Alignment of the CMS Muon System with Cosmic-Ray and Beam-Halo Muons

Abstract The CMS muon system has been aligned using cosmic-ray muons collected in 2008 and beam-halo muons from the 2008 LHC circulating beam tests. After alignment, the resolution of the most sensitive coordinate is 80 microns for the relative positions of superlayers in the same barrel chamber and 270 microns for the relative positions of endcap chambers in the same ring structure. The resolution on the position of the central barrel chambers relative to the tracker is comprised between two extreme estimates, 200 and 700 microns, provided by two complementary studies. With minor modifications, the alignment procedures can be applied using muons from LHC collisions, leading to additional significant improvements. * See Appendix A for the list of collaboration members arXiv:0911.4022v2 [physics.ins-det] 8 Feb 2010 FERMILAB-PUB-10-163-CMS Introduction The primary goal of the Compact Muon Solenoid (CMS) experiment [1] is to explore particle physics at the TeV energy scale exploiting the proton-proton collisions delivered by the Large Hadron Collider (LHC) The muon system consists of hundreds of independent tracking chambers mounted within the CMS magnetic field return yoke. Three technologies are employed: Drift Tube (DT) chambers on the five modular wheels of the barrel section, Cathode Strip Chambers (CSC) on the six endcap disks (illustrated in Figs. 1 and 2) and Resistive Plate Chambers (RPC) throughout. The DTs and CSCs are sufficiently precise to contribute to the momentum resolution of highmomentum muons (several hundred GeV/c) assuming that these chambers are well-aligned relative to the CMS tracker, a one-meter radius silicon strip and pixel detector. Between the tracker and the muon system are electromagnetic and hadronic calorimeters (ECAL and HCAL, respectively) for particle identification and energy measurement, as well as the solenoid coil for producing an operating magnetic field strength of 3.8 T in which to measure charged-particle momenta (all shown in The CMS collaboration is developing multiple techniques to align the DT and CSC chambers and their internal layers. Photogrammetry and in-situ measurement devices [3] provide realtime monitoring of potential chamber movements on short timescales and measurements of degrees of freedom to which tracks are only weakly sensitive. Track-based alignment, the subject of this paper, optimizes component positions for a given set of tracks, directly relating the active elements of the detectors traversed by the charged particles in a shared coordinate frame. Methods using tracks are employed both to align nearby components relative to one another and to align all muon chambers relative to the tracker. A challenge to track-based alignment in the CMS muon system is the presence of large quantities of material between the chambers. As a central design feature of the detector, 20-60 cm layers of steel are sandwiched between the chambers to concentrate the magnetic field and absorb beam-produced hadrons. Consequently, uncertainties in track trajectories become significant as muons propagate through the material, making it necessary to develop alignment procedures that are insensitive to scattering, even though typical deviations in the muon trajectories (3-8 mm) are large compared to the intrinsic spatial resolution (100-300 µm). Two types of approaches are presented in this paper: the relative alignment of nearby structures, which avoids extrapolation of tracks through material but does not relate distant coordinate frames to each other, and the alignment using tracks reconstructed in the tracker, which allows for a more sophisticated treatment of propagation effects by simplifying the interdependence of alignment parameters. This paper begins with a brief overview of the geometry of the muon system and conventions to be used thereafter (Section 2), followed by presentations of three alignment procedures: (a) internal alignment of layers within DT chambers using a combination of locally fitted track segments and survey measurements (Section 3); (b) alignment of groups of overlapping CSC chambers relative to one another, using only (c) alignment of each chamber relative to the tracker, using the tracks from the tracker, propagated to the muon system with a detailed map of the magnetic field and material distribution of CMS (Section 5). Procedure (c), above, completes the alignment, relating all local coordinate frames to a shared frame. Its performance is greatly improved by supplying internally aligned chambers from procedure (a), such that only rigid-body transformations of whole chambers need to be considered. Procedures (b) and (c) both align CSC chambers relative to one another, but in different ways: (b) does not need many tracks, only about 1000 per chamber, to achieve high precision, and (c) additionally links the chambers to the tracker. With the first LHC collisions, groups of CSCs will be interaligned using (b) and these rigidbody groups will be aligned relative to the tracker with (c). As more data become available, comparisons of results from (b) and (c) yield highly sensitive tests of systematic errors in (c). Although the ideal tracks for these procedures are muons from LHC collisions, this paper focuses on application of the procedures using currently available data, namely cosmic rays (a and c) and beam-halo muons from circulating LHC beam tests in September 2008 (b). In particular, (c) requires a magnetic field to select high-quality, high-momentum muons and concurrent operation of the tracker and muon systems. The CMS Collaboration conducted a monthlong data-taking exercise known as the Cosmic Run At Four Tesla (CRAFT) during OctoberNovember 2008, with the goal of commissioning the experiment for extended operation The formalism and results of each procedure are presented together. Details of the data transfer and the computing model which were used to implement these procedures are described in Ref. Geometry of the Muon System and Definitions Muon chambers are independent, modular track detectors, each containing 6-12 measurement layers, sufficient to determine the position and direction of a passing muon from the intersections of its trajectory with the layer planes ("hits"). The DT layers are oriented nearly perpendicular to lines radially projected from the beamline, and CSC layers are perpendicular to lines parallel with the beamline. Hits are initially expressed in a local coordinate frame (x, y, z) defined by the layers: z = 0 is the plane of the layer and x is the more precisely measured (or the only measured) of the two plane coordinates. On CSC layers, the most precise measurement is given by cathode strips, which fan radially from the beamline A semi-local coordinate system for the entire chamber is defined with x, y, and z axes nominally parallel to the layers' axes, but with a single origin. Within this common frame, the positions of hits from different layers can be related to each other and combined by a linear fit into segments with position (x,ȳ) and direction ( dx dz , dy dz ). The nominal x direction of every chamber is perpendicular to the beamline and radial projections from the beamline

