Introduction to the ATLAS Experiment at the LHC and its Upgrade for the High Luminosity LHC

Introduction to the ATLAS Experiment at the LHC and its Upgrade for the High Luminosity LHC Introduction The ATLAS Experiment Detector Technologies Phase-0 Phase-I Phase-II Digression: ATLAS and the Higgs Conclusions Phil Allport. ATLAS Upgrade Coordinator University of Liverpool Steve Lloyd ATLAS UK Collaboration Board Chair Queen Mary, University of London 24/10/14 UK ATLAS Institutions Birmingham Cambridge Edinburgh Glasgow Lancaster Liverpool Manchester Oxford Queen Mary, London Rutherford Appleton laboratory Royal Holloway, London Sheffield Sussex University College, London Warwick 1

The Large Hadron Collider at CERN

The Challenges At the LHC, around 2800 bunches of 10 11 protons circulate in each direction in a 27km tunnel at energies approaching 7 TeV (7 10 12 ev) and collide every 25ns inside the LHC experiments. Each beam carries an energy 360MJ (the same kinetic energy as a TGV at 150km/h). In each bunch collision, there are typically multiple proton collisions with hundreds of particles going in all directions. The job of the detectors is to measure the path of each particle for each bunch crossing and determine its corresponding energy and momentum. Detectors often need to cope with many particles per cm 2 (high particle fluxes), many different particle types (different masses etc) and constraints of cost, accessibility, high radiation levels over long operation periods, data transmission and data storage limitations Usually a system of detectors is needed so that the different components have to perform their function while minimally interfering with the function of the other parts The requirements always push in the direction of improved position, time, energy and momentum resolution with clearer particle identification (or background rejection) and realtime pattern recognition and data processing At the same time many application demand affordable large area coverage 3

Particle Detectors Tracking detectors focus on measuring the paths of all the charged particles to find their energies (E), momenta (p) and charge (±), derived from linking the hits for each particle combined with additional information from other detector layers (which often also can see the neutral particles) A very powerful technique to measure momentum is to track in a known magnetic field where the curvature is proportional to 1/p. Join the dots and fit for curves (seen end-on) in a solenoid magnetic field As the particle traverses the full detector system (including the tracker) the pattern of energy loss in different media provides information on the particle type (and therefore mass). Where massive detectors stop the particle entirely (electromagnetic and hadronic calorimeters) they directly provide E and also the energies and directions of the neutral particles. (In ATLAS ionization in liquid Ar with Pb, Cu or W absorbers is used for calorimetry except the for hadronic barrel based on steel and scintillator tiles) Muons, the main component of cosmic ray interactions at ground level, are very penetrating and for these charged particles, the identification comes from this property 4

ATLAS is a collaboration of 3000 physicists from 177 universities and laboratories in 38 countries including 1000 PhD students (see cern.ch/atlas)

ATLAS: Inner Tracking Detectors 25 m 10

ATLAS: Inner Tracking Detectors 25 m 11 11

The ATLAS Pixel Detector Three barrel layers: R= 5 cm (B-Layer), 9 cm (Layer-1), 12 cm (Layer-2) modules tilted by 20º in the Rφ plane to overcompensate the Lorentz angle. Two endcaps: three disks each 48 modules/disk Three precise measurement points up to η <2.5: RΦ resolution:10 µm η (R or z) resolution: 115 µm 1456 barrel modules and 288 forward modules, for a total of 80 million channels, 25ns beam crossing, total area of 17,000 cm 2. Temperature of -10 ºC given dose of 10 15 n/cm 2 (~1MGy) 2 T solenoidal magnetic field. 12

ATLAS Silicon Strip Detectors Designed to record each separate collision at 40 million collisions per second. Measure where particles go with 10μm precision (15 million strips). Has to withstand radiation of 10 14 n eq /cm 2 and 100kGy. 610,000 cm 2 of silicon micro-strip First 7 TeV Collision sensors ~20,000 6 6 cm silicon Event detectors 2012 (8TeV running) Higgs candidate to 4 muons showing importance of forward tracking ATLAS 13

