LARGE HADRON COLLIDER COMMITTEE Minutes of the one-hundredth-and-thirty-second meeting held on Thursday and Friday, 30 November -1 December 2017

Transcription

1 CERN/LHCC LHCC-132 November 2017 LARGE HADRON COLLIDER COMMITTEE Minutes of the one-hundredth-and-thirty-second meeting held on Thursday and Friday, 30 November -1 December 2017 OPEN SESSION STATUS REPORTS 1. LHC Machine Status Report: Roderik Bruce 2. ALICE Status Report: Grazia Luparello 3. ATLAS Status Report: Nikolina Ilic 4. CMS Status Report: Meenakshi Narain 5. LHCb Status Report: Jean-François Marchand 6. MoEDAL Status Report: James Pinfold 7. TOTEM Status Report: Ken Osterberg CERN-LHCC / LHCC /12/2017 CLOSED SESSION: Present: 1. Procedure C. Bloise, J. Boyd, V. Beckmann, H. Burkhardt, P. Burrows, R. Calabrese, D. Denisov, J. Dunlop, G. Eigen, E. Elsen, F. Forti (Chairperson), E. Kajfasz, P. Krizan, K. Krüger, F. Kunne, M. Kuze, A. Kuzmin, M. Mangano, P. Newman, S. Smith, B. Panzer-Steindel, C. Sfienti, D. Waters, T. Wengler (Scientific Secretary), W. Wisniewski, H. Wilkens The chairperson welcomed the committee members and reminded the committee that the minutes of the previous session were already approved by . The chairperson informed the committee that David Waters has been assigned as referee to the WLCG project, bringing the team of referees to full strength and ensuring a good balance of expertise on the various experiments across the referee team. The chairperson also welcomed Katja Krüger and Roberto Calabrese, who will take up their respective roles as LHCb and ATLAS referees from the next session of the LHCC. The chairperson thanked the outgoing members Phil Burrows and Gerald Eigen for their many invaluable contributions to the work of the committee. 2. Report from the Director of Research and Computing The Director of Research and Computing (DRC) reported on issues related to the LHC. The accelerator has had another excellent year of running, with the collected data sets exceeding the expectations. The special run programme worked very well, and also the luminosity delivered to LHCb met the expectations. The DRC reported that Prof.

2 2 Halina Abramowicz has been appointed to serve as Strategy Secretary for the next update of the European Strategy for Particle Physics. Input on the strategy will be collected from the community until the end of 2018, as a basis for the discussions to be held during The strategy group will consider a wide range of options, including CLIC, physics beyond colliders and also physics programmes at external labs. ILC plans will also be clarified by the end of The HL-LHC is already part of the European Strategy, with a study group under way to present the overall physics programme. The DRC also reported on the Phase-II upgrades, where many positive interactions have taken place with the funding agencies involved. The common fund for HL-LHC was approved in October 2017 at a level of 10% of the overall upgrade cost. 3. Report from the LHC Programme Co-ordinator The 2017 physics run finished on November 26th, after a very successful period in particular following the second Technical Stop, with records achieved in many parameters: peak luminosity (2 x cm 2 s 1 ), fill length (27h), machine availability (86.6%), b* (30 cm), and integrated luminosity. In this period, the 8b4e bunch pattern was used, to mitigate the effect from fast losses caused by cell 16L2, which limited the number of bunches to Despite the lower number of bunches, good luminosity performance for ATLAS and CMS was achieved by reducing the b* to 30 cm and using a low emittance beam. In this configuration, the pileup in ATLAS and CMS becomes very high and both experiments levelled the luminosity at 1.5 x cm 2 s 1, corresponding to a pileup of about 60. With the 8b4e scheme LHCb received 25% less collisions. This was partially compensated for by keeping fills longer than it would be optimal for luminosity accumulation in ATLAS in CMS. The total delivered luminosity in 2017 was above expectations for all experiments, with about 50 fb 1 for ATLAS/CMS, 1.86 fb 1 for LHCb and 17 pb 1 for ALICE. Proton reference data at 5.02 TeV needed for the heavy ion physics programme was taken, with the requested data samples delivered in less than the scheduled 11 days due to very high machine availability. The scheduled 900 GeV high b* run in 2017, for elastic scattering measurements at lower energy by TOTEM and ATLAS-ALFA, was cancelled, after beam tests showed too much beam background in the experiments for a precision measurement. A further test of the background was carried out, and the experiments and machine experts will analyse the results before deciding to request this run in In the remaining time 13 TeV data was taken with low-pileup in CMS and ATLAS, which resulted in an important data sample for W-boson physics. LHCb and ALICE took pp physics data to increase their pp data samples. Following a request from CMS, the 2017 schedule was changed to start the year end technical stop one week earlier than originally foreseen. This is to allow CMS to diagnose and fix a powering problem with their pixel detector, and will allow them to access the faulty components before the end-of-year CERN closure. Planning for the 2018 LHC setup is under way. The experiments request to run with 2500 bunches and the 25 ns BCMS injection scheme to obtain a large integrated luminosity with reduced pileup compared to The machine configuration will be discussed at the Evian workshop in 2017, and should be finalised at the Chamonix workshop at the end of January Special run requests for 2018 will likely include a 90 m b* run for TOTEM and CMS, to carry out low-mass diffractive studies, and a

