Difference: PDFSystematicsStudy (1 vs. 19)

Revision 192012-07-10 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 15 to 15
 Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine hadronic cross sections of processes in proton-proton collisions according to the formula,

%\[

Changed:
<
<
\sigma^{pp\rightarrow X,Y,...}(...)=\sum_{i_A,j_B=q(g),\bar{q}(g)} \int dx_1dx_2 f^A_i(x_1,Q^2) f^B_j(x_2,Q^2)\sigma^{i_A j_B \rightarrow X,Y,...}(x_1,x_2,\alpha_s,...).
>
>
\sigma^{pp\rightarrow X,Y,...}(...)=\sum_{i_A,j_B=q(g),\bar{q}(g)} \int dx_1dx_2 f^A_i(fl_1,x_1,Q^2) f^B_j(fl_2,x_2,Q^2)\sigma^{i_A j_B \rightarrow X,Y,...}(x_1,x_2,\alpha_s,...).
 \]%
Changed:
<
<
where $\sigma^{i_aj_B\rightarrow X,Y}$ is a parton-parton cross section induced by $i_A$-th and $j_B$-th partons interaction in incoming protons A and B, respectively, $f_i^A(...)$ and $f_j^B(...)$ are $i$-th and $j$-th parton distribution functions (PDF) in the A-th and B-th protons, correspondingly, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.
>
>
where $\sigma^{i_aj_B\rightarrow X,Y}$ is a parton-parton cross section induced by $i_A$-th and $j_B$-th partons interaction in incoming protons A and B, respectively, $f_i^A(...)$ and $f_j^B(...)$ are $i$-th and $j$-th parton distribution functions (PDF) in the A-th and B-th protons, correspondingly, with $fl_1$ and $fl_2$ to be the flavor of the interacting partons, $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.
  Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we want to estimate the effect of a PDF change in the Pythia6 generator (used to produce signal samples) on a signal event selection efficiency.
Line: 35 to 35
 \epsilon^1 = \frac{N^1_{cuts}}{N^1_{gen}}, \]%
Changed:
<
<
where $N^1_{gen}$ is the total number of events generated be the generator before applying any cut and $N^1_{cuts}$ is the number of selected signal events after applying all selection criteria. If the event filter of an efficiency $\epsilon^1_{gen}$ is applied on the generator, then the event selection efficiency will look like
>
>
where $N^1_{gen}$ is the total number of events generated by the generator before applying any cut and $N^1_{cuts}$ is the number of selected signal events after applying all selection criteria. If an event filter of an efficiency $\epsilon^1_{gen}$ is applied on the generator, then the event selection efficiency will look like
  %\[ \epsilon^1 = \epsilon^1_{gen} \frac{N^1_{cuts}}{N^1_{gen}}.
Line: 44 to 44
 Now, had these events been generated with the same generator but using another PDF (call it PDF2) then the relative probability of producing a particular event $e_i$ as a result of an interaction of two partons with the same flavor, momentum fraction and energy scale, as in the case of using the PDF1, will be defined, as it is obvious from the formula above, by the relative PDFs weight, $w^i$, defined as

%\[

Changed:
<
<
w^i=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)}.
>
>
w^i=\frac{f_{PDF2}(fl_1,x_1,Q^2)}{f_{PDF1}(fl_1,x_1,Q^2)} \times \frac{f_{PDF2}(fl_2,x_2,Q^2)}{f_{PDF1}(fl_2,x_2,Q^2)}.
 \]%

Now the $N^2_{cuts}$ and $N^2_{gen}$ for the PDF2 will be defined as $N^2_{cuts} = \sum^{N^1_{cuts}}_{i=1}w^i $ and $N^2_{gen} = \sum^{N^1_{gen}}_{i=1}w^i $ and the event selection efficiency would look like

Line: 55 to 55
  The generator filter efficiencies $\epsilon^1_{gen}$ and $\epsilon^2_{gen}$ have to be determined by separate runs of the generator with the both PDFs, PDF1 and PDF2.
Changed:
<
<
So, the role of the PDF reweighting tool is to extract the PDF info, $f_{PDF1}(f_1,x_1,Q^2)$ and $f_{PDF1}(f_2,x_2,Q^2)$, from the available sample(s), extract the new PDF info,$f_{PDF2}(f_1,x_1,Q^2)$ and $f_{PDF2}(f_2,x_2,Q^2)$, from a new PDF set (one can go here for that http://lhapdf.hepforge.org/pdfsets ), calculate the relative event weight, $w^i$ and apply this weight to every single event in the sample to be reweighted. For this purpose one can use the tools mentioned below.
>
>
So, the role of the PDF reweighting tool is to:
  • extract the PDF info, $f_{PDF1}(f_1,x_1,Q^2)$ and $f_{PDF1}(f_2,x_2,Q^2)$, from the available sample(s);
  • extract the new PDF info,$f_{PDF2}(f_1,x_1,Q^2)$ and $f_{PDF2}(f_2,x_2,Q^2)$, from a new PDF set (one can go here for that http://lhapdf.hepforge.org/pdfsets );
  • calculate the relative event weight, $w^i$.

Applying of the weights to the events in the sample(s) to be reweighted is usually not done withing the PDF-reweighting tool, it is a business of the person who does the reweighting.

From the technical point of view there are three (ATLAS??) tools available to implement PDF-reweighting method, which can be found following the links:

Some additional relevant info on the re-weighing method you can get from

In our analysis for PDF reweighting we use TopPdfUncertainty tool from the Top group.

 

Direct method

Revision 182012-07-08 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

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  This page is under construction
Changed:
<
<
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming from a choice of parton distribution functions (PDF) in the Pythia6 generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks, b' and t'.
>
>
This Twiki-page is to give some more or less detailed information about the analysis to estimate systematic uncertainties coming from a choice of parton distribution functions (PDF) in the Pythia6 generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks, b' and t'.
 