This is where it goes

Physics Reach at the LHC The challenge of the LHC is to cope with proton-proton collisions at rates giving up to 10 16 collision events per year, but where only a tiny fraction can be sensibly recorded Even at LHC energies and collision rates, new physics is hard to find Most collisions give low momentum events that do not correspond to the proton s constituents undergoing the head-on collisions which have the energies to make new particles A multi-level trigger quickly identifies signatures of high-energy constituent collisions and gives 10-5 online data reduction Even then, many tens of millions of Gigabytes per year need storing and processing: Worldwide LHC Computing Grid (WLCG over 150,000 processors at over 170 sites in 36 countries http://lcg.web.cern.ch/lcg/public/) Cross-section, σ, measured in units of barns (b) 15

Discovery of the Higgs at the LHC Spin-½ Spin-1 16

Discovery of the Higgs at the LHC 17

Discovery of the Higgs at the LHC The Higgs mass is measured to be 125.36 ± 0.41 GeV, corresponding to about 130 times the mass of the proton

The Higgs: Next Steps at the LHC 19

The Higgs: Next Steps at the LHC The CERN Council (May 2013) stated: The discovery of the Higgs boson is the start of a major programme of work to measure this particle s properties with the highest possible precision for testing the validity of the Standard Model and to search for further new physics at the energy frontier. The LHC is in a unique position to pursue this programme. Europe s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around 2030 HEPAP in the US (May 2014) decided: The HL-LHC is strongly supported and is the first high-priority large-category project in our recommended program 20

Current Shutdown Phase-0 - New insertable pixel layer (IBL) + new pixel services + new small Be pipe - New Aluminum beam pipes to prevent activation problem and reduce muon BG - New C 3 F 8 evaporative cooling plant for Inner Detector + IBL CO 2 cooling plant - Replace all calorimeter low voltage power supplies - Finish the installation of the muon chambers staged in 2003 + additional chambers in the feet and elevators region + gas system consolidation - Upgrade the magnets cryogenics and decouple toroid and solenoid cryogenics - Add specific neutron shielding where necessary - Revisit the entire electricity supply network (UPS in particular) - Where possible prepare Phase 1 upgrade (services etc) - Re-align the barrel calorimeter and ID + consolidation of infrastructure and services + general maintenance - Some early installation of (Phase-I) trigger upgrades which are required for above design luminosity operation New trigger processors Improve muon trigger with current small wheel (reduce fake rate) Tile calorimeter outer layer trigger (to help muon triggering) New and replacement trigger cards Dual output boards to allow fast trigger on tracks 21

Current Shutdown Phase-0 - New insertable pixel layer (IBL) + new pixel services + new small Be pipe 22

ATLAS: Inner Tracking Detectors 25 m 23 23

ATLAS Inner Detector Straw tubes Silicon strip Silicon pixel 24 24

ATLAS Inner Detector Straw tubes Silicon strip Silicon pixel 25 25

Insertable B-Layer Planar Sensor Finely segmented diode structure n-implants to collect electrons 200μm thick Minimize inactive edge by shifting guard-ring under pixels (215 μm) Radiation hardness proven up to 2.4 10 16 p/cm 2 (Grad doses) FE-I4 Pixel Chip (26880 channels) 19 x 20 mm 2 130 nm CMOS process, based on an array of 80 by 336 pixels (each 50 x 250 μm 2 ) FE chip - 3D Sensor Both electrode types are processed inside the detector bulk Max. drift and depletion distance set by electrode spacing Reduced collection time and depletion voltage sensor IBL Insertion into ATLAS on 7 th May 26

Future Upgrade Planning 27

Future Upgrade Planning Phase-I Upgrade (LS2) Starts Middle 2018 28

Future Upgrade Planning In 2013, 4 Technical Design Reports for Phase-I construction projects were prepared within ATLAS, approved by the CB and submitted to the LHCC As of 5 th December 2013 all 4 were endorsed by CERN s LHC Committee (LHCC) and Upgrade Cost Group Memoranda of understanding with funding agencies now mostly signed 29

New Small Muon Wheels (CERN-LHCC-2013-006) The innermost station of the muon end-cap Located between end-cap calorimeter and end-cap toroid Trigger Chambers Micro-Megas Principle Gas (ionization) based precision chambers optimised for high rate operation at HL-LHC stgc Prototype Tracking Chambers 2.4m 1m Micro-Megas prototype for ATLAS New Small muon Wheel (1280m 2 ) Micromegas Prototype Mechanical Prototype 31

