Plots for approval- jet shapes as a function of NPV

Lily Asquith (ANL)Boost 2012, Valencia

measurements of jet propertiesOutlineWhat are jet shapes, and why are we measuring them?

Experimental challenges.

The measurements. arxiv:1206.5369

Whats new?

What are jet shapes and why are we measuring them?Why measure jet shapes?We can use them to distinguish between three-body (top) jets and two-body (light quark/ gluon) jets: planar flow.

arXiv:0807.0234Why measure jet shapes?Two-body (W/Z/H) jets with different polarisation and two-body (light quark/gluon) jets: angularities.

arXiv:0807.0234

Why measure jet shapes?Heavy/light flavour and quark/gluon jets: width (or girth)

arXiv:1010.3698v2arXiv:1106.3076v2What are jet shapes?All of these observables are constructed using the angular separation and energy of the jet constituents. e.g. mass:A jet.A constituent.

Traditionally jet shapes are differential and integrated. arxiv:1101.0070, arxiv:1204.3170These shapes are different measures of energy flow: planar flow, angularity, width and mass.

Core-heavy jet: width0

WidthWidthBroad jet: width1

Planar flowTwo-body jet: Linear energy deposition: Planar flow0

Planar flowThree-body jet: Planar energy deposition: Planar flow1

EccentricityIsotropic energy deposition: eccentricity1

EccentricityElongated energy deposition: eccentricity1

Angularity -2Asymmetric energy deposition: -2maximum

Angularity -2Symmetric energy deposition: -20

Correlations between observables

High pT, central, Pythia6 dijets.

Mass and width are strongly correlated.

Planar flow and eccentricity are strongly anti-correlated.Correlations between observables

At high mass, the correlations change. These are for QCD.Mass > 100 GeVNo mass cutThe experimental challenges:aka Pileup

Why pileup is such a problem for jet shapes and substructure

1: These jets are big. These sorts of observables generally change under pileup like R2 or moreWhy pileup is such a problem for jet shapes and substructure2: We want to be able to distinguish A from BABWhy pileup is such a problem for jet shapes and substructure2: We want to be able to distinguish A from BAB in these conditions.Pileup in 2010

2010: NPV~2 (28% of events NPV=1) special datasetThe Number of reconstructed Primary Vertices - NPV can tell us how much additional radiation we are dealing with.22Pileup in 2011

~ 10 .23Pileup in 20122012*: ~ 25+.

24Controlling pileup

Complementary cone technique (CDF) looks in region transverse (in azimuth) to the jet.

Energy deposits in this region are attributed to pileup and underlying event (UE): soft radiation that is always present.

Single vertex events contain only the UE contribution characterise pileup by comparing events with single and multiple vertices.

Can then find the scaling of e.g. M with R obtain subtractions for R=1 jets.

expectedmeasuredScaling:

arxiv:1101.3002, 1106.5952v2

arxiv:1206.5369 Controlling pileupComplementary cone technique restores distributions to shape seen in single vertex events.

The measurementsDetailsEvents are selected based on run conditions, data quality and detector conditions.The anti-kT algorithm is used with locally calibrated topological clusters as input.The highest pT jet in each event is measured, must have pT>300 GeV.ObservableRMass rangePileup correctionMass M0.6,1.0AllWidth W0.6,1.0AllPlanar flow P1.0130-210NPV=1Eccentricity 0.6,1.0>100Angularity -20.6100-130Not neededDetailsObservableRMass rangePileup correctionMass M0.6,1.0AllWidth W0.6,1.0AllPlanar flow P1.0130-210NPV=1Eccentricity 0.6,1.0>100Angularity -20.6100-130Not neededPlanar flow is measured for jets with mass in a window around the top mass.Not many R=0.6 jets have such a high mass:Only measure P for R=1.0 jets.Only measure P in pileup-free (NPV=1) events.DetailsEccentricity is measured in the general region of interest for boosted particle searches: M>100 GeV.

ObservableRMass rangePileup correctionMass M0.6,1.0AllWidth W0.6,1.0AllPlanar flow P1.0130-210NPV=1Eccentricity 0.6,1.0>100Angularity -20.6100-130Not neededDetailsQCD small-angle approximation gives a prediction for the peak and maximum values of the -2 distribution:Valid for fixed high mass and pT (we choose 100