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Design, status and schedule of the sPHENIX experiment at RHIC
Available online at www.sciencedirect.com
Nuclear Physics A 967 (2017) 548–551 www.elsevier.com/locate/nuclphysa
Design, status and schedule of the sPHENIX experiment at RHIC Megan Connors for the sPHENIX Collaboration Georgia State University, Atlanta, Georgia 30303, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
Abstract The 2015 US Nuclear Physics Long Range Plan calls for a state-of-the-art jet and Upsilon detector at RHIC, known as sPHENIX to study the microscopic nature of the QGP, complementing similar studies at the CERN LHC. The sPHENIX detector will provide precision vertexing, tracking and full calorimetry over pseudorapidity |η| < 1.1 and full azimuth at the full RHIC collision rate, delivering unprecedented data sets for jet and upsilon measurements at RHIC. This will enable the three pillars of the sPHENIX physics program, i.e., studies of jet structure modifications, measurements of heavy-flavor tagged jet production and precision upsilon spectroscopy. We present an overview of the sPHENIX detector design, expected construction and running schedule and planned physics program. Keywords: RHIC, heavy ion, calorimeter, jets, heavy flavor
1. Physics Motivation As argued in the 2015 Nuclear Physics Long Range Plan (LRP) [1], understanding the origins of the novel quark-gluon plasma (QGP) properties revealed in the precise heavy-ion measurements now achieved requires new jet and heavy flavor capabilities at RHIC. These capabilities will enable measurements complementary to those available at the LHC, which will map out the temperature evolution of a number of scale-sensitive observables, providing key insights into the underlying dynamics of the QGP. Therefore, the sPHENIX detector has been proposed to measure modifications of the jet substructure, heavy-flavor tagged jets and quarkonia in heavy ion collisions at RHIC [2]. These measurements probe the QGP at various length scales to study the microscope behavior of the QGP. The sPHENIX detector is designed to preform these measurements with an eye toward a future Electron Ion Collider which was also highlighted in the LRP [1]. 2. The sPHENIX Detector To measure rare probes such as jets and quarkonia requires a detector with uniform acceptance that is capable of utilizing the full luminosity capabilities of the RHIC facility. The sPHENIX detector, shown in
http://dx.doi.org/10.1016/j.nuclphysa.2017.05.117 0375-9474/© 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
M. Connors / Nuclear Physics A 967 (2017) 548–551
549
Fig. 1. A drawing of the planned sPHENIX detector with each subsystem labeled.
Figure 1, is equipped with excellent tracking and calorimeter systems, which have full azimuthal acceptance, 0 < φ < 2π, span |η| < 1.1 in rapidity and can record 15 kHz minimum bias triggers in A+A collisions. To achieve the physics goals, the calorimeter system must have good electron identification for heavy flavor tagging, electron/pion separation for quarkonia measurements and single particle energy resolution of better √ than 100%/ E for jet measurements. Tracking is required to have a good momentum resolution up to 40 GeV/c for jet fragmentation functions, di-electron invariant mass resolution better than 100 MeV/c2 to distinguish the different Upsilon states, and excellent distance of closest approach (DCA) resolution to tag heavy-flavor events. Since momentum measurements require a magnetic field, sPHENIX is designed around a 1.4 T solenoid magnet. The solenoid, previously used in the BaBar experiment, is 3.8 m long and has an inner diameter of 2.8 m. It is currently at Brookhaven National Laboratory in preparation for sPHENIX and successfully passed a low current test in 2016. A full field test is planned for 2017. The tracking system includes monolithic active pixel sensors (MAPS) closest to the beam pipe, silicon strips at an intermediate radius (INTT) and a compact time projection chamber (TPC). The TPC spans 2078 cm radial and will have a continuous, non-gated readout. The INTT is composed of layers of silicon strips and will utilize electronics from the PHENIX silicon detectors. The MAPS detector contains three layers of silicon sensors and is based on the ALICE Inner Tracking System (ITS) upgrade [4]. The MAPS detector will provide 25 μm spatial resolution down to pT = 1–2 GeV/c. Continued improvements to the implementation of the tracking system in simulations are being used in finalizing the tracking design. The calorimeter system includes an electromagnetic calorimeter (EMCal) and an inner hadronic calorimeter located inside the solenoid as well as an outer hadronic calorimeter (HCal) outside the solenoid. The EMCal is composed of projective towers of tungsten with embedded fibers. The HCals have alternating layers of steel plates and scintillator tiles. The layers of the inner HCal are tilted in one direction and the outer HCal layers are tilted in the opposite direction. They are both tilted such that a particle with a straight trajectory from the interaction point through the detector will traverse through four layers of scintillator in each HCal. To verify the performance of these detectors and confirm the simulations, a prototype of the calorimeter system was built and tested.
