rivet as an experiment-theory interface for the heavy-ion

Rivet as an experiment-theory interfacefor the heavy-ion community

Przemek Karczmarczykfor the ALICE Collaboration

[email protected]

MPI@LHC, 18.11.2019

P. Karczmarczyk Rivet for heavy-ions 18.11.2019 1 / 16

Introduction

Introduction

Initial idea

Create an interface between experimental data and theoreticalpredictions for the heavy-ion community

� What do we have?

I Analyses (usually with finite acceptance, non-trivial cuts, non-trivialalgorithms of extracting physics objects, etc.)

I Data from different experiments published in papers (values usuallypublished in HepData)

I Large number of different Monte Carlo event generators

� What do we want?

I Test MC models by comparing their results to the experiment → RivetI Store the results in an easily accessible repository → MCPLOTS


Rivet

Rivet

� Rivet: Robust Independent Validation of Experiment and TheoryI Generator-independent analysis framework, arXiv:1003.0694I System for validation and tuning of event generatorsI Data & analysis algorithms preservation

� Rivet features:I Read input from HepMC format (file or FIFO)I Provides a large set of experimental analyses (currently over 400...)I Run one (or more) analyses on the input data from generatorI Fast and direct comparison between exp. data and generators

Example of Rivet results

Analysis coverage, source:https://rivet.hepforge.org/rivet-coverage


https://arxiv.org/abs/1003.0694

https://rivet.hepforge.org/rivet-coverage

Rivet

Rivet analysis

� Analyses as C++ classes

� To be written by users (analysers)

� Unique analysis identifier

I Consist of experiment name, year of publication, and Inspire ID codeI e.g. ALICE 2015 I1357424

� 3 core methods:

I init(): histograms booking, variables initialization...I analyze(...): main event loop, events are analysed and histograms are

filled hereI finalize(): histograms scaling, divisions for the final data comparison


Rivet

Rivet for heavy-ions

� Rivet originally developed for pp/pp̄ and e+e− physics

� But recently this has changed

I More interest from the heavy-ion communityI Possibility to use Rivet as a tool for HI analyses

� Most common HI features covered in Rivet 2.7 (see link)

� Rivet 2.7 released in 2019 with:

I Centrality calibration & selection using analysis optionsI Comparing and merging Rivet runs using reentrant finalize (e.g. for

AA/pp ratio)I Flow observables, event mixing frameworkI A set of 20+ analyses using heavy-ion features


https://rivet.hepforge.org

Rivet Centrality framework

Centrality framework in Rivet

� Centrality framework: allows an analysis to cut on percentiles ofsingle event quantities preloaded to that analysis

� Consist of:I A set of calibration analysesI Preloading calibration files as an input to the next runI Options for centrality to select the type of calibration to useI Centrality projection that allows to access centrality value

� Analysis options allow selection of centrality calibration method1 Calibration histogram from reference data2 Generated calibration histogram3 Impact parameter calibration histogram4 User-defined calibration histogram5 Generated centrality (available only with HepMC3)



Centrality calibration

� Calibration analysis used to produce calibration files

� Example analysis: ALICE 2015 PBPBCentrality

MC

0 5 10 15 20

10−3

10−2

10−1

b (fm)

(1/

Nev

t)d

N/

db

Impact parameter distribution

b

bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

b b b b b b b b b b bb b b b b b b b b b b b b b b b b

bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

b b b b bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

b b b b b bb b b b b b b b b b b b b

bbb b b b b b b bbb b b b b bb b b

b bbb

b b bbb b b b

b DataMC

0 5.0 ·103 1.0 ·104 1.5 ·104 2.0 ·104 2.5 ·104 3.0 ·104 3.5 ·104

10−6

10−5

10−4

10−3

10−2

10−1

1

V0M multiplicity distribution

� New preload flag to preload histograms to the Rivet runs



Centrality selection with analysis options

� Analysis options

I Possible to select by user at runtimeI Analysis can be run with different optionsI Centrality value accessible inside an analysis

b

b

b

b

b

b

bb

b

b DataMC [cent=IMP]MC [cent=GEN]

