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Merged
cmsbuild merged 3 commits into from
Sep 25, 2023
Merged

Backport fixes for alphaS running #30

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60db869
Revert "Revert "change to 8240 in to handle high multiplicity bug""
mseidel42 Jun 19, 2023
482d318
Backport alphaS running fix from 8.309
mseidel42 Jun 19, 2023
5d98ef7
Make the alphaS fix optional
mseidel42 Jun 19, 2023
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2 changes: 1 addition & 1 deletion include/Pythia8/MultipartonInteractions.h
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Expand Up @@ -214,7 +214,7 @@ class MultipartonInteractions {
SIGMAMBLIMIT;

// Initialization data, read from Settings.
bool allowRescatter, allowDoubleRes, canVetoMPI, doPartonVertex;
bool allowRescatter, allowDoubleRes, canVetoMPI, doPartonVertex, alphaSfixRun;
int pTmaxMatch, alphaSorder, alphaEMorder, alphaSnfmax, bProfile,
processLevel, bSelScale, rescatterMode, nQuarkIn, nSample,
enhanceScreening, pT0paramMode;
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2 changes: 1 addition & 1 deletion include/Pythia8/SimpleSpaceShower.h
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Expand Up @@ -163,7 +163,7 @@ class SimpleSpaceShower : public SpaceShower {
bool doQCDshower, doQEDshowerByQ, doQEDshowerByL, useSamePTasMPI,
doWeakShower, doMEcorrections, doMEafterFirst, doPhiPolAsym,
doPhiPolAsymHard, doPhiIntAsym, doRapidityOrder, useFixedFacScale,
doSecondHard, canVetoEmission, hasUserHooks, alphaSuseCMW,
doSecondHard, canVetoEmission, hasUserHooks, alphaSuseCMW, alphaSfixRun,
singleWeakEmission, vetoWeakJets, weakExternal, doRapidityOrderMPI,
doMPI, doDipoleRecoil, doPartonVertex;
int pTmaxMatch, pTdampMatch, alphaSorder, alphaSnfmax, alphaEMorder,
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2 changes: 1 addition & 1 deletion include/Pythia8/SimpleTimeShower.h
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Expand Up @@ -179,7 +179,7 @@ class SimpleTimeShower : public TimeShower {
allowBeamRecoil, dampenBeamRecoil, recoilToColoured, useFixedFacScale,
allowRescatter, canVetoEmission, doHVshower, brokenHVsym,
globalRecoil, useLocalRecoilNow, doSecondHard, hasUserHooks,
singleWeakEmission, alphaSuseCMW, vetoWeakJets, allowMPIdipole,
singleWeakEmission, alphaSuseCMW, alphaSfixRun, vetoWeakJets, allowMPIdipole,
weakExternal, recoilDeadCone, doDipoleRecoil, doPartonVertex;
int pTmaxMatch, pTdampMatch, alphaSorder, alphaSnfmax, nGluonToQuark,
weightGluonToQuark, alphaEMorder, nGammaToQuark, nGammaToLepton,
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6 changes: 4 additions & 2 deletions include/Pythia8/StandardModel.h
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Expand Up @@ -28,15 +28,15 @@ class AlphaStrong {
AlphaStrong() : isInit(false), order(0), nfmax(),
Lambda3Save(0.), Lambda4Save(0.), Lambda5Save(0.), Lambda6Save(0.),
Lambda3Save2(0.), Lambda4Save2(0.), Lambda5Save2(0.), Lambda6Save2(0.),
scale2Min(0.), mc(0.), mb(0.), mt(0.), mc2(0.), mb2(0.), mt2(0.), useCMW(),
scale2Min(0.), mc(0.), mb(0.), mt(0.), mc2(0.), mb2(0.), mt2(0.), useCMW(), fixRunning(),
lastCallToFull(false), valueRef(0.), valueNow(0.), scale2Now(0.) {}

