- Email: [email protected]
Test beam results of CMS quartz fibre calorimeter prototype and simulation of response to high energy hadron jets
Nuclear Instruments and Methods in Physics Research A 409 (1998) 593—597
Test beam results of CMS quartz fibre calorimeter prototype and simulation of response to high energy hadron jets N. Akchurin!, S. Ayan", Gy.L. Bencze#, K. Chikin$, H. Cohn%, S. Doulas&,1, I. Dumanog\ lu', E. Eskut&, A. Fenyvesi), A. Ferrando*, M.C. Fouz*, V. Gavrilov+, Y. Gershtein+, C. Hajdu#, J. Iosifidis,, M.I. Josa*, A. Khan*, S.B. Kim&, V. Kolosov+,*, S. Kuleshov+, J. Langland!, D. Litvinsev+, J.-P. Merlo&,2, J. Molnar), A. Nikitin+, Y. Onel!, G. O®nengu¨t', D. Osborne&, N. O®zdes7 -Kosa', A. Penzo-, E. Pesen", V. Podrasky,, A. Rosowsky&,3, J.M. Salicio*, V. Stolin+, L. Sulak&, J. Sullivan&, A. Ulyanov+, A. Umashev+, S. Uzunian+, G. Vesztergombi#, D. Winn,, R. Winsor!, P. Zalan#, M. Zeyrek" ! University of Iowa, Iowa City, USA " Middle East Technical University, Ankara, Turkey # KFKI-RMKI, Budapest, Hungary $ NPI Moscow State University, Moscow, Russia % Oak Ridge National Laboratory, Oak Ridge, USA & Boston Univesity, Boston, USA ' C7 ucurova University, Adana, Turkey ) ATOMKI, Debrecen, Hungary * CIEMAT, Madrid, Spain + ITEP, Moscow, Russia , Fairfield University, Fairfield, USA - Universita% de Trieste and INFN, Sez. Trieste, Trieste, Italy
Abstract CMS very forward calorimeter is based on a quartz fibre technology. The calorimeter prototype composed of two longitudinal segments was tested at CERN in 1996. We present the test beam data analysis of this prototype. It was shown that the mean values of responses for pions and electrons of the same energy could be equalised using the appropriate ratio of calibration constants for longitudinal segments. The beam test data were used to simulate the calorimeter response to hadron jets. ( 1998 Elsevier Science B.V. All rights reserved.
1. Introduction * Corresponding author. Tel.: #7 095 125 9112; fax: #7 095 123 6584; e-mail: [email protected]. 1 Now at Northeastern University, Boston, USA. 2 Now at University of Iowa, Iowa, USA. 3 Now at CEN Saclay, Gif-sur-Yvette, France.
The Very Forward Calorimeters (VFCAL) in CMS [1,2] will cover the pseudorapidity range 34DgD45. The main goals of VFCAL are to
0168-9002/98/$19.00 ( 1998 Elsevier Science B.V. All rights reserved PII S 0 1 6 8 - 9 0 0 2 ( 9 7 ) 0 1 3 2 8 - 4
VII. TRENDS IN CALORIMETRY
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N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
provide hermetic calorimetry measurements of the transverse energy (E ), and to identify jets. 5 The measurement of E is important in the study 5 of top quark production, as well as for Standard Model Higgs searches in channels involving neutrinos. It is crucial for SUSY particle searches. The calorimeter design with longitudinal segmentation allows to provide the redundancy of the energy flow measurements, to identify the events with anomalous deposition of electromagnetic energy and to improve the energy resolution of jets. The VFCAL will operate in extremely hostile radiation environment since it will catch the most part of the energy of secondary particles produced in pp collisions at LHC. Namely in the high luminosity regime of the collider, corresponding to L"1034 cm~2 s~1 more than 1000 particles of total energy of about 8 TeV will hit each of two VFCALs every 25 ns. The expected radiation levels and the neutron fluxes in the VFCAL region will be unprecidently high reaching MGy/yr and 109 n cm~2 s~1, respectively. This calls for two major requirements to the calorimeter performance, very fast signal to avoid a pile-up from several bunch crossings, and high radiation resistance. A low sensitivity to neutrons and radioactive decays is also desirable. The VFCAL based on quartz fibre technology [3—5] is proposed for CMS detector. The signal in this type of calorimeters is generated by Cherenkov light radiated by relativistic charged particles crossing optical quartz fibres embedded into the the copper absorber matrix. The fast response and low sensitivity to neutrons and radioactive decays are provided by the intrinsic features of Cherenkov radiation, instantaneous light emission and velocity threshold. The radiation resistance is achieved by using radiation hard types of optical quartz fibres [6]. The first results of beam tests of the hadronic prototype of the CMS quartz fibre calorimeter, concerning a single module without longitudinal segmentation, were published in Ref. [7]. It was shown that the response of the quartz fibre calorimeter is very fast and the calorimeter has adequate energy resolution for the CMS very forward region. It was also shown that there is a large difference between signals from pions and electrons of the
same energy. Such a difference was predicted by Monte-Carlo simulations of calorimeter response and is the consequence of the non-compensating nature of the calorimeters based on Cherenkov light.