0

200

400

600

800

1.0 ·103

1.2 ·103

1.4 ·103

1.6 ·103

1.8 ·103

Nch vs. centrality, Pb–Pb√

sNN = 2.76 TeV

dN

ch/

dη

b b b b b b b b b

0 10 20 30 40 50 60 70 800.50.60.70.80.9

11.11.21.31.4

Centrality [%]

MC

/Dat

a

Example fromALICE 2010 I880049

b b b b b b b b b b b b b b b b b b b b b b b b b b bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb bb b

bb

b DataMC [cent=IMP]MC [cent=GEN]

10−4

10−3

10−2

10−1

1

10 1

10 2

Nch vs. p⊥, Centr = 40 − 60 %,√

sNN = 2.76 TeV

1/N

evt1

/(2

πp ⊥

)(d

2 Nch)/

(dη

dp ⊥

)[(

GeV

/c)

−2 ]

b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

1 10 10.50.60.70.80.9

11.11.21.31.4

p⊥ [GeV / c]

MC

/Dat

a


b

b bb

b DataEPOS-LHC

0

0.5

1

1.5

2

2.5

ICP (0-5% / 60-90%) near-side

I CP

(0-5

%/

60-9

0%)

b b b b

3 4 5 6 7 8 9 100.50.60.70.80.9

11.11.21.31.4

pt,assoc [GeV/c]

MC

/Dat

a



Rivet Reentrant finalize

Reentrant finalize

� Postprocessing implemented in a form of ’reentrant finalize’ methodI Analyses produce ’RAW’ histograms - saved in the output file before

calling finalize() methodI rivet-merge to call finalize() again, but this time with preloaded files

from previous runs to get final plotsI ’Reentrant’ flag to mark analyses using reentrant finalize method

Nuclear modification factor

RAA = dNAA/dpT<Ncoll>dNpp/dpT

b b b b b b b bb b

b b bb b b

b bb b b

b b b b b b b b b b b b b b bbbbb b b b b b b b

b bb bbbb b

b bbb b b

b b bb

b Dataoutput [cent=IMP]

10−1

1

RAA vs. p⊥, Centr = 0 − 20 %,√

sNN = 2.76 TeV

RA

Ab b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

1 10 10.50.60.70.80.9

11.11.21.31.4

p⊥ [GeV / c]

MC

/Dat

a

ALICE 2012 I1127497 example


Rivet Reentrant finalize

HI analyses list

With data:ALICE 2010 I880049 (PbPb): Multiplicity

ALICE 2012 I930312 (PbPb): IAA

ALICE 2012 I1127497 (PbPb): RAA

ALICE 2012 I1126966 (PbPb): π, K, p spectra

ALICE 2013 I1225979 (PbPb): Charged multiplicity

ALICE 2014 I1243865 (PbPb): Multi-strange baryons

ALICE 2014 I1244523 (pPb): Multi-strange baryons

ALICE 2015 PBPBCentrality (PbPb): Calibration


ALICE 2016 I1419244 (PbPb): Multiparticle correlations (flow)

ALICE 2016 I1471838 (pp): Multi-strange baryons


ALICE 2016 I1507157 (pp): Angular correlations

ATLAS 2015 I1360290 (PbPb): Charged multiplicity

ATLAS 2015 I1386475 (pPb): Charged multiplicity + spectra

ATLAS PBPB CENTRALITY (PbPb): Calibration

ATLAS pPb Calib (pPb): Calibration

BRAHMS 2004 I647076 (AuAu): π, K, p spectra as function of rapidity

STAR 2016 I1414638 (AuAu): Di-hadron correlations (flow)

CMS 2017 I1471287 (pp): Multiparticle correlations (flow)

LHCF 2016 I1385877 (pPb): Forward pT

Without data:ALICE 2015 PPCentrality: Calibration

BRAHMS 2004 CENTRALITY: Calibration

STAR BES CALIB: Calibration

MC Cent pPb Calib: Calibration example

MC Cent pPb Eta: Calibration example

MC OPTIONS: Analysis options example

MC REENTRANT: Reentrant finalize example

See list of all analyses here


https://rivet.hepforge.org/analyses.html

MCPLOTS project

MCPLOTS website

� MCPLOTS: a particle physics resource based onvolunteer computing

I The idea: enable anyone to quickly get an idea of howwell a particular model describes various data sets

I Automatize Rivet creation of comparison plotsI Online repository of plots: http://mcplots.cern.ch