Performance of the CMS hadron calorimeter with cosmic ray muons and LHC beam data

The CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked

Performance of the CMS Hadron Calorimeter with Cosmic Ray Muons and LHC Beam Data

The CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked

Materiality - The future of Swedish municipal sustainability reporting? : An exploratory & qualitative case study on municipal materiality analysis of Agenda-2030 key figures.

Studien visar att materialitetsanalys till viss del redan sker i kommunal verksamhet när de upprättar hållbarhetsredovisning. Däremot är denna i många fall mycket ostrukturerad och i vissa fall reflekterar inte kommunerna över att de prioriterar information. Materialitetsanalysen som utfördes av kommunerna visade dels att Agenda 2030-nyckeltalen som är ämnade att användas och implementeras i sin helhet i många fall är svårhanterlig med grund i kommunernas självstyre och unika sammanhang. Vidare visade studien att materialitetsanalysen kan vara användbar för att hitta de nyckeltal bland Agenda 2030-nyckeltalen som faktiskt är användbara för en specifik kommun. Detta eftersom vad som är att anse som materiellt eller inte till största del verkar vara helt beroende på varje enskild kommuns egen uppfattning. Vad som statuerar ett materiellt nyckeltal är alltså mycket beroende på varje enskild kommun. Däremot är det viktigt för kommunerna att nyckeltalet faktiskt går att arbeta med. Huruvida kommunen tidigare haft fram- eller motgångar med nyckeltalet tycks inte vara av någon större vikt. Matrisen låter också kommunerna reflektera kring och analysera nyckeltalen vilket kan utgöra ett gott komplement till nyckeltalen i hållbarhetsredovisningen. Kommunerna är bekanta med Agenda 2030 och vikten av att implementera denna i sin hållbarhetsredovisning. Materialitetsanalysen tillåter detta att ske systematiskt och är användbart för att ta hänsyn till varje kommuns förutsättningar. På så vis närmar sig kommunerna materiella hållbarhetsredovisningar med substans snarare än generella kopior av varandra med intetsägande nyckeltal. Detta innebär också att legitimitetsgapet mot samhället minskas. Explicit tryck i form av lagar för att driva på kommunal hållbarhetsredovisning medför risker. Detta kan bestå av att information tas med för att tillgodose ett lagkrav och inte för att det är materiellt. Materialitetsanalysen har en plats i kommunal hållbarhetsredovisning, detta är möjligt utan att tvinga dit den med lagar. Genom att belysa användbarheten och det värde en strukturerad analys av nyckeltal eller annan information ger hållbarhetsredovisningen kan också en norm bildas som främjar kvalitet framför inställsamhet.The study shows that materiality analysis to some extent already takes place in municipal activities when they prepare sustainability reports. However, in many cases this is unstructured and in some cases the municipalities do not reflect on the fact that they prioritize information. The materiality analysis carried out by the municipalities showed that the Agenda 2030 key figures that are intended to be used and implemented in their entirety are in many cases difficult to handle and not suitable as a national standard based on the municipalities' autonomy and unique contexts. Furthermore, the study showed that the materiality analysis can be useful for finding the key figures among the Agenda 2030 key figures that are useful for a specific municipality. This is because what is to be regarded as material or not largely seems to be dependent on each individual municipality's own perception. What constitutes a material key figure is thus highly dependent on each individual municipality. On the other hand, it is important for the municipalities that the key figure is operational. Whether the municipality has previously had successes or setbacks with the key figure does not seem to be of any major importance to if it is to be regarded material or not.The matrix also allows the municipalities to reflect on and analyze the key figures, which can be a good complement to the key figures in the sustainability report. The municipalities are familiar with Agenda 2030 and the importance of implementing this in their sustainability report. The materiality analysis allows this to take place systematically and is useful for considering the conditions of each municipality. In this way, the municipalities approach material sustainability reports with substance rather than general copies of each other with bland key figures. Doing this will help the municipal to reduce the legitimacy gap. Explicit pressure in the form of laws to push for municipal sustainability reporting entails risks. This may consist of information being disclosed to satisfy a legal requirement and not because it is material. The materiality analysis has a place in municipal sustainability reporting, and it can take this without being forced to do so by laws. By highlighting the usefulness and the value that a structured analysis of key figures or other information provides in the sustainability report, a norm can also be formed that promotes quality over conformity in municipal sustainability reporting

Performance of the CMS hadron calorimeter with cosmic ray muons and LHC beam data

This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOPThe CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked.This work is supported by FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTDS (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

Performance of the CMS hadron calorimeter with cosmic ray muons and LHC beam data

This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOPThe CMS Hadron Calorimeter in the barrel, endcap and forward regions is fully commissioned. Cosmic ray data were taken with and without magnetic field at the surface hall and after installation in the experimental hall, hundred meters underground. Various measurements were also performed during the few days of beam in the LHC in September 2008. Calibration parameters were extracted, and the energy response of the HCAL determined from test beam data has been checked.This work is supported by FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTDS (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)