Introduction

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 \sigma^{pp\rightarrow X,Y,...}(...)=\sum_{i_A,j_B=q(g),\bar{q}(g)} \int dx_1dx_2 f^A_i(x_1,Q^2) f^B_j(x_2,Q^2)\sigma^{i_A j_B \rightarrow X,Y,...}(x_1,x_2,\alpha_s,...). \]%
Changed:
<
<
where $\sigma^{i_aj_B\rightarrow X,Y}$ is a parton-parton cross section induced by $i_A$-th and $j_B$-th partons interaction in incoming protos A and B, respectively, $f_i^A(...)$ and $f_j^B(...)$ are $i$-th and $j$-th parton distribution functions (PDF) in the A-th and B-th protons, correspondingly, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.
>
>
where $\sigma^{i_aj_B\rightarrow X,Y}$ is a parton-parton cross section induced by $i_A$-th and $j_B$-th partons interaction in incoming protons A and B, respectively, $f_i^A(...)$ and $f_j^B(...)$ are $i$-th and $j$-th parton distribution functions (PDF) in the A-th and B-th protons, correspondingly, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.
  Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we want to estimate the effect of a PDF change in the Pythia6 generator (used to produce signal samples) on a signal event selection efficiency.

Analysis methods

Changed:
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Our analysis to estimate PDF uncerntainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined.
>
>
Our analysis to estimate PDF uncertainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined.
 

Reweighting method

Line: 35 to 35
 \epsilon^1 = \frac{N^1_{cuts}}{N^1_{gen}}, \]%
Changed:
<
<
where $N^1_{gen}$ is the total number of events generated be the generator before applying any cut and $N^1_{cuts}$ is the number of selected signal events after applying all selection criteria. If the event filter of an efficiency $\epsilon^1_{gen}$ is applied on the generator, then the event selection efficienly will look like
>
>
where $N^1_{gen}$ is the total number of events generated be the generator before applying any cut and $N^1_{cuts}$ is the number of selected signal events after applying all selection criteria. If the event filter of an efficiency $\epsilon^1_{gen}$ is applied on the generator, then the event selection efficiency will look like
  %\[
Changed:
<
<
\epsilon^1 = \epsilon^1_{gen} \frac{N^1_{cuts}}{N^1_{gen}},
>
>
\epsilon^1 = \epsilon^1_{gen} \frac{N^1_{cuts}}{N^1_{gen}}.
 \]%
Changed:
<
<
Now, had these events been generated with the same generator but using another PDF (call it PDF2) then the relativer probabality of producing a particular event $e_i$ as a result of an interaction of two partons with the same flavor, momentum fraction and energy scale, as in the case of using the PDF1, will be defined, as it is obvious from the formula above, by the relative PDFs weight, $w_i$, defined as
>
>
Now, had these events been generated with the same generator but using another PDF (call it PDF2) then the relative probability of producing a particular event $e_i$ as a result of an interaction of two partons with the same flavor, momentum fraction and energy scale, as in the case of using the PDF1, will be defined, as it is obvious from the formula above, by the relative PDFs weight, $w^i$, defined as
  %\[ w^i=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)}.
Line: 50 to 50
 Now the $N^2_{cuts}$ and $N^2_{gen}$ for the PDF2 will be defined as $N^2_{cuts} = \sum^{N^1_{cuts}}_{i=1}w^i $ and $N^2_{gen} = \sum^{N^1_{gen}}_{i=1}w^i $ and the event selection efficiency would look like

%\[

Changed:
<
<
\epsilon^2 = \epsilon^2_{gen} \frac{ \sum^{N^1_{cuts}}_{i=1}w^i }{ \sum^{N^1_{gen}}_{i=1}w^i}.
>
>
\epsilon^2 = \epsilon^2_{gen} \frac{N^2_{cuts}}{N^2_{gen}} = \epsilon^2_{gen} \frac{ \sum^{N^1_{cuts}}_{i=1}w^i }{ \sum^{N^1_{gen}}_{i=1}w^i}.
 \]%
Changed:
<
<
The generator filter efficiences $\epsilon^1_{gen}$ and $\epsilon^2_{gen}$ have to be determined by separate runs of the generator with the both PDFs, PDF1 and PDF2.
>
>
The generator filter efficiencies $\epsilon^1_{gen}$ and $\epsilon^2_{gen}$ have to be determined by separate runs of the generator with the both PDFs, PDF1 and PDF2.
  So, the role of the PDF reweighting tool is to extract the PDF info, $f_{PDF1}(f_1,x_1,Q^2)$ and $f_{PDF1}(f_2,x_2,Q^2)$, from the available sample(s), extract the new PDF info,$f_{PDF2}(f_1,x_1,Q^2)$ and $f_{PDF2}(f_2,x_2,Q^2)$, from a new PDF set (one can go here for that http://lhapdf.hepforge.org/pdfsets ), calculate the relative event weight, $w^i$ and apply this weight to every single event in the sample to be reweighted. For this purpose one can use the tools mentioned below.

Direct method

In the Direct method one has to generate new signal event samples including into a generator not only other PDF(s) (different from the default one) but also tunes corresponding to these new PDF(s) to account for Underlying Event(UE), which in generator in general depends on the PDF used to run the generator and after to go through the whole chain of the sample production, i.e. simulation, digitization, reconstruction and production of D3PDs for the final analysis.

Changed:
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<
The advantige of this method over re-weighting is that in this case one counts for the possible effects coming from UE, in contrast to the previous method. On the other hand, the main disadvantige of this method is, it's time and cpu consuming.
>
>
The advantage of this method over re-weighting is that in this case one counts for the possible effects coming from UE, in contrast to the previous method. On the other hand, the main disadvantage of this method is, it's time and cpu consuming.
 