[GeV]T

p

)T

dpη)/

(dch

N2)

(dT

pπ 2

ev1/

(N

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

ALICEHerwig++ (Def)Pythia 6 (Def)Pythia 8 (Def)Sherpa (Def)

900 GeV pp Soft QCD

mcp

lots

.cer

n.ch

4.1

M e

vent

s≥

Riv

et 2

.4.0

,

Herwig++ 2.7.1, Pythia 6.428, Pythia 8.212, Sherpa 2.2.0

ALICE_2010_S8706239

> 0.15 GeV)T

| < 0.8, pη Spectrum (|T

Charged Particle p

[GeV]T

p1 10

Rat

io to

ALI

CE

1

2

0.5

+20%

-20%

+10%

-10%

2×

-50%

+50%

[GeV]T

p

Tdpη

/dσ d

Tpπ 1

/2ev

1/N

9−10

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

1

10ATLASHerwig++ (Def)Pythia 6 (Def)Pythia 8 (Def)Sherpa (Def)

7000 GeV pp Soft QCD

mcp

lots

.cer

n.ch

4.9

M e

vent

s≥

Riv

et 2

.4.0

,

Herwig++ 2.7.1, Pythia 6.428, Pythia 8.212, Sherpa 2.2.0

ATLAS_2010_S8918562

> 2.5 GeV)T

> 1, pch

Spectrum (NT

Charged Particle p

[GeV]T

p10

Rat

io to

AT

LAS

1

2

0.5

+20%

-20%

+10%

-10%

2×

-50%

+50%


http://mcplots.cern.ch

MCPLOTS project

MCPLOTS for heavy-ions

� Originally provided results for pp and ee, but not for heavy-ions� New heavy-ion version of MCPLOTS

I Uses new Rivet version as a baselineI Enables to run analyses that use heavy-ion features described

� Integration ongoingI Preview version available here: http://mcplots-alice.cern.ch

Centrality [%]

η /

dch

dN

210

310

410

ALICEEpos (LHC)

2760 GeV PbPb Soft QCD

mcp

lots

.cer

n.ch

(ar

Xiv

:130

6.34

36)

10k

eve

nts

≥R

ivet

2.7

.0,

Epos 1.99.crmc.1.7.0-hi

ALICE_2010_I880049

> 0.05 GeV)T

| < 0.5, pη vs centrality (|η/dchdN

Centrality [%]0 20 40 60 80

Rat

io to

ALI

CE

1

2

0.5

2

0.5

1

η

η /

dch

dN

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

ALICEEpos (LHC)

2760 GeV PbPb Soft QCD

mcp

lots

.cer

n.ch

(ar

Xiv

:130

6.34

36)

10k

eve

nts

≥R

ivet

2.7

.0,

Epos 1.99.crmc.1.7.0-hi

ALICE_2013_I1225979 (UNVALIDATED)

| < 5.6, 0-5%)η distribution (|ηCharged particle

η5− 0 5

Rat

io to

ALI

CE

1

2

0.5

2

0.5

1


http://mcplots-alice.cern.ch

Summary

Summary

� Rivet

I Rivet 2.7 containing first heavy-ion features releasedI Already possible to calibrate analysis, use centrality, and obtain ratios

of AA/ppI Several heavy-ion analyses already included in the release

� MCPLOTS

I Adapted to the heavy-ion features available in the recent Rivet releaseI In the process of integration with the main MCPLOTS repository


Summary

What next?

� Continuation of development of the frameworksI More heavy-ion features (e.g. fitting)I More analyses coming in

� Integration of more HI generatorsI Currently available: Epos (LHC), Jewel, Pythia, ...I We need more of them!

� First framework is there: now we need more people working onanalyses integration

HI analysis coverage, source:https://rivet.hepforge.org/rivet-coverage-heavyiononly


https://rivet.hepforge.org/rivet-coverage-heavyiononly

Summary

References

� Rivet webpage: https://rivet.hepforge.org/

� Rivet user manual: https://arxiv.org/pdf/1003.0694.pdf

� Rivet source code: https://phab.hepforge.org/source/rivethg/

� MCPLOTS source code: https://gitlab.cern.ch/MCPLOTS/mcplots

� MCPLOTS webpage: http://mcplots.cern.ch/

� MCPLOTS HI development webpage: http://mcplots-alice.cern.ch


https://rivet.hepforge.org/

https://arxiv.org/pdf/1003.0694.pdf

https://phab.hepforge.org/source/rivethg/

https://gitlab.cern.ch/MCPLOTS/mcplots

http://mcplots.cern.ch/

http://mcplots-alice.cern.ch

Summary

Thank you!


