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AMS01 Ions analysis status

AMS01 Ions analysis status. AMS - 01 Data: Z>2 statistics. Preselection Z>1 on AMSdata-Ntuples at Cern A total of 251688 heavy ions have been identified Li, Be, B, C, N, O, F. N. Tomassetti. Perugia, Marzo 2008. Local zenith. AMS attitude. Attitude angle. Data Periods.

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AMS01 Ions analysis status

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  1. AMS01 Ions analysis status E.Fiandrini, N. Tomassetti

  2. AMS-01 Data: Z>2 statistics • Preselection Z>1 on AMSdata-Ntuples at Cern • A total of 251688 heavy ions have been identified • Li, Be, B, C, N, O, F E.Fiandrini, N. Tomassetti N. Tomassetti Perugia, Marzo 2008

  3. Local zenith AMS attitude Attitude angle Data Periods • 5 Periods of data taking in 10 days: • pre- and Mir docking: no fixed orientation wrt local zenith • 0 degrees wrt local zenith • 20 degrees " " • 45 degress " " • 180 degrees " " 0 20 45 180 Mir Docking Attitude (deg) Pre Mir Docking Unix Time (sec) E.Fiandrini, N. Tomassetti

  4. Because of Shuttle material only particles entering form top of AMS01 are useful for analysis  Particles with (signed) <0 are discarded Mostly acquired during 180 degrees period, when AMS faced Earth Very few particles with >0 during 180 attitude period (likely secondaries) Local AMS Z axis <0 (upgoing) top 0 20 45 180 Mir Docking Attitude (deg) Pre Mir Docking bottom >0 (downgoing) Unix Time (sec) E.Fiandrini, N. Tomassetti

  5. AMS-01 STS-91 Flight • AMS-01 performed a 10 day Shuttle flight in June 1998 • Variable orientation, 0°, 20°, 45° • Time period exposure 180 hours • 100 million events E.Fiandrini, N. Tomassetti N. Tomassetti Perugia, Marzo 2008

  6. Selection analysis 1) Event cuts: - Paddle 10 in Plane 3 of TOF cannot be used for time of flight - Inefficient reconstruction of tracker K side (FalseTOFX) - Tracker Rec Pattern - Quality of the track fit (2fast, 2NoMS -  – Rigidity Match - Ratios of Rigidity to Half Rigidities - Rigidity resolution 2) Cluster quality cuts - Occupancy level (discard hot and dead strips) - Morphology of clusters - Cluster S/N - Minimum Seed charge - "Isolated" clusters E.Fiandrini, N. Tomassetti

  7. The initial sample is made of events satisfying the LVL3 trigger, i.e. NO ACC HITS The initial statistics is 196596 events with >0 As sample of mis-measured events, the fraction of events with wrong sign rigidity (R<0) has been used to tune cuts Then: 180123 events with R>0 16473 events with R<0 (9,1% of total sample) E.Fiandrini, N. Tomassetti

  8. Bad TOF+FalseTOFX Total R>0 R<0 171539 events satisfy the cut (95.3)% Good BAD 14262 background events survive the cut (86.6%) R>0 R<0 BAD Good E.Fiandrini, N. Tomassetti

  9. In the following, all distributions will be shown as last cut E.Fiandrini, N. Tomassetti

  10. –R match Well measured events lie around the curve 1/|| Mismeasured events cluster at low R and 1/» 1 Blue and Red Lines describe the applied cuts R (GV) E.Fiandrini, N. Tomassetti

  11. First 1 2 3 4 5 Last 6 Span = Last Layer Used– First Layer Used E.Fiandrini, N. Tomassetti

  12. Track Pattern Normalized distributions It looks like if reco algorithms prefer some patterns to get wrong rigidity sign NB: No wrong sign rigidity when using 6 hits tracks E.Fiandrini, N. Tomassetti

  13. 1 2 3 4 5 6 If the number of consecutive planes is small, it is possible that an interaction (eg large angle MS) in between 2 hit planes is overlooked E.Fiandrini, N. Tomassetti

  14. Track Fit Quality • Fast non linear fit used four times in the following modes: • In the default algorithm, all hits are used to determine the track parameters, R and fast • The same algorithm is applied to the 1st and 2nd half of the track, evaluating R1 and R2 • Multiple scattering is neglected in a 4th iteration which yields diffrenet results especially in the low rigidity region. The resulting parameters are RnoMS and fast E.Fiandrini, N. Tomassetti

  15. Half Rigidities To reject events which underwent to important nuclear scattering R/R1 and R/R2 are used Loose cut on R/R1 0<R/R1<2 Tighter cut on R/R2 0.5<R/R2<2 to take into account the MS integrated effect along the trajectory path E.Fiandrini, N. Tomassetti

