1. CPV & LFV/LFU @ Belle II Introduction (Examples of...) LFU LFV CPV
Boštjan Golob
University of Ljubljana/Jožef Stefan Institute
& Belle/Belle II Collaboration
Introduction
(Examples of...)
LFU
LFV
CPV
Summary
University
of Ljubljana
“Jožef Stefan”
Institute
Heavy Flavor 2016
Quo Vadis?

2. “SuperKEKB” Accelerator
Introduction
“SuperKEKB” Accelerator
Lumi ratio for same sensitivity
e- (HER): 7.0 GeV
e+ (LER): 4.0 GeV
ECMS=M(U(4S))c2
dNf/dt = s(e+e-→f) L
L =8x1035 cm-2 s-1
B → fKs
B → J/yKs
B → tn
Belle
Belle 2
Ee+beam
5 ab-1
20 ab-1
Phase 1:
w/o QCS, Belle 2
Phase 2:
w/ QCS, Belle 2
(no VXD)
Phase 3:
full Belle 2
Phase 1
Phase 2
Phase 3
QCS, Belle 2
VXD
35 ab-1
50 ab-1

3. Methods and processes where Belle 2 can provide
Subjects
Methods and processes where Belle 2 can provide
important insight into NP complementary to other experiments:
Emiss:
B(B→ tn), B(B → Xctn), B(B → hnn),...
(Semi)Inclusive:
B(B → sg), ACP(B → sg), B(B → sll ), ...
Neutrals:
S(B → KSp0g), S(B → h’ KS), S(B → KSKSKS), B(t → mg), B(Bs → gg), ...
Detailed description of physics program at Belle 2 in:
The Physics of the B Factories
A.G. Akeroyd et al., arXiv:
B.G.,, K, Trabelsi, P. Urquijo, BE LLE2-NOTE- PH
Impact of Belle II on Flavor Physics
Ed. A.J. Bevan, B. Golob, Th. Mannel, S. Prell, and B.D. Yabsley,
Eur. Phys. J. C74 (2014) 3026
P. Urquijo, BE LLE2-NOTE- PH
Belle I I - LHCb measurement
extrapolation comparisons
B. O’Leary et al., arXiv:

4. LFU/Missing energy B  tn, hnn, Xctn,... l possible to reconstruct
events with n‘s;
fully (partially) reconstruct
Btag;
reconstruct h± from Bsig;
no additional energy in
EM calorim.;
signal at EECL~0;
Partial reconstruction (semileptonic tagging):
etag~1%
Missing E
(n)
Btag
Bsig
Bsig → tn
candidate
event l
Bsig
Btag
D*± n

5. l =e,m LFU/Missing energy B  D*tn R(D(*)) R(D)SM=0.300 ±0.008
use NN with M2miss,
Evis, cosqB-D* l sig.
data sample with
low M2miss used to
fit the background
contribution
l =e,m
Belle, arXiv: , 700 fb-1
H. Na et al., Phys.Rev.D 92, (2015)
S.Fajfer et al., Phys.Rev.D85(2012)
signal is to the
right →
NN output for data
with M2miss >
0.85 GeV2

6. LFU/Missing energy B  D*tn R(D*)=0.302±0.030±0.011
Belle, arXiv: , 700 fb-1
s(R(D*))/R(D(*))[%]
HFAG,
4s discrepancy with SM
3.5 s from 5 ab-1
5 s from 20 ab-1
L [ab-1]

7. LFU/Missing energy Ds  l n inclusive D meson reconstr.
cc → Dtag Ds* (→ Ds g) Kfrag Xfrag
Mmiss(Dtag gKfragXfrag) = MDs
Ds → mn
Mmiss(Dtag gKfragXfrag m) = Mn
inclusive reconstruction of Ds
Belle, JHEP09, 139 (2013), 900 fb-1
reconstruction of Dsmn

8. LFU/Missing energy Ds  l n Ds → tn EECL
Belle, JHEP09, 139 (2013), 900 fb-1

9. LFU/Missing energy Ds  l n s(X)/X[%] RDst/m Br(Ds → mn) Br(Ds → tn)
B.G.,, K, Trabelsi, P. Urquijo, BE LLE2-NOTE- PH
RDst/m
Br(Ds → mn)
Br(Ds → tn)
RDst/m= Br(Ds → tn) / Br(Ds → mn)
RDst/m=10.73 ± 0.69 ± 0.55
(RDst/m)SM= ± 0.031
Belle, JHEP09, 139 (2013), 900 fb-1
L [ab-1]
n.b.: s(R(D*))/R(D(*)) ab-1

