Generation of two particles particle gun fur ND280, T2K simulation

mpcasado · December 21, 2025, 12:52pm

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Geant4 Version: nd280Gean4Sim_7.14
Operating System: Linux-AlmaLinux_9.4-gcc_11-x86_64
Compiler/Version:
CMake Version:

Hello, I’m trying to generate mu+ and e+ in ND280, T2K experiment (HA-TPCs). I’m not able to see equal amounts of mu+ and e+ in my generation and my ML jobs are not giving sensible results. Could you tell me if my data cards are correct or would you propose me other thing? (I would like to have uniform momentum generation). Thanks a lot!

My data cards:

/t2k/control baseline-2022 1.0
/t2k/update
/gps/source/clear
/gps/source/multiplevertex false
/gps/source/add 1
/gps/particle mu+
/gps/ang/rot1 -1 0 0
/gps/ang/rot2 0 -1 0
/gps/ang/type beam1d
#/gps/ang/sigma_r 30 deg
/gps/ang/type iso
/gps/ang/mintheta 20 deg
/gps/ang/maxtheta 170 deg
/gps/ang/minphi 90 deg
/gps/ang/maxphi 90 deg

/gps/position 50 50 -230 cm
/gps/pos/type Volume
/gps/pos/shape Para
/gps/pos/halfx 25 cm
/gps/pos/halfy 1 cm
/gps/pos/halfz 60 cm

/gps/ene/type Lin
/gps/ene/gradient 0.0
/gps/ene/intercept 1.0
/gps/ene/min 11.23 MeV
/gps/ene/max 1497.83 MeV
/gps/ene/type User
/gps/hist/type energy

