Muon - Electron Conversion at J-PARC COMET-PRISM/PRIME

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Muon - Electron Conversion at J-PARC

COMET-PRISM/PRIME

Ed HungerfordUniversity of Houston

for the COMET Collaboration

5/30/09 Ed Hungerford for the COMET collaboration 1

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Imperial College London, UKImperial College London, UK A. Kurup, J. Pasternak, Y. Uchida,A. Kurup, J. Pasternak, Y. Uchida, P. Dauncey, U. Egede, P. P. Dauncey, U. Egede, P. Dornan,Dornan, and L. Jennerand L. JennerUniversity College London, University College London, UKUK M. Wing, M. Lancaster, M. Wing, M. Lancaster, and R. D’Arcy*and R. D’Arcy*

The COMET-PRISM Collaboration

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Department of physics and astronomy, Department of physics and astronomy, University of British Columbia, Vancouver, University of British Columbia, Vancouver, CanadaCanada D. Bryman D. Bryman TRIUMF, CanadaTRIUMF, Canada T. NumaoT. Numao

43 people from 13 institutes ( 25th May 2009 )

Department of Physics, Department of Physics, Brookhaven National Laboratory, USABrookhaven National Laboratory, USA R. PalmerR. PalmerY. Cui Y. Cui Department of Physics, University of Department of Physics, University of Houston, USAHouston, USA E. Hungerford E. HungerfordK. LauK. Lau


Institute for Chemical Research, Kyoto University, Institute for Chemical Research, Kyoto University, Kyoto, JapanKyoto, Japan Y. Iwashita,Y. Iwashita,Department of Physics, Osaka University, JapanDepartment of Physics, Osaka University, Japan M. Aoki, Md.I. Hossain, T. Itahashi, Y. Kuno, N. Nakadozono*, M. Aoki, Md.I. Hossain, T. Itahashi, Y. Kuno, N. Nakadozono*, A. Sato, T. Tachimoto* and M. YoshidaA. Sato, T. Tachimoto* and M. YoshidaDepartment of Physics, Saitama University, JapanDepartment of Physics, Saitama University, Japan M. Koike and J. SatoM. Koike and J. SatoDepartment of Physics, Tohoku University, JapanDepartment of Physics, Tohoku University, Japan Y. Takubo,Y. Takubo,High Energy Accelerator Research Organization (KEK), High Energy Accelerator Research Organization (KEK), JapanJapan Y. Arimoto, Y. Igarashi, S. Ishimoto, S. Mihara, H. Y. Arimoto, Y. Igarashi, S. Ishimoto, S. Mihara, H. Nishiguchi, Nishiguchi, T. Ogitsu, M. Tomizawa, A. Yamamoto, and K. YoshimuraT. Ogitsu, M. Tomizawa, A. Yamamoto, and K. YoshimuraInstitute for Cosmic Ray Research, JapanInstitute for Cosmic Ray Research, Japan M. YamanakaM. Yamanaka

JINR, Dubna, RussiaJINR, Dubna, Russia V. Kalinnikov, A. Moiseenko, V. Kalinnikov, A. Moiseenko, D. Mzhavia, J. Pontecorvo, D. Mzhavia, J. Pontecorvo, B. Sabirov, Z. Tsamaiaidze, B. Sabirov, Z. Tsamaiaidze, and P. Evtukhouvichand P. Evtukhouvich

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COMET Muon-to-Electron (μ-e) Conversion Lepton Flavor Violation

Muonic Atom

nucleus


μ Decay in Orbit (DIO)μ- → e- ν ν

Lepton Flavor Changes by one unit

Coherent Conversionμ- + A →e-+ A

Nuclear Capture μ- + A →ν+ [N +(A-1)]

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COMET Introductionto

COMET-PRISM/PRIME

• COMET (Phase I)PRISIM/PRIME (Phase II) is a search for coherent, neutrino-less conversion of muons to electron (μ-e conversion) at a single sensitivity of 0f 0.5x10-1610-18

• The experiment offers a powerful probe for new physics beyond the Standard Model.

• It will be undertaken at J-PARC. Phase I (COMET) uses a slow-extracted, bunched 8 GeV proton beam from the J-PARC main ring.

• A proposal was submit to J-PARC Dec. 2007, and a Conceptual Design Report submitted June 2009. COMET now has Stage-1 approval from the J-PARC PAC (July 2009).

