# 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

• Aaboud, M 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 (5): (2019)
• Aaboud M 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 (5): (2019)
• Aaboud M 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 (11): (2018)
• Aaboud, M 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 (1): (2018)
• Aaboud M 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 (6): (2018)
• Aaboud M 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 (7): (2018)
• Aaboud M 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 (7): (2018)
• Aaboud, M et al.
Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector
Physical Review d. 97 (7): (2018)
• Aaboud M 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 (9): (2018)
• Aaboud M et al.
Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector
Physics Letters b. 784173-191 (2018)
• Aaboud M et al.
Operation and performance of the ATLAS Tile Calorimeter in Run 1
European Physical Journal c. 78 (12): 987- (2018)
• Aaboud, M 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 (21): 211801- (2018)
• Aaboud, M 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 (9): (2018)
• Aaboud M 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 (7): (2018)
• Aaboud M 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 (10): (2018)
• Aaboud M 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 (1): 467- (2018)
• Aaboud M 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 (12): (2017)
• Aaboud M 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 (5): (2017)
• Aaboud M 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 (11): (2017)
• Aaboud M 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 (11): (2017)
Search for lepton-flavour-violating decays of the Higgs and Z bosons with the ATLAS detector
European Physical Journal c. 77 (2): 70- (2017)
• Aaboud M et al.
Performance of the ATLAS trigger system in 2015
European Physical Journal c. 77 (5): 317- (2017)
• Aaboud M 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 (8): 531- (2017)
Search for bottom squark pair production in proton–proton collisions at $\sqrt{s}=13$  TeV with the ATLAS detector
European Physical Journal c. C76 (10): 547- (2016)
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. 761136-157 (2016)
• Aaboud M et al.
Luminosity determination in pp collisions at √s = 8 TeV using the ATLAS detector at the LHC
European Physical Journal c. 76 (12): 467- (2016)
• Aaboud M 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 (11): 467- (2016)
• Abdallah, J et al.
The Laser calibration of the ATLAS Tile Calorimeter during the LHC run 1
Journal Of Instrumentation. 11 (UNSP T10005): (2016)
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 (3): 032005- (2016)
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 (9): 074- (2016)
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 (3): (2016)
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 (8): 045- (2016)
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 (1): 1-51 (2016)
• Atlas Collaboration 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 (5): (2016)
• Atlas Collaboration 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 (2): 467- (2016)
• Atlas Collaboration 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 (8): NA (2015)
• Atlas Collaboration et al.
Measurements of the top quark branching ratios into channels with leptons and quarks with the ATLAS detector
Physical Review d. 92 (7): NA (2015)
• Atlas Collaboration 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 (11): (2015)
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 (7): 299- (2015)
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 (7): 349-50 (2015)
• The ATLAS collaboration 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 (9): (2015)
• The ATLAS collaboration 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 (10): (2015)
• The ATLAS collaboration 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 (10): (2015)
• Casolino, Mirkoantonio et al.
Probing a light CP-odd scalar in di-top-associated production at the LHC
European Physical Journal c. 75 (10): (2015)
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 (1): (2015)
ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider
European Physical Journal c. 75 (10): 1-48 (2015)
• The ATLAS collaboration 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 (8): (2015)
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 (11): (2015)
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 (11): (2015)
• Aguilar-Saavedra et al.
Asymmetries in top quark pair production at hadron colliders
Reviews Of Modern Physics. 87 (2): 421-455 (2015)
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 (19): 191803- (2015)
• The ATLAS collaboration 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 (12): 1-65 (2015)
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 (3): (2015)
• Junk et al.
Review of physics results from the Tevatron: Higgs boson physics
International Journal Of Modern Physics a. 30 (6): (2015)
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 (2): 92- (2015)
• Aaltonen, T et al.
Studies of high-transverse momentum jet substructure and top quarks produced in 1.96 TeV proton-antiproton collisions
Physical Review d. 91 (3): (2015)
• Aaltonen T 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 (1): (2015)
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. B740222-242-242 (2015)
Search for Scalar Charm Quark Pair Production in $pp$ Collisions at $\sqrt{s}=$ 8 TeV with the ATLAS Detector
Physical Review Letters. 114 (16): 161801- (2015)
• ### 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

New Member

New Member in the ATLAS Pixels group

May 26, 2022

Yujing Gan has just joined the ATLAS Pixels group as a PhD student. She got her bachelor degree in the Central China Normal University (CCNU).

Instrumentation

ATLAS pixels group milestone towards ITk module production

April 6, 2022

IFAE´s ATLAS pixels group has achieved a new milestone towards the ATLAS ITk Pixel module production.

New Member

New member of the ATLAS group

February 16, 2022

Judita Mamužić has just started as a new postdoc of the ATLAS Group.

Instrumentation

New HGTD project milestone

February 9, 2022

The first results of charge collection in ALTIROC2 prototypes for HGTD have been carried out at IFAE.

In the Media

Martine Bosman interviewed on the La Mira online magazine

January 12, 2022

Martine Bosman has been interviewed in the La Mira online Magazine

New Paper

New ATLAS pixel group paper

January 12, 2022

Characterization of Irradiated Boron, Carbon-Enriched and Gallium Si-on-Si Wafer Low Gain Avalanche Detectors” by L. Castillo García and others, has been published in a special issue of Instruments journal dedicated to Timing Detectors.