#Include here histogram for Kinetic Energy - Uniform momentum

/gps/hist/point 11.233986654667532 0.0012476187931736028
/gps/hist/point 26.099905717029102 0.0009987273533319935
/gps/hist/point 40.96582477939067 0.0008999107249192035
/gps/hist/point 55.831743841752235 0.0008189201050356094
/gps/hist/point 70.6976629041138 0.0007897258118217555
/gps/hist/point 85.56358196647537 0.0007606660545213296
/gps/hist/point 100.42950102883694 0.0007409565432041428
/gps/hist/point 115.29542009119851 0.0007201707445795327
/gps/hist/point 130.16133915356008 0.0007353060348401725
/gps/hist/point 145.02725821592162 0.0007042282388383269
/gps/hist/point 159.8931772782832 0.0006996540177817784
/gps/hist/point 174.75909634064476 0.0006948107248983741
/gps/hist/point 189.62501540300633 0.0006985777304743552
/gps/hist/point 204.4909344653679 0.0006876803214866955
/gps/hist/point 219.35685352772947 0.0006879493933135513
/gps/hist/point 234.22277259009104 0.000684316923650998
/gps/hist/point 249.0886916524526 0.0006706615284380667
/gps/hist/point 263.9546107148142 0.0006704597245679247
/gps/hist/point 278.82052977717575 0.0006697870450007852
/gps/hist/point 293.6864488395373 0.0006641365366368136
/gps/hist/point 308.5523679018989 0.000664809216203953
/gps/hist/point 323.41828696426046 0.0006566025254848513
/gps/hist/point 338.28420602662203 0.0006702579206977828
/gps/hist/point 353.1501250889836 0.0006618494261085393
/gps/hist/point 368.01604415134517 0.0006587551000996976
/gps/hist/point 382.88196321370674 0.0006673653985590831
/gps/hist/point 397.7478822760683 0.0006500102657268844
/gps/hist/point 412.6138013384299 0.0006627239095458206
/gps/hist/point 427.47972040079145 0.0006669617908187994
/gps/hist/point 442.345639463153 0.0006553244343072863
/gps/hist/point 457.2115585255146 0.000655660774090856
/gps/hist/point 472.07747758787616 0.0006679035422127947
/gps/hist/point 486.94339665023773 0.0006557953100042839
/gps/hist/point 501.8093157125993 0.0006499429977701729
/gps/hist/point 516.6752347749608 0.0006579478846191277
/gps/hist/point 531.5411538373224 0.0006546517547401494
/gps/hist/point 546.407072899684 0.0006609076747145415
/gps/hist/point 561.2729919620456 0.0006502120695970287
/gps/hist/point 576.1389110244071 0.0006506829452940213
/gps/hist/point 591.0048300867687 0.0006586205641862723
/gps/hist/point 605.8707491491302 0.0006520955723850143
/gps/hist/point 620.7366682114919 0.0006598986553638373
/gps/hist/point 635.6025872738534 0.0006508847491641631
/gps/hist/point 650.468506336215 0.0006490685143328916
/gps/hist/point 665.3344253985765 0.0006497411939000261
/gps/hist/point 680.2003444609381 0.0006427453264017804
/gps/hist/point 695.0662635232997 0.0006481940308956052
/gps/hist/point 709.9321825856613 0.0006520955723850193
/gps/hist/point 724.7981016480228 0.0006410636274839268
/gps/hist/point 739.6640207103844 0.0006524319121685891
/gps/hist/point 754.5299397727459 0.0006465795999344705
/gps/hist/point 769.3958588351076 0.0006476558872418987
/gps/hist/point 784.2617778974691 0.0006508847491641631
/gps/hist/point 799.1276969598307 0.0006598986553638373
/gps/hist/point 813.9936160221922 0.0006459069203673311
/gps/hist/point 828.8595350845538 0.0006489339784194637
/gps/hist/point 843.7254541469154 0.0006465123319777566
/gps/hist/point 858.591373209277 0.0006430143982286362
/gps/hist/point 873.4572922716385 0.0006570734011818464
/gps/hist/point 888.3232113340001 0.0006473195474583289
/gps/hist/point 903.1891303963616 0.0006469832076747542
/gps/hist/point 918.0550494587233 0.000653710003346154
/gps/hist/point 932.9209685210848 0.0006412654313540686
/gps/hist/point 947.7868875834464 0.0006475213513284708
/gps/hist/point 962.6528066458079 0.000643283470055492
/gps/hist/point 977.5187257081694 0.0006360857986870945
/gps/hist/point 992.384644770531 0.0006609076747145466
/gps/hist/point 1007.2505638328926 0.0006418708429644941
/gps/hist/point 1022.1164828952542 0.0006410636274839365
/gps/hist/point 1036.9824019576156 0.0006424762545749197
/gps/hist/point 1051.8483210199772 0.0006337986881588204
/gps/hist/point 1066.7142400823388 0.0006533736635625893
/gps/hist/point 1081.5801591447002 0.0006418035750077801
/gps/hist/point 1096.4460782070619 0.00064725227950161
/gps/hist/point 1111.3119972694235 0.0006493375861597424
/gps/hist/point 1126.1779163317851 0.0006535081994760172
/gps/hist/point 1141.0438353941465 0.0006384401771720829
/gps/hist/point 1155.9097544565082 0.0006495393900298842
/gps/hist/point 1170.7756735188698 0.0006458396524106171
/gps/hist/point 1185.6415925812314 0.0006416690390943622
/gps/hist/point 1200.5075116435928 0.0006527009839954399
/gps/hist/point 1215.3734307059544 0.0006510192850775912
/gps/hist/point 1230.239349768316 0.000638171105345227
/gps/hist/point 1245.1052688306777 0.0006403909479167972
/gps/hist/point 1259.971187893039 0.0006343368318125319
/gps/hist/point 1274.8371069554007 0.0006363548705139503
/gps/hist/point 1289.7030260177623 0.0006560643818311372
/gps/hist/point 1304.568945080124 0.0006520283044283103
/gps/hist/point 1319.4348641424854 0.0006572079370952744
/gps/hist/point 1334.300783204847 0.0006434180059689149
/gps/hist/point 1349.1667022672086 0.0006527682519521538
/gps/hist/point 1364.0326213295702 0.0006553244343072938
/gps/hist/point 1378.8985403919316 0.0006419381109212081
/gps/hist/point 1393.7644594542933 0.0006522973762551561
/gps/hist/point 1408.630378516655 0.0006525664480820119
/gps/hist/point 1423.4962975790165 0.0006510192850776011
/gps/hist/point 1438.362216641378 0.0006376329616915154
/gps/hist/point 1453.2281357037396 0.0006492030502463146
/gps/hist/point 1468.0940547661012 0.0006363548705139601
/gps/hist/point 1482.9599738284626 0.0006541808790431466

second particle

####################

/gps/source/add 2

/gps/particle e+

/gps/ang/rot1 -1 0 0
/gps/ang/rot2 0 -1 0
/gps/ang/type beam1d
#/gps/ang/sigma_r 30 deg
/gps/ang/type iso
/gps/ang/mintheta 20 deg
/gps/ang/maxtheta 170 deg
/gps/ang/minphi 90 deg
/gps/ang/maxphi 90 deg

