Transcript PowerPoint プレゼンテーション

New Physics Search in B Decays
(Leptonic and Neutrino Modes)
& Super B Factory
Toru Iijima
Nagoya University
October 17, 2006
Heavy Quark and Leptons 2006 Munich
Talk Outline + Appology
Introduction
Bln (tn, mn, en, lng)
Bll (ee, mm, tt, llg)
BK(*)nn, nn
Super KEKB
Summary
Appology:
Due to limited time, some of
them cannot be mentioned
or have to be put in backup .
2
Introduction
 If New Physics found at LHC at TeV scale, they must
appear in loops as well and change amplitudes.
 It is easier to see the effects when SM amplitudes are
small (or zero).
Rare Decays !!
 B decay has many patterns to test the effects.
Box
Penguin

W

n

t


n
b
g, Z
b
Annihilation
s
W
b
W
W
t
s
u
Higgs mediation
3
Hunting Rare Decays
In 1993…
CLEO
First evidence of
BK*g
PRL 71, 674 (1993)
4
Hunting Rare Decays
 High luminosity
Evidence of Btn
 Good detector (PID, vertex…)
 Analysis techniques
Observation of bdg
– qq background suppression
FB asymmetry in BK* l+l– Fully reconstructed tag
Direct CPV in B0K+p
Beginning of B->fK0 saga
Observation of BK l+ lCPV in B decay
Success of B factories brought rare B decays in
leptonic and neutrino modes on the stage !
5
Bln
 Proceed via W annihilation in the SM.
 SM Branching fraction
Br(tn)=1.6x10-4
Br(mn)=7.1x10-7
Br(en)=1.7x10-11
Provide
fB|Vub|
 In two Higgs doublets model, charged Higgs exchange interferes
with the helicity suppressed W-exchange.
2
 mB2

Br = BrSM  rH , rH =  1 - 2 tan2β 
 mH

 If mn is also measured, lepton
universality can be tested.
 SUSY correction etc.
6
Full Reconstruction Method
 Fully reconstruct one of the B’s to tag
– B production
– B flavor/charge
– B momentum
B
e
(8GeV)
e+(3.5GeV)
Υ(4S)
p
B
Decays of interests
BXu l n,
BK n n
BDtn, tn
full (0.1~0.3%)
reconstruction
BDp etc.
Single B meson beam in offline !
Powerful tools for B decays w/ neutrinos
7
Btn Analysis
 Extra neutral energy in calorimeter EECL
– Most powerful variable for separating signal and background
– Total calorimeter energy from the neutral clusters which are not
associated with the tag B
Minimum energy threshold


Barrel : 50 MeV
For(Back)ward endcap : 100(150) MeV
Zero or small value of EECL arising only
from beam background
Higher EECL due to additional neutral
clusters
MC includes overlay of random trigger
data to reproduce beam backgrounds.
8
The First Btn Evidence
 The final results are deduced by unbinned likelihood fit
to the obtained EECL distributions.
Signal +
background
S : Statistical Significance
Background
Btn
Signal
Observe 17.2 +5.3
events in the
- 4.7
signal region.
Significance decreased to 3.5 s
after including systematics
Signal shape : Gauss + exponential
Background shape : second-order polynomial
+ Gauss (peaking component)
9
Results (Br & fB Extraction)
 Measured branching fraction;
+0.56
Br B  tn   1.79 -0.49
+0.46
-0.51
-4
×10

 Product of B meson decay constant fB and CKM
matrix element |Vub|
+1.6
fB Vub = 10.1 -1.4
+1.3
-1.4
-4
×10
GeV