Measured Energy (GeV)
18 16 14 12
σ(E)/
M. Connors / Nuclear Physics A 967 (2017) 548–551
550
UIUC 10° Incident Angle 2 Fit, Einput - 0.0018*Einput THP 10° Incident Angle 2 Fit, Einput - 0.0009*Einput UIUC 45° Incident Angle 2 Fit, 1.09*Einput + 0.0007*Einput
0.2 UIUC 10° Incident Angle
0.18
Fit, Δ E/E = 2% (δ p/p) ⊕ 2.8% ⊕ 15.5%/ E THP 10° Incident Angle
0.16
Fit, Δ E/E = 2% (δ p/p) ⊕ 2.9% ⊕ 16.1%/ E
0.14
UIUC 45° Incident Angle
10 8
0.12
6
0.1
4
Fit, Δ E/E = 2% (δ p/p) ⊕ 0% ⊕ 14.6%/ E
0.08
Measured Energy Input Energy
2
0.06
0 1.1
0.04
1.05
0.02
1 0.95 0.9
2
4
6
8
10
12
14
16
Input Energy (GeV)
0
2
4
6
8
10
12
14
16
Energy (GeV)
Fig. 2. A measurement of the linearity of the energy response (left) and the energy resolution (right) for electrons in the EMCal.
3. Prototype of the Calorimeter System Prototypes of the sPHENIX EMCal and HCals were tested at the Fermilab Test Beam Facility (FTBF) in April 2016 as the T-1044 experiment [3]. The FTBF provides primary proton beams of 120 GeV and lower energy secondary beams. For T-1044, beams of 1–32 GeV containing a mixture of electrons and pions were studied. A Chrenkov detector was used to select electron or pion events. The EMCal prototype consists of 32 blocks corresponding to 64 towers. Each block contains scintillating fibers embedded in absorber material and two lightguides. The absorber material is a mixture of tungsten powder and epoxy which provides a radiation length of 0.7 cm and sampling fraction for EM-showers of 2.3%. Each lightguide corresponds to one tower and is read out by silicon photomultipliers (SiPMs). The linearity and energy resolution for the EMCal from the √test beam results are shown in Figure 2. The energy resolution for electrons is ΔE/E = 2.8% ⊕ 15.5%/ E. This resolution meets the physics-driven specifications for sPHENIX. At the 2016 test beam, behind the EMCal was the inner HCal followed by a mock cryostat and finally the outer HCal. The mock cryostat allowed particles traversing the prototypes to experience the same number of interaction lengths of material as a particle in the actual sPHENIX would experience as it passed through the solenoid magnet. Each HCal prototype included 20 layers of scintillator tiles corresponding to a total of 16 towers, since each layer included four tiles placed side by side horizontally and tiles were bundled into groups of five before being readout as a single tower. Each tile is embedded with a wavelength shifting fiber which is then read out by a single SiPM. The fiber routing depends on the shape of the tile which depends on tiles position in rapidity. The 2016 prototype used the mid-rapidity configuration. The calibration of the HCal system for hadron showers depends on where the shower started. The linearity and energy resolution for hadronic showers starting in the EMCal (black), inner HCal (red) and outer HCal (blue) are plotted in Figure 3. The fits to the energy resolution data show that the calorimeter system satisfies the sPHENIX requirement that √ the single particle energy resolution be 100%/ E or better. Additional studies shown in [3] demonstrate the excellent agreement between the test beam data and the GEANT4 simulation results. A beam test of prototypes of the calorimeters at large rapidity including 2D projective EMCal towers was underway in February 2017 (during this conference).
Resolution (σE/)
M. Connors / Nuclear Physics A 967 (2017) 548–551
551
1.2
EMCAL+HCALIN+HCALOUT 1
ΔE/E = 2%(δp/p) ⊕ 13.5% ⊕ 64.9%/ E
0.8
ΔE/E = 2%(δp/p) ⊕ 14.5% ⊕ 74.9%/ E
0.6
ΔE/E = 2%(δp/p) ⊕ 17.1% ⊕ 75.5%/ E
HCALIN+HCALOUT (EMCAL MIP)
HCALOUT (EMCAL+HCALIN MIP)
0.4
0.2
0 0
5
10
15
20
25
30
35
40
Input Energy (GeV) Fig. 3. The hadron resolution for the sPHENIX prototype.
