1. Giovanni Petri University of Pisa/INFN Pisa/SLAC 29 August 2005 Study of TEM errors

2. 1.Can the LAT produce errors during data acquisition? –Choice of Error Type –How often does it happen? –Under what condition does it happen –Under what condition does it happen ? 2.What is the impact of these Errors on-orbit? Lost in Translation Introduction

3. How does it happen??? Tracker Calorimeter Tower Electronic Module Tower Subsystems Overview Glt Electronics Module TEM collects them, checks 3-in-a- row and (if TKR triggers) sends it to GEM GEM opens window on first trigger type and waits for others to arrive (Coincidence Window) After few ticks CW closes and TAM is sent back to the readout controller to start readout Readout starts from the BOTTOM!!! A particle hits the tower Trigger Primitives fired by subsystems

4. TEM CC FIFO Error –1 cable stores up to 128 hits –8 cables per Tower –128 x 8 = 1024 hits per tower Other Buffer Limits: –Readout controller: max of 64 hits allowed –Plane: max of 128 hits allowed (64x2) –How: Cosmic showers e.g. –Let’s call an event with FIFO error “BAD” Cables Si Planes Tracker Sketch FIFO Definition

5. How Often? Statistics Summary 6 Towers Runs: # Runs: 62 (B type) # Register Config: 3 # Events: 15,346,394 # Bad Events: 1760 8 Towers Runs: # Runs: 81 (B type) # Register Config: 3 # Events: 22,391,000 # Bad Events: 2900 2 Towers Runs: # Runs: 48 (all!!) # Register Config: 19 # Events: 9,564,116 # Bad Events: 915 4 Towers Runs: # Runs: 31 (B type) # Register Config: 2 # Events: 1,084,655 # Bad Events: 93

6. Error Rates for B type Runs: 2 Towers: 7.4 · 10 -5 »B2: 8.3 · 10 -5 »B10: 7.1 · 10 -5 »B13: 7.5 · 10 -5 4 Towers: 8.66 · 10 -5 »B10: 8.40 · 10 -5 »B13: 8.79 · 10 -5 6 Towers: 1.13 · 10 -4 »B2: 1,15 · 10 -4 »B10: 1.09 · 10 -4 »B13: 1.20 · 10 -4 Among 2 Towers runs (not B type) –135002057-2103 –Single RC Right/Left »ER 2 · 10 -4 –135002166-2168 –Single RC R/L + Overlay 10 KHz »2,1/2,7 · 10 -4 –135002107 –Only Cal Trigger »5.9· 10 -3 How Often? Bad Events Rates What’s that? 2 orders of magnitude? Can we explain this? B2: Flight Settings B10: Cal 4 range B13: Zero Suppression OFF

7. Cables Planes RC on one side only: Max hits per plane is 64 RC try to read its entire plane! –An event that had 70 hits on a plane now saturates the plane! –It’s easier to have more hits on the same Cable!! Single RC ER Anomaly The factor 2-3 of difference is not so strange!! »This can be a first order explanation!! 3040 70

8. 1.CAL LE has more probability to be triggered by high energy events. 2.Energetic events have more probably high hits occupancy 3.Is it enough to explain the big difference? No other runs to compare rates!! Cal Only Trigger Anomaly ER = 5.9· 10 -3 The run has few events: 3000 instead of 300,000! NOT STRANGE!! Do you believe me? BUT... We can REPRODUCE that!!! Cut on CAL LE triggered Events!! What comes out is ER ~ 3.6 · 10 -3 !!! # Events: 3048 # Bad Events:18

9. You clearly recognize Eduardo when he’s been working late in the night When do Bad Events happen to good people? Which primitive triggers are there? »GemConditionsWord When do they arrive? »Are there temporal patterns? Is a Bad Event influenced by the previous one? »GemDeltaEventTime How are hits distributed? Are there odd configurations? You understand “odd” later »Stay tuned… Trigger Hits Occupancy

10. Trigger Topology GemConditionsWord: –Tells which primitive triggers arrived in the CW –Possible combinations: TKR (2) CAL LE (4) CAL HE (8) TKR + CAL LE (6) TKR + CAL HE (10) CAL LE + CAL HE (12) TKR + both CAL (14) B10 runs 2 towers Trigger Types Good Bad No 8s, 10s, 12s: This was expected!! Bad Events are “big”! –High Multiplicity

11. We expect that the TKR often arrives first! –TKR is big: high probability to trigger first Trigger Topology Trigger Primitives Arrival Times Chained B10 runs 2 towers TKR arrives soon!!! This is no surprise! ~80% The number of events goes down very rapidly!! Ticks 1 tick = 50 ns

