K 2020 YITP (virtual), Sept 2, 2020 - - PowerPoint PPT Presentation

K中間子による新物理探査

Kohsaku Tobioka (飛岡幸作)

Florida State University

素粒子物理学の進展2020

YITP (virtual), Sept 2, 2020

Collaboration with

Teppei Kitahara, Takemichi Okui, Gilad Perez, Yotam Soreq 
 [Phys.Rev.Lett. 124 (2020) 07180, 1909.11111 +updates ]
 Stefania Gori, Gilad Perez [2005.05170]
 Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo 
 [Phys.Rev.Lett. 124 (2020) 041802, 1902.07715]

Kohsaku Tobioka (FSU)

Outline

2

• Introduction
• Why Kaon? Excellent probe for New Physics, FIMP
• Rare kaon decay K→πvv at KOTO, and NA62
• Recent results from KAON2019 to ICHEP2020
• NA62 results, KOTO “excess”
• New Physics Scenarios
• Future prospects
• Higgs Portal, Muonic Force, Axion-like-particle

Kohsaku Tobioka (FSU)

3

History: Kaons as discovery probes of new physics

Glashow-Iliopoulos-Maiani (GIM) mechanism

2x2 matrix →charm as new d.o.f.

• scillation
• CP violation

CKM matrix [3x3 matrix with new phase] KL(~CP odd) KL→π0π0π0 KS(~CP even) Ks→π0π0

• Charm quark

Puzzle: KL→μ+μ- rate too small

from CERN Courier

K0(¯ sd) − ¯ K0(s ¯ d)

Also observed KL→π0π0 !!

日経サイエンス

Kohsaku Tobioka (FSU)

Very Rare Kaon Decays

4

~

M

∝ |M|2

∝ (ImM)2

K+ → π+ν¯ ν

KL → π0ν¯ ν

Kohsaku Tobioka (FSU)

Very Rare Kaon Decays

4

Extremely rare and precise process in SM.

[Buras et al., 1503.02693]

• Br~10-11 due to suppressions of 1loop, CKM and GIM
• Unlike LHC physics, a few events are already significant!

~

M

∝ |M|2

∝ (ImM)2

K+ → π+ν¯ ν

KL → π0ν¯ ν

BR(K+ → π+ν¯ ν) = (9.11 ± 0.72) × 10−11

BR(KL → π0ν¯ ν) = (3.00 ± 0.30) × 10−11

Kohsaku Tobioka (FSU)

Grossman-Nir bound

5

[Y. Grossman and Y. Nir (‘97)]

~

M

• Br[KL] indirectly bounded by Br[K+]

BR[KL → π0ν¯ ν] BR[K+ → π+ν¯ ν] ≤ 4.3

Γ[KL → π0ν¯ ν] Γ[K+ → π+ν¯ ν] = (Im M)2 |M|2 ≤ 1

Ratio of total widths +isospin breaking

Isospin relation(∆I=1/2)

Kohsaku Tobioka (FSU)

Grossman-Nir bound

5

[Y. Grossman and Y. Nir (‘97)]

~

M

• Br[KL] indirectly bounded by Br[K+]

BR(KL → π0X) . 4.3BR(K+ → π+X)

[H. Leutwyler, M. A. Shifman(’90)]

saturates,e.g., when X is CP-even

• GN bound can be generalized to new physics case

BR[KL → π0ν¯ ν] BR[K+ → π+ν¯ ν] ≤ 4.3

Γ[KL → π0ν¯ ν] Γ[K+ → π+ν¯ ν] = (Im M)2 |M|2 ≤ 1

Ratio of total widths +isospin breaking

Isospin relation(∆I=1/2)

Kohsaku Tobioka (FSU)

Experiments for Rare Koan Decays

6

30GeV p since 2013 (restart ‘15)

~2GeV KL

Gold

JPARC

1 2 [m] 2 4 6 8 10 12

CsI calorimeter

Concr iron shield FB NCC Hinemos MB BCV CV OEV LCV CC03 CC04 CC05 CC06 BHCV BHPV

KL beam

Decay volume (vacuum)

400GeV p from SPS physic run since 2015

75GeV K+ CERN Aim for precision Br~10-11 ⇒ NK~1013 ≫ NB-pair,BelleII~1011!! ~3m ~150m Mainly ECAL

Kohsaku Tobioka (FSU)

Kaon Measurements—Big Picture —

7

KL → ππ K0 → μ+μ− K → πν¯

ν

B physics RBC-UKQCD FCNC and/or CPV

εK and ε′

• KS → π0μ+μ−

KS → μ+μ−γ KS → 4ℓ KS → π+π−e+e−

Understanding

• f ChPT

KL → π0ℓ+ℓ−

Reduce th error

K → πX

• vs unitarity

Vus

CORRELATION

summary 北原さん

https://indico.cern.ch/event/783304/contributions/3497938/attachments/1916882/3169405/TeppeiKitahara_HC2NP .pdf

[富井さんtalk]

Kohsaku Tobioka (FSU)

From Precision to Discovery

8

Effective Field Theory [conventional] weak Mass of new particle

Probed

Coupling 0.1 10-5

Kohsaku Tobioka (FSU)

From Precision to Discovery

8

Effective Field Theory [conventional] weak Mass of new particle

Probed

Coupling 0.1 10-5

Weak Scale BSM, e.g. SUSY

• Conventional

studies

Kohsaku Tobioka (FSU)

From Precision to Discovery

8

Effective Field Theory [conventional] weak

Feebly Interacting Light Particle

Mass of new particle

Probed

Coupling 0.1 10-5

Weak Scale BSM, e.g. SUSY

• Conventional

studies

• Target

at Intensity Frontier[US], Physics Beyond Collider[Europe]

• Dark matter, portal, various anomalies

Kohsaku Tobioka (FSU)

