Status and Physics Prospects of the Super KEKB

Status and Physics Prospects of the Super. KEKB Project Y. Horii Tohoku Univ. (Japan) 5 th March 2011, La Thuile 2011 1

KEKB Collider L 2 B ER e l l e R E H Tsukuba city (40 minutes from Tokyo by train) KEKB parameters � HER (e-): 8. 0 Ge. V � LER (e+): 3. 5 Ge. V � ECMS = U(4 S) mass B meson pair � Peak luminosity = 2. 1 x 1034 /cm 2 s � Integrated luminosity > 1 ab-1 (June 1999 - June 2010)

Belle Detector KL and Muon Detector Electromagnetic Calorimeter e+ e. Time of Flight Silicon Vertex Detector (Double-sided silicon strips) Aerogel Cherenkov Drift Chamber K±/p± identification (Eff. ~ 90%, fake ~ 10%) 3

A Success Story at B-Factories Discovery of CP violation in the B system PRL 98, 031802 (2007), 0. 5 ab-1 _ B 0 J/ψK 0 Asymmetry _ _ =(N-N)/(N+N) 4 Measurements of the CKM matrix elements

Upgrades KEKB collider Belle detector 5 Super. KEKB collider Belle II detector

Super. KEKB Collider Approved in 2010. e- Smaller asymmetry 8 / 3. 5 Ge. V 7 / 4 Ge. V Belle II e+ Larger crossing angle 2 f = 22 mrad 83 mrad for separated final-focus magnets. High currents e-: 2. 6 A e+: 3. 6 A Replace short dipoles with longer ones (LER). Small beam sizes sx~10 mm, sy~60 nm Damping ring Redesign the lattices of HER & LER to reduce the emittance. Ti. N coated beam pipe with antechambers 6 L = 8 x 1035 cm-2 s-1

Peak Luminosity Super. KEKB 7

Peak Luminosity (cm-2 s-1) Integrated Luminosity (ab-1) Schedule Milestone of Super. KEKB 9 months/year We will reach 50 ab-1 20 days/month in 2020 -2021. Commissioning starts in 2 nd half of FY 2014. Shutdown for upgrade Year 8

Detector Upgrade 9 Feb. 24 th, 2011 H. Nakayama (KEK) 9

Detector Upgrade Vertex detector: 4 lyr. Si strip 2 lyr. pixel + 4 lyr. Si strip 10 Feb. 24 th, 2011 H. Nakayama (KEK) 10

Detector Upgrade Drift chamber for tracking: smaller cells Vertex detector: 4 lyr. Si strip 2 lyr. pixel + 4 lyr. Si strip 11 Feb. 24 th, 2011 H. Nakayama (KEK) 11

Detector Upgrade Drift chamber for tracking: smaller cells Vertex detector: 4 lyr. Si strip 2 lyr. pixel + 4 lyr. Si strip New PID system: Cherenkov imaging, very fast readout 12 Feb. 24 th, 2011 H. Nakayama (KEK) 12

Detector Upgrade Drift chamber for tracking: smaller cells Vertex detector: 4 lyr. Si strip 2 lyr. pixel + 4 lyr. Si strip Calorimeter: new readout with waveform sampling New PID system: Cherenkov imaging, very fast readout 13 Feb. 24 th, 2011 H. Nakayama (KEK) 13

Detector Upgrade Drift chamber for tracking: smaller cells Vertex detector: 4 lyr. Si strip 2 lyr. pixel + 4 lyr. Si strip Endcap KL/muon: RPC Scintillator +MPPC Calorimeter: new readout with waveform sampling New PID system: Cherenkov imaging, very fast readout 14 Feb. 24 th, 2011 H. Nakayama (KEK) 14

Vertex Detector 4 lyr. Si strip 2 lyr. pixel(DEPFET) + 4 lyr. Si strip pixel Si strip Improve decay-time precision and acceptance (KS’s). 2 nd lyr. 1 st lyr. 15 6 th lyr. Pixel: r=14, 22 mm Si strip: r=38, 80, 115, 140 mm Belle II Belle 5 th lyr. 4 th lyr. 3 rd lyr. 2 nd lyr. 1 st lyr.