3 3 request for the low-energy high b* elastic scattering measurements by TOTEM and ATLAS-ALFA. There is a 4 week PbPb run scheduled at the end of the 2018 running period. 4. Test Beams The draft 2018 injector schedule anticipates 32.5 weeks of proton physics at the PS East Hall and 31 weeks at the SPS North Hall. It will be followed by 4 weeks of Pb ion physics. 90 requests for beam time have been received, out of which over 70 for testbeams. The LHC experiments and their upgrade programmes constitute the majority of the requests. A timeline of all the requests and a potential implementation of a user schedule was presented. There remains a competition for beam-time towards the end of the year in the H4 beam line, between CMS and the LHC muon detectors R&D and the Neutrino Platform. LHCb has requested a one-week period of SPS beam with 25 ns bunch structure to pre-commission the full readout chain with a time structure of the beam close to the LHC beam. The LHCC acknowledges the request by LHCb for 25 ns test beam. Given the impact this request would have on the facility and other users, the LHCC requests a more detailed presentation of the benefits expected from these tests before endorsing this request. The LHCC also encourages LHCb to find alternative means to achieve these tests, for example by installing test setups in the LHCb cavern. 5. Discussion with ALICE Scientific output and current activities: ALICE continues to make excellent progress on its physics programme, with 6 papers submitted since the last session of the LHCC, bringing the total number of publications to 194. Recent results include measurements of the J/ψ elliptic flow and (Anti-) 4 He production in PbPb collisions, and the production of charm jets in ppb collisions. ALICE successfully concluded its 2017 data-taking campaign with a rich harvest of recorded data, including 866M minimum bias pp events at 13 TeV, 1.7M Xe- Xe events at 5.44 TeV, and 986M minimum bias pp events at 5 TeV. The detector has been operating very well, with a data taking efficiency of 92%. After switching to Ne-CO 2 gas in March, the TPC distortions returned to run 1 levels, however ROC instabilities reappeared as well. The decision was therefore taken to return to Ar gas for the running next year. Phase-I upgrades: Good progress has been reported on the upgrade programme. The man-power and resource allocation for the MFT have been presented, now involving more permanent staff, with funds secured for the existing personnel. For the TPC the failure of the IROC reported at the last session was tracked to a damaged High Voltage cable inside the chamber. Additional measures have been added to the QA protocols to avoid this issue in the future. Other production chambers tests in the ALICE cavern have shown no sparks or instabilities in long term tests. All QA procedures have been established and are being

4 4 rigorously applied at all production sites. 60% of the required GEM foils have been produced and the total yield is 90%. 15% of ROCs have been produced so far and two ROCS have been extensively tested at P2. The HV EDR has been completed on November 24th. Results have been shown from preliminary tests of the SAMPA V3 and V4 chips, with the expected improved high rate behaviour observed for V4. Although the results are promising, full qualifications for both versions remain to be done. The LHCC congratulates ALICE on the successful data taking in 2017, and the rich physics output, and on the continuous progress made on its upgrade programme. The LHCC acknowledges the good progress made in particular on the TPC upgrade, but notes that it remains an area of concern. The LHCC encourages ALICE to continue its efforts in particular to guarantee a thorough test of all ROCs and FEC after installation in the field cage. A detailed plan of these final tests will be presented at the next LHCC. The LHCC urges ALICE to thoroughly qualify both SAMPA V3 and V4 chips and to proceed to a complete test of both MCH and TPC front-end cards before any decision is taken concerning the chip baseline solution. 6. Discussion with ATLAS Scientific output and current activities: ATLAS continues to deliver high quality physics results with 696 papers submitted to date, including 26 since the last LHCC. Recent new results include new top mass measurements, evidence for Higgs boson production via associated tth production, a measurement of the triple-differential Drell-Yan cross-section, as well as a measurement of ZZ 4l, that was also used to search for neutral triple gauge couplings not present in the SM. ATLAS has had a successful data taking campaign in 2017, with 47.1 fb 1 of 13 TeV data recorded, with an average data taking efficiency of 93.3%. In addition, data were collected during multiple special runs. All detector systems worked well. The detector coped well with the high pile-up conditions, which were levelled at around 60, with maximum values of up to 80 for short periods. The planning for the YETS is being finalised, activities will include a leak-fixing campaign on the RPC system, apart from many standard maintenance tasks to be performed. Phase-I upgrades: Brief reports were delivered on the LAr and TDAQ upgrade projects for Phase-I, which are on track, with production and testing making good progress. Large progress has also been reported in all areas of the NSW upgrade, however the schedule remains very tight, with several challenging milestones still to be passed. Among the most critical items on the electronics side are the evaluation of the VMM3a and ROC1a chips. Packaged chips are expected in January, with the results of the evaluation expected to be available for the LHCC