// Destructor.
virtual ~AlphaStrong() {}

// Initialization for given value at M_Z and given order.
virtual void init(double valueIn = 0.12, int orderIn = 1, int nfmaxIn = 6,
bool useCMWIn = false);
bool useCMWIn = false, bool fixRunningIn = false);

// Set flavour threshold values: m_c, m_b, m_t.
virtual void setThresholds(double mcIn, double mbIn, double mtIn) {
Expand Down Expand Up @@ -81,6 +81,8 @@ class AlphaStrong {

// CMW rescaling factors.
bool useCMW;
// Fix alphaS running (backported from 8.309)
bool fixRunning;
static const double FACCMW3, FACCMW4, FACCMW5, FACCMW6;

// Safety margins to avoid getting too close to LambdaQCD.
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6 changes: 6 additions & 0 deletions share/Pythia8/xmldoc/CouplingsAndScales.xml
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Expand Up @@ -43,6 +43,12 @@ not go to second order there is no strong reason to use this option,
but there is also nothing wrong with it.</option>
</modepick>

<flag name="SigmaProcess:alphaSfixRun" default="off">
<option value="off">Do not apply the fix for 2-loop running. </option>
<option value="on">Apply the fix for 2-loop running, backported from 8.309.
</option>
</flag>

<p/>
QED interactions are regulated by the <ei>alpha_electromagnetic</ei>
value at the <ei>Q^2</ei> renormalization scale of an interaction.
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6 changes: 6 additions & 0 deletions share/Pythia8/xmldoc/MultipartonInteractions.xml
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Expand Up @@ -99,6 +99,12 @@ not go to second order there is no strong reason to use this option,
but there is also nothing wrong with it.</option>
</modepick>

<flag name="MultipartonInteractions:alphaSfixRun" default="off">
<option value="off">Do not apply the fix for 2-loop running. </option>
<option value="on">Apply the fix for 2-loop running, backported from 8.309.
</option>
</flag>

<p/>
QED interactions are regulated by the <ei>alpha_electromagnetic</ei>
value at the <ei>pT^2</ei> scale of an interaction.
Expand Down
6 changes: 6 additions & 0 deletions share/Pythia8/xmldoc/SpacelikeShowers.xml
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Expand Up @@ -182,6 +182,12 @@ not go to second order there is no strong reason to use this option,
but there is also nothing wrong with it.</option>
</modepick>

<flag name="SpaceShower:alphaSfixRun" default="off">
<option value="off">Do not apply the fix for 2-loop running. </option>
<option value="on">Apply the fix for 2-loop running, backported from 8.309.
</option>
</flag>

<p/>
The CMW rescaling of <ei>Lambda_QCD</ei> (see the section on
<aloc href="StandardModelParameters">StandardModelParameters</aloc>)
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6 changes: 6 additions & 0 deletions share/Pythia8/xmldoc/TimelikeShowers.xml
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Expand Up @@ -188,6 +188,12 @@ not go to second order there is no strong reason to use this option,
but there is also nothing wrong with it.</option>
</modepick>

<flag name="TimeShower:alphaSfixRun" default="off">
<option value="off">Do not apply the fix for 2-loop running. </option>
<option value="on">Apply the fix for 2-loop running, backported from 8.309.
</option>
</flag>

<p/>
The CMW rescaling of <ei>Lambda_QCD</ei> (see the section on
<aloc href="StandardModelParameters">StandardModelParameters</aloc>)
Expand Down
6 changes: 4 additions & 2 deletions src/MergingHooks.cc
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Expand Up @@ -2049,15 +2049,17 @@ void MergingHooks::init(){
// Initialise AlphaS objects for reweighting
double alphaSvalueFSR = settingsPtr->parm("TimeShower:alphaSvalue");
int alphaSorderFSR = settingsPtr->mode("TimeShower:alphaSorder");
bool alphaSfixRunFSR= settingsPtr->flag("TimeShower:alphaSfixRun");
int alphaSnfmax = settingsPtr->mode("StandardModel:alphaSnfmax");
int alphaSuseCMWFSR= settingsPtr->flag("TimeShower:alphaSuseCMW");
AlphaS_FSRSave.init(alphaSvalueFSR, alphaSorderFSR, alphaSnfmax,
alphaSuseCMWFSR);
alphaSuseCMWFSR, alphaSfixRunFSR);
double alphaSvalueISR = settingsPtr->parm("SpaceShower:alphaSvalue");
int alphaSorderISR = settingsPtr->mode("SpaceShower:alphaSorder");
bool alphaSfixRunISR= settingsPtr->flag("SpaceShower:alphaSfixRun");
int alphaSuseCMWISR= settingsPtr->flag("SpaceShower:alphaSuseCMW");
AlphaS_ISRSave.init(alphaSvalueISR, alphaSorderISR, alphaSnfmax,
alphaSuseCMWISR);
alphaSuseCMWISR, alphaSfixRunISR);