From Precision to Discovery

8

Effective Field Theory [conventional] weak

Feebly Interacting Light Particle

Mass of new particle

Probed

Coupling Include light d.o.f. [direct search] 0.1 10-5

Weak Scale BSM, e.g. SUSY

• Conventional

studies

• Target

at Intensity Frontier[US], Physics Beyond Collider[Europe]

• Dark matter, portal, various anomalies

Kohsaku Tobioka (FSU)

From Precision to Discovery

9

Weak Scale BSM, e.g. SUSY

Effective Field Theory [conventional] weak

Feebly Interacting Light Particle

Mass of new particle

Probed

Coupling

• Target

at Intensity Frontier[US], Physics Beyond Collider[Europe]

Include light d.o.f. [direct search] 0.1 10-5

Cosmology Astrophysics (<GeV)

• Conventional

studies

• Dark matter, portal, various anomalies

Cosmology Astrophysics (<me)

Same for Belle II, LHCb, ν-factrory

Kohsaku Tobioka (FSU)

Outline

10

✓ Introduction

• Why Kaon? Excellent probe for FIMP
• Rare kaon decay K→πvv at KOTO, and NA62
• Recent results from KAON2019 to ICHEP2020
• NA62 results, KOTO “excess”
• New Physics Scenarios
• Future prospects
• Higgs Portal, Muonic Force, Axion-like-particle

Kohsaku Tobioka (FSU)

NA62

11

400GeV p from SPS physic run since 2015

75GeV K+ CERN ~150m tracker

K+ π+ v v

* * *

• Main signal: π++missing

BG: K+→π+π0, π+π+π-

Kohsaku Tobioka (FSU)

NA62

11

400GeV p from SPS physic run since 2015

75GeV K+ CERN ~150m tracker

BR(K+ → π+ν¯ ν) = (9.11 ± 0.72) × 10−11

[SM]

K+ π+ v v

* * *

• Main signal: π++missing

BG: K+→π+π0, π+π+π-

Kohsaku Tobioka (FSU)

NA62

11

400GeV p from SPS physic run since 2015

75GeV K+ CERN ~150m tracker

BR(K+ → π+ν¯ ν) = (9.11 ± 0.72) × 10−11

[SM]

• Currently NK+~7x1012 decays

K+ π+ v v

* * *

• Main signal: π++missing

BG: K+→π+π0, π+π+π-

Kohsaku Tobioka (FSU)

NA62

11

400GeV p from SPS physic run since 2015

75GeV K+ CERN ~150m tracker

BR(K+ → π+ν¯ ν) = (9.11 ± 0.72) × 10−11

[SM]

• Currently NK+~7x1012 decays

K+ π+ v v

* * *

• Trying to measure BR(K+→π+vv) with O(10%) precision
• Main signal: π++missing

BG: K+→π+π0, π+π+π-

Kohsaku Tobioka (FSU) NA62 Preliminary

Box Opened

2 events observed in signal region

NA62

12

KAON2019 ICHEP2020 Obs: 3 [‘16+’17, NK+~2x1012] BG: 1.65 (±0.31)

signal region

K+→π+π0

𝐋+ → 𝛒+𝛏ത 𝛏

𝐿+ decay in flight technique NA62 𝐿+ 87/E949

Data 2016 NA62 𝐶𝑆 𝐿+ → 𝜌+𝜉 ҧ 𝜉 = 1.73−1.05

+1.15 × 10−10

Kohsaku Tobioka (FSU) NA62 Preliminary

Box Opened

2 events observed in signal region

NA62

12

KAON2019 ICHEP2020 Obs: 3 [‘16+’17, NK+~2x1012] BG: 1.65 (±0.31)

17 New result on the search for the K+ → π+νν decay at NA62 (R. Marchevski) ICHEP 2020

Opening the box in the 2018 data

5.3 background + 7.6 SM signal events expected, 17 events observed

NA62 Preliminary

Obs: 17 [’18, NK+~7x1012] BG: 5.3 (+1,-0.7)

signal region

K+→π+π0

𝐋+ → 𝛒+𝛏ത 𝛏

𝐿+ decay in flight technique NA62 𝐿+ 87/E949

Data 2016 NA62 𝐶𝑆 𝐿+ → 𝜌+𝜉 ҧ 𝜉 = 1.73−1.05

+1.15 × 10−10

Kohsaku Tobioka (FSU)

NA62

13

KAON2019 ICHEP2020

NA62 result from the complete Run 1(2016 + 2017 + 2018)

Observed events: 1 (2016) + 2 (2017) + 17(2018) = 20 (Run 1) Expected background ~ 0.2(2016) + 1.5(2017) + 5.3(2018) = 7 (Run 1)

• e most precise measurement of the BR obtained so far
• e result is compatible with the SM prediction within one standard deviation
• Perform extremely well, and confirm the signal at 3.5σ!

• Compatible with SM. More data in 2021 with LHC Run III.

ICHEP2020

• R. Marchevski

Obs: 3 [‘16+’17, NK+~2x1012] BG: 1.65 (±0.31) Obs: 17 [’18, NK+~7x1012] BG: 5.3 (+1,-0.7)

Kohsaku Tobioka (FSU)

KOTO

14

30GeV p since 2013 (restart ‘15)

~2GeV KL

Gold

JPARC

1 2 [m] 2 4 6 8 10 12

CsI calorimeter

Concr iron shield FB NCC Hinemos MB BCV CV OEV LCV CC03 CC04 CC05 CC06 BHCV BHPV

KL beam

Decay volume (vacuum)

~3m Mainly ECAL

π0→ ν

*

γγ KL v

• Main signal: 2γ+missing

BG: KL→3π0, neutron

Kohsaku Tobioka (FSU)

KOTO

14

30GeV p since 2013 (restart ‘15)

~2GeV KL

Gold

JPARC

1 2 [m] 2 4 6 8 10 12

CsI calorimeter

Concr iron shield FB NCC Hinemos MB BCV CV OEV LCV CC03 CC04 CC05 CC06 BHCV BHPV

KL beam

Decay volume (vacuum)