/gps/position 50 50 -230 cm
/gps/pos/type Volume
/gps/pos/shape Para
/gps/pos/halfx 25 cm
/gps/pos/halfy 1 cm
/gps/pos/halfz 60 cm

/gps/ene/type Lin
/gps/ene/gradient 0.0
/gps/ene/intercept 1.0
/gps/ene/min 11.23 MeV
/gps/ene/min 49.49 MeV
/gps/ene/max 1599.49 MeV
/gps/ene/type User
/gps/hist/type energy

#Include here histogram for Kinetic Energy - Uniform momentum

/gps/hist/point 49.49383665355062 0.0006468406704648177
/gps/hist/point 64.99378966793877 0.0006428406583394619
/gps/hist/point 80.49374268232691 0.0006529697213020563
/gps/hist/point 95.99369569671506 0.0006447761480775369
/gps/hist/point 111.49364871110322 0.0006520019764330185
/gps/hist/point 126.99360172549137 0.0006367761238268262
/gps/hist/point 142.4935547398795 0.000649679388747328
/gps/hist/point 157.99350775426765 0.0006392277441617206
/gps/hist/point 173.4934607686558 0.0006466471214910098
/gps/hist/point 188.99341378304396 0.00063690515647603
/gps/hist/point 204.49336679743212 0.0006598729680345266
/gps/hist/point 219.99331981182024 0.0006449696970513444
/gps/hist/point 235.4932728262084 0.000642905174664064
/gps/hist/point 250.99322584059655 0.0006452922786743593
/gps/hist/point 266.49317885498465 0.000659808451709923
/gps/hist/point 281.9931318693728 0.0006412277502243985
/gps/hist/point 297.49308488376096 0.0006612278108511782
/gps/hist/point 312.9930378981491 0.0006482600296060726
/gps/hist/point 328.49299091253727 0.0006424535603918463
/gps/hist/point 343.9929439269254 0.0006477438990092526
/gps/hist/point 359.4928969413136 0.000640001940056953
/gps/hist/point 374.9928499557017 0.0006511632642131858
/gps/hist/point 390.4928029700898 0.0006395503257847331
/gps/hist/point 405.992755984478 0.0006459374419203821
/gps/hist/point 421.49270899886614 0.0006358728952823898
/gps/hist/point 436.9926620132543 0.0006469051867894199
/gps/hist/point 452.49261502764244 0.0006440664685069092
/gps/hist/point 467.9925680420306 0.0006425825930410537
/gps/hist/point 483.4925210564187 0.0006461955072187922
/gps/hist/point 498.99247407080685 0.000647292284737035
/gps/hist/point 514.492427085195 0.0006480019643076602
/gps/hist/point 529.9923800995832 0.0006492922907997152
/gps/hist/point 545.4923331139713 0.0006424535603918439
/gps/hist/point 560.9922861283595 0.0006537439171972889
/gps/hist/point 576.4922391427476 0.0006536148845480838
/gps/hist/point 591.9921921571357 0.0006384535482664881
/gps/hist/point 607.4921451715239 0.0006470987357632298
/gps/hist/point 622.992098185912 0.0006489051928520954
/gps/hist/point 638.4920512003002 0.0006458729255957819
/gps/hist/point 653.9920042146883 0.0006463890561925973
/gps/hist/point 669.4919572290765 0.000644001952182309
/gps/hist/point 684.9919102434646 0.0006436148542346939
/gps/hist/point 700.4918632578527 0.000649098741825903
/gps/hist/point 715.991816272241 0.0006567116681290046
/gps/hist/point 731.491769286629 0.0006440019521823043
/gps/hist/point 746.9917223010173 0.0006399374237323506
/gps/hist/point 762.4916753154054 0.0006438084032084968
/gps/hist/point 777.9916283297936 0.0006366470911776222
/gps/hist/point 793.4915813441817 0.000646130990894192
/gps/hist/point 808.9915343585698 0.0006421954950934339
/gps/hist/point 824.491487372958 0.0006371632217744424
/gps/hist/point 839.9914403873461 0.0006510342315639785
/gps/hist/point 855.4913934017343 0.0006395503257847355
/gps/hist/point 870.9913464161224 0.0006476793826846476
/gps/hist/point 886.4912994305106 0.0006438729195331039
/gps/hist/point 901.9912524448987 0.0006519374601084185
/gps/hist/point 917.4912054592868 0.0006414858155228062
/gps/hist/point 932.991158473675 0.0006465826051664096
/gps/hist/point 948.4911114880631 0.0006392922604863207
/gps/hist/point 963.9910645024513 0.0006479374479830624
/gps/hist/point 979.4910175168394 0.0006505181009671582
/gps/hist/point 994.9909705312276 0.0006408406522767857
/gps/hist/point 1010.4909235456157 0.0006483890622552753
/gps/hist/point 1025.990876560004 0.0006373567707482452
/gps/hist/point 1041.4908295743921 0.0006472277684124396
/gps/hist/point 1056.9907825887801 0.0006392277441617182
/gps/hist/point 1072.4907356031683 0.0006375503197220528
/gps/hist/point 1087.9906886175565 0.0006512922968623886
/gps/hist/point 1103.4906416319448 0.0006442600174807144
/gps/hist/point 1118.990594646333 0.0006356793463085892
/gps/hist/point 1134.490547660721 0.0006378729013450654
/gps/hist/point 1149.9905006751092 0.0006335503075966968
/gps/hist/point 1165.4904536894974 0.0006465180888418118
/gps/hist/point 1180.9904067038854 0.0006421309787688314
/gps/hist/point 1196.4903597182736 0.0006458729255957772
/gps/hist/point 1211.9903127326618 0.0006440019521823043
/gps/hist/point 1227.49026574705 0.0006555503742861641
/gps/hist/point 1242.990218761438 0.0006357438626331824
/gps/hist/point 1258.4901717758262 0.0006450342133759446
/gps/hist/point 1273.9901247902144 0.0006418729134704213
/gps/hist/point 1289.4900778046026 0.0006458729255957867
/gps/hist/point 1304.9900308189906 0.0006450987297005471
/gps/hist/point 1320.4899838333788 0.0006471632520878276
/gps/hist/point 1335.989936847767 0.0006360019279316019
/gps/hist/point 1351.489889862155 0.0006365180585284126
/gps/hist/point 1366.9898428765432 0.0006304535240157761
/gps/hist/point 1382.4897958909314 0.0006460664745695847
/gps/hist/point 1397.9897489053196 0.0006576148966734446
/gps/hist/point 1413.4897019197076 0.0006460664745695847
/gps/hist/point 1428.9896549340958 0.0006503245519933507
/gps/hist/point 1444.489607948484 0.0006516148784854106
/gps/hist/point 1459.989560962872 0.0006463245398679949
/gps/hist/point 1475.4895139772602 0.0006489697091766979
/gps/hist/point 1490.9894669916484 0.0006467761541402124
/gps/hist/point 1506.4894200060367 0.0006558084395845741
/gps/hist/point 1521.9893730204246 0.0006425180767164465
/gps/hist/point 1537.4893260348128 0.0006421954950934339
/gps/hist/point 1552.989279049201 0.0006429696909886735
/gps/hist/point 1568.489232063589 0.0006367116075022201
/gps/hist/point 1583.9891850779773 0.0006522600417314262

