Development and validation of HERWIG 7 tunes from CMS underlying-event measurements
Аннотация
Abstract This paper presents new sets of parameters (“tunes”) for the underlying-event model of the $${\textsc {herwig}} \,7$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mstyle> <mml:mi>H</mml:mi> <mml:mi>E</mml:mi> <mml:mi>R</mml:mi> <mml:mi>W</mml:mi> <mml:mi>I</mml:mi> <mml:mi>G</mml:mi> </mml:mstyle> <mml:mspace/> <mml:mn>7</mml:mn> </mml:mrow> </mml:math> event generator. These parameters control the description of multiple-parton interactions (MPI) and colour reconnection in $${\textsc {herwig}} \,7$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mstyle> <mml:mi>H</mml:mi> <mml:mi>E</mml:mi> <mml:mi>R</mml:mi> <mml:mi>W</mml:mi> <mml:mi>I</mml:mi> <mml:mi>G</mml:mi> </mml:mstyle> <mml:mspace/> <mml:mn>7</mml:mn> </mml:mrow> </mml:math> , and are obtained from a fit to minimum-bias data collected by the CMS experiment at $$\sqrt{s}=0.9$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> </mml:math> , 7, and $$13 \,\text {Te}\text {V} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>13</mml:mn> <mml:mspace/> <mml:mrow> <mml:mtext>Te</mml:mtext> <mml:mspace/> </mml:mrow> </mml:mrow> </mml:math> . The tunes are based on the NNPDF 3.1 next-to-next-to-leading-order parton distribution function (PDF) set for the parton shower, and either a leading-order or next-to-next-to-leading-order PDF set for the simulation of MPI and the beam remnants. Predictions utilizing the tunes are produced for event shape observables in electron-positron collisions, and for minimum-bias, inclusive jet, top quark pair, and Z and W boson events in proton-proton collisions, and are compared with data. Each of the new tunes describes the data at a reasonable level, and the tunes using a leading-order PDF for the simulation of MPI provide the best description of the data.
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