5 5 comprehensive review in February. The chamber production for the NSW is under way for both stgcs and Micromegas, however the required production speed has not been reached yet. More solid data on the production speed will be available in time for the next session of the LHCC. Phase-II upgrades: The ITk Strip Tracker TDR has already been approved previously. The MoU is currently under development, and the project is on track. A revised version of the Muon TDR was approved by the LHCC to proceed to the UCG review on November 28 th, with the UCG review taking place later on the same day. The LHCC report is appended to these minutes below. The UCG report is listed in the documents section of these minutes. The TDR will be submitted, with the recommendation for approval, to the next Research Board. The LAr and Tile TDRs have been submitted to the LHCC and underwent their respective LHCC review this week. The corresponding reports are appended to these minutes below. In both cases the LHCC recommends proceeding to the UCG review. UCG kick-off meetings took place this week for both TDRs, with no major problem apparent at this point. The TDAQ and Pixel TDRs will be submitted in December, with the corresponding UCG packages on track for submission in January. An expression of interest for a High Granularity Timing Detector as part of the Phase-II upgrade was submitted to the LHCC for this session, as described in a separate section below. The LHCC congratulates ATLAS on the successful operation of the detector in 2017 and the impressive amount of new physics results produced. The LHCC acknowledges the good progress made in the NSW project, however the completion of both NSWs in time for installation in LS2 remains in serious doubt. The LHCC continues to encourage contingency planning for cases in which full assembly of one or both NSWs might not be possible for their installation in LS2. 7. Discussion with CMS Scientific output and current activities: CMS continues to make excellent progress on its physics programme, with 685 papers submitted to date, including 36 since the last session of the LHCC. Recent results include new limits on the decay of the Higgs to two muons, evidence for tzq production, and the observation of top production in ppb collisions. CMS has recorded 45.1 fb 1 of 13 TeV pp data in 2017, with a data taking efficiency of 90.3%. In addition, data was collected during multiple special runs. Although in the initial part of the year data taking efficiency was limited by issues in the commissioning of the new pixel detector, in the final part of the run an efficiency comparable to previous years was obtained. The detector is generally working well, with problems encountered in the pixel

6 6 detector. Periodic dis-/enable cycles were needed to recover modules affected by SEUs in a small FE chip (Token Bit Manager (TBM)). This issue is understood, and will be fixed during LS2 by replacing layer 1 of the barrel pixel detector. However, since October 5 th, the DC-DC converters used in performing these cycles have started to fail, leading to an increasing fraction of inactive channels. The cause of these failures is currently not understood. While the impact on data quality is still relatively small at this point, it is clear that this issue needs to be addressed. It has therefore been decided with the CERN management to end the 2017 run one week early in order to be able to extract the pixel detector, and investigate and repair the failing converters. Phase-I upgrades: The Phase-I upgrades of CMS are nearly complete. The upgrade of the hadron endcap calorimeter, which is planned for full installation early 2018, uses the same DC-DC converters as used in the pixel detector. No issues have been observed here in extensive tests, including running one sector in the collision hall during The baseline plan hence remains to proceed with full installation as planned. Phase-II upgrades: The Phase-II upgrades are proceeding as planned. The Tracker TDR underwent its UCG review this week. The report is listed in the documents section of these minutes below. The TDR will be submitted, with the recommendation for approval, to the next Research Board. The Muon and Barrel calorimeter TDRs have been submitted to the LHCC in September and underwent their respective LHCC reviews this week. The corresponding reports are appended to these minutes below. In both cases the LHCC recommends proceeding to the UCG review. UCG kick-off meetings took place this week for both TDRs, with no major issues apparent at this point. Interim TDRs on the Level 1 and HLT/DAQ Phase-II upgrades have been submitted to the LHCC in September. While the full review will only take place once the TDRs have been submitted at a later date, the interim documents serve to understand the overall scope, feasibility, and cost of the systems in the context of the full Phase-II upgrade. In both cases design, schedule and cost estimate were found to be reasonable. The Calorimeter Endcap TDR was partially submitted to the LHCC this week, with the performance chapter to be added before the end of the year. A technical proposal for a MIP Timing Detector as part of the Phase-II upgrade was submitted to the LHCC for this session, as described in a separate section below. The LHCC congratulates CMS on the successful data taking in 2017, and the rich physics output produced during this year. The LHCC encourages CMS to not only investigate and repair the DC-DC converter issues observed in the pixel detector, but also to consider possible implications for other detectors using the same, or similar, components. The LHCC notes that the very tight schedule for the pixel detector installation has limited the time allocated for commissioning the detector, and encourages the

7 7 experiment to plan on sufficient checkout and commissioning time for future installations. Based on the interim TDRs submitted, the LHCC finds the design, schedule and cost estimates of the Level 1 and HLT/DAQ systems for Phase-II reasonable, and encourages CMS to proceed to develop the full TDRs, planned for 2020 and 2021 respectively. 8. Discussion with LHCb Scientific output and current activities: LHCb continues to have a rich scientific output, with a total of 405 publications to date, including 9 new papers since the last session of the LHCC. New results dd include the measurement of φ s in B 0 s (K + π )(K π + ) decays, the first measurements of relative branching fractions of charmless four-body Λ 0 0 b and Ξ b b decays, and evidence for the rare decay Σ + pµµ. LHCb has reached its target of recording 1.7 fb 1 in All detector subsystems are running well, with an average data taking efficiency of 91.4%. For 2018, LHCb hopes to get fb 1 delivered, which would open the possibility of establishing lepton universality violation at more than 5s assuming the current central value. Phase-I upgrades: Good progress has been reported on the Phase-I upgrades. For the VELO the micro-channel in silicon cooling has been chosen. The Velopix V2 chip is now available for testing, with first results showing good performance. The yields are above 50%. SciFi and all other subsystems are making good progress. On the UT upgrade a bug spotted in V1 of the SALT chip was not fixed for the V2 engineering run. While this bug is easy to fix, it will likely require a further engineering run, causing additional delays in the UT schedule, where the SALT chip is on the critical path. The software and computing TDR is being finalised, with a planned submission to the LHCC early in It was noted that it might be problematic to fit the computing requirements for run 3 into a flat budget scenario. The LHCC congratulates LHCb on its rich scientific output and successful detector operations in 2017, and commends the collaboration for the progress made on its upgrade programme. The LHCC acknowledges that the impact of an enlarged data set in 2018 is likely to be very significant for LHCb. This will be taken into account in the optimization of running condition for While good progress has been reported on the upgrades, the LHCC is concerned that delays start to become critical and might affect the end date and installation of the Phase-I upgrades. We expect the catch-up of the delayed milestones to happen by the next LHCC meeting. The LHCC considers the delays worrying in particular in the UT project, and encourages the LHCb management to optimise the distribution of the workload among the involved groups, and involve new manpower as needed, to recover