Future Upgrade Planning Phase-II Upgrade (LS3) Starts End 2022 32

Phase-II Detector Upgrades Integrated radiation levels (up to 2-3 10 16 n eq /cm 2 ) and plan to cope with up to 200 interactions every 25ns Implications of this include: - New Inner Detector (strips and pixels) - Trigger and data acquisition upgrades - Use tracks to improve triggering - New calorimeter front-end and back-end electronics (both LAr and tile) - Possible upgrades of very forward LAr - Muon system trigger electronics - Possible muon trigger chamber upgrades - Forward detector upgrades - Collimator and shielding upgrades - Various infrastructure upgrades - Common activities (installation, safety, ) - Software and Computing FCal Cold cover 33

ATLAS: New All-silicon Inner Tracker Long Barrel Strips Forward Strips Short Barrel Strips Signal vs dose (1 MeV n equivalent) Barrel pixel RD50 Forward pixel Baseline layout of the new ATLAS inner tracker for HL-LHC Aim to have at least 14 silicon hits everywhere (robust tracking) Microstrip Stave Prototype Quad Pixel Module Quad Pixel Sensor Wafer 34

New All-silicon Inner Tracker Pixel Detector n-implant planar, 3D and diamond sensors proved to doses up to 2 10 16 n eq /cm 2 (~10 MGy) Use 65nm CMOS technology for 2cm 2cm read-out chips bump-bonded with 50µm 50µm or 25µm 100µm pixels Test structures in 65nm produced and studied after irradiation Larger area sensors (150µm thick) quads (4cm 4cm) produced on high resistivity wafers with several foundries Irradiated quad pixel modules studied in test-beam with excellent performance Need radiation-hard optical read-out (~10Gb/s) and low mass micro-cables Support designs prototyped and service routings have been studied Quad Sensor Forward Pixel Rings RD50 16 32 pixels in 65nm CMOS Possible Barrel Support Concept Forward Pixel Services 35

New All-silicon Inner Tracker Strip Detector New prototype n-electrode sensors delivered with 4 rows of 2.4cm long strips at 74.5µm pitch New (256 channel) 130nm CMOS ASIC received and working well (97% yield) Many strip modules (single and double sided) prototyped with 250nm ASICs Large area stave DC-DC prototype (130cm 10cm) produced and under study New hybrids for 130nm ASIC Serial and DC-DC powering studied in detail on short versions of 250nm stave Several other new custom chips also needed Hybrid/module designs to use these completed Module with on-board DC-DC converter 4 row wire bonds Local supports extensively prototyped and further material reduction achieved Progress in Petal and Stave support designs End-of-stave card for 130nm developed Fully functional forward module

Stave: Hybrids glued to Sensors glued to Bus Tape glued to Cooling Substrate Glue Glue Current Prototypes 250nm ASIC Designs 1.2m 1.3m Carbon-fibre facing with CF honeycomb and carbon foam around titanium pipes with CO 2 high pressure bi-phase cooling

Potential technologies under study to bring some of the advantages of monolithic active pixel sensor (MAPS) technology to the HL-LHC HV/HR-CMOS R&D MAPS already installed at the Relativistic Heavy Ion Collider at Brookhaven, USA Some key fundamental issues around HV/HR-CMOS sensors are not yet fully understood, in particular the charge collection and efficiencies (especially after irradiation) but also time slewing, which all need further R&D A reasonably sized detector still needs to be demonstrated in a beam with particles 38

Conclusions The understanding of the full physics potential of the HL-LHC is advancing rapidly, with greatly increased activity on both detector and accelerator preparations following the adoption by CERN Council of the Updated European Strategy for Particle Physics, with the HL-LHC as its highest priority ATLAS has a coherent plan for upgrades through the coming decade to meet the challenges up to and including the HL-LHC era. There are designs for a replacement tracker that should withstand both the pile-up and radiation conditions at the HL-LHC with performance able to not just fully recover, but also improve on, the current vertex finding and tracking capabilities at low pile-up. There are many opportunities for advanced technologies in sensors, radiation-hard electronics, powering, advanced low-mass composites, optical read-out, data acquisition systems and computing. The UK participants in ATLAS, with the support of STFC, are playing major roles in key aspects of the LHC and HL-LHC programmes. 39

Projected ATLAS Upgrade Costs Total New Inner Detector LAr Muon Tile TDAQ 40

Discovery of the Higgs at the LHC The Higgs mass is measured to be 125.36 ± 0.41 GeV, corresponding to about 130 times the mass of the proton