A fast precision tracking trigger with RPCs for high luminosity LHC upgrade

1. A fast precision tracking trigger with RPCs for high luminosity LHC upgrade G. Aielli, B. Liberti,*R. Cardarelli and R. Santonico University and INFN Roma Tor Vergata TIPP Chicago 13 June 2011

3. Radiation and cavern background uncertainty estimate scale to adjust Hz/cm2 CSC measurement MDT measurement Simulation R

4. L1 trigger . Realtime reconstruction of EI segment • Bunch - ID • Requirement of matched pointing segment • fake removal • track by track correction for • multiple scattering in calo • size of luminous region • smearing by 2-3 mrad to correct •  Improved pT resolution at L1 • Required angular resolution = 1 mrad Present trigger : BW TGC X Required to send (R, f, dq) to sector logic max allowed delay 1.088 msec to arrive at sector logic input X integrating NSW in trigger

5. RPC for the Small Wheel upgrade • Baseline: Hybrid RPC-sMDT detector • Integration of mechanical structure • Sharing of LV and Readout • RPC is designed to provide: • 1 mrad angular resolution on bending coordinate • 1 mm resolution second coordinate • Sub ns timing and TOF capability • Full coverage and tracking efficiency > 97% 30-40 cm 1st layer 2nd layer θ • The trigger function is provided by an electronic chain measuring the azimuth angle from digital local coordinates. • The zero suppression is applied on chamber • The angle calculation requires about 50 ns on top of the signal delivery time to USA15

6. Proposal Strategy and key points • Rate capability enhancement • New FE electronics allowing a working point with 1/10 of charge delivered in the gas with respect to ATLAS standard  achieved • New detector layout 1+1 mm gap allows to at least halve the total charge delivered for a given signal, improving also the prompt charge distribution and the timing prototype under test 2011 H8 campaign. • Timing • 1+1 mm gap  0.5 ns sigma for each gas gap • Trigger  based on fast precision measurement (~0.3 mm on a single gap) including zero suppression • Uncorrelated background pileup suppression  strict space-time coincidence • 2 ns width coincidence, correction for signal propagation delay on strips is not needed • Virtual PAD of ~30x1 cm^2 • 2/3 majority per chamber (2 chambers per station) • Integration with sMDT chamber • Sharing mechanics due low profile chamber (3.5 cm) • Sharing LV services and readout for the second coordinate • Provide timing and hit position for the tube

7. Detector proposal outline • Detector element baseline: 1+1 mm gap • average total charge delivered 0.5 pC per count • Time resolution of about 0.5 ns (e.g. almost gaussian time distribution) • Full efficiency at 10 kHz/cm^2 • Intrinsic space resolution better than 0.3 mm • Resistive plate baseline: ATLAS standard laminate • Chamber baseline: RPC Triplets • Triplets will be used for redundancy in a 2/3 majority • Readout Baseline: Eta + Phi on the single gap • Eta segmented in 2 mm pitch strips read out by Maximum Selector. Optionally the average of each 8 strips can be read by the MDT mezzanine spare channels. • Phi segmented in ~1 cm strips (variable with the radius), read out by the spare Mezzanine channels.

8. Trigger proposal outline • Coincidence type baseline: • (2/3maj AND 2/3maj )Eta • Space time coincidence • DEtaexpected to be a ~1 cm. To be calculated by the MC taking in to account multiple scattering and maximum deflection on the bending coordinate • Dphi defined by the coincidence width x signal propagation speed • Time coincidence baseline ~2 ns with 1+1 mm gap (no propagation time correction is needed see after) • Trigger occupancy baseline estimated in about 44 Hz per station. Can be easily improved

9. Draft layout of a EIL chamber (triplet) 1. Phi strips 2. Gas volume 3. Eta strips 4. Spacer 4 3 2 1

10. Fast precision trigger with ( RPC) for ATLAS SW • Fast precision trigger required : • Precision spatial information from the front-end electronics of RPC ( 2mm strip pitch ~0.3 mm resolution) • Fast trigger decision ( 50 ns + cable length latency) • High rate uncorrelated background rejection

