# Collider Physics Group

• ### Collider Physics Group

CERN’s Large Hadron Collider (LHC) delivered the first high-energy proton-proton collisions in 2010, opening a new energy frontier in particle physics. ATLAS is one of the four large detectors at the LHC involving about 3000 scientists. With a 25-year involvement in the ATLAS experiment, IFAE has strongly contributed to a broad spectrum of topics critical to the scientific exploitation of the experiment

The Collider Physics group at IFAE is led by M. Bosman.

### The ATLAS Tile Hadronic Calorimeter (TileCal)

IFAE played a central role in the design, construction and commissioning of the Tile hadronic Calorimeter (TileCal), finished in 2009. Since 2010, IFAE strongly contributes to various aspects of the TileCal operation, data reconstruction, calibration, data quality monitoring, and luminosity measurement. IFAE researchers often act as TileCal run coordinators. During the last years the group has led the R&D for the new structure hosting the upgraded front-end electronics, needed for the high luminosity LHC (HL-LHC) period starting in 2027. The production of the new structures started in 2019 and is expected to last 3 years.

### The ATLAS Trigger and Data Aquisistion (TDAQ)

IFAE has contributed to the development and operation of the data acquisition and event selection system (trigger), critical for an efficient selection of the most interesting collisions. IFAE was one of three groups developing the software infrastructure of the high-level trigger and held several coordinating responsibilities within the ATLAS trigger group. IFAE also played a key role in developing the algorithms for the selection of events with tau leptons, later extended to jet triggers. In order to cope with the higher luminosity of Run 2 (2015-2018), ATLAS installed a new processor to perform real-time event selection based on topological variables. IFAE made major contributions to the simulation of the processor, its commissioning and validation with data. Moreover, IFAE contributed to the operations of the whole trigger system with the overall coordination of the trigger menu. The trigger work at IFAE will continue in preparation for the new Run 3 scheduled for spring 2022.

### Physics Analysis Program

The institute deployed a strong and rich physics analysis program at the LHC, expanding from precise Standard Model background measurements to Higgs boson physics. During Run 2, when LHC collided protons at a center-of-mass energy of 13 TeV, IFAE developed a broad program of searches for new phenomena, including dark matter, invisible Higgs boson decays, supersymmetry, compositeness, new heavy Higgs bosons, as well as precise measurements of the interactions between the top and bottom quarks and the Higgs boson. IFAE, which represents about 1% of ATLAS, directly contributes to about 10% of ATLAS publications. IFAE researches have held a number of physics-related coordination positions. Most notably, A. Juste is the current co-coordinator of the ATLAS Exotics Physics Working Group.

### Data processing of the LHC data

IFAE is a main actor in the data processing of the LHC data. In 2003, IFAE and CIEMAT founded the Port d’Informació Científica (PIC), one of 13 LHC Tier-1 data centers in the world and the only one in Spain. As such, PIC participates in the overall effort of processing and distributing the tens of PB of data the LHC produces every year. Year after year, PIC, which operates 24/7, is listed in the top three of Tier-1 centers in terms of reliability.

### 3D silicon pixel sensors for ATLAS

IFAE in collaboration with the CNM center in the UAB campus led the development of the ultra-radiation-hard 3D silicon pixel sensors for ATLAS. The institute made key contributions to the current detector systems based on this technology: providing 3D sensors for the innermost pixel layer (IBL) in 2014 and constructing in 2016 the first stations for the ATLAS Forward Protons (AFP) tracking system, finished in 2020. Recently, the design of the 3D sensors has been adapted to satisfy the HL-LHC requirements, and the technology has been selected for the innermost layer of the new ATLAS tracking system. IFAE is now preparing to produce the pixel modules and deliver them to CERN in the mid 2020s. This is arguably the most demanding piece of instrumentation of ATLAS: a 250-um-thick silicon sensor that will reside 3cm away from the interaction point and that has to provide excellent position resolution during many years of LHC operation in a high radiation environment.

### High Granularity Timing Detector (HGTD)

IFAE has been deeply involved in the R&D effort to design and fabricate a timing detector to mitigate the effect of pile-up at the HL-LHC. Using timing, one can identify the origin of the reconstructed tracks, thus reducing the effect of overlapping collisions. IFAE proposed the Low Gain Avalanche Detector (LGAD) technology developed at CNM to be used in a High Granularity Timing Detector (HGTD), demonstrating that LGAD sensors can provide the needed time resolution in the presence of the expected large radiation doses. After its adoption by ATLAS, IFAE is now working on the corresponding ASIC design and has developed the hybridization process for the HGTD.

