ATLAS style lectures series presents The Belle and BelleII Experiments in Japan The Belle Experiment is an asymmetric e+e- collider situated in KEK Japan and its primary purpose is to study the CP-Violation and indirectly look for new physics running on the Upsilon(4S) center of mass = 10.58GeV
ATLAS style lectures series presents The Belle and BelleII Experiments in Japan The Belle Experiment is an asymmetric e+e- collider situated in KEK Japan and its primary purpose is to study the CP-Violation and indirectly look for new physics running on the Upsilon(4S) center of mass = 10.58GeV
Measurement of CP Violation Objective: Measure time dependent decay 3 possible contributions asymmetry of B and B going to the same final ▸ CP-Violation in decay (direct) state ▸ CP-Violation in mixing (indirect) a CP ( t ) = Γ ( B 0 → f CP ; t ) − Γ ( B 0 → f CP ; t ) ▸ CP-Violation by interference of Γ ( B 0 → f CP ; t ) + Γ ( B 0 → f CP ; t ) mixing and decay (mixing induced) 2 2 � � � � � � � � � � � � � � � � c c c c � � � � � � � � J / ψ J / ψ J / ψ J / ψ � � � � � � � � b d u, c, t b b d u, c, t b � � � � � � � � � c c � � c c � � � � � � � � � � � � � W + W − W − W + � B 0 B 0 W − W + � � B 0 B 0 W + W − � + ≠ + � � � � � � � � � � � � � � � � s s � s � � s � � � � � � � � u, c, t � d u, c, t b d � b d � � d � K 0 K 0 K 0 K 0 � � � � � � � � S S S S � � � � d d � d � � d � � � � � � � � � � � � � ▸ For B mesons, contributions from indirect CP-Violation are negligible ▸ For many decays, loop diagrams contribute to the amplitudes possibility to indirectly detect new physics 2 Martin Ritter The Belle II Experiment
Measurement of CP-Violation Experimental challenging task: 350 ▸ lifetime of B mesons is 1.5 ps Entries / 0.5 ps 300 ▸ flavour of B meson has to be known 250 200 Solution 150 ▸ Υ ( 4S ) : coherent B-meson pair production 100 ▸ one B to determine flavour (tag side), 50 other B for CP measurement (CP side) 0 ▸ boost system using asymmetric beam energies -6 -4 -2 0 2 4 6 ∆ t (ps) t → ∆ t = ∆ z ⟨ βγ ⟩ c ℓ − K − B 0 tag Υ ( 4S ) e − e + π + B 0 CP J / ψ K 0 S µ − π − Boost ∆ z ⟨ ∆ z ⟩ ∼ 200 ţm µ + 3 Martin Ritter The Belle II Experiment
Experimental requirements 25 Υ ( 1S ) Best place to produce BB in a clean σ ( e + e − → Hadrons ) [nb] 20 environment is at the Υ ( 4S ) : Υ ( 2S ) ▸ lowest energy with free B mesons 15 ▸ 1/3 of all events are BB Υ ( 3S ) 10 Υ ( 4S ) ▸ possibility to “turn off” B production by 5 continuum background lowering center of mass energy by 50 MeV 0 9.44 9.46 10.0010.02 10.34 10.37 10.54 10.58 10.62 e + e − Center-of-Mass Energy [GeV] Differences to LHC Energy is factor O( 1000 ) smaller than for LHC: ▸ there are no real “jets”: we see single particles ▸ mean momentum of charged particles is around 500 MeV Electron Collider: ▸ full knowledge about the center of mass frame ▸ no underlying events ▸ but: low cross section (more than factor 100) 4 Martin Ritter The Belle II Experiment
Belle/Belle II Experiment Asymmetric e + e − experiment mainly at the Υ ( 4 S ) resonance (10.58 GeV) KEKB/Belle SuperKEKB/Belle II operation 1999 – 2010 2014 – 2.11 × 10 34 cm − 2 s − 1 8 × 10 35 cm − 2 s − 1 peak luminosity 1023 fb − 1 (772 million BB pairs) 50 ab − 1 integrated luminosity 5 Martin Ritter The Belle II Experiment
Challenging environment 6 Martin Ritter The Belle II Experiment
Challenging environment Earthquake 6 Martin Ritter The Belle II Experiment
Challenging environment Earthquake Tsunami 6 Martin Ritter The Belle II Experiment
Challenging environment Earthquake Tsunami Nuclear meltdown 6 Martin Ritter The Belle II Experiment
Challenging environment Earthquake Tsunami Nuclear meltdown Tornado 6 Martin Ritter The Belle II Experiment
Challenging environment Earthquake Tsunami Nuclear meltdown Tornado 6 Martin Ritter The Belle II Experiment
Time of Propagation counter Electromagnetic Calorimeter DIRC with 20 mm quartz bars 8000 CsI Crystals, 16 X 0 MCP-PMT readout PMT/APD readout Pixel Vertex Detector 2 layer pixel detector (8MP) DEPFET technology Silicon Vertex Detector 4 layer double sided strips 20 − 50 ns shaping time Central Drift Chamber Aerogel RICH proportional wire drift chamber Proximity focusing RICH with 15000 sense wires in 58 layers silica aerogel