2. Experimental set-up and test beam The results presented in this paper are based on the data collected in July—August 1996 at CERN SPS test beam with the detector set-up composed by two longitudinal modules, extended with respect to the one tested during the same run period (see Ref. [7]). The calorimeter prototype consisted of two independent modules. Each module was essentially a copper block with fibres embedded in it in such a way that every fibre was equidistant to its six nearest neighbours with the spacing 2.3 mm. The resulting filling fraction in volume was 1.5%. The dimensions of the first, with respect to the incoming particle direction, module were 16]16]34 cm3 while the second module (HAD module) was 16]16]135 cm3. The equivalent lengths for EM and HAD modules are 24X (2j ) and 8.5 j respec0 I I tively. Thus the total length is equivalent to about 10.5j . The instrumented volume is sufficient for I 93% lateral and full longitudinal hadron shower containment [7]. The fibres are arranged to form 9 readout towers having 53]54 mm2 transverse dimensions. The Cherenkov light originated in the fibres of each tower is detected in the photomultiplier (PM) and further digitised. PMs of the EM section are mounted in front of the module to avoid gap which would appear between EM and HAD parts in order to accommodate bundles. Cherenkov light, mostly going in forward direction along the fibre, is collected in EM section by means of reflection at the mirrored ends of the fibres. The whole set-up was mounted on the platform in the H4 beam line of the CERN SPS. The angles between the beam and the fibres both in horizontal and vertical planes were kept at 0° throughout the experiment. The details about the beam line equipment, rates, the trigger conditions, and the readout system can be found in Ref. [7].
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
595
3. Data analysis and results for single particles The data sample used for the analyses presented here consists of the datasets taken at various energies of an electron beam or a negative pion beam, namely (A) The electron data taken at 10, 12, 15, 20, 35, 80, 100, 150, 200 GeV. (B) The negative pion data taken at 12, 15, 20, 35, 80, 100, 200, 300, 350 GeV. (C) The calibration data taken with the electrons of 80 GeV hitting consequently the centres of individual cells both for the electromagnetic and the hadronic modules. In datasets (A) and (B) the beam of incoming particles has been steered in the centre of the innermost tower. Using the calibration data the responses of all cells to 80 GeV electrons were equalised. Then the calibration factors for every cells were derived constraining the total response deposited in all cells of each of the modules to the electron beam energy. These factors defined the electromagnetic scale for the prototype signal. The response of a calorimeter was calculated as a sum of signals from all 18 cells (3]3 towers). The electron showers were practically completely contained in the EM section, but in the case of pion the signal was shared between the EM and HAD sections. The energy resolution for electron can be approximated as p /E"1.5/JE=0.06 while the RMS resolution for pions was p /E"2.7/JE=0.13. RMS These results are in an agreement with the results for longitudinally non-segmented prototype (single HAD section) of quartz fibre calorimeter [7]. For single HAD module the energy resolution was p /E"1.4/JE while the constant RMS term was less than 0.02 for electrons and p /E" RMS 2.7/JE=0.13 for pions. The observed difference in constant terms of electron resolution functions is caused by spatial non-uniformity induced by variation of the reflection efficiency of the mirrors. Fig. 1 shows the dependence of the mean calibrated response against the beam energy. The error bars in this figure correspond to RMS of the response distribution. Fig. 1 demonstrates that the calibration using the electromagnetic scale would
Fig. 1. Signal in the prototype vs. energy.
