“Introduction to LKr L1”

1. “Introduction to LKr L1” GianlucaLamanna 9.2.2011 “Online trigger” meeting

2. LKr readout: reminder Lkr Trigger LKr L1 PC To L1TP • The LKr is a “singular” system in the NA62 TDAQ: • The continuous digitization @40 MHz produces ~7 Tb/s → only 4x4 cells trigger sums (supercells) are sent to the LKr Trigger system • The ~432 CREAMs aren’t read at L0: @1 MHz the bandwidth would be 1.7 Tb/s (~4 Gb/s/CREAM) (without zero suppr.) → no contribution to L1 trigger decision using data • The LKr is read at L1: @100 kHz the bandwidth will be ~200 Gb/s (~0.5 Gb/s/CREAM) (without zero suppr.) → one link per board Trigger sums (16 cells) To L0TP CREAM To L2 Circular buffer (up to 10 ms) Linear buffer (up to 15 s) L0 L1

3. Contribution at L1 • The LKr L1 PC receives the “reduced” primitives (based on 4x4 cells): • Clusters multiplicity, distances, energy, projections and momenta are computed directly on the LKr L0 trigger system • Difficult to image further calculations on 4x4 cells granularity in the L1 LKr PC (everything is done before, in the FPGAs) • Service functions: • Propagate L0 Trigger System information to L1TP (i.e. LKr Energy to build ETOT with MUV1-2,…) • Consistency check on L0 trigger primitives → no consistency check on LKr data at L1

4. Regions of Interest (ROI) L0 Lkr Trigger LKr L1 PC SWI TCH ROI data • ROI readout: • The LKr L0 Trigger system (concentrator board) asks to specific CREAM modules to send data to the LKr L1 PC • The ROI request is sent with a fixed delay (>1ms) after the corresponding L0 primitive • The LKrL0 trigger system is in charge to send the destination address to the selected CREAMS To L1TP Trigger sums (16 cells) ROI request To L0TP CREAM ROI data: to LKr L1 PC Circular buffer (up to 10 ms) Linear buffer (up to 15 s) To L2 One link only L0 L1

5. Regions of Interest (ROI) • The LKr L0 trigger system will ask ROI readout for particular events: • The request is based only on LKr information: single cluster with “strange” shape, too close double clusters… • For each ROI request 4/5 CREAMS will be read • Simulation to understand the increasing in readout rate • Assuming max 250 Mb/s (1/2 of the free bandwidth if the L1 is 100 kHz) dedicated to ROI r/o and flat gamma distribution → max 0.5 MHz of ROI requests Pion and gamma cluster at d=17 cm in 4x4 cells and in full readout

6. Effectiveness of ROI • ~½ of pp0 with “signal” in LAVs→~102 kHz remains • ~90% of pp0(after LAV) with “signal” in the SAV→~7 kHz remains [Spasimir October TDAQ WG] • The inefficiency of the 30 cm LKr cut gives 57 kHz (rejectable with !SAV) • A part of the 57 kHz could be rejected using ROI, if we want to avoid to use SAV or we can’t use STRAWS • If we use STRAWS (or SAV) the ROI is useless! (at least for the main trigger)

7. Conclusions • The contribution of the LKr at L1 will be relatively small • The LKR L0 trigger system will reject most of the pp0 in the LKr acceptance at L0 • The LKr L1 PC is useful to transmit the primitives produced from the L0 trigger system to the L1TP • The ROI readout is easy to be implemented in the present readout scheme, but the utility depends on the way to threat at L1 the events with gammas with small angle (my favorite way is with STRAWS)