S/N - Realizing one side readout to extract the other side readout wrapping DSSD with Flex PCB. Flexible print circuit board Bonding wire Rohacell DSSD 19
Central Drift Chamber longer lever arm improve resolution of momentum and de/dx Belle Belle Belle II inner most sense wire r=88mm r=168mm outer most sense wire r=863mm r=1111.4mm Number of layers 50 56 Total sense wires 8400 14336 Belle II small cell normal cell Gas He:C2H6 He:C2H6 sense wire W(Φ30μm) W(Φ30μm) field wire Al(Φ120μm) Al(Φ120μm) 10 mm 6~8 mm 18 mm 10~20 mm 20
Particle Identification(PID) Detector Time of Projection chamber(top) Threshold type Cherenkov PID(Belle) Quartz RICH PID for barrel Aerogel RICH type PID for endcap RICH with Time measurement TTS~40ps Aerogel Ring image Cherenkov(ARICH) 200mm 200mm Aerogel radiator n~1.05 Hamamatsu HAPD + new ASIC 21
Contributions from Tohoku University group Beam BG study in beam interaction region SVD vertex detector construction SOI(Silicon On Insulator) pixel detector for future PXD option Beam BG study by K.Nakano&H.Yamamoto SOI beam test study by H.Katsurayama SOI radiation tolerance study by Y.Ono SVD development by me & Y.Himori 22
Construction Schedule of SuperKEKB/Belle II FY2009 FY2010 FY2011 FY2012 FY2013 FY2014 Linac e+ new matching & L-band acc. R&D Construction RF-gun & laser system Design study Commissioning at test stand Damping Ring R&D, Design Mass Fabrication Tunnel construction Building construction Installation Main Ring Building construction R&D, Design Mass Fabrication Installation Belle II Detector R&D Construction Mass Production Installation 23 Cosmic Ray Test
Peak Luminosity (cm -2 s -1 ) Integrated Luminosity (ab -1 ) Luminosity upgrade projection Milestone of SuperKEKB 9 month/year 20 days/month We will reach 50 ab -1 in 2020~2021. Commissioning starts mid of 2014 Shutdown for upgrade FY 24
Summary KEKB&Belle upgrade project was approved The target is 40 times luminosity of KEKB and 50 times data of Belle. The motivation is to observe beyond standard model in particle physics. Tohoku group contributes beam BG study in IR, SVD and SOI pixel detector for future upgrade option. The experiment will start in 2014 25
Funding Status 10 billion yen funded by Very Advanced Research Support Program of MEXT(Ministry of Education, Culture, Sports, Science and Technology) in FY2010-2012 KEKB upgrade has been approved. Construction had started. 26
SOI pixel detector for PXD option Silicon On Insulator(SOI) pixel detector - Next generation pixel detector R/O electronics and sensor in single wafer =>Monolithic detector. -Able to implement sophisticated functions in Front End Electronics. e.g. counter, memory -Developed by KEK and Tohoku Univ etc. -Manufacturer is OKI-Semiconductor Miyagi e+ beam test@tohoku LNS 27
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