12. Trigger Topology Trigger Primitives Timing CAL LE should open when TKR is not the first: »CAL LE is faster than CAL HE! »# Times CAL LE opens CW is consistent!! This is odd!! Explanation??? Just a case? Remember Log Scale Ticks 3 events

13. Trigger Topology Temporal Correlations The time between a Bad Event and the previous one is long!! Good Bad The minimum Delta Time is longer than for Good events Just low statistics probably 1000 ticks 2000 ticks

14. Hits Occupancy Event Display Cliffhanger Salt and Pepper No Cal Hits only in upper layers “Recognizable track” Cal lit up where “track” arrives Hits everywhere Drittoni (big straight) 50% 25% 20%

15. Hits Occupancy 1.Qualitatively: you can distinguish the single layers, one by one, from the other. 2.Hits are only on the borders and are uniformely distributed. Evt 135002052-268476 Cables Readout Controllers Characteristic signature: everything’s FULL Puffettae

16. Puffettae There is a Puffetta in 6 Towers Runs too!! None found in 4 and 8 towers runs It looks exactly the same as the 2 towers one. 135004119-115100

17. Puffettae Dumps Looking at Dumps you find this: 0040 (hex) = 64 (dec) For every single RC above 1 on every CC. 2 8 1 LDF Dump file

18. Puffettae Data EventIDCalEneSum (MeV) Gem Word TkrCal LeCal HeDelta Time Gem Discarded 2 Towers 6 Towers There is no obvious hint of electronics gone wild!! Are these energies consistent with showers that big? Delta Times are long GemDiscarded seems reasonable (TOT very long) 1150991172231 102213607 11510035130314302470433607 115101262031 568183615 26847502031 466001367 2684768776614209655351367 26847702031 655351367

19. From Russia with… CAL! Too good to be true!!!! CAL says: “Everything normal pal!! Just big shower!!” Layers Energy (GeV) Asimmetry

20. LAT 6 towers 1.At sea level we see 10% of E p (Tune) 2.From graph 10 6 e - at sealevel (Tune) High multiplicity shower of 10 MeV e - 350 GeV measured All strips hit ⇒ 10 4 particles in 6 towers 350GeV/10000 = 35 MeV per particle 10 MeV particles don’t go through the TKR!! p For Ep=10 5 GeV (for consistency with the observed rate)

21. NO PUFFETTAE!! What happens on-orbit? There will be high-energy photons!! –Will these be high multiplicity events in the TKR? Let’s see what MC has to say about this!! Used photons coming from 45°-60° from the vertical axis Energy of 300 GeV Searching for behaviours like those observed in FIFO errors Backsplash? Total # MC photons 10 5 # Triggered Events 13006 #1 Towers Saturated: 38 300 GeV

23. Conclusions 1.The TKR works (poor me…) too well!! FIFO errors are no mistery anymore!! We know how to characterize AND understand them! –Rates are low: 1 (lonely) bad guy every 100 thousands!!!! –No influence on other events!!! 2.Bad Events are consistent with showers 3.High energy photons MC needs to be further studied –What about reducing lower layers buffer bandwidth to improve recon??

24. TACK Favorite saying: “I told you NOT my Camaro!! Now I’m angry…” Anders Borgland High energy Muon shower Eduardo do Couto e Silva Favorite saying: THIS IS TOO COOL!!!! HIM …trying to sneak home early… 1 AM… ME

25. BACKUP SLIDES …hic sunt leones…

26. EM Showers To be in the core area 3.14x420 2 =5.5x10 5 m 2 Freq = 2 x 10 -2 /s (~4-8 e/ m 2 ) To be in a 10 times denser area Freq ~ 2 x 10 -3 /s (~40-80 e/ m 2 ) To be in a 100 times denser area Freq ~ 2 x 10 -4 /s (~400-800 e/ m 2 ) To be in the core area 3.14x420 2 =5.5x10 5 m 2 Freq = 2 x 10 -4 /s (~40-80 e/ m 2 ) To be in a 10 times denser area Freq ~ 2 x 10 -5 /s (~400-800 e/ m 2 ) To be in a 100 times denser area Freq ~ 2 x 10 -6 /s (~4000-8000 e/ m 2 ) 10 7 Gev 10 8 Gev Need ~ 10 4 particles Total Energy ~ 350 GeV ~ 35 MeV Let’s say initial total energy was 10 5 -10 6 GeV We get at sealevel ~ 10 6 particles Assume for such initial energy, Freq ~ 2 x 10 -4 /s The 6 tower data acquisition lasted ~ 1 day ~ 16 Puffettae (or like)