PDFs and tunes

Changed:
<
<
This PDF systematic uncerntainty study is done using MC samples produced within MC11b ATLAS production setup. In this production MC samples generated with Pythia6 generator have been obtained using MRST LO** (20651) as the default PDF along with its recent "ATLAS Underlying Event Tune 2B" (AUET2B) tune.
>
>
This PDF systematic uncertainty study is done using MC samples produced within MC11b ATLAS production setup. In this production MC samples generated with Pythia6 generator have been obtained using MRST LO** (20651) as the default PDF along with its recent "ATLAS Underlying Event Tune 2B" (AUET2B) tune.
  In the both methods outlined above we have used the following PDFs to estimate the uncerntainty:
  • CTEQ6L1 (10042) - LO with LO alpha_s;
Line: 79 to 79
  Pythia6 parameters tuned in the the AUET2B tuning campain are as follows:
Changed:
<
<
Paremeters PARP(62), PARP(64) and PARP(72) are responsible for shower parameterization, namely,
>
>
Paremeters PARP(62), PARP(64) and PARP(72) are responsible for shower parametrization, namely,
 
  • PARP(62) defines an initial state radiation (ISR) $p_T$ cut-off;
  • PARP(64) - ISR scale factor on $\alpha_S$ evaluation scale and;
  • PARP(72) is $\Lambda_{QCD}$ for FSR showering from ISR parton emissions.
Line: 109 to 109
  Samples:
Changed:
<
<
The following samples have been used to get default efficiences (i.e. with default MRST LO** PDF) for both direct and re-weighting methods as well as used in the re-weighting method to get shifted efficiences:
>
>
The following samples have been used to get default efficiencies (i.e. with default MRST LO** PDF) for both direct and re-weighting methods as well as used in the re-weighting method to get shifted efficiencies:
  Mass point of 400 GeV:
  • mc11_7TeV.119314.Pythia_d4PairToWtWtbar_400_1LepIncl.merge.NTUP_TOP.e972_s1310_s1300_r3043_r2993_p834
Line: 129 to 129
  To implement this method we use default signal heavy b' ?? samples to re-weight them.
Changed:
<
<
From the technical point of view there are three ATLAS? tools available to implement PDF-reweighting methog, which can be found following the links:
>
>
From the technical point of view there are three ATLAS? tools available to implement PDF-reweighting method, which can be found following the links:
 

Revision 172012-07-06 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

<!--optional-->
Changed:
<
<
This page is under construction and contains no useful information yet
>
>
This page is under construction
  This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming from a choice of parton distribution functions (PDF) in the Pythia6 generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks, b' and t'.

Introduction

Changed:
<
<
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we want to estimate the effect of a PDF change in the Pythia6 generator to produce signal samples on a signal event selection efficiency.
>
>
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine hadronic cross sections of processes in proton-proton collisions according to the formula,

\[ \sigma^{pp\rightarrow X,Y,...}(...)=\sum_{i_A,j_B=q(g),\bar{q}(g)} \int dx_1dx_2 f^A_i(x_1,Q^2) f^B_j(x_2,Q^2)\sigma^{i_A j_B \rightarrow X,Y,...}(x_1,x_2,\alpha_s,...). \]

where $\sigma^{i_aj_B\rightarrow X,Y}$ is a parton-parton cross section induced by $i_A$-th and $j_B$-th partons interaction in incoming protos A and B, respectively, $f_i^A(...)$ and $f_j^B(...)$ are $i$-th and $j$-th parton distribution functions (PDF) in the A-th and B-th protons, correspondingly, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.

Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we want to estimate the effect of a PDF change in the Pythia6 generator (used to produce signal samples) on a signal event selection efficiency.

 

Analysis methods

Line: 21 to 29
 

Reweighting method

Changed:
<
<
Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, $x_{flav1}$, $x_{flav2}$, according to a second PDF set, PDF2, at the same energy scale $Q$, then evaluating the following ratio
>
>
Suppose, we have MC signal events generated using PDF1 in a generator. If we apply selection cuts to these events, then the signal event selection efficiency, $\epsilon^1$, by definition is,

\[ \epsilon^1 = \frac{N^1_{cuts}}{N^1_{gen}}, \]

where $N^1_{gen}$ is the total number of events generated be the generator before applying any cut and $N^1_{cuts}$ is the number of selected signal events after applying all selection criteria. If the event filter of an efficiency $\epsilon^1_{gen}$ is applied on the generator, then the event selection efficienly will look like

  %\[
Changed:
<
<
EW=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)}
>
>
\epsilon^1 = \epsilon^1_{gen} \frac{N^1_{cuts}}{N^1_{gen}},
 \]%
Changed:
<
<
After the EventWeight, $EW$, is applied on MC events generated with PDF1 and then they will effectively be distributed according to PDF2.
>
>
Now, had these events been generated with the same generator but using another PDF (call it PDF2) then the relativer probabality of producing a particular event $e_i$ as a result of an interaction of two partons with the same flavor, momentum fraction and energy scale, as in the case of using the PDF1, will be defined, as it is obvious from the formula above, by the relative PDFs weight, $w_i$, defined as
 
Added:
>
>
\[ w^i=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)}. \]
 
Added:
>
>
Now the $N^2_{cuts}$ and $N^2_{gen}$ for the PDF2 will be defined as $N^2_{cuts} = \sum^{N^1_{cuts}}_{i=1}w^i $ and $N^2_{gen} = \sum^{N^1_{gen}}_{i=1}w^i $ and the event selection efficiency would look like

\[ \epsilon^2 = \epsilon^2_{gen} \frac{ \sum^{N^1_{cuts}}_{i=1}w^i }{ \sum^{N^1_{gen}}_{i=1}w^i}. \]
 
Added:
>
>
The generator filter efficiences $\epsilon^1_{gen}$ and $\epsilon^2_{gen}$ have to be determined by separate runs of the generator with the both PDFs, PDF1 and PDF2.
 
Added:
>
>
So, the role of the PDF reweighting tool is to extract the PDF info, $f_{PDF1}(f_1,x_1,Q^2)$ and $f_{PDF1}(f_2,x_2,Q^2)$, from the available sample(s), extract the new PDF info,$f_{PDF2}(f_1,x_1,Q^2)$ and $f_{PDF2}(f_2,x_2,Q^2)$, from a new PDF set (one can go here for that http://lhapdf.hepforge.org/pdfsets ), calculate the relative event weight, $w^i$ and apply this weight to every single event in the sample to be reweighted. For this purpose one can use the tools mentioned below.
 

Direct method

Revision 162012-06-19 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Revision 152012-02-19 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 72 to 72
 
Added:
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>

Sample Production

 
Changed:
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Sample Production

MC11b

Within the official production campain the 4th generation quark samples (b' and t') are produced using the tags combination - e972_s1310_s1300_r3043_r2993_p834. Thus, to perform this study samples have been produced privately and following official production setup as closely as possible.