  16. 2's Fast<40 Both peaked at low values with an extended tail due to tracker ineffic., misalignment, noise, -rays production and the neglect of MS in the 2noMS variable noMS<200 E.Fiandrini, N. Tomassetti

  17. Rigidity Resolution Require a good rigidity measurement R/R <0.3 E.Fiandrini, N. Tomassetti

  18. Cluster Selection E.Fiandrini, N. Tomassetti

  19. X side  dependence corrected by a 4th order polinomial Chip gain dependence taken into account: effect of few percent (forgot to put the plots...) E.Fiandrini, N. Tomassetti

  20. Occupancy • Many strips with low occupancy • Some strips with high occupancy Few events (757/251891) have "bad format", ie contain clusters with strip channels > 1024! E.Fiandrini, N. Tomassetti

  21. Occupancy Relative Occupancy Fraction = (Channel Hits)/(Average Ladder Channel Hits) An Y channel is declared DEAD if ROF<0.4 (10.5 %) An Y cahnnel is declared HOT if ROF>2 (1.6 %) An X channel is declared DEAD if ROF<0.61 (17.5%) An X cahnnel is declared HOT if ROF>2 (1%) Well described by a gaussian with peak @1 and ¼ 0.2 E.Fiandrini, N. Tomassetti

  22. Since X side has falseTOFX inefficiency, an higher number of hot and noisy strips and is not relevant for curvature measurement, only the Y side has been used for cluster selection E.Fiandrini, N. Tomassetti

  23. Occupancy • A cluster is declared BAD if: • It contains a hot strip • It contains or is adjacent to a dead strip • it is within 1 channel length from edges ¼15% of Y cluster removed, ¼19% of X clusters removed E.Fiandrini, N. Tomassetti

  24. D Seed 1 Seed 2 First Clus Chan: Seed -2 Last Clus Chan: Seed +2 Distance between track cluster and cluster on same ladder A fraction of track clusters have another cluster attached or within few channel lenghts Max Clus Length is 5: Seed § 2 channels If real cluster legth exceeds 5, two adjacent cluster are created  need to re-clusterize E.Fiandrini, N. Tomassetti

  25. All Charge Residuals after cuts E.Fiandrini, N. Tomassetti

  26. Nclose = 0 A close cluster is a cluster separated by at least 1 channel and within Nmax channels from track cluster with NmaxY = 20 (§ 2 mm) Nmaxx = 10 (§ 2 mm) E.Fiandrini, N. Tomassetti

  27. Minimum (S/N)cl/Z2 (S/N)clZ2 > 4 • A guess on the quality of cluster of the hit is S/N • To make it charge independent (to first approx), normalize to rec charge number Z2 • Low (S/N)/Z2 indicate that possibly a noise cluster (or a part of larger cluster) has been assigned to track hit to build the coordinate E.Fiandrini, N. Tomassetti

  28. Cluster Length Most of clusters have length >3 With (mostly not fully relatistic) heavy ions with inclined trajectories is unlikely to have "short" clusters due to high charge deposit  Lengths <3 are indicative that a cluster which is the "tail" of a larger cluster was used in track fitting E.Fiandrini, N. Tomassetti

  29. Seed 2nd Max Seed 2nd Max Good cluster Bad cluster Cluster morphology | # Seed – # 2nd Max| · 1 Indication either of channel inefficiency (but not dead) or a possible -ray emission or nuclear fragmentation E.Fiandrini, N. Tomassetti

  30. Cluster Quality A cluster must satisfy all the previous cuts The event is declared good if at least 3 good clustrs are left E.Fiandrini, N. Tomassetti

  31. Cluster amplitudes after cuts E.Fiandrini, N. Tomassetti

  32. Square root of Average charge cluster adc adc Well fitted by 6 gaussians adc adc E.Fiandrini, N. Tomassetti adc adc

  33. Final sample (all charges) No events below 0.6 GV/c and above »70 GV/c left after selection R (GV/c) E.Fiandrini, N. Tomassetti

  34. Efficiencies Li Be Efficiency and flux evaluated for R>0.8 GV/c and R< 40 GV/c for limited statistics Log10(R) Log10(R) B C Log10(R) Log10(R) O N Log10(R) F Log10(R) Log10(R) E.Fiandrini, N. Tomassetti

  35. Rates Li Be >0.9 0.8<<0.9 0.7<<0.8 0.4<<0.7 B C <0.4 Right now the rates are calculated only for 0, 20 and 45 degrees periods O N Log E.Fiandrini, N. Tomassetti

  36. B/C ratio Log10(R) E.Fiandrini, N. Tomassetti

  37. Peak vs Pcharge in different beta bins E.Fiandrini, N. Tomassetti

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