1 DT Local Reconstruction on CRAFT data Plots for approval CMS- Run meeting, 26/6/09 U.Gasparini, INFN & Univ.Padova on behalf of DT community [ n.b.: more detailed information on the plots can be found on the draft PAS linked in the Twiki page: https: //twiki.cern.ch/twiki/bin/view/CMS/DTLocalRecoCRAFTPaper full info and complete analysis on muon CMS-NOTE also linked in the page, submitted to muon editorial board on 11/6/09 ]

2 Plots list : → Highlight most relevant results from DT Local Reco CRAFT analysis: 1) Resolution of rec.hits, after the muon arrival time determination (i.e. the best obtainable performance nearest to LHC condition…) 1.a single chamber distribution 1.b summary from all DT chambers 2) Reconstructed hit efficiency 3) Result from dedicated  -rays study 4) DT track segment distributions: hit multiplicity & track direction 5) Track segments efficiencies in all DT chambers 6) Bending vs p T (between consecutive chambers & using the full “lever-arm” MB4→MB1) & multiple scattering effect

3 1.a Hit residuals in single chamber Reconstructed hit residuals in a MB1 DT station of Wheel-2, with respect to the predicted position from the segment extrapolation, after the determination of the arrival time of the cosmic muon in the chamber. The MB1 stations of this wheel have in their sensitive volume the larger value of the residual magnetic field, which may worsen the chamber resolution. The red curves show the result of a double Gaussian fit to the distributions. The bulk of the distribution has a fitted dispersion  1 ≈220  m in the data (≈190  m in the MC simulation). The expected resolution from test-beam measurement is 200  m. The scatter plot on the right shows the residuals as a function of the local position in the DT cells.

4 Distribution of the fitted values of the reconstructed hit resolution in 246 DT chambers, after the determination of the cosmic muon arrival time in the chamber. The blue entries are from chambers in the vertical sectors of the Muon Barrel system, for which the incident angle of the muon track with respect to the normal direction to the chamber is on average very large. 1.b Hit residuals : summary from all DT chambers

5 Efficiency to have a reconstructed hit in a DT cell crossed by a cosmic muon as a function of the predicted muon local position in the cell for the four different Muon Barrel stations. The position of the anode wire is at x=0; the I-beams separating contigous cells are positioned at x= ± 2.1 cm. 2. Hit efficiency

6 Distribution of the difference between the distance to the cell anode wire of the first hit recorded in a cell and the distance of the extrapolated track position. The left-side tail in the plot is due to  -rays passing nearer to the wire than the crossing muon. The right-side tails originates from  -rays farer than the muon, when the muon hit goes undetected. The x- coordinate has been expanded to values larger than the cell size, to show the effect of  ray hits occurring in the cell neighbouring to the one in which there is the extrapolated prediction. Hits from  -ray affects the association efficiency of the muon hits to the track segments built in a chamber. The simulation agrees with the data at ~ 0.5 % level. 3. Effect of  -rays

7 Right: distribution of the reconstructed local angle with respect to the direction normal to the chamber, for reconstructed cosmic muon crossing the top sectors of the Muon Barrel system. Dots: data; full line histograms: simulation. The data-MC discrepancy in the left plots is due to a slight difference in the hit association efficiency, which sum-up independently for each of the 12 (8 for MB4 stations) layers. (see PAS note for more details) 4. Segments: hit multiplicity & track direction Left: multiplicity of associated hits to reconstructed segments in the four Muon Barrel stations of the top sector (sector 4) of CMS

8 Segment reconstruction efficiency in the r-  plane in the DT Muon Barrel chambers. Black: MB1, red: MB2, green: MB3, blue: MB4. Chambers from vertical sectors are not shown in the plots, due to lack of statistics of good quality tracks usable by the efficiency computation algorithm. Segment reconstruction efficiency in the r-  plane 5. Track segments efficiency

9 Bending angle differences between consecutive stations: MB1-MB2 (left) and MB2-MB3 (right), for muons of p T = (10±2) GeV/c (red histograms) and p T = (30±5) GeV/c (blue histograms). A gaussian fit to the p T = 30 GeV/c distribution is shown both for positive (points) and negative (full line) muons. The agreement of the fitted average values shows the accuracy of the alignment of the stations. The dispersion of the distribution is in agreement with expectations from multiple scattering.  6. Bending between consecutive stations

10 Bending angle differences between MB1 and MB4 stations. The selected p T interval for the p T = 200 GeV/c distribution is [150, 250] GeV/c. As seen from the distributions, the Standalone muon system is capable to correctly identify the muon charge of a 200 GeV muon in 80% of the cases, without any assumption on the primary vertex. Fitted dispersion of the distribution of the bending angle differences between consecutive stations as a function of the muon momentum. Full points:  +; open points:  -. The dashed and dashed-dotted lines show the expectations from the multiple scattering between MB1-MB2 and MB2-MB3 (or MB3-MB4 as well) respectively.

11 Back up

12 MC Reconstructed hit residuals in four DT stations with respect to the predicted position from the segment extrapolation, after the determination of the arrival time of the cosmic muon in the chamber. Left column: data; middle column: simulation. The scatter plots on the right show the residuals as a function of the local position in the DT cells.

13 NOT for approval