>
>
MC signal samples (4th generation b' quark pair production) used in this study have been produced with ATLAS MC production setup MC11c using the tags combination - e972_s1310_s1300_r3043_r2993_p834. The samples have been produced privately and following official production instructions.
  Athena releases used for different production steps are the following:
Changed:
<
<
  • Event generation AtlasProduction, 16.6.8.2 (tag - e972);
  • G4 simulation AtlasProduction, 16.6.7.13 (tag - s1310);
  • Digitization and Reconst AtlasProduction, 17.0.5.1 (tag - r3043);
>
>
  • Event generation AtlasProduction, 16.6.6.3 - 16.6.7.X (tag - e972);
  • G4 simulation AtlasProduction, 15.6.6.3 - 16.6.7.X (tag - s1310, merging - s1300);
  • Digitization and Reconst AtlasProduction, 17.0.5.6 and newer (tag - r3043, merging - r2993);
 
  • TopD3PD production - AtlasPhysics, 17.0.5.6.1 (tag - p834);
Changed:
<
<
For more information on the MC11b production setup have a look at the following links:
>
>
For more information on the MC11 production setup have a look at the link.
 
Changed:
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<

MC11c

>
>
Samples:
 
Changed:
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The difference in MC11b and MC11c productions mainly comes from the usage of Pythia6 pileup setup in MC11c instead of Pythia8 in MC11b. In terms of production setup details the difference comes in Digitization and Reconst steps. The Athena release used for this step is:
  • Digitization and Reconst AtlasProduction, 17.0.5.6 and newer;
>
>
The following samples have been used to get default efficiences (i.e. with default MRST LO** PDF) for both direct and re-weighting methods as well as used in the re-weighting method to get shifted efficiences:
 
Changed:
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<
For details on the MC11c production, go to
>
>
Mass point of 400 GeV:
  • mc11_7TeV.119314.Pythia_d4PairToWtWtbar_400_1LepIncl.merge.NTUP_TOP.e972_s1310_s1300_r3043_r2993_p834
Mass point of 500 GeV:
  • user.mandry.MC11.115114.Pythia_d4PairToWtWtbar_500_1LepIncl.ntup_top.s130_r3043_p834.17.01.2012/
 
Changed:
<
<

Inclusion of the PDFs into a JO file

>
>
Next samples have been produced with non-default PDFs listed above and used to extract efficiency shifts for the corresponding PDFs for the mass point of b' of 500 GeV:
  • user.mandry.MC11.100001.Pythia_d4PairToWtWtbar_500_1LepIncl_CTEQ6L1.ntup_top.s130_r3043_p834.24.01.2012/
  • user.mandry.MC11.100001.Pythia_d4PairToWtWtbar_500_1LepIncl_CT09MC2.ntup_top.s130_r3043_p834.24.01.2012/
  • user.mandry.MC11.100001.Pythia_d4PairToWtWtbar_500_1LepIncl_MSTW2008LO.ntup_top.s130_r3043_p834.24.01.2012/
  • user.mandry.MC11.100001.Pythia_d4PairToWtWtbar_500_1LepIncl_MRSTLOStar.ntup_top.s130_r3043_p834.24.01.2012/
 
Added:
>
>

Extraction of efficiencies

 
Changed:
<
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Reweighting method

>
>

Reweighting method

  To implement this method we use default signal heavy b' ?? samples to re-weight them.
Line: 118 to 118
  In our analysis for PDF reweighting we use TopPdfUncertainty tool from the Top group.
Changed:
<
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Samples used for the re-weighting are:

MC11b: mc11_7TeV.119314.Pythia_d4PairToWtWtbar_400_1LepIncl.merge.NTUP_TOP.e972_s1310_s1300_r3043_r2993_p834

MC11c:

Direct method

Validation of samples

Extracting efficiencies

Reweighting method

Direct method

Discussion of the results

Howtos

To read more on the subject, go to References.

Example:You may also directly contact P.Uwer to get the package.

b'b'bar->ttbar+WW (Panda link)

t't'bar -> WW+qqbar (q=b',d,s,b) (Panda link)

t't'bar -> WW+qqbar (q=d,s,b) (Panda link)

>
>

Direct method

 
Deleted:
<
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Below Top quark pair production cross sections in proton-proton (pp) and proton-antiproton (ppb) collisions calculated by this tool (in red) are compared with ones obtained from arXiv/hep-ph/0804.2800 (in blue). PDF errors are calculated in the asymmetric way. Cross sections are given in picobarns (pb).
 
Changed:
<
<
  • $\sigma_{NLO}$ (pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-100(scales) +30-29(PDFs)
  • CS_nlo(pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-101(scales)+30-29(PDFs)
>
>

Discussion of the results

Revision 142012-02-16 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 144 to 144
  To read more on the subject, go to References.
Changed:
<
<
Example:You may also directly contact P.Uwer or S.Moch to get the package.
>
>
Example:You may also directly contact P.Uwer to get the package.

b'b'bar->ttbar+WW (Panda link)

t't'bar -> WW+qqbar (q=b',d,s,b) (Panda link)

t't'bar -> WW+qqbar (q=d,s,b) (Panda link)

 

Revision 132012-02-04 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 92 to 92
 

MC11c

Changed:
<
<
The difference in MC11b and MC11c productions mainly comes from the usage of Pythia6 pileup setup in MC11c instead of Pythia8 in MC11b. In term of production setup details the difference comes in Digitization and Reconst steps like:
>
>
The difference in MC11b and MC11c productions mainly comes from the usage of Pythia6 pileup setup in MC11c instead of Pythia8 in MC11b. In terms of production setup details the difference comes in Digitization and Reconst steps. The Athena release used for this step is:
 
  • Digitization and Reconst AtlasProduction, 17.0.5.6 and newer;
Changed:
<
<
For the details on the MC11c production, go to
>
>
For details on the MC11c production, go to
 

Inclusion of the PDFs into a JO file

Line: 124 to 124
 mc11_7TeV.119314.Pythia_d4PairToWtWtbar_400_1LepIncl.merge.NTUP_TOP.e972_s1310_s1300_r3043_r2993_p834
Changed:
<
<
MC11b:
>
>
MC11c:
 

Direct method

Revision 122012-02-04 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 112 to 112
 
Changed:
<
<
Additional info on the re-weighing method you can get from
>
>
Some additional relevant info on the re-weighing method you can get from
 

In our analysis for PDF reweighting we use TopPdfUncertainty tool from the Top group.