8 8 the schedule delays. The LHCC expects to receive the Software and Computing TDR in early 2018 and to proceed to the scientific and technical review. For a complete cost and schedule review, also the resource requirements and their availability for Run 3 need to be sufficiently well understood and the LHCC looks forward to reviewing these in the Computing Model TDR which is due in Q Concerning the LHCb request for a 25ns bunch spacing test beam period, see test beam section above. 9. Discussion with MoEDAL In the year since MoEDAL was last reviewed in detail by the LHCC, the collaboration s passive detectors surrounding LHCb have been exposed to the full delivered LHC luminosity, amounting to around 2 fb 1. First limits on magnetic monopole Drell-Yan production in 13 TeV proton-proton collisions have been published based on passing the aluminium block Magnetic Monopole Trackers through a SQUID device. They include world-leading constraints in some regions of phase space. The collaboration continues to grow slowly and has added a Machine Deep Learning group, charged with optimising signal extraction from the plastic Nuclear Track Detectors. A prototype MAPP (MoEDAL Apparatus for Penetrating Particles ) detector is at CERN and ready for deployment in a service tunnel a few tens of metres from the LHCb interaction point in the 2018 run. This detector consists of scintillator bars and PMTs and will be sensitive to anomalously penetrating particles that are able to pass through the intervening rock. Since MoEDAL will not reach its originally requested 10 fb 1 exposure before LS2, it is developing a proposal to continue in LHC Run 3. The LHCC congratulates the MoEDAL collaboration on the publication of the first magnetic monopole search in 13 TeV pp collisions. The LHCC notes that MoEDAL is pursuing an innovative programme that is complementary to the other LHC experiments and does not significantly impact upon them. The LHCC encourages MoEDAL to develop a detailed proposal for post-ls2 running, including the MAPP detectors, that should cover physics motivation, financial and manpower resource requirements and implications for LHCb. 10. Discussion with TOTEM/CT-PPS Scientific output and current activities: CT-PPS had a successful 2017 run, recording 39.5 fb 1 out of 43.1fb 1 delivered. The analysis of the CT-PPS 2016 data is well advanced, with the publication of the dilepton-pair mass spectrum under collaboration-wide review, and the diphoton results expected to be available for the Winter conferences. The lattice alignment and detector alignment for the 2017 data are in progress, and should be ready for the start of data analysis in two weeks. Results for final states like WW, ZZ, Zγ will be carried out on the fully data set. The TOTEM analysis of the total, elastic and inelastic cross sections at 13 TeV, from the b* = 90 m runs in 2016, is completed, and the publication is expected

9 9 soon. The first measurement of the ρ parameter at 13 TeV, from the b* = 2.5 km run, has a 10% precision, and points to a possible evidence for the exchange of a colourless 3-gluon bound state. These measurements underscore the importance of a future run at energies as low as allowed by the accelerator. TS2 and YETS activities: All activities planned for TS2 have been carried out successfully. In particular, the vertical repositioning of the tracking pixel detectors has corrected the radiation-induced loss of efficiency, leading to optimal conditions for data taking after TS2. Tracking and timing sensors that have been subject to large radiation doses will be replaced during the YETS. The proposed configuration will feature pixel detectors for the horizontal tracking roman pots (RPs) and silicon strips for vertical tracking. The horizontal timing RPs will host two planes of diamond sensors each, and two planes of the novel double-diamond detectors. Ultra-fast Silicon Detectors and new SAMPIC electronics for the TOTEM vertical timing RPs required by the b* = 90 m run are being assembled and tested, for installation during the YETS and TS1. Special runs: The top priority for TOTEM and CMS in 2018 will be the b* = 90 m run, for low-mass diffraction studies. The 900 GeV run at high b* will remain on the to-do list for TOTEM until its successful completion. The LHCC congratulates CT-PPS for the successful data taking and for the physics results released so far. The LHCC recognizes the physics potential of CT-PPS, and the possible value of continued operations in run 3, in order to fully exploit the physics programme. The definition of this programme, however, must emerge from a complete and urgent review of the long-term potential, addressing both the physics studies presented in the TDR, and additional physics opportunities that may have emerged since, also in view of the lessons learned from the existing data. The LHCC endorses the proposed detector configuration for 2018, and supports the continued assessment, including via dedicated R&D, of the different technologies under consideration, also in view of the possible long-term (run 3) evolution of the TOTEM and CT-PPS detectors. The LHCC recommends that continued attention be given to the needs of CT- PPS, in the planning for the 2018 LHC high-luminosity running conditions. The LHCC welcomes the additional progress made towards the eventual merge of the TOTEM collaboration with CMS. 11. Discussion with WLCG WLCG infrastructure continues to operate very well, with all experiments making full use of the pledged resources. A flood affected the Tier-1 centre CNAF / INFN (Bologna), on November 9 th, The status of about 100 flooded tapes and hardware is still being evaluated. It is expected to be operational again in 02/2018. Preparations

