The J-PARC KOTO Experiment Yau WAH Fermilab Project-X Workshop - - PowerPoint PPT Presentation

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The J-PARC KOTO Experiment Yau WAH Fermilab Project-X Workshop - - PowerPoint PPT Presentation

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The J-PARC KOTO Experiment Yau WAH Fermilab Project-X Workshop June 2012 1 K0 at To kai (KOTO) for the rare decay 2 A short history Earlier searches before E391a were crippled by limited veto abilities. Searches with better

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SLIDE 1

The J-PARC KOTO Experiment

Yau WAH Fermilab Project-X Workshop June 2012

1

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SLIDE 2

K0 at Tokai (KOTO) for the rare decay

2

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SLIDE 3

A short history

  • Earlier searches before E391a were crippled by limited veto abilities.
  • Searches with better kinematics constraint via 0 Dalitz decay (1.2%

br) but with degraded sensitivity.

3

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SLIDE 4

The Basic Strategy

  • Pencil beam
  • Hermetic veto
  • Reconstruction of

0 vertex and Pt assuming 0 mass

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SLIDE 5

Pilot E391 at KEK

  • Decay region in high vacuum(10-7 Torr)

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CsI Calorimeter Charged Veto Main barrel Front Barrel with CC02

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SLIDE 6

MC signal & neutron background after Reconstruction

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BG Estimation CC02 ‘pi0’ 0.6+/-0.4 CV-eta 0.2+/-0.1 CV-pi0 <0.3 Sensitivity of 1.1x10-8

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SLIDE 7

E391a neutron related background

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BG Estimation CC02 ‘pi0’ 0.6+/-0.4 CV-eta 0.2+/-0.1 CV-pi0 <0.3 Neutron interactions with detector close to the beam were the main background sources.

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SLIDE 8

Pilot E391a Result

  • Data plot of blind analysis

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SLIDE 9

Pilot E391 result

  • Data plot of blind analysis, open the box
  • BR( ) < 2.6x10-8(90% CL)

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SLIDE 10

How do we improve:

  • More KL ,less halo neutron  Beam (JPARC, new

beamline)

  • Background and acceptance  Calorimeter and

electronics (1% acceptance to ~ >5%)

  • Background  New veto detectors

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SLIDE 11

Bird’s eye photo in January of 2008

South to North Neutrino Beams (to Kamioka)

JFY2009 Beams

50 GeV Synchrotron Hadron Exp. Facility Materials and Life Experimental Facility

JFY2008 Beams

3 GeV Synchrotron

CY2007 Beams

Lina c Japan-Proton Accelerator Research Center (KEK/JAEA）

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SLIDE 12

Hadron Experimental Hall

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SLIDE 13

The Beam

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To KOTO To beam dump 16o J-PARC E14 KOTO KEK-E391a

  • Primary proton energy

30 GeV 12 GeV

  • Proton intensity(/spill)

2x1014 2.5x1012

  • Spill-length/repetition

0.7s / 3.3s 2s / 4s

  • Extraction angle

16 deg. 4 deg.

  • KL yield(/spill)

8.1x106 3.3x105

  • Average PKL

2.1 GeV/c 2.6 GeV/c

  • n/KL ratio

6.5 45 Ni

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SLIDE 14

The Beamline Design

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SLIDE 15

Target, collimators and sweeping magnets

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SLIDE 16

Beam Survey

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  • K. Shiomi et. al. Nucl. Inst. Meth. A664, 264 (2012):

KL yield consistent with FLUKA; 2.4* GEANT4 QGSP-BERT-CHIPS (proposal) 3 Snowmass year -> <1.5

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SLIDE 17

Comparison of halo neutron momentum

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Neutron Momentum E391a KOTO The halo neutron background is expected to be 0.2 for KOTO. MC study of  particle production

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SLIDE 18

To Further Reduce Neutron Background

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Move CC02 upstream and make it fully active This configuration of CC02 and CV and the new beamline reduce the halo neutron background by a factor of >200.

E391a KOTO

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SLIDE 19

Detector Upgrades

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SLIDE 20

The CsI Calorimeter

E391 CsI crystal 7cmx7cmx30cm 16X0 KTev crystals

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E391a KOTO

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SLIDE 21

The effect of longer CsI crystals

Energy in CsI as a fraction of ncident photon energy

KTeV Crystal E391a Crystal

Reconstructed vertex of MC 0 sample with 0 generated with fixed position.

