1. LEMC Workshop, Fermilab, February 2007 Peter Skands Monte Carlo Event Generators for HEP Studies

2. Peter SkandsEvent Generator Status 2 ►Philosophy of this talk: Mail-order two (2) ACME muon guns  Physics Studies at the Interaction Point ►This talk is meant to give an update on HEP event generators, with special focus on μ + μ -  HEP μ-μ- μ+μ+ Physics at the IP = Primary Vertex

3. Peter SkandsEvent Generator Status 3 The Event Generator Position Collider Detector Reconstruction Framework Detailed Simulations prerequisite for: Serious physics studies Detector design studies Design reports …

4. Peter SkandsEvent Generator Status 4 The Monte Carlo Method Hard Part Hundreds of GeV  E cm Parton Showers Multi-GeV Hadron Decays Hadronizatio n ~ 1 GeV ~ 10 -15 m σ hard process, P res P ISR, P FSR P hadronization P decays

5. Peter SkandsEvent Generator Status 5 ►Starting observation: photon forward brems singularity is process- independent. Fundamental property of gauge theory  also applies to gluon brems. Leading contributions to both QED (photon radiation) & QCD (quark, gluon radiation) can be worked out to all orders once and for all  exponentiated (Altarelli-Parisi) integration kernels ►Iterative (Markov chain) formulation = parton shower can be used to generate the forward singular (“collinear”) parts of QED and QCD corrections to any process to infinite order in the coupling ordered in a measure of resolution  a series of successive factorizations the lower end of which can be matched to a hadronization description at some fixed low hadronization scale ►Limitations misses interference terms relevant in the deep non-singular region kinematic ambiguities and double counting between fixed order part and resummed part Bremsstrahlung: Parton Showers

6. Peter SkandsEvent Generator Status 6 Pre-LEP Event Generators ► “Seated on a tripod above a crack in the earth, she went into a trance by the stupefying vapors rising from the earth and by chewing laurel leaves. From the incoherent babbling which the priestess spoke in her ecstasy, the temple priests formulated the oracle.” ►There was a certain amount of voodoo involved ►Still, an impressive amount of data could be accounted for ►We now have much better voodoo The Pythia ►ARIADNE, HERWIG, and PYTHIA T. Sjöstrand, S. Mrenna, PS, JHEP 05 (2006) 026

7. Peter SkandsEvent Generator Status 7 Developments since LEP ►Hard Bremsstrahlung (additional jets, e.g. Z  3,4,5 jets) Parton shower approximation breaks down  large uncertainties Lots of progress in last ~ 5 years: “matching” to matrix elements ►Jet Broadening (soft/collinear parton bremsstrahlung) New generation of theoretical models Improved parton showers implemented in both general-purpose generators (HERWIG(++) and PYTHIA) + work here at Fermilab: VINCIA – a next-generation “antenna” shower ►The Final Femtometer – Hadronization With short-distance parts better under control  non-perturbative side has less wiggle room  also here improved possibility for studies Current studies at hadron colliders  feed back to lepton collider physics

8. Peter SkandsEvent Generator Status 8 VINCIA ►VINCIA Dipole shower C++ code for gluon showers – running Can evolve in either of 2 different shower evolution variables: pT-ordering (~ ARIADNE) Virtuality-ordering (~ Pythia 6.2 & SHERPA) For each evolution type, an infinite family of radiation functions implemented, all with correct collinear and soft behaviour (= “antenna functions”) ►First parton shower with systematic possibility of variation of shower variable and shower functon  control uncertainties ►To any fixed order, these variations can be absorbed by a new type of matching to matrix elements Dipoles – a dual description of QCD 1 3 2 virtual numerical collider with integrated antennae Giele, Kosower, PS : in progress

9. Peter SkandsEvent Generator Status 9 VINCIA Example: H  gg  ggg VINCIA 0.008 Unmatched “soft” |A| 2 VINCIA 0.008 Unmatched “hard” |A| 2 VINCIA 0.008 Matched “soft” |A| 2 VINCIA 0.008 Matched “hard” |A| 2 Expect public code and long writeup before summer Giele, Kosower, PS : in progress y 12 y 23 Later: plug-in for Pythia 8 ? Next: Quarks and leptons  lepton colliders y 12 ►First Branching ~ first order in perturbation theory ►Unmatched shower varied from “soft” to “hard” : soft shower has “radiation hole”. Filled in by matching. radiation hole in high-p T region