10 10 have started for run 3, however the resources needed depend on the running conditions of the accelerator, which are expected to be defined as a first baseline after the Chamonix meeting. It was noted that in particular for LHCb it might be problematic to fit the computing requirements for run 3 into a flat budget scenario. ALICE presented updated parameters for its 2018/19 resource request, in particular a MC/raw data ratio of 1.4 for pp and 0.3 for PbPb, which is endorsed by the LHCC. On the computing in the HL-LHC era a summary of the HSF community white paper (CWP) is expected by the end of the year. A WLCG strategy document will then be prepared as a specific view of the CWP, prioritizing R&Ds relevant to the HL-LHC computing challenge. A draft of this document will be presented to the February LHCC session, with the WLCG TDR for HL-LHC still foreseen for On the software side the strategy of integrating Geant 4 and Geant V developments into the future main version of Geant is being defined. The LHCC recognises the need of a baseline for the run 3 machine running conditions to guide the WLCG in its resource planning, and requests such information to be provided to the WLCG as soon as possible. 12. Discussion on ATLAS/CMS Timing Detectors for Phase-II Both ATLAS and CMS have prepared proposals to install new timing detectors as part of their Phase-II upgrades. The main purpose of these detectors is the mitigation of the effect of the large pile-up expected under HL-LHC conditions (up to 200). The additional timing information would allow to spread the many interaction vertices per bunch crossing in time as well as space, thereby aiding the track-vertex assignment, with benefits for particle flow variables, jet finding, and b-tagging, among others. The plan is to essentially retain the performance available at a pile-up of about 50, as routinely present today, under HL-LHC pile-up conditions. The two experiments have submitted the proposals to the present session of the LHCC, including presentations of physics motivation and preliminary technical design. The committee briefly discussed the proposals in closed session following the presentations and discussion in the open part of the meeting. Pending a more thorough review the committee finds these proposals an interesting addition to the Phase-II upgrades. However, given the substantial cost of the proposed detectors, and the potential impact on other Phase-II upgrades, a strong physics motivation is needed to recommend proceeding with these projects. The referees will hence concentrate on the review of the physics gain these detectors can provide, with a first report expected by the next session of the LHCC. In particular the impact on other Phase-II upgrades will then also have to be carefully evaluated. 13. REFEREES The LHCC referee teams for this session are as follows: ALICE: C. Bloise, J. Dunlop, P. Newman, C. Sfienti (Co-ordinator) ATLAS: V. Beckmann, P. Burrows (Co-ordinator), F. Kunne, W. Wisniewski CMS: D. Denisov (Co-ordinator), E. Kajfasz, A. Kuzmin, D. Waters LHCb: G. Eigen (Co-ordinator), P. Krizan, T. Kuhr, M. Kuze

11 11 LHCf, MoEDAL, TOTEM: C. Bloise, A. Kuzmin, M. Mangano (Co-ordinator), P. Newman LCG: V. Beckmann, J. Dunlop, T. Kuhr (Co-ordinator), D. Waters 14. The LHCC received the following documents: CERN-LHCC Minutes of the one hundred and thirty-first meeting of LHCC held on 10 and 11 May 2017 CERN-LHCC Technical Design Report for the Phase-II Upgrade of the ATLAS LAr Calorimeter CERN-LHCC Technical Design Report for the Phase-II Upgrade of the ATLAS Tile Calorimeter CERN-LHCC The Phase-2 Upgrade of the CMS Endcap Calorimeter CERN-LHCC Technical Proposal for a MIP timing detector in the CMS Experiment Phase-II upgrade CERN-LHCC Expression of Interest: A High-Granularity Timing Detector for the ATLAS Phase-II Upgrade CERN-LHCC /UCG-023 Report on the UCG review of the CMS Phase-II Tracker TDR CERN-LHCC /UCG-024 Report on the UCG review of the ATLAS Phase-II Muon Spectrometer TDR DATES FOR LHCC MEETINGS Dates for February May Thorsten Wengler September E mail: Thorsten.Wengler@cern.ch 30 Nov - 1 Dec Tel LHCC Secretariat: Patricia Mage (Bldg. 3/R-018) Tel patricia.mage@cern.ch APPENDICES A. Report on the LHCC review of the ATLAS Phase-II Muon Spectrometer TDR Review panel: Philip Burrows, Paul Karchin, Pierluigi Paolucci, Blair Ratcliff, Rob Roser (chair), Concettina Sfienti, William Wisniewski, Darian Wood The LHCC reviewed the ATLAS Muon Spectrometer Phase-II Upgrade Technical Design Report required for high luminosity running for the second time. At the last meeting, the committee granted conditional approval for this upgrade but asked for increased clarity in several areas. Namely, the proponents needed to identify clearly

