Skip to content

Far Forward Acceptance Analysis

Overview

This document presents the acceptance analysis for Lambda (Λ) baryons in the Far Forward (FF) detector region of the EPIC detector at the EIC.

  • 5×41 GeV: 5 GeV electron beam on 41 GeV proton beam
  • 10×100 GeV: 10 GeV electron beam on 100 GeV proton beam
  • 10×130 GeV: 10 GeV electron beam on 130 GeV proton beam
  • 18×275 GeV: 18 GeV electron beam on 275 GeV proton beam

Lambda Decay over Energies

Lambda Decay

Lambda Decay Zoom

Lambda Decay Cumulative

Momentum vs decay distance

BeamDistribution Plot
5×41Lambda Distance 5x41
10×100Lambda Distance 10x100
10×130Lambda Distance 10x130
18×275Lambda Distance 18x275

Lambda Decay Products

Lambda decay products (proton and π⁻)

Proton P vs Z endpoint

Energy ConfigurationDecay Distance Distribution
5×41 GeVProton Distance 5x41
10×100 GeVProton Distance 10x100
10×130 GeVProton Distance 10x130
18×275 GeVProton Distance 18x275

π⁻ P vs Z endpoint

The π⁻ from Lambda decay typically has lower momentum and a wider angular distribution compared to the proton.

Energy ConfigurationDecay Distance Distribution
5×41 GeVPion- Distance 5x41
10×100 GeVPion- Distance 10x100
10×130 GeVPion- Distance 10x130
18×275 GeVPion- Distance 18x275

Neutron P vs Z decay distance

Energy ConfigurationNeutron Distribution
5×41 GeVNeutron Distance 5x41
10×100 GeVNeutron Distance 10x100
10×130 GeVNeutron Distance 10x130
18×275 GeVNeutron Distance 18x275

π⁰ P vs Z

Neutral pions may be produced in the fragmentation region or through resonance decays. Their detection relies on electromagnetic calorimetry.

Energy Configurationπ⁰ Distribution
5×41 GeVPion0 Distance 5x41
10×100 GeVPion0 Distance 10x100
10×130 GeVPion0 Distance 10x130
18×275 GeVPion0 Distance 18x275

Detector-Specific Acceptance

The Far Forward region consists of multiple detector subsystems, each optimized for specific particle types and kinematic ranges. The following sections show polar acceptance plots for different particles in various detector components. These plots display the angular distribution of particle hits in a polar coordinate representation, providing insight into the geometric acceptance of each subsystem.

B0 Tracker

The B0 tracker provides tracking coverage close to the beam pipe in the forward direction, essential for detecting high-momentum particles at small angles.

Energy ConfigurationPolar Acceptance
5×41 GeVProton B0 5x41
10×100 GeVProton B0 10x100
18×275 GeVProton B0 18x275

Forward Off-Momentum Tracker

The Forward Off-Momentum (OMD) tracker system captures particles scattered at small angles, including protons from Lambda decays that are slightly deflected from the beam direction.

Energy ConfigurationPolar Acceptance
5×41 GeVProton OMD 5x41
10×100 GeVProton OMD 10x100
18×275 GeVProton OMD 18x275

Forward Roman Pot

The Roman Pot detectors are specialized tracking stations positioned very close to the beam line, designed to detect forward protons at extremely small scattering angles.

Energy ConfigurationPolar Acceptance
5×41 GeVProton RomanPot 5x41
10×100 GeVProton RomanPot 10x100
18×275 GeVProton RomanPot 18x275

Charged Pion Detection

Charged pions from Lambda decay and other sources are detected in the B0 and OMD tracking systems. Both π⁺ and π⁻ are important for understanding the reaction kinematics and backgrounds.

Pion⁺ in B0 Tracker

Energy ConfigurationPolar Acceptance
5×41 GeVPion+ B0 5x41
10×100 GeVPion+ B0 10x100
18×275 GeVPion+ B0 18x275

Pion⁺ in Forward Off-Momentum Tracker

Energy ConfigurationPolar Acceptance
5×41 GeVPion+ OMD 5x41
10×100 GeVPion+ OMD 10x100
18×275 GeVPion+ OMD 18x275

Pion⁻ in Forward Off-Momentum Tracker

The π⁻ from Lambda decay (Λ → p + π⁻) is a critical component for Lambda reconstruction.

Energy ConfigurationPolar Acceptance
5×41 GeVPion- OMD 5x41
10×100 GeVPion- OMD 10x100
18×275 GeVPion- OMD 18x275

Pion Tracking Observations:

  • Pions typically have wider angular distributions than protons from Lambda decays
  • The combination of B0 and OMD provides comprehensive coverage
  • Charge sign determination is essential for distinguishing π⁺ from π⁻
  • Lower momentum pions are more affected by magnetic field deflection

Neutral Particle Detection

Neutral particles (neutrons and π⁰) are detected in calorimetric systems, with the ZDC playing a crucial role for very forward particles.

Neutron Detection in Far Forward ZDC

The hadronic Zero Degree Calorimeter (HCal ZDC) is optimized for neutron detection at very small angles.

Energy ConfigurationPolar Acceptance
5×41 GeVNeutron ZDC 5x41
10×100 GeVNeutron ZDC 10x100
18×275 GeVNeutron ZDC 18x275

π⁰ Detection

Neutral pions are reconstructed through their two-photon decay (π⁰ → γγ) using electromagnetic calorimetry.

π⁰ in B0 ECal:

Energy ConfigurationPolar Acceptance
5×41 GeVPion0 B0ECal 5x41
10×100 GeVPion0 B0ECal 10x100
18×275 GeVPion0 B0ECal 18x275

π⁰ in ECal Far Forward ZDC:

Energy ConfigurationPolar Acceptance
5×41 GeVPion0 ECalZDC 5x41

π⁰ in HCal Far Forward ZDC:

Energy ConfigurationPolar Acceptance
5×41 GeVPion0 HCalZDC 5x41
10×100 GeVPion0 HCalZDC 10x100
18×275 GeVPion0 HCalZDC 18x275

Released under the MIT License.