Crist iano Fanel l i

John Hardin

Just in Stevens

Mike Wi l l iams

John Frye

Matthew Shepherd

1

A DIRC FOR GLUEX

Fixed target (ɣ,p) experiment

Poised to start taking data in 2016

Looking for “exotic mesons” – requiring nontrivial gluonic contributions

Predicted by lattice QCD in the mass range we probe

Interested in finding the strange content of these particles

2

GLUEX PHYSICS

We would like to increase our energy reach in PID

Especially need this for high purity samples (going from 90% -> 95%

purity lowers efficiency by ~50% with baseline GlueX)

Additional runtime has been approved by the PAC

3

MOTIVATION

eta2300 phi1850 Purity Base DiRC Base DiRC

0.90 0.37 0.51 0.68 0.74 0.95 0.18 0.38 0.61 0.69 0.99 0.01 0.06 0.28 0.42

h' 2600 y2175 Purity Base DiRC Base DiRC

0.90 0.31 0.49 0.52 0.67 0.95 0.15 0.33 0.39 0.59 0.99 0.00 0.06 0.06 0.23

Identification Efficiency

4

DIRC @ BABAR

The goal is to determine the

velocity of the charged particle

based on its angle

• BaBar’s readout of the DiRC Shown above

• A particle travels through the bars and

Cerenkov radiates. As these photons totally

internally reflect up the bar, their angle is

preserved and can be read out.

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SLAC’S FDIRC PROTOTYPE

(for Super-B)

$

6

GEANT SIMULATION OF PHOTONS

In front of the

FCAL

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LOCATION IN GLUEX

Resolution depends

heavily on the number of

photons found

Test dif ferent mirror techs

Polished, coated, Aluminum

Aluminum coated glass

taped to an Aluminum

strongback

8

MIRRORS

Use same method as LHCb

A reference spherical mirror, a point source, and a ccd

camera can give angular dispersion

Then put flat mirror “in the way” to measure

9

EVALUATING THE MIRRORS

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MIRROR EVALUATION SETUP

The image of the fiber is 1mm

We require <~.5mrad of spread, and

this is clearly much better than that

Relative pixel size drawn

11

SAMPLE IMAGE

Lapped Al 45 deg Polished Al 45 deg Glass 14 deg

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REFLECTIVITY

“Purple”

Using Kernel Density Estimation

Still need to optimize for speed

3 GeV requires much less time than 4+ GeV,

Implementing progressive version

X-Y distributions shown below

RECONSTRUCTION METHOD

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θ=0⁰ φ=0⁰

θ=4⁰ φ=40⁰

Can use this method to evaluate different designs

Most design parameters exist in a broad valley

Switched to water

Magnification effect

Lost Photons

Little net effect

Switched to a 3 segment mirror

Small gain from spread and timing

Tracking error cancels in our geometry

14

DESIGN FROM RECONSTRUCTION

Analytically tracking photons down the bar to form KDE

Needs to be faster per particle to integrate with offline reconstruction (3Hz->~100Hz)

Minimal optimization has been performed, so there is plenty of room for improvement

Very quick at analyzing different geometries for fixed kinematics

Under development along with other algorithms (e.g. Look up tables)

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RECONSTRUCTION NOTES

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EXPECTED PERFORMANCE: EFFICIENCY

AND MISSID

Recently reviewed by Jlab, report forthcoming,

but feedback already received has been very

positive

Expecting to start construction in the first half

of 2016

In the process of testing mirror technologies

and improving reconstruction

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OUTLOOK

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QUESTIONS?

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BONUS SLIDE: TRANSPORTATION

Ver y expensive bars to be moved across USA

Contract w i th Rock - I t Cargo and i terate

Our geometry results in tracking errors canceling for

“forward” and “backward” photons.

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BACKUP: TRACKING ERROR

Room is not completely dark, so long runs must take all

sources of background into account

Do this with and without mirror

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BACKUP: REFLECTIVITY

Blue LED

345nm LED