- Email: [email protected]
Silicon vertex tracker for PHENIX detector at the central rapidity region
ARTICLE IN PRESS
Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143 www.elsevier.com/locate/nima
Silicon vertex tracker for PHENIX detector at the central rapidity region Atsushi Taketania,b a RIKEN, Wako, Saitama 351-0198, Japan RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
b
Available online 2 March 2005 For the PHENIX collaboration
Abstract We present the status of the silicon vertex tracker for the PHENIX experiment. The purpose of the PHENIX detector is to investigate very high-density and high-temperature matter, so called Quark Gluon Plasma in heavy ion collisions upto 100 GeV/nucleon and spin structure of the nucleon with polarized proton beam up to 250 GeV/beam. We plan to build the silicon vertex tracker to identify the charm and bottom quark decay by using displaced decay vertex, with two inner pixel layers and two outer stripixel layers. The design goal of the displaced vertex resolution is at the level of 30–50 mm in high charged multiplicity environment with minimum material budget requirement to avoid generating background for outer detectors in the PHENIX. r 2005 Elsevier B.V. All rights reserved. PACS: 29.40.WK Keywords: Heavy ion physics spin; Physics; Stripixel; Pixel; RHIC
1. Physics motivation We are investigating characteristics of the Quark Gluon Plasma (QGP) by using heavy ion collisions and the origin of proton spin by using polarized proton–proton collisions. If the gluon density is high enough, charm quark can be produced in addition to the initial proton–proton collisions. The bottom quark can be E-mail address: [email protected].
produced only in the initial proton–proton collisions, since its mass is much heavier than the charm mass. Measuring charm and bottom production will give us the information about early stage of the heavy ion collisions and later stage [1]. Protons consist of quarks and gluons. The spin of the proton should be explained by the sum of spin of quarks and gluons, and their orbital angular momentum. The contribution from quark spin has been measured by the polarized lepton
0168-9002/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.01.050
ARTICLE IN PRESS 138
A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
deep inelastic scattering experiment (DIS). However, it is only 20% of the proton spin. Since the gluons cannot interact with leptons, DIS is not best way to investigate gluon contributions. Therefore polarized proton–proton collision will use gluon and quarks as probes to interact gluons. Heavy flavor quarks are mainly produced from gluon–gluon collisions. So, identifying the heavy flavor quarks and measuring their asymmetry of production cross-section will give us the gluon polarization in the nucleon [2]. In both of QGP and spin physics program, it is important to separate charm and bottom quarks as well separating from light flavor quarks. Fig. 1. View of the current PHENIX detector. It consists of central arms, muon arms, and forward detectors.
2. RHIC and PHENIX RHIC can make collisions of heavy ions up to Au with beam energy up to 100 GeV/nucleon and polarized proton–proton up to 250 GeV/beam with 70% of polarization [3]. The summary of design goal of RHIC is shown in Table 1. Bunches are collided every 106 ns. PHENIX is one of the large scale detectors, which is constructed to detecting photons, electrons, muons, and hadrons with high rate data acquisition capability but having a limited geometrical acceptance [4]. Fig. 1 shows cut view of the current PHENIX detector without silicon vertex tracker. In the central Au–Au collisions at center of mass energy per nucleon 130 GeV, charged multiplicity has been measured as 622 per unit pseudo-rapidity at midrapidity region [5]. Typical central Au–Au event is shown in Fig. 2. There is no magnetic field in order to simplify the event display in this figure.
3. Vertex tracker configuration
Table 1 Summary of RHIC design goal
Beam energy Luminosity Ion species Polarization
Fig. 2. Typical central Au–Au event at the PHENIX.
Heavy ion
Polarized proton
30–100 GeV/nucleon 2 1026 cm2 s1 Upto Gold
30–250 GeV/beam 2 1032 cm2 s1 70%
The charm and bottom quark have slightly longer life time than other light-flavor quarks. For example, the ct of the neutral D1 meson and B1 meson are 123 and 462 mm, respectively [6]. Therefore, silicon vertex tracker near the beam pipe region, which measures displaced vertex from
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
Fig. 3. Side view of the silicon vertex tracker.