~3m Mainly ECAL

π0→ ν

*

γγ KL v

[SM]

BR(KL → π0ν¯ ν) = (3.00 ± 0.30) × 10−11

• Main signal: 2γ+missing

BG: KL→3π0, neutron

Kohsaku Tobioka (FSU)

KOTO

14

30GeV p since 2013 (restart ‘15)

~2GeV KL

Gold

JPARC

1 2 [m] 2 4 6 8 10 12

CsI calorimeter

Concr iron shield FB NCC Hinemos MB BCV CV OEV LCV CC03 CC04 CC05 CC06 BHCV BHPV

KL beam

Decay volume (vacuum)

~3m Mainly ECAL

π0→ ν

*

γγ KL v

• Currently NKL~6x1011 decays [7x1012 incoming]

[SM]

BR(KL → π0ν¯ ν) = (3.00 ± 0.30) × 10−11

• Main signal: 2γ+missing

BG: KL→3π0, neutron

Kohsaku Tobioka (FSU)

KOTO

14

• Trying to measure a few KL→π0vv events

30GeV p since 2013 (restart ‘15)

~2GeV KL

Gold

JPARC

1 2 [m] 2 4 6 8 10 12

CsI calorimeter

Concr iron shield FB NCC Hinemos MB BCV CV OEV LCV CC03 CC04 CC05 CC06 BHCV BHPV

KL beam

Decay volume (vacuum)

~3m Mainly ECAL

π0→ ν

*

γγ KL v

• Currently NKL~6x1011 decays [7x1012 incoming]

[SM]

BR(KL → π0ν¯ ν) = (3.00 ± 0.30) × 10−11

• Main signal: 2γ+missing

BG: KL→3π0, neutron

Kohsaku Tobioka (FSU)

KOTO “excess”?

15

KAON2019 [talk by Shinohara] Blind analysis Z[reconstructed decay position]

Reconstructed π0 pT

signal region

BG:0.05±0.02, SM[KL→π0vv]0.05±0.01

1 2 3 4 5 6 7

Pi0RecZ 2000 3000 4000 5000 6000 Pi0Pt 50 100 150 200 250 300 350 400 450 500

462 473.1 ± 4.2 0.08 ± 0.06 0.00 ± 0.00 0.18 ± 0.09 0.00 ± 0.00 0.07 ± 0.05 0.05 ± 0.02

• S.E.S : 6.910
• bserved

expectation

P r e l i m i n a r y

0.33 ± 0.11 (including signal region)

Open the box [unblinding]

Kohsaku Tobioka (FSU)

KOTO “excess”?

15

KAON2019 [talk by Shinohara] Blind analysis Z[reconstructed decay position]

Reconstructed π0 pT

signal region

BG:0.05±0.02, SM[KL→π0vv]0.05±0.01

1 2 3 4 5 6 7

Pi0RecZ 2000 3000 4000 5000 6000 Pi0Pt 50 100 150 200 250 300 350 400 450 500

462 473.1 ± 4.2 0.08 ± 0.06 0.00 ± 0.00 0.18 ± 0.09 0.00 ± 0.00 0.07 ± 0.05 0.05 ± 0.02

• S.E.S : 6.910
• bserved

expectation

P r e l i m i n a r y

0.33 ± 0.11 (including signal region)

Open the box [unblinding]

1 2 3 4 5 6 7

Pi0RecZ 2000 3000 4000 5000 6000 Pi0Pt 50 100 150 200 250 300 350 400 450 500

P r e l i m i n a r y

4 events! [nothing outside SR]

Kohsaku Tobioka (FSU)

KOTO “excess”?

16

1 2 3 4 5 6 7

Pi0RecZ 2000 3000 4000 5000 6000 Pi0Pt 50 100 150 200 250 300 350 400 450 500 upstream detector On-timing peak is shifted by large pulse

• n-time

waveform of the event measured time 0.08 ± 0.06 0.18 ± 0.09 473.1 ± 4.2 0.00 ± 0.00 0.07 ± 0.05 0.050.02 expectation

P r e l i m i n a r y

Preliminary

clock [8ns] ADC [counts] 0.330.11

1 event is suspected Even 3 events >> SM+BG~0.1.

Kohsaku Tobioka (FSU)

Combine NA62&KOTO, KAON2019

17 % % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

GN bound violated

[Kitahara, Okui, Perez, Soreq, KT (1909.11111)] × B(KL → π0ν¯ ν)KOTO = 2.1+2.0 (+4.1)

−1.1 (−1.7) × 10−9

Kohsaku Tobioka (FSU)

• SM point, inconsistent 


p-value~10-4 [just KL]

• IF GN bound saturates [1D]

still tension of 2.1 σ

• Violation of GN bound in

K→πvv is very difficult.
 [heavy NP is below blue line]

Combine NA62&KOTO, KAON2019

17

BR[KL → π0ν¯ ν] BR[K+ → π+ν¯ ν] ≤ 4.3

=

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

GN bound violated

[Kitahara, Okui, Perez, Soreq, KT (1909.11111)] × B(KL → π0ν¯ ν)KOTO = 2.1+2.0 (+4.1)

−1.1 (−1.7) × 10−9

Kohsaku Tobioka (FSU)

• SM point, inconsistent 


p-value~10-4 [just KL]

• IF GN bound saturates [1D]

still tension of 2.1 σ

• Violation of GN bound in

K→πvv is very difficult.
 [heavy NP is below blue line]

Combine NA62&KOTO, KAON2019

17

If this is NP , a new light state is favored.

BR[KL → π0ν¯ ν] BR[K+ → π+ν¯ ν] ≤ 4.3

=

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

GN bound violated

[Kitahara, Okui, Perez, Soreq, KT (1909.11111)] × B(KL → π0ν¯ ν)KOTO = 2.1+2.0 (+4.1)

−1.1 (−1.7) × 10−9

Kohsaku Tobioka (FSU)

KOTO “excess”, ICHEP2020

18

Post-unblinding analysis found new possible BG(upstream K+) BG=0.05±0.02

KAON2019 ICHEP2020

Charged kaon?