Added:
>
>
Samples used for the re-weighting are:

MC11b: mc11_7TeV.119314.Pythia_d4PairToWtWtbar_400_1LepIncl.merge.NTUP_TOP.e972_s1310_s1300_r3043_r2993_p834

MC11b:

 

Direct method

Revision 112012-01-28 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 75 to 75
 

Sample Production

Added:
>
>

MC11b

 Within the official production campain the 4th generation quark samples (b' and t') are produced using the tags combination - e972_s1310_s1300_r3043_r2993_p834. Thus, to perform this study samples have been produced privately and following official production setup as closely as possible.

Athena releases used for different production steps are the following:

Line: 88 to 90
 
Added:
>
>

MC11c

The difference in MC11b and MC11c productions mainly comes from the usage of Pythia6 pileup setup in MC11c instead of Pythia8 in MC11b. In term of production setup details the difference comes in Digitization and Reconst steps like:

  • Digitization and Reconst AtlasProduction, 17.0.5.6 and newer;
 
Added:
>
>
For the details on the MC11c production, go to
 

Inclusion of the PDFs into a JO file

Revision 102012-01-23 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 46 to 46
 This PDF systematic uncerntainty study is done using MC samples produced within MC11b ATLAS production setup. In this production MC samples generated with Pythia6 generator have been obtained using MRST LO** (20651) as the default PDF along with its recent "ATLAS Underlying Event Tune 2B" (AUET2B) tune.

In the both methods outlined above we have used the following PDFs to estimate the uncerntainty:

Changed:
<
<
  • CTEQ6L1 (10042)
>
>
  • CTEQ6L1 (10042) - LO with LO alpha_s;
 
  • MSTW2008LO (21000)
  • MRST LO* (20650)
Changed:
<
<
  • CT09MC2 (10772)
>
>
  • CT09MC2 (10772) - 1-loop alphas; momentum sum rule violation;
 For more details on the PDFs go to LHAPDF.

Reason for choosing the above PDFs: MRST LO** is a LO PDF, so the above PDFs, chosen for the PDF systematics study, should also be of LO.

Revision 92012-01-20 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 22 to 22
 

Reweighting method

Changed:
<
<
Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio
>
>
Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, $x_{flav1}$, $x_{flav2}$, according to a second PDF set, PDF2, at the same energy scale $Q$, then evaluating the following ratio
  %\[ EW=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)}
Line: 98 to 98
  To implement this method we use default signal heavy b' ?? samples to re-weight them.
Added:
>
>
From the technical point of view there are three ATLAS? tools available to implement PDF-reweighting methog, which can be found following the links:

Additional info on the re-weighing method you can get from

In our analysis for PDF reweighting we use TopPdfUncertainty tool from the Top group.

 

Direct method

Validation of samples

Revision 82012-01-16 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Revision 72012-01-13 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 7 to 7
  This page is under construction and contains no useful information yet
Changed:
<
<
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming from a choice of parton distribution functions (PDF) in the generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks.
>
>
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming from a choice of parton distribution functions (PDF) in the Pythia6 generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks, b' and t'.
 

Introduction

Changed:
<
<
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we have tried to estimate the effect of a PDF change in a generator to produce signal samples on a signal event selection efficiency.
>
>
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we want to estimate the effect of a PDF change in the Pythia6 generator to produce signal samples on a signal event selection efficiency.
 
Deleted:
<
<
Our analysis to estimate PDF uncerntainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined as well as described how the analysis is done.
 

Analysis methods

Added:
>
>
Our analysis to estimate PDF uncerntainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined.
 

Reweighting method

Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio

Line: 39 to 40
 
Changed:
<
<

Realizations of the analysis methods

For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO** ) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.

This study is done in release 17 using MC11b-like production setup.

>
>

PDFs and tunes

 
Added:
>
>
This PDF systematic uncerntainty study is done using MC samples produced within MC11b ATLAS production setup. In this production MC samples generated with Pythia6 generator have been obtained using MRST LO** (20651) as the default PDF along with its recent "ATLAS Underlying Event Tune 2B" (AUET2B) tune.
  In the both methods outlined above we have used the following PDFs to estimate the uncerntainty:
Deleted:
<
<
 
  • CTEQ6L1 (10042)
  • MSTW2008LO (21000)
  • MRST LO* (20650)

Revision 62012-01-13 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 37 to 37
 In the Direct method one has to generate new signal event samples including into a generator not only other PDF(s) (different from the default one) but also tunes corresponding to these new PDF(s) to account for Underlying Event(UE), which in generator in general depends on the PDF used to run the generator and after to go through the whole chain of the sample production, i.e. simulation, digitization, reconstruction and production of D3PDs for the final analysis. The advantige of this method over re-weighting is that in this case one counts for the possible effects coming from UE, in contrast to the previous method. On the other hand, the main disadvantige of this method is, it's time and cpu consuming.
Added:
>
>
 

Realizations of the analysis methods

Changed:
<
<
For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO** ) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.
>
>

For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO** ) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.

  This study is done in release 17 using MC11b-like production setup.
Line: 51 to 55
 
  • MRST LO* (20650)
  • CT09MC2 (10772)
Changed:
<
<
Reason for choosing the above PDFs: MRST LO** is a LO PDF, so the above PDFs, chosen for the PDF systematics study, should also be of LO
>
>
For more details on the PDFs go to LHAPDF.

Reason for choosing the above PDFs: MRST LO** is a LO PDF, so the above PDFs, chosen for the PDF systematics study, should also be of LO.

Pythia6 parameters tuned in the the AUET2B tuning campain are as follows:

Paremeters PARP(62), PARP(64) and PARP(72) are responsible for shower parameterization, namely,

  • PARP(62) defines an initial state radiation (ISR) $p_T$ cut-off;
  • PARP(64) - ISR scale factor on $\alpha_S$ evaluation scale and;
  • PARP(72) is $\Lambda_{QCD}$ for FSR showering from ISR parton emissions.