lead to the underestimation of the hadronic energy deposited in the VFCAL. The energy of jet detected in the VFCAL is the sum of energies deposited by hadrons, mostly charged pions, and energies deposited by photons, from p0 decays. The average fraction of the electromagnetic component in the tagging jets is expected to be about 1/4, but the value of this fraction fluctuates highly from jet to jet. The simplest way to achieve unbiased measurement of jet energy is the rescaling of responses from both EM and HAD segments primarily calibrated in the EM scale. However it is possible to approximately equalise the calibrated response to charged pions and to electrons by increasing mean response to pions using higher calibration constant C for second 2 longitudinal segment of calorimeter (Eq. (1)). A"C A #C A . 1 EM 2 HAD
(1)
For the studied longitudinal segmentation such equalisation is achieved for C /C +2. However 2 1 due to induced longitudinal non-uniformity of calorimeter the energy resolution for single pions becomes worse (p /E"2.9/JE=0.20) with respect RMS to the case of C /C "1. It is shown in Fig. 2 in 2 1 VII. TRENDS IN CALORIMETRY
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N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
Fig. 2. Energy resolution for pions vs. energy.
comparison with the energy resolution for the ratio of calibration constants C /C "1). 2 1 4. Jet response simulation The data from beam test were used for the simulation of the quartz fibre calorimeter response to high energy hadron jets. So called tagging jets were simulated for the analysis. These type of very high energy jets (SE T+1 TeV) will be produced +%5 at the LHC in the reaction qqP(WW, ZZPH)jj in the pseudorapidity range 24DgD45. The jets were generated by means of the PYTHIA package. The energy of the jets ranges from 400 GeV to 2 TeV. Each jet was considered as a mixture of hadrons (mainly pB) and gammas contained in a g—/ cone of the radius 0.5 around the direction of the initial quark which has given rise to this jet. The data for pions were used for simulation of the response to all types of hadrons and data for electrons were used for simulation of the response to gammas. The jet response was calculated as a sum of responses of all jet particles. It is possible to improve the resolution for jet measurements changing the ratio of the calibration constants for EM and HAD modules. Fig. 3 shows the calibrated response distributions for three different ratios of calibration constants C /C (the absolute values of 2 1 constants were chosen to have the mean response to be equal to 1 TeV for 1 TeV jets). The best
Fig. 3. Signal distributions for 1 TeV jets.
energy resolution for jets was achieved for C /C "1.45. 2 1 Fig. 4 shows the results of simulation of jet energy resolution as a function of jet energy. Three sets of points correspond to three different values of C /C . This figure allows to draw a conclusion that 2 1 the ratio of C /C "1.45 is the optimal one in the 2 1 wide range of jet energies. Fit to the standard expression p /E "a/JE =b yielded the followRMS +%5 +%5 ing parameters: p 3.0 RMS" =0.09 for C /C "1, 2 1 E JE +%5 +%5
(2)
p 3.0 RMS" =0.06 for C /C "1.45, 2 1 E E +%5 +%5
(3)
p 3.2 RMS" =0.08 for C /C "1.97. 2 1 E JE +%5 +%5
(4)
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
597
g—/ cone used for jet energy measurements. It is expected that for high luminosity operation of LHC these two terms will be approximately of the same value as the intrinsic jet energy resolution of quartz fibre calorimeter.
Acknowledgements
Fig. 4. Energy resolution for 1 TeV jets.
The small non-linearity of response is observed for this set of calibration constants but it is less than the energy resolution.
