- Email: [email protected]
The VHMPID RICH upgrade project for ALICE at LHC
Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
The VHMPID RICH upgrade project for ALICE at LHC A. Di Mauro a,n, A. Agocs b, R. Alfaro c, G.G. Barnafoldi b, G. Bencze b, L. Boldizsar b, E. Cuautle d, G. DeCataldo e, E. Denes b, D. DiBari e, I. Dominguez d, Z. Fodor b, E. Futo b, E. Garcia f, G. Hamar b, J.W. Harris g, P. Levai b, C. Lipusz b, P. Martinengo a, D. Mayani d, L. Molnar a, E. Nappi e, A. Ortiz d, G. Paic d, C. Pastore e, D. Perini a, V. Peskov a,d, F. Piuz a, S. Pochybova b, I. Sgura e, N. Smirnov g, C. Son h, J.B. Van Beelen a, D. Varga i, G. Volpe e, J. Yi h, I.K. Yoo h a
CERN, Geneva, Switzerland MTA KFKI RMKI, Budapest, Hungary Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, Mexico d Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, Mexico e Universita degli Studi di Bari, Dipartimento Interateneo di Fisica ‘‘M.Merlin’’ & INFN Sezione di Bari, Bari, Italy f Chicago StateUniversity, Chicago, USA g YaleUniversity, New Haven, USA h Pusan National University, Pusan, Republic of Korea i Eotvos University, Budapest, Hungary b c
a r t i c l e i n f o
a b s t r a c t
Available online 8 November 2010
RHIC results have shown the importance of high momentum particles as hard probes and the need for particle identification (PID) in a very large momentum range. A Very High Momentum PID (VHMPID) detector has been proposed as upgrade of ALICE to extend the track-by-track identification capabilities for charged hadrons from the present 5 GeV/c limit to the momentum range 10–30 GeV/c. The VHMPID detector is a focusing RICH using C4F10 gaseous radiator coupled to a CsI-based photon detector. Detector design studies, achievable Cherenkov angle resolution, expected performance and high momentum triggering will be discussed. & 2010 Elsevier B.V. All rights reserved.
Keywords: RICH Gaseous detectors Photon detection CsI photoconverter ALICE
1. Introduction A Large Ion Collider Experiment (ALICE) has been designed to study quark-gluon plasma in heavy ion collisions at the LHC, but also p+p collision studies are relevant part of the physics program. The ALICE detector has a unique capability to identify a wide variety of particles [1]; however its momentum coverage for track-by-track identification should be extended to meet new physics challenges at LHC. Indeed, the anomalous baryon/meson ratio observed at RHIC in the momentum range 2–8 GeV/c [2] is expected to extend even higher in pt at LHC energies [3,4]. A Very High Momentum PID (VHMPID) RICH detector has been proposed as ALICE upgrade to perform charged hadrons track-by-track identification in the range 10–30 GeV/c and specifically address physics with ‘‘jets’’ [5]. The present paper will review the status of studies carried out on detector layout, expected performance and dedicated trigger system.
2. Detector layout and design issues The momentum range of interest for PID has driven the choice towards a focusing RICH detector with C4F10 gaseous radiator [6]. n
Corresponding author. E-mail address: [email protected] (A. Di Mauro).
