Kyoto University H. Nanjo for E391a and K O TO collaboration

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New Developments of Flavor Physics 20091

Kyoto University

H. Nanjo

for E391a and KOTO collaboration

TOK and E391a

Experiment K O

• KEK-PS E391a– The first dedicated experiment for KL .

• J-PARC E14• to measure Br(KL ) at J-PARC

– KOTO (K0 at Tokai)• Japan-USA-Russia-Taiwan-Korea

– 5 countries and 15 institutes.

• Based on E391a collaboration.• New members are joining.

• We aim to discover KL

with the similar method

used in the E391a.

Collaboration

KEKKyotoNDAOsakaSagaYamagataArizona StateChicagoMichiganJINRNational TaiwanPusan NationalSeoulCheonBuk NationalJeju National

Br)in accuracy (10%

K from constraint 0L

• Flavor Physics– Direct CP violation.

– Br(KL0)

• :Complex phase in CKM (Height of unitary triangle)

• Beyond the SM– Rare FCNC process (highly suppressed in SM).

• Br(KL0)=(2.8 0.4) 10-11

– Very Sensitive to new physics(TeV-Scale Physics).

• Small theoretical uncertainty– Short distance physics (>99% due to t quark) 2% uncertainty in (Br ) Golden mode.

Motivation

KOTO Physics Run 20112014

New Physics

Status and Room for New Physics

1015.105.1 1073.1

)%90(1046.1 9 CLBr

)%90(107.6 8 CLBr

Chance to reach TeV-scale New Physics using Kaon Next-Generation World-Wide Kaon Physics

– KEK-PS E391 Run2 – Run3 analysis KOTO

– Grossman-Nir bound– model independent (can be violated if LFV)

– indirect limit from K+ BNL E797/E949

CERN NA62 European Rare-decays Experiments with Kaons , FNAL Project-X

Concept of Experiment• KL beam (proton target)

– neutral beam line » Long beam line Kill particles with shorter lifetime

» Charged particle sweeping magnet.

» Pb photon absorber reduce beam photons

» Collimator shaping (source of beam halo)

– Core : KL, photon, neutron

– Halo : neutron scattering on the surface of collimator

• Detector– () and nothing

• Photon calorimeter and hermetic vetos

Concept of Experiment• How to make KL beam?

– Proton beam Target KL

proton

target

– Proton beam Target KL

» Charged particles

» neutral short-lived particles

» photon

» neutron

proton

target

photon

neutroncharged particle

KLShort Lived

– Proton beam Target KLShaping Collimator» Charged particles

» neutral short-lived particles

» photon

» neutron

proton

target

photon

collimator

KLShort Lived

– Proton beam Target KLShaping Collimator» Charged particles sweeping magnet

» neutral short-lived particles long beam line

» photon Pb absorber (kill but pass KL)

» neutron

proton

target

photon

collimator

PbKLShort Lived

c KL 15000mm 87mm 79mmKS 27mm

– Proton beam Target KLShaping Collimator– core : neutron, photon

– halo : neutron (scattering at Pb /on the surface of collimator)

proton

target

neutron

collimator

halo neutron

core photon, neutron

Concept of Experiment• How to detect KL0?

– () and nothing• Photon calorimeter

proton

target

collimator

halo neutron

– () and nothing• Photon calorimeter and hermetic vetos

– for photons

proton

target

collimator

halo neutron

– for photons and charged particles

proton

target

collimator

halo neutron

core photon, neutron-

• Beam hole veto under huge core /n flux Weaker veto.

proton

target

collimator

halo neutron

• Make beam hole small!

Pencil Beam

proton

target

collimator

halo neutron

• Make beam hole small!

proton

target

collimator

halo neutron

core photon, neutronPencil Beam

Concept of Experiment

proton

target

halo neutron

• How to reconstruct KL0?

– in Calorimeter and nothing– Energy and Position.

– Reconstruct – assuming KL vertex in the beam line thanks to the pencil beam.

– Decide Zvtx with 0 invariant mass .

0 full reconstruction

proton

target

halo neutron

• How to reconstruct KL0?

– in Calorimeter and nothing– Energy and Position.

– Reconstruct – assuming KL vertex in the beam line thanks to the pencil beam.

– Decide Zvtx with 0 invariant mass .