5. Summary and conclusions The data from beam test of the prototype of longitudinal-segmented quartz fibre calorimeter were used to simulate the expected response of such type of calorimeters to high energy jets. It was shown that the optimal jet energy resolution can be achieved for the appropriate calibration of signals from different longitudinal segments. As a result the jet energy resolution of p /E "3.0/JE =0.06 RMS +%5 +%5 can be achieved. The response will be linear with respect to the jet energy with the accuracy better than the energy resolution. It should be noted that the quoted resolution corresponds only to the intrinsic resolution of the calorimeter. In the real experiment there will be at least two other terms, namely the pile-up noise fluctuation and the fluctuations of the fraction of jet energy flowing out the
We would like to thank our colleagues from CMS, and in particular J.Bourotte and M. Haguenauer, who made the described beam tests possible. We are grateful to N.Doble, who provided us with particle beams of excellent quality. This project was carried out with financial support from CERN, the US Department of Energy, RMKIKFKI (Hungary, OTKA grant T 016823), the Scientific and Technical Research Council of Turkey (TU®BITAK), CICYT (Spain, grant AEN96-2051E), the International Science Foundation (grants M82000 and M82300), the State Committee of the Russian Federation for Science and Technologies, and the Russian Research Foundation (grant 9502-04815).
References [1] The CMS Collaboration, Technical Proposal, CERN/LHCC 94-39, (1994). [2] The CMS Collaboration, Technical Design Report, CERN/LHCC 97-31, (1997). [3] A. Contin et al., R&D Proposal for development of quartz fibre calorimetry, CERN DRDC/94-4 (1994) [4] G. Anzivino et al., Nucl. Instr. and Meth. A 357 (1995) 380. [5] P. Gorodetzky et al., Nucl. Instr. and Meth. A 361 (1995) 1. [6] V. Gavrilov et al., Study of Quartz Fiber Radiation Hardness, CMS TN-94-324. [7] N. Akchurin et al., Beam test results from a fine-sampling quartz fiber calorimeter for electron, photon and hadron detection, Nucl. Instr. and Meth. A 399 (1997) 202.
VII. TRENDS IN CALORIMETRY
Test beam results of CMS quartz fibre calorimeter prototype and simulation of response to high energy hadron jets N. Akchurin!, S. Ayan", Gy.L. Bencze#, K. Chikin$, H. Cohn%, S. Doulas&,1, I. Dumanog\ lu', E. Eskut&, A. Fenyvesi), A. Ferrando*, M.C. Fouz*, V. Gavrilov+, Y. Gershtein+, C. Hajdu#, J. Iosifidis,, M.I. Josa*, A. Khan*, S.B. Kim&, V. Kolosov+,*, S. Kuleshov+, J. Langland!, D. Litvinsev+, J.-P. Merlo&,2, J. Molnar), A. Nikitin+, Y. Onel!, G. O®nengu¨t', D. Osborne&, N. O®zdes7 -Kosa', A. Penzo-, E. Pesen", V. Podrasky,, A. Rosowsky&,3, J.M. Salicio*, V. Stolin+, L. Sulak&, J. Sullivan&, A. Ulyanov+, A. Umashev+, S. Uzunian+, G. Vesztergombi#, D. Winn,, R. Winsor!, P. Zalan#, M. Zeyrek" ! University of Iowa, Iowa City, USA " Middle East Technical University, Ankara, Turkey # KFKI-RMKI, Budapest, Hungary $ NPI Moscow State University, Moscow, Russia % Oak Ridge National Laboratory, Oak Ridge, USA & Boston Univesity, Boston, USA ' C7 ucurova University, Adana, Turkey ) ATOMKI, Debrecen, Hungary * CIEMAT, Madrid, Spain + ITEP, Moscow, Russia , Fairfield University, Fairfield, USA - Universita% de Trieste and INFN, Sez. Trieste, Trieste, Italy
Abstract CMS very forward calorimeter is based on a quartz fibre technology. The calorimeter prototype composed of two longitudinal segments was tested at CERN in 1996. We present the test beam data analysis of this prototype. It was shown that the mean values of responses for pions and electrons of the same energy could be equalised using the appropriate ratio of calibration constants for longitudinal segments. The beam test data were used to simulate the calorimeter response to hadron jets. ( 1998 Elsevier Science B.V. All rights reserved.