10. LFU/B →K* l l B  K*l l angular analysis B  K*mm B  K*ee Nsig=118±12
Belle, arXiv: , 700 fb-1
P5‘
LHCb, JHEP 1308 (2013) 131

11. LFU/B →K* l l B  K*l l R(K*)= N(B  K*ee) approximate stat.
N(B  K*mm)
approximate stat.
uncertainty on
R(K*)
Belle, arXiv: , 700 fb-1
L [ab-1]

12. LFV/t → m g e t → m g e m g p n t e kinematic variables
Belle, PLB66, 16 (2008), 535 fb-1
kinematic variables
for signal isolation:
DE=ECM(mg)-ECM(beam)
Minv=m(mg)
main background from
ee→ t(mnn) t(pn) gISR
BrUL  1/ √L
signal m g p n t e
expected sig.
B 5x10-7
background e

13. LFV/t → m g t → m g B(t → m g) < 4.4 ·10-8
simplified (1D) toy MC
UL90%
B(t → m g)
[10-8] 4 2 1
0.4
0.2
t → m g
Belle, PLB66, 16 (2008), 535 fb-1
 1/L
B(t → m g) < 4.4 ·10-8
decays t → 3l, l h0 background free
 1/√L
L[ab-1]
B.G.,, K, Trabelsi, P. Urquijo,
BE LLE2-NOTE- PH

14. CPV/B → sqq b → sqq t-dependent CPV DS=sin2f1eff -sin2f1
- some uncertainties cancel in DS
(vtx reconstr., flavor tag, likelihood fit) ;
- better KS eff. with vtx hits - larger vtx radius,
30%);
- vtx reconstr. improved with better tracking;
41 new phases in MSSM
DS=sin2f1eff -sin2f1
s(sin2f1(J/yKs))
s(s)
0.007
3Ks
fKs
P. Urquijo,
Belle2-note-ph
0.045
h‘Ks
s(sin2f1(fKs))
0.020
J/yKs
0.02
B. Golob, K. Trabelsi, P. Urquijo,
Belle2-note-ph

15. B → K* (→KSp0)g t-dependent CPV CPV/B → sg SM:
t-dependent decays rate of B → fCP;
S and A: CP violating parameters
B → K* (→KSp0)g
t-dependent CPV
SM:
SCPK*g  -(2ms/mb)sin2f1  -0.04
Left-Right Symmetric Models:
SCPK*g  0.67 cos2f1  0.5
SCP(Ksp0g) = ±0.31 ±0.07
ACP(Ksp0g) = ±0.20 ±0.06
for m(Ksp0) < 1.8 GeV (mainly K*g)
D. Atwood et al., PRL79, 185 (1997)
B. Grinstein et al., PRD71, (2005)
Belle, PRD74, (2006), 500 ab-1

16. B → K* (→KSp0)g t-dependent CPV CPV/B → sg SCPKsp0g = -0.15 ±0.20
ACPKsp0g = ±0.12
HFAG
Summer 2012
HFAG, Summer’12
5 ab-1
s(SCPKsp0g)= @ 5 ab-1
0.04 @ 50 ab-1
(~SM prediction)
50 ab-1
B.G.,, K, Trabelsi, P. Urquijo, BE LLE2-NOTE- PH
for B→ r0g ~2x larger uncertainty

17. direct CPV DCPV/B → sg B → s(+d)g b → sg DD: difference between
Semi-inclusive, sum of many exclusive
states: all flavor specific final
states;
<D>: average dilution due to
flavour mistag, 1
DD: difference between
flavour mistag for
b and b, << 1
Adet: detector induced
asymmetry
BaBar, PRL101, (2008),350 fb-1
b → sg
Adet: careful study of K/p asymmetries in (p,qlab)
using D decays or inclusive tracks from
fragmentation;
lots of work on system.,  few 10-3 exp. sensitivity

18. DCPV/B → sg B → sg direct CPV SM: ACP ~ (0.0044±0.00240.0014)%
Inclusive, g recontruction only;
bkg. suppression (kinematic event shape
variables);
semileptonic tagging;
Similar sensitivity expected for semi-inclusive
& fully inclusive
Belle, PRL114, (2015), 700 fb-1
HFAG, 2014(?)
SM: ACP ~ (0.0044± )%
T. Hurth et al., Nucl.Phys. B704, 56 (2005)
sum of excl.
incl.
5x10-3

19. Summary LFU: important measurements to be performed already
with 5 – 10 ab-1 ( )
LFV:
50 ab-1 (2023) needed to reduce existing limits by > 10
CPV:
in rare modes ab-1 ( ) needed to reach
SM expectations

20. Summary

21. Summary