KL

Sweeping magnet 2nd collimator

𝐿𝑀 𝐿±

• 𝐿±/𝐿𝑀 ∼ 1.6 × 10−6

𝐿± → 𝜌0𝑓±𝜉 𝜌0 𝑄𝑢

𝑳𝑴 𝐿± 33 ± ×

KL * collimator →K+→π0e+v [BR~5%], π0π+

Kohsaku Tobioka (FSU)

19

• ◆ SES =

1 𝑂𝐿𝑀𝜗𝑡𝑗𝑕 = 7.1 × 10−10

0.04

• ◆

𝑂𝑝𝑐𝑡 → ◆ 𝐿+

• n

Expected # of BGs in the signal region U: Updated from Kaon2019 N: New

talk @ichep2020

BG=0.05±0.02 → 0.39±0.10

x8 [new K+ BG, MC]

KAON2019 ICHEP2020

Post-unblinding analysis found new possible BG(upstream K+)

KOTO “excess”, ICHEP2020

Kohsaku Tobioka (FSU)

• 𝐿±
• → 1.05 ± 0.28

New New New

Preliminary

# from 𝐿± decays = (0.33±0.08) × uncertainties of simulation

Uncertainty of flux → x 3.0 Uncertainty of the estimation of acceptance → ongoing using 𝑳+ control sample

Prediction by MC simulation 20

talk @ichep2020

It’s still tentative, let’s wait for a paper. BG=0.05±0.02 → 0.39±0.10 → 1.05±0.28

x8 [new K+ BG, MC] [calibrate K+ flux x3]

KAON2019 ICHEP2020

KOTO “excess”, ICHEP2020

Post-unblinding analysis found new possible BG(upstream K+)

Kohsaku Tobioka (FSU)

21

KOTO2019

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

Combine NA62&KOTO, ICHEP2020

ICHEP2020

(A) K+ BG based on MC (B)K+ BG MC x3 [special run]

SM: 3+σ GN tension: 2.1σ

B=0.39±0.10 B=1.05±0.28

Kohsaku Tobioka (FSU)

21

KOTO2019

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

Combine NA62&KOTO, ICHEP2020

ICHEP2020

(A) K+ BG based on MC (B)K+ BG MC x3 [special run]

SM: 3+σ GN tension: 2.1σ

B=0.39±0.10 B=1.05±0.28

• SM:
• GN tension:

2.6σ 1.5σ

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

Kohsaku Tobioka (FSU)

21

KOTO2019

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

Combine NA62&KOTO, ICHEP2020

ICHEP2020

(A) K+ BG based on MC (B)K+ BG MC x3 [special run]

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

1.7σ 0.9σ

SM: 3+σ GN tension: 2.1σ

B=0.39±0.10 B=1.05±0.28

• SM:
• GN tension:

2.6σ 1.5σ

% % %

• ℬ(+→ π+νν)⨯

ℬ(→ πνν)⨯

Kohsaku Tobioka (FSU)

References relevant to the excess

22

• Light new states violating GN bound
• Heavy new physics

EFT: Kitahara, Okui, Perez, Soreq, KT [1909.11111]
 Leptoquark:R. Mandal, A. Pich [1908.11155] Z′: Calibbi, Crivellin, Kirk, Manzari, and Vernazza [1910.00014],
 Aebischer, Buras, Kumar [2006.01138] Generic neutrino interactions: Li, Ma, and Schmidt [1912.10433] Breaking Grossman-Nir: He, Ma, Tandean,and Valencia [2002.05467, 2005.02942]

• Light new state with GN bound

General analysis: Kitahara, Okui, Perez, Soreq, KT [1909.11111] Light dark fermions (do not work): Fabbrichesi and Gabrielli (1911.03755) Light scalars: Fuyuto, Hou, Kohda [1412.4397] Egana-Urinovic, Homiller, and Meade [1911.10203]
 Dev, Mohapatra, and Zhang [1911.12334] Liu, McGinnis, Wagner, and Wang (2001.06522) [muon g-2] Banerjee, Kim, Matsedonskyi, Perez, Safronova [2004.02899]… Light gauge boson: Jho, Lee, S.C. Park, Y. Park, and Tseng [2001.06572]

• Exotic (not in this talk)
• M. Pospelov. Status and phenomenology of light bsm. talk Jan 20, 2019

• R. Ziegler, J. Zupan, R. Zwicky [2005.00451] S. Gori, G. Perez, KT [2005.05170], 

• M. Hostert, K. Kaneta, M. Pospelov [2005.07102], W. Altmannshofer, B. V. Lehmann, S. Profumo [2006.05064]

Fixed target production: Kitahara, Okui, Perez, Soreq, KT [1909.11111]
 Pionium: P. Lichard [arXiv:2006.02969]

Kohsaku Tobioka (FSU)

23

EFT operators for KL→π0vv

Both heavy and light new physics compatible

CS,R − CT ∼ e− 3

4 πi/(75 TeV)2

Best Fit

KAON2019

[1909.11111]

Heavy NP

OS = ¯ L¯ σµL ¯ Q2¯ σµQ1 OT = ¯ Lτ a¯ σµL ¯ Q2τ a¯ σµQ1 OR = ¯ L¯ σµL scτ a¯ σµ ¯ dc

Kohsaku Tobioka (FSU)

23

EFT operators for KL→π0vv

Both heavy and light new physics compatible

CS,R − CT ∼ e− 3

4 πi/(75 TeV)2

Best Fit

KAON2019

[1909.11111]

Heavy NP

OS = ¯ L¯ σµL ¯ Q2¯ σµQ1 OT = ¯ Lτ a¯ σµL ¯ Q2τ a¯ σµQ1 OR = ¯ L¯ σµL scτ a¯ σµ ¯ dc

