- Email: [email protected]
Status of the CNGS experiment
Nuclear Physics B (Pmt.
ELSEVIER
Status
Suppl.) ill
(2002)
175477
of the CNGS experiment
NAKAMURA
Mitsuhiro
a *
“F-ken, Department of Physics, NAGOYA University, Furo-cho, Chikusa-ku, Nagoya 464-8602, JAPAN At CERN,
a new neutrino
Two fine-grained and intend
detectors,
to detect
will be the first clear and predicted
beam OPERA
I+ appearance evidence
theoretically
line directing among
Nakagawa
laboratory
at the Gran
oscillation
from
CERN.
suggested
is under
construction.
Sasso underground This
laboratory
appearance
by the Kamiokande
detection experiment
and Sakata.
The deficit of atmospheric v~, observed by the Kamiokande experiment [l], is considered as the evidence of the neutrino oscillation predicted by Maki, Nakagawa and Sakata [2]. The most probable explanation is the oscillation from v,, to v7. The first generation long base line experiment, K2K [3], will establish the existence of V~ disappearance in the accelerator neutrino beam. The second generation long base line experiments should prove the hypothesis that the disappearance of muon neutrino is originated by the neutrino oscillation from V~ to v,. The beam and the detector should have the capability of creating and detecting u, charge current interactions. The CNGS
underground
flux traveling
of neutrino
1. Introduction
2.
Sass0
will be installed
the neutrino
of the existence
by Maki,
to Gran
and ICARUS,
excavating the target chamber and the decay tunnel. According to the initial planning, excavation will be finished at the middle of 2002 and the installation of the beam line instrument will be finished at the end of 2004.
< E >v vF/pot/kton at GS Proton on target (pot) in shared mode per year yPronaPt T
$a~l+lK-h
17 GeV 5.44 x lo-l7 4.5 x 1019 negligible -0.85%
CNGS beam performance.
beam
The CNGS beam was designed to realize v, ap pearance experiment. Table.2 shows some basic parameters of the CNGS beam. The beam energy is above the tau lepton production threshold (- 3.5GeV) [4]. Th e expected number of neutrino interactions occurred in 1 kton detector per year is - 2500~: and - 16~:~ in the case of the SK expected neutrino oscillation parameters, i.e. sin’20 = 1 and Am2 = 2.5 x 10d3eV2. This new beam line is under construction. At the beginning of 2002, tunnel-boring machine was *I wish to thank to Prof. K.Elsener of CNGS Team and Prof. A. Rubbia of ICARUS for their help of the preparation of this report. I also wish to express thanks to OPERA collaborators for their cooperation.
3. OPERA
detector
OPERA is an Emulsion-counter Hybrid experiment applying the advanced nuclear emulsion technology, which was developed in Japan and have succeeded to detect v,“” in DONUT experiment [5] [6] [7]. Emulsion Cloud Chamber (ECC) is the unit of the OPERA detector. OPERA ECC is a stack of one-millimeter thick lead plates and thin nuclear emulsion films. A schematic view is shown in Fig.1. The size of the unit ECC brick is 1Ocm x 12.5cm perpendicular to the beam and
0920-5632/02/S - see front matter 0 2002 Elsevier Science B.V. All rights reserved. PII SO920-5632(02)01702-4
176
M. Nakamura /Nuclear Physics B (Pmt. Suppl.) I1 I (2002) 175-I 77
the thickness is about 7.5cm which contains 56 lead plates, 58 emulsion films and one thin plastic spacer. The thickness of one brick is corresponding to 10 X0. The weight of one ECC brick is about 8.3 kg.
(Lead Plate(lmmt)+Emu
ion Film 1 x56 /f--J
. . .
Figure 1. Basic component of the OPERA tor: Schematic view of a v,“” interaction OPERA ECC.
detecin the
The emulsion film has two nuclear emulsion layers of 44,um thick coated on the both sides of a plastic film of 205pm thickness. The emulsion films will be produced by Fuji Photo film Co., Ltd in Japan. The production will be performed by the production machines of commercial photographic films in order to deal with the large amount of emulsion films of 176000m’ for OPERA. After the production, erasing of the background random tracks recorded during the production (so-called refreshing) will be performed in the underground laboratory of TON0 mine located at Toki-shi of the Gifu prefecture, Japan. Then the films will be vacuum-packed, transported to the Gran Sasso underground laboratory and composed to the ECC bricks.