27. Saturated tower: > 64 hits on each of the 4 bottom planes (both on x and y) Is this consistent with Showers? # Saturated Towers 12345678 6 Towers Data 7863112// 8 Towers Data 14511332104 91 169 =

28. V.H.E. Cosmic Rays and Air Shower Profile Take a proton with E p =10 7 GeV=10 16 eV Flux is 6.8/E 1.75 per cm2, second, steradian and bin-width of E where E= 10 7 GeV. We then get, Flux(E p =10 7 GeV)=3.8x10 -12 /cm 2 /s/sr for a bin-width of 10 7 GeV Step 1) Read off the flux of 10 7 GeV proton rate Step 2) Estimate the lateral distr. of particles Distance from the core is about 14X = 420m Normalized density of 10 -2 /X 2 = 10 -2 /(30m) 2 X=Rad. length of atmosphere=36g/cm 2 =30m Observation proton

29. Electron Component in Hadronic Shower N e /E 0 [1/GeV] Step 3) Estimate the number of electrons in a 10 7 GeV air shower at sea level. These are shower measured profiles for 10 5 GeV proton. Since there is no measurement for 10 7 GeV, we assume one sample profile from these. This gives highest number of electrons at sea level: use as an upper limit. For a 10 7 GeV proton we get Number of e = 0.2x10 7 = 2x10 6

30. Electrons and Gammas within an EM Shower Step 4) Calculate electron density per m 2 From Step 3) Total number of electrons = 2x10 6 electrons From Step 2) Assume they are distributed uniformly in r=14X=420m of the core. Electron density is then 1.8x10 -6 (1/m 2 ) times 2x10 6 = 3.6/m 2 Uncertainty: a) Fluctuation: Trade-off with frequency. Can give a factor of 10-100? b) Low critical energy for LAT? E c =10MeV > 1.5MeV: a factor of 2? (see Figure) Step 5) Calculate frequency: From Step 1) 3.8x10 -12 /cm 2 /s/sr From Step 2) core radius=14X=420m To be in the core area 3.14x420 2 =5.5x10 5 m 2 Freq = 2 x 10 -2 /s (~4-8 e/ m 2 ) To be in a 10 times denser area Freq ~ 2 x 10 -3 /s (~40-80 e/ m 2 ) To be in a 100 times denser area Freq ~ 2 x 10 -4 /s (~400-800 e/ m 2 )

31. Horizontal Air Shower? (1/2) Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273 Ordinary air shower initiated by protons and nuclei lose ~all energy for zenith ang. >50 deg. A different population “hirizontal” shower has been detected. If LAT is hit horizontally the electron multiplicity can be much lower. Step 6) Take horizontal air showers with Ne>10 4 Intensity = 2 x 10 -13 /cm2/s/ster (see the right fig.) Likely zenith angle = 65, 75, 85 deg. (see the fig. in the next slide.) Overburden=1kg/cos(65,75,85deg)=2.4, 3.9, 11.5 kg = 67, 108, 319 X (the shower hist. may be shorter.) Typical lateral size: assume to be half the detector size of the Akeno exp. > radius=20m

32. Horizontal Air Shower? (2/2) Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273 Step 7) Calculate frequency and electron density Core area = 1250m 2 Electron density = >10 4 /1250 = >8/m 2 Freq = 2.5x10 -6 /s/sr To be in the core area (1250m 2) Freq ~ 2.5 x 10 -6 /s (>8 e/ m 2 ) To be in a 10 times denser area Freq ~ Prob. of 10 fold fluct. x 2.5 x 10 -7 /s (>80 e/ m 2 )

33. Conclusion 1) Frequency of LAT being within the core radius (~420m for 10 7 GeV) is high (~1/min) but average electron density is only ~4-8/m 2. 2) Electron density probably fluctuate as much as 100 times, but the product of frequency and multiplicity remains constant for a given shower energy. Freq ~ 2 x 10 -2 /s (~4-8 e/m 2 ) Freq (x 10) ~ prob. of 10 fold fluct. x 2 x 10 -3 /s (~40-80 e/m 2 ) Freq (x 100) ~ prob. of 100 fold fluct. x 2 x 10 -4 /s (~400-800 e/m 2 ) 3) Guestimate for 10 8 GeV protons: Frequency 1/100, multi. is 10 times. Freq ~ 2 x 10 -3 /s 2 x 10 -4 /s (~40-80 e/m 2 ) Freq ~ prob. of 10 fold fluct. x 2 x 10 -5 /s (~400-800 e/m 2 ) Freq ~ prob. of 100 fold fluct. x 2 x 10 -6 /s (~4000-8000 e/m 2 ) 4) Horizontal showers are likely to produce high multiplicity events than normal showers.