### High temperature superconductor coated conductors for the Future Circular Collider (FCC-hh)

A collaboration between CERN and Spanish centers ICMAB, UPC, ALBA and IFAE was established in 2016 to evaluate high temperature superconductor coated conductors (HTS-CC) as candidates for the beam screens of the Future Circular Collider (FCC-hh). To study its properties under mechanical stress, IFAE designed and built a dedicated machine that holds a large sample of powered HTS-CC, applies mechanical stress to it, and measures the distributions of mechanical deformation and current density over its surface. The work was funded by CERN for three years (2016-19), was very positively reviewed, and has been recently extended to build a proof-of-concept FCC-hh beam screen device based on HTS-CC.

• ### Group Members

Collider Physics Group

• ### International Collaborations

Collider Physics Group

ATLAS

ATLAS at the LHC

ATLAS is one of the four major experiments at the Large Hadron Collider (LHC) at CERN. It is a general-purpose particle physics experiment designed to exploit the full discovery potential and the huge range of physics opportunities that the LHC provides.

CERN, Geneva, Switzerland
• ### Research Projects

Collider Physics Group

AIDA-2020

Advanced European Infrastructures for Detectors at Accelerators

The AIDA-2020 project brings together the leading European research infrastructures in the field of detector development and testing and a number of institutes, universities and technological centers, thus assembling the necessary expertise for the ambitious programme of work.