// Initialise AlphaEM objects for reweighting
int alphaEMFSRorder = settingsPtr->mode("TimeShower:alphaEMorder");
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3 changes: 2 additions & 1 deletion src/MultipartonInteractions.cc
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Expand Up @@ -385,6 +385,7 @@ bool MultipartonInteractions::init( bool doMPIinit, int iDiffSysIn,
// Parameters of alphaStrong generation.
alphaSvalue = settings.parm("MultipartonInteractions:alphaSvalue");
alphaSorder = settings.mode("MultipartonInteractions:alphaSorder");
alphaSfixRun = settings.flag("MultipartonInteractions:alphaSfixRun");
alphaSnfmax = settings.mode("StandardModel:alphaSnfmax");

// Parameters of alphaEM generation.
Expand Down Expand Up @@ -502,7 +503,7 @@ bool MultipartonInteractions::init( bool doMPIinit, int iDiffSysIn,
enhanceBavg = 1.;

// Initialize alpha_strong generation.
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, false);
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, false, alphaSfixRun);
double Lambda3 = alphaS.Lambda3();

// Initialize alphaEM generation.
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4 changes: 4 additions & 0 deletions src/Settings.cc
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Expand Up @@ -1839,6 +1839,7 @@ void Settings::resetTuneEE() {
// FSR: strong coupling, IR cutoff.
resetParm("TimeShower:alphaSvalue");
resetMode("TimeShower:alphaSorder");
resetFlag("TimeShower:alphaSfixRun");
resetFlag("TimeShower:alphaSuseCMW");
resetParm("TimeShower:pTmin");
resetParm("TimeShower:pTminChgQ");
Expand Down Expand Up @@ -1872,6 +1873,7 @@ void Settings::resetTunePP() {
// ISR: strong coupling, IR cutoff, coherence and spin correlations.
resetParm("SpaceShower:alphaSvalue");
resetMode("SpaceShower:alphaSorder");
resetParm("SpaceShower:alphaSfixRun");
resetParm("SpaceShower:alphaSuseCMW");
resetFlag("SpaceShower:samePTasMPI");
resetParm("SpaceShower:pT0Ref");
Expand All @@ -1886,6 +1888,8 @@ void Settings::resetTunePP() {

// MPI: strong coupling, IR regularization, energy scaling.
resetParm("MultipartonInteractions:alphaSvalue");
resetMode("MultipartonInteractions:alphaSorder");
resetParm("MultipartonInteractions:alphaSfixRun");
resetParm("MultipartonInteractions:pT0Ref");
resetParm("MultipartonInteractions:ecmRef");
resetParm("MultipartonInteractions:ecmPow");
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3 changes: 2 additions & 1 deletion src/SimpleSpaceShower.cc
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Expand Up @@ -135,12 +135,13 @@ void SimpleSpaceShower::init( BeamParticle* beamAPtrIn,
// Parameters of alphaStrong generation.
alphaSvalue = settingsPtr->parm("SpaceShower:alphaSvalue");
alphaSorder = settingsPtr->mode("SpaceShower:alphaSorder");
alphaSfixRun = settingsPtr->flag("SpaceShower:alphaSfixRun");
alphaSnfmax = settingsPtr->mode("StandardModel:alphaSnfmax");
alphaSuseCMW = settingsPtr->flag("SpaceShower:alphaSuseCMW");
alphaS2pi = 0.5 * alphaSvalue / M_PI;