The OPERA detector will be composed from about 240 thousand ECC bricks. The resulted total mass is about 1.95ktons. Scintillating strip detectors read-out by wavelength shifting fibers will be at#tached to each ECC brick wall and tag the brick where the neutrino interaction occurs. The tagged ECC bricks will be extracted within a few days after the interaction occurs and processed for the analysis. Thanks to the advances of the current emulsion scanning system [l l] [8] [6], recorded tracks in the extracted bricks will be read-out automatically within a day. Using the read-out data, interaction vertex location in the brick, decay hunting and decay analysis will be performed as like the case of DONUT experiment [6]. For the candidate events, extra-bricks located downstream of the vertex will be extracted and the corresponding particles will be investigated further in order to check the existence of secondary leptons from the interaction. In the proposal, quite tight cut on the decayPt will be applied to the hadronic decay mode in order to suppress the secondary interaction background to be the level of order 0.1 events. The expected number of golden v,“” events is 11.8 in the case of 5 years running and the current SK parameters. The total background is estimated to be 0.74 events. Fig.2 shows the exclusion plot in the case of no-signal. The sensitivity (90% CL.) covers the SK expected region. The key components to realize the experiment are the mass-producible emulsion film and the super fast emulsion read-out system (so-called SUTS) compatible to the OPERA requirement. Until today, Nagoya group and Fuji Photo Film Co., Ltd have established the mass production sequences of emulsion film and fulfilled the requirement of erasing unwanted background tracks. Also, a prototype of the S-UTS was started its operation successfully in the last summer. 4. ICARUS
detector
ICARUS is utilizing a liquid Argon Time Projection Chamber as a tracking calorimeter [9]. Though it has tracking capability, it is too coarse to detect the tau lepton trajectory itself. There-
M. Nakamura/Nuclear
Physics
B (Proc.
Suppl.)
III
(2002) 175-l
77
111
problems. The important milestone to convince the experiment to the people was the operation of a large-scale module (so-called T600 module). In the last year, a 3OOton module, which is the half of T600, was operated at Pavia successfully. When several safety problems will be solved or answered confidently, the test module will be installed in the Gran Sasso underground laboratory. 5. Summary
Figure
2. Sensitivity
of the OPERA
experiment.
According to the current planning, the CNGS beam will start its operation at 2006, one year delay from the initial planning. OPERA will be installed in Hall C of Gran Sass0 underground laboratory until that time and will show several clear v,“” events within a year after the CNGS beam on, if the observation of Kamiokande and Super-Kamiokande is really caused by the v,, to v, oscillation. REFERENCES
fore, the target branching mode will be restricted to r + eyy and calorimetric information will be used to tag the v,“” event. The planned active target mass is 2.35ktons. The analysis scheme is almost same as the case of NOMAD analysis for the short base line experiment [lo]. At first, electron tracks were selected by the tracking information. The main contamination comes from vzc, of which ratio is about 0.85% of the events. In order to separate the v,“” signal from backgrounds, the total visible energy and the missing Pt will be used. For v,“” event, the total visible energy becomes smaller and the missing Pt becomes larger. Using these two parameters, a likelihood function will be defined and used as a separation parameter. After a moderate cut, the resulted expected number of events will be 11.9 with the background of 0.7 events in the case of the SK parameter and 5 years running, which is compatible to the sensitivity of the OPERA experiment described above. In OPERA experiment, scale up from one ton (the DONUT level) to - 2/cton is simply quantitative, i.e. increase the number of ECC bricks, but in ICARUS, scale up from the existing small module to the required scale contains qualitative
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Y.Fukuda et al, Phys. Lett. B335(1994)237245. Z.Maki, M.Nakagawa and S.Sakata, Prog. Theor. Phys. 53(1962)870. S.H.Ahn et al., Phys. Lett.B511(2001)178184. R.Bailey et al., CERN-SL/99-034(DI); INFN/AE-99/05. K.Kodamaet al., Phys. Lett. B504(2001)218. K.Kodama et al., submitted to Nucl. Instr. and Meth. A. OPERA Experiment proposal: CERN/SPSC 2000-028, SPSC/P318, LNGS P25/2000. S.Aoki for the collaboration, Nucl. Instr. and Meth. A473(2001)192-196. ICARUS proposal, LNGS-95/10,1995. J.Altegoer et al., Nucl. Instr. and Meth. A 404( 1998)98. T.NAKANO, BUTURI, 56(2001)411-418.(in Japanese).