ICHEP2020

[T.Kitahara]

CS,R − CT ∼ e− 3

4 πi/(78 TeV)2

Kohsaku Tobioka (FSU)

23

EFT operators for KL→π0vv

Both heavy and light new physics compatible

CS,R − CT ∼ e− 3

4 πi/(75 TeV)2

Best Fit

KAON2019

[1909.11111]

KL→π0X X: invisible Light NP Heavy NP

OS = ¯ L¯ σµL ¯ Q2¯ σµQ1 OT = ¯ Lτ a¯ σµL ¯ Q2τ a¯ σµQ1 OR = ¯ L¯ σµL scτ a¯ σµ ¯ dc

ICHEP2020

[T.Kitahara]

CS,R − CT ∼ e− 3

4 πi/(78 TeV)2

Kohsaku Tobioka (FSU)

23

EFT operators for KL→π0vv

Both heavy and light new physics compatible

CS,R − CT ∼ e− 3

4 πi/(75 TeV)2

Best Fit

KAON2019

[1909.11111]

KL→π0X X: invisible Light NP

• =

=

• []
• π[]

→π

• Jacobian peak

accumulate near pT threshold

KT

Heavy NP

OS = ¯ L¯ σµL ¯ Q2¯ σµQ1 OT = ¯ Lτ a¯ σµL ¯ Q2τ a¯ σµQ1 OR = ¯ L¯ σµL scτ a¯ σµ ¯ dc

ICHEP2020

[T.Kitahara]

CS,R − CT ∼ e− 3

4 πi/(78 TeV)2

Kohsaku Tobioka (FSU)

24

Both heavy and light new physics compatible

OS = ¯ L¯ σµL ¯ Q2¯ σµQ1 OT = ¯ Lτ a¯ σµL ¯ Q2τ a¯ σµQ1 OR = ¯ L¯ σµL scτ a¯ σµ ¯ dc

CS,R − CT ∼ e− 3

4 πi/(75 TeV)2

Best Fit

KAON2019 ICHEP2020

[T.Kitahara] [1909.11111]

• ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
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• ℬ(→ π)

ℬ(→ πνν)

• []

ℬ(→ π)⨯

KOTO BG= 0.39±0.10 (Green) 1.05±0.28 (Blue)

Heavy NP Light NP EFT operators for KL→π0vv KL→π0X X: invisible

CS,R − CT ∼ e− 3

4 πi/(78 TeV)2

Kohsaku Tobioka (FSU)

25

• “Excess” leads to novel scenarios [KL is the best probe of NP]


Make KOTO experiment very unique!

Novel Scenarios violating GN bound

Flavor-violating dark sector [single light state] Single light state, generalized GN bound still persists.

OSMX

OSM ⊃ ¯ sd

KL→π0 X K+→π+ X

X: SM gauge singlet mX<350MeV

Kohsaku Tobioka (FSU)

25

• “Excess” leads to novel scenarios [KL is the best probe of NP]


Make KOTO experiment very unique!

Novel Scenarios violating GN bound

Flavor-violating dark sector [single light state] Single light state, generalized GN bound still persists.

OSMX

OSM ⊃ ¯ sd

KL→π0 X K+→π+ X

X: SM gauge singlet mX<350MeV

BR(KL → π0X) . 4.3BR(K+ → π+X)

[H. Leutwyler, M. A. Shifman(’90)]

saturates,e.g., when X is CP-even

Kohsaku Tobioka (FSU)

26

• “Excess” leads to novel scenarios [KL is the best probe of NP]


Make KOTO experiment very unique!

Novel Scenarios violating GN bound

Flavor-violating dark sector [2+ light states]

OSMX1X2

OSM ⊃ ¯ sd

X1,2: SM singlet

KL→XiXj K+→π+XiXj

• M. Pospelov [talk, Jan 2020], S. Gori, G. Perez, KT [2005.05170] M. Hostert, K. Kaneta, M. Pospelov [2005.07102]

violate GN bound

See also R. Ziegler, J. Zupan, R. Zwicky [2005.00451]

Kohsaku Tobioka (FSU)

26

• “Excess” leads to novel scenarios [KL is the best probe of NP]


Make KOTO experiment very unique!

Novel Scenarios violating GN bound

Flavor-violating dark sector [2+ light states]

OSMX1X2

OSM ⊃ ¯ sd

X1,2: SM singlet

KL→XiXj K+→π+XiXj

• M. Pospelov [talk, Jan 2020], S. Gori, G. Perez, KT [2005.05170] M. Hostert, K. Kaneta, M. Pospelov [2005.07102]

violate GN bound

• Neutral particle (e.g., K0, B0) decays directly to dark sector.
• Charged particle decays with extra SM particle (π+) →1/16π2 or forbidden.

X1 X2

γ

KL

X1 π0(γγ)

+

• r

X2 X2 γ

(A) (B)

See also R. Ziegler, J. Zupan, R. Zwicky [2005.00451]

Kohsaku Tobioka (FSU)

Outline

27

✓ Introduction

• Why Kaon? Excellent probe for FIMP
• Rare kaon decay K→πvv at KOTO, and NA62

✓ Recent results from KAON2019 to ICHEP2020

• NA62 results, KOTO “excess”
• New Physics Scenarios
• Future prospects
• Higgs Portal, Muonic Force, Axion-like-particle

Kohsaku Tobioka (FSU)

28

• Even if KOTO “excess” will be gone, 


interesting opportunities for Kaon factories await
 1.Higgs portal bound will be improved by K→π X 2.Muonic Force@NA62. Timely, w/ Fermilab μ g-2, Belle II
 3.ALP search @NA62&KOTO, unexplored range


Kohsaku Tobioka (FSU)

K→π X and Higgs Portal

29

1 10 100 1000 10-11 10-9 10-7 10-5

mϕ[MeV] θ2

NA62 KOTO

SN1987a

B-decay

Relaxion

Belle II LHCb

+CMB-S4

KLEVER BBN

BBN LSND CHARM KOTO NA62

E949

• Light scalar portal φ 


to dark sector

• φ and Higgs mix

θ ∼ Av/m2

h

Aφ|H|2 + h.c.