 Using |Vub| = (4.39  0.33)×10-3 from HFAG
fB = 0.229
GeV
+0.036 +0.034
-0.031 -0.037
16% = 14%(exp.) + 8%(Vub)
15%
fB = 216  22 MeV
[HPQCD, Phys. Rev. Lett. 95, 212001 (2005) ]
10
Correction to the FPCP06 result
 Error in the efficiency calculation.
– Due to a coding error, the efficiency quoted in the 1st Belle
preliminary result was incorrect.
 Treatment of the peaking background component.
– Peaking component is subtracted for the central value.
– Re-evaluate its systematic uncertainty.
 The data plots and event sample are unchanged. However, fB and the
branching fraction must be changed.
0.46
0.560.39
0.490.46
0.51
0.340.18
0.280.16
New value
BF( B t nt )  (1.79
) 104
FPCP04
result
BF(B t nt )  1.06
104
The revised paper has been resubmitted, and posted
as hep-ex/0604018v2.
11
Btn Search @ Babar
 Babar searches for in a sample of 324x106 BB events
Reconstruct one B in a semileptonic final state BDlnX
DK p, K p p p, K p p, Ks p p (X=g, p from D*0 is not explicitly
reconstructed)




Require lepton CM momentum > 0.8 GeV
Require that -2 < cosqB-D0l < 1
Parent B energy and momentum are determined from the beam energy
Tagged B reconstruction efficiency ~0.7%

 Discriminate signal from
background using Eextra
lepton is identified in the
4 decay modes
t
12
Btn Search @ Babar (cont.)
 Observed excess is not significant yet (1.3s), and set a
limit on the branching fraction and quote a central value.
Babar preliminary
Deduced fB |Vub|
13
Constraints on Charged Higgs
+0.56
Brexp = (1.79 -0.49
) ×10-4
+0.46
-0.51
These regions are excluded.
BrSM = (1.59 ± 0.40) ×10-4
fB from HPQCD
|Vub| from HFAG
2
 mB2
2 
rH =  1 - 2 tan β 
 mH

Brexp

=1.13 ± 0.53
BrSM
Much stronger constraint than
those from energy frontier exp’s.
14
Future Prospect: Btn
 Br(Bt n) measurement:
More luminosity help to reduce both stat. and syst. errors.
– Some of the syst. errors limited by statistics of the control sample.
 |Vub| measurement: < 5% in future is an realistic goal.
 fB from theory: ~10% now  5% ?
My assumption
Lum.
DfB(LQCD) = 5%
DB(Btn)
exp
D|Vub|
414 fb-1
36%
7.5%
5 ab-1
10%
5.8%
50 ab-1
3%
4.4%
If D|Vub| = 0 & DfB = 0
5ab-150ab-1
Br(Btn)/Dmd to cancel fB ?
G.Isidori&P.Paradisi, hep-ph/0605012
15
Bmn, en
 BaBar @ 208.7fb-1
 Belle @ 140fb-1
w/ fully reconstructed tag;
BD(*) X.
monoenergetic e or m
recoiling against Btag
w/ “inclusive ” reconstruction
of the companion B.
Nobs = 0 in the signal box.
Br(B  en ) < 7.9 ×10
-6
Br(B  mn ) < 6.2 ×10
@90%C.L.
-6
Br(B  en ) < 5.4 ×10-6 (60fb-1 )
Br(B  mn ) < 2.6 ×10-6 (140fb-1 )
@90%C.L.
16
Future Prospect: Bmn
 Bmn is the next milestone decay mode.
 Measurements will offer a cross check to the results
obtained by Bt n.
– fB|Vub| determination.
– Test the lepton universality.
– Inclusive-recon method has
high efficiency but poor S/N.
limit  1/ L
– Hadronic tag will provide very
clean and ambiguous signals,
but very low efficiency.
limit  1/L
Standard Deviation
 Method?
K.Ikado at BNM2006
Extrapolation from the
present Belle analysis
(inclusive-recon.)
3s at 1.3ab-1
5s at 3.7ab-1
Luminosity (ab-1)
See also talk by Robertson
at CERN flavour WS (May 2006)
17
B0l+l-
l
 Proceeds via box or penguin annihilation
SM Branching fractions
d
l
Br(Bd0  e + e- ) ~ 10-15
l
Br(Bd0  m + m - ) ~ 10-10
Br(Bd0  nn ) = zero
l
d
Flavor violating channel (B0  e +m –, etc.) are forbidden in SM.
 New Physics can enhance the branching
fractions by orders of magnitude.
ex.) loop-induced FCNC Higgs coupling
b
d
Note:
Br(Bs 
Br(Bd 
25
300
Btt requires full-reco. tag.
2
Br(B  tt )  mτ 
= 
Br(B  mm )  mμ 
A0,H0, h0
Present CDF limit;Br(Bsmm)
< 1x10-7 (95%CL) is equivalent
to Br(Bsmm) < 4x10-9.
2
)  Vts 
=

