ISSUES FOR THE LONG-RANGE KAON PROGRAM

AT J-PARCNP08 “Kaon Rare Decay Experiments” WG

Thursday, 06 March 2008

Takeshi K. Komatsubara (KEK, J-PARC Center)

be performed with the K1.1 beam line optimized for K+ ! !+""̄ . The limited Phase1 budget allows, however, one primary line and one production-target in the K-Hall [1].An example of preliminary layout of the K-Hall is shown in Fig. 10. A low-energy, two-stage separated K+ beam line, viewing the T1 target at 6 degree and in 24-m long, isconsidered.

Figure 10: Preliminary layout of the K-Hall. “K1.1” to the right is for low-energy K+’s.

To reduce the pion contamination and the background to K+ ! !+""̄ due to beampions scattered into the detector, a K+ beam line with a high K+/!+ ratio (> 3)should be constructed at K-Hall. The K+ momentum must be low (600-800 MeV/c).Right now we are investigating the optimization of the kaon beam line for K+ ! !+""̄at the K-Hall, based on the experience of E787 and E949. An idea is a shorter beamline with lower K+ momentum.

• The counting-rates in the most subsystems related to the beam analysis and photonveto analysis in the E787 and E949 detectors were proportional to the incident kaons,not to the kaons at rest in the target [38]. That means, with the same incident fluxand by lowering the beam momentum (and reducing the amount of material in thedegrader), the kaon stopping fraction increases while accidental hits decrease 6.

6Also, using additional proton intensity to extend the spill length without increasing the instantaneousrate raises the number of kaon decays per hour without impacting the acceptance.

15

KL

extraction: 16 degree

30GeV proton

20m from T1 target

図1.15

:T1標的

1.3.3実験予定

J-PA

RC

E14実験は平成

20年

12月に最初のビームが取り出されビームラインの性能評

価実験が行われる。そのときのビーム強度は設計ビームの

1/10

00である

1011pp

p程度が

予想されており測定項目はビーム形状、ビームコア／ハローのエネルギー分布と

Flux、お

よび!線、ミューオンと熱中性子の

Fluxである。その実験データの解析を行い本実験の

ビームライン設計に反映させ平成

22年から

KL!

"0 ##̄稀崩壊分岐比測定実験を行う予

定である。

20sharing the common

T1 target

developing the plan in the next step

assumption:a) the full intensity of the Phase-1 slow extraction with 30GeV proton is realized - when ? 2011 ? 2013 ?

8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3LINAC Output power <for RCS> ｋW 5.4<0.25> 5.4<0.6> 5.4<1.2>6 15 <18>

Peak current mA 5-25Pulse width msec 50-100 50-250Beam Rep. pps single - 25 single - 25

RCS Output power ｋW 4 4 4 100 250 （280）(MLF) Typical Beam Rep. pps single - 25 single - 25single - 25

No. of Bunches 1 - 2 1 - 2 1- 2 1- 2 1- 2 2Particles /bunch for MLF 4.2E11 4.2E11 8.5E11 4.2E12 1.1E13 1.2E13Particles /bunch for MR (4.2E11) (4.2E11)Particles /ring for MLF 8.3E12 2.1E13Particles /ring for MR (8.3E11) (4.2E11)

MR Output power ｋW 0.12 1.2 3.6 100Energy GeV 3 30Typical Beam Rep. pps 0.3 0.3 - 0.5No. of Bunches 1 - 2 1 - 2 6 6Particles /bunch 4.2E11 4.2E11 4.2E11 1.2E13Particles /ring 8.3E11 8.3E11 2.5E12 7.2E13

HD Output power ｋW 1.2Energy GeV 30Particles /burst 8.3E11

NU Output power ｋW 3.6 100Energy GeV 30Particles /burst 2.5E12 7.2E13

JFY 2008 JFY 2007 JFY2009

- Requirement from T2K: 2.0E20 protons on the ν target by the 2010 summer shutdown. - Guideline :Beam loss at each extraction point < 25 -100 W to keep residual radiation level < 1mSv/h.

