# Yellow Report Detector PID

Greetings!

This page has been set up to access and document progress within the Particle Identification (PID) Detector Working Group (DWG) convened to study PID technology leading up to the EIC Yellow Report.

## PID Basics

It is assumed that a magnetic spectrometer and a calorimeter system will provide measurements of charged particle momentum and electromagnetic shower energy. This is typically insufficient to identify the species of the particle measured, except for cases such as topological reconstruction such as neutral-V decays (e.g. Λ decay) or displaced vertex (e.g. charm or bottom quark decays). PID systems primarily use some form of velocity determination to distinguish species: electron, pion, Kaon, and proton. Nature supplies several options for velocity or velocity-dependent interactions of particle:

Time of Flight (TOF).
A direct measurement of velocity combining path length as delivered by the tracking system with a start and stop time.
The principle performance-driving factor for any TOF system is the timing resolution.
The highest timing resolution options are sensitive to magnetic field and must be oriented carefully.
Cherenkov Effect
The Chernkov effect results from a polarization of a radiating medium induced by the passage of a charged particle.
The production angle for cherenkov photons goes as ${\displaystyle \cos \left(\theta _{c}\right)={\frac {1}{n\beta }}}$.
Threshold cherenkov counters are typically used for electron ID and fire when ${\displaystyle \beta >{\frac {1}{n}}}$.
Imaging detectors measure ${\displaystyle \theta _{c}}$ via focusing optics and ID all species electron, pion, Kaon, proton.
The principle performance-driving factor of a cherenkov-based system is the index of refraction.
The cherenkov photon generation goes as ${\displaystyle {\frac {dN}{dL}}\sim \sin ^{2}\left(\theta _{c}\right)}$, forcing low index radiators to be long.
Specific Ionization (aka dE/dx)
Rate of ionization is, for some ranges of momentum a strong function of momentum as shown below:
The steepest dependence of ionization rate on velocity is in the Bethe-Bloch regime.
Landau fluctuations complicate the measurement and are typically battled using many samples over a long track length.
Charged particles crossing a step function in refractive index have possibility to release a photon.
These photons can be identified by relatively large energy (typically x-ray regime) and being non-colinear with the track.
Typically high-Z additives to gas detectors (e.g. Xenon) are used to improve x-ray detection efficiency.
High pixelation (as provided by silicon detectors) is typically required to ID off-axis TR photons.

## Detector Technology Evaluation Strategy

The selection of detector technologies for PID will be principally driven by the momentum spectrum of produced particles. The momentum spectrum is drive by a number of factors:

• Collision kinematics (electron energy, hadron energy)
• Direction of ejectile (either captured as ${\displaystyle \eta }$ or ${\displaystyle \theta }$
• Underlying production mechanism.

### Example of Physics Production: Charmed Hadron Decays

Simulating the ejectile spectra is the task of the so-called Physics Working Groups (PWG) and is communicated by them to all detector working groups. Shown here is an example of the output for the production of charm hadrons and their subsequent decay products as a function of momentum and $\displaystyle \eta$ .

The striking feature in this process is the asymmetry in requirements with the highest momentum hadrons produced in the forward eta.

### Standardized Simulation Format from PWG

The PWG convenors have defined a Standard Histogram to Display Kinematics Coverage examples of which are shown here as scavenged from the PWG presentation at the Pavia Workshop:

Plots such as those above are currently evolving from the PWG efforts. The eventual goal is to overlay the detector technology performance with the physics requirements as shown in cartoon fashion below:

### Status of Input from PWG

At the date of this writing (June 15, 2020), the data files are not yet available from the PWG to be used in making the detector requirements plots. Olga reports that they are working hard but have not yet achieved this milestone. We shall instead merely glean comments from the summary slides of Pavia where we can. These comments are summarized in the table below:

Inclusive Reactions
• Renee Fatemi (Kentucky)
• Nobuo Sato (JLab)
• Barak Schmookler (Stony Brook)

Charged Current (CC) x-sec:

• Need full Ecal+Hcal coverage PID requirement
• Detection of final state charged hadrons, neutrons,
photons required for reconstructing kinematics.
CC via Missing Transverse Energy:
• Full HCAL coverage required
General:
• High electron reconstruction efficiencies (10-50 GeV)
SIDIS
• Ralf Seidl (RIKEN)
• Justin Stevens (W&M)
• Anselm Vossen (Duke)
• Bowen Xiao(CCNU, China)

Studying requirements for

• Tracking
• PID
• Displaced vertices
• Hermiticity/Homogeneity
Jets and Heavy Quarks
•  Leticia Mendez (ORNL)
• Brian Page (BNL)
• Frank Petriello (ANL & Northwestern U.)
• Ernst Sichtermann (LBL)
• Ivan Vitev (LANL)

Requirements/Assumptions

• c-jet: PID TBD
• D meson: Assumed perfect PID (required?).