• The Collaboration is completing R&D for a TDR.


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COMET The SINDRUM-II Experiment (at PSI)Published Results


SINDRUM-II used a continuous muon beam from the PSI cyclotron. To eliminate beam related background from the beam, a beam-veto counter was used.

This technology cannot be used with higher beam rates in modern beamlines.

COMETAl Target

SINDRUM

Signal at`muon mass

DIO

DIO

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Sensitivities

SUSY-Seesaw Model ( SUSY-GUT SO(10) )

A. Masiero et al., J. High Energy Phys. B. JHEP03, (2004) 046.


Present Sindrum Limit

B(μ → e + )10-13

B(μ + Al → e + Al) < 10-16COMET

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Prediction from SUSY-SU(5)


Tan( ) = ( h2/ h1) ; = higgsino mass

J. Hisano, T. Moroi, K. Tobe and M. Yamaguchi, Phys. Lett. B 391, 341 (1997)

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05-30-09 Ed Hungerford

for the COMET collaboration

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• Electron ResolutionMinimal Detector Material – Thin, Low Z Vacuum EnvironmentREDUNDENT measurements of the electron track

• RatesUp to 500 kHZ single ratesLarge channel countR/O timing (~1-2ns) and analog information

• Dynamic Range Protons 30-40 times Eloss for MIP Pileup and saturation Maintain MIP track efficiency

• Low-Power, Low-foot print electronicsHeatSignal Transmission, inside-to -outside the vacuumNoise

• REDUNDANCY Redundancy (Redundancy, Redundancy, Redundancy) Ambiguous hits, dead channels, accidentalsReconstruction of ghost tracks

• Robust measurements

Design Considerations for COMET (and generally all)

μ to e Experiments

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COMET COMET PRISM at J-PARC


Early Realization Phase II

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COMET J-PARCJapan Proton Accelerator Research Complex

3 GeV Rapid-Cycling Synchrotron, RCS (25 Hz, 1MW ）

Hadron Beam Facility

NP-Hall

Neutrino to Kamiokande

50 GeV Main Ring Synchrotron (0.75 MW)

500 m

Linac (330m)

PRISM-Phase2PRISM-Phase1


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μ→eγ and μ-e Conversion

Background Challenge beam intensity

• μ→eγ accidentals detector resolution limited

• μ-e conversion beam beam

background Less limited• μ→eγ : Accidental background is given by (rate)2. To push

sensitivity the detector resolutions and timing must be improved. However, (in particular for the photon) it would be hard to better MEG with present technology. The ultimate sensitivity is about 10-14 (with a run of 108/sec).

• μ-e conversion : Improvement of a muon beam is possible, both in purity (no pions) and in intensity (thanks to muon collider R&D). A higher beam intensity can be used with present timing because no coincidence is required.


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Overview of COMET


Proton Beam

The Muon Source•Proton Target•Pion Capture•Muon Transport

The Detector•Muon Stopping Target•Electron Transport•Electron Detection

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Comparison to MECO

• Proton Target– tungsten (MECO)– graphite (J-PARC)

• Muon Transport– Magnetic field distributions are different.– Efficiency of the muon transport is almost the same.

• Spectrometer– For 1011 stopping muons/sec– Straight Solenoid (MECO)

• ~500 kHz/wire– Curved Solenoid (J-PARC)

• ~ 300 DIO Hz /detector• Detector Wire Planes rather than

straws

MECO

COMET


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COMET Target and Detector Solenoids

•a muon stopping target, curved solenoid,tracking chambers, and a calorimeter/trigger and cosmic-ray shields.


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Background Rejection (preliminary)


Backgrounds Events Comments

(1)

Muon decay in orbitRadiative muon captureMuon capture with neutron emissionMuon capture with charged particle emission

0.05<0.001<0.001<0.001

230 keV resolution

(2)

Radiative pion capture*Radiative pion captureMuon decay in flight*Pion decay in flight*Beam electrons*Neutron induced*Antiproton induced

0.120.002<0.02

<0.0010.08

0.0240.007

promptlate arriving pions

for high energy neutronsfor 8 GeV protons

(3) Cosmic-ray inducedPattern recognition errors

0.10<0.001

10-4 veto efficiency

Total 0.4

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Signal Sensitivity

• Single event sensitivity Nμ is a number of stopping

muons in the muon stopping target which is 6x1017 muons.

