1. Flavor Physics at e+e- Colliders
Boštjan Golob
University of Ljubljana/Jožef Stefan Institute
& Belle/Belle II Collaboration
Status & Plans
Examples of measurements
Summary
University
of Ljubljana
“Jožef Stefan”
Institute
Alps 2017:
an Alpine LHC
Physics Summit

2. Status e+e- Accelerators? PEP-II LEP(2) BEPC-II SuperKEKB VEPP-4M
Inclusive
Neutrals
Emiss
Summary
Status
e+e- Accelerators?
PEP-II
LEP(2)
BEPC-II
SuperKEKB
VEPP-4M
DANE
CESR-C
VEPP-4M
DANE
Eastbound →
considering acc. relevant (subjective) to this talk → Far East

3. Status Accelerator “SuperKEKB” e- Belle 2 e+ SuperKEKB:
Inclusive
Neutrals
Emiss
Summary
Status
Accelerator
“SuperKEKB”
Tokyo (40 mins by Tsukuba Exps)
SuperKEKB:
e- (HER): 7.0 GeV
e+ (LER): 4.0 GeV
ECMS=M(U(4S))c2
(→BB)
[M(U(1S))c2 ,M(U(6S))c2]
dNf / dt = s(e+e-→f)L
L =8x1035 cm-2 s-1
LER
HER e-
Belle 2 e+

4. Status Accelerator “BEPC - II” BEPC-II: ECMS=2.0 – 4.6 GeV
Inclusive
Neutrals
Emiss
Summary
Status
Accelerator
“BEPC - II”
BEPC-II:
ECMS=2.0 – 4.6 GeV
M(y(3770))c2, M(y(4040))c2
(→DD) (→DD*)
L =1x1033 cm-2 s-1

5. Status Super KEKB luminosity planning 5 ab-1 20 ab-1 Phase 1: w/o QCS
Inclusive
Neutrals
Emiss
Summary
Status
Super KEKB luminosity planning
5 ab-1
20 ab-1
Phase 1:
w/o QCS
w/o Belle 2
Phase 2:
w/ QCS
w/ 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

6. Status Belle 2 planning Final focusing superconducting magnets
Inclusive
Neutrals
Emiss
Summary
Status
Belle 2 planning
Final focusing superconducting magnets
150 GeV Cosmic ray in ECL
BEAST PHASE I: Simple background
commissioning
detector
(diodes, TPCs,
crystals). No final
focus (i.e. no
luminosity, single
beam background
studies possible).
BEAST PHASE II: More elaborate inner background commissioning detector & full Belle II outer detector.
Superconducting final focus, no vertex detectors.
Physics Running
Feb – Jun 2016
Oct 2017 –
Jan 2018
Oct 2018 →

7. Belle 2 Roll-in (April 11th)
Status
Inclusive
Neutrals
Emiss
Summary
Status
Belle 2 Roll-in (April 11th)
to beam lines
CDC
Oct 2016

8. Belle 2 Roll-in (April 11th)
Status
Inclusive
Neutrals
Emiss
Summary
Status
Belle 2 Roll-in (April 11th)
after
1 minute
30 seconds

9. Belle 2 Roll-in (April 11th)
Status
Inclusive
Neutrals
Emiss
Summary
Status
Belle 2 Roll-in (April 11th)

10. Properties of e+e- Colliders (as compared to LHC) low energy
Status
Inclusive
Neutrals
Emiss
Summary
Status
Properties of e+e- Colliders
(as compared to LHC)
low energy
D. Curtin et al., arXiv:
10-1
10-2
10-3
e: gA‘ coupling
A. Bondar et al., Belle2-note-ph

11. Properties of e+e- Colliders (as compared to LHC) low energy
Status
Inclusive
Neutrals
Emiss
Summary
Status
Properties of e+e- Colliders
(as compared to LHC)
low energy
low trigger rate / Event size
(30 kHz 1st level, 5 kHz high level; 300 kB event size)
low multiplicity (O(10))

12. Properties of e+e- Colliders (as compared to LHC) low energy
Status
Inclusive
Neutrals
Emiss
Summary
Status
Properties of e+e- Colliders
(as compared to LHC)
low energy
low trigger rate / Event size
(30 kHz 1st level, 5 kHz high level; 300 kB event size)
low multiplicity (O(10))
good hermiticity
specific methods for
full event
reconstruction
Missing E
(n)
Btag
fully (partially) reconstruct Btag;
reconstruct h from e.g. Bsig→hnn
or Bsig→ t(→ hn)n;
no additional energy in EM calorim.;
signal at EECL~0;
Btag full reconstruction (NeuroBayes)
Bsig
Bsig → tn
candidate
event

