A Cosmic Muon Tracking Algorithm for the CMS RPC based Technical Trigger

Transcription

1 A Cosmic Muon Tracking Algorithm for the CMS RPC based Technical Trigger by Rajan Raj Thilak Department of Physics University of Bari INFN on behalf of the CMS RPC-Trigger Group (Bari, Frascati, Sofia, Napoli, Pavia and Warsaw)

2 CMS RPC Technical Trigger Motivation Objective select Cosmic Muons produce Sector level triggers and Wheel level triggers Hurdle for test and calibration of detectors during commissioning and later running of CMS. test DT, RPC and Tracker alignment CMS RPC Trigger System was build to identify Muon Tracks from the Interaction Point. Challenge Solution needs to be Compact and Inexpensive To use existing electronics infrastructure with minimal modifications (if required) and attain the Objectives

3 CMS RPC Trigger System Overview Detector Periphery Counting Room Link Box TRIGGER BOARD Ref : RPC Based Technical Trigger for CMS Exp, Flavio Loddo, CMS CR-2006/088 FEB FEB Link Board Sync, LMUX & Optical Trm. Control Board Link Board CCU RPC LVDS SplitterBoard L D M U X PAC DAQ Ghost Buster Data Concentrator Card Ghost Buster & Sorter To Global Muon Trigger To DAQ Link Boards : Synchronize the signals with the LHC clock and data compress for optical transmission Trigger Boards : Receives LB Fibers and implements the PAC (Pattern Comparator) algorithm Interconnections between Links Boards and Trigger Boards are optimized for vertex geometry.

4 CMS RPC Trigger System Overview : Trigger Board TLK2501 De-serializer Altera FPGA Opto Sync. Altera FPGA TTU PAC Trigger Board (designed by Warsaw Team) : De serialize Data, Synchronize and Run the PAC (Pattern Comparator) algorithm. To detect Cosmic Muons > replace PAC Firmware with a new Firmware

5 CMS RPC Technical Trigger Implementation: Phase 1 Detector periphery 1 RBC/ 2 sectors Counting Room RBC RBC RBC Barrel Wheel RBC Fiber 30 Optical Fibers RBC RBC (RPC Balcony Collector) 6 Fibers/wheel RBC Detector Periphery : RBC RPC Balcony Collector Ref : RPC Based Technical Trigger for CMS Exp, Flavio Loddo, CMS CR-2006/088 Each RBC reads 2x (13 or 15) OR MAP from and makes Sector Level Trigger. Passes these OR's and Sector Level Trigger passed to the Counting Room. Each => 1 sector (13 to 15 OR's) ; Each RBC => 2 s( 2 sectors ) ; 6 RBCs => 1 Wheel

6 RPC Technical Trigger Implementation: Phase 2 ORs from 2 sectors RBC ORs from 2 sectors 2 Sector Triggers From 6 RBC PHASE 2 : RBC + Technical Trigger Unit (TTU) Detector periphery Trigger Board used as Technical Trigger Unit PAC algorithm replaced by CMTA algorithm TTU (1 Wheel) Cosmic Muon Tracking Algorithm 12 RBC Sector Triggers Task in Hand : Firmware for TTU => CMTA Algorithm! Counting Room Programmable mixer Trigger Board as TTU From 5 TTU Crate backplane Programmable mixer

7 Birds Eye View : Muon Trigger Block Diagram (Before) RPC PACT Pattern Comparator DTBX Barrel BTI Bunch & Time Id TRACO Track Correlator Wire Cards CSC Endcap Strip Cards Motherboard Trigger Server Port Card DTTF Drift Tube Track Finder CSC Cathode Strip Ch. Track Finder Quiet Bits from Cal. Trigger RPC Sorter DT Sorter CSC Sorter Global Muon Trigger To Global Trigger

8 Birds Eye View : Muon Trigger Block Diagram (Now) RPC DTBX Barrel CSC Endcap RBC RPC Balcony Collector PACT Pattern Comparator BTI Bunch & Time Id TRACO Track Correlator Wire Cards Strip Cards Motherboard TTU with CMTA Trigger Server DTTF Drift Tube Track Finder Port Card CSC Cathode Strip Ch. Track Finder Quiet Bits from Cal. Trigger RPC Sorter DT Sorter Global Muon Trigger CSC Sorter To Global Trigger

9 Firmware for the TTU... from RBC ORs (12x15) bits Mask (12x15) bits Force(12x15) bits Min. Length Of Track Sector Delays Sector level Triggers Trigger Config. TTU Firmware Clocked at 40MHz Trigger few Hz Cosmic Muon Track[ ] (Id,Sector, Station) Slow Ctrl. Configuration written in VHDL Objectives : Process the input OR's (12x15) provided by RBC at every Bx to detect Multiple Tracks Produce a Wheel-level Trigger if the Length of Muon Track >= Min. Length Of Track set Store all the Seeds (Station co-ordinates) of the Track Configurable Mask, Force and other settings through Slow control configuration.