1. Introduction * Corresponding author. Tel.: #7 095 125 9112; fax: #7 095 123 6584; e-mail: [email protected]. 1 Now at Northeastern University, Boston, USA. 2 Now at University of Iowa, Iowa, USA. 3 Now at CEN Saclay, Gif-sur-Yvette, France.
The Very Forward Calorimeters (VFCAL) in CMS [1,2] will cover the pseudorapidity range 34DgD45. The main goals of VFCAL are to
0168-9002/98/$19.00 ( 1998 Elsevier Science B.V. All rights reserved PII S 0 1 6 8 - 9 0 0 2 ( 9 7 ) 0 1 3 2 8 - 4
VII. TRENDS IN CALORIMETRY
594
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
provide hermetic calorimetry measurements of the transverse energy (E ), and to identify jets. 5 The measurement of E is important in the study 5 of top quark production, as well as for Standard Model Higgs searches in channels involving neutrinos. It is crucial for SUSY particle searches. The calorimeter design with longitudinal segmentation allows to provide the redundancy of the energy flow measurements, to identify the events with anomalous deposition of electromagnetic energy and to improve the energy resolution of jets. The VFCAL will operate in extremely hostile radiation environment since it will catch the most part of the energy of secondary particles produced in pp collisions at LHC. Namely in the high luminosity regime of the collider, corresponding to L"1034 cm~2 s~1 more than 1000 particles of total energy of about 8 TeV will hit each of two VFCALs every 25 ns. The expected radiation levels and the neutron fluxes in the VFCAL region will be unprecidently high reaching MGy/yr and 109 n cm~2 s~1, respectively. This calls for two major requirements to the calorimeter performance, very fast signal to avoid a pile-up from several bunch crossings, and high radiation resistance. A low sensitivity to neutrons and radioactive decays is also desirable. The VFCAL based on quartz fibre technology [3—5] is proposed for CMS detector. The signal in this type of calorimeters is generated by Cherenkov light radiated by relativistic charged particles crossing optical quartz fibres embedded into the the copper absorber matrix. The fast response and low sensitivity to neutrons and radioactive decays are provided by the intrinsic features of Cherenkov radiation, instantaneous light emission and velocity threshold. The radiation resistance is achieved by using radiation hard types of optical quartz fibres [6]. The first results of beam tests of the hadronic prototype of the CMS quartz fibre calorimeter, concerning a single module without longitudinal segmentation, were published in Ref. [7]. It was shown that the response of the quartz fibre calorimeter is very fast and the calorimeter has adequate energy resolution for the CMS very forward region. It was also shown that there is a large difference between signals from pions and electrons of the
same energy. Such a difference was predicted by Monte-Carlo simulations of calorimeter response and is the consequence of the non-compensating nature of the calorimeters based on Cherenkov light.
2. Experimental set-up and test beam The results presented in this paper are based on the data collected in July—August 1996 at CERN SPS test beam with the detector set-up composed by two longitudinal modules, extended with respect to the one tested during the same run period (see Ref. [7]). The calorimeter prototype consisted of two independent modules. Each module was essentially a copper block with fibres embedded in it in such a way that every fibre was equidistant to its six nearest neighbours with the spacing 2.3 mm. The resulting filling fraction in volume was 1.5%. The dimensions of the first, with respect to the incoming particle direction, module were 16]16]34 cm3 while the second module (HAD module) was 16]16]135 cm3. The equivalent lengths for EM and HAD modules are 24X (2j ) and 8.5 j respec0 I I tively. Thus the total length is equivalent to about 10.5j . The instrumented volume is sufficient for I 93% lateral and full longitudinal hadron shower containment [7]. The fibres are arranged to form 9 readout towers having 53]54 mm2 transverse dimensions. The Cherenkov light originated in the fibres of each tower is detected in the photomultiplier (PM) and further digitised. PMs of the EM section are mounted in front of the module to avoid gap which would appear between EM and HAD parts in order to accommodate bundles. Cherenkov light, mostly going in forward direction along the fibre, is collected in EM section by means of reflection at the mirrored ends of the fibres. The whole set-up was mounted on the platform in the H4 beam line of the CERN SPS. The angles between the beam and the fibres both in horizontal and vertical planes were kept at 0° throughout the experiment. The details about the beam line equipment, rates, the trigger conditions, and the readout system can be found in Ref. [7].