0168-9002/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2010.10.103
The small available space inside the ALICE detector results in limitations of radiator length and geometrical acceptance. This last parameter, combined with the expected low charged particle yield at high momentum [7], makes necessary the implementation of a high-pt trigger to maximize the event rate. One trigger option, as discussed later, consists in a new dedicated detector to be integrated in the same volume available for the full VHMPID system, thus resulting in further limitations on the radiator length. The expected large photosensitive area of about 3 m2 and the operation inside the magnetic field of 0.5 T of the ALICE solenoid suggests to exploit the experience gained with CsI-based gaseous photon detectors for the ALICE HMPID RICH [8,9] and for other similar RICH counters (HADES [10], COMPASS [11]), more than exploring other solutions like vacuum or solid state devices which are significantly less cost-effective or not suitable for this application. The principle scheme of the proposed VHMPID RICH detector has been presented in other publications [5,6]. The Cherenkov photons produced in a C4F10 gaseous radiator (L¼80 cm) are focused by a spherical mirror through a SiO2 (or CaF2) window onto an HMPID-like photon detector, a MWPC coupled to CsI photocathode segmented into 8 8.4 mm2 pads. As alternative option, a thick-GEM based photon detector with reflective CsI photo-converter is under study [12]. The mirror has a lightweight carbon-fiber substrate, a material which minimizes the material for traversing particles and is fluorocarbon-compatible, thus not
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
275
Table 1 Contributions to the resolution (from chromatic, emission point and pixel errors), the total resolution per photoelectron, the mean number of reconstructed photoelectrons for particles at saturation (from MonteCarlo simulation) and the resolution per track, for the proposed RICH detector with two different window materials. sring has been calculated as sph y y /ONrp, then it does not include any background contribution.
chromatic
rh (mrad) remission (mrad) h rpixel (mrad) h rph h (mrad) Nrp
rring (mrad) h
CaF2
SiO2
1.26 0.5 2.0 2.3 10 0.8
0.6 0.5 2.0 2.0 7.2 0.8
100
80
90
75
80
70 70
Y
Fig. 1. Proposed VHMPID layout, with five super-modules next to the PHOS detector and the D-CAL electromagnetic calorimeter extension.
65
60
60
50 40
55
30
50 20
45
10
40
0
40
Fig. 2. Longitudinal (left) and transversal (right) cross-sections of the proposed VHMPID central module, showing the dimensions of main elements and the sharing among them the 1.3 m available height.
degraded by C4F10 [13]. High reflectivity up to VUV is achieved by Al/MgF2 coating [14]. The Front-End electronics is based on the GASSIPLEX chip [15] allowing multiplexed analogue readout for centroid measurement. Concerning integration inside the ALICE experiment, a ‘‘supermodule’’ layout with large radiator vessels has been recently adopted in order to exploit all the available space and maximize the acceptance (Fig. 1). With four ‘‘side’’ modules of 3.2 1.7 m2 and one ‘‘central’’ of 2.6 1.7 m2, a total acceptance of 12% of the ALICE central barrel can be achieved in the pseudorapidity range 9Z9 o0.5, corresponding to jets fully contained inside the ALICE TPC. Fig. 2 shows the cross-section of the central module with the organization of the different subsystems. According to the present layout, each super-module will be equipped with an array or mirrors of about 50 60 cm2, each focusing Cherenkov photons on a corresponding photon detector of 20 30 cm2 area. Mirror segmentation and orientation are under investigation to minimize the photosensitive area while keeping identification efficiency for close tracks [16].
3. Cherenkov angle resolution studies Given the limitation in radiator length, hence in the number of produced Cherenkov photons, the dependence of Cherenkov angle resolution and particle separation on window material has been
45
50
55
60 X
65
70
75
80
Fig. 3. Cherenkov ring produced by simulation of 16 GeV/c p in a detector with SiO2 window.
studied. Table 1 presents the main contributions to the angular resolution for CaF2 and SiO2 windows obtained by analytical treatment [17]. The number of reconstructed photoelectrons (Nrp) corresponds to the number of pad clusters and is smaller than the number of detected photoelectrons due to the relatively large pad size and small ring radius, resulting in a geometrical overlap inside the same pad clusters. Detector simulations have been used to estimate Nrp (reported in Table 1) and sph y for the two window materials (Figs. 3 and 4), using optical media transparencies and CsI quantum efficiency from Refs. [18,19,20,9]. In such a detector configuration the pixel error is dominant and the angular resolution at saturation is equivalent for the two window materials. Fig. 5 shows the sring needed for 3s separation between two y particles of masses m1 and m2, respectively, as a function of the momentum p, obtained using the well known relation.
sring ¼ y
m22 m21 2ns p2 tan W
where ns ¼3, and y is the Cherenkov angle. The estimated track resolution of 0.8 mrad would allow p/K and K/p 3s separation up to25 and 45 GeV/c, respectively. Nevertheless, smaller pad segmentation (e.g. 4 4 mm2) would improve the spatial resolution and consequently increase Nrp, with beneficial effects not only on upper but also on lower momentum limit, close to Cherenkov emission threshold. The choice of window material and pad
276
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
Fig. 5. sring for 3s separation between p/K and K/p as a function of the particle y momentum.