10. Peter SkandsEvent Generator Status 10 The Move to C++ (from F77) ►HERWIG++: complete reimplementation Improved parton shower and decay algorithms Eventually to include “CKKW”-style matching ? B.R. Webber; S. Gieseke, D. Grellscheid, A. Ribon, P. Richardson, M. Seymour, P. Stephens,... ►SHERPA: complete implementation, has CKKW matching ME generator + wrappers to / adaptations of PYTHIA, HERWIG F. Krauss; T. Fischer, T. Gleisberg, S. Hoeche, T. Laubrich, A. Schaelicke, S. Schumann, C. Semmling, J. Winter ►PYTHIA 8: selective reimplementation Improved PS and UE, limited number of hard subprocesses Many obsolete features not carried over  simpler, less parameters T. Sjöstrand, S. Mrenna, P. Skands

11. PYTHIA for the Muon Collider Instructive Examples

12. Peter SkandsEvent Generator Status 12 Event listing (summary) I particle/jet KS KF orig p_x p_y p_z E m 1 !mu+! 21 -13 0 0.000 0.000 750.000 750.000 0.106 2 !mu-! 21 13 0 0.000 0.000 -750.000 750.000 0.106 ======================================================================== ====== 3 !mu+! 21 -13 1 0.000 0.000 750.000 750.000 0.000 4 !mu-! 21 13 2 0.000 0.000 -750.000 750.000 0.000 5 !mu+! 21 -13 3 35.339 66.868 627.465 632.007 0.000 6 !mu-! 21 13 4 0.549 2.140 -388.502 388.509 0.000 7 !Z'0! 21 32 0 35.888 69.007 238.963 1020.516 989.090 8 !nu_e! 21 12 7 -162.336 -426.971 135.508 476.466 0.000 9 !nu_ebar! 21 -12 7 198.224 495.978 103.455 544.050 0.000 ======================================================================== ====== 10 (Z'0) 11 32 7 35.888 69.007 238.963 1020.516 989.090 11 gamma 1 22 3 -35.320 -66.793 108.367 132.107 0.000 12 gamma 1 22 4 0.514 -1.099 -16.725 16.769 0.000 13 gamma 1 22 4 -1.082 -1.115 -330.605 330.608 0.000 14 nu_e 1 12 8 -162.336 -426.971 135.508 476.466 0.000 15 nu_ebar 1 -12 9 198.224 495.978 103.455 544.050 0.000 16 gamma 1 22 1 0.000 0.000 0.000 0.000 0.000 17 gamma 1 22 2 0.000 0.000 0.000 0.000 0.000 ======================================================================== ====== sum: 0.00 0.000 0.000 0.000 1500.000 1500.000 Z’ Radiative Return ►Z’ with mass 1 TeV, with invisible decays (here neutrinos) ►MC running at 1.5 TeV. Radiative return via photon bremsstrahlung Beam Initial State (= beam + initial-state radiation) Final State (at Leading Order) Final State (after bremsstrahlung) Examples using PYTHIA 6.410 T. Sjöstrand, S. Mrenna, PS, JHEP 05 (2006) 026 http://projects.hepforge.org/pythia6/ Note: also handles full γ/Z 0 /Z’ 0 interference for SM channels Standard PC  ~ 1M evts / hr.