10 TTU CMTA Algorithm Definition Latency : In a system its the Time (in Clock cycles) that elapses between the Stimulus and its Output A single component of latency 1 Bx. difficult to implement OR Map Trigger Algorithm Firmware Trigger consumes lot of Chip area. Solution : Implement CMTA in a Pipeline LHC Clock f = 40 MHz Number of smaller parallel processes. Trade-off Latency = 1 Bx. Latency <=> Chip Area Preferably Modular and Generic OR Map Process 1 Process 2 Process N Trigger LHC Clock f = 40 MHz Latency = N Bx.

11 Trigger Algorithm: The Wheel Map... Stations Sectors Comic Visualization of Wheel (@ 1 Bx.) OR Map (12 x 15) -> Wheel Map (12x6) Notice that every chamber of the Muon Track has at least 1 Chamber HIT in the periphery

12 Trigger Algorithm: Connecting the Dots Sector Station Track Len RB4 1 5 RB3 2 6 RB3 3 7 RB4 4 1 RB2_OUT 1 12 RB RB4 3 Generate Wheel Level Trigger 1 Find Initial seed scanning from the Top most station (RB4) to the Innermost station (RBIN) Priority Scan: for hits in sector order 4,5,3,2,6,7,1,8,12,9,10,11 Track the Path and Increment Length of Track at every New Seed found. Find Multiple Tracks and Store all Seeds.

13 Modularity Tracker and Seed... Id(N-1), Station (N-1), Sector(N-1), Track Length(N-1) Seed (N-1) Seed N Id(N), Station (N), Sector(N), Track Length(N) Tracker (N) 40 MHz Input Map (with Seed N-1) Seed (N-1) Seed (N) Output Map (without Seed N-1) Generic Tracker : Scan the periphery of the input seed and find next seed, if seed found Increment Track Length, pass the new seed and map if seed not found initialize Track Length = 1, pass the new seed and map

14 Parallelism Trackers and Seeds... Trackers f = 40 MHz Initial Seed Buster Tracker 1 Tracker 2 Tracker N Seed 0 Seed 1 Seed 2 Seed N Memory Initial Seed Buster : Scans from the top most station RB4 of the Wheel Map to bottom RB1 IN, in search of a seed. Each Tracker finds a new seed and passes the new Map and new seed to the next Tracker Total Number of Trackers can be Statically parametrized during Synthesis. No. of Trackers = Max length of the Track. Currently (N =14). Seed Out []

15 CMTA Component Flow (Main Blocks) Inputs from RBC Mask Data Masked OR Map (12x15 bits) Check Force Force OK Flag Wheel Mapping Wheel map (12x6 bits) Initial Seed Buster Wheel 0 Seed 0 Trackers(1...N) INTERNAL RAM Data Readout Control Tracks [ ] Filters Final Track [ ] Choose Track Max Track Length >= Trigger Config Final Trigger Out Config. Registers Status Registers Internal Diagnostic Tool Min. Length Of Track LHC Clock f = 40 MHz

16 Preliminary Off-line Analysis of CMTA Generated a set of Cosmic Muon Events with CMSCGEN - Cosmic Monte Carlo Generator for CMS Single Cosmic Muon per event No Magnetic Field No Noise Patterns were further filtered applying a Sector level Constraint of N i.e at least N Chambers have contiguous hits in any single sector. to ensure most of the tracks pass through a single wheel. These patterns were passed to the CMTA and Minimum Length of Track Parameter of the CMTA was varied.

17 Patterns and Triggers with Sector level Constraint = 3 No. of Patterns and No. of Triggers Minimum Length of Track Number of Patterns with >= No. of Triggers 100 % 96 % 81 % 74 % Number of Patterns Number of Pattern with Hits 3 : 1269 Number of Pattern with Hits 4 : 1238 Number of Pattern with Hits 5 : 1113 Number of Pattern with Hits 6 : 901

18 Comments on Preliminary Results CMTA is fully efficient when patterns have consecutive chambers hit CMTA not efficient when muon tracks: are oblique and hence pass through multiple wheels do not cross contiguous chambers due to the Detector Geometry pass through the center of the detector and hence are detected as 2 small tracks. Most of these inefficiencies can be removed by combining the RBC(Sector Trigger) + TTU (Wheel Trigger) Possible Improvements in CMTA Under Study CMTA Jump : Tracker scans for 2 layers in Periphery instead of 1 layer Smart Patch : Combines 2 smaller Tracks Sector Level Trigger -> Wheel Level Trigger -> Barrel Level Trigger?

19 Run with Min. Track Length = 5 (Test on Wheel +1 with Sector 10 and Sector 11 active) Number of Entries VS Number of fired Planes

20 Selected TB Snapshots with Min. Track Length = 5 (Test on Wheel +1 with Sector 10 and Sector 11 active)

21 Summary RPC based Technical Trigger independent debugging tool for the test and calibration of sub-detector chains of the CMS CMTA : Configurable Firmware implemented in the TTU to select Cosmic Muons. can detect Multiple Tracks, at every Bx. produce Wheel Level Triggers VHDL Library and Single-click Test-Bench ready. To do : To do further off-line analysis by adding noise and magnetic field to input patterns Find solutions to inefficiencies Study the Timing and synchronization of the TTU Define Trigger Configuration for different applications