The fDiRC PID Upgrade Detector for GlueX in Hall D · which is only effective up to approximately 2...
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EM Background (arbitrary normalization) at the planned position of the fDiRC. Dotted lines are the planned inner edges of the boxes [2] GlueX is a fixed target (ɣ,p) experiment poised to start taking physics data in 2015. One of the primary physics goals of GlueX is to map out the light meson spectra. Lattice QCD predicts that exotic mesons – those with quantum numbers requiring gluon spin contributions - exist in the mass range that GlueX can probe. The GlueX Detector Analysis of several states requires determining the strange content through emitted pions and kaons. The PID system of the base detector relies especially on time of flight information, which is only effective up to approximately 2 GeV. Upgrading the PID system with the fDiRC will provide coverage to approximately 4.5GeV Expected phase space of the kaons from 4 reactions with TOF coverage overlaid [1] The DiRC Boxes The DiRC is a set of 4.5m long polished quartz bars previously used in the BaBar detector. They work by totally internally reflecting the Cerenkov light to the end of the bar for imaging. The reflection preserves the emission angle, which contains velocity information. Particle Identification Meson spectra from lattice QCD [1] A single photon propagating in a DiRC bar [2] The fDiRC The GlueX proposal to the DoE requests the use of 4 bar boxes. The currently planned geometry has the bars arranged as shown: Planned geometry of the fDiRC. To be placed just in front of the ToF system [2] The readout box is designed to accurately transport the photons from the bars to the PMTs. The 2 mirror provide focusing and an increased path length for greater angular resolution on the PMT plane. Side view of the focusing box and box mounting design [2] The fDiRC PID Upgrade Detector for GlueX in Hall D Background considerations The photon beam in Hall D is capable of high luminosity, which creates a large E&M background near the beam. To avoid overwhelming the detector with the large amount of radiation produced by these highly relativistic elections, a gap in the bars’ coverage is left near the beam. eta2300 phi1850 Purity Base DiRC Base DiRC 0.90 0.37 0.51 0.68 0.74 0.95 0.18 0.38 0.61 0.69 0.99 0.01 0.06 0.28 0.42 h' 2600 y2175 Purity Base DiRC Base DiRC 0.90 0.31 0.49 0.52 0.67 0.95 0.15 0.33 0.39 0.59 0.99 0.00 0.06 0.06 0.23 Calorimetry considerations The fDiRC represents a large radiation length (~15%), and so it must be verified that this will not interfere with calorimetry. ɣ reconstruction was chosen to test this as this analysis depends heavily on the FCAL. From Monte Carlo simulations, it is not expected that this reconstruction will be hindered by the DiRC, as it appears to function as a “pre-radiator,” being so close to the FCAL, which means it’s effect on the energy resolution is small. ɣ reconstruction with and without the DiRC [2] Benefits of the PID Upgrade In order to quantify the effect of the new PID system, the projected output was calculated for a monte carlo sample. Then a BDT was trained with and without the new information. By comparing the selection efficiency for various signal purities of the 2 BDTs, the relative value of the new information can be assessed. References 1. GlueX Collaboration, An initial study of mesons and baryons containing strange quarks with GlueX, A Proposal to the 40 th JLab program Advisory Committee (PAC 40). [arXiv: 1305.1523v1] 2. GlueX Collaboration, A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRC (A proposal to the 42 nd Jefferson Lab Program Advisory Committee)
Transcript of The fDiRC PID Upgrade Detector for GlueX in Hall D · which is only effective up to approximately 2...
EM Background (arbitrary normalization) at the planned position of the fDiRC. Dotted lines are the
planned inner edges of the boxes [2]
GlueX is a fixed target (ɣ,p) experiment poised to start taking physics data in 2015. One of the primary physics goals of GlueX is to map out the light meson spectra. Lattice QCD predicts that exotic mesons – those with quantum numbers requiring gluon spin contributions - exist in the mass range that GlueX can probe.
The GlueX Detector
Analysis of several states requires determining the strange content through emitted pions and kaons. The PID system of the base detector relies especially on time of flight information, which is only effective up to approximately 2 GeV. Upgrading the PID system with the fDiRC will provide coverage to approximately 4.5GeV
Expected phase space of the kaons from 4 reactions with TOF coverage overlaid [1]
The DiRC Boxes
The DiRC is a set of 4.5m long polished quartz bars previously used in the BaBar detector. They work by totally internally reflecting the Cerenkov light to the end of the bar for imaging. The reflection preserves the emission angle, which contains velocity information.
Particle Identification
Meson spectra from lattice QCD [1]
A single photon propagating in a DiRC bar [2]
The fDiRC The GlueX proposal to the DoE requests the use of 4 bar boxes. The currently planned geometry has the bars arranged as shown:
Planned geometry of the fDiRC. To be placed just in front of the ToF system [2]
The readout box is designed to accurately transport the photons from the bars to the PMTs. The 2 mirror provide focusing and an increased path length for greater angular resolution on the PMT plane.
Side view of the focusing box and box mounting design [2]
The fDiRC PID Upgrade Detector for GlueX in Hall D
Background considerations The photon beam in Hall D is capable of high luminosity, which creates a large E&M background near the beam. To avoid overwhelming the detector with the large amount of radiation produced by these highly relativistic elections, a gap in the bars’ coverage is left near the beam.
eta2300 phi1850 Purity Base DiRC Base DiRC
0.90 0.37 0.51 0.68 0.74 0.95 0.18 0.38 0.61 0.69 0.99 0.01 0.06 0.28 0.42
h' 2600 y2175 Purity Base DiRC Base DiRC
0.90 0.31 0.49 0.52 0.67 0.95 0.15 0.33 0.39 0.59 0.99 0.00 0.06 0.06 0.23
Calorimetry considerations
The fDiRC represents a large radiation length (~15%), and so it must be verified that this will not interfere with calorimetry. ɣ reconstruction was chosen to test this as this analysis depends heavily on the FCAL. From Monte Carlo simulations, it is not expected that this reconstruction will be hindered by the DiRC, as it appears to function as a “pre-radiator,” being so close to the FCAL, which means it’s effect on the energy resolution is small.
ɣ reconstruction with and without the DiRC [2]
Benefits of the PID Upgrade In order to quantify the effect of the new PID system, the projected output was calculated for a monte carlo sample. Then a BDT was trained with and without the new information. By comparing the selection efficiency for various signal purities of the 2 BDTs, the relative value of the new information can be assessed.
References 1. GlueX Collaboration, An initial study of mesons and baryons
containing strange quarks with GlueX, A Proposal to the 40th JLab program Advisory Committee (PAC 40). [arXiv: 1305.1523v1]
2. GlueX Collaboration, A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRC (A proposal to the 42nd Jefferson Lab Program Advisory Committee)