4. Collaboration and Schedule The sPHENIX collaboration officially formed in December 2015 following the recommendation in the Nuclear Science Long Range Plan. At the time of this conference the collaboration includes 62 institutes and 235 collaborators but involvement continues to grow. In the fall of 2016, the Department of Energy (DOE) recognized the need for sPHENIX by granting it CD-0, the first phase of an official DOE project. Construction is expected to start in 2018 and finish in 2021 with sPHENIX ready to start taking data for its anticipated multi-year physics program beginning in 2022. The LRP also recommends the construction of an Electron Ion Collider, and BNL is planning how to build upon RHIC to realize such a facility. In concert with that effort, the cold QCD topical group within the collaboration is studying how sPHENIX could serve as the foundation for a capable EIC detector to measure the nuclear parton distribution functions, the partonic structure of the proton, low-x saturation effects, diffraction, hadronization and other key EIC observables. In conclusion, sPHENIX is an official DOE project, which will start taking data in 2022. It is designed to make precise measurements of the jet substructure, heavy-flavor tagged jets and quarkonia in heavy ion collisions at RHIC. These measurements are essential in establishing a complete understanding of the behavior of the QGP. In addition, capabilities and possible upgrades are being explored for sPHENIX to measure cold QCD physics. sPHENIX consists of a tracking system and calorimeter system designed around a solenoid magnet. Prototypes of the calorimeter have been studied at a test beam. Results for the mid-rapidity configuration are consistent with the GEANT4 simulations and satisfy the energy resolution requirements necessary to achieve the sPHENIX program goals. The analysis of the large rapidity configuration, tested in February 2017, is ongoing. sPHENIX is on track to start data collection in 2022 and will provide precise measurements of probes which will enhance our understanding of the QGP. References [1] Reaching For the Horizon, The 2015 Long Range Plan for Nuclear Science, http://science.energy.gov/~/media/np/ nsac/pdf/2015LRP/2015_LRPNS_091815.pdf (DOE,NSF) [2] A. Adare, et al., An Upgrade Proposal from the PHENIX Collaboration, arXiv:1501.06197 [3] C.A. Aidala, et al., Design and Beam Test Results for the sPHENIX Electromagnetic and Hadronic Calorimeter Prototypes arXiv:1704.01461 [4] B. Abelev et al. [ALICE Collaboration], Technical Design Report for the Upgrade of the ALICE Inner Tracking System, J. Phys. G 41, 087002 (2014). doi:10.1088/0954-3899/41/8/087002
Nuclear Physics A 967 (2017) 548–551 www.elsevier.com/locate/nuclphysa
Design, status and schedule of the sPHENIX experiment at RHIC Megan Connors for the sPHENIX Collaboration Georgia State University, Atlanta, Georgia 30303, USA RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
Abstract The 2015 US Nuclear Physics Long Range Plan calls for a state-of-the-art jet and Upsilon detector at RHIC, known as sPHENIX to study the microscopic nature of the QGP, complementing similar studies at the CERN LHC. The sPHENIX detector will provide precision vertexing, tracking and full calorimetry over pseudorapidity |η| < 1.1 and full azimuth at the full RHIC collision rate, delivering unprecedented data sets for jet and upsilon measurements at RHIC. This will enable the three pillars of the sPHENIX physics program, i.e., studies of jet structure modifications, measurements of heavy-flavor tagged jet production and precision upsilon spectroscopy. We present an overview of the sPHENIX detector design, expected construction and running schedule and planned physics program. Keywords: RHIC, heavy ion, calorimeter, jets, heavy flavor
1. Physics Motivation As argued in the 2015 Nuclear Physics Long Range Plan (LRP) [1], understanding the origins of the novel quark-gluon plasma (QGP) properties revealed in the precise heavy-ion measurements now achieved requires new jet and heavy flavor capabilities at RHIC. These capabilities will enable measurements complementary to those available at the LHC, which will map out the temperature evolution of a number of scale-sensitive observables, providing key insights into the underlying dynamics of the QGP. Therefore, the sPHENIX detector has been proposed to measure modifications of the jet substructure, heavy-flavor tagged jets and quarkonia in heavy ion collisions at RHIC [2]. These measurements probe the QGP at various length scales to study the microscope behavior of the QGP. The sPHENIX detector is designed to preform these measurements with an eye toward a future Electron Ion Collider which was also highlighted in the LRP [1]. 2. The sPHENIX Detector To measure rare probes such as jets and quarkonia requires a detector with uniform acceptance that is capable of utilizing the full luminosity capabilities of the RHIC facility. The sPHENIX detector, shown in
http://dx.doi.org/10.1016/j.nuclphysa.2017.05.117 0375-9474/© 2017 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
M. Connors / Nuclear Physics A 967 (2017) 548–551
549
Fig. 1. A drawing of the planned sPHENIX detector with each subsystem labeled.
