Commissioning of the MUON Spectrometers in ATLAS and CMS Differences and similarities between the MUON Spectrometer of ATLAS and CMS. Status of the ATLAS-MUON installation and Commissioning. Status of the CMS-MUON installation and Commissioning. General comments on readiness. Conclusions.

Different Philosophies between the 2 large experiments ATLAS Philosophy Trigger and perform precise measurements of HE muons in the spectrometer, correct for losses in the calorimeters and improve measurement using inner detector for LE muons. Main emphasis on low mass Spectrometer and high coverage (eta<2.7) CMS Philosophy Main emphasis of the spectrometer is on the trigger (2 different and complementary systems), while momentum measurement is mainly based on ID tracking in a high magnetic field (4 Tesla). Main emphasis is on precise Pt measurements for rapidity <1.8.

Different Philosophies lead also to different importance of the ID measurement, and of the rapidity behavior ATLAS CMS While in ATLAS, the MUON Spectrometer determines the P resolution for P>20GeV/c, in CMS the resolution is dominated by the ID. In ATLAS, the MUON Spectrometer resolution is dominated by the alignment and the Drift Tubes resolution

Due to the magnetic field, the 2 experiments measure different things: ATLAS=P, CMS=Pt In the low rapidity region CMS has a superior P resolution (mainly due to the high Solenoidal field), while at high rapidity, is the ATLAS spectrometer, with its toroidal field that has the better resolution. At high momenta, it is the L**2 in BL**2 in the MUON Spectrometers,that allows to recuperate the P resolution. Due to the relative importance of the MUON Spectrometer in ATLAS, its performance depend critically on: Alignment Good field knowledge (due to non-uniformity) Good Drift Tubes Calibration

Status of the ATLAS-MUON installation and Commissioning All barrel chambers have been installed, but not all are at the final position. Except for 40% of the EO chambers to be installed in May, all End-Cap chambers have been installed. The so called staged EE chambers have been constructed (thanks to Protvino) and their installation is foreseen after the shut-down.

Know the magnetic field; i. e Know the magnetic field; i.e. know where the magnets are to within a couple of mm in a non-uniform field Magnet was powered in November 06 and its field measured and reconstructed with probes installed in the chambers.

4 coils were reconstructed in shape with very small residuals If you know (alignment) where the chambers are, the field reconstruction works.

Where are the chambers and how much do they deform 6,000 images in the barrel and 6,000 in the end-caps. System allows to measure: Translations in X-Y Rotation magnification

Status of the barrel alignment and its Performance Type Total Working Broken Bad because MDT not in place Projective 117 85 12 20 Axial 1035 998 10 27 Praxial 2006 1938 6 56 Reference 256 232 4 CCC 260 234 16 BIR/BIM 32 Inplane 2110 2064 8 38 5816 5589 50 177 Measuring 10 to 100 micron changes, due to magnet heaters being turned-on.

Status of End-Cap Alignment Main reference system is the alignment bars. Since Wheels are not in final longitudinal place, no projective element has been used, however they have been used to align and follow the chambers in the azimuthal component in the Small and Big Wheels.

Operation of the End-Cap Alignment The alignment system has been used to correct the psition of the chambers in the Small and Big MUON Wheels. All its elements (except the projective part) are working and the chamber positions are being monitored continuosly

Status of Barrel MDT Commissioning Sectors from 3 to 8 Commissioned with Cosmic rays. Sectors 1-2 & 9-10 noise test (missing HV-PS’s). Sectors 11-12 under test. List of remaining problems % Dead tubes less than 1‰ Some noisy wires mainly on BOS # HV trips: 2 # Gas leaks: 18 yet unfixed leaks

Status of MDT-DCS Commissioning HV/LV +monitoring of FE electronics T and V . Alignment Gas B-field T-sensors Initialization

Status of MDT Commissioning in the End-Caps Side C LV+HV completed Temporary Gas connections: now moving to final Operated under Cosmic rays in common runs. 3 Chambers excluded from read-out for DAQ/Fiber problems 3 Multilayers with HV Problems Side A LV fully equipped HV bottom half Temporary Gas connections on bottom half: now moving to final Bottom half operated under Cosmic rays in common runs. 1 FE card excluded from read-out 3% of all chambers with some problem: need access between wheels to solve them.

Status of MDT-CSC Commissioning in the End Caps: Small Wheels Small Wheels fully commissioned outside pit. All 3 systems have ~0.05% of non-working channels. Transport through CERN has been very impressive. No broken wires and no gas leaks after descend to ATLAS pit. Second Wheel went down last Friday.

Installation and Commissioning of the EO-MDT chambers All EOS chambers have been installed and commissioning has started. 9 out of the 16 mechanical Large sectors have been installed, with the corresponding alignment bars (major effort to have all components at CERN in mid December). 4 out of 16 Large sectors have been installed with all their chambers. Following ATLAS closing, remaining 7 mechanical Large sectors to be installed (2 per day) and the remaining 12 chamber sectors (1 sector per day). There will be very little time for commissioning of the large sectors.