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
595
3. Data analysis and results for single particles The data sample used for the analyses presented here consists of the datasets taken at various energies of an electron beam or a negative pion beam, namely (A) The electron data taken at 10, 12, 15, 20, 35, 80, 100, 150, 200 GeV. (B) The negative pion data taken at 12, 15, 20, 35, 80, 100, 200, 300, 350 GeV. (C) The calibration data taken with the electrons of 80 GeV hitting consequently the centres of individual cells both for the electromagnetic and the hadronic modules. In datasets (A) and (B) the beam of incoming particles has been steered in the centre of the innermost tower. Using the calibration data the responses of all cells to 80 GeV electrons were equalised. Then the calibration factors for every cells were derived constraining the total response deposited in all cells of each of the modules to the electron beam energy. These factors defined the electromagnetic scale for the prototype signal. The response of a calorimeter was calculated as a sum of signals from all 18 cells (3]3 towers). The electron showers were practically completely contained in the EM section, but in the case of pion the signal was shared between the EM and HAD sections. The energy resolution for electron can be approximated as p /E"1.5/JE=0.06 while the RMS resolution for pions was p /E"2.7/JE=0.13. RMS These results are in an agreement with the results for longitudinally non-segmented prototype (single HAD section) of quartz fibre calorimeter [7]. For single HAD module the energy resolution was p /E"1.4/JE while the constant RMS term was less than 0.02 for electrons and p /E" RMS 2.7/JE=0.13 for pions. The observed difference in constant terms of electron resolution functions is caused by spatial non-uniformity induced by variation of the reflection efficiency of the mirrors. Fig. 1 shows the dependence of the mean calibrated response against the beam energy. The error bars in this figure correspond to RMS of the response distribution. Fig. 1 demonstrates that the calibration using the electromagnetic scale would
Fig. 1. Signal in the prototype vs. energy.
lead to the underestimation of the hadronic energy deposited in the VFCAL. The energy of jet detected in the VFCAL is the sum of energies deposited by hadrons, mostly charged pions, and energies deposited by photons, from p0 decays. The average fraction of the electromagnetic component in the tagging jets is expected to be about 1/4, but the value of this fraction fluctuates highly from jet to jet. The simplest way to achieve unbiased measurement of jet energy is the rescaling of responses from both EM and HAD segments primarily calibrated in the EM scale. However it is possible to approximately equalise the calibrated response to charged pions and to electrons by increasing mean response to pions using higher calibration constant C for second 2 longitudinal segment of calorimeter (Eq. (1)). A"C A #C A . 1 EM 2 HAD
(1)
For the studied longitudinal segmentation such equalisation is achieved for C /C +2. However 2 1 due to induced longitudinal non-uniformity of calorimeter the energy resolution for single pions becomes worse (p /E"2.9/JE=0.20) with respect RMS to the case of C /C "1. It is shown in Fig. 2 in 2 1 VII. TRENDS IN CALORIMETRY
596
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
Fig. 2. Energy resolution for pions vs. energy.
