The Intersection ofHigh Energy Physics
and Medicine
Milind Purohit, OISTThe Belle II Experiment & Detector
This experiment is at KEK, Tsukuba, Japan
It is designed to collide 4 GeV positrons (e+)
with 7 GeV electrons (e-) with the world’s
highest luminosity ever

Belle II at KEK, Tsukuba, JapanThe Belle II experiment is part of abroad-based search for new physics in
the intensity frontier
Precisely measuring particle collisions
and comparing with theory
The SuperKEKB accelerator
upgrade will provide 40x theluminosity of KEKB and 50x
the data taken with BelleElectrons and positrons will collide to provide useful events >30,000 times per second. The detector needs
to detect the resulting particles, send the data to server farms, and store it for analysis. [In figure: PF-AR = Photon Factory
Advanced Ring]Belle II Detector
BEAST (Backgroundcommissioning detector)
EM Calorimeter:

KL and muon detector:
Resistive Plate Counter (barrel outer layers)
Scintillator + WLSF + MPPC (end-caps ,inner 2 barrel layers)

CsI(Tl), waveform sampling (barrel)
Pure CsI + waveform sampling (end-caps)

Particle Identification

Electrons (7 GeV)

Time-of-Propagation counter (barrel)
Prox. focusing Aerogel RICH (fwd)

Beryllium beam pipe
2cm diameter

Vertex Detector
2 layers DEPFET + 4 layers DSSD

Positrons (4 GeV)

Central Drift ChamberHe(50%):C2H6(50%), small cells, longlever arm, fast electronics
4

The Time of Propagation Detector (TOP)Charged particles produced in Belle2 emit Cherenkov radiation as they traverse
quartz bars in the TOP

Properties of Cherenkov Radiation
Sinceand

For high energy particles, the angle is 41 degreesis given by

In practical terms, the number of photons collected issmall, typically around 50 / cm
Belle2 uses precision timing (resolution better than100 ps) to distinguish photons from K and p
The radiation is polarized in the plane containing theMeasuring Beam Dose with
Cherenkov Emissions (CE)

“Direct in‑water radiation dose measurements using
Cherenkov emission corrected signals from polarization
imaging for a clinical radiotherapy application”, byÉmily Cloutier, Luc Beaulieu, & Louis Archambault[Université Laval, Québec]Scientific Reports (2022) 12:9608
https://doi.org/10.1038/s41598-022-12672-w
The Setup

Emission Angle vs Beam EnergyImages for Four Polarizations

Angle and Degree of Polarization

Reconstructed Doses

Comparison with HEP
Coordinate system is differentOne paper says > 180 MeV is “high energy”
Speed at which dose is delivered is increasingly
important. Want patient to remain still for not too long.
Hence “FLASH” radiotherapy.
Timing of 50 ps not used (yet)Counting of 50 photons would be too low (?)
Use GEANT for detector simulation, ELEGANT foraccelerator simulation
Use terms like “phantom”
Positron Emission Tomography (PET)TitleTitlePositron Emission Tomography (PET)A radionuclide that emits positrons (b+) is injected; it
accumulates in the region of interest; gamma-ray pairsemanate from e+e- annihilation; the line of response orpoint of emission resolution can be improved from a few
ns to ~10 ps.
Better time resolution also helps greatly in 3D
reconstruction.
However, as temporal and spatial resolution improve, theneed for detailed simulation of particles as they passthrough a variety of matter in the patient becomes moreCT Scans

Wikipedia (where the PET pictures are from) has a great video of CT scanreconstruction:https://en.wikipedia.org/wiki/File:Tomographic_reconstruction-_Projection,_Back_projection_and_Filtered_back_projection.webm

Seems perfect for Machine Learning applications

Accelerators
Hospitals need compact devices to acceleratecharged particles needed for irradiation.
The Compact Linear Collider (CLIC) is a TeVscale high-luminosity linear e+e− collider underdevelopment at CERN; the total length will be inthe 11-50 km range.
However, it accelerates particles with a gradientof 72 MV/m, which should allow for compact
generation of electron beams in the 100-300From US DOE’s “Basic Research Needs for High Energy Physics
Detector Research & Development Report”
In this report we summarize the need for new technologies interms of four Grand Challenges. The technologies envisioned
to address them are described in the body of the report. The
Grand Challenges are:

1.Advancing HEP detectors to new regimes of sensitivity
2.Using integration to enable scalability for HEP sensors
3.Building next-generation HEP detectors with novel materials
and advanced techniques
4.Mastering extreme environments and data rates in HEP
experiments

Acknowledgements
Thanks to many Belle 2 physicists whose talks I
borrowed from, including Tom Browder (Univ. ofHawaii), Kazuki Kojima (Nagoya Univ.), … and to theauthors of the various articles cited and Wikipedia!
CLIC information is from CERN’s 2018 report:https://arxiv.org/pdf/1812.06018.pdf
US DOE’s “Basic Research Needs” reportI would also like to thank Dr. Audrius Stundžia, ofTomographix Ltd. in Toronto, Canada for discussions onthese topics.

Extra Slides

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