25 GeV/c, 80 cm C4F10 π K
120 100
p
<θ>π = 0.0546 rad σπ = 1.15 mrad
<θ>K = 0.0507 rad σK = 1.23 mrad
80 60 40
Fig. 4. Reconstructed Cherenkov angle distributions from MonteCarlo simulations, for CaF2 (a) and SiO2 (b) windows. The sph y values are in good agreement with theoretical calculations results, shown in Table 1.
20 0 0.03
segmentation will be finalized by means of beam tests of RICH prototypes.
0.035
0.04
0.045 0.05 0.055 angle (rad)
0.06
0.065
0.07
Fig. 6. Cherenkov angle ring resolution from events with p, K and p at 25 GeV/c embedded in HIJING background.
4. PID performance studies The analytical treatment of the angle resolution does not take into account the background, which can degrade the PID performance in the high-multiplicity environment of Pb+Pb collisions at LHC energies, where charged particles densities up to 80/m2 are expected. PID has been studied implementing in ALIROOT (the ALICE simulation framework) the VHMPID baseline detector (with CsI-MWPC and SiO2 window) and generating events by overlapping single particle Cherenkov rings to HIJING background [6,16]. The pattern recognition algorithm based on the Hough Transform method and implemented for the HMPID RICH [21] has been adapted for the proposed VHMPID focusing layout and used for event processing. Fig. 6 shows the reconstructed ring angle distributions for p, K and p at 25 GeV/c from the above described events, in which one can notice the increase in sring with respect to analytical estimation. Table 2 summarizes PID y
Table 2 Momentum ranges for PID: in case of presence of signal, the lower limit corresponds to Nrp 43, while the upper limit corresponds to 3s separation. Particle type
Absence of signal (GeV/c)
Presence of signal (GeV/c)
11–17
4–24 11–24 19–38
p K p
capabilities. Preliminary results of efficiency and contamination studies with simulations have confirmed the validity of the baseline layout [5].
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
277
5. High momentum trigger
Acknowledgments
The drop in charged hadron yield at high momentum requires a specific trigger to fully exploit the VHMPID and enrich the collected sample. In addition to the baseline solution represented by the ALICE TRD detector for L1 triggering [22], a dedicated High-pt Trigger Detector (HPTD) is under development [23]. It consists of two sets of tracking planes, upstream and downstream the RICH detector, respectively, providing
This work was supported by Hungarian OTKA and NKTH grants NK77816, CK 77719 and CK 77815. The support of National Research Foundation (NRF) of Korea is also acknowledged. G. Paic and D. Mayani acknowledge the support of the UNAM grant IN115808, the CERN-UNAM grant and the support of the Coordinacion de la Investigacion Cientifica. G. Baranfoldi thanks the Janos Bolyai Research Scholarship of the HAS, Hungary.
Fast L0 trigger (mostly relevant for the p +p environment) for p 42 GeV/c;
L1 trigger to select tracks in the high-pT range, with a tunable
cut-off in 8–15 GeV/c, for the high multiplicity Pb+ Pb environment; Tracking for accurate positioning of particles, used for Cherenkov angle reconstruction.
The detector under study is a Close-Cathode-Chamber, a classic MWPC with small anode-cathode gap ( o1 mm) and field wires interleaved with anode wires, achieving a narrow response function onto a strip segmented cathode. The dependence of trigger efficiency on number of layers and strip size is being investigated with simulations and beam tests.
