October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 1

Inkyu’s X - FILE :Local Compactness

21st Century PHOBOS presents

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 2

Motivation : Flow systematics

Dilution

Enhancement

Jet

2

2

Can we do STAR-like jet study? Don’t have Pt trigger…

If yes, 1) useful for Flow systematics, 2) potential new physics menu

- Is Flow the unique source E-by-E modification of dN/dd ?

- STAR showed “Jet-ness” at RHIC…

- v2 = Flow (x%) + Jet (1-x %)

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 3

E-by-E Jet-finding from dNh/dd

• dN/d ~ flat from =-2 to =2.• full azimuthal acceptance, to .

• Need to correct Octagon acceptance (phase space, cracks).• Need to fix Hot/Dead channels, fix CMN problem. • Need to apply 2D Poisson correction, Occ().

Similar to v2

• Need a Jet algorithm– ATLAS/JetFinder Library : cone, double-cone, kT, pair-

wise merging, sliding windows, MGS, etc … – No need of “Pt/Et” seed, not sensitive to MB hits

Additional tool

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 4

ATLAS/MGS algorithm : Local Compactness

AHD (Average Hit Density)

= #hits / Total Area

LHD (Local Hit Density)

= #hits inside / window size

-2 2-

AHD = 24/(2 x 4) ~ 0.95,

LHD = 9/( r2 ) ~ 4.47

LC= 4.7!

LC = LHD/AHD

• Designed for Top quark mass, Heavy-Higgs search

• Dynamical Jet size variation, give the best Jet energy calibration

• Image Processing method, Rely on compactness, No license fee

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 5

A typical LC event : peripheralLC>2PR01 data (Flow)

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 6

A typical LC event : peripheral

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 7

A typical LC event : peripheral

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 8

A typical LC event : peripheral

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 9

A typical LC event : mid-central

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 10

A typical LC event : mid-central

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 11

A typical LC event : most central

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 12

# of LCs : peripheral events

MC shows more LCs (Flow, Fluctuation)

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 13

# of LCs : mid-central events

Starting from bin 4, Data show more LCs (Jet-ness ?)

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 14

# of LCs : central events

Data show 3 or 4 times more LCs, even di-jets (Jet-ness !)

4 times higher Prob

October 4, 2002 Inkyu Park - Phobos Collaboration Meeting - BNL 15

Summary

• Data show higher Prob. of Local Compactness! – much more than the contribution from Flow

• Are they Jets? CMN problems? Secondary shower? – important source of Non-flow correlation

• At best, can be a new physics menu– We have larger acceptance (-2 to 2). STAR: -0.7 to 0.7

• At worst, can be used for v2 systematics (non-flow)

• Still long way to go, to get a conclusion