1. Belle II at SuperKEKB Kurtis Nishimura University of Hawaii
(on behalf of the Belle II Collaboration)
11th Conference on the Intersections
of Nuclear and Particle Physics
June 3, 2012
TexPoint fonts used in EMF.
Read the TexPoint manual before you delete this box.: AAAAAAA

2. B Factory Physics Proposals (1994)
Primary physics goal of the B factories:
Measure CP violation in B mesons, confirm the Kobayashi-Maskawa mechanism of CP violation...
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

3. Measuring CPV at Asymmetric B Factories
Search for time dependent decay asymmetries:
Belle
8.0 GeV e- , 3.5 GeV e+
¯° = 0.42
BaBar
9.0 GeV e- , 3.1 GeV e+
¯° = 0.56 e- e+
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

4. Time Dependent CPV – Success! (2001)
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

5. Luminosity at B Factories (1999-2010)
Performance far exceeding design values!
World record peak luminosity (Belle): 2.1 x 1034 cm-2 s-1
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

6. Variety of Successes from B Factories
Belle and BaBar have made a wide range of achievements over ~10 year running period:
Observation of CP violation in B decays.
CKM measurements of:
Matrix elements.
Unitary triangle angles.
CKM verified to ~O(10%)
Direct CP violation:
B  K ¼
New hadronic states:
X,Y,Z mesons
Rare probes of new physics:
b  s °
b  s
B0 tag _
BaBar LOI (1994)
CKM Fitter (2012)
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

7. Variety of Successes from B Factories
Belle and BaBar have made a wide range of achievements over ~10 year running period:
Observation of CPV in B decays.
CKM measurements of:
Matrix elements
Unitary triangle angles
CKM verified to ~O(10%)
Direct CP violation (e.g., B  K ¼).
New hadronic states: X(3872),Y,Z,…
Rare probes of new physics, e.g.,
B  ¿ º
b  s ° , b  s
Rare ¿ decays
Observation of D mixing.
X(3872)
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

8. Nishimura - Belle II @ SuperKEKB
What next…?
Continue to improve precision on CKM picture, search for deviations:
50ab-1
today
Explore current hints of possible new physics that already exist, e.g.,:
~few ¾ tension in current CKM fit between measured/predicted B  ¿ º and sin 2¯
“B  K ¼ puzzle” – difference in K+¼-/K+¼0 direct CP asymmetries.
Direct CP violation in D decays.
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

9. Nishimura - Belle II @ SuperKEKB
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

10. Nishimura - Belle II @ SuperKEKB
Upgrade!
KEKB  Super KEKB
Belle  Belle II
KEKB
SuperKEKB+ SuperB
PEP-II
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

11. SuperKEKB x 40 Gain in Luminosity L=8·1035 s-1cm-2 e- 2.3 A
Colliding bunches
Belle II
New IR
e- 2.3 A
New superconducting /permanent final focusing quads near the IP
New beam pipe
& bellows
e+ 4.0 A
Replace short dipoles with longer ones (LER)
Add / modify RF systems for higher beam current
Low emittance positrons to inject
Positron source
Damping ring
Redesign the lattices of HER & LER to squeeze the emittance
New positron target / capture section
Low emittance gun
TiN-coated beam pipe with antechambers
Low emittance electrons to inject
L=8·1035 s-1cm-2
x 40 Gain in Luminosity

12. Luminosity Prospects,Detector Requirements
~50 ab-1 (2022)
~10 ab-1 (2018)
Current B factories
Design L: 8 x 1035 cm-2 s-1
Increased luminosity:
~10-20x higher backgrounds, rad. damage
Increased trigger rates (0.5  200 kHz).
Need to maintain excellent performance, hermeticity.
Significant detector upgrades!
Belle event with increased background overlaid.
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

13. Nishimura - Belle II @ SuperKEKB
The Belle II Detector
RPC m & KL counter:
scintillator + Si-PM
for end-caps
CsI(Tl) EM calorimeter:
waveform sampling
electronics,
pure CsI
for end-caps
7.4 m
3.3 m
1.5 m
4 layers DSSD →
2 layers PXD
(DEPFET) +
4 layers DSSD
7.1 m
Time-of-Flight, Aerogel
Cherenkov Counter →
Time-of-Propagation
counter (barrel),
proximity focusing Aerogel
RICH (forward)
Central Drift Chamber:
smaller cell size,
long lever arm
Belle II Technical Design Report: arXiv:
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