// Initialize alpha_strong generation.
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, alphaSuseCMW);
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, alphaSuseCMW, alphaSfixRun);

// Lambda for 5, 4 and 3 flavours.
Lambda5flav = alphaS.Lambda5();
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19 changes: 12 additions & 7 deletions src/SimpleTimeShower.cc
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@@ -1,5 +1,5 @@
// SimpleTimeShower.cc is a part of the PYTHIA event generator.
// Copyright (C) 2018 Torbjorn Sjostrand.
// Copyright (C) 2019 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.

Expand Down Expand Up @@ -124,12 +124,13 @@ void SimpleTimeShower::init( BeamParticle* beamAPtrIn,
// Parameters of alphaStrong generation.
alphaSvalue = settingsPtr->parm("TimeShower:alphaSvalue");
alphaSorder = settingsPtr->mode("TimeShower:alphaSorder");
alphaSfixRun = settingsPtr->flag("TimeShower:alphaSfixRun");
alphaSnfmax = settingsPtr->mode("StandardModel:alphaSnfmax");
alphaSuseCMW = settingsPtr->flag("TimeShower:alphaSuseCMW");
alphaS2pi = 0.5 * alphaSvalue / M_PI;

// Initialize alphaStrong generation.
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, alphaSuseCMW);
alphaS.init( alphaSvalue, alphaSorder, alphaSnfmax, alphaSuseCMW, alphaSfixRun);

// Lambda for 5, 4 and 3 flavours.
Lambda3flav = alphaS.Lambda3();
Expand Down Expand Up @@ -3077,12 +3078,16 @@ bool SimpleTimeShower::branch( Event& event, bool isInterleaved) {
int iSysSelRec = dipSel->systemRec;

// Sometimes need to patch up colType in junction systems.
int idRec = recBef.id();
int colTypeTmp = dipSel->colType;
if (idRec > 0 && idRec < 9 && colTypeTmp > 0) colTypeTmp = -colTypeTmp;
if (idRec > -9 && idRec < 0 && colTypeTmp < 0) colTypeTmp = -colTypeTmp;
if (idRad > 0 && idRad < 9 && colTypeTmp < 0) colTypeTmp = -colTypeTmp;
if (idRad > -9 && idRad < 0 && colTypeTmp > 0) colTypeTmp = -colTypeTmp;
int colTypeRec = particleDataPtr->colType( recBef.id() );
// Negate colour type if recoiler is initial-state quark.
if (!recBef.isFinal()) colTypeRec = -colTypeRec;
int colTypeRad = particleDataPtr->colType( idRad );
// Perform junction tests for all colour (anti)triplets.
if (colTypeRec == 1 && colTypeTmp > 0) colTypeTmp = -colTypeTmp;
if (colTypeRec == -1 && colTypeTmp < 0) colTypeTmp = -colTypeTmp;
if (colTypeRad == 1 && colTypeTmp < 0) colTypeTmp = -colTypeTmp;
if (colTypeRad == -1 && colTypeTmp > 0) colTypeTmp = -colTypeTmp;
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@menglu21 menglu21 Jun 20, 2023

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I checked that we changed this part several time, e.g., 4311abd, do we need to change it back

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@mseidel42 mseidel42 Jun 20, 2023

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Yes, this is the multiplicity bug fix, @agrohsje reminded me that it needs to be included.

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@agrohsje agrohsje Jun 20, 2023

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@menglu21 we first fixed, then re-introduced the bug for testing releases. the buggy version stayed in the code but the fixed version was picked up in cmsdist. now that we are changing the code we need to fix again.

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@menglu21 menglu21 Jun 22, 2023

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I see, thanks


// Default OK for photon, photon_HV or gluon_HV emission.
if (dipSel->flavour == 22 || dipSel->flavour == idHV) {
Expand Down
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