13. Peter SkandsEvent Generator Status 13 Event listing (summary) I particle/jet KS KF orig p_x p_y p_z E m 1 !mu+! 21 -13 0 0.000 0.000 60.000 60.000 0.106 2 !mu-! 21 13 0 0.000 0.000 -60.000 60.000 0.106 ======================================================================== ====== 3 !mu+! 21 -13 1 0.000 0.000 60.000 60.000 0.000 4 !mu-! 21 13 2 0.000 0.000 -60.000 60.000 0.000 5 !mu+! 21 -13 3 0.000 0.000 60.000 60.000 0.000 6 !mu-! 21 13 4 0.000 0.000 -60.000 60.000 0.000 7 !h0! 21 25 0 0.000 0.000 0.000 120.000 120.000 8 !b! 21 5 7 -27.886 6.281 52.534 60.000 4.800 9 !bbar! 21 -5 7 27.886 -6.281 -52.534 60.000 4.800 ======================================================================== ====== 10 (h0) 11 25 7 0.000 0.000 0.000 120.000 120.000 11 gamma 1 22 1 0.000 0.000 0.000 0.000 0.000 12 gamma 1 22 2 0.000 0.000 0.000 0.000 0.000 13 (ubar) A 12 -2 8 -0.243 -0.347 0.397 0.668 0.330 14 (g) I 12 21 8 0.173 -0.630 0.658 0.927 0.000 15 (g) I 12 21 8 -0.887 -0.091 1.462 1.712 0.000 16 (b) V 11 5 8 -9.565 10.722 44.056 46.587 4.800 17 (u) A 12 2 8 -12.758 -3.627 -0.934 13.300 0.330 18 (g) I 12 21 8 -1.441 -0.459 0.931 1.775 0.000 19 (g) I 12 21 9 0.620 0.004 -0.189 0.648 0.000 20 (g) I 12 21 9 -0.081 1.305 -1.532 2.014 0.000 21 (g) I 12 21 9 -0.101 0.355 -0.413 0.554 0.000 22 (g) I 12 21 9 0.773 -0.305 -0.065 0.834 0.000 23 (g) I 12 21 9 0.332 0.059 -0.228 0.407 0.000 24 (bbar) V 11 -5 9 23.177 -6.986 -44.142 50.572 4.800 ======================================================================== ====== 25 (string) 11 92 13 -10.522 9.654 46.573 49.895 10.799 26 (omega) 11 223 25 -0.253 -0.461 1.549 1.812 0.778 27 (pi0) 11 111 25 -0.480 -0.281 0.321 0.656 0.135 28 (pi0) 11 111 25 -1.442 2.077 7.957 8.350 0.135 29 (rho-) 11 -213 25 -1.077 1.453 5.978 6.291 0.754 30 (B*bar0) 11 -513 25 -7.270 6.866 30.767 32.786 5.325 31 (string) 11 92 17 10.522 -9.654 -46.573 70.105 50.416 32 (rho0) 11 113 31 -5.421 -1.084 -0.402 5.565 0.492 33 (K*+) 11 323 31 -4.307 -1.543 0.409 4.674 0.870 34 K- 1 -321 31 -1.770 -0.800 -0.443 2.052 0.494 35 p+ 1 2212 31 -2.323 -0.381 -0.291 2.551 0.938 36 (eta') 11 331 31 -0.351 0.200 0.439 1.128 0.958 37 (Deltabar-) 11 -2214 31 1.141 1.009 -1.561 2.513 1.248 38 pi+ 1 211 31 0.105 -0.415 -1.261 1.339 0.140 39 (rho-) 11 -213 31 5.155 -1.570 -8.550 10.137 0.790 40 pi+ 1 211 31 0.981 0.012 -2.262 2.469 0.140 41 (B0) 11 511 31 17.310 -5.083 -32.651 37.676 5.279 SM Higgs Factory Beam Initial State (= beam) Final State (at Leading Order) Final State (after bremsstrahlung) Legend: (g): gluon (u): quark A I I : colour chain I V Final State (after hadronization) Legend: (pi0): decayed hadron K- : undecayed hadron (string): hadronizing string Examples using PYTHIA 6.410 T. Sjöstrand, S. Mrenna, PS, JHEP 05 (2006) 026 http://projects.hepforge.org/pythia6/ Standard PC  ~ 1M evts / hr.