Figure 1, is equipped with excellent tracking and calorimeter systems, which have full azimuthal acceptance, 0 < φ < 2π, span |η| < 1.1 in rapidity and can record 15 kHz minimum bias triggers in A+A collisions. To achieve the physics goals, the calorimeter system must have good electron identification for heavy flavor tagging, electron/pion separation for quarkonia measurements and single particle energy resolution of better √ than 100%/ E for jet measurements. Tracking is required to have a good momentum resolution up to 40 GeV/c for jet fragmentation functions, di-electron invariant mass resolution better than 100 MeV/c2 to distinguish the different Upsilon states, and excellent distance of closest approach (DCA) resolution to tag heavy-flavor events. Since momentum measurements require a magnetic field, sPHENIX is designed around a 1.4 T solenoid magnet. The solenoid, previously used in the BaBar experiment, is 3.8 m long and has an inner diameter of 2.8 m. It is currently at Brookhaven National Laboratory in preparation for sPHENIX and successfully passed a low current test in 2016. A full field test is planned for 2017. The tracking system includes monolithic active pixel sensors (MAPS) closest to the beam pipe, silicon strips at an intermediate radius (INTT) and a compact time projection chamber (TPC). The TPC spans 2078 cm radial and will have a continuous, non-gated readout. The INTT is composed of layers of silicon strips and will utilize electronics from the PHENIX silicon detectors. The MAPS detector contains three layers of silicon sensors and is based on the ALICE Inner Tracking System (ITS) upgrade [4]. The MAPS detector will provide 25 μm spatial resolution down to pT = 1–2 GeV/c. Continued improvements to the implementation of the tracking system in simulations are being used in finalizing the tracking design. The calorimeter system includes an electromagnetic calorimeter (EMCal) and an inner hadronic calorimeter located inside the solenoid as well as an outer hadronic calorimeter (HCal) outside the solenoid. The EMCal is composed of projective towers of tungsten with embedded fibers. The HCals have alternating layers of steel plates and scintillator tiles. The layers of the inner HCal are tilted in one direction and the outer HCal layers are tilted in the opposite direction. They are both tilted such that a particle with a straight trajectory from the interaction point through the detector will traverse through four layers of scintillator in each HCal. To verify the performance of these detectors and confirm the simulations, a prototype of the calorimeter system was built and tested.
Measured Energy (GeV)
18 16 14 12
σ(E)/
M. Connors / Nuclear Physics A 967 (2017) 548–551
550
UIUC 10° Incident Angle 2 Fit, Einput - 0.0018*Einput THP 10° Incident Angle 2 Fit, Einput - 0.0009*Einput UIUC 45° Incident Angle 2 Fit, 1.09*Einput + 0.0007*Einput
0.2 UIUC 10° Incident Angle
0.18
Fit, Δ E/E = 2% (δ p/p) ⊕ 2.8% ⊕ 15.5%/ E THP 10° Incident Angle
0.16
Fit, Δ E/E = 2% (δ p/p) ⊕ 2.9% ⊕ 16.1%/ E
0.14
UIUC 45° Incident Angle
10 8
0.12
6
0.1
4
Fit, Δ E/E = 2% (δ p/p) ⊕ 0% ⊕ 14.6%/ E
0.08
Measured Energy Input Energy
2
0.06
0 1.1
0.04
1.05
0.02
1 0.95 0.9
2
4
6
8
10
12
14
16
Input Energy (GeV)
0
2
4
6
8
10
12
14
16
Energy (GeV)
Fig. 2. A measurement of the linearity of the energy response (left) and the energy resolution (right) for electrons in the EMCal.