11. Tracking residuals H8 test beam results Overall CS=2 result No systematic correction Strip by strip

12. Precision spatial information from the front-end electronic of RPC ( 2mm pitch) strip Pitch 2mm RPC

13. RPC based fast trigger scheme for the SW • The New RPC Front End allowed a new working mode with a factor 10 less of charge per count  10 KHz/cm^2 as tested • Tracking trigger: a new type of • low-cost • low-consumption • Fast • compact electronic readout circuit allows fast precision tracking for local trigger generation on the Eta. • It works finding the maximum of the RPC charge distribution 4 4 4 4 4 4 ACES 2011

14. Amp and Maximum Selector Maximum selector • N strips are processed at the same time (N can vary reasonably in the range of ~10) • The Maximum selector amplifies the inputs and outputs a negative signal only in correspondence of the strip above a settable fractional threshold, normalized to the average charge provided • The threshold is chosen to have one or two strips firing (cluster size 1 or 2) • The decoder transforms the simple digital pattern in to a number representing the hit coordinate on the chamber • The processing time of (7-10 ns) is highlighted in figure 7-10 ns

15. Maximum Selector performance Ch3 slightly >Ch4 Ch3 = Ch4 Ch4 slightly >Ch3

16. Readout and trigger scheme example 2 mm pitch micro strips grouped by 8 Stripped readout plane RPC1 RPC2 Maximum selector 2 transistor 20 mW per channel decoder Output : binary number giving the position of the maximum; 8x4 strips =5 bits +1 for CS=2 40 ns delay for processing Single RPC plane spatial resolution N2 σ = 2 mm / √12 = 580 µm (only CS=1) Strip pitch 2 mm TRIGGER DECISION: N2-N1 <X σ = 2/2 mm / √12 = 289 µm (CS=1 or 2) N1 It will be tested in the summer H8 test beam

17. Overall Muon station Trigger scheme 2 ns 2/3 majority 2 ns 10 ns OR Max selector OR Max selector OR Max selector 1MHz 2/3 majority AND 1MHz 0.7 kHz RPC 1 RPC 2 RPC 3 OR Max selector OR Max selector OR Max selector 2kHz x 100 strips 0.7 kHz RPC 1 RPC 2 RPC 3 44 Hz Decoder +FIFO Latch Latch Chamber 1 Chamber 2 Optical link N1+T1

18. Strip delay correction Dx • Using the doublet 2 ns coincidence (2/3 majority) • Maximum geometrical delay: Dx*tana/c  negligible • Mean-timer electronics not necessary • Equivalent to ~30 cm segmentation in Phi • Overall virtual PAD of 30x1 cm^2 2ns * c/2 a Front End Front End Front End Front End AND 2ns

19. Trigger diagram 2 ns 10 ns 1MHz/ 5 strips 2/3 majority AND OR 5 strips Max selector OR 5 strips Max selector OR 5 strips Max selector 0.7 kHz x 100 strips (one chamber) 0.7 kHz on 30 cm virtual PAD RPC 1 RPC 2 RPC 3 44 Hz N1+T1 Decoder +FIFO Optical link Latch Chamber 1

20. RPC layout details • The RPC layout follows the MDT one • Eta strip pitch 2mm • External chambers along R have increasing Phi strip pitch • Total channels per wheel ~200000 all included • On wheel power consumption ~4 kW (includes FE, maximum selector and decoder) • The low voltage supply can vary in the range of 2-3.5 V, can be integrated with the MDT system

21. Conclusions Detector: • 10 kHz/cm^2 is done • 0.3 mm spatial resolution is done • Layout of detectors is in advanced phase Electronics: • Front-end is done • Maximum selector is done • Trigger strategy baseline defined to reject the uncorrelated background • Minimal number of channels and interconnections