Paremeters PARP(77), PARP(78), PARP(82), PARP(84) and PARP(90) difene MPI model parameters with

  • PARP(77) being responsible for a suppression of colour reconnection for high-$p_T$ strings;
  • PARP(78) - for the strength of colour reconnection;
  • PARP(82) - MPI $p_T$ cutoff at the nominal reference energy of 1800 GeV;
  • PARP(84) - fractional radius of core part of double-Gaussian transverse proton matter distribution and;
  • PARP(90) - exponent governing the rate of increase of the p0_T MPI cutoff as a function of $\sqrt{s}$.

For more info the AUET2B tune have a look at the ATLAS note ATL-PHYS-PUB-2011-009.

 
Deleted:
<
<
For more details on the PDFs see LHAPDF.
 

Sample Production

Changed:
<
<
MC11b
>
>
Within the official production campain the 4th generation quark samples (b' and t') are produced using the tags combination - e972_s1310_s1300_r3043_r2993_p834. Thus, to perform this study samples have been produced privately and following official production setup as closely as possible.

Athena releases used for different production steps are the following:

  • Event generation AtlasProduction, 16.6.8.2 (tag - e972);
  • G4 simulation AtlasProduction, 16.6.7.13 (tag - s1310);
  • Digitization and Reconst AtlasProduction, 17.0.5.1 (tag - r3043);
  • TopD3PD production - AtlasPhysics, 17.0.5.6.1 (tag - p834);

For more information on the MC11b production setup have a look at the following links:

 
Deleted:
<
<
Event generation AtlasProduction 16.6.6.3 - 16.6.7.X(16.6.8.2), using Generators/MC11JobOptions Generate_trf.py

G4 simulation AtlasProduction 15.6.6.3 - 16.6.7.X(16.6.7.13), AtlasG4_trf.py uses two beam spot settings: wide beam spot (90mm in z); narrow(er) beam spot (75 mm in z);

Digitization and Reconst. AtlasProduction 17.0.5.1(17.0.5.1) and newer DigiMReco_trf.py (new) transform which enables one to mix the v2 and v3 triggers according to the data periods ( run numbers ) in the run dependent conditions

 

Inclusion of the PDFs into a JO file

Changed:
<
<
The roles of the PARP(n) parameters are as follows for the various n: 77 - suppression of colour reconnection for high-p_T strings, 78 - strength of colour reconnection, 82 - MPI p_T cutoff at the nominal reference energy of 1800 GeV, 84 - fractional radius of core part of double-Gaussian transverse proton matter distribution, 90 - exponent governing the rate of increase of the p0_T MPI cutoff as a function of $sqrt{s}$. The fraction of the proton matter distribution contained in the core Gaussian is given by PARP(83) and was, as for the A*T2 tunes, fixed to the AMBT1 value of 0.356.
>
>
 

Reweighting method

Revision 52012-01-12 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 16 to 16
  Our analysis to estimate PDF uncerntainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined as well as described how the analysis is done.
Added:
>
>

Analysis methods

 
Changed:
<
<

Reweighting method

>
>

Reweighting method

  Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio
Line: 31 to 32
 
Changed:
<
<

Direct method

In Direct method one has to generate signal events using in the generator PDF different from the default one and going through the whole chain of sample production, generation, simulation, digitization, reconstruction and production of D3PDs for the final analysis.

>
>

Direct method

 
Added:
>
>
In the Direct method one has to generate new signal event samples including into a generator not only other PDF(s) (different from the default one) but also tunes corresponding to these new PDF(s) to account for Underlying Event(UE), which in generator in general depends on the PDF used to run the generator and after to go through the whole chain of the sample production, i.e. simulation, digitization, reconstruction and production of D3PDs for the final analysis. The advantige of this method over re-weighting is that in this case one counts for the possible effects coming from UE, in contrast to the previous method. On the other hand, the main disadvantige of this method is, it's time and cpu consuming.
 

Realizations of the analysis methods

Changed:
<
<
For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO**) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.
>
>
For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO** ) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.
  This study is done in release 17 using MC11b-like production setup.

Revision 42012-01-09 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDF Systematics Study at HU Berlin

Line: 38 to 38
 

Realizations of the analysis methods

Changed:
<
<
For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO**) ATL-PHYS-PUB-2011-009, with the * MRST LO** as a default PDF.
>
>
For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO**) ATL-PHYS-PUB-2011-009, with the * MRST LO** (20651) as a default PDF.
  This study is done in release 17 using MC11b-like production setup.

In the both methods outlined above we have used the following PDFs to estimate the uncerntainty:

Changed:
<
<
  • CTEQ6L1
  • MSTW2008LO from LHAPDF.
  • MRST LO*
  • CT09MC2
>
>
  • CTEQ6L1 (10042)
  • MSTW2008LO (21000)
  • MRST LO* (20650)
  • CT09MC2 (10772)
 
Added:
>
>
Reason for choosing the above PDFs: MRST LO** is a LO PDF, so the above PDFs, chosen for the PDF systematics study, should also be of LO
 
Added:
>
>
For more details on the PDFs see LHAPDF.
 
Changed:
<
<

Reweighting method

>
>

Sample Production

 
Changed:
<
<
To implement this method we use default signal heavy b' ?? samples to re-weight them.
>
>
MC11b

Event generation AtlasProduction 16.6.6.3 - 16.6.7.X(16.6.8.2), using Generators/MC11JobOptions Generate_trf.py

G4 simulation AtlasProduction 15.6.6.3 - 16.6.7.X(16.6.7.13), AtlasG4_trf.py uses two beam spot settings: wide beam spot (90mm in z); narrow(er) beam spot (75 mm in z);

Digitization and Reconst. AtlasProduction 17.0.5.1(17.0.5.1) and newer DigiMReco_trf.py (new) transform which enables one to mix the v2 and v3 triggers according to the data periods ( run numbers ) in the run dependent conditions

 
Deleted:
<
<

Direct method

 

Inclusion of the PDFs into a JO file

Line: 64 to 80
 energy of 1800 GeV, 84 - fractional radius of core part of double-Gaussian transverse proton matter distribution, 90 - exponent governing the rate of increase of the p0_T MPI cutoff as a function of $sqrt{s}$. The fraction of the proton matter distribution contained in the core Gaussian is given by PARP(83) and was, as for the A*T2 tunes, fixed to the AMBT1 value of 0.356.
Added:
>
>

Reweighting method

To implement this method we use default signal heavy b' ?? samples to re-weight them.