Kohsaku Tobioka (FSU)

K→π X and Higgs Portal

29

1 10 100 1000 10-11 10-9 10-7 10-5

mϕ[MeV] θ2

NA62 KOTO

SN1987a

B-decay

Relaxion

Belle II LHCb

+CMB-S4

KLEVER BBN

BBN LSND CHARM KOTO NA62

E949

• Light scalar portal φ 


to dark sector

• Current K→π X 


as powerful probes

• Complimentary to

B physics and cosmology

• φ and Higgs mix

θ ∼ Av/m2

h

Aφ|H|2 + h.c.

Kohsaku Tobioka (FSU)

Muonic Force

30

~3.5σ

Fermilab g-2 experiment already more data than BNL ≫new result expected in 2020 In the future, J-PARC g-2 experiment

Kohsaku Tobioka (FSU)

Muonic Force

30

~3.5σ

Fermilab g-2 experiment already more data than BNL ≫new result expected in 2020 In the future, J-PARC g-2 experiment

• A compelling scenario by FIMP

Light muonic force e.g., gauging Lμ-Lτ

.

• S. Baek, N. Deshpande, X. He, and P. Ko, Phys.Rev. 


D64, 055006 (2001), arXiv:hep-ph/0104141 [hep-ph]

Kohsaku Tobioka (FSU)

Muonic Force

30

~3.5σ

Fermilab g-2 experiment already more data than BNL ≫new result expected in 2020 In the future, J-PARC g-2 experiment X

• A compelling scenario by FIMP

Light muonic force e.g., gauging Lμ-Lτ

.

• S. Baek, N. Deshpande, X. He, and P. Ko, Phys.Rev. 


D64, 055006 (2001), arXiv:hep-ph/0104141 [hep-ph]

Kohsaku Tobioka (FSU)

Muonic Force

30

~3.5σ

Fermilab g-2 experiment already more data than BNL ≫new result expected in 2020 In the future, J-PARC g-2 experiment X

• A compelling scenario by FIMP

Light muonic force e.g., gauging Lμ-Lτ

.

• S. Baek, N. Deshpande, X. He, and P. Ko, Phys.Rev. 


D64, 055006 (2001), arXiv:hep-ph/0104141 [hep-ph]

1901.02010,1812.03829, 1804.03144, 1801.10448, …

αX ∼ 10−8

(gX ∼ 4 × 10−4)

mX . mµ

if mX at weak scale
 [Harigaya, Igari, Nojiri, Takeuchi, Tobe,1311.0870]

Kohsaku Tobioka (FSU)

Status of Lμ-Lτ gauge boson

31

Kohsaku Tobioka (FSU)

Status of Lμ-Lτ gauge boson

31

• 1. BaBaR (mV>200MeV)

e+e− → µ+µ−V (→ µ+µ−)

Kohsaku Tobioka (FSU)

Status of Lμ-Lτ gauge boson

31

• 2. Neutrino Trident
• 1. BaBaR (mV>200MeV)

e+e− → µ+µ−V (→ µ+µ−)

CCFR, NuTeV, Charm-II

2.

[W. Altmannshofer, S. Gori,

• M. Pospelov, I. Yavin (‘14)]

V

Kohsaku Tobioka (FSU)

Status of Lμ-Lτ gauge boson

31

• 2. Neutrino Trident
• 3. v-e scattering

[solar v+oscillation]

• 1. BaBaR (mV>200MeV)

e+e− → µ+µ−V (→ µ+µ−)

3.

[R. Harnik, J. Kopp, P.A. Machado(’12);

• Y. Kaneta, T. Shimomura (‘17)]

V

CCFR, NuTeV, Charm-II

2.

[W. Altmannshofer, S. Gori,

• M. Pospelov, I. Yavin (‘14)]

V

Kohsaku Tobioka (FSU)

Status of Lμ-Lτ gauge boson

31

• 2. Neutrino Trident
• 3. v-e scattering

[solar v+oscillation]

• 1. BaBaR (mV>200MeV)

e+e− → µ+µ−V (→ µ+µ−)

3.

[R. Harnik, J. Kopp, P.A. Machado(’12);

• Y. Kaneta, T. Shimomura (‘17)]

V

CCFR, NuTeV, Charm-II

2.

[W. Altmannshofer, S. Gori,

• M. Pospelov, I. Yavin (‘14)]

V

Can we probe parallel to Fermilab g-2?

@K+ [this talk, Ibe, Nakano, Suzuki(1611.08460)] @Belle II [1912.11276, Y.Jho et al(1904.13053)] @ATLAS [I. Galon et al(1906.09272)]

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

32

→ ¯ ν ν

signal: K+→µ+ +inv

*assume only stat. error

Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo, KT 
 [Phys.Rev.Lett. 124 (2020) 041802, 1902.07715]

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

32

→ ¯ ν ν

signal: K+→µ+ +inv

*assume only stat. error

Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo, KT 
 [Phys.Rev.Lett. 124 (2020) 041802, 1902.07715]

0.00 0.05 0.10 0.15 102 103 104 105 106 107 108 109 mmiss2 @GeV2D  events background: 108 K+ signal: aV=10-3

10 MeV

200 MeV 300 MeV

K+ → µ+N

recast

(pK+ − pµ+)2

BG: missed photon halo muon

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

32

→ ¯ ν ν

signal: K+→µ+ +inv

*assume only stat. error

Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo, KT 
 [Phys.Rev.Lett. 124 (2020) 041802, 1902.07715]

0.00 0.05 0.10 0.15 102 103 104 105 106 107 108 109 mmiss2 @GeV2D  events background: 108 K+ signal: aV=10-3

10 MeV

200 MeV 300 MeV

K+ → µ+N

recast

(pK+ − pµ+)2

BG: missed photon halo muon NA62 can cover remaining parameter space!