14. Peter SkandsEvent Generator Status 14 A 0 (from 2HDM) Event listing (summary) I particle/jet KS KF orig p_x p_y p_z 1 !mu+! 21 -13 0 0.000 0.000 300.000 2 !mu-! 21 13 0 0.000 0.000 -300.000 ======================================================== ==== 3 !mu+! 21 -13 1 0.000 0.000 300.000 4 !mu-! 21 13 2 0.000 0.000 -300.000 5 !mu+! 21 -13 3 0.000 0.000 300.000 6 !mu-! 21 13 4 0.000 0.001 -299.999 7 !A0! 21 36 0 0.000 0.001 0.001 8 !Z0! 21 23 7 -121.255 37.370 250.912 9 !h0! 21 25 7 121.255 -37.369 -250.911 10 !d! 21 1 8 -124.900 34.235 257.398 11 !dbar! 21 -1 8 3.645 3.135 -6.485 12 !tau-! 21 15 9 133.239 -9.141 -163.468 13 !tau+! 21 -15 9 -11.985 -28.227 -87.444 ======================================================== ==== 14 (A0) 11 36 7 0.000 0.001 0.001 15 gamma 1 22 4 0.000 -0.001 -0.001 16 (Z0) 11 23 8 -121.255 37.370 250.912 17 (h0) 11 25 9 121.255 -37.369 -250.911 18 (tau+) 11 -15 13 -11.983 -28.224 -87.433 19 (tau-) 11 15 12 131.583 -9.121 -161.287 20 gamma 1 22 12 1.655 -0.023 -2.192 23 (d) A 12 1 10 -86.461 23.971 171.287 24 (g) I 12 21 10 -20.973 4.898 39.060 25 (g) I 12 21 10 -4.846 1.556 10.350 26 (g) I 12 21 10 -2.985 1.077 6.514 27 (g) I 12 21 10 -1.208 0.094 11.716 28 (g) I 12 21 10 -1.148 0.894 3.534 29 (g) I 12 21 11 -0.829 -0.584 2.033 30 (g) I 12 21 11 -3.152 1.114 7.427 31 (g) I 12 21 11 -1.286 -0.891 2.165 32 (g) I 12 21 11 -0.322 -0.945 1.215 33 (g) I 12 21 11 -0.390 -0.326 -0.317 34 (g) I 12 21 11 0.284 0.117 0.004 35 (g) I 12 21 11 0.497 2.252 -0.578 36 (g) I 12 21 11 1.241 3.958 -3.508 37 (dbar) V 11 -1 11 0.324 0.184 0.009 ======================================================== ==== 38 nu_taubar 1 -16 18 -8.239 -19.736 -62.376 39 (rho+) 11 213 18 -3.745 -8.488 -25.057 40 nu_tau 1 16 19 0.376 -0.010 -0.335 41 (rho-) 11 -213 19 131.207 -9.111 -160.951 42 (string) 11 92 23 -121.255 37.370 250.912 43 (omega) 11 223 42 -54.820 14.763 107.817 H ++ (from LR Symmetry) Event listing (summary) I particle/jet KS KF orig p_x p_y p_z 1 !mu+! 21 -13 0 0.000 0.000 1000.000 2 !mu-! 21 13 0 0.000 0.000-1000.000 ============================================================ 3 !mu+! 21 -13 1 0.000 0.000 1000.000 4 !mu-! 21 13 2 0.000 0.000-1000.000 5 !mu+! 21 -13 3 0.097 0.092 991.468 6 !mu-! 21 13 4 0.000 0.000 -999.999 7 !H_L++! 21 9900041 0 622.421 -441.228 603.501 8 !H_L--! 21-9900041 0 -622.324 441.320 -612.033 9 !tau+! 21 -15 7 390.204 -216.443 455.416 10 !tau+! 21 -15 7 232.217 -224.785 148.085 11 !tau-! 21 15 8 -620.412 420.784 -541.234 12 !tau-! 21 15 8 -1.912 20.536 -70.799 ============================================================ 13 (H_L++) 11 9900041 7 622.421 -441.228 603.501 14 (H_L--) 11-9900041 8 -622.324 441.320 -612.033 15 gamma 1 22 3 -0.097 -0.092 8.530 16 gamma 1 22 3 0.000 0.000 0.002 17 (tau-) 11 15 11 -620.412 420.784 -541.234 18 (tau-) 11 15 12 -1.912 20.536 -70.799 19 (tau+) 11 -15 9 390.194 -216.438 455.405 20 (tau+) 11 -15 10 226.721 -219.279 144.594 21 gamma 1 22 10 5.506 -5.511 3.502 22 gamma 1 22 1 0.000 0.000 0.000 23 gamma 1 22 2 0.000 0.000 0.000 ============================================================ 24 nu_tau 1 16 17 -348.492 235.606 -302.953 25 pi- 1 -211 17 -271.921 185.179 -238.281 26 nu_tau 1 16 18 -0.933 4.425 -15.491 27 pi- 1 -211 18 -0.214 3.391 -10.885 28 (rho0) 11 113 18 -0.765 12.720 -44.422 29 nu_taubar 1 -16 19 101.142 -55.537 116.914 30 pi+ 1 211 19 289.052 -160.900 338.491 31 nu_e 1 12 20 3.975 -3.877 2.430 32 e+ 1 -11 20 216.486 -209.065 137.898 33 nu_taubar 1 -16 20 6.260 -6.337 4.267 34 pi- 1 -211 28 -0.794 12.176 -42.192 35 pi+ 1 211 28 0.029 0.544 -2.230 ============================================================ sum: 0.00 0.000 0.000 0.000 Examples using PYTHIA 6.410 T. Sjöstrand, S. Mrenna, PS, JHEP 05 (2006) 026 http://projects.hepforge.org/pythia6/