Direct method

Validation of samples

Extracting efficiencies

Reweighting method

Direct method

Discussion of the results

 

Howtos

To read more on the subject, go to References.

Revision 32011-12-28 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"
Changed:
<
<

PDFS ystematics Study of HU Berlin

>
>

PDF Systematics Study at HU Berlin

 
<!--optional-->
Changed:
<
<
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming parton distribution functions (PDF) choice in the generator to produce signal samples in an analysis to search for 4th generation heavy quarks done at HU Berlin.
>
>
This page is under construction and contains no useful information yet
 
Added:
>
>
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming from a choice of parton distribution functions (PDF) in the generator to produce signal samples in an analysis to search for 4th generation SM-like heavy quarks.
 
Deleted:
<
<

Introduction

 
Changed:
<
<
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error.
>
>

Introduction

 
Changed:
<
<
Thus, in this study we have tried to estimate the effect of a PDF change in a generator producing signal samples on a signal event selection efficiency.
>
>
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error. Thus, in this study we have tried to estimate the effect of a PDF change in a generator to produce signal samples on a signal event selection efficiency.
 
Changed:
<
<
To read more on the subject, go to References.

Example:You may also directly contact P.Uwer or S.Moch to get the package.

>
>
Our analysis to estimate PDF uncerntainties is done using two different methods, re-weighting method and a direct method. In the following shortly the idea of both methods is outlined as well as described how the analysis is done.
 

Reweighting method

Changed:
<
<
Suppose, we have MC events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, x_flav1, x_flav2, and an energy scale Q. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio
>
>
Suppose, we have MC signal events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, $x_{flav1}$, $x_{flav2}$, and an energy scale $Q$. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio
 
\[ EW=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)} \]
Changed:
<
<
After the EventWeight is applied on MC events generated with PDF1, they will effectively be distributed according to PDF2.
>
>
After the EventWeight, $EW$, is applied on MC events generated with PDF1 and then they will effectively be distributed according to PDF2.

Direct method

In Direct method one has to generate signal events using in the generator PDF different from the default one and going through the whole chain of sample production, generation, simulation, digitization, reconstruction and production of D3PDs for the final analysis.

Realizations of the analysis methods

For MC11, the default tune for Pythia samples is the "ATLAS Underlying Event Tune 2B" (AUET2B-LO**) ATL-PHYS-PUB-2011-009, with the * MRST LO** as a default PDF.

This study is done in release 17 using MC11b-like production setup.

 
Added:
>
>
In the both methods outlined above we have used the following PDFs to estimate the uncerntainty:

  • CTEQ6L1
  • MSTW2008LO from LHAPDF.
  • MRST LO*
  • CT09MC2

Reweighting method

To implement this method we use default signal heavy b' ?? samples to re-weight them.

Direct method

Inclusion of the PDFs into a JO file

The roles of the PARP(n) parameters are as follows for the various n: 77 - suppression of colour reconnection for high-p_T strings, 78 - strength of colour reconnection, 82 - MPI p_T cutoff at the nominal reference energy of 1800 GeV, 84 - fractional radius of core part of double-Gaussian transverse proton matter distribution, 90 - exponent governing the rate of increase of the p0_T MPI cutoff as a function of $sqrt{s}$. The fraction of the proton matter distribution contained in the core Gaussian is given by PARP(83) and was, as for the A*T2 tunes, fixed to the AMBT1 value of 0.356.

Howtos

To read more on the subject, go to References.

Example:You may also directly contact P.Uwer or S.Moch to get the package.

 
Line: 38 to 76
 
  • $\sigma_{NLO}$ (pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-100(scales) +30-29(PDFs)
  • CS_nlo(pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-101(scales)+30-29(PDFs)
Deleted:
<
<

Direct method

Revision 22011-12-27 - MalikAliev

Line: 1 to 1
 
META TOPICPARENT name="MalikAliev"

PDFS ystematics Study of HU Berlin

<!--optional-->
Deleted:
<
<
A few words
 
Changed:
<
<
Example:You may also directly contact P.Uwer or S.Moch to get the package.
>
>
This Twiki-page is to give some more or less detailed infotmation about the analysis to estimate systematics uncerntainties coming parton distribution functions (PDF) choice in the generator to produce signal samples in an analysis to search for 4th generation heavy quarks done at HU Berlin.
 

Introduction

Changed:
<
<
Functionality of HATHOR is based on the use of the expression:
>
>
Partonic distribution functions (PDFs) along with parton-parton interaction cross sections determine cross sections of processes in proton-proton collisions. Since the PDFs are not calculable from the first principles but are determined experimentally with some errors (which come from experimental measurements, theoretical models used to extract PDFs etc.), inclusion of any PDF into the cross section calculation introduces an additional systematic error.
 
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\[ \sigma^{qq}(\sqrt{s},m_q)=\sum_{i,j=q,q,g} \int_{-\infty}^\infty dx_1dx_2f^A_i(x_1,\mu_f^2) f^B_j(x_2,\mu_f^2)\sigma^{ij\rightarrow qq}(\rho,m^2_q,x_1,x_2,\alpha_s,\mu_r,\mu_f). \]
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Thus, in this study we have tried to estimate the effect of a PDF change in a generator producing signal samples on a signal event selection efficiency.
 
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where $\sigma^{ij\rightarrow qq}$ is a quark-antiquark pair production cross sections induced by i-th and j-th partons interaction, $f_i^A(x)$ and $f_j^B(x)$ are $i$-th and $j$-th partons distribution functions (PDF) in the A-th and B-th incoming nucleons correspondingly, $\mu_f$ and$\mu_r$ are factorization and renormalization scales, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.
 
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To read more on the subject, go to References.
 