12 12 what is the baseline plan for the muon upgrade. The R&D described should be presented as possible options. Finally, if this R&D effort is successful and can be adopted, to describe what the impact to the overall project would be in shifting the baseline. Based on the committee s guidance, the ATLAS muon group produced an updated version of the TDR with several improvements for LHCC review. They provided updated performance plots and improved clarity on how simulation was used for physics prospects. A detailed discussion on greenhouse gas impact and plans was added. A refined RPC discussion clarifying what is in the baseline design and R+D opportunities to improve performance was also added. The power supply chapter was modified to include more modules than was originally described. Finally, the management chapter was significantly updated with much more detail than the original version. The committee was pleased with added clarity provided in the updated version of the TDR and fully approve this version. The committee was also quite impressed with the latest round of presentations and information. In a few short months, it seemed that this upgrade project is functioning much more like a coherent team with significantly improved communications and ownership of the project that did not come across in the first review. B. Report on the LHCC review of the CMS Phase-II Barrel calorimeter TDR Review panel: Franco Bedeschi (chair), Marco Delmastro, Dmitri Denisov, Doug Glenzinski, Gerald Eigen, Alex Kluge, Alex Kuzmin, Francesco Lanni Over a period of about two months the CMS Phase II Barrel Calorimeter review panel has evaluated the proposed upgrade of the CMS barrel calorimeter. The main motivations for the upgrade are the need to significantly reduce the noise in the APDs and their rate of "spikes", and to make the calorimeter compatible with the higher Level 1 trigger rates and increased trigger complexity demanded by the high luminosity operation. The panel found these motivations very solid. Additional findings are that the project appears to be in a very good stage of advancement for the TDR phase and is well organized and managed by a competent and experienced team. Moreover, most studies done in the TDR cover a range of integrated luminosity up to 4500 fb 1, in excess of the 3000 fb 1 planned for the whole HL-LHC running period. This demonstrates that the proposed upgrades have adequate performance margins. The radiation models used in the TDR are accurately tuned on the data and show that radiation damage to the PbWO4 crystals has acceptable effects on the energy resolution, but the dark current and corresponding noise increase of the APDs is a serious problem. This is solved by reducing the APD operating temperature from 18 to 9 degrees C. Remarkably this is achieved retaining most of the current cooling system. The hadron barrel calorimeter scintillator is also degraded by radiation, but the corresponding light loss most likely will not be a problem, considering the higher quantum efficiency of the SiPM readout that will be implemented during the Phase-I upgrade. More studies are needed to reach a final decision on the need to replace the inner scintillator layers. The review panel recommends that this decision be made before the January 2018 UCG meeting. The two ASICs of this upgrade are the amplifier with fast shaping time (CATIA) and the ADC with 160 MHz sampling frequency (LiTE-DTU) to tag APD spikes. The

13 13 development of CATIA is advanced. Successful prototypes have been produced and all major decisions on the chip design have been taken. The simulation of the signal output reproduces very well the observations, thus giving confidence on the performance estimates. The LiTE-DTU chip is still being designed. The ADC cell is already well specified and will be bought from an external company. The remaining part of the chip still needs substantial work. The review panel recommends completing as soon as possible the studies needed to determine the specification of the functionality of this chip (size of the buffer FIFO, latency to deliver to BCP, compression scheme and BW contingency), preferably before the first submission. The power distribution board is based on the FEASTMP_CLP radiation hard DC-DC converter developed at CERN. This unit has wide use in the LHC experiment upgrades, but has shown problems recently in a specific application, so attention should be paid to the DC-DC converter tests. The new back-end boards, BCP, are critical to reach the latency and rate requirements of the upgraded Level 1 trigger. These boards are common to the EM and hadronic part of the barrel calorimeter and appear to satisfy the requirements, however the review panel recommends completing the study of the total latency achievable, in particular considering the inter-board communication and front-end data distribution latency. The details of the clock distribution system needed to achieve the planned 30 ps timing resolution are not available yet and should also be defined soon. In any case it is understood that a minor degradation of the timing resolution is not critical for the final detector performance. The time needed to rework and install super-modules is derived from experience, making the schedule realistic, but supervision and coordination with other systems needs to be better clarified. The review panel finds physics goals and technical implementation of the CMS barrel calorimeter upgrade well matching with the HL-LHC programme and recommends the TDR to proceed to the UCG review of the project. C. Report on the LHCC review of the CMS Phase-II Muon TDR Review panel: Florian Bauer, Alessandro Cardini, Silvia Dalla Torre, Dmitri Denisov, Hubert Kroha, Paul Newman, Mario Martinez-Perez (chair), Alessandro Polini, Osamu Sasaki, David Waters The committee reviewed the technical Design Report (TDR) of the CMS muon systems, which describes the foreseen detector upgrade in view of the HL-LHC period starting in Different elements of the read-out electronics for the muon chambers: Drift Tubes (DT), Cathode Strip Chambers (CSC) and Resistive Plate Chambers (RPC) need to be replaced in order to cope with the expected Level 1 trigger rate of 750 khz and the Level 1 trigger latency of 12.5 microseconds. The better timing capabilities of the new trigger electronics allows moving the trigger primitive logic to the back-end electronics, leading to a more versatile trigger logic, also aiming for an increased background rejection rate. The TDR proposes the construction of new muon chambers in the forward region. This includes two new Gas Electron Multiplier (GEM) detector sets and two improved RPC chamber sets. The CMS experiment carried out extensive longevity studies of the four different muon chamber technologies (DT, CSC, RPC, GEM), with the aim of determining whether their functionalities can be maintained up to the expected HL-LHC luminosity levels.

