New Small Wheel Background

Charles Young (SLAC)

New Small Wheel Background 2

NEW JD GEOMETRY

New Small Wheel Background 3

Geometry Description

• Based on engineering plans from Marco et al– Thinner Disk compared with Runs 1 / 2 – Outside of Hub is not tapered

• Cutouts in cladding to accommodate chamber supports

– “Mismatch” between Disk and Hub cladding• Inner radius of Disk cladding is circular • Outer radius of Hub and cladding is polygon

– Larger gap between Disk and endcap calorimeter with three rings

– “L-shaped” polyboron shielding on Hub as in Run 2• Stainless steel bushing not yet implemented • Some engineering details ignored, as in all such

background simulations

New Small Wheel Background 4

Side View of Disk and Hub

5-cm front plate

4-cm back plate

polygon on outside

cylinder on outside

tapered cylinder on inside

beam line

New Small Wheel Background 5

Side View Including Disk Cladding

4-cm polyboron cladding on Disk

1-cm lead cladding on Disk

New Small Wheel Background 6

Side View Including Hub Cladding

5-cm polyboron cladding.Note cutouts for NSW supports.3-cm thick lead cladding (not shown here) has similar cutouts.

New Small Wheel Background 7

End View of Disk and Hub Cladding

Hub polyboron cladding

Hub lead cladding

Hub and its cladding have polygonal outer circumference

Inner radii of lead and polyboron cladding on Disk

Note radial gap between polyboron pieces

Note radial gap between lead pieces

New Small Wheel Background 8

Side View of L-Shaped Cladding

“L-shaped” cladding

5-cm polyboron cladding on Hub.Disk and its cladding not shown

New Small Wheel Background 9

Side View of First Ring

Innermost ring between JD and endcap calorimeter, made of steel

Disks

beam line

New Small Wheel Background 10

Close-Up Side View of First Ring

Innermost ring between JD and endcap calorimeter

Note gap between ring and disks. Ring is mounted on JD and spring-loaded so it touches endcap calorimeter

Disks

New Small Wheel Background 11

Side View Including Part of 2nd Ring

Disks

Innermost ring between JD and endcap calorimeter

Second ring between JD and endcap calorimeter attached to Disk

New Small Wheel Background 12

Side View of 1st and 2nd Rings

Second ring made up of three materials: steel, polyboron and lead

New Small Wheel Background 13

Side View of All Three RingsNote gap between 3rd ring and JD is larger than gap for 1st ring

3rd ring: polyboron + lead

New Small Wheel Background 14

SIMULATION RESULTS

New Small Wheel Background 15

Simulation Conditions

• Three detector geometries– 2012 geometry– Run 2 geometry– NSW geometry, as outlined earlier

• Otherwise identical assumptions: – √s = 14 TeV– s(pp) = 70 mb– Normalized to luminosity = 1034 cm-2 sec-1 – TGC sensitivities

2012 & Run 2 results from ATL-COM-MUON-2014-027.2012 corresponds to “I1” in Note.

New Small Wheel Background 16

2012 Geometry

Red: Photon hitsBlue: Neutron hitGreen: Charged particle hits except e+/e-

Yellow: e+/e- hits

New Small Wheel Background 17

Run 2 Geometry

Red: Photon hitsBlue: Neutron hitGreen: Charged particle hits except e+/e-

Yellow: e+/e- hits

New Small Wheel Background 18

NSW Geometry

Red: Photon hitsBlue: Neutron hitGreen: Charged particle hits except e+/e-

Yellow: e+/e- hits

New Small Wheel Background 19

Summary of Changes & Explanation

• 2012 to Run 2– Reduction by ~2x– Thinner beam pipe– Additional shielding around JD and JT

• Run 2 to NSW – Increase by ~2x, i.e. rates similar to 2012– Reduced JD shielding

Changes here refer to those

due to geometry changes

only.