Toru%20Iijima

1
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
2
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 .
3
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).
• B decay has many patterns to test the effects.

Rare Decays !!
Annihilation
Box
Penguin
4
Hunting Rare Decays
In 1993
CLEO First evidence of B?Kg
PRL 71, 674 (1993)
5
Hunting Rare Decays

• High luminosity
• Good detector (PID, vertex)
• Analysis techniques
• qq background suppression
• Fully reconstructed tag

Observation of b?dg
FB asymmetry in B?K ll-
Direct CPV in B0?Kp-
Beginning of B-gtfK0 saga
Observation of B?K l l-
CPV in B decay
Success of B factories brought rare B decays in
leptonic and neutrino modes on the stage !
6
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 fBVub

• In two Higgs doublets model, charged Higgs
  exchange interferes with the helicity suppressed
  W-exchange.

• If mn is also measured, lepton universality can
  be tested.
• ? SUSY correction etc.

7
Full Reconstruction Method

• Fully reconstruct one of the Bs to tag
• B production
• B flavor/charge
• B momentum

Decays of interests B?Xu l n, B?K n n
B?Dtn, tn
B
e- (8GeV)
e(3.5GeV)
?(4S)
p
full (0.10.3) reconstruction B?Dp etc.
B
Single B meson beam in offline !
Powerful tools for B decays w/ neutrinos
8
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.
9

The First B?tn Evidence

• The final results are deduced by unbinned
  likelihood fit to the obtained EECL
  distributions.

Signal background
S Statistical Significance
Observe 17.2 events in the signal region.
Significance decreased to 3.5 s after including
systematics
5.3 - 4.7
Background
B?tn Signal
Signal shape Gauss exponential Background
shape second-order polynomial
Gauss (peaking component)
10
Results (Br fB Extraction)

• Measured branching fraction
• Product of B meson decay constant fB and CKM
  matrix element Vub
• Using Vub (4.39 ? 0.33)10-3 from HFAG

16 14(exp.) 8(Vub)
15
fB 216 ? 22 MeV HPQCD, Phys. Rev. Lett. 95,
212001 (2005)
11
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
New value
0.51
FPCP04 result
The revised paper has been resubmitted, and
posted as hep-ex/0604018v2.
12
B?tn Search _at_ 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 (Xg, p from D0
  is not explicitly reconstructed)
• Require lepton CM momentum gt 0.8 GeV
• Require that -2 lt cosqB-D0l lt 1
• Parent B energy and momentum are determined from
  the beam energy
• Tagged B reconstruction efficiency 0.7
• Discriminate signal from
• background using Eextra

• t lepton is identified in the
• 4 decay modes

13
B?tn Search _at_ Babar (cont.)

• Observed excess is not significant yet (1.3s),
  and set a limit on the branching fraction and
  quote a central value.
• Deduced fB Vub

Babar preliminary
14
Constraints on Charged Higgs
These regions are excluded.
fB from HPQCD Vub from HFAG
Much stronger constraint than those from energy
frontier exps.
15
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 lt 5 in future is an realistic
  goal.
• fB from theory 10 now ? 5 ?

My assumption
DfB(LQCD) 5
Lum. DB(B?tn) exp DVub
414 fb-1 36 7.5
5 ab-1 10 5.8
50 ab-1 3 4.4
Preliminary
16
B?mn, en

• BaBar _at_ 208.7fb-1
• w/ fully reconstructed tag
• B?D() X.

• Belle _at_ 140fb-1
• w/ inclusive reconstruction of the companion
  B.

_at_90C.L.
_at_90C.L.
17
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.
• fBVub determination.
• Test the lepton universality.

Preliminary

• Method?
• Inclusive-recon method has high efficiency but
  poor S/N.
• Hadronic tag will provide very clean and
  ambiguous signals, but very low efficiency.

See also talk by Robertson at CERN flavour WS
(May 2006)
18
B0?ll-

• Proceeds via box or penguin annihilation
• SM Branching fractions
• Flavor violating channel (B0 ? e m , etc.) are
  forbidden in SM.

19
B0?ll- (ee-,mm-,em-)
Signal regions
Events observed
mm
ee
B(B0 ? ee) lt 6.1 10-8 (90CL) B(B0 ?
mm) lt 8.3 10-8 (90CL) B(B0 ? e m) lt
18 10-8 (90CL)
111 fb-1
Phys. Rev. Lett. 94, 221803 (2005)
e-m
B(B0 ? ee) lt 1.9 10-7 (90CL) B(B0 ?
mm) lt 1.6 10-7 (90CL) B(B0 ? e m) lt
1.7 10-7 (90CL)
78 fb-1
Phys. Rev. D 68, 111101 (2003)
B(B0d?mm-) lt 2.310-8 (90 CL)
780 pb-1
It would be interesting to see results with more
data. What about U(5S) data at Super-B ?
20
B0?llg (BaBar_at_ 292fb-1)

• 320 M BB events
• 0.3 lt mll lt 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 ? ee-g) lt 0.7 10-7 (90CL) B(B0 ? mm-g)
lt 3.4 10-7 (90CL)
Babar preliminary
21
B?K() n n (b?s w/ two ns)

• B?K()nn proceeds via one-loop radiative penguin
  and box diagrams.
• It is highly sensitive to new physics, and
  theoretically very clean.
• But, experimentally very challenging.
• Signature B?K() nothing.
• Nothing may be light dark matter
• (see papers by Pespelov et al.).