13. Plans Ee+beam boost Lumi ratio for same sensitivity B → fKs B → J/yKs
Introduction
Inclusive
Plans
Neutrals
Emiss
Summary
Plans
Lumi ratio for same sensitivity
B → fKs
B → J/yKs
Belle II
B-tagged
LHCb
Hadronic
B → tn
Belle
Belle 2
Ee+beam
boost
Relative yield increase
Ee-beam from U(4S) mass
B. Golob, K. Trabelsi, P. Urquijo, Belle2-note-ph
Belle 2: improved KS reconstr.;
improved hadr. B tagging;
LHCb: s s;
run 2 50% less eff. for hadronic triggers
than run 1;
run 3 increase eff. for hadr. triggers by
2x w.r.t. run 1;
LHCb EPJC 73, 2373

14. BEPC-II / BES-III planning
Introduction
Inclusive
Plans
Neutrals
Emiss
Summary
Plans
BEPC-II / BES-III planning
part of existing data sets:
proposal until 2020 (3 years):
1010 J/y
3 fb GeV (Lc)
5 fb GeV (XYZ)
data lumin.[fb-1] year
y(3770) /11
y(4040)
4.18 GeV

15. Subjects Methods and processes where Belle 2 can provide
Introduction
Inclusive
Neutrals
Emiss
Summary
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), B(B → Xu l n)...
(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:
Physics of 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
B. O’Leary et al., arXiv:
P. Urquijo, BE LLE2-NOTE- PH
Belle I I - LHCb measurement
extrapolation comparisons
Ed. A.J. Bevan, B. Golob, Th. Mannel, S. Prell, and B.D. Yabsley,
Eur. Phys. J. C74 (2014) 3026

16. l =e,m Test of LFU Missing energy B  D*tn
Introduction
Inclusive
Neutrals
Emiss
Summary
Missing energy
B  D*tn
R(D(*))= B(B  D*tn) / B(B  D* l n)
R(D)SM=0.300 ±0.008
R(D*)SM =0.252 ±0.003
use NN with M2miss,
Evis, cosqB-D* l sig.
data sample with
low M2miss used to
fit the background
contribution
Belle, PRD 94, , 700 fb-1
l =e,m Test of LFU
H. Na et al., Phys.Rev.D 92, (2015)
23123
D* tn
S.Fajfer et al., Phys.Rev.D85(2012)
280057
D* l n
signal is to the
right →
NN output for data
with M2miss >
0.85 GeV2

17. Missing energy B  D*tn R(D*)=0.302±0.030±0.011 current
Introduction
Inclusive
Neutrals
Emiss
Summary
Missing energy
B  D*tn
R(D*)=0.302±0.030±0.011
Belle, PRD 94, , 700 fb-1
current
Belle II 5 ab-1
Belle II 50 ab-1
s(R(D(*)))/R(D(*))[%]
3.5 5 ab-1
Nm/Ne (Brm/Bre)2 semil. tag
Nm/Ne Brm/Bre had. tag
sstat(e/m)  5%
sstat(t/e,m)  11%
(semil. tag)
5 20 ab-1
L [ab-1]

18. Neutrals CPV in b → sqq DS=sin2f1eff -sin2f1 41 new phases in MSSM
Introduction
Inclusive
Neutrals
Emiss
Summary
Neutrals
CPV in b → sqq
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
B → J/y Ks
for comparison
DS=sin2f1eff -sin2f1
B → KsKsKs
0.007
B → f Ks
0.045
B → f Ks
B → h‘ Ks
0.020
0.010
P. Urquijo,
Belle2-note-ph
B. Golob, K. Trabelsi, P. Urquijo,
Belle2-note-ph
0.02

19. Neutrals Exotic states g ISR X(3872) discovery by Belle (2003)
Introduction
Inclusive
Neutrals
Emiss
Summary
Neutrals
Exotic states
Belle II / BES III
g ISR
X(3872) discovery by Belle (2003)
(meson molecule?)
clear that exotic ( ≠ qq, qqq) states exist
PQ discovery by LHCb (2015)
Belle II & BES III can produce those
clearly and abundantly
e.g. Y states in e+e-
(quark gluon hybrids?)
Y(4260); BESIII 0.8 fb-1 at Ecms=4.26 GeV
→ J/y p+p-
studies of properties (combined with
LQCD?) may reveal nature of exotic states e+ Y e-
Zc+(3900)
BESIII, PRL 110, (2013)
M. Padmanath et al., PRD92, (2015)

20. Summary complementarity is an absolute must in intensity frontier
Introduction
Inclusive
Neutrals
Emiss
Summary
Summary
complementarity is
an absolute must in
intensity frontier
need to do some
(re)analysis of Belle
data
hardly waiting to start
datataking with
Belle II
B. Golob, K. Trabelsi, P. Urquijo, Belle2-note-ph ?