15. Peter SkandsEvent Generator Status 15Technicolor Event listing (summary) I particle/jet KS KF orig p_x p_y p_z E m 1 !mu+! 21 -13 0 0.000 0.000 1000.000 1000.000 0.106 2 !mu-! 21 13 0 0.000 0.000-1000.000 1000.000 0.106 ======================================================================== ====== 3 !mu+! 21 -13 1 0.000 0.000 1000.000 1000.000 0.000 4 !mu-! 21 13 2 0.000 0.000-1000.000 1000.000 0.000 5 !mu+! 21 -13 3 0.000 0.000 1000.000 1000.000 0.000 6 !mu-! 21 13 4 0.000 0.000-1000.000 1000.000 0.000 7 !pi_tc+! 21 3000211 0 330.799 -763.014 -241.681 1000.025 500.022 8 !pi_tc-! 21-3000211 0 -330.799 763.014 241.681 999.975 499.920 9 !u! 21 2 7 -63.162 -482.381 -111.969 499.218 0.330 10 !bbar! 21 -5 7 393.961 -280.633 -129.712 500.808 4.800 11 !ubar! 21 -2 8 44.437 520.715 107.332 533.516 0.330 12 !b! 21 5 8 -375.236 242.299 134.349 466.459 4.800 ======================================================================== ====== 13 (pi_tc+) 11 3000211 7 330.799 -763.014 -241.681 1000.025 500.022 14 (pi_tc-) 11-3000211 8 -330.799 763.014 241.681 999.975 499.920 15 gamma 1 22 1 0.000 0.000 0.000 0.000 0.000 16 gamma 1 22 2 0.000 0.000 0.000 0.000 0.000 17 (u) A 12 2 9 -50.238 -373.883 -84.036 386.489 0.330 18 (g) I 12 21 9 -10.115 -94.777 -23.332 98.130 0.000 19 (g) I 12 21 9 -0.365 -1.610 -0.077 1.653 0.000 20 (g) I 12 21 9 -1.459 -5.564 0.547 5.778 0.000 21 (g) I 12 21 9 0.991 -6.413 -5.097 8.252 0.000 22 (g) I 12 21 9 1.065 -1.928 -0.883 2.373 0.000 23 (g) I 12 21 10 0.511 -1.018 -0.464 1.230 0.000 24 (g) I 12 21 10 0.608 -0.218 -0.132 0.659 0.000 25 (g) I 12 21 10 1.588 -0.970 -0.384 1.900 0.000 26 (g) I 12 21 10 13.555 -10.109 -4.320 17.453 0.000 27 (bbar) V 11 -5 10 374.657 -266.523 -123.505 476.108 4.800 28 (ubar) A 12 -2 11 15.212 201.143 42.628 206.173 0.330 29 (g) I 12 21 11 17.753 214.099 42.291 218.957 0.000 30 (g) I 12 21 11 9.279 104.465 21.247 107.007 0.000 31 (g) I 12 21 11 1.138 1.929 0.646 2.331 0.000 32 (g) I 12 21 11 -1.868 0.865 1.543 2.573 0.000 33 (g) I 12 21 12 -1.611 1.425 0.882 2.325 0.000 34 (g) I 12 21 12 -0.409 0.207 0.208 0.504 0.000 35 (g) I 12 21 12 -1.694 1.075 0.416 2.049 0.000 36 (b) V 11 5 12 -368.599 237.806 131.820 458.057 4.800 ======================================================================== ====== 37 (string) 11 92 17 330.799 -763.014 -241.681 1000.025 500.022 38 p+ 1 2212 37 -28.471 -214.162 -48.494 221.424 0.938 39 (rho+) 11 213 37 -6.754 -52.209 -11.786 53.955 0.925 40 pbar- 1 -2212 37 -16.097 -119.073 -27.000 123.156 0.938 41 (pi0) 11 111 37 -1.194 -13.408 -2.850 13.760 0.135 42 (pi0) 11 111 37 -2.712 -26.468 -6.257 27.333 0.135 43 (rho0) 11 113 37 -4.398 -33.030 -7.997 34.277 0.767 Technicolor Strawman model Lowest-lying bound states of lightest Techni-fermion doublet Can be used for studies of a wide range of non-perturbative New Physics models Topcolor, walking Technicolor, extended Technicolor, … Mrenna, Lane Phys.Rev.D67:115011,2003 Examples using PYTHIA 6.410 T. Sjöstrand, S. Mrenna, PS, JHEP 05 (2006) 026 http://projects.hepforge.org/pythia6/ Standard PC  ~ 250k evts / hr.

16. Peter SkandsEvent Generator Status 16 The Generator Outlook ►MC Generators in state of continuous development Not much done (yet) specifically for muon colliders, but what’s there is already pretty useful As physics studies pick up, interactions likely to foster more developments  more studies  more developments … ►Get yours today – it’s free  more precise, more reliable theoretical predictions μ-μ- μ+μ+ http://projects.hepforge.org/pythia6/