14 14 Except for the DT chambers, the other three muon chamber technologies did not show to date any sign of ageing. The committee welcomes the mitigation measures taken by the experiment and notes that this deterioration will only have a mild effect in the muon reconstruction. The proposed upgrade of the DT and CSC read-out electronics is mandatory, in order to maintain the detector performances over the entire HL-LHC period. The improved trigger capacities will preserve the physics program. For both, DT and CSC chambers, prototypes of upgrade read-out electronic cards either exist or are well advanced. The remaining R&D effort is small. In case of the DT, the experiment plans to instrument a whole sector with the new electronics already in 2019, which can be seen as the ultimate validation of the project. The proposed upgrade of the RPC s link system is well motivated to improve the timing resolution and to provide a higher bandwidth. The construction of new chambers in the pseudorapidity region promises to add redundancy to the muon reconstruction, to control the trigger rates at low p T, and to offer new functionality to trigger on exotic signals involving displaced muons, longlived particles, and heavy charged particles. Altogether, the committee is convinced that these potential improvements are worthwhile enhancements of the trigger. Two new sets of GEM chambers are proposed, ME0 and GE2/1, which will cover the pseudorapidity regions and , respectively. The technology proposed follows closely that of the already constructed GE1/1 chambers. The layout of the new chambers and the number of layers proposed are well motivated by space constrains, signal efficiency and background rejection. No signal deterioration has been observed so far during the ME0 aging studies. Similarly, the committee takes note of the positive results obtained on the discharge probability measurements carried out by the experiment. Two improved RPC chambers are proposed, RE3/1 and RE4/1, in the pseudorapidity region The new chambers feature a smaller gap and different charge threshold and resistivity to better handle the HL-LHC rates. In addition, a new 2D scheme for the readout of the strips is considered to improve the position resolution and to reduce the number of read-out channels. The committee takes note of the fact that two prototypes of different sizes have already been tested successfully. The design and test of the front-end electronic boards, based on Si-Ge technology, is still in progress. However, the read-out scheme has been validated in a small prototype. Concerning the strategy to reduce the emission of F-gases by CSC and RPC chambers, the CMS experiment presented a comprehensive plan. In addition, studies on alternate gas mixtures are progressing. Finally, the experiment presented the physics motivation for the new upgraded chambers in terms of a variety of physics channels involving multi-leptons in the final state, for which the presence of extended muon coverage would be beneficial. The LHCC panel would like to formulate the following recommendations: The committee considers that the DT ageing results are not completely understood and therefore recommends continuing the irradiation and the related studies. The DT project plans to instrument the detector with new electronics in This action is an example to be followed. The panel encourages the rest of the systems to do so wherever possible.

15 15 The fact that both GE2/1 and ME0 use (as much as possible) solutions introduced for GE1/1 is a good conservative attitude. The panel observed that there is limited feedback from the slices already installed in CMS and therefore this test cannot guide the construction, which is starting now. However, the panel considers this is an important test for CMS GEMs. Any information from this test will provide an important guidance on the GEM operation for CMS. The panel encourages the project to continue the GEM discharge studies under CMS conditions. This will allow the collaboration to integrate enough discharges such that definitive conclusions can be drawn on the robustness of the holes and the chambers against shorts. The panel consider that the proposed strategy to reduce F-gases in order to be compatible with the CERN requirements on greenhouse gases is viable. In parallel, studies on alternate gases and gas mixtures should be pursued, but the final choices must take into account the detector performance and longevity. Altogether, the committee finds the improved RPC project convincing, given also the already acquired experience in the detector construction and tests. The committee recommends following in depth the validation of the choices for the Si-Ge front-end electronics in the improved RPCs and the challenging prospect of the 2D readout, which need to comprise comprehensive tests on real-size detector prototypes. The committee finds that the physics case was not presented in enough detail and, in particular, it is not completely clear what the gain of the additional pseudorapidity coverage is in terms of physics output. We recommend CMS to continue to work on the physics motivation, and provide clear evidence of the separate impact of each muon upgrade and not just the combined impact of all upgrades taken together. The review committee finds the CMS muon system TDR technically sound and satisfying the specifications of the HL-LHC programme. The committee therefore approves the TDR (pending information of the individual upgrades on the physics reach) to proceed to the UCG review of the project. D. Report on the LHCC review of the ATLAS Phase-II LAr Calorimeter TDR Review panel: Phil Burrows, Claudia Cecchi (chair), Mauro Donega, Jean-Louis Faure, Peter Krizan, Fabienne Kunne, Martijn Mulders, Bob Tschirhart, Bill Wisniewski The TDR for the Phase-II upgrade of the Liquid Argon calorimeter has been submitted in September, and over a period of two months, the Liquid Argon Phase-II Calorimeter Upgrade Review Panel evaluated the scope of the upgrade project for the HL-LHC versus scientific reach and technical choices employed for the optimization of the design. The electronic upgrade of the detector is well justified in view of the High Luminosity running. The motivations of the upgrade have been clearly presented going from pileup mitigation, to radiation tolerance issues and compatibility with the Phase-I Trigger upgrade. The necessity for the LAr upgrade is well defined, even if many design choices have to be finalized. Some parts of the upgrade have, from the technical point of view, stringent requirements, but they have been shown to be feasible on the proper time scale.