• Near term: Further evaluate detector needs
• Looking ahead towards the EICUG collaboration meeting and 3rd workshop: Iterate detector needs.
• Better than 3 sigma separation of the PID identification
• Good time resolution (<10ns) to reduce background
Diffraction & Tagging
•  Wim Cosyn (Florida)
• Or Hen (MIT)
• Doug Higinbotham (JLab)
• Spencer Klein (LBNL)
• Anna Stasto (PSU)

Processes needing PID

• Sullivan process ep/d -> e + pi/K/X + nucleon
• Spectroscopy
• Vector meson production

## Status Table

p-Range @
Contributes to ${\displaystyle \theta _{c}}$ Parameterized Pro/con External Constraints Simulation
psec TOF
Up to 10 GeV/c
Depends on ${\displaystyle \sigma _{t}}$ and L
N/A YES YES YES YES (CMS)
dual RICH (dRICH)
(aerogel, gas)
2-60 GeV/c @ 1.6 meter

YES

• Chromaticity
• Emission
• Pixelation
• Magnetic Field
• Tracking
YES YES YES
• Simulated with constant momentum
YES
• GEMC/Geant4
• AI-driven Optimization
GEM RICH
(Gas Electron Multiplier)
20 - 50 GeV/c @ 1 meter

YES

• Chromaticity
• (Emission)
• Pixelation
• Tracking
YES YES YES YES
(ePHENIX)
modular RICH (mRICH) 2-10 GeV/c @ 3.0 cm

YES

• Chromaticity
• Emission
• Pixelation
• Tracking
~YES YES YES
(tracking)
YES
• GEMC/Fun4All work in progress
Detection of Internally
Reflected Cherenkov
(DIRC)
0.8 - 6 GeV/c @ 1.7 cm

YES

• Tracking
• Multiple Scattering
• Chromaticity
• Emission
• Pixelation
YES YES YES YES
• GEMC without B-field
${\displaystyle {\frac {dE}{dx}}}$
(TPC)
0.5-3 GeV/c @ 60 cm
${\displaystyle Ne:CF_{4}50:50}$
N/A ~YES
(Parameterized Test Beam)
NO N/A YES
• Fun4All sPHENIX
(TRD)
eID only
p>1 GeV/c
N/A NO NO N/A YES
• GEMC
(HBD)
eID only
0.1-4 GeV/c @ 50 cm
N/A YES
(Measured PHENIX HBD)
NO N/A YES
• Fun4All PHENIX

## Feedback to Complementarity Group

The PID group was asked in August 2020 to provide feedback on a list of questions. The questions and an exposition to clarify the meaning of each question is posted here. Detector complementarity is defined independently in each of three regions: Electron Arm, Central Arm, Hadron Arm, each of which is discussed in detail below.

Arm Electrons $\displaystyle \pi/K/p$ Package 1 Package 2 Package 3 Package 4 Package 5
Resolution PID p-Range Separation
Electron 2-7% / √ E rejection 10^4 ≤ 7 GeV/c > 3-sigma HBD mRICH TRD LAPPD LGAD
Central 10-12% / √ E rejection 10^4 ≤ 5 GeV/c > 3-sigma DIRC dE/dx LGAD
Hadron 10-12% / √ E ≤ 45 GeV/c > 3-sigma dRICH mRICH LAPPD LGAD

## Feedback to Integration Group

The PID group was asked in August 2020 to provide feedback on a list of questions. The questions and an exposition to clarify the meaning of each question is posted here. Detector integration is defined independently in each of three regions: Electron Arm, Central Arm, Hadron Arm, each of which is discussed in detail below.