139
central heavy ion collisions, the inner two layers are made of pixel detector and outer layer are made of two-dimensional readout stripixel detector. The details of each detector will be described in the later sections. The layout of the detector is shown in Table 2. Hit occupancy is shown in Table 3. The numbers are estimated with central Au–Au collisions at 200 GeV by using HJING event generator and GEANT detector simulator with modeled silicon vertex tracker. The charge sharing among pixels and strips is accounted by the length of track segment projection onto the pixel or strip area. Because the size of the charge diffusion is estimated as 20 mm and much smaller than the strip size, which is 80 mm, the dominant part of charge sharing is treated well. The third layer has the highest occupancy of 4.7%.
4. Pixel detector
Fig. 4. Cross-sectional view from beam pipe direction of the vertex tracker.
collision vertex, can identify the heavy flavor quarks. The PHENIX detector will be upgraded to include a silicon vertex tracker. Figs. 3 and 4 show the side view and crosssectional view of the vertex tracker at central rapidity region. The tracker covers |Z|o1 and almost 2p azimuthally with four layers of sensors. Due to the high charged multiplicity with the
Our pixel detector was originally developed by the ALICE group [7] at CERN. It is produced as p-in-n structure wafer of 200 mm thickness. A pixel cell is defined by p+ implants in one side of the ntype silicon. The pixel dimension is 50 mm in azimuthal direction and 425 mm in the beam direction. The photograph of a corner a pixel sensor is shown in Fig. 5. The sensor depletes typically at 12 V applied to the aluminized n+ implanted continuous back plane. The leakage current is as low as a few nanoamperes per pixel. Every sensor pixel has a contact pad for bumpbonding to the matching electronics pixel on the readout chip. The array of 32 by 256 consist a single sensor and is read-out by a readout chip. Fig. 6 shows the cross-section of a pixel detector assembly. It consists of the sensor chip and the readout chip that is connected via solder bumbonds to sensor chip. Every sensor pixel has a corresponding individual signal processing electronics in the readout chip. They are interconnected with small solder balls (‘‘bump-bonds’’) in a flipchip process. Eight pixel detector assemblies are wire-bonded to a readout bus structure that runs along the detector on top of the sensors. The readout bus is consisted of Aluminum and Kapton as insulator. In Fig. 7, arrangement of the two
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
140
Table 2 Configuration of the each layer VTX
Layer
R1
R2
R3
R4
Geometrical dimensions
R (cm) Dz (cm) Area (cm2)
2.5 21.8 280
5 21.8 560
10 31.8 1240
14 38.2 1600
Channel count
Sensor size R z (cm2) Channel size
1.28 1.36 (256 32 pixels) 50 425 mm2
3.43 6.36 (384 2 strips) 80 mm 3 cm (effective 80 1000 mm2)
Sensors/ladder Ladders Sensors Readout chips Readout channels
28 10 160 160 1,310,720
5 18 90 1080 138,240
Sensor Readout Bus Ladder and cooling Total
0.2% 0.16% 0.14% 0.7% 1.2%
Radiation length (X/X0)
20 320 320 2,621,440
6 26 144 1728 221,184
0.5% 0.8% 0.7% 2.0%
Table 3 Hit occupancy of each layer Layer Layer Layer Layer Layer
1 2 3 4
Detector
Occupancy
Pixel Pixel Strip Strip
0.53% 0.16% 4.5%(x-strip) 2.5%(x-strip)
4.7%(y-strip) 2.7%(y-strip)
Fig. 6. Cross-section of the pixel detector half ladder.
Fig. 5. Photograph of a corner of a pixel sensor.
Fig. 7. Arrangement of two sensor assemblies with four chips per sensor.
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
sensor assemblies with four readout chip per sensor is shown. The readout bus connects all readout chips by wire bonding. The pilot module at outside vertex detector acceptance interfaces the readout chip to a PHENIX data acquisition system. The readout chip has a preamplifier and a discriminator for each individual pixel. The 256 of 32-bits data are sent to the next stage of the data acquisition system at a frequency of 10 MHz. Also, the readout chip provides an ‘‘OR’’ signal of all pixel for each readout clock cycle. This feature can be used as first-level trigger logic. The chips are designed as radiation hardness. The photograph of Aluminum–Kapton bus which is developed by a collaboration of RIKEN
Fig. 8. Photograph of 120mm pitch Aluminum–Kapton readout bus.