21. Beast phase 1 Beast phase 1 background drop backgrounds in ECL
Introduction
Inclusive
Neutrals
Emiss
Summary
Beast phase 1
Beast phase 1
background
drop
backgrounds in ECL
responding to colimator
settings
colimator
closing
Touschek background
(  1/sy)
reason for lower boost

22. Semil. tagging B  tn, hnn, Xctn,... l± possible to reconstruct
Introduction
Inclusive
Neutrals
Emiss
Summary
Semil. tagging
B  tn, hnn, Xctn,...
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

23. LFU/B →K* l l B  K*l l R(K*)= N(B  K*mm) N(B  K*ee)
Introduction
Inclusive
Neutrals
Emiss
Summary
LFU/B →K* l l
B  K*l l
R(K*)=
N(B  K*mm)
N(B  K*ee)
approximate stat.
uncertainty on
R(K*), very roughly
Belle, 0.7 ab-1
Belle II, 10 ab-1
Belle, arXiv: , 700 fb-1

24. LFU charm Ds  l n s(X)/X[%] RDst/m Br(Ds → mn) Br(Ds → tn)
Introduction
Inclusive
Neutrals
Emiss
Summary
LFU charm
s(X)/X[%]
Ds  l n
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

25. Inclusive l± 1.26 GeV < E < 2.20 GeV B  s(+d) g g K : g p
Introduction
Inclusive
Neutrals
Emiss
Summary
Inclusive
B  s(+d) g
experimental challenge:
huge bkg;
only g reconstructed in the signal side
continuum
p0  gg
h  gg
b  sg g
Bsig
Btag Xs
l± 1.26 GeV < E < 2.20 GeV
Belle, PRL103, , (2008), 605 fb-1
different method: hadronic tagging (= full
reconstruction of Btag);
reduction of system.uncertainty on the account
of lower efficiency (ehad ~ 0.5%); p
Bsig
Btag g Xs K : 5%
B. Golob, K. Trabelsi, P. Urquijo,, Belle2-note-ph

26. Inclusive b  d g s(Br(dg)) = (±20±22)10-7 high Xd mass region
Introduction
Inclusive
Neutrals
Emiss
Summary
Inclusive
b  d g
within SM: Br(B → dg) / Br(B → sg) =(3.8 ±0.5) 10-2
(ratio can be used to determine |Vtd/Vts|)
Br(B → sg) = 3.410-4
Br(B → dg) should be measured with an accuracy of ~210-6
sum of exclusive modes: s(Br(dg)) = (±3±1) low Xd mass region
s(Br(dg)) = (±20±22) high Xd mass region
T. Hurth et al., Nucl.Phys. B704, 56 (2005)
BaBar, PRD82, (2010), 0.4ab-1
largest syst. uncertainty:
B → s g bkg.;
missing (>= 5 body) modes;
significant improvement necessary
Belle/Belle 2 full simulation:
Belle 2
15%
B0 K*(Kp)g, B0  r(pp)g,
DE= EB* - Ebeam

27. Inclusive B → sg direct CPV b → sg Semi-inclusive, sum of many
Introduction
Inclusive
Neutrals
Emiss
Summary
Inclusive
B → sg
direct CPV
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
HFAG, 2014
SM: ACP ~ (0.44± )%
T. Hurth et al., Nucl.Phys. B704, 56 (2005)
5x10-3

28. Neutrals DCPV puzzle: tree+penguin processes, B+(0)→K+p0(-)
Introduction
Inclusive
Neutrals
Emiss
Summary
Neutrals
B0 →K+p-
DCPV puzzle:
tree+penguin processes, B+(0)→K+p0(-)
DAKp= A(K+p -)- A(K+p 0)= ±0.028
Belle, Nature 452, 332 (2008), 480 fb-1
IKp B (B0 → K+p -)
Mbc
M. Gronau, PLB627, 82 (2005);
D. Atwood, A. Soni, PRD58, (1998)
s(ACP(KSp+))
Belle 2 K0p0
50 ab-1
s(ACP(K-p+))
B. Golob, K. Trabelsi, P. Urquijo,, Belle2-note-ph

29. Summary (Belle perspective)
Introduction
Inclusive
Neutrals
Emiss
Summary
Summary (Belle perspective)
B. Golob, K. Trabelsi, P. Urquijo, Belle2-note-ph

30. Introduction Ee+beam Lumi ratio for same sensitivity B → fKs B → J/yKs
Inclusive
Neutrals
Emiss
Summary
Introduction
Lumi ratio for same sensitivity
B → fKs
B → J/yKs
P. Urquijo,
Belle2-note-ph
B → tn
Belle
Belle 2
Ee+beam
Ee-beam from U(4S) mass
B. Golob, K. Trabelsi, P. Urquijo, Belle2-note-ph
Belle 2: improved KS reconstr.;
improved hadr. B tagging;
LHCb: s s;
run 2 50% less eff. for hadronic triggers
than run 1;
run 3 increase eff. for hadr. triggers by
2x w.r.t. run 1;
Belle II
B-tagged
LHCb
Hadronic
Relative yield increase
LHCb EPJC 73, 2373

