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TOF contribution to the Minimum Bias Trigger of pp collisions

TOF contribution to the Minimum Bias Trigger of pp collisions. Terzo Convegno Nazionale sulla Fisica di ALICE. Summary. TOF geometry Trigger with the TOF PYTHIA pp collisions – fully reconstructed events Efficiency for the trigger Efficiency for beam-gas/halo events. TOF geometry.

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TOF contribution to the Minimum Bias Trigger of pp collisions

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  1. TOF contribution to the Minimum Bias Trigger of pp collisions Terzo Convegno Nazionale sulla Fisica di ALICE

  2. Summary • TOF geometry • Trigger with the TOF • PYTHIA pp collisions – fully reconstructed events • Efficiency for the trigger • Efficiency for beam-gas/halo events

  3. TOF geometry Holes for the PHOS 18 SuperModules

  4. TOF geometry (II) The TOF detector is composed by: • 18 Super Modules (18 sectors in ) • 1600 MRPC x 96 channels • Granularity: 2.5x3.5 cm2 at 3.7 m from the primary vertex; • Total sensitivity area  150 m2 • Time resolution, σ < 100 ps • High efficiency, ε > 99%

  5. The TOF trigger • Based on a very fast detector (L0); • Large area; • || <1; • High segmentation; • FPGA Flexibility allows to search for different topology and to change the trigger selection on the fly. • Status: Magnetic and radiation test for all the electronic components: done.

  6. Trigger with the TOF • Ultra Peripheral AA collisions (L0) • pp MB (L0) • High multiplicity (L0) • Jets in pp collisions (L1) • Cosmics (commissioning, μ physics) (L0); AliTOFTrigger class: read the TOFdigit information and return the mask with the TOF trigger response.

  7. Granularity for the TOF trigger TOF pad (~ 10 cm2) 2 MRPC = 2 x 96 ch 2 x ½-MRPC .OR. of 96 ch MaxiPad (MP) 2 x ½-MRPC .OR. of 96 ch MaxiPad (MP) 1000 cm2

  8. 36 x 25 36 x 25 Stratix II 25x36 input Stratix II 25x36 input Piggy back Crate 72 Crate 1 LTM Stratix II Trigger decision, VME TO CTP 1638 strips, 157248 pads ................... Crate 2 LTM LTM 72 cables, L=60 m, 25 pairs (LVDS) CTTM To Alice CTP

  9. MP-0001 MP-0865 … … MP-0864 MP-1728 Front Back The L0 MB TOF trigger LUP (Look Up table) Counter  thr. When the number of MP signals is greater than a given threshold the trigger is set ON. An independent trigger signal for each bunch crossing (time of the clock = 25 ns) can be asserted

  10. Background from the detector noise Measured rate Safety rate The choice for the MB threshold depends on the background expected for the detector noise. The Fake Trigger Rate is expected to be of the order of 1 Hz for a threshold of 4. Please note: if Single pad rate = 5 Hz/pad  FTR ( TH = 3) as low as 60 Hz, compared With few tens of kHz of MB genuine trigger

  11. Comparison with ITS-VZERO trigger .AND. notBG MB1 = GLOB.FO .OR. VZERO.OR MB2 = GLOB.FO .AND. VZERO.OR MB3 = GLOB.FO .AND. VZERO.AND

  12. 3 3 3 ALL INELASTIC Results vs. TOF threshold Comparison between TOF (Nthr = 4 MP) and MB3. The TOF gain for different processes: • 1.5% for Minimum Bias (All Inelastic) • ~8% for single diffractive • ~12% for double diffractive.

  13. Efficiency vs. Ntracks (18 SM)

  14. beam-gas/halo results (Nthr) Expected contamination to the MB pp interaction dur to beam-gas interactions. For Nthr = 4 it reduces to 2.5%

  15. Some considerations • The simulations above are performed in the pessimistic case: the background is a factor 5 higher than the one measured in the laboratory. • Should the background be at the expected level (5 Hz/pad ~ 0.5 Hz/cm2). In this case the threshold for MB triggering can be lowered to MP = 3 (FTR = 60 Hz). • Other configurations can allow to low the threshold.

  16. An example TOF .AND. ITS (Nthr < 4)

  17. Conclusions • TOF trigger performances for pp MB events was presented; • TOF trigger provides a fast (L0) and flexible signal (programmable on the fly) for each pp bunch crossing; • Fake trigger from electronics noise is under control; • The gain wrt the current MB setup was shown and it is relevant in the region of low multiplicity; • The beam-gas effect was shown.

  18. backup

  19. ITS OR di 1200 canali Soglia > 100 σ rispetto al fondo Integrazione su 100 ns (4 bunch crossing) VZERO 2 set di contatori a scintillazione 4 finestre temporali (BBA, BBC, BGA, BGC) Segnale di veto per interazioni beam-gas Detector utilizzati nel trigger

  20. Some EVENT DISPLAYs TOF TOFsw = ppMB TOF trigger response MB1sw = response for MB1 ITS-VZERO configuration MB2sw = response for MB2 ITS-VZERO configuration MB3sw = response for MB3 ITS-VZERO configuration VZERO TRD ITS TPC Red Line = primary track with a digit on the TOF Black Line = track which gives a digit on the TOF through a secondary track

  21. Efficiency wrt the MB-TOF threshold (18 SM) SD +6.5% DD +14% Gain from TOF for MB3 = 3.5 %

  22. Efficiency wrt the type of the process (18 SM) - old version (no time digit cut)

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