Electromagnetic Calorimeter ▸ no hadronic calorimeter needed due to low energy ▸ around 8000 CsI crystals: pure CsI in the endcaps, CsI(Tl) in the barrel ▸ crystals are expensive and will be reused from Belle ▸ good pointing and energy resolution Earthquake ▸ During the earthquake, the Belle detector (1500 t) moved by 6 cm ▸ but most probably it moved 20 cm in one direction and then came back ▸ inner detector was already disassembled but crystals were still in so far tests show that crystals are still working 8 Martin Ritter The Belle II Experiment
Electromagnetic Calorimeter ▸ no hadronic calorimeter needed due to low energy ▸ around 8000 CsI crystals: pure CsI in the endcaps, CsI(Tl) in the barrel ▸ crystals are expensive and will be reused from Belle ▸ good pointing and energy resolution Earthquake ▸ During the earthquake, the Belle detector (1500 t) moved by 6 cm ▸ but most probably it moved 20 cm in one direction and then came back ▸ inner detector was already disassembled but crystals were still in so far tests show that crystals are still working 8 Martin Ritter The Belle II Experiment
Particle Identification System Good separation between Kaons and Pions is very important ▸ Momentum and dE/dx will be measured in the tracking system ▸ Use of Cherenkov detectors to measure speed of the particle ▸ Cherenkov light is the optical analogy to the sonic boom ▸ particles that are faster than the speed of light in a given medium emit cherenkov light ▸ direction of the light is dependent on β 9 Martin Ritter The Belle II Experiment
Time of Propagation Counter DIRC = Detecton of internaly reflected Cherenkov light ▸ array of rectangular quartz bars ▸ cherenkov light is reflected internally ▸ MCP-PMT array at the end will detect position and time ▸ 40 ps time resolution, 3 σ K/ π separation 10 Martin Ritter The Belle II Experiment
Endcap A-RICH RICH = Ring Imaging Cherenkov Detector ▸ silica aergoel radiators used to create Cherenkov light ▸ light will form in circle screen ▸ two layers of different refractive materials used to produced focussed ring ▸ 4 σ K/ π separation Silica Aerogel ▸ produced by drying silica gel in a specific way ▸ low density (world record at 1.9 mg / cm 3 ) ▸ low refractive index 11 Martin Ritter The Belle II Experiment
Central Drif Chamber ▸ wire chamber with ∼ 15000 sense wires ▸ drif time ∝ distance to wire ▸ position resolution of O( 100 ţ m ) ▸ stereo wires to get θ -information ▸ determination of particle momentum 12 Martin Ritter The Belle II Experiment
Contribution to PID Drif chamber also contributes to particle identification due to different energy losses for different kind of particles 32 µ + on Cu Stopping power [MeV cm 2 /g] 28 100 µ − Energy deposit per unit length (keV/cm) µ π K p D Bethe Radiative Anderson-� Lindhard-� 24 Ziegler Scharff E µ c 10 Radiative� 20 Radiative� losses Minimum� effects� e e ionization reach 1% Nuclear� 16 losses Without δ 1 10 4 10 5 10 6 0.001 0.01 0.1 1 10 100 1000 12 βγ 0.1 1 10 100 1 10 100 1 10 100 8 [MeV/ c ] [GeV/ c ] [TeV/ c ] 0.1 1 10 Muon momentum Momentum (GeV/ c ) Particle Identification uses the combined information of all sub detectors the particle traversed 13 Martin Ritter The Belle II Experiment
Strip Vertex Detector n strip + ▸ 4 layer double sided strip detector p - stop ▸ pitch of 50 ţ m resp. 160 ţ m hole n bulk electron ▸ shaping time of 20 − 50 ns p strip + 14 Martin Ritter The Belle II Experiment
SVD Material Budget To reduce the material budget, the readout chips will be thinned down and put directly on the sensor 15 Martin Ritter The Belle II Experiment
SVD Material Budget To reduce the material budget, the readout chips will be thinned down and put directly on the sensor they call it the “Batman-shape” 15 Martin Ritter The Belle II Experiment
Pixel Vertex Detector ▸ innermost part of the detector ▸ 2 layer pixel detector (8M pixels) ▸ readout time of 20 ms ▸ data rate of 240 Gb / s = 30 GB / s ▸ pixel size of 50 × 50 ţ m and 50 × 75 ţ m ▸ single track vertex resolution O( 15 − 30 ţ m ) VON EINEM AUTODESK-SCHULUNGSPRODUKT ERSTELLT 170.00 23.00 124.00 23.00 22.00 14.00 23.00 90.00 23.00 136.00 16 Martin Ritter The Belle II Experiment
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