• ### Selected Publications

Collider Physics Group

• Aad, G et al.,
Search for four-top-quark production in the single-lepton and opposite-sign dilepton final states in pp collisions at root s=13 TeV with the ATLAS detector,
Physical Review d 99 (2019) [DOI]
• Aad G et al.,
Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √s = 13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2019 (2019) [DOI]
• Aad G et al.,
Search for supersymmetry in final states with charm jets and missing transverse momentum in 13 TeV pp collisions with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad, G et al.,
Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad, G et al.,
Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector,
Physical Review d 97 (2018) [DOI]
• Aad G et al.,
Search for the standard model Higgs boson produced in association with top quarks and decaying into a b b pair in pp collisions at s =13 TeV with the ATLAS detector SEARCH for the STANDARD MODEL HIGGS BOSON ? M. AABOUD et al.,
Physical Review d 97 (2018) [DOI]
• Aad G et al.,
Search for supersymmetry in final states with missing transverse momentum and multiple b-jets in proton-proton collisions at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad G et al.,
Search for dark matter produced in association with bottom or top quarks in ?s=13 TeV pp collisions with the ATLAS detector,
European Physical Journal c 78 (2018) [DOI]
• Aad G et al.,
Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector,
Physics Letters b 784 (2018) [DOI]
• Aad G et al.,
Search for flavour-changing neutral current top-quark decays t → qZ in proton-proton collisions at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad G et al.,
Search for the Higgs boson produced in association with a vector boson and decaying into two spin-zero particles in the H → aa → 4b channel in pp collisions at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad, G et al.,
Search for pair production of Higgsinos in final states with at least three b-tagged jets in root s=13 TeV pp collisions using the ATLAS detector,
Physical Review d 98 (2018) [DOI]
• Aad G et al.,
Search for charged Higgs bosons decaying into top and bottom quarks at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Aad, G et al.,
Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at root s=13 TeV with the ATLAS Detector,
Physical Review Letters 121 (2018) [DOI]
• Aad G et al.,
Operation and performance of the ATLAS Tile Calorimeter in Run 1,
European Physical Journal c 78 (2018) [DOI]
• Aad G et al.,
Search for pair production of up-type vector-like quarks and for four-top-quark events in final states with multiple b-jets with the ATLAS detector,
Journal Of High Energy Physics 2018 (2018) [DOI]
• Abbott B et al.,
Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector,
European Physical Journal c 77 (2017) [DOI]
• Aad G et al.,
Performance of the ATLAS trigger system in 2015,
European Physical Journal c 77 (2017) [DOI]
• Aad G et al.,
Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8 TeV using data collected by the ATLAS detector,
European Physical Journal c 77 (2017) [DOI]
• Aad G et al.,
Search for new phenomena in dijet events using 37 fb-1 of pp collision data collected at s =13 TeV with the ATLAS detector,
Physical Review d 96 (2017) [DOI]
• Aad G et al.,
Search for supersymmetry in events with b-tagged jets and missing transverse momentum in pp collisions at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2017 (2017) [DOI]
• Aad G et al.,
Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at √s=13 TeV with the ATLAS detector,
Journal Of High Energy Physics 2017 (2017) [DOI]
• Aad G et al.,
Search for dark matter in association with a Higgs boson decaying to two photons at ?s=13 TeV with the ATLAS detector,
Physical Review d 96 (2017) [DOI]
• Aad, Georges et al.,
Measurement of jet activity in top quark events using the $e\mu$ final state with two $b$-tagged jets in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector,
Journal Of High Energy Physics 1609 (2016) [DOI]
• Barreiro Alonso, Fernando et al.,
Search for the Standard Model Higgs boson decaying into b(b)over-bar produced in association with top quarks decaying hadronically in pp collisions at root s=8 TeV with the ATLAS detector,
Journal Of High Energy Physics 2016 (2016) [DOI]
• Barreiro Alonso, Fernando et al.,
Measurement of the charge asymmetry in top-quark pair production in the lepton-plus-jets final state in pp collision data at root s=8 TeV with the ATLAS detector,
European Physical Journal c 76 (2016) [DOI]
• Aad G et al.,
Luminosity determination in pp collisions at √s = 8 TeV using the ATLAS detector at the LHC,
European Physical Journal c 76 (2016) [DOI]
• Aad G et al.,
Search for the Higgs boson produced in association with a W boson and decaying to four b-quarks via two spin-zero particles in pp collisions at 13 TeV with the ATLAS detector,
European Physical Journal c 76 (2016) [DOI]
• Alexa, C et al.,
The Laser calibration of the ATLAS Tile Calorimeter during the LHC run 1,
Journal Of Instrumentation 11 (2016) [DOI]
• Abbott B et al.,
Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at √S=7 and 8 TeV in the ATLAS experiment,
European Physical Journal c 76 (2016) [DOI]
• Abbott, Brad et al.,
Search for pair production of gluinos decaying via stop and sbottom in events with $b$-jets and large missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector,
Physical Review d 94 (2016) [DOI]
• Abbott, Brad et al.,
Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at $\sqrt{s}=7$ and 8 TeV,
Journal Of High Energy Physics 1608 (2016) [DOI]
• Aad, Georges et al.,
Measurement of the $t\bar{t}$ production cross-section using $e\mu$ events with b-tagged jets in pp collisions at $\sqrt{s}$=13 TeV with the ATLAS detector,
Physics Letters b 761 (2016) [DOI]
• Aad, Georges et al.,
Search for bottom squark pair production in proton–proton collisions at $\sqrt{s}=13$  TeV with the ATLAS detector,
European Physical Journal c C76 (2016) [DOI]
• Aad, Georges et al.,
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in $pp$ collisions at $\sqrt{s}=13$ TeV using the ATLAS detector,
Physical Review d D94 (2016) [DOI]
• Aad G et al.,
Search for production of vector-like quark pairs and of four top quarks in the lepton-plus-jets final state in pp collisions at (formula presented.) TeV with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Abbott B et al.,
Search for the Standard Model Higgs boson produced in association with top quarks and decaying into bb in pp collisions at √s = 8 TeV with the ATLAS detector,
European Physical Journal c 75 (2015) [DOI]
• Abbott B et al.,
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √S=8 TeV with the ATLAS detector,
European Physical Journal c 75 (2015) [DOI]
• Aad G et al.,
Measurement of the forward-backward asymmetry of electron and muon pair-production in pp collisions at (Formula Presented.) = 7 TeV with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Barreiro Alonso, Fernando et al.,
Measurements of the top quark branching ratios into channels with leptons and quarks with the ATLAS detector,
Physical Review d 92 (2015) [DOI]
• Barreiro Alonso, Fernando et al.,
A search for t(t)over-bar resonances using lepton-plus-jets events in proton-proton collisions at root s=8 TeV with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Aad G et al.,
Summary of the searches for squarks and gluinos using √s = 8 TeV pp collisions with the ATLAS experiment at the LHC,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Aad G et al.,
Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Abbott B et al.,
ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider,
European Physical Journal c 75 (2015) [DOI]
• Aad G et al.,
Search for flavour-changing neutral current top quark decays t → Hq in pp collisions at √s=8 TeV with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Barreiro Alonso, Fernando et al.,
Search for pair production of a new heavy quark that decays into a W boson and a light quark in pp collisions at root s=8 TeV with the ATLAS detector,
Physical Review d 92 (2015) [DOI]
• J A Amidei et al.,
Asymmetries in top quark pair production at hadron colliders,
Reviews Of Modern Physics 87 (2015) [DOI]
• Farooque, Trisha et al.,
Probing a light CP-odd scalar in di-top-associated production at the LHC,
European Physical Journal c 75 (2015) [DOI]
• Thomas R Juste et al.,
Review of physics results from the Tevatron: Higgs boson physics,
International Journal Of Modern Physics a 30 (2015) [DOI]
• Alon, R et al.,
Studies of high-transverse momentum jet substructure and top quarks produced in 1.96 TeV proton-antiproton collisions,
Physical Review d 91 (2015) [DOI]
• Amerio S et al.,
Measurement of differential production cross sections for Z /γ∗ bosons in association with jets in p p ¯ collisions at s =1.96TeV,
Physical Review d 91 (2015) [DOI]
• Abbott, Brad et al.,
Search for $H \to \gamma\gamma$ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector,
Physics Letters b B740 (2015) [DOI]
• Abbott, Brad et al.,
Search for the $b\bar{b}$ decay of the Standard Model Higgs boson in associated $(W/Z)H$ production with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Abbott, Brad et al.,
Search for dark matter in events with heavy quarks and missing transverse momentum in $pp$ collisions with the ATLAS detector,
European Physical Journal c 75 (2015) [DOI]
• Abbott, Brad et al.,
Search for charged Higgs bosons decaying via $H^{\pm} \rightarrow \tau^{\pm}\nu$ in fully hadronic final states using $pp$ collision data at $\sqrt{s} = 8$ TeV with the ATLAS detector,
Journal Of High Energy Physics 2015 (2015) [DOI]
• Abbott, Brad et al.,
Search for Scalar Charm Quark Pair Production in $pp$ Collisions at $\sqrt{s}=$ 8 TeV with the ATLAS Detector,
Physical Review Letters 114 (2015) [DOI]
• Abbott, Brad et al.,
Search for vector-like $B$ quarks in events with one isolated lepton, missing transverse momentum and jets at $\sqrt{s}=$ 8 TeV with the ATLAS detector,
Physical Review d 91 (2015) [DOI]
• Abbott, Brad et al.,
Combined Measurement of the Higgs Boson Mass in $pp$ Collisions at $\sqrt{s}=7$ and 8 TeV with the ATLAS and CMS Experiments,
Physical Review Letters 114 (2015) [DOI]
• Abbott, Brad et al.,
Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in the lepton+jets final state with ATLAS,
Physical Review d 91 (2015) [DOI]
• ### Instrumentation Projects

