MEXT Roadmap and Belle II

Yutaka USHIRODA June 2020

MEXT Roadmap and Belle II

• Upon successful conclusion of SCJ Master Plan 2020, SuperKEKB/Belle II was called for a proposal as a

candidate project to be listed on MEXT Roadmap 2020.

• SuperKEKB/Belle II is described as a ~10 years plan starting from JFY2020.

• Goals

– Integrated luminosity of 40/ab within 10 years, 50/ab

(soon) after that. 50/ab is the final target of Belle II project.

– Instantaneous luminosity is not put as a numerical goal, but it should be reasonably high to achieve the integrated luminosity goal within the planned timescale.

– Physics: NP, DM, hadrons

MEXT Roadmap

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• Two long shutdowns:

– To replace PXD in 2022

– To replace QCS in 2026 <- chance to upgrade detector

• 2026 detector “upgrade” is foreseen in the proposal of MEXT Roadmap.

– Anything that happens before integrating 50/ab (~11 years from now) is included in the proposal.

• Keep using the name “Belle II”

• Anything after that is not in the scope. Requires another proposal.

• What is written on the proposal:

– We need 23 oku JPY in order to keep detector performance good enough despite increasing risk of instantaneous and cumulative radiation damage. The cost will hopefully be shared with overseas

• Details in the following slides are not explicitly written on the FAs

proposal, but are assumed in the background to determine the size of budget, and are explained to MEXT.

– Changes can be made when needed.

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SVD

R&D of ASICs and production

• Currently use ASIC (APV25) is discontinued and won’t be available any longer.

• Finer processing: 250nm -> 180nm

→ Radiation tolerant, faster, higher channel density

R&D of Narrow pitch silicon sensor and production

• Gives a better vertex resolution using KS

→ Improves the NP finding sensitivity of an important measurement, which is possible only at Belle II.

PXD and SVD suffer from

・Continuous high dose during operation

・Instantaneous very high dose due to machine trouble and dust particles in vacuum pipe.

Radiation damage is a big concern.

→Need spares to replace PXD and SVD.

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Technical challenges

Sensor APV25

Possibly with higher radiation tolerance and

with better performance

Large coverage is essential for full event reconstruction

Areas lost after 3-4 years of runs with full spec.

Areas lost after 4-5 years of runs with full spec.

CDC is essential for Belle II experiment

Gives trigger, charged particle trajectories, dE/dx, …

CDC

Radiation damage will start to kill optical modules on frontend readout boards

30% less power consumption More radiation tolerant

Frontend electronics with

are needed.

Need a development within a few years

before inner part starts to die

MCP-PMT gradually deteriorate due to radiation background.

The 1^st half will be replaced in 2022.

Another half may need to be replaced around 2026, which requires procurement every year.

To replace in 2026

To replace in 2022 MCP-PMT

TOP

To be installed in Belle II

4 MCP-PMT per module

Aerogel 420 HAPDs

• HAPD will withstand 10 years of Belle II operation, but requires replacement after that. However, it is already discontinued.

• Alternative solution (MPPC) is being prepared.

✓ MPPCs are widely used in recent years, low cost and easier to produce (than HAPD).

✓ Detection efficiency is about twice more than HAPD. Also gives a better position resolution. Much better PID performance is expected as a result.

✓ Challenge is in radiation tolerance (under study)

ARICH

64ch MPPC (3780pcs)

• Replace HAPDs with rad-hard MPPCs. Also replace the FEE

Frontend electronics

ARICH

ECL

New scintillator crystals with short time constant (undoped CsI) will suppress the degradation of

performance.

According to the level of degradation, a part of endcap will be replaced.

Degradation in light yield due to radiation damage.

Photo sensors deteriorated due to neutrons Not critical at this moment, but concerns in future since the background is higher than expected.

Undoped CsI Short PMT Readout electronics

IP beam pipe (for new QCS)

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As we exchange QCS, dimensions of IP beam pipe must be modified.

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+ other IR works for detector maintenance

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Assumed profile of KEK’s contribution

EoI, LoI, TDR

Still a

(painted rice cake = castle in the air)

Need more concrete design and coherent effort over the collaboration

~10 oku yen

• HyperKEKB/Belle III ?

– Even higher luminosity – Polarized beam

– …

• Not in the scope of SCJ Masterplan 2020 or MEXT Roadmap 2020

• “R&D” is proposed in KEK Roadmap 2021 (under discussion). The Roadmap will be examined by KEK SAC in early 2021.

– https://www.kek.jp/en/About/Roadmap/

Upgrade beyond 50/ab?

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