6. Conclusions and outlook The proposed VHMPID upgrade project is in a full R&D phase aiming at the optimization of detector layout and PID performance. Two fundamental parameters, the photon detector spatial resolution (pad size) and window material will be studied further with simulations and beam tests. The R&D for the construction of a prototype module (the central module partially equipped to achieve a suitable acceptance) has been approved by the ALICE collaboration. Its installation has been proposed for the end of the long LHC shutdown in 2013.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
B. Alessandro, et al., J. Phys. G 32 (2006) 1295. S.S. Adler, et al., Phys. Rev. C 69 (2004) 034909. R.C. Hwa, C.B. Yang, Phys. Rev. Lett. 97 (2006) 042301. S. Sapeta, U. A. Wiedemann, arXiv:0707.3494 [hep-ph]. A. Agocs, et al., Nucl. Instr. and Meth. A 617 (2010) 424. G. Volpe, et al., Nucl. Instr. and Meth. A 595 (2008) 40. P. Levai, et al., J. Phys. G35 (2008) 104111. P. Martinengo, report, Nucl. Instr. and Meth., this issue. H. Hoedlmoser, et al., Nucl. Instr. and Meth. A 566 (2006) 338. K. Zeitelhack, et al., Nucl. Instr. and Meth. A 433 (1999) 201. G. Baum, et al., Nucl. Instr. and Meth. A 433 (1999) 207. V. Peskov, report, Nucl. Instr. and Meth., this issue. G.J. Barber, et al., Nucl. Instr. and Meth. A 593 (2008) 624. P. Baillon, et al., Nucl. Instr. and Meth. A 277 (1989) 338. J.C. Santiard, Nucl. Instr. and Meth. A 518 (2004) 498. G. Volpe, report, Nucl. Instr. and Meth, this issue. T. Ypsilantis, J. Seguinot, Nucl. Instr. and Meth. A 343 (1994) 30. D. Wiedner, et al., Nucl. Instr. and Meth. A 595 (2008) 216. E. Albrecht, et al., Nucl. Instr. and Meth. A 502 (2003) 266. C. Joram, Nucl. Instr. and Meth. A 343 (1994) 246. D. Di Bari, Nucl. Instr. and Meth. A 502 (2003) 300. ALICE TRD Technical Design Report, CERN-LHCC 2001-021. L. Boldiszar, et al., Nucl. Phys. B (Proc. Suppl.) 197 (2009) 296.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
The VHMPID RICH upgrade project for ALICE at LHC A. Di Mauro a,n, A. Agocs b, R. Alfaro c, G.G. Barnafoldi b, G. Bencze b, L. Boldizsar b, E. Cuautle d, G. DeCataldo e, E. Denes b, D. DiBari e, I. Dominguez d, Z. Fodor b, E. Futo b, E. Garcia f, G. Hamar b, J.W. Harris g, P. Levai b, C. Lipusz b, P. Martinengo a, D. Mayani d, L. Molnar a, E. Nappi e, A. Ortiz d, G. Paic d, C. Pastore e, D. Perini a, V. Peskov a,d, F. Piuz a, S. Pochybova b, I. Sgura e, N. Smirnov g, C. Son h, J.B. Van Beelen a, D. Varga i, G. Volpe e, J. Yi h, I.K. Yoo h a
CERN, Geneva, Switzerland MTA KFKI RMKI, Budapest, Hungary Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Mexico, Mexico d Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico, Mexico e Universita degli Studi di Bari, Dipartimento Interateneo di Fisica ‘‘M.Merlin’’ & INFN Sezione di Bari, Bari, Italy f Chicago StateUniversity, Chicago, USA g YaleUniversity, New Haven, USA h Pusan National University, Pusan, Republic of Korea i Eotvos University, Budapest, Hungary b c
a r t i c l e i n f o
a b s t r a c t
Available online 8 November 2010
RHIC results have shown the importance of high momentum particles as hard probes and the need for particle identification (PID) in a very large momentum range. A Very High Momentum PID (VHMPID) detector has been proposed as upgrade of ALICE to extend the track-by-track identification capabilities for charged hadrons from the present 5 GeV/c limit to the momentum range 10–30 GeV/c. The VHMPID detector is a focusing RICH using C4F10 gaseous radiator coupled to a CsI-based photon detector. Detector design studies, achievable Cherenkov angle resolution, expected performance and high momentum triggering will be discussed. & 2010 Elsevier B.V. All rights reserved.