comparison with the energy resolution for the ratio of calibration constants C /C "1). 2 1 4. Jet response simulation The data from beam test were used for the simulation of the quartz fibre calorimeter response to high energy hadron jets. So called tagging jets were simulated for the analysis. These type of very high energy jets (SE T+1 TeV) will be produced +%5 at the LHC in the reaction qqP(WW, ZZPH)jj in the pseudorapidity range 24DgD45. The jets were generated by means of the PYTHIA package. The energy of the jets ranges from 400 GeV to 2 TeV. Each jet was considered as a mixture of hadrons (mainly pB) and gammas contained in a g—/ cone of the radius 0.5 around the direction of the initial quark which has given rise to this jet. The data for pions were used for simulation of the response to all types of hadrons and data for electrons were used for simulation of the response to gammas. The jet response was calculated as a sum of responses of all jet particles. It is possible to improve the resolution for jet measurements changing the ratio of the calibration constants for EM and HAD modules. Fig. 3 shows the calibrated response distributions for three different ratios of calibration constants C /C (the absolute values of 2 1 constants were chosen to have the mean response to be equal to 1 TeV for 1 TeV jets). The best
Fig. 3. Signal distributions for 1 TeV jets.
energy resolution for jets was achieved for C /C "1.45. 2 1 Fig. 4 shows the results of simulation of jet energy resolution as a function of jet energy. Three sets of points correspond to three different values of C /C . This figure allows to draw a conclusion that 2 1 the ratio of C /C "1.45 is the optimal one in the 2 1 wide range of jet energies. Fit to the standard expression p /E "a/JE =b yielded the followRMS +%5 +%5 ing parameters: p 3.0 RMS" =0.09 for C /C "1, 2 1 E JE +%5 +%5
(2)
p 3.0 RMS" =0.06 for C /C "1.45, 2 1 E E +%5 +%5
(3)
p 3.2 RMS" =0.08 for C /C "1.97. 2 1 E JE +%5 +%5
(4)
N. Akchurin et al./Nucl. Instr. and Meth. in Phys. Res. A 409 (1998) 593—597
597
g—/ cone used for jet energy measurements. It is expected that for high luminosity operation of LHC these two terms will be approximately of the same value as the intrinsic jet energy resolution of quartz fibre calorimeter.
Acknowledgements
Fig. 4. Energy resolution for 1 TeV jets.
The small non-linearity of response is observed for this set of calibration constants but it is less than the energy resolution.
5. Summary and conclusions The data from beam test of the prototype of longitudinal-segmented quartz fibre calorimeter were used to simulate the expected response of such type of calorimeters to high energy jets. It was shown that the optimal jet energy resolution can be achieved for the appropriate calibration of signals from different longitudinal segments. As a result the jet energy resolution of p /E "3.0/JE =0.06 RMS +%5 +%5 can be achieved. The response will be linear with respect to the jet energy with the accuracy better than the energy resolution. It should be noted that the quoted resolution corresponds only to the intrinsic resolution of the calorimeter. In the real experiment there will be at least two other terms, namely the pile-up noise fluctuation and the fluctuations of the fraction of jet energy flowing out the
We would like to thank our colleagues from CMS, and in particular J.Bourotte and M. Haguenauer, who made the described beam tests possible. We are grateful to N.Doble, who provided us with particle beams of excellent quality. This project was carried out with financial support from CERN, the US Department of Energy, RMKIKFKI (Hungary, OTKA grant T 016823), the Scientific and Technical Research Council of Turkey (TU®BITAK), CICYT (Spain, grant AEN96-2051E), the International Science Foundation (grants M82000 and M82300), the State Committee of the Russian Federation for Science and Technologies, and the Russian Research Foundation (grant 9502-04815).
References [1] The CMS Collaboration, Technical Proposal, CERN/LHCC 94-39, (1994). [2] The CMS Collaboration, Technical Design Report, CERN/LHCC 97-31, (1997). [3] A. Contin et al., R&D Proposal for development of quartz fibre calorimetry, CERN DRDC/94-4 (1994) [4] G. Anzivino et al., Nucl. Instr. and Meth. A 357 (1995) 380. [5] P. Gorodetzky et al., Nucl. Instr. and Meth. A 361 (1995) 1. [6] V. Gavrilov et al., Study of Quartz Fiber Radiation Hardness, CMS TN-94-324. [7] N. Akchurin et al., Beam test results from a fine-sampling quartz fiber calorimeter for electron, photon and hadron detection, Nucl. Instr. and Meth. A 399 (1997) 202.
VII. TRENDS IN CALORIMETRY