************************************************ * * * Specification of Isolated Electron Algorithm * * * * for * * * * D-Zero Level 1.5 Calorimeter Trigger * * * ************************************************ 31-AUG-1994 Introduction ------------ The purpose of this document is to specify the Isolated Electron (1x2 EM vs. 3x3 Total) Algorithm for the Level 1.5 Calorimeter Trigger. This document is divided into the following parts: (i) Interface with COOR (ii) Local Tool Interface with Local Frame (iii) Local Tool Processing (iv) Local Tool DeBug Section Contents (v) Global Tool Interface with Global Frame (vi) Global Tool Processing This file should be used in addition to the file: TRGL15CTHS:L15CT_MULTIPLE_TERMS_SINGLE_TOOL.TXT to understand the multiple Term operation of the 1x2_EM_vs_3x3_Total Tool. (i) Interface with COOR ----------------------- The format of the communication between COOR and the Trigger Control Computer (TCC) is given in the official COOR-to-TCC message format specification document. This document only describes the information which will be provided by COOR, it does not specify the message passing format. The Local Tool receives from COOR the following quantities at initialization: (1) Local Tool Number. The Local Tool Number of this Tool is: 2 Note that this Tool Number is not assigned by COOR, but instead COOR must know the Tool Number assigned to this Local Tool. (2) Local Parameters. Parameter Parameter Parameter Parameter Number Name Format Units --------- --------- --------- --------- 1 EM_Et_1x2_Threshold Floating GeV 2 EM_Et_vs_Tot_Et_Ratio Floating -unitless- The Local Tool will impose the following range restrictions on the Local Parameters: Parameter Parameter Parameter Parameter Number Name Minimum Maximum --------- --------- --------- --------- 1 EM_Et_1x2_Threshold 0.25 128 2 EM_Et_vs_Tot_Et_Ratio 0.01 100 In the current implementation, this Local Tool may only use Crate #0 Terms #0, #1, #2, and #3. COOR must at least specify Term #0, and may optionally specify any or all of Terms #1, #2, and #3. Terms which are not specified by COOR will have benign default Parameter values assigned by TCC. From the point of view of the Tool, all 4 Terms must be defined. Also note that, at run time, all 4 Terms will be evaluated for each Seed. The Local Frame (to support the Local Tool), receives from COOR the following quantities at initialization: (1) Reference Set. The Local Frame requires one EM Et Reference Set (which is Reference Set #0) to generate "seeds" for the Local Tool. This reference set is separate from all Level 1 Calorimeter Trigger Reference Sets, although it is defined in the same fashion. Only one Reference Set (Ref. Set #0) is used by the L1.5 Cal Trig to evaluate all 4 Terms. The Global Tool receives from COOR the following quantities at initialization: (1) Global Tool Number. The Global Tool Number of this Tool is: 2 Note that this Tool Number is not assigned by COOR, but instead COOR must know the Tool Number assigned to this Global Tool. (2) Global Parameters. Parameter Parameter Parameter Parameter Number Name Format Units --------- --------- --------- --------- 1 Object_Count_Threshold Integer objects The Global Tool will impose the following range restrictions on the Global Parameter: Parameter Parameter Parameter Parameter Number Name Minimum Maximum --------- --------- --------- --------- 1 Object_Count_Threshold 0 8 Also for the current implementation, this Global Tool must be mapped by COOR to L1.5 Cal Trig Terms #0, #1, #2, and #3 (in Crate #0). Again, note that COOR must define at least Term #0, but then may optionally specify any or all of Terms #1, #2, and #3. Terms which are not specified by COOR will be given default benign parameter value by TCC. Again, from the point of view of the Tool, all 4 Terms must be defined, and all 4 Terms will be evaluated for each "cycle" of the L1.5 Cal Trig. (ii) Local Tool Interface with Local Frame ------------------------------------------ The Local Tool receives from the Local Frame the following quantities: (1) The Trigger Tower eta and phi indices of a candidate seed Trigger Tower. Call these (eta, phi) indices (i, j). Recall that a candidate seed Trigger Tower is defined as a Trigger Tower with EM Et greater than or equal to the Reference Set Et defined for that Trigger Tower and this Tool. (iii) Local Tool Processing --------------------------- The Local Tool performs the following processing: (1) The Local Tool examines the four neighboring Trigger Towers to determine which of these four Towers has the greatest Et. Call the (eta, phi) indices of this Tower (k, l). On a LEGO plot, the four neighbors are defined as follows: +------------+ | eta = i | | phi = j+1 | | (neighbor) | +------------+------------+------------+ | eta = i-1 | eta = i | eta = i+1 | | phi = j | phi = j | phi = j | ^ | (neighbor) | (seed) | (neighbor) | | +------------+------------+------------+ | | eta = i | | | phi = j-1 | | | (neighbor) | phi +------------+ eta ----> The neighbors will be examined clockwise (on the above plot), starting with the (eta=i, phi=j+1) Trigger Tower. In the event that two neighbors have equal Et, preference is given to the FIRST neighbor found. Recall that in the Trigger Tower addressing scheme, eta indices +1 and -1 are adjacent (i.e. there is no eta index of 0), and phi indices 1 and 32 are adjacent (i.e. the phi indices wrap around the detector). (2) The Local Tool calculates the sum of the EM Et in the seed Tower and the neighboring Tower with the greatest Et (as determined above): EM_Et_1x2_Sum = EM_Et(i, j) + EM_Et(k, l) (3) The Local Tool calculates the sum of the Total Et of the 9 Trigger Towers around the seed Tower (i.e. the seed tower and its EIGHT neighbors): m = i+1 n = j+1 __ __ Total_Et_3x3_Sum = \ \ Total_Et(m, n) /_ /_ m = i-1 n = j-1 Note that all of the above calculations and comparisons are done with the pedestals removed from the Trigger Tower Et. (4) The Local Tool applies the following two tests for all 4 Terms: Is the EM_Et_1x2_Sum >= EM_Et_1x2_Threshold Is the | EM_Et_1x2_Sum/Total_Et_3x3_Sum | >= EM_Et_vs_Tot_Et_Ratio (note that this compares the MAGNITUDE of the actual ratio to the ratio threshold. The ratio threshold is non-negative--this is guaranteed by range-checking) If either test fails, the Local Tool proceeds to evaluating the next Term (or, if it has evaluated the last Term, it returns to the Local Frame) without saving any results (unless this is a Mark and Force Pass event, in which case the Local Tool continues with the next step). If both tests are passed, then the Local Tool performs the next step. (5) The Local Tool makes an entry in the Local List of Identified Objects. This entry should be 3 longwords long, and should contain the following information: Bits in 1st longword -------------------- 0:7 Term Number that generated this entry 8:15 Local DSP Tool Number (= 2 for 1x2 EM vs. 3x3 Total) 16:23 Eta coordinate of the seed Trigger Tower, this is an 8-bit signed integer which can be in the range {-20..-1, +1..+20} 24:31 Phi coordinate of the seed Trigger Tower, this is an 8-bit unsigned integer which can be in the range {1..32} Bits in 2nd longword -------------------- 0:7 Object Type Code (=1 for Isolated Electrons) 8:15 Real or Mark and Pass Data (always 0 : real entry that passed the Local Term Algorithm FF (hex) : entry that failed the Local Term Algorithm, but was saved because this is a mark and pass event 16:31 EM_Et_1x2_Sum. This is a 16-bit signed integer with units of 1/4 GeV per count. This quantity has no pedestal. Bits in 3rd longword -------------------- 0:15 Total_Et_3x3_Sum. This is a 16-bit signed integer with units of 1/4 GeV per count. This quantity has no pedestal. 16:23 "Delta-eta" (with respect to the seed Trigger Tower) of the neighbor Trigger Tower used in the calculation of the EM_Et_1x2_Sum. This will be a signed integer which can be either -1, 0, or +1. 24:31 "Delta-phi" (with respect to the seed Trigger Tower) of the neighbor Trigger Tower used in the calculation of the EM_Et_1x2_Sum. This will be a signed integer which can be either -1, 0, or +1. (6) The Local Tool then exits, returning control to the Local Frame. For the initial implementation of the Level 1.5 Cal Trig, this Local Tool will be the only Local Tool running in each Local DSP. Also note that this Local Tool will be mapped to L1.5 Cal Trig Terms #0, #1, #2, and #3, each with its own set of Local Parameters. (iv) Local Tool DeBug Section Information ----------------------------------------- A DeBug Section Type 1 Entry for this Local Tool will contain the Trigger Tower Data. Only one DeBug Section Type 1 Entry from each Local DSP will be present in an MFP Data Block. The format of this Type 1 Entry is specified in the Data Block Format document. A DeBug Section Type 2 Entry for this Local Tool will contain the EM Reference Set Data. Only one DeBug Section Type 2 Entry from each Local DSP (corresponding to Reference Set #0) will be present in an MFP Data Block. The format of this Type 2 Entry is specified in the Data Block Format document. A DeBug Section Type 3 Entry for this Local Tool will contain the Derived Constants for this Local Tool, as well as the Tool Number of this Tool, and the Term Number to which this Local Tool is mapped. This Local Tool will have 5 Derived Constants. The Derived Constants are: Derived Constant Number Derived Constant Description -------- ---------------------------- 1 Total Et 3x3 Zero Response for eta = n+2 2 Total Et 3x3 Zero Response for eta = n+3 3 Total Et 3x3 Zero Response for eta = n+4 4 Total Et 3x3 Zero Response for eta = n+5 5 EM Et 1x2 Threshold in ADC Counts Note that a DeBug Section Type 3 Entry will be 8 longwords long, as it contains the Type 3 Entry Header, the Term Number to which this Tool is mapped, the Tool Number of this Tool, and the 5 Derived Constants. Also note that there will be FOUR DeBug Section Type 3 Entries, one for each of Terms #0, #1, #2, and #3, from each Local DSP. (v) Global Tool Interface with Global Frame -------------------------------------------- The Global Tool receives from the Global Frame the following information: (1) The Local Lists of Identified Objects from each of the 11 Local DSPs (as collected in the Global DSP). (vi) Global Tool Processing --------------------------- (1) The Global Tool computes the number of isolated electrons found for each Term in the Local DSPs. It does this by examining each of the Valid Objects in each Local List of Identified Objects. It determines the Term Number for each Object, and increments a Number_of_Electrons Counter for each Term. There will be 4 such Number_of_Electrons Counters, one for each of Terms #0, #1, #2, and #3. (2) The Global Tool then performs the following test for each of Terms #0, #1, #2, and #3: Is the Number_of_Electrons >= Electron_Count_Threshold? If this test is met then L1.5 Cal Trig Term corresponding to this Global Tool is mared as passed. Otherwise the corresponding L1.5 Cal Trig Term is marked as failed. (3) The Global Tool then exits, returning control to the Global Frame. For the current implementation of the Level 1.5 Cal Trig, this Global Tool will be the only Global Tool running in the Global DSP. Also note that this Global Tool will be mapped to L1.5 Cal Trig Terms #0, #1, #2, and #3, each with its own Global Parameter. Note that this Global Tool does NOT make any entries in the Global List of Identified Objects. It will, however, report the Global Number of Identified Objects in the Header of the Global List of Identified Objects.