)  Vtd 
tan6β

mA4


18
B0l+l- (e+e-,m+m-,e+m-)
Signal regions
e+e–
Events observed
m+m–
111 fb-1
e-m+
78 fb-1
B(B0  e+e–) < 6.1 × 10-8 (90%CL)
B(B0  m+m–) < 8.3 × 10-8 (90%CL)
B(B0  e+ m–) < 18 × 10-8 (90%CL)
Phys. Rev. Lett. 94, 221803 (2005)
B(B0  e+e–) < 1.9 × 10-7 (90%CL)
B(B0  m+m–) < 1.6 × 10-7 (90%CL)
B(B0  e+ m–) < 1.7 × 10-7 (90%CL)
Phys. Rev. D 68, 111101 (2003)
780 pb-1
B(B0dmm) < 2.3×10-8 (90% CL)
It would be interesting to see results with more data.
What about U(5S) data at Super-B ?
19
B0llg (BaBar@ 292fb-1)





320 M BB events
0.3 < mll < 4.9 (4.7) GeV for eeg (mmg)
Background from J/y, y (2S) decay (leptons) or p0 decay (g)
Reject qq background event shape in a Fisher discriminant
Observe 0 (3) events in the signal box in electron (muon) events
e+ e-g
m+ m-g
B(B0  e+e-g) < 0.7 × 10-7 (90%CL)
B(B0  m+m-g) < 3.4 × 10-7 (90%CL)
Babar preliminary
20
BK(*) n n (bs w/ two n’s)
 BK(*)nn proceeds via one-loop radiative penguin and box diagrams.
SM prediction
Br ~ 4x10-6.
 It is highly sensitive to new physics, and theoretically very clean.
 But, experimentally very challenging.
Signature: BK(*) + nothing.
DAMA NaI
3s
 Nothing may be light dark matter
Region
(see papers by Pespelov et al.).
Direct dark matter search cannot
see M<10GeV region.
21
BK(*)nn
 Babar @82fb-1
hadronic and semileptonic tagging
Br(B  K+νν) < 5.2×10-5 (90%C.L.)
Br(B0  K*0νν) < 3.4 ×10-5 (90%C.L.)
 Belle @253fb-1
hadronic tagging
Br(B  K+νν) < 3.6×10-5 (90%C.L.)
 Belle @492fb-1
hadronic tagging
Yield = 4.7
Br(B  K*0νν) < 3.4 ×10-4 (90%C.L.)
+3.1
-2.6
(1.7σ stat. significance)
BK+nn extrapolated sensitivity (if SM)
3s @ 12ab-1, 5s @ 33ab-1
Need Super-B !!
22
SuperKEKB
 Asymmetric-energy ee collider to be realized by upgrading the
existing KEKB collider.
 Super-high luminosity  81035 cm2s1  1010 BB per yr.
 8109 t t  per yr.
 Letter of Intent is available at: http://belle.kek.jp/superb/loi
Belle with improved rate immunity
ECM=M((4s))
Higher beam current,
smaller by* and
crab crossing
 L = 81035
23
Flavor Physics at SuperKEKB
1.
Are there new CP-violating phases ?
2.
Are there new right-handed currents ?
3.
Are there new flavor-changing interactions with b, c or t ?
SuperKEKB will answer
these questions by
scrutinizing loop diagrams.
DSfK0 (July 2005)
B
b
_
d
DSfK0 (SuperKEKB)
s_
s
s_
d
f
Ks
SM predictions
24
LFV Search at Super-B
cf) Hayasaka at BNM2006
PDG2006
Belle
Babar
g
tlg
0
t
t
m (e )
m ( e)
(ml2 )23(13)
t3l, lh
t
m
h
based on eff.
and NBG of
most sensitive
analysis
Estimated
upper limit
range of Br
m ( s)
m (s )
Search region enters into O(10-810-9)
25
Major Achievements Expected at SuperKEKB
Case 1: All Consistent with Kobayashi-Maskawa Theory
Search for New CP-Violating Phase in b g s with 1 degree precision
CKM Angle Measurements with 1 degree precision
Discovery of B g Knn
Discovery of New Subatomic Particles
sin2qW with O(10-4) precision
|Vub| with 5% Precision
Discovery of B g Dtn
“Discovery” with
significance > 5s
Observations with
U(5S), U(3S) etc.
Discovery of B g mn
Discovery of CP Violation in Charged B Decays
Discovery of Direct CP Violation in B0 g Kp Decays (2005)
Discovery of CP Violation in Neutral B Meson System (2001)
26
Major Achievements Expected at SuperKEKB