14. Nishimura - Belle II @ SuperKEKB
Vertex Detector
Belle II: Pixels (2 layers) + SVD (4 layers)
Belle: SVD (4 layers)
DSSD strip layers
pixel layers
Vertexing improvements:
~25% Improvement in vertex resolution.
~30% higher KS  ¼+¼- efficiency.
DEPFET Pixel Mockup
Increased sensitivity to b  s ° TCPV:
SCP suppressed by ms / mb in SM.
Enhanced in LR symmetric models.
Currently statistics limited.
Silicon Vertex Detector
Nonresonant KS ¼0 °
Resonant K*0 °
All KS ¼0 °
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

15. Nishimura - Belle II @ SuperKEKB
Central Drift Chamber
longer lever arm
improve resolution of momentum and dE/dx
Vital for “full reconstruction”:
Fully reconstruct “tag” B to determine “signal” B flavor, charge, momentum.
(7.0 GeV)
(4.0 GeV)
Allows measurement of modes with missing energy, neutrinos:
B  K(*) º º
B  ¿ º
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

16. Time-of-Propagation (Barrel PID)
TOP Concept
Example x,t
Hit Pattern
Compact version of detection of internally reflected Cherenkov (DIRC) technique:
Measure internally reflected Cherenkov pattern in x,y,t.
Relies strongly on timing
of detected photons.
Typically separation
between K,¼ is of
order ~100 ps.
90±, 2 GeV
Red - Pion
Blue - Kaon
t° (ns)
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

17. Time-of-Propagation (Barrel PID)
K§, ¼§
Focusing Mirror
MCP-PMTs
Quartz radiator
Compact version of detection of internally reflected Cherenkov (DIRC) technique:
Measure internally reflected Cherenkov pattern in x,y,t.
Significant improvement over Belle threshold aerogel + time-of-flight.
Hamamatsu SL-10
16-channel
Micro-channel plate PMTs
Excellent timing (¾t ~ 40 ps)
Compact, integrated GSa/s waveform digitizing readout:
TOP performance at 3 GeV/c
90%
128-channel
integrated module
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

18. Aerogel RICH (Endcap PID)
Proximity focusing scheme:
Aerogel
Hamamatsu HAPD
Slightly different indices of aerogel stacked  improve Cherenkov angle resolution.
90%
 Excellent PID efficiency over wide momentum range.
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

19. Improved PID Performance
Significant improvement in K/¼ discrimination:
Rare radiative processes:
B  ½0 ( ¼+¼-) °
B  K* ( K+¼-) °
Other physics impact: K¼ CPV puzzle.
Naively, for K+¼0, K +¼- we expect:
¢A = 0.
Current Belle value (EPS 2011):
¢A = § 4¾
…but theoretical uncertainty can be large.
Model independent sum rule:
Gronau,
PLB627, 82
(2005)
current
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

20. Improved PID Performance
Significant improvement in K/¼ discrimination:
Rare radiative processes:
B  ½0 ( ¼+¼-) °
B  K* ( K+¼-) °
Other physics impact: K¼ CPV puzzle.
Naively, for K+¼0, K +¼- we expect:
¢A = 0.
Current Belle value (EPS 2011):
¢A = § 4¾
…but theoretical uncertainty can be large.
Model independent sum rule:
Gronau,
PLB627, 82
(2005)
current
Projected
w/ 50 ab-1
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

21. Electromagnetic Calorimeter
Crystals:
Barrel: reuse existing CsI(Tl).
Endcaps: (possibly staged) upgrade to pure CsI.
 Better performance & radiation hardness.
Readout electronics:
Upgrade to 2 MHz waveform sampling.
Online signal processing.
 Improved energy resolution.
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

22. Nishimura - Belle II @ SuperKEKB
Missing Energy Modes
Belle B  ¿ º [PRD82:071101]
Fully reconstruct one B, measure Emiss
for signal B. Examples:
B  ¿ º
Current ~2.8 ¾ CKM fit tension.
B  h º º
Sets limits on right-handed currents.
Bkg only.
Sig + bkg
Belle B  K*ºº [PRL99:221802]
-- exp. signal (20xBr)
exp. bkg
50 ab-1
W. Altmannshofer et al.,
JHEP 0904, 022 (2009).
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