Summary

Backup


Summary

More about Rivet

� Rivet features

I Provides a large set of experimental analyses (currently over 400...)useful for MC generator development, validation, and tuning

I Analyses correspond to the actual paper resultsI Analysis algorithms in object-oriented C++I Analysis code separated → easy way to add a new oneI Using the HepMC event format → independent of MC generatorsI Plotting based on YODA framework


Summary

HepMC & YODA

� HepMC:I Standarized event record library for High Energy Physics Monte Carlo

generators and simulationI A direct output of most of modern generatorsI File format contains information about final state particlesI Why? We need an interface between generator and analysis

� YODA (Yet more Objects for Data Analysis):

I A histogramming toolkit developed as a lightweightcommon system for MC event generator validationanalyses

I The core histogramming system in Rivet YODA logoP. Karczmarczyk Rivet for heavy-ions 18.11.2019 19 / 16

Summary

HI analysis chain

1 Calibration run:rivet -a ALICE_Calibration /path/to/PbPb.hepmc

2 Run with preloaded calibration file for PbPb beam:rivet -p /path/to/calib.yoda -a ALICE_2012_I123456:cent=IMP /path/to/PbPb.hepmc

3 Regular run for pp beam:rivet -a ALICE_2012_I123456:cent=IMP /path/to/pp.hepmc

4 Postprocessing with reentrant finalize:rivet -merge PbPb.yoda pp.yoda -o final.yoda


Summary

RAA analysis

b b b b b b b b b b b b b b b b b b b b b b b b b b bbbbbbbbbbbb

bbbbbbbbbbbbbbbbbbbb bbb bbbb

b Dataoutput [cent=IMP]

10−3

10−2

10−1

1

10 1

10 2

10 3

Nch vs. p⊥, Centr = 0 − 10 %,√

sNN = 2.76 TeV

1/N

evt1

/(2

πp ⊥

)(d

2 Nch)/

(dη

dp ⊥

)[(

GeV

/c)

−2 ]

b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

1 10 10.50.60.70.80.9

11.11.21.31.4

p⊥ [GeV / c]

MC

/Dat

a

(a) PbPb results

output [cent=IMP]

1 10 1

10−5

10−4

10−3

10−2

10−1

1

Nch vs. p⊥, Centr = 0 − 10 %,√

sNN = 2.76 TeV

p⊥ [GeV / c]

Nev

t1/(2

πp ⊥

)(d

2 Nch)/

(dη

dp ⊥

)[(

GeV

/c)

−2 ]

(b) pp reference

� Impact parameter distribution used for calibration� No HepMC data for pp reference� JEWEL does not provide Ncoll - that’s why the difference between

MC and experimental dataP. Karczmarczyk Rivet for heavy-ions 18.11.2019 21 / 16

Summary

RAA analysis

Nuclear modification factor

RAA = dNAA/dpT<Ncoll>dNpp/dpT

〈Ncoll〉 - average number of nucleon-nucleon collisions in a HI collisiondNAA/dpT - transverse momentum distribution in HI collision

dNpp/dpT - transverse momentum distribution in pp collision

� RAA tells how heavy-ion events looks like in scale of pp collisions

� Both pp and heavy-ion collisions are required to calculate RAA


Summary

MCPLOTS project

� The mcplots.cern.ch web siteI Simple online repository of plots made using RivetI with MC generators and comparisons to the experimental dataI Originally provides results for pp and ee, but not for heavy-ions

� Relies on:I The HEPDATA database of experimental resultsI The Rivet Monte Carlo analysis toolI MC event generators (currently implemented: ALPGEN, EPOS-LHC,

HERWIG++, PHOJET, PYTHIA 6, PYTHIA 8, SHERPA, VINCIA)I The LHC@HOME 2.0 framework for volunteer cloud computing


mcplots.cern.ch

rivet as an experiment-theory interface for the heavy-ion

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