141
and KEK is shown in Fig. 8. The pitch of the pattern is 120 mm and width, 40 mm. The thickness of Aluminum layer is 12 mm.
5. Stripixel detector The geometry of the individual pixel of stripixel sensor is shown in the Fig. 9. The sensor has been developed by ‘‘silicon detector development and processing laboratory’’ at BNL [8]. The sensor is a finely segmented detector with 80 by 1000 mm pixels. Each pixel region has two spiral shaped electrode. A penetrating charged particle will deposit the energy on both spirals. A metal strip connects those spirals that are in a straight line (xstrip) and spirals are lined at 4.61 angle (y-strip). This provides a two-dimenstional hit position information from single-sided sensor. The expected diffusion in the 400 mm sensor is 20 mm, which is much larger than the space between two spirals. Fig. 10 shows a schematic view of prototype sensor and its dimensions. The sensitive area is divided into two parts to place the readout pad, and size is 30.7 by 30.0 mm. Number of strips in the sensor is 1536 and 2 384 per each direction. Half of them are associated with Xand other half with Y-direction. Full depletion voltage is measured to be 80 V for 400-mm-thick sensors. We tested first prototype sensors with 250 and 400 mm thickness. The sensors were readout with
Fig. 9. Configuration of stripixel detector.
ARTICLE IN PRESS 142
A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
Fig. 10. Schematic view of the prototype stripixel sensor.
VA2 chips [9], which have 1–3 ms shaping time. It feeds buffered analog signal to outside VME ADC for LINUX-based data acquisition system. The position resolution and the detection efficiency were evaluated with a 90Sr b-source and in the test beam at KEK PS with charged particle momentum of 0.5–2.0 GeV/c. The position resolution was measured from the residuals of hits on reconstructed particle trajectory among multiple sensor layers. It was 23–25 mm and agrees to the expected pffiffiffiffiffi resolution for 80 mm pitch sensor, 80= 12 ¼ 23:1 mm: The lower limit of the detection efficiency is obtained to be 96% [10]. In the RHIC environment, beam bunches are crossing every 106 ns. We decide to use SVX4 chip [11], which was developed by Fermilab/Berkeley collaboration. The SVX4 chip has around 100 ns shaping time. The chip is implemented in the 0.25 mm process and is inherently radiation hard. It has 46-deep analog pipeline for each 128 channel input. The requirement from the PHENIX data acquisition system is holding each data until level 1 trigger decision for 4 ms. Also, chip has pedestal
subtraction capability for level 1 trigger accepted event. For the readout chip layout on the top of the sensor, it is better to relocate wire-bonding pad to longer side of the sensor instead of locating short side of the sensor as show in the Fig. 9. The longer side of each pixel will be place parallel to the beam axis. As a bonus of the modification, inactive area in the beam axis will be minimized. Prototype sensors of the new design sensors are under construction.
6. Conclusion The PHENIX experiment will build silicon vertex tracker to tag heavy-flavor quarks in the heavy ion collision and polarized proton–proton experiments with two inner pixel layers and two outer stripixel layers. Their design performance satisfies requirements for vertex resolution in high hit occupancy environment, within a low material budget constraint.
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
References [1] E. Shuryak, Phys. Rep 61 (1980) 71. [2] G. Bunce, et al., Ann. Rev. Nucl. Part. SDci. 50 (2000) 525. [3] M. Harrison, et al., Nucl. Instr. and Meth. A 499 (2003) 235. [4] K. Adcox, et al., Nucl. Instr. and Meth. A 499 (2003) 469. [5] K. Adcox, et al., Phys. Rev. Let. 86 (2001) 3500.
143
[6] K. Hagiwara, et al., Phys. Rev. D 66 (2002) pp. 010001-39 and 010001-45. [7] http://www.pd.infn.it/spd. [8] Z. Li, et al., Electron beam and laser testing on the novel stripixel detectors, in this proceedings. [9] Ideas ASA (Norway); http://www.ideas.no/. [10] J. Tojo, et al., IEEE Trans. Nucl. Sci. 51 (5) (2004) 2337. [11] http://d0server1.fnal.gov/users/Rapidis/manual.html.
Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143 www.elsevier.com/locate/nima
Silicon vertex tracker for PHENIX detector at the central rapidity region Atsushi Taketania,b a RIKEN, Wako, Saitama 351-0198, Japan RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, USA
b
Available online 2 March 2005 For the PHENIX collaboration
Abstract We present the status of the silicon vertex tracker for the PHENIX experiment. The purpose of the PHENIX detector is to investigate very high-density and high-temperature matter, so called Quark Gluon Plasma in heavy ion collisions upto 100 GeV/nucleon and spin structure of the nucleon with polarized proton beam up to 250 GeV/beam. We plan to build the silicon vertex tracker to identify the charm and bottom quark decay by using displaced decay vertex, with two inner pixel layers and two outer stripixel layers. The design goal of the displaced vertex resolution is at the level of 30–50 mm in high charged multiplicity environment with minimum material budget requirement to avoid generating background for outer detectors in the PHENIX. r 2005 Elsevier B.V. All rights reserved. PACS: 29.40.WK Keywords: Heavy ion physics spin; Physics; Stripixel; Pixel; RHIC
1. Physics motivation We are investigating characteristics of the Quark Gluon Plasma (QGP) by using heavy ion collisions and the origin of proton spin by using polarized proton–proton collisions. If the gluon density is high enough, charm quark can be produced in addition to the initial proton–proton collisions. The bottom quark can be E-mail address: [email protected].
produced only in the initial proton–proton collisions, since its mass is much heavier than the charm mass. Measuring charm and bottom production will give us the information about early stage of the heavy ion collisions and later stage [1]. Protons consist of quarks and gluons. The spin of the proton should be explained by the sum of spin of quarks and gluons, and their orbital angular momentum. The contribution from quark spin has been measured by the polarized lepton
0168-9002/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2005.01.050
ARTICLE IN PRESS 138
A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
deep inelastic scattering experiment (DIS). However, it is only 20% of the proton spin. Since the gluons cannot interact with leptons, DIS is not best way to investigate gluon contributions. Therefore polarized proton–proton collision will use gluon and quarks as probes to interact gluons. Heavy flavor quarks are mainly produced from gluon–gluon collisions. So, identifying the heavy flavor quarks and measuring their asymmetry of production cross-section will give us the gluon polarization in the nucleon [2]. In both of QGP and spin physics program, it is important to separate charm and bottom quarks as well separating from light flavor quarks. Fig. 1. View of the current PHENIX detector. It consists of central arms, muon arms, and forward detectors.
2. RHIC and PHENIX RHIC can make collisions of heavy ions up to Au with beam energy up to 100 GeV/nucleon and polarized proton–proton up to 250 GeV/beam with 70% of polarization [3]. The summary of design goal of RHIC is shown in Table 1. Bunches are collided every 106 ns. PHENIX is one of the large scale detectors, which is constructed to detecting photons, electrons, muons, and hadrons with high rate data acquisition capability but having a limited geometrical acceptance [4]. Fig. 1 shows cut view of the current PHENIX detector without silicon vertex tracker. In the central Au–Au collisions at center of mass energy per nucleon 130 GeV, charged multiplicity has been measured as 622 per unit pseudo-rapidity at midrapidity region [5]. Typical central Au–Au event is shown in Fig. 2. There is no magnetic field in order to simplify the event display in this figure.
3. Vertex tracker configuration
Table 1 Summary of RHIC design goal
Beam energy Luminosity Ion species Polarization
Fig. 2. Typical central Au–Au event at the PHENIX.
Heavy ion
Polarized proton
30–100 GeV/nucleon 2 1026 cm2 s1 Upto Gold
30–250 GeV/beam 2 1032 cm2 s1 70%
The charm and bottom quark have slightly longer life time than other light-flavor quarks. For example, the ct of the neutral D1 meson and B1 meson are 123 and 462 mm, respectively [6]. Therefore, silicon vertex tracker near the beam pipe region, which measures displaced vertex from
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
Fig. 3. Side view of the silicon vertex tracker.