16 16 Going into more details: Preamplifier and Shaping boards have been tested for two of the proposed technologies (65 nm and 130 nm ASICS). Some noise issues have been detected. ADC ASICS is the area presenting more difficulties. The baseline option, based on a custom 65 nm ADC, has been presented. A first version of the board has been tested, with some problems related to the loss of ENOB (equivalent number of bits) under investigation. The full prototype for the integrated Preamplifier/Shaper + ADC + optics is foreseen for 2021/2022. The HEC (Hadronic Endcap Calorimeter) needs a dedicated preamplifier/shaper board due to the opposite polarity signal and because of a different gain stage needed in one section. A new possible location for the LVPSs (Low Voltage Power Supply) has been discussed. The baseline option is at PP2 inside the toroid, where radiation is not an issue, but where a larger magnetic field is present, and longer cables are necessary. The off-detector electronics main board LASP (Liquid Argon Signal Processing), based on a monolithic blade ATCA (Advanced Technology Computing Architecture), shows a power requirement exceeding the specified upper limit of 400W/slot, this problem is under investigation. Detector performances have been discussed starting from the assumption of reaching, with the upgraded calorimeter, the same performance as in the run 2 data taking. The optimistic performance scenario, which assumes the constant term and the pileup noise can be significantly reduced, is able to achieve this goal, but the reconstruction algorithms available today have not yet demonstrated this performance. The review panel asked to explicitly highlight and quantify in the TDR the benefits arising from the availability of the full granularity and history of energy deposits in a bunch crossing for triggering and PU (pile-up) filtering. Based on the technical and scientific review, approval is given for the project to proceed to the UCG review. E. Report on the LHCC review of the ATLAS Phase-II Tile Calorimeter TDR Review panel: Phil Burrows, Claudia Cecchi (chair), Mauro Donega, Jean-Louis Faure, Peter Krizan, Fabienne Kunne, Martijn Mulders, Bob Tschirhart, Bill Wisniewski The TDR for the Phase-II Upgrade of the TileCal calorimeter has been submitted in September, and over a period of two months, the TileCal Phase-II Calorimeter Upgrade Review Panel evaluated the scope of the upgrade project for the HL-LHC versus scientific reach and technical choices employed for the optimization of the design. TileCal is the ATLAS Central Hadronic calorimeter made of scintillator tiles, read out by PMTs using Wavelength-shifting fibers (WLS). Motivations of the electronic upgrades, very well justified, are mainly based on the new ATLAS trigger and readout architecture (higher latency and trigger rates), radiation tolerances, and improvements of the reliability of the system by implementing redundancies on the new electronic boards.

17 17 Some topics have been deeply investigated as they have been recognized to be the weaker points of the complete upgrade chain. The scintillators will not be replaced and radiation damage could affect the performance of the detector. Starting from integrated doses over the 2016 data taking of ATLAS and from previous irradiation campaigns, an extrapolation of the dose at the end of HL-LHC has been presented. A 10% light loss has been estimated, but due to large systematic uncertainties, and because of differences in the material of the tiles placed in different regions of the detector, the review panel has asked for more studies in this respect. In particular a simulation of the detector response in the most exposed regions has been requested for an extreme aging scenario. The PMT response and absolute gain is continuously monitored by the laser system and can vary due to change in gain, opacity of the window, or variation in the quantum efficiency. Changes of the response as a function of integrated charge deposited has led to the decision of replacing only PMTs whose expected response loss will be greater than 20% at the end of HL-LHC. This amounts to a total of about 800 PMTs. In this context, the calibration system is crucial and new electronic control and a new hydraulic system are necessary for the upgrade. The Low Voltage Power Supplies (LVPS) are custom made devices with stringent size requirements due to the limited available space. The reliability of these devices is of fundamental importance, because they can only be accessed during longer breaks in LHC operations. Its operation relies on the ELMB++ interface, for which only a conceptual design is available at the moment. This currently represents the biggest uncertainty in the design of the device. The High Voltage Power Supplies (HVPS) positioning has been thoroughly discussed. The possibility to install them in a not irradiated and accessible environment is very appealing, but pairs of 100 m long cables would be required. At present only one company is able to supply the necessary multi-core cables and connectors for 32/48 pairs are not available. This baseline solution is therefore still under investigation and a backup solution is available. Although the detector performance has been presented for µ = 200, some of the physics results were only presented with a µ value of 40, and a trigger result demonstrating upgrade trigger performance was shown for µ = 50. In addition, many of the performance plots include results only for the central barrel, and do not include the extended barrel. The review panel has requested to see all performance and physics plots for µ = 200 and including the extended barrel. Based on the technical and scientific review, approval is given for the project to proceed to the UCG review.