Read out of MDT and Calibration All ROD’s have been installed and tested. Data taking is performed from the control room. During December run, calibration data stream has become operational at LV2 (only data in ROI send to TIER2 centers). Calibration performed quasi on-line, with very encouraging results. Many problems, but first results are very encouraging.

Status of RPC Commissioning Cabling of HV/LV Racks on HS 75% of the work completed Missing Sectors 11, 12, 13, 14 Should be finished within 1 month (depending on CAEN delivery) Cable test and connection to Chambers Sectors 1-8 completely cabled Working on 9 and 10 Work pace: 2 Weeks/sector Will increase having a second team working in parallel

Status of RPC Commissioning Many gas leaks found due to broken gas inlets (80, 43 of them already repaired). All commissioning performed with gas circulating in open mode. Soon to move to recycle mode, but various issues need yet to be clarified. To complete RPC commissioning by mid June, a 2 step procedure has been started, with the first step being: Testing all cable connections and their correspondence checked DCS working and electronic threshold optimization HV checked and debugged Gas Checked and debugged Trigger electronics and front end electronics debugged and timed. The remaining problems are left to a second pass. With this procedure, expect to achieve 1 sector/2 weeks.

Status of RPC Commissioning Sectors 1-6 have been commissioned with cosmics, while 7-8 are being completed now. The number of problems left is small: Dead strips= 0.2% Disconnected gaps for HV problems 0.6% Disconnected gaps for Gas Leak 0.2% Noisy channels: few units Average Noise 0.4 Hz/cm2 MDT -RPC Correlation  ~ 9 mm Distance between MDT track and RPC cluster

Status of TGC Commissioning All sectors tested with cosmics either in surface or in the pit: Bad Channels ≈ 10-4 6/24 sectors operated during common runs CAEN Power supply and crates delivery have been the main bottleneck Installing mini-crates and AC/DC converters Difficult access for TGC3: Need BW away from EO for ½ of the sectors (2 Weeks of work in parallel with EO installation). TGC currently operated with CO2 in a temporary Gas distribution System - Need urgently to move to Final Gas System: Distribution racks (final connection to racks being performed now) Final mixture (n-pentane): problems have been found with the heaters used to performed the mixture. Expect to be solved in April. A C

Status of TGC Commissioning Both trigger and readout paths are operational. All readout and trigger electronics are installed. Trigger Latency measured: 86-90 clk C09 Previous Current Next 32/30132 events

Remaining problems Although the CAEN delivery problem is under control (last delivery in April), there are still some problems with failure rates. Cruising speed to commission the RPC system should be increased (doubled) in order to complete the first pass by end of May. One needs to move soon to a gas recirculation system for RPC’s, and in particular optimize the various filters. One needs to start the commissioning of the TGC gas system with CO2 and ensure that the final system will be available in May. The available time to complete the power supplies installation for the Low-Pt trigger in the TGC’s (TGC2-3) is very tight (2 weeks in parallel to EO installation). The time for the completion of the EOL installation is very tight (2 weeks), which will not allow much time for full commissioning.

The CMS muon system Barrel: Drift Tubes (DT) (4 layers) Resistive Plate Chambers (RPC) (6 layers) End caps: Cathode Strip Chambers (CSC) (4 layers) Resistive Plate Chambers (RPC) (4 layers)

CMS muon detectors DT CSC RPC

Barrel wheel

End cap disks with CSC’s 22 Jan 08

A Measurement ! Magnet Test and Cosmic Challenge MTCC: on the Surface Cosmic muons momentum distribution) MTCC: on the Surface Cosmic muons charge ratio (+/-) (Awaiting definitive alignment constants)

Commissioning DT system in UX YB0 Entrance Angles

Examples of Performance: DT Analysis of Drift-Tube commissioning data for Wheel 0, sector 10. Resolution ~ 300m from cosmic muons

Airshower triggered by RPC: DT segments reconstructed at HLT November Global Run 100% of HB 50% of HF, HE 20% of DT, HO 10% of barrel RPC, EB (for a few days) 0.04% of strip tracker (6 module RIB prototype) Synchronized 10M events logged Small % of End-Caps detectors took part underground, due to Power Supplies delivery Airshower triggered by RPC: DT segments reconstructed at HLT

General Comments on readiness Both MUON systems have been delayed in their commissioning by the late arrival of CAEN Power Supplies, which should be completed by May-08. In the case of ATLAS, being the MUON’s the outermost detector, their installation and their services were always the last one. The RPC gas recirculation system has encountered many problems, not all yet solved, which have slow down the commissioning due to the high cost of gas.

Conclusions The MUON systems of the 2 large LHC experiments, with 1,000’s of M**2 detectors and over 1M readout channels each, to measure the passage of the particles with resolutions of less than 100microns, constitute one of the major technological defies ever achieved. The two experiments are well advanced in their commissioning aspects, and the fact that one is already taking cosmic data from their respective control room, a few months before beam is a very good sign. Albeit many problems, the two large LHC experiments will be able to take MUON data with a large part of their systems at the beginning of the LHC beam.