23. Nishimura - Belle II @ SuperKEKB
KL and ¹ Detector
Endcap:
RPCs  scintillator to tolerate high BG.
14x(75 x-strips, 75 y-strips) per 90± sector.
16,800 total channels w/ waveform sampling readout.
Barrel:
Belle RPCs mostly to be reused.
Inner two layers  scintillator.
Iron plate
Aluminium frame
x-strip plane
y-strip plane
Y strip
X strip
Photon-counting with Hamamatsu MPPCs and waveform sampling readout
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

24. Belle II Physics Program
Belle II provides many opportunities to search for new physics at intensity frontier:
*From Enrico Lunghi’s slides on Wednesday
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

25. Belle II Physics Program
Very broad physics program within Belle II!
“Physics at Super B Factory”, arXiv:
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

26. Nishimura - Belle II @ SuperKEKB
Summary
Super KEKB & Belle II are approved by Japanese government.
Accelerator and detector upgrades are underway.
Belle II Technical Design Report: arXiv:
Planning to collect 50 ab-1 by 2022.
Broad physics program.
More details: arXiv:
~400 members from over 60 institutes in 19 countries:
New members welcome! Visit:
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

27. Nishimura - Belle II @ SuperKEKB
Backup
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

28. Increasing Luminosity for SuperKEKB
Target luminosity (8 x 1035 cm-2 s-2): ~40x KEKB
Beam current
I: beam current
b*: trajectories envelope at IP
xy  (by */ey ) beam-beam parameter
e: beam emittance
σ*: beam size
RL,Rξy: geometrical reduction factors
(crossing angle, hourglass effect)
Beam-beam parameter
Vertical beta IP
E (GeV)
LER/HER
β*y (mm)
β*x (cm)
εx (nm) φ
(mrad)
I (A)
L (cm-2s-1)
KEKB
3.5/8.0
5.9/5.9
120/120
18/24 11
1.6/1.2
2.1 x 1034
SuperKEKB
4.0/7.0
0.27/0.41
3.2/2.5
3.2/1.7
41.5
3.6/2.6
80x1034
Strategies:
Reduce vertical beta function at IP: collide very small, focused beams.
Nano-beam scheme invented by P. Raimondi.
2. Increase beam currents.
sx~100mm, sy~2mm
sx~10mm, sy~60nm
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

29. Nishimura - Belle II @ SuperKEKB
SuperKEKB Parameters
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

30. Nishimura - Belle II @ SuperKEKB
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

31. Nishimura - Belle II @ SuperKEKB
Central Drift Chamber
longer lever arm
improve resolution of momentum and dE/dx
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

32. Missing Energy Modes: B-  ¿ - º
Tension between the global CKM fit and :
Current world ave.
~2.8 ¾ discrepancy
Expectation from CKM fit
Better measurement of B(B  ¿ º) may reveal source of the tension.
Tag-side information vital when ¸2 º’s in
final state! Signal is seen as zero excess EECL.
Bkg only.
Sig + bkg
Example w/ semileptonic tag, 657M BB
PRD82: (2010)
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

33. Nishimura - Belle II @ SuperKEKB
B  ¿ º at Belle II
Also sensitive to new physics:
In type-II Two-Higgs Doublet Model (THDM), the SM branching fraction of B-  ¿ - º is modified:
Belle II discovery region with 5 ab-1
Assumes improvements in theory values:
5% |Vub| error
5% fB error
5 ¾ discovery region
current 95% exclusion
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

34. Nishimura - Belle II @ SuperKEKB
B  ¿ º at Belle II
Also sensitive to new physics:
In type-II Two-Higgs Doublet Model (THDM), the SM branching fraction of B-  ¿ - º is modified:
Belle II discovery region with 50 ab-1
Assumes improvements in theory values:
2.5% |Vub| error
2.5% fB error
5 ¾ discovery region
current 95% exclusion
*Does not yet account for improvements in full-recon efficiency. Recently work suggests O(2x) improvements.
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB

35. Nishimura - Belle II @ SuperKEKB
B  D* ¿ º
CIPANP - June 3, 2012
Nishimura - Belle SuperKEKB