DiscoveringHeavyParticles

Introduction

This note demonstrates a recently proposed method for determining the mass of boosted particles from their decay products by exploiting the substructure of the resulting single collimated jet using the kT algorithm. We illustrate this method with a simple RPV SUSY model using the ATLAS detector at the LHC. We consider the hadronic decay of boosted neutralinos into single jets composed of three collimated subjets. We consider up to 1fb-1 of integrated luminosity with 10TeV simulated data. The ATL-PHYS-PUB-2009-076 note can be found here

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Pseudo cone-radius as a function of neutralino pT

• Figure1.eps: ATL-PHYS-PUB-2009-076 [ Figure 1 ]

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pT vs. mass for jets in events with at least four jets with |eta| < 2.5 for 1 fb−1

• Figure2.eps: ATL-PHYS-PUB-2009-076 [ Figure 2 ]

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Jet mass for jets with pT > 275GeV in events with at least four jets with |eta| < 2.5

• Figure3.eps: ATL-PHYS-PUB-2009-076 [ Figure 3 ]

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y2 vs. y1 for jets with pT >275GeV in events with at least four jets with |h|<2.5 (distributions normalised to unity)

• Figure4.eps: ATL-PHYS-PUB-2009-076 [ Figure 4 ]

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Jet mass for jets with pT > 275GeV and y2 > −0.17y1 +0.08 in events passing all event selection cuts

• Figure5.eps: ATL-PHYS-PUB-2009-076 [ Figure 5 ]

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Jet pT for jets with pT > 275GeV and y2 > −0.17y1+0.08 in signal events passing all event selection cuts

• Figure6.eps: ATL-PHYS-PUB-2009-076 [ Figure 6 ]

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Jet mass for jets with pT > 275 GeV and y2 > −0.17y1 +0.08 in events passing all event selection cuts

• Figure7.eps: ATL-PHYS-PUB-2009-076 [ Figure 7 ]

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	Cut 1	Cuts 1 & 2	Cuts 1,2 & 3	Cuts 1,2,3 & 4
SUSY	14577	5849	792	347
t ¯t	2.3×10^5	2,000	200	1
dijets	3.2×10^9	1.1×10^6	1.8×10^4	1100
W+jets	1500	20	20	0
Z+jets	1.9×10^4	210	2	1

Table 2: Offline Cut Flow (all counts are Events per 1 fb−1)

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Trigger Name	Total	Prescale Effic. before event selection (%)	Effic. after event selection (%)
J350	1	50.0	82.7
3J180	1	56.0	98.3
4J95	20	77.6	99.6
3J60	1000	95.0	99.6
J265	15	75.5	99.6
4J125	1	55.8	99.6
JE280	2	91.0	100
JE340	1	83.2	100

Table 3: Trigger efficiencies for various jet triggers on RPV SUSY events.

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