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In order to calculate the central value factorization $\mu_f$ and renormalization $\mu_r$ scale parameters are set to a heavy quark mass, i.e. $\mu_f=\mu_r=m_q$. Along with central value the tool calculates also errors. There are two kind of errors: 1) errors coming from factorization $\mu_f$ and renormalization $\mu_r$ scales and 2) PDFs errors.
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Example:You may also directly contact P.Uwer or S.Moch to get the package.
 
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1) Scale errors are calculated by setting $\mu_f=\mu_r=m_q/2$ and $\mu_f=\mu_r=2m_q$ in order to get upper and lower deviations from the central value respectively.
 
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2) PDF errors can be calculated in two ways: a) in a simplified way, where upper and lower deviations from the central value are calculated as averaged, according to the formula $\Delta = \frac{1}{2}\sqrt{\sum_{i=1}^N[max(\sigma_i^+-\sigma_i^-)]^2}$ and thus errors are symmetric; b) in a more general way, where deviations from the central value are calculated according to the formula $\Delta \sigma_{max}^+=\sqrt{\sum^N_{i=1}[max(\sigma_i^+-\sigma_0,\sigma_i^--\sigma_0,0)]^2}$, for the upper deviation, and formula $\Delta \sigma_{max}^-=\sqrt{\sum^N_{i=1}[max(\sigma_0-\sigma_i^+,\sigma_0-\sigma_i^-,0)]^2}$, for the lower deviation, so that the errors are asymmetric.
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Reweighting method

 
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Suppose, we have MC events generated using PDF1. Interacting partons in incoming protons (antiprotons) are characterized by flavours, flav1, flav2, momentum fractions, x_flav1, x_flav2, and an energy scale Q. The PDF reweighting technique consists of evaluating, on the event-by-event basis, the probability of picking up the same flavoured partons with the same momentum fractions, x_flav1, x_flav2, according to a second PDF set, PDF2, at the same energy scale Q, then evaluating the following ratio

\[ EW=\frac{f_{PDF2}(f_1,x_1,Q^2)}{f_{PDF1}(f_1,x_1,Q^2)} \times \frac{f_{PDF2}(f_2,x_2,Q^2)}{f_{PDF1}(f_2,x_2,Q^2)} \]

After the EventWeight is applied on MC events generated with PDF1, they will effectively be distributed according to PDF2.

 
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To read more on the subject, go to References.
 
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Validation

 
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Validation of the tool is done comparing heavy quarks pair production cross sections calculated using this tool with ones obtained from other open official sources, first of all from different articles.
  Below Top quark pair production cross sections in proton-proton (pp) and proton-antiproton (ppb) collisions calculated by this tool (in red) are compared with ones obtained from arXiv/hep-ph/0804.2800 (in blue). PDF errors are calculated in the asymmetric way. Cross sections are given in picobarns (pb).

  • $\sigma_{NLO}$ (pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-100(scales) +30-29(PDFs)
  • CS_nlo(pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-101(scales)+30-29(PDFs)
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Direct method

Revision 12011-12-27 - MalikAliev

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META TOPICPARENT name="MalikAliev"

PDFS ystematics Study of HU Berlin

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A few words

Example:You may also directly contact P.Uwer or S.Moch to get the package.

Introduction

Functionality of HATHOR is based on the use of the expression:

\[ \sigma^{qq}(\sqrt{s},m_q)=\sum_{i,j=q,q,g} \int_{-\infty}^\infty dx_1dx_2f^A_i(x_1,\mu_f^2) f^B_j(x_2,\mu_f^2)\sigma^{ij\rightarrow qq}(\rho,m^2_q,x_1,x_2,\alpha_s,\mu_r,\mu_f). \]

where $\sigma^{ij\rightarrow qq}$ is a quark-antiquark pair production cross sections induced by i-th and j-th partons interaction, $f_i^A(x)$ and $f_j^B(x)$ are $i$-th and $j$-th partons distribution functions (PDF) in the A-th and B-th incoming nucleons correspondingly, $\mu_f$ and$\mu_r$ are factorization and renormalization scales, and $x_1$ and $x_2$ momentum fraction of each interacting parton in incoming nucleons.

In order to calculate the central value factorization $\mu_f$ and renormalization $\mu_r$ scale parameters are set to a heavy quark mass, i.e. $\mu_f=\mu_r=m_q$. Along with central value the tool calculates also errors. There are two kind of errors: 1) errors coming from factorization $\mu_f$ and renormalization $\mu_r$ scales and 2) PDFs errors.

1) Scale errors are calculated by setting $\mu_f=\mu_r=m_q/2$ and $\mu_f=\mu_r=2m_q$ in order to get upper and lower deviations from the central value respectively.

2) PDF errors can be calculated in two ways: a) in a simplified way, where upper and lower deviations from the central value are calculated as averaged, according to the formula $\Delta = \frac{1}{2}\sqrt{\sum_{i=1}^N[max(\sigma_i^+-\sigma_i^-)]^2}$ and thus errors are symmetric; b) in a more general way, where deviations from the central value are calculated according to the formula $\Delta \sigma_{max}^+=\sqrt{\sum^N_{i=1}[max(\sigma_i^+-\sigma_0,\sigma_i^--\sigma_0,0)]^2}$, for the upper deviation, and formula $\Delta \sigma_{max}^-=\sqrt{\sum^N_{i=1}[max(\sigma_0-\sigma_i^+,\sigma_0-\sigma_i^-,0)]^2}$, for the lower deviation, so that the errors are asymmetric.

To read more on the subject, go to References.

Validation

Validation of the tool is done comparing heavy quarks pair production cross sections calculated using this tool with ones obtained from other open official sources, first of all from different articles.

Below Top quark pair production cross sections in proton-proton (pp) and proton-antiproton (ppb) collisions calculated by this tool (in red) are compared with ones obtained from arXiv/hep-ph/0804.2800 (in blue). PDF errors are calculated in the asymmetric way. Cross sections are given in picobarns (pb).

  • $\sigma_{NLO}$ (pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-100(scales) +30-29(PDFs)
  • CS_nlo(pp, Mt=171 GeV, CME=14 TeV, CTEQ6.5) = 875+102-101(scales)+30-29(PDFs)
 
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