Leptoquarks

1
Lepton number violation at the LHC
Leptoquarks
Diquarks
with
and
Hiroaki SUGIYAMA
(Maskawa Inst., Kyoto Sangyo Univ.)
Contents

• Introduction, Motivation

• The Model - colored Zee-Babu model -

• Lepton Number Violation at the LHC

• Summary

based on M. Kohda, HS, K. Tsumura, PLB718, 1436
(2013)
2
Introduction -Neutrino Oscillation-
Neutrino masses, mixings, and oscillations
Massive neutrinos can be mixed
flavor eigenstates (weak interaction)
mass eigenstates (propagation)
Maki-Nakagawa-Sakata matrix (mixing)
(quark sector Cabibbo-Kobayashi-Maskawa matrix)
Flavor transitions (oscillations) are possible
masses
distance
energy
3
Two Neutrino Case (good approximation)
P(transition)
accuracy for accuracy for
first oscillation maximum
good set up (E, L) of experiments to obtain
and
4
e.g., Measurement in KamLAND experiment
55 Japanese nuclear power reactors
Kamioka mine
apparently oscillating !
S. Abe et al., PRL100, 221803
Neutrino masses are necessary
We have evidence of oscillations
5
Current knowledge on neutrino masses and mixings
T2K
reactor
atmospheric
accelerator
solar
KamLAND
or
inverted
normal
6
Introduction -Neutrino Mass-
Neutrino masses are extremely smaller than other
fermion masses.
neutrino-specific mechanism to generate their
masses ?
for
c.f.
Unnatural
Neutrino-specific mass term
Majorana
Allowed only for neutrinos
Lepton number violation
7
Majorana mass LV processes
LV process
Majorana neutrino
(tiny mass)
(tiny rate)
e.g., Neutrinoless double beta decay
8
Motivation
Input Small
Output Small rate of LV
Input Unsuppressed LV
Output Suppressed
Black box TeV-scale particles
No
9
Two-Loop Neutrino Mass
Zee-Babu Model
A. Zee, NPB264, 99 (1986)
K.S. Babu, PLB203, 132 (1988)
colored version
two colored loops
10
Lepton number violation at the LHC
Leptoquarks
Diquarks
with
and
Hiroaki SUGIYAMA
(Maskawa Inst., Kyoto Sangyo Univ.)
Contents

• Introduction, Motivation

• The Model - colored Zee-Babu model -

• Lepton Number Violation at the LHC

• Summary

based on M. Kohda, HS, K. Tsumura, PLB718, 1436
(2013)
11
The Model - Zee-Babu Model -
colored
Briefly mentioned in K.S. Babu and C.N. Leung,
NPB619, 667 (2001)
Scalar Leptoquark
Scalar Diquark
soft LV term (no BV)
Two-loop neutrino mass
color
color
12
A Benchmark Point
LQ Yukawa
DQ Yukawa
Scale
satisfy constraints (couplings, masses)
agree with neutrino oscillation data
13
Lepton number violation at the LHC
Leptoquarks
Diquarks
with
and
Hiroaki SUGIYAMA
(Maskawa Inst., Kyoto Sangyo Univ.)
Contents

• Introduction, Motivation

• The Model - colored Zee-Babu model -

• Lepton Number Violation at the LHC

• Summary

based on M. Kohda, HS, K. Tsumura, PLB718, 1436
(2013)
14
Large Hadron Collider
Higgs at CMS
Higgs at ATLAS
4 Apr. 2008
4 Apr. 2008
4 Jul. 2012
4 Jul. 2012
(cf. Tevatron at )
collider at
(cf. 26.4km loop subway in Nagoya, Japan)
26.7km ring
(cf. 21.7km loop line in Osaka, Japan)
15
8.5 km
16
LV Process at the LHC
without missing
No missing energy
No missing L
Definite total L of final states
Evidence for LV
17
without missing
LV
No SM process in principle
No mimic event in SM
Hard
Clear evidence for LV
18
(No Transcript)
19
at
for
20
For fixed
Large
Good for
Bad for

Bad for
Good for

Small
is preferred
Benchmark point
21
_at_ Benchmark point
w/o missing
w/ missing
w/o missing
( )
22
Benchmark point LHC with
23
Summary
Zee-Babu Model with Leptoquark and Diquark
Colored
Suppressed neutrino mass ( two-loop,
, )
color
color
Unsuppressed LV process at the LHC
without missing
24
Backup
25
LV Process at the LHC
without missing
at
even for
for
for
26
Production Cross Section
T. Han, I. Lewis, and Z. Liu, JHEP 1012, 085
(2010)
27
Bounds on Masses
Leptoquark mass
(for
)
CMS
PRD86, 052013 (2012)
PLB709, 158 (2012)
ATLAS
EPJC72, 2151 (2012)
Diquark mass
No analysis for
cf.
CMS
arXiv1302.4794
28
Bounds on Masses
Leptoquark mass
CMS
PRD86, 052013 (2012)
JHEP1212, 055 (2012)
arXiv1210.5629
29
Bounds on Masses
Leptoquark mass
PLB709, 158 (2012)
ATLAS
EPJC72, 2151 (2012)
30
Bounds on Masses
Diquark mass
No analysis for
cf.
CMS
arXiv1302.4794
31
Constraints on New Yukawa Couplings
LQ Yukawa
M. Carpenter and S. Davidson, EPJC70, 1071 (2010)
( conversion )
Constraint
Benchmark
( meson decay )
Constraint
Benchmark
Constraint
MEG, PRL107, 171801 (2011)
MEG, arXiv1303.0754
Benchmark
32
DQ Yukawa
UTfit, JHEP0803, 049 (2008)
mixing
Benchmark point
mixing
mixing
33
LFV
We ignore .
No
Type-II or Type-X THDMs ( or are -
odd)
or - triplet Leptoquark
Dangerous
34
Neutrinoless Double Beta Decay
_at_ Benchmark point