Keywords: RICH Gaseous detectors Photon detection CsI photoconverter ALICE
1. Introduction A Large Ion Collider Experiment (ALICE) has been designed to study quark-gluon plasma in heavy ion collisions at the LHC, but also p+p collision studies are relevant part of the physics program. The ALICE detector has a unique capability to identify a wide variety of particles [1]; however its momentum coverage for track-by-track identification should be extended to meet new physics challenges at LHC. Indeed, the anomalous baryon/meson ratio observed at RHIC in the momentum range 2–8 GeV/c [2] is expected to extend even higher in pt at LHC energies [3,4]. A Very High Momentum PID (VHMPID) RICH detector has been proposed as ALICE upgrade to perform charged hadrons track-by-track identification in the range 10–30 GeV/c and specifically address physics with ‘‘jets’’ [5]. The present paper will review the status of studies carried out on detector layout, expected performance and dedicated trigger system.
2. Detector layout and design issues The momentum range of interest for PID has driven the choice towards a focusing RICH detector with C4F10 gaseous radiator [6]. n
Corresponding author. E-mail address: [email protected] (A. Di Mauro).
0168-9002/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2010.10.103
The small available space inside the ALICE detector results in limitations of radiator length and geometrical acceptance. This last parameter, combined with the expected low charged particle yield at high momentum [7], makes necessary the implementation of a high-pt trigger to maximize the event rate. One trigger option, as discussed later, consists in a new dedicated detector to be integrated in the same volume available for the full VHMPID system, thus resulting in further limitations on the radiator length. The expected large photosensitive area of about 3 m2 and the operation inside the magnetic field of 0.5 T of the ALICE solenoid suggests to exploit the experience gained with CsI-based gaseous photon detectors for the ALICE HMPID RICH [8,9] and for other similar RICH counters (HADES [10], COMPASS [11]), more than exploring other solutions like vacuum or solid state devices which are significantly less cost-effective or not suitable for this application. The principle scheme of the proposed VHMPID RICH detector has been presented in other publications [5,6]. The Cherenkov photons produced in a C4F10 gaseous radiator (L¼80 cm) are focused by a spherical mirror through a SiO2 (or CaF2) window onto an HMPID-like photon detector, a MWPC coupled to CsI photocathode segmented into 8 8.4 mm2 pads. As alternative option, a thick-GEM based photon detector with reflective CsI photo-converter is under study [12]. The mirror has a lightweight carbon-fiber substrate, a material which minimizes the material for traversing particles and is fluorocarbon-compatible, thus not
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
275
Table 1 Contributions to the resolution (from chromatic, emission point and pixel errors), the total resolution per photoelectron, the mean number of reconstructed photoelectrons for particles at saturation (from MonteCarlo simulation) and the resolution per track, for the proposed RICH detector with two different window materials. sring has been calculated as sph y y /ONrp, then it does not include any background contribution.
chromatic
rh (mrad) remission (mrad) h rpixel (mrad) h rph h (mrad) Nrp
rring (mrad) h
CaF2
SiO2
1.26 0.5 2.0 2.3 10 0.8
0.6 0.5 2.0 2.0 7.2 0.8
100
80
90
75
80
70 70
Y
Fig. 1. Proposed VHMPID layout, with five super-modules next to the PHOS detector and the D-CAL electromagnetic calorimeter extension.
65
60
60
50 40
55
30
50 20
45
10
40
0
40
Fig. 2. Longitudinal (left) and transversal (right) cross-sections of the proposed VHMPID central module, showing the dimensions of main elements and the sharing among them the 1.3 m available height.
degraded by C4F10 [13]. High reflectivity up to VUV is achieved by Al/MgF2 coating [14]. The Front-End electronics is based on the GASSIPLEX chip [15] allowing multiplexed analogue readout for centroid measurement. Concerning integration inside the ALICE experiment, a ‘‘supermodule’’ layout with large radiator vessels has been recently adopted in order to exploit all the available space and maximize the acceptance (Fig. 1). With four ‘‘side’’ modules of 3.2 1.7 m2 and one ‘‘central’’ of 2.6 1.7 m2, a total acceptance of 12% of the ALICE central barrel can be achieved in the pseudorapidity range 9Z9 o0.5, corresponding to jets fully contained inside the ALICE TPC. Fig. 2 shows the cross-section of the central module with the organization of the different subsystems. According to the present layout, each super-module will be equipped with an array or mirrors of about 50 60 cm2, each focusing Cherenkov photons on a corresponding photon detector of 20 30 cm2 area. Mirror segmentation and orientation are under investigation to minimize the photosensitive area while keeping identification efficiency for close tracks [16].