139
central heavy ion collisions, the inner two layers are made of pixel detector and outer layer are made of two-dimensional readout stripixel detector. The details of each detector will be described in the later sections. The layout of the detector is shown in Table 2. Hit occupancy is shown in Table 3. The numbers are estimated with central Au–Au collisions at 200 GeV by using HJING event generator and GEANT detector simulator with modeled silicon vertex tracker. The charge sharing among pixels and strips is accounted by the length of track segment projection onto the pixel or strip area. Because the size of the charge diffusion is estimated as 20 mm and much smaller than the strip size, which is 80 mm, the dominant part of charge sharing is treated well. The third layer has the highest occupancy of 4.7%.
4. Pixel detector
Fig. 4. Cross-sectional view from beam pipe direction of the vertex tracker.
collision vertex, can identify the heavy flavor quarks. The PHENIX detector will be upgraded to include a silicon vertex tracker. Figs. 3 and 4 show the side view and crosssectional view of the vertex tracker at central rapidity region. The tracker covers |Z|o1 and almost 2p azimuthally with four layers of sensors. Due to the high charged multiplicity with the
Our pixel detector was originally developed by the ALICE group [7] at CERN. It is produced as p-in-n structure wafer of 200 mm thickness. A pixel cell is defined by p+ implants in one side of the ntype silicon. The pixel dimension is 50 mm in azimuthal direction and 425 mm in the beam direction. The photograph of a corner a pixel sensor is shown in Fig. 5. The sensor depletes typically at 12 V applied to the aluminized n+ implanted continuous back plane. The leakage current is as low as a few nanoamperes per pixel. Every sensor pixel has a contact pad for bumpbonding to the matching electronics pixel on the readout chip. The array of 32 by 256 consist a single sensor and is read-out by a readout chip. Fig. 6 shows the cross-section of a pixel detector assembly. It consists of the sensor chip and the readout chip that is connected via solder bumbonds to sensor chip. Every sensor pixel has a corresponding individual signal processing electronics in the readout chip. They are interconnected with small solder balls (‘‘bump-bonds’’) in a flipchip process. Eight pixel detector assemblies are wire-bonded to a readout bus structure that runs along the detector on top of the sensors. The readout bus is consisted of Aluminum and Kapton as insulator. In Fig. 7, arrangement of the two
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
140
Table 2 Configuration of the each layer VTX
Layer
R1
R2
R3
R4
Geometrical dimensions
R (cm) Dz (cm) Area (cm2)
2.5 21.8 280
5 21.8 560
10 31.8 1240
14 38.2 1600
Channel count
Sensor size R z (cm2) Channel size
1.28 1.36 (256 32 pixels) 50 425 mm2
3.43 6.36 (384 2 strips) 80 mm 3 cm (effective 80 1000 mm2)
Sensors/ladder Ladders Sensors Readout chips Readout channels
28 10 160 160 1,310,720
5 18 90 1080 138,240
Sensor Readout Bus Ladder and cooling Total
0.2% 0.16% 0.14% 0.7% 1.2%
Radiation length (X/X0)
20 320 320 2,621,440
6 26 144 1728 221,184
0.5% 0.8% 0.7% 2.0%
Table 3 Hit occupancy of each layer Layer Layer Layer Layer Layer
1 2 3 4
Detector
Occupancy
Pixel Pixel Strip Strip
0.53% 0.16% 4.5%(x-strip) 2.5%(x-strip)
4.7%(y-strip) 2.7%(y-strip)
Fig. 6. Cross-section of the pixel detector half ladder.
Fig. 5. Photograph of a corner of a pixel sensor.
Fig. 7. Arrangement of two sensor assemblies with four chips per sensor.
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
sensor assemblies with four readout chip per sensor is shown. The readout bus connects all readout chips by wire bonding. The pilot module at outside vertex detector acceptance interfaces the readout chip to a PHENIX data acquisition system. The readout chip has a preamplifier and a discriminator for each individual pixel. The 256 of 32-bits data are sent to the next stage of the data acquisition system at a frequency of 10 MHz. Also, the readout chip provides an ‘‘OR’’ signal of all pixel for each readout clock cycle. This feature can be used as first-level trigger logic. The chips are designed as radiation hardness. The photograph of Aluminum–Kapton bus which is developed by a collaboration of RIKEN
Fig. 8. Photograph of 120mm pitch Aluminum–Kapton readout bus.