Collider Physics Group

3D Pixels

3D silicon pixel sensors  (ATLAS)

IFAE in collaboration with CNM led the development of the ultra-radiation-hard 3D silicon pixel sensors for ATLAS. IFAE provided 3D sensors for the innermost pixel layer (IBL) and constructed the first stations for the ATLAS Forward Protons (AFP) tracking system.

HGTD

High Granularity Timing Detector  (ATLAS)

IFAE has been deeply involved in the R&D effort to design and fabricate a timing detector to mitigate the effect of pile-up at the HL-LHC. IFAE proposed and demonstarted the Low Gain Avalanche Detector (LGAD) technology developed at CNM to be used in a HGTD detector.

HTS-CC

High temperature superconductor coated conductors

A collaboration between CERN and Spanish centers ICMAB, UPC, ALBA and IFAE was established in 2016 to evaluate high temperature superconductor coated conductors (HTS-CC) as candidates for the beam screens of the Future Circular Collider (FCC-hh).

• ## Group News

Workshop

Red LHC workshop

May 12, 2021

The IFAE-ATLAS group participates in the RED LHC Workshop 10-12 May 2021

Collaboration Meeting

ATLAS physics and performance week

May 5, 2021

The ATLAS physics and performance week is taking place this week. Aurelio Juste is giving the plenary talk “Implication of anomalies (muon g-2, R(K), etc.) for the Exotics program

New Publication

New ATLAS Pixels Group Publication

April 28, 2021

The Paper “Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker” has been published in Frontiers for Physics.

New Appointment

Sebastian Grinstein endorsed as deputy Project Leader of the ATLAS HGTD

April 28, 2021

Sebastian Grinstein has been endorsed as deputy Project Leader of the High Granularity Timing Detector (HGTD) of ATLAS by the Institute Board.

Collaboration Meeting

ATLAS Upgrade week

April 21, 2021

The ATLAS Upgrade Week will take place next week (online). IFAE members will be presenting results and convening various sessions in the ITk Pixels and HGTD upgrade projects.

Conference

XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects

April 14, 2021

The XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects is taking place as a virtual event on April 12-16, 2021 Stergios Kazakos contribute with the talk “Searching for leptoquarks with the ATLAS detector”.