3. Prototype of the Calorimeter System Prototypes of the sPHENIX EMCal and HCals were tested at the Fermilab Test Beam Facility (FTBF) in April 2016 as the T-1044 experiment [3]. The FTBF provides primary proton beams of 120 GeV and lower energy secondary beams. For T-1044, beams of 1–32 GeV containing a mixture of electrons and pions were studied. A Chrenkov detector was used to select electron or pion events. The EMCal prototype consists of 32 blocks corresponding to 64 towers. Each block contains scintillating fibers embedded in absorber material and two lightguides. The absorber material is a mixture of tungsten powder and epoxy which provides a radiation length of 0.7 cm and sampling fraction for EM-showers of 2.3%. Each lightguide corresponds to one tower and is read out by silicon photomultipliers (SiPMs). The linearity and energy resolution for the EMCal from the √test beam results are shown in Figure 2. The energy resolution for electrons is ΔE/E = 2.8% ⊕ 15.5%/ E. This resolution meets the physics-driven specifications for sPHENIX. At the 2016 test beam, behind the EMCal was the inner HCal followed by a mock cryostat and finally the outer HCal. The mock cryostat allowed particles traversing the prototypes to experience the same number of interaction lengths of material as a particle in the actual sPHENIX would experience as it passed through the solenoid magnet. Each HCal prototype included 20 layers of scintillator tiles corresponding to a total of 16 towers, since each layer included four tiles placed side by side horizontally and tiles were bundled into groups of five before being readout as a single tower. Each tile is embedded with a wavelength shifting fiber which is then read out by a single SiPM. The fiber routing depends on the shape of the tile which depends on tiles position in rapidity. The 2016 prototype used the mid-rapidity configuration. The calibration of the HCal system for hadron showers depends on where the shower started. The linearity and energy resolution for hadronic showers starting in the EMCal (black), inner HCal (red) and outer HCal (blue) are plotted in Figure 3. The fits to the energy resolution data show that the calorimeter system satisfies the sPHENIX requirement that √ the single particle energy resolution be 100%/ E or better. Additional studies shown in [3] demonstrate the excellent agreement between the test beam data and the GEANT4 simulation results. A beam test of prototypes of the calorimeters at large rapidity including 2D projective EMCal towers was underway in February 2017 (during this conference).
Resolution (σE/
M. Connors / Nuclear Physics A 967 (2017) 548–551
551
1.2
EMCAL+HCALIN+HCALOUT 1
ΔE/E = 2%(δp/p) ⊕ 13.5% ⊕ 64.9%/ E
0.8
ΔE/E = 2%(δp/p) ⊕ 14.5% ⊕ 74.9%/ E
0.6
ΔE/E = 2%(δp/p) ⊕ 17.1% ⊕ 75.5%/ E
HCALIN+HCALOUT (EMCAL MIP)
HCALOUT (EMCAL+HCALIN MIP)
0.4
0.2
0 0
5
10
15
20
25
30
35
40
Input Energy (GeV) Fig. 3. The hadron resolution for the sPHENIX prototype.
4. Collaboration and Schedule The sPHENIX collaboration officially formed in December 2015 following the recommendation in the Nuclear Science Long Range Plan. At the time of this conference the collaboration includes 62 institutes and 235 collaborators but involvement continues to grow. In the fall of 2016, the Department of Energy (DOE) recognized the need for sPHENIX by granting it CD-0, the first phase of an official DOE project. Construction is expected to start in 2018 and finish in 2021 with sPHENIX ready to start taking data for its anticipated multi-year physics program beginning in 2022. The LRP also recommends the construction of an Electron Ion Collider, and BNL is planning how to build upon RHIC to realize such a facility. In concert with that effort, the cold QCD topical group within the collaboration is studying how sPHENIX could serve as the foundation for a capable EIC detector to measure the nuclear parton distribution functions, the partonic structure of the proton, low-x saturation effects, diffraction, hadronization and other key EIC observables. In conclusion, sPHENIX is an official DOE project, which will start taking data in 2022. It is designed to make precise measurements of the jet substructure, heavy-flavor tagged jets and quarkonia in heavy ion collisions at RHIC. These measurements are essential in establishing a complete understanding of the behavior of the QGP. In addition, capabilities and possible upgrades are being explored for sPHENIX to measure cold QCD physics. sPHENIX consists of a tracking system and calorimeter system designed around a solenoid magnet. Prototypes of the calorimeter have been studied at a test beam. Results for the mid-rapidity configuration are consistent with the GEANT4 simulations and satisfy the energy resolution requirements necessary to achieve the sPHENIX program goals. The analysis of the large rapidity configuration, tested in February 2017, is ongoing. sPHENIX is on track to start data collection in 2022 and will provide precise measurements of probes which will enhance our understanding of the QGP. References [1] Reaching For the Horizon, The 2015 Long Range Plan for Nuclear Science, http://science.energy.gov/~/media/np/ nsac/pdf/2015LRP/2015_LRPNS_091815.pdf (DOE,NSF) [2] A. Adare, et al., An Upgrade Proposal from the PHENIX Collaboration, arXiv:1501.06197 [3] C.A. Aidala, et al., Design and Beam Test Results for the sPHENIX Electromagnetic and Hadronic Calorimeter Prototypes arXiv:1704.01461 [4] B. Abelev et al. [ALICE Collaboration], Technical Design Report for the Upgrade of the ALICE Inner Tracking System, J. Phys. G 41, 087002 (2014). doi:10.1088/0954-3899/41/8/087002