31. Early running Dark matter Early running
Introduction
Inclusive
Neutrals
Emiss
Summary
Early running
Early running
need time for calibration of detectors
at U(4S);
measurements not requiring sophisticated
PID and/or vertex determination;
maximize impact on existing data samples
(e.g. U(3S));
A. Bondar et al., Belle2-note-ph
Dark matter
e+e-  g A‘ g cc
(mc < mA‘/2)
single g trigger required;
simplified: single g, Eg > Ecut;
high bkg, low e
high trigger rate
Ecut
main backgrounds:
e+e-  g e+e-
e+e-  gg
e: gA‘ coupling

32. Missing energy B  tn, hnn, ... B  tn
Introduction
Inclusive
Neutrals
Emiss
Summary
Missing energy
B  tn, hnn, ...
fully (hadron tag) or partially (semil.tag) reconstruct Btag;
Nsig=62 ± 24
hadronic tag
B  tn
main syst. is reducible: bkg. ECL shape, e Btag)
B(B+ →t+n)=(0.72 ± 0.26 ± 0.11) ∙10-4
Belle, PRL110, (2013), 700 fb-1
Nsig=222 ± 50
B(B+ →t+n)=(1.25 ± 0.28 ± 0.27) ∙10-4
Belle, arXiv: , 700 fb-1
semil. tag

33. Missing energy B+  tn projected accuracy on B(B+ →t+n) B →K(*)nn
Introduction
Inclusive
Neutrals
Emiss
Summary
Missing energy
B+  tn
projected accuracy on B(B+ →t+n)
corresponding |Vub| uncertainty
(experimental):
semil. tag, 50 ab-1: 4.5%
hadr. tag, 50 ab-1: 3.5%
B. Golob, K. Trabelsi, P. Urquijo,, Belle2-note-ph
B →K(*)nn
Br‘s expected to be „measured“ to 30%
5x10-6
approx. expected
50 ab-1 SM
W. Altmannshofer et al., arXiv:

34. SuperKEKB SuperKEKB Nano beams design (P. Raimondi)
Introduction
Inclusive
Neutrals
Emiss
Summary
SuperKEKB
SuperKEKB
sx~100mm,sy~2mm
sx~10mm,sy~60nm
Nano beams design
(P. Raimondi) e- e+
∫L dt
[ab-1]
b*: beta-function (trajectories
envelope) at IP
xy: beam-beam parameter
∫L dt=50 ab-1 ( )
small by*
large xy  (by*/ey)  small ey
hourglass effect  small bx*
increase I
∫L dt=10 ab-1 ( )
current B factories L
[s-1cm-2]
design L=8·1035 s-1cm-2
magnet installation
for SuperKEKB;
Being built on schedule

35. Introduction SuperKEKB e+ e-
Inclusive
Neutrals
Emiss
Summary
Introduction
SuperKEKB
Belle II e+
New IR
New superconducting /permanent final focusing quads near the IP
New beam pipe
& bellows
Replace short dipoles with longer ones (LER) e-
Add / modify RF systems for higher beam current
Low emittance positrons to inject
Redesign the lattices of HER & LER to squeeze the emittance
Positron source
Damping ring
Low emittance gun
Low emittance electrons to inject
New positron target / capture section
TiN-coated beam pipe with antechambers

36. Introduction Damping ring tunnel: built!
Inclusive
Neutrals
Emiss
Summary
Introduction
Installation of 100 new long LER bending magnets done
Installation of HER wiggler chambers in Oho straight section is done.
Damping ring tunnel: built!

37. BF, KEKB @ KEK / PEPII @ SLAC
Introduction
Inclusive
sin2f1
Neutrals
Emiss
General requirements
Accelerator
Accelerator
BF, KEK / SLAC
Belle Ldt  1020 fb-1
BaBar Ldt  550 fb-1
u,d b
Bd0, B+ b
energ. threshold
for BB production b
u,d
U(4S)
s(e+e-→hadrons) [nb]
Bd0, B-
“on resonance” production
e+e- → U(4S) → Bd0Bd0, B+B-
s(e+e- → BB)  1.1 nb (~109 BB pairs Belle)
s(e+e- → c c)  1.3 nb (~1.3x109 XcYc pairs Belle)
”continuum” production, qq, ll, tt g* f e- e+
(hadrons)
(hadrons)
running at Y(nS), e.g. Y(5S) (BsBs)