Case 2: New Physics with Extended Flavor Structure
Search for New CP-Violating Phase in b g s with 1 degree precision
Discovery of Lepton Flavor
Violation in t g mg Decays#
CKM Angle Measurements with 1 degree precision
of B g Knn
Discovery of NewDiscovery
Right-Handed
Current in b g s Transitions #
Discovery of New Subatomic Particles
-4
Discoverysin
of2qNew
CP Violation
W with O(10 ) precision
0 Decays#
in B0 |Vub|
g fK
with 5% Precision
Discovery of B g Dtn
“Discovery” with
significance > 5s
# SUSY GUT with
gluino mass = 600GeV,
tanb = 30
Observations with
U(5S), U(3S) etc.
Discovery of B g mn
Discovery of CP Violation in Charged B Decays
Discovery of Direct CP Violation in B0 g Kp Decays (2005)
Discovery of CP Violation in Neutral B Meson System (2001)
27
Super-KEKB Status
 Super-high luminosity  81035 cm-2s-1
– Natural extension of KEKB
– With technology proven at KEKB
Crab crossing
 Many key components are tested at KEKB.
Crab crossing will be tested in winter 2007.
Ante-chamber
Installed at KEKB
Crab cavity
Super-KEKB is a machine which can be build now.
28
Super-KEKB Status
 Letter of Intent (LoI) in 2004
– 276 authors from 61 institutions
– available at
http://belle.kek.jp/superb/loi
– “Physics at Super B Factory”
hep-ex/0406071
 Updates of physics reach and also
new measurements (U(5S) run etc.)
are extensively discussed.
– BNM2006 workshop (Sep.13-14)
http://www-conf.kek.jp/bnm/2006/
– 2nd meeting at Nara (Dec.18-19,
after CKM2006@Nagoya)
A lot of activities for physics and detector studies !
You are welcome to join !
29
Summary
 The first evidence of Btn has obtained by Belle @414fb-1.
 Successful operation of B factories have finally brought the B
leptonic decays on the stage.
 O(ab-1) data will bring Bmn and Bdmm for serious examination.
 These enable us to explore New Physics, esp. in large tanb region,
together with other measurements; DmBS, Bsmm, BXsg and also t
decays (tmh, tmg).
(see talk by A.Weiler)
 O(10ab-1) data will bring BKnn at horizon.
We need a Super B Factory !
 Super-KEKB aims at L=8x1035cm-2s-1, with tech. proven at KEKB.
 A lot of activities for physics and detector studies.
 HEP community in Japan is now discussing “Grand Lepton Collider”
plan to accommodate both Super-KEKB and ILC.
Stay tuned !
30
References
 Bln
– Btn:
Belle (hep-ex/0604018), BaBar (hep-ex/0608019)
– Bmn, en: Belle (hep-ex/0408132), BaBar (hep-ex/0607110)
– Blng:
Belle (hep-ex/0408132)
 Bll
– Be+e-, m+m-, e+m– Be+e-g, m+m-g :
– Bt+t-:
Belle (PRD68, 111101(R) (2003))
BaBar (PRL94, 221803(2005)), CDF
BaBar(hep-ex/0607058)
BaBar(PRL96, 241802 (2006))
 BKnn, nn
– B+K+nn Belle(hep-ex/0507034), BaBar(PRL94, 101801 (2005))
– B0K*0nn Belle(hep-ex/0608047)
– B0nn
BaBar(PRL93, 091802(2004))
Due to limited time, some of them cannot be mentioned
or have to be put in backup
31
Backup
32
New Physics in large tanb
 Leptonic decays (Bln, ll) are theoretically clean, free from
hadronic uncertainty.
 In particular, they are good probes in large tanb region, together
with other measurements; DmBS, Bsmm, BXsg and also t decays
(tmh, tmg).
Ex.) G.Isidori & P.Paradisi, hep-ph/0605012
u
H
n
t
Neutral Higgs
b
d
tanb
Charged Higgs
b
A0,H0, h0
See talk by A.Weiler