SM prediction Br 4x10-6.
Direct dark matter search cannot see Mlt10GeV
region.
22
B?K()nn

• Babar _at_82fb-1
• hadronic and semileptonic tagging

• Belle _at_253fb-1
• hadronic tagging

• Belle _at_492fb-1
• hadronic tagging

3.1 -2.6
Yield 4.7
(1.7s stat. significance)
23
SuperKEKB
? Asymmetric-energy ee- 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/super
b/loi
Belle with improved rate immunity
ECMM(?(4s))
Higher beam current, smaller by and crab
crossing ? L 8?1035
24
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.
25
LFV Search at Super-B
cf) Hayasaka at BNM2006
t?lg
PDG2006 Belle Babar
Preliminary
based on eff. and NBG of most sensitive
analysis
t?3l, lh
Estimated upper limit range of Br
t?3l
t?lg
t?lp/h()
t?B g/p
t?l Ks
Search region enters into O(10-8?10-9)
26
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
Observations with U(5S), U(3S) etc.
Vub with 5 Precision
Discovery of B g Dtn
Discovery of B g mn
Discovery of CP Violation in Charged B Decays
Discovery with significance gt 5s
Discovery of Direct CP Violation in B0 g Kp
Decays (2005)
Discovery of CP Violation in Neutral B Meson
System (2001)
27
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
Discovery of New Right-Handed Current in b g s
Transitions
Discovery of B g Knn
Discovery of New Subatomic Particles
Discovery of New CP Violation in B0 g fK0 Decays
sin2qW with O(10-4) precision
Observations with U(5S), U(3S) etc.
Vub with 5 Precision
Discovery of B g Dtn
Discovery of B g mn
Discovery of CP Violation in Charged B Decays
Discovery with significance gt 5s
Discovery of Direct CP Violation in B0 g Kp
Decays (2005)
SUSY GUT with gluino mass 600GeV, tanb 30
Discovery of CP Violation in Neutral B Meson
System (2001)
28
Super-KEKB Status
Crab crossing

• Super-high luminosity ? 8?1035 cm-2s-1
• Natural extension of KEKB
• With technology proven at KEKB
• 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.
29
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_at_Nagoya)

A lot of activities for physics and detector
studies ! You are welcome to join !
30
Summary

• The first evidence of B?tn has obtained by Belle
  _at_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).
• O(10ab-1) data will bring B?Knn at horizon.

(see talk by A.Weiler)
31
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?ee-, mm-, em- Belle (PRD68, 111101(R)
  (2003))
• BaBar (PRL94, 221803(2005)), CDF
• B?ee-g, mm-g BaBar(hep-ex/0607058)
• B?tt- BaBar(PRL96, 241802 (2006))
• B?Knn, nn
• B?Knn Belle(hep-ex/0507034), BaBar(PRL94,
  101801 (2005))
• B0?K0nn 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
32
Backup
33
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
Charged Higgs
Neutral Higgs
See talk by A.Weiler
34
B?tn Candidate Event
B g D0 p K p- p p- B- g t -
n e-nn
35
Contd
Charged Higgs Mass Reach (95.5CL exclusion _at_
tanb30)
Only exp. error (DVub0, DfB0)
Preliminary
DVub2.5, DfB2.5
Mass Reach (GeV)
DVub5, DfB5
Luminsoity(ab-1)
Note) Ratio to cancel out fB may help
(G.IsidoriP.Paradisi, hep-ph/0605012)
from other measurements
36
B0?t t- (BaBar _at_ 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
• gt280k 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
Control sample
Nobs26319
Nexpect28148
_at_90C.L.
Phys. Rev. Lett. 96, 241802 (2006)
37
B0 ? n n (invisible) _at_Babar
B pairs used (88.51.0)106

• Semileptonic tags
• B0?D()-ln (D- ?D0 p-)
• Require nothing in recoil
• - no charged tracks,
• - limited of neutral clusters.
• ML fit to Eextra
• Upper limit (frequentist)
• incl. systematics (additive7.4events,
• multiplicative 10.9)

nn
8
nng
Phys. Rev. Lett. 93, 091802 (2004)
B(B0 ? invisible) lt 22 10-5 (90CL)
38
Future Prospect B?Knn
cf.) K.Ikado _at_ BNM2006

• Belle _at_ 250fb-1 (preliminary)
• 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 !
39
Advantages of SuperKEKB

• Clean environment ? measurements that no other
  experiment can perform. Examples CPV in B g fK0,
  B g hK0 for new phases, B g Ksp0g for
  right-handed 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.

40
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) ?

These grand questions can only be answered by
experiments both at the luminosity and energy
frontiers. SuperKEKB will play an essential role.
41
(No Transcript)