Particle Identification System at Belle II Endcap PID: Aerogel RICH (ARICH) Barrel PID: Time of Propagation Counter (TOP) 200 mm Quartz radiator ton o ov ph enk Cher Focusing mirror Hamamatsu MCP-PMT (measure t, x and y) Aerogel radiator n~1. 05 Hamamatsu HAPD + new ASIC TOP n 1 n 2 Completely different from PID at Belle, with better K/p separation, more tolerance for BG, and less material. 16 Multiple aerogel layers with different indices sq(1 p. e. ) = 14. 4 mrad Npe ~ 9. 6 sq(track) = 4. 8 mrad

More information of Belle II detector: “Belle II Technical Design Report” at ar. Xiv: 1011. 0352. 17

Physics at Super. KEKB/Belle II �A benefit to use One B meson (“tag” side) can be reconstructed in a common decay. Flavor, charge, and momentum of the other B can be determined. Effective for the modes including missing energy. Missing Also possible to partially reconstruct (semileptonically, …). 18

B tn � Evidence obtained at the B factories. BG only Sig + BG Example w/ semileptonic tag, 0. 6 ab-1 PRD 82, 071101 (2010) � Tension between the global CKM fit and direct measurement. Better measurement of B tn may reveal source of the tension. Tag-side information is vital for ≥ 2 n’s. 19 ~2. 8 s discrepancy

B tn at Belle II � In Two-Higgs Doublet Model (THDM) Type II, the branching ratio of B tn can be modified. H- Constrains on m. H± and tanb can be obtained. 20 5 ab-1 assuming 5% errors for |Vub| and f. B. 50 ab-1 assuming 2. 5% errors for |Vub| and f. B.

Direct CP Violation for B Kp If the only diagrams are a and b, we expect a b However, significant difference is obtained. K-p+ B Kp w/ 0. 5 ab-1 Nature 452, 332 (2008) Missing diagrams? Large theoretical uncertainty… 21 K -p 0 K +p- K +p 0

Direct CP Violation for B Kp at Belle II can compare to a model-independent sum rule: 22 measured sum rule Current measurement larger error for ACPK 0 p 0 expected measured Can be represented as diagonal band (slope precisely known from B and lifetimes): Belle II provides a good environment for the all neutral final state (K 0 p 0). sum rule � We 50 ab-1 assuming current central val

Decays of t Example: t mg Belle II provides good sensitivities � Can be enhanced by the effects on the t decays. of new physics in the loop diagram. g t t mg □ t mh △ t mmm ○ m Integrated luminosity (ab-1) 23

More information of physics prospects: “Physics at Super B Factory” at ar. Xiv: 1002. 5012. 24

Summary KEK collider Belle detector Super. KEKB collider Belle II detector Operation from 1999 to 2010. Aim to start commissioning in 2014. Peak luminosity = 2. 1 x 1034 / cm 2 s. Target of peak luminosity = 8 x 1035 / cm 2 s. Integrated luminosity = 1. 0 ab-1. Target of integrated luminosity = 50 ab-1 by 202 � Significant opportunities to search for new physics (B tn, B Kp, t decays, etc. ) at Super. KEKB/Belle II. � More information: � “Belle II Technical Design Report” at ar. Xiv: 1011. 0352. � “Physics 25 at Super B Factory” at ar. Xiv: 1002. 5012.

Backup Slides 26

KEKB Collider 2. 1 x 1034 cm-2 s-1 Crab crossing: 27

Funds for Super. KEKB � 100 oku-yen (~100 million dollars) approved in summer 2010. � Upgrade � Waiting 28 approved by the cabinet in December 2010. for the final approval by the Diet.

Belle II Detector Have to deal with: • Higher background (10 -20 x) radiation damage, higher occupancy • Higher event rates DAQ (L 1 trigg. 0. 5 20 k. Hz) • Improved performance hermeticity 29 Calorimeter: waveform sampling KL, m: scintillator strips for endcaps Drift Chamber: Vertexing: 2 lyrs DEPFET pixel smaller cell size improved read-out 4 lyrs DSSD PID: TOP barrel ARICH forward

Other Upgrades for Belle II Silicon vertex detector: new readout chip (APV 25) shorter integration time (800 ns 50 ns) Drift chamber: smaller cells Belle II Calorimeter: new readout system with waveform sampling (x 1/7 BG reduction) KL/Muon detector RPC Scintillator+MPPC Better performance against neutron BG 30

Expected Performance for Belle II 31