3. Cherenkov angle resolution studies Given the limitation in radiator length, hence in the number of produced Cherenkov photons, the dependence of Cherenkov angle resolution and particle separation on window material has been
45
50
55
60 X
65
70
75
80
Fig. 3. Cherenkov ring produced by simulation of 16 GeV/c p in a detector with SiO2 window.
studied. Table 1 presents the main contributions to the angular resolution for CaF2 and SiO2 windows obtained by analytical treatment [17]. The number of reconstructed photoelectrons (Nrp) corresponds to the number of pad clusters and is smaller than the number of detected photoelectrons due to the relatively large pad size and small ring radius, resulting in a geometrical overlap inside the same pad clusters. Detector simulations have been used to estimate Nrp (reported in Table 1) and sph y for the two window materials (Figs. 3 and 4), using optical media transparencies and CsI quantum efficiency from Refs. [18,19,20,9]. In such a detector configuration the pixel error is dominant and the angular resolution at saturation is equivalent for the two window materials. Fig. 5 shows the sring needed for 3s separation between two y particles of masses m1 and m2, respectively, as a function of the momentum p, obtained using the well known relation.
sring ¼ y
m22 m21 2ns p2 tan W
where ns ¼3, and y is the Cherenkov angle. The estimated track resolution of 0.8 mrad would allow p/K and K/p 3s separation up to25 and 45 GeV/c, respectively. Nevertheless, smaller pad segmentation (e.g. 4 4 mm2) would improve the spatial resolution and consequently increase Nrp, with beneficial effects not only on upper but also on lower momentum limit, close to Cherenkov emission threshold. The choice of window material and pad
276
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
Fig. 5. sring for 3s separation between p/K and K/p as a function of the particle y momentum.
25 GeV/c, 80 cm C4F10 π K
120 100
p
<θ>π = 0.0546 rad σπ = 1.15 mrad
<θ>K = 0.0507 rad σK = 1.23 mrad
80 60 40
Fig. 4. Reconstructed Cherenkov angle distributions from MonteCarlo simulations, for CaF2 (a) and SiO2 (b) windows. The sph y values are in good agreement with theoretical calculations results, shown in Table 1.
20 0 0.03
segmentation will be finalized by means of beam tests of RICH prototypes.
0.035
0.04
0.045 0.05 0.055 angle (rad)
0.06
0.065
0.07
Fig. 6. Cherenkov angle ring resolution from events with p, K and p at 25 GeV/c embedded in HIJING background.
4. PID performance studies The analytical treatment of the angle resolution does not take into account the background, which can degrade the PID performance in the high-multiplicity environment of Pb+Pb collisions at LHC energies, where charged particles densities up to 80/m2 are expected. PID has been studied implementing in ALIROOT (the ALICE simulation framework) the VHMPID baseline detector (with CsI-MWPC and SiO2 window) and generating events by overlapping single particle Cherenkov rings to HIJING background [6,16]. The pattern recognition algorithm based on the Hough Transform method and implemented for the HMPID RICH [21] has been adapted for the proposed VHMPID focusing layout and used for event processing. Fig. 6 shows the reconstructed ring angle distributions for p, K and p at 25 GeV/c from the above described events, in which one can notice the increase in sring with respect to analytical estimation. Table 2 summarizes PID y
Table 2 Momentum ranges for PID: in case of presence of signal, the lower limit corresponds to Nrp 43, while the upper limit corresponds to 3s separation. Particle type
Absence of signal (GeV/c)
Presence of signal (GeV/c)
11–17
4–24 11–24 19–38
p K p
capabilities. Preliminary results of efficiency and contamination studies with simulations have confirmed the validity of the baseline layout [5].