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

32

→ ¯ ν ν

signal: K+→µ+ +inv

• Remove trigger prescaling 1/400
• Control systematics

Challenges

*assume only stat. error

Gordan Krnjaic, Gustavo Marques-Tavares, Diego Redigolo, KT 
 [Phys.Rev.Lett. 124 (2020) 041802, 1902.07715]

0.00 0.05 0.10 0.15 102 103 104 105 106 107 108 109 mmiss2 @GeV2D  events background: 108 K+ signal: aV=10-3

10 MeV

200 MeV 300 MeV

K+ → µ+N

recast

(pK+ − pµ+)2

BG: missed photon halo muon NA62 can cover remaining parameter space!

Kohsaku Tobioka (FSU)

Heavy Axion, Axion-like Particle

33

10-12 10-7 0.01 1000.00 108 1013 10-17 10-13 10-9 10-5 10-1

[]

• [-]

b r

• a

d res ABRACADABRA A D M X CASPEr-Wind CASPEr-EDM ALPS IIc IAXO

ΔNeff SHiP L I G O Q C D a x i

• n

B e n c h m a r k 1 B e n c h m a r k 2

• s

• p

• a

• a

• Axion/ALP with MeV-GeV mass is poorly explored

DM quality

• P. Agrawal, K. Howe(‘17)

loophole

Kohsaku Tobioka (FSU)

Heavy Axion, Axion-like Particle

33

10-12 10-7 0.01 1000.00 108 1013 10-17 10-13 10-9 10-5 10-1

[]

• [-]

b r

• a

d res ABRACADABRA A D M X CASPEr-Wind CASPEr-EDM ALPS IIc IAXO

ΔNeff SHiP L I G O Q C D a x i

• n

B e n c h m a r k 1 B e n c h m a r k 2

• s

• p

• a

• a

• Axion/ALP with MeV-GeV mass is poorly explored
• Interesting parameter space

by Axion/PQ quality problem [favor low decay constant]

[S. M. Barr, D. Seckel ('92); M. Kamionkowski, J. March-Russell ('92)]

DM quality

• P. Agrawal, K. Howe(‘17)

loophole

Kohsaku Tobioka (FSU)

Heavy Axion, Axion-like Particle

33

10-12 10-7 0.01 1000.00 108 1013 10-17 10-13 10-9 10-5 10-1

[]

• [-]

b r

• a

d res ABRACADABRA A D M X CASPEr-Wind CASPEr-EDM ALPS IIc IAXO

ΔNeff SHiP L I G O Q C D a x i

• n

B e n c h m a r k 1 B e n c h m a r k 2

• s

• p

• a

• a

• Axion/ALP with MeV-GeV mass is poorly explored
• Models Mirror QCD (QCD’x Z2)

[V. Rubakov (’97);…Fukuda, K. Harigaya, M. Ibe, T. T. Yanagida(’15);

• S. Dimopoulos, A. Hook, J. Huang, G. Marques-Tavares(’16), 

• P. Agrawal, K. Howe(‘17)]
• Interesting parameter space

by Axion/PQ quality problem [favor low decay constant]

[S. M. Barr, D. Seckel ('92); M. Kamionkowski, J. March-Russell ('92)]

DM quality

• P. Agrawal, K. Howe(‘17)

loophole

Kohsaku Tobioka (FSU)

+mass term

• EFT

Heavy Axion, Axion-like Particle

34

• Axion/ALP with MeV-GeV mass is poorly explored
• Interesting parameter space

by Axion/PQ quality problem [favor low decay constant]

• Models Mirror QCD (QCD’x Z2)

[V. Rubakov (’97);…Fukuda, K. Harigaya, M. Ibe, T. T. Yanagida(’15);

• S. Dimopoulos, A. Hook, J. Huang, G. Marques-Tavares(’16), 

• P. Agrawal, K. Howe(‘17)]

[S. M. Barr, D. Seckel ('92); M. Kamionkowski, J. March-Russell ('92)]

Kohsaku Tobioka (FSU)

+mass term

• EFT

Heavy Axion, Axion-like Particle

34

Induce KL/K+ decay to axion by π-a mixing or

KL→π0a K+→π+a

• E. Izaguirre,T. Lin,B. Shuve (‘16)
• Axion/ALP with MeV-GeV mass is poorly explored
• Interesting parameter space

by Axion/PQ quality problem [favor low decay constant]

• Models Mirror QCD (QCD’x Z2)

[V. Rubakov (’97);…Fukuda, K. Harigaya, M. Ibe, T. T. Yanagida(’15);

• S. Dimopoulos, A. Hook, J. Huang, G. Marques-Tavares(’16), 

• P. Agrawal, K. Howe(‘17)]

[S. M. Barr, D. Seckel ('92); M. Kamionkowski, J. March-Russell ('92)]

Kohsaku Tobioka (FSU)

+mass term

• EFT

Heavy Axion, Axion-like Particle

34

if a→2γ, new search at KOTO&NA62 Induce KL/K+ decay to axion by π-a mixing or

KL→π0a K+→π+a

• E. Izaguirre,T. Lin,B. Shuve (‘16)
• Axion/ALP with MeV-GeV mass is poorly explored
• Interesting parameter space

by Axion/PQ quality problem [favor low decay constant]

• Models Mirror QCD (QCD’x Z2)

[V. Rubakov (’97);…Fukuda, K. Harigaya, M. Ibe, T. T. Yanagida(’15);

• S. Dimopoulos, A. Hook, J. Huang, G. Marques-Tavares(’16), 

• P. Agrawal, K. Howe(‘17)]

[S. M. Barr, D. Seckel ('92); M. Kamionkowski, J. March-Russell ('92)]

