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J/ Simulations for RUN III

Manuel Calderon for the Heavy-Flavor Group

Analysis Meeting at BNLOctober 23, 2002

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Simulations so far …

Rejection/Efficiency: Working on AuAu low multiplicity simulations only up to now. Need dAu simulations, can probably get higher rejection with lower multiplicity events. Use Seff = S/(2B/S + 1)

Background:

Minbias Au+Au (only last weekend did d+Au begin running…)

Select most peripheral 50% x-section: dN/d = 11 (5.6 at 40%) to approx. d+Au multiplicity

Signal:

J/Psi simulated flat in pt and h to see efficiency vs pt

Will use more realistic pt distribution to see where most signal sits.

Throw one J/Psi in an empty event

Need to also mix them into a background event.

Using 3 cuts: Tower Energy (L0), Mass, CosL2)

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Algorithm

1) Approximate the electron daughters with towers (or clusters)Energy, Position2) Obtain vertex from BBC timing3) Need at least 2 towers to make a pair (could require this at L0?)4) Take all selected towers and make all possible pairs

Minv 2E1E2(1-cos())

5) Do cuts in M and cos()…

Still exploring possibilitiesTowers, clusters, cluster size?

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Algorithm : Need to explore various ideas

What are the best energy thresholds to use?

1, 1.5, 2 GeV? Want acceptable resolution and not to kill the signal.

First tested with Tower Energy only: resolution not good!

Now testing various cluster approaches: 2 towers, or patches of various sizes (3x3, 5x5, 7x7, 9x9)

Single Tower 2-Tower Cluster

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Acceptance and Trigger Efficiency J/

1) Done at mid-rapidity with full EMC

2) Trigger efficiency using Tower Energy (no clustering), and both towers with same threshold (1 GeV)

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Half EMC acceptance (pT - )

Raw Accepted electrons withE>1 GeV, 0.1 < < 0.9

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Acceptance and Trigger Efficiency (Half Emc, Cluster)

Half Emc, 0.2 < < 1

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J/ Mass at Level 2

Thrown massL2 Mass, real E, real cos()L2 Mass, cluster E, real cos()L2 Mass, real E, cluster cos()L2 Mass, cluser E and cos()

J/ flat in pt- Background

To do: simulate with some pT slope

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J/ Mass at Level 2 (from today!)

Thrown massL2 Mass, real E, real cos()L2 Mass, cluster E, real cos()L2 Mass, real E, cluster cos()L2 Mass, cluser E and cos()

J/ with slope 600 MeV Background (w/ dAu)

Rejection Factor at L2 for loose cuts: 35Goal: ~48 KHz/1KHz not too far

<M> = 2.93, 2.68 GeVM = 300, 668 MeV

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Decay Topology: large opening angle for most J/

Accepted J/ (flat in pt- Background

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Isolation cuts…Compare tower (or “cluster”) energy to surrounding energyin patch

i high towertowers

itowers

E E

E

For 3x3 patchElectrons

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To Do:

Still many simulations and tests to do to arrive at a good L2 Algorithm:

+ Low multiplicity in d+Au will reduce the backgrounds

- Signal is faint ~ “one in a million”

- Half EMC drastically reduces acceptance

Need to try out various patches, 3x3, 5x5 Energy Thresholds Mass Thresholds Opening Angles Isolation cuts