Intensity upgrade plan of the first three years

developing the plan in the next step

assumption:a) the full intensity of the Phase-1 slow extraction with 30GeV proton is realized - when ? 2011 ? 2013 ?

b) we construct dedicated beam-line(s) in the existing or extended Hadron Hall. - after physics run of E14, TREK

7

Expectation from NP08

! Neutrinos + Approved Hadrons :

– Reconfirm the construction schedule.

– Desired scenario for the beamtime schedule.

– Needed upgrades for 2009 – 2014.

! Non Approved Experiments:

– Find scientific opportunities.

– Desired location of the experiment.

– Cost (if known) and other requests to the J-PARC.

– Potential participants.

– International contributions, if any.

– Any other issues.

! Preparation for the Users Steering Committee:

– Timeline of all proposed projects.

– Priority setting among individual proposals, if at all possible.

– Demand to the accelerator.

– International competition and/or coordination.

S.Nagamiya’s slide yesterday

KL: E14 (stage-2)K+: TREK (stage-1)

build the beamlines andperform the physics run;

prepare the next step

(discussed in the morning sessions)

What subjects are we going to study,in the Phase 1 experiments (E14, TREK),

to develop the Phase 2 plan ?

What proton beam do we request to the Main Ring ?

50 GeV ? - no big merit in K yield, in photon veto

more intensity ?

duty factor, spill structure ?- optimization in E14, TREK

0.17s

1.4s

0.7-3s

0.67s

2.94-5.24s

probable 30GeV pattern

(h=9)

slow extraction pattern and Beam Power

• Phase-I Extraction Energy 30GeV• Phase-II Extraction Energy 50GeV

Beam Power Final Goal @30GeV330-180 kW (180MeV Linac)540-300 kW (400MeV Linac)

• Reducing beam loss is crucial for slow extraction at the high beam intensity.

• First beam commissioning (low beam power ~1.2kW)

establishment of beam handling technique and stability/reliability for hardware

• Beam intensity would be increased step by step with reducing beam loss toward final goal

What facility do we request for Phase 2 ?

extension of Hadron Hall ? - Should we say we MUST have the extended Hadron Hall ? by 2014 ? - we do not like to have “long shutdown” for it before running E14, TREK

new primary beam (B-line) ? - for KL line with small angle

next to E14 for the B.R. measurement

• Optimized beamline with 5deg angle for

• higher KL momentum <PK>=5.2GeV/c

• higher yield: 4.4E7/2µsr /3E14pot

!"#$%&&'()*+,&'(--&.(/+01&2-(,

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3%$%5&36$4&&7891/:;<

36$45&3%$%&7=91/:;<

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Test line

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Example

next to E14 for the B.R. measurement

• Optimized beamline with 5deg angle for

• higher KL momentum <PK>=5.2GeV/c

• higher yield: 4.4E7/2µsr /3E14pot

Example

What beam-line (kaon flux, purity)do we construct ?

new target station - Ni rod target for KL

extraction angle + length - 5deg + 50m for KL yield

collimation (KL)

DC separation, focusing (K+) - two stages of separation ?

What detector improvementsdo we need (for breakthrough) ?

acceptance

background rejection

rate capability

...

Will we use a new technique or concept of the detetor ?

shower shape discrimination

waveform digitization

new photon detector

new photo-sensors

simulations

...

Aren’t we missing any good ideasto be pursued ?

lower proton energy ?

micro-bunched beam for TOF technique ?

large extraction angle ?

...

10

! RSVP - Rare Symmetry Violating Processes

NSF Major Research Equipment (MRE) proposal ($100M+); FY 06 construction start (possibly 2005)

" MECO, E940, µ- ! e- conversion

" K0PI0, E926, Rare K decay

KL0 ! !0""bar

NSF Abandoned Project in summer 1995

– 2008 STATUS

JPARC P21 (COMET) and/or P20 (PRISM), FNAL Mu2E, Project X

JPARC E14 Stage 2 Approval,FNAL Project X

Status of AGS fixed target experiments as of Sept 2003

back to the future: let us review the slides once again