1. Matteo Volpi, Luca Fiorini Timing study with Muons at 90º from first beam PRELIMINARY STUDY (Barcelona) 1 Tile Timing Group meeting 17 September 2008

2. Outline  Beam and runs information.  Identification of Muon particles at 90º.  Study of the timing in all Tile Cal, in particular for :  Individual Partitions  Each sampling  Time difference inside a single cell  Conclusions 2

3. Beam and run  Run 87863: BPTX trigger data was analyzed. Run taken Wednesday 10 th Sep night around 22:00. Horizontal Muons at 90 º come from beam scraping with the collimator.  Beam 2 comes from the C-side, impinging in EBC partitions.  Ntuples are stored in castor :/castor/cern.ch/grid/atlas/tzero/prod1/perm/data08_1beammag/physics_B PTX  Analyzed data consist of about 4000 events. All the available ntuples (for this run) were analyzed.  Cell energy threshold at 300MeV (sum of both channels) was considered. While total energy in the Tile was asked to be less than 1TeV to avoid splash events. 3

4. Muon at 90º  The horizontal muons come from scraping interactions with the collimator. There are no splash events because the collimator was open and the typical total energy in TileCal is about 100 GeV. Splash events release energy above 1000 TeV.  Muon angle reconstruction plot on the right Horizontal, muons from the beam ATLANTIS DISPLAY Vertical, Cosmic muons 4

5. Tile energy plots. 5 We plot the mean energy of all the modules as a function of Z (mm) for different samples. EBCLBC LBAEBA Sample A EBCLBC LBA EBA Sample BC EBCLBC LBA EBA Sample D D4 A12 BC10

6. Timing study We would like to study the signal timing as a function of the Z position. We will treat all cells of a given type as one cell, integrating signals from all the modules in phi. In reconstruction, corrections include laser and WLS fiber lengths, standard LASER corrections (10Sept2008). D BC D0 BC5 y z D BC A Beam2 EBCLBC LBA EBA We applied two more corrections for the fact that particles are not coming from the IP, but from C-side at 90º. We took this into account for both A side and C. IP -Z/C+Z/C L/C Z/C correction: We would like to eliminate the z-dependence resulting from TOF We correct for TOF dependence along z calculating and correcting for time it takes for muon to fly from a given cell to the z=0 point. Z/C +TOF(IP) corrections: We apply the previous correction and the TOF it takes for muon to fly from IP to a given cell. 6

7. Timing study: no corrections applied yet Time as a function of the Z position. We sum all cells of a given type in phi for all the modules. EBCLBCLBA EBA We observe a timing discontinuity between the partitions and a timing trend as a function of Z. The later is due to TOF. The slope is in agreement with the fact that the beam is not coming from the interaction point (IP), but from the C-side. Sample A EBCLBCLBA EBA Sample BC EBCLBCLBAEBA Sample D 7

8. Timing study: first, Z/C correction applied Timing as a function of the Z position when applied the Z/C correction. EBCLBCLBA EBA Quite flat response for each partitions is observed. Also observed time difference between partitions, mainly for LBC. Also the general baseline is about - 10nsec, likely due to the trigger not coming at t0. Sample A EBCLBCLBA EBA Sample BC EBCLBCLBA EBA Sample D 8

9. Timing study: Z+TOF(IP) corrections Time as a function of the Z position after we applied the Z+TOF(IP) corrections. Nothing new or informative comes from these corrections, not until the interactions will come from IP EBCLBCLBA EBA Sample A EBCLBCLBA EBA Sample BC EBCLBCLBA EBA Sample D 9

10. Time Vs Modules (Phi) for each partitions 10 Not corrections applied EBC  The timing is about uniform for the drawers of the same partition.  8 Modules in EBC are shifted by about 7 ns. Modules in two different sectors, LASER data shows nothing unusual. Remaining Open question. LBC LBA EBA 8 modules had Shift of about 7 ns RMS=5.1nsRMS=1.5ns RMS=2.2ns RMS=1.5ns

11. Time Semi Difference inside a cell 11 We find a very small semi time difference between the 2 PMTs signals of the cells The semi difference time is not more than 1ns. Effect of the partition timing difference is observable for cell D0 D0 Sample A Sample BC Sample D We confirm the good calibration with the laser system.

12. Conclusion  The goal is to have TileCal at ±2ns from the T0 of the trigger to optimize the performance of OptFilt.  The start is quite good. We observe a timing discontinuity between the partition at he level of 10 ns to be fixed.  For each partition we observe a timing trend as a function of Z at the level of 4 ns (worst case) instead of 0.  The analysis is preliminary and the next step is to study in detail the delay of each digitizer. 12