MH(GeV)
33
Btn Candidate Event
B+ g D0 p+
K+ p- p+ pB- g t - n
e-nn
34
Cont’d
Charged Higgs Mass Reach
Mass Reach (GeV)
(95.5%CL exclusion @ tanb=30)
Only exp. error
(DVub=0%, DfB=0%)
DVub=2.5%, DfB=2.5%
DVub=5%, DfB=5%
Luminsoity(ab-1)
Note) Ratio to cancel out fB may help
V
Br(B  tn )
 ub
Δmd
Vtd
Vub
Vtd
(G.Isidori&P.Paradisi, hep-ph/0605012)
from other measurements
35
B0t+ t- (BaBar @ 210fb-1)
 Experimentally very very challenging (2-4 neutrinos
in the final state ! )
 High sensitive to NP
Bsmm at hadron machines
 Analysis
• Reconstruct one B in a fully
hadronic final state B D(*) X
=>280k events
• In the event remainder, look for
two t decays (tlnn, pn, rn)
• Kinematics of charged partilce
momenta and residual energy
are fed into a neutral network
to separate signal and BG
Data
Nobs=263±19
Control
sample
Nexpect=281±48
Br(B  tt ) < 4.1 ×10-3 @90%C.L.
Phys. Rev. Lett. 96, 241802 (2006)
36
B0
 n n invisible) @Babar
Semileptonic tags :
B0D(*)-l+n (D*- D0 p-)
Require nothing in recoil:
- no charged tracks,
– 8
B pairs used:
(88.5±1.0)×106
nn
- limited # of neutral clusters.
ML fit to Eextra
nng
Ns =17 ± 9
Nb =19-8+10
Upper limit (frequentist)
incl. systematics (additive;7.4events,
multiplicative; 10.9%)
B(B0
 invisible) < 22 ×
10-5
(90%CL)
Phys. Rev. Lett. 93, 091802 (2004)
37
Future Prospect: BKnn
 Belle @ 250fb-1 (preliminary)
cf.) K.Ikado @ BNM2006
Fully reconstructed tag (by modifying the PID criteria used in
Btn analysis).
Belle preliminary
Consistent with BG expected
Signif.
Lum (ab-1)
3s
12
5s
33
Need Super-B !
38
Advantages of
SuperKEKB
Clean environment  measurements that no other experiment can perform.
Examples: CPV in B g fK0, B g h’K0 for new phases, B g Ksp0g for righthanded currents.
“B-meson beam” technique  access to new decay modes.
Example: discover B g Knn.
Measure new types of asymmetries.
Example: forward-backward asymmetry
in b g smm, see
Rich, broad physics program including B,
t and charm physics.
Examples: searches for t g mg and D-D
mixing with unprecedented sensitivity.
No other experiment can
compete for New Physics reach
in the quark sector.
39
Role of SuperKEKB
What is the origin of CP violation ?
What is the origin of the matter-dominated Universe ?
What is the flavor structure of new physics (e.g. SUSY breaking) ?
LHC
EDM
ILC
LFV
Super B
K physics
Muon g-2
Neutrino
These grand questions can only be answered by
experiments both at the luminosity and energy frontiers.
SuperKEKB will play an essential role.
40
41