141
and KEK is shown in Fig. 8. The pitch of the pattern is 120 mm and width, 40 mm. The thickness of Aluminum layer is 12 mm.
5. Stripixel detector The geometry of the individual pixel of stripixel sensor is shown in the Fig. 9. The sensor has been developed by ‘‘silicon detector development and processing laboratory’’ at BNL [8]. The sensor is a finely segmented detector with 80 by 1000 mm pixels. Each pixel region has two spiral shaped electrode. A penetrating charged particle will deposit the energy on both spirals. A metal strip connects those spirals that are in a straight line (xstrip) and spirals are lined at 4.61 angle (y-strip). This provides a two-dimenstional hit position information from single-sided sensor. The expected diffusion in the 400 mm sensor is 20 mm, which is much larger than the space between two spirals. Fig. 10 shows a schematic view of prototype sensor and its dimensions. The sensitive area is divided into two parts to place the readout pad, and size is 30.7 by 30.0 mm. Number of strips in the sensor is 1536 and 2 384 per each direction. Half of them are associated with Xand other half with Y-direction. Full depletion voltage is measured to be 80 V for 400-mm-thick sensors. We tested first prototype sensors with 250 and 400 mm thickness. The sensors were readout with
Fig. 9. Configuration of stripixel detector.
ARTICLE IN PRESS 142
A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
Fig. 10. Schematic view of the prototype stripixel sensor.
VA2 chips [9], which have 1–3 ms shaping time. It feeds buffered analog signal to outside VME ADC for LINUX-based data acquisition system. The position resolution and the detection efficiency were evaluated with a 90Sr b-source and in the test beam at KEK PS with charged particle momentum of 0.5–2.0 GeV/c. The position resolution was measured from the residuals of hits on reconstructed particle trajectory among multiple sensor layers. It was 23–25 mm and agrees to the expected pffiffiffiffiffi resolution for 80 mm pitch sensor, 80= 12 ¼ 23:1 mm: The lower limit of the detection efficiency is obtained to be 96% [10]. In the RHIC environment, beam bunches are crossing every 106 ns. We decide to use SVX4 chip [11], which was developed by Fermilab/Berkeley collaboration. The SVX4 chip has around 100 ns shaping time. The chip is implemented in the 0.25 mm process and is inherently radiation hard. It has 46-deep analog pipeline for each 128 channel input. The requirement from the PHENIX data acquisition system is holding each data until level 1 trigger decision for 4 ms. Also, chip has pedestal
subtraction capability for level 1 trigger accepted event. For the readout chip layout on the top of the sensor, it is better to relocate wire-bonding pad to longer side of the sensor instead of locating short side of the sensor as show in the Fig. 9. The longer side of each pixel will be place parallel to the beam axis. As a bonus of the modification, inactive area in the beam axis will be minimized. Prototype sensors of the new design sensors are under construction.
6. Conclusion The PHENIX experiment will build silicon vertex tracker to tag heavy-flavor quarks in the heavy ion collision and polarized proton–proton experiments with two inner pixel layers and two outer stripixel layers. Their design performance satisfies requirements for vertex resolution in high hit occupancy environment, within a low material budget constraint.
ARTICLE IN PRESS A. Taketani / Nuclear Instruments and Methods in Physics Research A 541 (2005) 137–143
References [1] E. Shuryak, Phys. Rep 61 (1980) 71. [2] G. Bunce, et al., Ann. Rev. Nucl. Part. SDci. 50 (2000) 525. [3] M. Harrison, et al., Nucl. Instr. and Meth. A 499 (2003) 235. [4] K. Adcox, et al., Nucl. Instr. and Meth. A 499 (2003) 469. [5] K. Adcox, et al., Phys. Rev. Let. 86 (2001) 3500.
143
[6] K. Hagiwara, et al., Phys. Rev. D 66 (2002) pp. 010001-39 and 010001-45. [7] http://www.pd.infn.it/spd. [8] Z. Li, et al., Electron beam and laser testing on the novel stripixel detectors, in this proceedings. [9] Ideas ASA (Norway); http://www.ideas.no/. [10] J. Tojo, et al., IEEE Trans. Nucl. Sci. 51 (5) (2004) 2337. [11] http://d0server1.fnal.gov/users/Rapidis/manual.html.