#/generator/add

#/generator/copy 0 1
#/run/beamOn 100000

/run/beamOn 1000

jrellin · December 21, 2025, 9:36pm

I’ll preface this with your are probably going to want to just write your own particle gun since gps is really limited to trying to constrain several parameters at once. With your macro so far, Id start with the following.

Add /gps/source/intensity 1.0 (or 0.5) after every /gps/source/add X
You can only have 1 angular type at a time so currently /gps/ang/type beam1d is overridden by /gps/ang/type iso
Same with energy /gps/ene/type User overrides /gps/ene/type Lin, /gps/ene/min 49.49 MeV overrides /gps/ene/min 11.23 MeV

There are also some conceptual issues here. Uniform momentum != uniform kinetic energy. From physics: | p | = sqrt(T (T + M)). But you can do that directly:

/gps/ene/type Arb
/gps/hist/type momentum
/gps/hist/point 100 MeV 1.0
/gps/hist/point 1500 MeV 1.0

GPS is not going to give you both 1d beam and angular sampling. The latter can be done with:

/gps/ang/type iso
/gps/ang/mintheta 20 deg
/gps/ang/maxtheta 170 deg
/gps/ang/minphi 0 deg
/gps/ang/maxphi 360 deg

Again the real answer is likely to be to just write your particle gun. It will be a bit of work but much more flexible given what you want to do here.