0 full reconstruction

2021 )cos1(2 mEE

Concept of Experiment• Kinematics of KL

– 0 PT-Zvtx Plane (Kinematics and Fiducial)– Higher PT distribution of 0

– Max 231 MeV/c (V-A theory)

– Kaon-orign background• Veto and Kinematics

19ZZKL→2γKL→2γ

KL→2π0KL→2π0

signal regionsignal region

KL→π+π-π0KL→π+π-π00

00 (even)+-0

Signal Region

proton

target

collimator

Pb 0 /0 production

halo neutron

2021 )cos1(2 mEE

• Halo neutron background– halo neutron interact with detector component

create 0 /0 decay to 2 – Vertex position shift due to

• Energy mis-measurement– photonuclear, neutron-contami

• 0 mass

• halo-n background in PT-Zvtx Plane

– Contamination into the signal box

• Point– Suppress halo-n– Lower halo-n momentum– Reduce material– Place it far from

signal region– Veto at 0 production

ZZhalo-n CV-halo-n CV-

halo-n CC02 π0halo-n CC02 π0

signal regionsignal regionhalo-n CV-0halo-n CV-0

2021 )cos1(2 mEE

E391a Experiment• KL production with KEK 12GeV PS

– 2 x 1012 protons on target (POT) per 2sec spill, 4sec cycle– production angle: 4°, KL peak momentum 2GeV/c, n/KL ratio: ~40

• 0 and nothing.– Pure CsI Calorimeter – Hermetic Vetos

• Physics runs– Run I: February to July of 2004

• “Express” analysis with 10% data published in PRD (2006)

– Run II: February to April of 2005 (~ 32 days without break)

• published in PRL(2007)

– Run III: October - December of 2005• Analysis Expect to be finished in 2009

E391 Detector• a

• Decay region– High vacuum: 10-5 Pa

• to suppress the backgroundfrom interactions w/ residual gas

• Detector components– Set in the vacuum: 0.1 Pa

• separating the decay regionfrom the detector regionwith “membrane”: 0.2mmt film

E391a Status• KL

– Run2 Published Phys.Rev.Lett.100,201802(2008)

• No event observed. (BG estimate 0.41)

– Run3 Analysis• ~ 2 times higher sensitivity expect to be finished in 2009

– 3 order to SM sensitivity KOTO

• KL X (Xlight pseudoscalar particle X

– Published with Run2 data Phys.Rev.Lett.102,051802(2009)

• KL X (X– Analysis in final stage with Run3 data.

)%90(107.6 8 CLBr

7 214.3MeV/cmfor )%90(104.2 CLBr

Strategy from E391a to KOTO• High intensity beam

• New beam line (halo-n surpress)

• Detector upgrade (background)

MR(50GeV PS) perimeter~1.6km30 GeV for slow ext.21014 ppp 0.3MW0.7s spill/3.3s repe.

T1 Ni Target

E391 det. at 16 deg line

proton

Exp Hall

20m neutral beamline

High intensity beam• Flux x RunTime x Acceptance ~2.8 SM

eventKOTO E391a (Run2)

Proton energy 30 GeV 12 GeV

Proton intensity 2e14 2.5e12

Spill/cycle 0.7/3.3sec 2/4sec

Extraction Angle

16 deg 4 deg

Solid Angle 9Str 12.6Str

KL yield/spill 7.1e13 2.4e11 x30 /sec

Run Time 3 s.m. years =12 months.

1 month x10

Decay Prob. 4% 2% x 2

Acceptance 3.6%* 0.67% x5

*without Back splash loss

New Beamline

Jan/2009

CollimatorFabrication

We fixed the beamline design and fabrication is on-going.

halo-n surpression• E391 : core tail : 10-3 level

• KOTO : : 10-4 level– softer neutron momentum.– beamline design

Next talk by Shimogawa.

Detector UpgradeNCC

Increase Veto PerformanceReduce halo-n affectionCope with high rate

• NCC : move to upstream, full active pure-CsI, WLS fiber readout. – To reduce halo neutron BG and monitor halo-n itself in stew.

• CsI 7730cm2.52.550cm– Reduce inefficiency, improve energy resolution, discrimination of fusion– CW base with amp. to reduce heat and increase gain.

• CV : 2-layer design Scintillator + WLS fiber + MPPC (light, space, cost)• BHPV : Pb converter + Aerogel Cerenkov radiator + winstone cone light collection.

• (single rate@E391 is ~1MHz ~40MHz @J-PARC impossible totally different.) • MB : increase the thickness To reduce the inefficiency

Summary and prospects• KOTO experiment

to measure Br(KL )• Neutral beamline design is fixed and

fabrication is on-going and delivery and construction in this FY.

• Beamline survey in ~Oct. 2009 with the BL.• Detector upgrade is being designed and

prototype is made and tested toward Engineering run in 2010 and Physics run in 2011.

Kyoto University H. Nanjo for E391a and K O TO collaboration

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