Ereditato, A

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1CERN/SPSC 99-38, SPSC/M641LNGS-LOI 19/99, Addendum 1November 18, 1999Addendum to the OPERA Progress Report1. IntroductionWe give the cost estimate and the planning for the construction of the OPERA detector as wellas the milestones for the main decisions to be taken in order to have the detector ready at the beamstart-up. In the Progress Report [1] different options were considered for the main components ofthe detector. The estimate given in this addendum refers to a “baseline” configuration.2. Baseline detector configurationAs described in the Progress Report, two options are open for the configuration of the basic cellin the brick (compact and spacer). The compact cell is taken as the baseline for the cost estimate.With both cell options, only decays outside of the lead plate where the interaction occurred areconsidered for the performance estimate [1]. The decay topology is thus directly observed in bothcases. With the spacer configuration all 1-prong decay modes are characterised by a lowbackground. For the compact configuration only the leptonic decays are considered; the highertarget density however compensates the lower observed branching ratio, so that a similar numberof τ is observed. We are also presently investigating the capability of the compact configuration forthe observation of hadronic decays.For the target trackers and for the inner trackers of the muon spectrometer, the baseline retainedconsists of plastic scintillators with optical fibre read-out. For the spectrometer outer trackers wehave considered drift tubes.Both magnet options described in the Progress Report (toroidal or dipole magnets) useconventional techniques. The cost estimate is based on the dipole option.3. Cost estimate The cost for the construction of the OPERA detector has been estimated for all options. Thecost presented here refers to the baseline configuration. Other options under investigation may leadto lower costs. We give below a synthetic breakdown of the cost estimate. Table 1 gives theconstruction cost of one supermodule. Table 2 shows the construction cost of the detector,consisting of five supermodules. Equipment, instrumentation and tools comprise brick assemblingmachines, robots for brick handling, equipment for emulsion development, tools for magnetassembly, cabling and slow control.2Table 1. Cost estimate for the construction of one supermodule  (MCHF)Brick walls Emulsion   8.2Lead and mechanics   3.5Total 11.7Target trackers       1.7Spectrometer Magnet   0.9Trackers    2.0Total cost 16.3Table 2. Cost estimate for the construction of five supermodules  (MCHF)Equipment, instrumentation and tools        4.7Supermodules 81.5Total cost 86.2Apart from the standard expenditure, the running cost has to account for the replacement of thebricks where interactions have taken place.We request the support of the LNGS for infrastructure such as safety installations, cooling andventilation, uninterruptible power supplies, an additional small crane, control room and emulsionlaboratories. For these items, a cost of about 3 MCHF is estimated.4. Schedule and milestonesA detailed construction schedule has been estimated taking into consideration about 500activities, starting from the assembly of the basic components of OPERA. The schedule isessentially determined by technical constraints. The final assembly will take place in the cavern. Aserial supermodule installation has been considered, using two cranes. Fig. 1 gives the overallschedule for detector construction.3Fig. 1 Schedule for detector constructionThe milestones for the main choices in the detector design are:- April 2000 Emulsion temperature and humidity requirements- July 2000 Brick configuration- October 2000 MagnetsWall support structureTrackersTogether with the cost estimate and the schedule, the funding profile is being produced. Theemulsions make up almost half the cost. A substantial fraction of this expenditure is delayed until2004-2005. The other payments are distributed over the forthcoming five years.The sensitivity quoted in the Progress Report is based on the present central SuperKamiokandeparameter values, ∆m2 = 3.5x10-3 eV2 with maximal mixing. In a five year run, five OPERAsupermodules will detect about 18 ντ  events with a background of 1 event thus providing ameasurement of the νµ -ντ oscillation probability. Because of the low background, the disclosure ofνµ -ντ oscillation as the explanation of the SuperKamiokande observations can already come from asmaller number of events. As the oscillation signal scales with (∆m2)2 a squared mass difference of,for instance, 4.5x10-3 eV2 would result in 30 ντ  events (with unchanged background) or in 18ντ  events (0.6 background events) with 3/5 of the effort. Should in the forthcoming years a ∆m2higher than the present central value be favoured by experimental results, the construction strategycould be reviewed.45. Collaboration, management and responsibilitiesAt present, the Collaboration consists of physicists belonging to 21 Institutions from Europe andJapan. The definitive management structure will be defined around the time of the proposal withthe participation of new collaborators joining following the approval of the beam. Until then, themanagement is under the responsibility of an executive board with Kimio Niwa, Jean Paul Repellinand Paolo Strolin as members. Jean-Paul Fabre is acting as technical co-ordinator. The contact-person is Antonio Ereditato.A preliminary sharing of responsibilities for the detector construction is given in Table 3.Table 3. Sharing of responsibilities (preliminary)Installation CERN, LNF, LNGS, other InstitutionsEmulsion Ankara, Bari, Kobe, Nagoya, Naples, Rome, Salerno, TohoTarget CERN, Israel, LNF, Münster, Nagoya, NaplesTrackers Bern, Brussels, CERN, Hamburg, IN2P3, Israel, LNF, MoscowMagnets Brussels, CERN, LNFTrigger, DAQ, Controls Bern, Hamburg, IN2P3, MoscowScanning Ankara, CERN, Bari, Bern, IN2P3, Münster, Nagoya, Naples, Rome, Salerno, Toho, UtsunomiyaOffline Architecture CERN, IN2P3Analysis All InstitutionsReferences[1] OPERA. A long baseline ντ appearance experiment in the CNGS beam from CERN to GranSasso, CERN/SPSC 99-20, SPSC/M635, LNGS-LOI 19/99, August 27 1999 

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