Kohsaku Tobioka (FSU)

Another interesting program [ALPs]

35

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

LEP

E949 [K+] N A 6 2 + 4 8 / 2 [ K

]

GlueX

NA62[K+] πβ

KTEV[KL]

KTEV

E949[K+]

[electron] Beam dump[proton] |θπa|=10% |θπa|=50%

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

NA62[2γ]

KOTO[4γ]

αs 8πFa aG ˜ G

Bounds

NA62&KOTO projection

Many new bounds and projection in S. Gori, G. Perez, KT [2005.05170]

Kohsaku Tobioka (FSU)

Another interesting program [ALPs]

35

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

LEP

E949 [K+] N A 6 2 + 4 8 / 2 [ K

]

GlueX

NA62[K+] πβ

KTEV[KL]

KTEV

E949[K+]

[electron] Beam dump[proton] |θπa|=10% |θπa|=50%

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

NA62[2γ]

KOTO[4γ]

αs 8πFa aG ˜ G

Bounds

NA62&KOTO projection

Many new bounds and projection in S. Gori, G. Perez, KT [2005.05170]

• Updated calculation K+→π+a finds uncertainty 


[two “octet(ΔI=1/2)” enhancements cancel]

Full result, BR[θπ,θη] BR[θπ,θη=0] BR[θπ=0,θη] BR[K+→π+π0]θπ

50 100 150 200 250 300 350 10-10 10-8 10-6 10-4 10-2

ma[MeV]

BR[K+→π+](10 GeV/Fa)2

• H. Georgi, D. B. Kaplan, L. Randall (‘86)

• W. A. Bardeen, R. Peccei, T. Yanagida (’87), also Alves, Weiner(‘17)

Kohsaku Tobioka (FSU)

Another interesting program [ALPs]

36

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

LEP

E949 [K+] N A 6 2 + 4 8 / 2 [ K

]

GlueX

NA62[K+] πβ

KTEV[KL]

KTEV

E949[K+]

[electron] Beam dump[proton] |θπa|=10% |θπa|=50%

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

NA62[2γ]

KOTO[4γ]

αs 8πFa aG ˜ G

Bounds

NA62&KOTO projection

Many new bounds and projection in S. Gori, G. Perez, KT [2005.05170]

• Updated calculation K+→π+a finds uncertainty 


[two “octet(ΔI=1/2)” enhancements cancel]

• KL→π0a is more stable, 


can be enhanced by two-loop without εK

Full result, BR[θπ,θη] BR[θπ,θη=0] BR[θπ=0,θη] BR[KL→π0π0]2θπ

50 100 150 200 250 300 350 10-13 10-11 10-9 10-7 10-5

ma[MeV]

BR[KL→π0](10 GeV/Fa)2

• H. Georgi, D. B. Kaplan, L. Randall (‘86)

• W. A. Bardeen, R. Peccei, T. Yanagida (’87), also Alves, Weiner(‘17)

Kohsaku Tobioka (FSU)

Another interesting program [ALPs]

37

50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

NA62[2γ]

KOTO[4γ]

αs 8πFa aG ˜ G

Bounds

NA62&KOTO projection

Many new bounds and projection in S. Gori, G. Perez, KT [2005.05170]

50 100 150 200 250 300 350 400 10-3 10-4 10-5 10-6

ma[MeV] ℊaW[GeV-1]

NA62[2γ] NA62[0γ] KOTO[2γ]

KOTO[4γ]

gaW 4 aW ˜ W

50 100 150 200 250 300 350 400 10-3 10-4 10-5 10-6

ma[MeV] ℊaW[GeV-1]

CDF[Z]

E949[K+] N A 6 2 + 4 8 / 2 [ K

]

LEP[Z] NA62[K+] KOTO[KL]

KTEV[KL]

KTEV[KL]

E949[K+] Beam dump 50 100 150 200 250 300 350 400 10 0.1 103 104 105 102 10 1

ma[MeV] Fa[GeV]

LEP

E949 [K+] N A 6 2 + 4 8 / 2 [ K

]

GlueX

NA62[K+] πβ

KTEV[KL]

KTEV

E949[K+]

[electron] Beam dump[proton] |θπa|=10% |θπa|=50%

Kohsaku Tobioka (FSU)

Concluding Remarks

38

• NA62 performs well. KOTO “excess” could be BG
• Wait for the paper
• If new BG is really large, 


upstream veto detector is key

• Future
• NA62 and KOTO have opportunities for FIMP
• Muonic force search w/ Fermila g-2
• New ALP search with a→γγ
• New Idea?
• Join Snowmass RF working group 


[RARE PROCESSES AND PRECISION MEASUREMENTS]

Backup

39

Kohsaku Tobioka (FSU)

Look at Frontier Data

40

Rich experimental data are forthcoming, which push frontiers! B: Belle II, LHCb K: NA62, KOTO ν: MicroBoone, LBNE, DUNE, T2HK Long-lived particle: FASER, NA62++, future beam-dump Kaon is an example Pros: running, extremely intense, relevant to lepton and hadron.
 Each one is complementary to others [B-factories, beam dump]

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

41

→ ¯ ν ν

K+ → µ+N

0.00 0.05 0.10 0.15 102 103 104 105 106 107 108 109 mmiss2 @GeV2D  events background: 108 K+ signal: aV=10-3

10 MeV

1 M e V

200 MeV 300 MeV

2015 data [NA62] Data(BG) vs our Signal

[G. Krnjaic, G. Marques-Tavares, D. Redigolo, KT (‘19)]

(pK+ − pµ+)2

BG: missed photon halo muon recast

Kohsaku Tobioka (FSU)

Lμ-Lτ gauge boson at NA62

42

[G. Krnjaic, G. Marques-Tavares, D. Redigolo, KT (‘19)]

• Remove prescaling 1/400
• Control systematics

*assume only stat. error

NA62 can cover remaining parameter space! Challenges