overview of the atlas hgtd upgrade · 12/01/18 norcalhep-ex y.zhao 3 / 14 atlas will undergo an...

Overview of the ATLAS HGTD Upgrade

NorCal HEP-Exchange 2018

Yuzhan Zhao, on behalf of SCIPP group SCIPP, University of California, Santa Cruz

12/01/18 NorCalHEP-EX Y.Zhao 2 / 14

High Luminosity Large Hadron Collider (HL-LHC) and ATLAS Detector● Large Hadron Collider (LHC): 14 TeV proton-

pronton collider at CERN, Geneva.

● ATLAS: General purpose detector for discovery of new physics and precise measurements.

– Layered detector: Tracker, EM & Hadronic Calorimeter, Muon spectrometer.

● Luminosity Upgrade (HL-LHC project):

– Scheduled to start in 2026.

– Deliver integrated luminosity 4000 fb-1 .

– Instantaneous luminosity 7.5 x 1034 cm-2 s-1. (5 times higher than current run.)

=> Main Challenge: Pile-up.

Run 2 (Current Run)

HL-LHC Run

Figures fromTP CERN-LHCC-2018-023

ATLAS Detector


● ATLAS will undergo an upgrade (Phase-II upgrade) to mitigate the pile-up.

● Adding new layer of silicon detector in the end-cap, the High-Granularity-Timing-Detector (HGTD)

● The goals are:

– Reducing the pile-up contamination in tracks and vertexes.

– Providing timing resolution of 30 ps/track.– With nominal Gaussian beam profile with 45mm or 175 ps spread

in z-direction, 175/30 ≈ 6, reducing the pile-up by factor of 6.– Improvement on

– track-to-vertex association.– b-jet tagging.– Lepton isolation.

– jet/Etmiss

.

ATLAS Phase-II Upgrade and High-Granularity-Timing-Detector (HGTD)


● Visualization of the timing information provided by the HGTD to help mitigate pile-up. (Figure below)

– 2D plot of vertex location with temporal information. (The width of the circle is the resolution in Z)

Blue ellipses: pile-up events.Red ellipse: hard scatter, event of interest.

ATLAS Phase-II Upgrade and High-Granularity-Timing-Detector (HGTD)

Figures fromTP CERN-LHCC-2018-023


HGTD Location, Covered Region, and Design

● Locates between the tracker and end-cap calorimeter.● Pseudo-rapidity(|η|): 2.4 to 4.0

– Central region (80%) 3 hits/track– Outside (20%) 2 hits/track

● Active area: (radial extension)– 120 mm < R < 640 mm.

● Pixel-lated 15x30 array sensor with pad area 1.3x1.3 mm2 (dead area <10%).● CO

2 cooling system to maintain sensors at -30 0C.

Table fromTP CERN-LHCC-2018-023


Predicted Radiation Level for HGTD

● Total fluence at the end of the HL-LHC run (4000 fb-1) (with safety factor of ~2 applied):

– R = 10 cm (Central region): 7.35x1015 N

eq/cm2 .

– R = 32 cm : 3.7x1015 Neq

/cm2 .

● The inner wheel of HGTD (R < 32 cm) will be replaced at the mid-run of HL-LHC.

– ≈ 32% of sensors/ASICs will be changed.

Inner wheel


HGTD Performance from Simulation

● Simulation with HGTD has shown promising improvements on physics objects.

– The black-line is with Inner Tracker (ITK) only.

– The colored-line is with HGTD+ITK with different scenarios.

Efficiency of rejecting pile-up jet increase by factor of 3

Improvement of b-jet tagging rejection.

5 – 20% improvement in lepton isolation efficiency.


Physics potential

● Better pile-up jet rejection

– Processes with VBF final states with di-jets in the forward region.

VBF H → WW → lvlv, signal strength (Δμ) 8% improvement.

● Improved b-jet tagging

– Searches and measurements with forward b-jets

t(H → bb), cross-section (σ) 11% improvement.

● Improved lepton isolation

– SM measurements that required leptons (e.g.: weak mixing angle)

13% improvement in sensitivity to sin2θeff

for the forward region.

● Timing for hits and vertices

– Detection of long lived particles at high pseudo-rapidity.

Magnetic Monopoles

● Improved luminosity measurement

– Overall improvement in physics potential.


● HGTD will be equipped with Low-Gain-Avalanche-Detector (LGAD), a thin silicon sensor designed by the CNM:

– LGADs make use of the n++-p+-p structure (n++ is N+, p+ is P, and p is π in the figure )

– Provide moderate gain of 20.

– Timing resolution as good as 20 ps/MiP before irradiation.

– (Details will be covered in the next presentation by C.Gee.)

● The Development of readout ASICs is on-going (ALTIROC, right figure)

– LGADs are Bump bonded to ALTIROC.

– Signal amplification and time measurement.

– Wire bonded to a flex cable going to peripheral electronics.

– Then sent to USA15 with optical link for high level processing.

Low-Gain-Avalanche-Detector (LGAD) and ALTIROC Readout ASICs


● R&D phase ends ~2020.

– Production in ~2022. Installation in 2025.

● LGAD Testing

– New full production from CNM, HPK and FBK.

● Readout eletronics

– ALTIROC(ver 2)

● Technical proposal is ready

– http://cdsweb.cern.ch/record/2623663

● TDR will be ready for Spring/Summer 2019.

Conclusion

http://cdsweb.cern.ch/record/2623663


HL-LHC Timeline


This work was supported by the United States Department of Energy,

grant DE-FG02-04ER41286

This project was supported in part by a Launchpad Grant awarded by the Industry Alliances

& Technology Commercialization office from the University of California, Santa Cruz.

This work was partially performed within the CERN RD50 collaboration.

Part of this work has been financed by the European Union’s Horizon 2020 Research and

Innovation funding program, under Grant Agreement no. 654168 (AIDA-2020) and Grant

Agreement no. 669529 (ERC UFSD669529), and by the Italian Ministero degli Affari Esteri

and INFN Gruppo V.

Acknowledgment


HGTD Groups: 9 countries, 20 institues


Current ATLAS Layout

HGTDReplacing current MBTS

End-Cap Calorimeter

overview of the atlas hgtd upgrade · 12/01/18 norcalhep-ex y.zhao 3 / 14 atlas will undergo an...

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