A. Di Mauro et al. / Nuclear Instruments and Methods in Physics Research A 639 (2011) 274–277
277
5. High momentum trigger
Acknowledgments
The drop in charged hadron yield at high momentum requires a specific trigger to fully exploit the VHMPID and enrich the collected sample. In addition to the baseline solution represented by the ALICE TRD detector for L1 triggering [22], a dedicated High-pt Trigger Detector (HPTD) is under development [23]. It consists of two sets of tracking planes, upstream and downstream the RICH detector, respectively, providing
This work was supported by Hungarian OTKA and NKTH grants NK77816, CK 77719 and CK 77815. The support of National Research Foundation (NRF) of Korea is also acknowledged. G. Paic and D. Mayani acknowledge the support of the UNAM grant IN115808, the CERN-UNAM grant and the support of the Coordinacion de la Investigacion Cientifica. G. Baranfoldi thanks the Janos Bolyai Research Scholarship of the HAS, Hungary.
Fast L0 trigger (mostly relevant for the p +p environment) for p 42 GeV/c;
L1 trigger to select tracks in the high-pT range, with a tunable
cut-off in 8–15 GeV/c, for the high multiplicity Pb+ Pb environment; Tracking for accurate positioning of particles, used for Cherenkov angle reconstruction.
The detector under study is a Close-Cathode-Chamber, a classic MWPC with small anode-cathode gap ( o1 mm) and field wires interleaved with anode wires, achieving a narrow response function onto a strip segmented cathode. The dependence of trigger efficiency on number of layers and strip size is being investigated with simulations and beam tests.
6. Conclusions and outlook The proposed VHMPID upgrade project is in a full R&D phase aiming at the optimization of detector layout and PID performance. Two fundamental parameters, the photon detector spatial resolution (pad size) and window material will be studied further with simulations and beam tests. The R&D for the construction of a prototype module (the central module partially equipped to achieve a suitable acceptance) has been approved by the ALICE collaboration. Its installation has been proposed for the end of the long LHC shutdown in 2013.
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
B. Alessandro, et al., J. Phys. G 32 (2006) 1295. S.S. Adler, et al., Phys. Rev. C 69 (2004) 034909. R.C. Hwa, C.B. Yang, Phys. Rev. Lett. 97 (2006) 042301. S. Sapeta, U. A. Wiedemann, arXiv:0707.3494 [hep-ph]. A. Agocs, et al., Nucl. Instr. and Meth. A 617 (2010) 424. G. Volpe, et al., Nucl. Instr. and Meth. A 595 (2008) 40. P. Levai, et al., J. Phys. G35 (2008) 104111. P. Martinengo, report, Nucl. Instr. and Meth., this issue. H. Hoedlmoser, et al., Nucl. Instr. and Meth. A 566 (2006) 338. K. Zeitelhack, et al., Nucl. Instr. and Meth. A 433 (1999) 201. G. Baum, et al., Nucl. Instr. and Meth. A 433 (1999) 207. V. Peskov, report, Nucl. Instr. and Meth., this issue. G.J. Barber, et al., Nucl. Instr. and Meth. A 593 (2008) 624. P. Baillon, et al., Nucl. Instr. and Meth. A 277 (1989) 338. J.C. Santiard, Nucl. Instr. and Meth. A 518 (2004) 498. G. Volpe, report, Nucl. Instr. and Meth, this issue. T. Ypsilantis, J. Seguinot, Nucl. Instr. and Meth. A 343 (1994) 30. D. Wiedner, et al., Nucl. Instr. and Meth. A 595 (2008) 216. E. Albrecht, et al., Nucl. Instr. and Meth. A 502 (2003) 266. C. Joram, Nucl. Instr. and Meth. A 343 (1994) 246. D. Di Bari, Nucl. Instr. and Meth. A 502 (2003) 300. ALICE TRD Technical Design Report, CERN-LHCC 2001-021. L. Boldiszar, et al., Nucl. Phys. B (Proc. Suppl.) 197 (2009) 296.