– fcap is a fraction of muon capture, which is 0.6 for aluminum.

– Ae is the detector acceptance, which is 0.07.

total protonsmuon transport efficiencymuon stopping efficiency

8x1020

0.00710.26

# of stopped muons 1.5x1018


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Summary

• COMET is a Phase I search for coherent, neutrino-less conversion of muons to electron (μ-e conversion) at a single event sensitivity of 10-16

• The experiment offers a powerful probe for new physics beyond the Standard Model.

• The experiment will be undertaken at the J-PARC NP Hall using a slowly-extracted, bunched proton beam from the J-PARC main ring.

• More Advanced design, attempting to reduce backgrounds and miss-constructed electron trajectories

• The Experiment is developing a TDR and refining design details. The experiment has completed a CDR and has Stage-1 approval of the J-PARC PAC.

• As a follow-on to COMET, PRISM/PRIME (Phase II) would reach a sensitivity of 10-18. It requires a new beam line, new hall, and a muon storage ring


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04/24/23 18

Supplementary Slides

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Backgrounds

Background rejection is crucial in single-event/few–event searches• Avoids statistical separation of events from background• Conspiring events can mimic a signal• It’s always the background that you don’t predict

which imposes the limits - (Redundancy, Redundancy, Redundancy, )


Intrinsic backgrounds

Beam induced on the Stopping Target, Slits and

Solenoid Walls

•muon decay in orbit (DIO)•radiative muon capture•muon capture with particle emission

Beam-related backgrounds

caused by beam particles, such as electrons, pions,

muons, and anti-protons in a beam

•radiative pion capture•muon decay in flight•pion decay in flight•beam electrons•neutron induced •antiproton induced

Other background cosmic rays •cosmic-ray

•pattern recognition errors

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The MELC/MECO Proposals

Cancelled in 2005

MELC (Russia) MECO (BNL)

•To eliminate beam related background, beam pulsing was adopted (with delayed measurement).•To increase number of muons pion capture in a high-field solenoidal .•Curved solenoid used for momentum pre- selection


The MECO Experiment

at BNL

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Pion Capture Solenoid

• A large muon yield can be achieved by a large solid angle, pion-capture, high- field solenoid surrounding the proton target.

• B=5T,R=0.2m, PT=150MeV/c.

• Superconducting Solenoid Magnet for pion capture

• 15 cm radius bore• a 5 tesla solenoidal field• 30 cm thick tungsten radiation shield• heat load from radiation• a large stored energy


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COMET Electron Detection (preliminary)

Wire Plane Trackers for electron momentum • Vacuum in constant 1T magnetic field.• Straw tube 25μm walls, 5 mm diameter.• One plane has 4 views (x ,y) + (x’,y’) • Five planes are placed 48 cm apart• 250μm position resolution.• σ = 230 keV/c (multiple scattering

dominated.)

Electron calorimeter •Triggers R/O•Redundant Energy Measurement• Candidates are GSO or LSO(LYSO).•APD readout .


16 Wire Units 5 mm Wire spacing 208 wires/array832 wires/plane4160 wires/detector

Trigger Calorimeter

Wire Plane Tracker

~1.2m

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Cosmic Ray Shields

• Both passive and active shields are used.• Passive shields

– 2 meter of concrete and 0.5 m of steel• Active shields

– layers of scintillator veto counters (~1% inefficiency)


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Schematic of System Readout

FE ASIC

FE ASIC

AnalogBuffer

ADC

LocalReadoutControl

(in CPLD)

W Section SectionReadoutControl(FPGA)

PlaneReadoutControl

Off-lineDatabase

Each plane will have its own data link to send data from the detector.In each plane, the readout sequence is organized in sections.Each section is controlled by a FPGA.Locally, there is a CPLD to control the A-to-D conversion.

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Muon Transport Solenoids

• Muons are transported from the capture section to the detector by the muon transport beamline.

• Requirements :– long enough for pions to

decay to muons (> 20 meters ≈ 2x10-3).

– high transport efficiency – negative charge selection– low momentum cut (Pμ>75 MeV/c)

• Straight + curved solenoid transport system to select momentum and charge


Muon - Electron Conversion at J-PARC COMET-PRISM/PRIME

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