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| CMS-PAS-GEN-17-002 | ||
| A new set of CMS tunes for novel colour reconnection models in PYTHIA8 based on underlying-event data | ||
| CMS Collaboration | ||
| September 2021 | ||
| Abstract: New sets of parameter tunes for two of the colour reconnection models implemented in the PYTHIA8 event generator, QCD-inspired and gluon move, are obtained based on the default CMS PYTHIA8 underlying-event tune, CP5. Measurements sensitive to underlying-event performed at $\sqrt{s}=$ 1.96, 7, and 13 TeV are used to constrain the parameters of the colour reconnection models and the multiple parton interactions simultaneously. The new colour reconnection tunes are compared to various measurements at a centre-of-mass energy of 1.96, 7, 8, and 13 TeV including measurements of underlying event, strange particle multiplicities, jet substructure observables, hadron ratios, jet shapes and colour flow in top quark pair events, and top quark mass. The new colour reconnection tunes can be used to estimate systematic uncertainties related to colour reconnection modelling. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to EPJC. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Display of the topology of a hadron-hadron collision in which a "hard'' parton-parton collision has occurred. The "toward'' region contains the "toward-side'' jet, while the "away'' region, on the average, contains the "away-side'' jet. |
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Figure 2:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 2-a:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 2-b:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 2-c:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 2-d:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 3:
The pseudorapidity of charged hadrons, ${dN_{\mathrm {ch}}/d\eta}$, measured in $|\eta | < $ 2 by the CMS experiment at $\sqrt {s} = $ 13 TeV [17]. The predictions of the tunes CP5, CP5-"QCD-inspired'', and CP5-"gluon-move'' are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 4:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 4-a:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 4-b:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 4-c:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 4-d:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [9]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 5:
The pseudorapidity of charged hadrons, ${dN_{\mathrm {ch}}/d\eta}$, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [17]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 6:
The mean charged-particle average transverse momentum as a function of charged-particle multiplicity in transMAX (left) and transMIN (right) regions, measured by the ATLAS experiment at $\sqrt {s} = $ 13 TeV [10]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 6-a:
The mean charged-particle average transverse momentum as a function of charged-particle multiplicity in transMAX (left) and transMIN (right) regions, measured by the ATLAS experiment at $\sqrt {s} = $ 13 TeV [10]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 6-b:
The mean charged-particle average transverse momentum as a function of charged-particle multiplicity in transMAX (left) and transMIN (right) regions, measured by the ATLAS experiment at $\sqrt {s} = $ 13 TeV [10]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 7:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [11]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 7-a:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [11]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 7-b:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [11]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 7-c:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [11]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 7-d:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ (right) densities in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [11]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 8:
The charged-particle (upper left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (upper right) in the transverse region, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, and on average transverse momentum in the transverse region as a function of the leading charged particle ${p_{\mathrm {T}}}$ (lower left) and of the charged particle multiplicity (lower right), measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [12]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 8-a:
The charged-particle (upper left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (upper right) in the transverse region, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, and on average transverse momentum in the transverse region as a function of the leading charged particle ${p_{\mathrm {T}}}$ (lower left) and of the charged particle multiplicity (lower right), measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [12]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 8-b:
The charged-particle (upper left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (upper right) in the transverse region, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, and on average transverse momentum in the transverse region as a function of the leading charged particle ${p_{\mathrm {T}}}$ (lower left) and of the charged particle multiplicity (lower right), measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [12]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 8-c:
The charged-particle (upper left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (upper right) in the transverse region, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, and on average transverse momentum in the transverse region as a function of the leading charged particle ${p_{\mathrm {T}}}$ (lower left) and of the charged particle multiplicity (lower right), measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [12]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 8-d:
The charged-particle (upper left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (upper right) in the transverse region, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, and on average transverse momentum in the transverse region as a function of the leading charged particle ${p_{\mathrm {T}}}$ (lower left) and of the charged particle multiplicity (lower right), measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [12]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 9:
The pseudorapidity of charged particles, ${dN_{\mathrm {ch}}/d\eta}$, with at least one charged particle in $|\eta | < 2.4$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [27]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 10:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CDF experiment at $\sqrt {s} = $ 1.96 TeV [13]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 10-a:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CDF experiment at $\sqrt {s} = $ 1.96 TeV [13]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 10-b:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CDF experiment at $\sqrt {s} = $ 1.96 TeV [13]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 10-c:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CDF experiment at $\sqrt {s} = $ 1.96 TeV [13]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 10-d:
The charged particle (left) and ${p_{\mathrm {T}}^{\mathrm {sum}}}$ densities (right) in the transMIN (upper) and transMAX (lower) regions, as a function of the ${p_{\mathrm {T}}}$ of the leading charged particle, ${p_{\mathrm {T}}^{\mathrm {max}}}$, measured by the CDF experiment at $\sqrt {s} = $ 1.96 TeV [13]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 11:
The forward energy flow as a function of pseudorapidity in two different selections, in minimum-bias events (left) and in events with a presence of a hard dijet system (right), measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [28]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 11-a:
The forward energy flow as a function of pseudorapidity in two different selections, in minimum-bias events (left) and in events with a presence of a hard dijet system (right), measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [28]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 11-b:
The forward energy flow as a function of pseudorapidity in two different selections, in minimum-bias events (left) and in events with a presence of a hard dijet system (right), measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [28]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 12:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 12-a:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 12-b:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 13:
Ratios of particle yields, $p/\pi $, as a function of transverse momentum in miminum bias events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [32]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 14:
Ratios of particle yields for light, charm, and bottom hadrons predicted by the the CP5 and CP5-CR tunes compared to data from $e^{+}e^{-}$ colliders [33] and the DELPHI collaboration [34]. |
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Figure 15:
Average charged-hadron multiplicity as a function of the jet ${p_{\mathrm {T}}}$ for jets with rapidity $|y| < 1$, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [24]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 16:
Distributions of $F(z)$ for $25\text { GeV} < p_T^{\text {jet}} < 40\text { GeV}$ (left) and $400\text { GeV} < p_T^{\text {jet}} < 500\text { GeV}$ (right) for jets with pseudorapidity $|\eta _\text {jet}| < 1.2$, measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [25]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 16-a:
Distributions of $F(z)$ for $25\text { GeV} < p_T^{\text {jet}} < 40\text { GeV}$ (left) and $400\text { GeV} < p_T^{\text {jet}} < 500\text { GeV}$ (right) for jets with pseudorapidity $|\eta _\text {jet}| < 1.2$, measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [25]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 16-b:
Distributions of $F(z)$ for $25\text { GeV} < p_T^{\text {jet}} < 40\text { GeV}$ (left) and $400\text { GeV} < p_T^{\text {jet}} < 500\text { GeV}$ (right) for jets with pseudorapidity $|\eta _\text {jet}| < 1.2$, measured by the ATLAS experiment at $\sqrt {s} = $ 7 TeV [25]. The predictions of the CP5 and CP5-CR tunes are compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 17:
Number of charged particles and ${p_{\mathrm {T}}}$ flow in the transverse region of DY events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV in bins of Z boson ${p_{\mathrm {T}}}$ [35]. The plots show the predictions of the CP5 and CP5-CR tunes compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 17-a:
Number of charged particles and ${p_{\mathrm {T}}}$ flow in the transverse region of DY events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV in bins of Z boson ${p_{\mathrm {T}}}$ [35]. The plots show the predictions of the CP5 and CP5-CR tunes compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 17-b:
Number of charged particles and ${p_{\mathrm {T}}}$ flow in the transverse region of DY events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV in bins of Z boson ${p_{\mathrm {T}}}$ [35]. The plots show the predictions of the CP5 and CP5-CR tunes compared to data. The coloured band represents the total experimental uncertainty in the data. |
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Figure 18:
Distributions of the particle multiplicity (left) and the angle between two groomed subjets ($\Delta R_g$) (right) measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [40]. The coloured band represents the total experimental uncertainty in the data. |
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Figure 18-a:
Distributions of the particle multiplicity (left) and the angle between two groomed subjets ($\Delta R_g$) (right) measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [40]. The coloured band represents the total experimental uncertainty in the data. |
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Figure 18-b:
Distributions of the particle multiplicity (left) and the angle between two groomed subjets ($\Delta R_g$) (right) measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [40]. The coloured band represents the total experimental uncertainty in the data. |
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Figure 19:
Pull angle between jets from the W boson in top quark decays, calculated from the charged constituents of the jets, measured by the ATLAS experiment using $\sqrt {s} = $ 8 TeV data to investigate colour flow. The coloured band represents the total experimental uncertainty in the data. |
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Figure 20:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP1 and CP1-CR tunes (upper) and CP2 and CP2-CR tunes (lower) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 20-a:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP1 and CP1-CR tunes (upper) and CP2 and CP2-CR tunes (lower) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 20-b:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP1 and CP1-CR tunes (upper) and CP2 and CP2-CR tunes (lower) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 20-c:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP1 and CP1-CR tunes (upper) and CP2 and CP2-CR tunes (lower) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 20-d:
The strange particle production, $\Lambda $ baryons (left) and $K_s^0$ mesons (right), as a function of rapidity, measured by the CMS experiment at $\sqrt {s} = $ 7 TeV [29]. The predictions of the CP1 and CP1-CR tunes (upper) and CP2 and CP2-CR tunes (lower) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 21:
Ratios of particle yields, $p/\pi $, as a function of transverse momentum in minimum bias events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [32]. The predictions of the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 21-a:
Ratios of particle yields, $p/\pi $, as a function of transverse momentum in minimum bias events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [32]. The predictions of the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 21-b:
Ratios of particle yields, $p/\pi $, as a function of transverse momentum in minimum bias events, measured by the CMS experiment at $\sqrt {s} = $ 13 TeV [32]. The predictions of the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right) are compared to data. The coloured band represents the total experimental uncertainty in the data. |
png pdf |
Figure 22:
Ratios of particle yields for light, charm, and bottom hadrons predicted by the different pythia8 tunes compared to data. The data are compared to predictions from the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right). |
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Figure 22-a:
Ratios of particle yields for light, charm, and bottom hadrons predicted by the different pythia8 tunes compared to data. The data are compared to predictions from the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right). |
png pdf |
Figure 22-b:
Ratios of particle yields for light, charm, and bottom hadrons predicted by the different pythia8 tunes compared to data. The data are compared to predictions from the CP1 and CP1-CR tunes (left) and CP2 and CP2-CR tunes (right). |
| Tables | |
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Table 1:
List of input RIVET routines, distributions, x-axis ranges, R of the distributions in the fit, number of bins and the centre-of-mass energy used in the fits to derive the CP5-CR1 and CP5-CR2 tunes. |
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Table 2:
MPI and CR parameter ranges used in the tuning procedure. |
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Table 3:
The parameters obtained in the fits of the CP5-CR1 and CP5-CR2 tunes, compared with that of the tune CP5. The upper part of the table displays the fixed input parameters of the tune, while the lower part shows the fitted tune parameters. The number of degrees of freedom ($N_\text {dof}$) and the goodness of fit divided by $N_\text {dof}$ are also shown. |
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Table 4:
The top quark mass, ${m_{\mathrm{t}}}$, and $\mathrm{W} $ mass, ${m_{\mathrm{W}}}$, extracted by a fit to the predictions of the different pythia8 tunes. The uncertainties in the ${m_{\mathrm{t}}}$ and ${m_{\mathrm{W}}}$ values correspond to the uncertainty in the fitted ${m_{\mathrm{t}}}$ and ${m_{\mathrm{W}}}$. |
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Table 5:
List of input RIVET routines, distributions, x-axis ranges, R of the distributions in the fit, number of bins and the centre-of-mass energy used in the fits to derive the CP1-CR1 and CP1-CR2 tunes. |
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Table 6:
List of input RIVET routines, distributions, x-axis ranges, R of the distributions in the fit, number of bins and the centre-of-mass energy used in the fits to derive the CP2-CR1 and CP2-CR2 tunes. |
png pdf |
Table 7:
The parameters obtained in the fits of the CP1-CR1 and CP1-CR2 tunes, compared to the ones of the tune CP1. The upper part of the table displays the fixed input parameters of the tune, while the lower part shows the fitted tune parameters. The number of degrees of freedom ($N_\text {dof}$) and the goodness of fit divided by the number of degrees of freedom are also shown. |
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Table 8:
The parameters obtained in the fits of the CP2-CR1 and CP2-CR2 tunes, compared to the ones of the tune CP2. The upper part of the table displays the fixed input parameters of the tune, while the lower part shows the fitted tune parameters. The number of degrees of freedom ($N_\text {dof}$) and the goodness of fit divided by the number of degrees of freedom are also shown. |
| Summary |
| New sets of parameters for two of the colour reconnection (CR) models, QCD-inspired and gluon-move, implemented in the PYTHIAviii event generator are obtained, based on the default CMS CP5 PYTHIAviii tune. Measurements sensitive to underlying-event (UE) contributions performed at $\sqrt{s}=$ 1.96, 7, and 13 TeV are used to constrain the parameters for the CR and for the multiple parton interactions simultaneously. Different measurements at a centre-of-mass energy of 1.96, 7, 8, and 13 TeV are used to evaluate the performance of the new tunes. The central values predicted by the new CR tunes for the UE and minimum-bias distributions significantly better describe the data than the CR models with their default parameters before tuning. The predictions of the new tunes are able to achieve a very good level of agreement against many underlying-event observables including UE data measured at forward pseudorapidities. However, it should be noted that the models after tuning perform no better than the CP5 tune for the observables presented in this study. The new CR tunes are also tested against measurements of strange particle multiplicities for $\Lambda$ baryons and $K_s^0$ mesons. It is shown that new CR models alone do not improve the description of the strange particle production versus rapidity distribution for $\Lambda$ baryons. It is observed that all CP5 tunes, irrespective of the CR model, describe particle production for $K_S^0$ versus rapidity very well. The predictions of the new tunes to jet shapes and colour flow measurements done with top quark pair events are also compared to data. None of the tunes describe the jet shapes distributions considered in this note well, and all tunes have similar predictions. Some differences are also observed with respect to the colour flow data which is particularly sensitive to the ERD option in the CR models. The differences between the predictions using the different tunes observed here indicate that the inclusion of observables such as the jet pull angle and other jet substructure observables could be beneficial in tuning studies. A study of uncertainty on the top quark mass measurement due to CR effects is also presented which shows that CR will continue to be one of the dominating uncertainty sources in the top quark mass measurements. |
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Compact Muon Solenoid LHC, CERN |
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