Arm Electrons $\displaystyle \pi/K/p$ Package 1 Package 2 Package 3 Package 4 Package 5
Resolution PID p-Range Separation
Electron 2-7% / √ E rejection 10^4 ≤ 7 GeV/c > 3-sigma HBD mRICH TRD LAPPD LGAD
Central 10-12% / √ E rejection 10^4 ≤ 5 GeV/c > 3-sigma DIRC dE/dx LGAD
Hadron 10-12% / √ E ≤ 45 GeV/c > 3-sigma dRICH mRICH LAPPD LGAD

## Detector Technology Matrix

Here the co-conveners are confused. We thought that we were to edit & update the detector matrix presented at Pavia:

${\displaystyle \eta }$ Nomenclature Electrons $\displaystyle \pi/K/p$ Technology
Resolution PID p-Range Separation
-3.5 --> -1.0 Backward Detector 2-7% / √ E rejection 10^4 ≤ 7 GeV/c > 3-sigma HBD
mRICH
TRD
LAPPD
-1.0 --> 1.0 Central Detector 10-12% / √ E rejection 10^4 ≤ 5 GeV/c > 3-sigma DIRC
dE/dx
1.0 --> 2.0 Forward Detector-1 10-12% / √ E ≤ 8 GeV/c > 3-sigma dRICH
mRICH
LAPPD
2.0 --> 3.0 Forward Detector-1 10-12% / √ E ≤ 20 GeV/c > 3-sigma dRICH
Gas RICH
TRD
3.0 --> 3.5 Forward Detector-1 10-12% / √ E ≤ 45 GeV/c > 3-sigma dRICH
Gas RICH
TRD

### Electron Arm Detector Technology Options

In the electron arm, the principle goal is the separation of electrons (most often the primary scattered electron) from pion or heavier hadron interference. Several options exist are and listed here:

The HBD developed and operated in the PHENIX experiment at BNL produced 20 photo-electrons on 50 cm of ${\displaystyle CF_{4}}$ gas.
The HBD Threshold for pions was well matched to the $\displaystyle e-\pi$ requirements.
Shorter radiator lengths than 50 cm are possible but require further study.
mRICH
A modular RICH uses a proximity-focused aerogel radiator focussed with a fresnel lens.
The fresnel lens not only focuses the ring, but it also filters low wavelength scattered light.
TRD
The transition radiation detector assists pion rejection at the 5X level and can assist lower momentum technologies.
LAPPD
LAPPD is the current best time resolution device known,
LAPPD uses micro-channel plate amplification of cherenkov light created in a quartz window.
Current best performance is ! 5psec.

### Central Arm Detector Technology Options

The central arm barrel is challenging because of space requirements. PID must be accomplished in a very short detector space, unless the PID is coupled with another detector purpose.

dE/dx
The specific ionization of a particle depends upon velocity.
Some tracking technologies (e.g. TPC) provide dE/dx measurements to aid in PID in the central arm.
DIRC
The DIRC focuses cherenkov light released and internally reflected in a precision quartz bar.
The light is channeled away from the central region for detection.
R&D has advanced the DIRC technology to each well beyond the initial implementation in BaBar.
LGAD is the not current best time resolution device known, however it is able to work in a magnetic field.
LGAD is a silicon-pixel based technology and provives precision tracking at the same time as TOF.
Current best performance is ~ 20 psec.

### Hadron Arm Detector Technology Options

In the hadron arm, we are required to reach the highest possible momenta. Gas cherenkov technology is the only one suited to reach the highest momentum goals, however due to the cherekov threshold, gas cherenkov must be assisted by another technology at the lower momenta

Dual RICH (dRICH)
A dual RICH configuration images both a higher index (aerogel) radiator and a lower index radiator (gas) onto the same focal plane.
This configuration allows the device to span a very wide range in momenta.
mRICH
A modular RICH uses a proximity-focused aerogel radiator focussed with a fresnel lens.
The fresnel lens not only focuses the ring, but it also filters low wavelength scattered light.
It would require gas cherenkov in addition.
LAPPD
LAPPD is the current best time resolution device known,
LAPPD uses micro-channel plate amplification of cherenkov light created in a quartz window.
Current best performance is ! 5psec.
This would need to be assisted by gas cherenkov to reach the highest momentum.
TRD
The transition radiation detector assists pion rejection at the 5X level and can assist lower momentum technologies.
This is used to assist electron ID for decay electrons (e.g. vector meson decay).