ELSEVIER
Status
Suppl.) ill
(2002)
175477
of the CNGS experiment
NAKAMURA
Mitsuhiro
a *
“F-ken, Department of Physics, NAGOYA University, Furo-cho, Chikusa-ku, Nagoya 464-8602, JAPAN At CERN,
a new neutrino
Two fine-grained and intend
detectors,
to detect
will be the first clear and predicted
beam OPERA
I+ appearance evidence
theoretically
line directing among
Nakagawa
laboratory
at the Gran
oscillation
from
CERN.
suggested
is under
construction.
Sasso underground This
laboratory
appearance
by the Kamiokande
detection experiment
and Sakata.
The deficit of atmospheric v~, observed by the Kamiokande experiment [l], is considered as the evidence of the neutrino oscillation predicted by Maki, Nakagawa and Sakata [2]. The most probable explanation is the oscillation from v,, to v7. The first generation long base line experiment, K2K [3], will establish the existence of V~ disappearance in the accelerator neutrino beam. The second generation long base line experiments should prove the hypothesis that the disappearance of muon neutrino is originated by the neutrino oscillation from V~ to v,. The beam and the detector should have the capability of creating and detecting u, charge current interactions. The CNGS
underground
flux traveling
of neutrino
1. Introduction
2.
Sass0
will be installed
the neutrino
of the existence
by Maki,
to Gran
and ICARUS,
excavating the target chamber and the decay tunnel. According to the initial planning, excavation will be finished at the middle of 2002 and the installation of the beam line instrument will be finished at the end of 2004.
< E >v vF/pot/kton at GS Proton on target (pot) in shared mode per year yPronaPt T
$a~l+lK-h
17 GeV 5.44 x lo-l7 4.5 x 1019 negligible -0.85%
CNGS beam performance.
beam
The CNGS beam was designed to realize v, ap pearance experiment. Table.2 shows some basic parameters of the CNGS beam. The beam energy is above the tau lepton production threshold (- 3.5GeV) [4]. Th e expected number of neutrino interactions occurred in 1 kton detector per year is - 2500~: and - 16~:~ in the case of the SK expected neutrino oscillation parameters, i.e. sin’20 = 1 and Am2 = 2.5 x 10d3eV2. This new beam line is under construction. At the beginning of 2002, tunnel-boring machine was *I wish to thank to Prof. K.Elsener of CNGS Team and Prof. A. Rubbia of ICARUS for their help of the preparation of this report. I also wish to express thanks to OPERA collaborators for their cooperation.
3. OPERA
detector
OPERA is an Emulsion-counter Hybrid experiment applying the advanced nuclear emulsion technology, which was developed in Japan and have succeeded to detect v,“” in DONUT experiment [5] [6] [7]. Emulsion Cloud Chamber (ECC) is the unit of the OPERA detector. OPERA ECC is a stack of one-millimeter thick lead plates and thin nuclear emulsion films. A schematic view is shown in Fig.1. The size of the unit ECC brick is 1Ocm x 12.5cm perpendicular to the beam and
0920-5632/02/S - see front matter 0 2002 Elsevier Science B.V. All rights reserved. PII SO920-5632(02)01702-4
176
M. Nakamura /Nuclear Physics B (Pmt. Suppl.) I1 I (2002) 175-I 77
the thickness is about 7.5cm which contains 56 lead plates, 58 emulsion films and one thin plastic spacer. The thickness of one brick is corresponding to 10 X0. The weight of one ECC brick is about 8.3 kg.
(Lead Plate(lmmt)+Emu
ion Film 1 x56 /f--J
. . .
Figure 1. Basic component of the OPERA tor: Schematic view of a v,“” interaction OPERA ECC.
detecin the
The emulsion film has two nuclear emulsion layers of 44,um thick coated on the both sides of a plastic film of 205pm thickness. The emulsion films will be produced by Fuji Photo film Co., Ltd in Japan. The production will be performed by the production machines of commercial photographic films in order to deal with the large amount of emulsion films of 176000m’ for OPERA. After the production, erasing of the background random tracks recorded during the production (so-called refreshing) will be performed in the underground laboratory of TON0 mine located at Toki-shi of the Gifu prefecture, Japan. Then the films will be vacuum-packed, transported to the Gran Sasso underground laboratory and composed to the ECC bricks.
