CLAS12

CLAS12 is a 12 GeV (gigaelectronvolt) upgrade to the CLAS detector at Jefferson Lab. It includes detectors for detecting protons, neutrons, muons, and electrons.

Purpose
CLAS12 is needed mostly to study generalized parton distributions within the nucleon. Both full large solid angle coverage and high luminosity are required for an efficient GPD program.

Layout
CLAS12 consists of a pre-calorimeter (PCal) and the earlier electromagnetic calorimeter (EC) portions of the CLAS detector.

The CLAS12 detector is divided into the Forward Detector (FD) and the Central Detector (CD).

PCal/EC
The pre-shower calorimeter (PCal) is needed to reconstruct the energy of high-showering particles and to separate pions and photons.

Low Threshold Cherenkov Counter (LTCC)
The LTCC has 6 sectors consisting of lightweight mirrors, light connecting cones, PMTs, magnetic fields. It includes both hyperbolic and elliptical mirrors.

Torus
CLAS12 includes a Torus magnet with a 3.6 T (Tesla) conducting field. It is based on six conducting coils arranged symmetrically around the beam line.

High Threshold Cherenkov Counter (HTCC)
The HTCC uses the Cherenkov Effect to detect fast-moving particles in the CLAS12 detector.

Beamline
The beamline contains several interdependent subsystems for continually controlling and performing diagnostics on the electron flow from the accelerator, through the fixed target, and to the Faraday cup at the beam dump.

Silicon Vertex Tracker (SVT)
The Silicon Vertex Tracker (SVT) is intended to recreate the trajectories of charged tracks with angles between 35 and 125 degrees.

Central Time-of-Flight (CTOF)
The CLAS12 Central Time-of-Flight apparatus is a barrel scintillation detector for triggering and time-of-flight measurements in the central region of the detector. JLab's goal is for the CTOF to achieve a resolution time of 50-60 ps (picoseconds) (1 ps = 1 x 10^-12 s).

Solenoid
CLAS12 features a 5T solenoid field. A magnetic field of this intensity is required for a large opening for charged and neutral particles in the forward hemisphere.

Drift Chambers (DC)
The drift chambers (DC) are wire chambers, or boxes with small fine wires connected from one side to another, and filled with a certain gas (JLab uses a combination of argon and carbon dioxide (CO2)).

Forward Time-of-Flight (FTOF)
The Forward Time-of-Flight system will measure the time-of-flight of charged particles emerging from the target. The average distance from the target to the FTOF counters will be approximately 6 m (600 cm).

CLARA
CLARA (CLAs Reconstruction and Analysis Framework) was created by JLab for network distributed physics data processing applications for CLAS12. It implements Python, Java, and C++ in its Services layer. It also includes multi-threaded and cloud/batch farm support.

CED
CED (CLAS Event Display) is a program developed by Christopher Newport University for Jefferson Lab. It allows users to run simulators based on various parts of the Hall A accelerator at JLab. This program is a 12 GeV simulation update of the 6 GeV application.

GEMC
gemc (GEant4 Monte Carlo) is an application by Jefferson Lab that incorporates Geant4 libraries to simulate particles passing through matter. The definitions for its simulation parameters, such as geometry and fields, can be found in MySQL, C++, text, and GDML databases.

Links
CLAs Reconstruction and Analysis Framework: https://clasweb.jlab.org/wiki/index.php/CLARA

CLAS12 Slow Controls: https://clasweb.jlab.org/wiki/index.php/CLAS12_Slow_Controls

CLAS12 Detector Subsystem Geometry: https://clasweb.jlab.org/wiki/index.php/CLAS12_Detector_Subsystem_Geometry

CLAS12 Drift Chamber Archives: https://clasweb.jlab.org/wiki/index.php/Archives

CLAS12 Software Specifications: http://www.jlab.org/Hall-B/clas12-web/specs/software.pdf

CLAS12 Software Manual: http://www.jlab.org/Hall-B/clas12-software-nov13.pdf