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Main mechanism for KL

  • >2pi0

background becomes ‘even- paring’ events with two photon missing in veto detectors

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SLIDE 22

KTeV Calorimeter  KOTO Calorimeter(Chicago)

  • New in KOTO: high rate, different energy range,

vacuum, higher timing requirement

  • CW base ->low power
  • Differential outputs to the

125MHz waveform digitizer

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14bit 125MHz pulse shaping FADC

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SLIDE 23

The Gaussian Filter in the FADC

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CsI pulse(inverted). Yellow: filtered Filter circuit

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SLIDE 24

Timing Measurement with an ADC

  • Full pulse sampling allows fitting to determine the time of the pulse
  • Timing measurement is important for veto and reducing acceptance
  • loss. A good timing measurement also have the potential to find the

angle of the photon. The angle measurement suppresses a large class

  • f background.

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ns Timing resolution ~110ps at E=100MeV Smaller pulses have irregular shapes

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SLIDE 25

Readout and Architecture

  • Two level trigger system
  • Fully pipelined system with no delay cable
  • With 48 samples for a pulse, the FADC board can send out

data at a trigger rate of >100kHz. Data throughput: 20GByte/second

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Optical fiber readout FADC Data Flow

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SLIDE 26

Improvements on the Charged Veto (CV)

  • 0.8mm CFRP (carbon fiber reinforced)

mechanical support;

  • Scintillator fiber MPPC both ends readout;
  • Prototype measured light yield 8-10 p.e./100keV

deposited; inefficiency is expected to be <1x10-3;

  • June 2012 verification with beam
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SLIDE 27

Data: Simulation:

  • 1 p.e.
  • MPPC output/1p.e. 50ns pulse 7.5x105 gain
  • Pulse height : 0.24mV/1p.e.
  • Amp out: 12mV/1p.e.
  • FADC: 10mV/1p.e. ~ 80 counts
  • MIP peak
  • 25-50 p.e./single end (FADC:~2000-4000 counts)
  • 50-80 p.e./sum both end
  • 2.3nsec timing resolution achieved
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SLIDE 28

Catching photons down the hole

  • Challenge: ~108 neutrons/0.7

second, and more low energy beam photons(<10MeV)  Lead/Aerogel Cerenkov counter  Readout fast pulses: 500MHz FADC board

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25 modules in total

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SLIDE 29

Expected Performance

  • Energetic photons go down the hole

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SLIDE 30

KOTO Main Barrel(MB)

  • With the improvement in the beam and Calorimeter, the main

background comes from KL

  • >2

with missing photons.

  • Adding another 5X0 to the 14 X0 E391 MB reduces 2

background by a factor of 2.

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Photon Detection Inefficiency E391 MB KOTO MB With angle convoluted

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SLIDE 31

How can we go further?

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Low energy sampling effect dominate For perpendicularly incident photons, 19X0 isn’t enough for punch though. Not many such photons in MB, but many such photons in CsI. This explains why E391a K->2pi0 background comes from ‘punch through’.

  • MB Inefficiency Mechanism MC

Study

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SLIDE 32

Background and Sensitivity

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J-PARC KOTO KEK-E391a improvement KL yield/spill 8.1x106 3.3x105 x30/sec Run time 12 months 2 months x6 Decay prob. 3.6% 2.1% x2 Acceptance 4.7% 1% x3.6 Sensitivity 0.8x10-11 1.1x10-8 x1300

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SLIDE 33

Feb 2012

KLπ+ π-

Event display of a KL3π0candidate

KL3π

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SLIDE 34

Summary

  • KOTO(step 1) is designed to make the first
  • bservation of
  • Construction of other detectors is on-going

and will be completed in Fall 2012.

  • Physics run will start in Fall 2012 with

~30kW for few (?) months and will reach the Grossman-Nir limit.

  • Start preparing beamline for Stage-II.

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SLIDE 35

Basic line : 5degee & 52m from target

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SLIDE 36

Backup

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SLIDE 37
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SLIDE 38
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SLIDE 39

Beam Survey

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With 1-3kW beam

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SLIDE 40

Beam Survey in 2009

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  • K. Shiomi et al, Nucl. Instr. and Meth. A664, 264 (2012)

Halo suppression meets expectation

KL yield measurement

KL yield: 1.94*107 /spill ! 3 snowmass year  <1.5 consistent with FLUKA; 2.5*GEANT4 QGSP-BERT-CHIPS

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SLIDE 41

Fusion

  • To reject fusion events, E391a suffered ~60% acceptance loss. In

KOTO, the fusion background is reduced with a small acceptance loss.

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5cm distance between two photon to identify fusion using KOTO calorimeter; 15cm for E391a photon 2 photons KTeV CsI