The OPERA detector will be composed from about 240 thousand ECC bricks. The resulted total mass is about 1.95ktons. Scintillating strip detectors read-out by wavelength shifting fibers will be at#tached to each ECC brick wall and tag the brick where the neutrino interaction occurs. The tagged ECC bricks will be extracted within a few days after the interaction occurs and processed for the analysis. Thanks to the advances of the current emulsion scanning system [l l] [8] [6], recorded tracks in the extracted bricks will be read-out automatically within a day. Using the read-out data, interaction vertex location in the brick, decay hunting and decay analysis will be performed as like the case of DONUT experiment [6]. For the candidate events, extra-bricks located downstream of the vertex will be extracted and the corresponding particles will be investigated further in order to check the existence of secondary leptons from the interaction. In the proposal, quite tight cut on the decayPt will be applied to the hadronic decay mode in order to suppress the secondary interaction background to be the level of order 0.1 events. The expected number of golden v,“” events is 11.8 in the case of 5 years running and the current SK parameters. The total background is estimated to be 0.74 events. Fig.2 shows the exclusion plot in the case of no-signal. The sensitivity (90% CL.) covers the SK expected region. The key components to realize the experiment are the mass-producible emulsion film and the super fast emulsion read-out system (so-called SUTS) compatible to the OPERA requirement. Until today, Nagoya group and Fuji Photo Film Co., Ltd have established the mass production sequences of emulsion film and fulfilled the requirement of erasing unwanted background tracks. Also, a prototype of the S-UTS was started its operation successfully in the last summer. 4. ICARUS
detector
ICARUS is utilizing a liquid Argon Time Projection Chamber as a tracking calorimeter [9]. Though it has tracking capability, it is too coarse to detect the tau lepton trajectory itself. There-
M. Nakamura/Nuclear
Physics
B (Proc.
Suppl.)
III
(2002) 175-l
77
111
problems. The important milestone to convince the experiment to the people was the operation of a large-scale module (so-called T600 module). In the last year, a 3OOton module, which is the half of T600, was operated at Pavia successfully. When several safety problems will be solved or answered confidently, the test module will be installed in the Gran Sasso underground laboratory. 5. Summary
Figure
2. Sensitivity
of the OPERA
experiment.
According to the current planning, the CNGS beam will start its operation at 2006, one year delay from the initial planning. OPERA will be installed in Hall C of Gran Sass0 underground laboratory until that time and will show several clear v,“” events within a year after the CNGS beam on, if the observation of Kamiokande and Super-Kamiokande is really caused by the v,, to v, oscillation. REFERENCES
fore, the target branching mode will be restricted to r + eyy and calorimetric information will be used to tag the v,“” event. The planned active target mass is 2.35ktons. The analysis scheme is almost same as the case of NOMAD analysis for the short base line experiment [lo]. At first, electron tracks were selected by the tracking information. The main contamination comes from vzc, of which ratio is about 0.85% of the events. In order to separate the v,“” signal from backgrounds, the total visible energy and the missing Pt will be used. For v,“” event, the total visible energy becomes smaller and the missing Pt becomes larger. Using these two parameters, a likelihood function will be defined and used as a separation parameter. After a moderate cut, the resulted expected number of events will be 11.9 with the background of 0.7 events in the case of the SK parameter and 5 years running, which is compatible to the sensitivity of the OPERA experiment described above. In OPERA experiment, scale up from one ton (the DONUT level) to - 2/cton is simply quantitative, i.e. increase the number of ECC bricks, but in ICARUS, scale up from the existing small module to the required scale contains qualitative
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Y.Fukuda et al, Phys. Lett. B335(1994)237245. Z.Maki, M.Nakagawa and S.Sakata, Prog. Theor. Phys. 53(1962)870. S.H.Ahn et al., Phys. Lett.B511(2001)178184. R.Bailey et al., CERN-SL/99-034(DI); INFN/AE-99/05. K.Kodamaet al., Phys. Lett. B504(2001)218. K.Kodama et al., submitted to Nucl. Instr. and Meth. A. OPERA Experiment proposal: CERN/SPSC 2000-028, SPSC/P318, LNGS P25/2000. S.Aoki for the collaboration, Nucl. Instr. and Meth. A473(2001)192-196. ICARUS proposal, LNGS-95/10,1995. J.Altegoer et al., Nucl. Instr. and Meth. A 404( 1998)98. T.NAKANO, BUTURI, 56(2001)411-418.(in Japanese).