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Peter Krieger


Experimental High Energy Physics

Telephone: (416) 978-2950
Fax: (416) 978-8221

Research Other ATLAS Activities Other Professional Activities Talks Papers Courses

BSc., Dalhousie (1985)
MSc, University of Toronto (1988)
PhD, University of Toronto (1994)
Research Associate, Carleton University (OPAL) (1994-1998),
Research Associate, Carleton University (ATLAS/OPAL) (1998-2001),
IPP Research Scientist/Assistant Professor, University of Toronto (2001-2004),
Associate Professor, University of Toronto (2005 - 2014)
Professor, University of Toronto (2014-)

Research Activities

My research focus is ultimately on the search for physics beyond the so-called Standard Model of Particle Physics. The next few years will be an especially exciting time for our field. In Sept. 2008 CERN's Large Hadron Collider (LHC), the highest-energy collider ever constructed, circulated proton beams for the first time, an event that was well publicized in the national and international press. An equally well publicised incident required the shutdown of the LHC soon thereafter, for repairs that were completed in mid-2009. The LHC is scheduled to begin producing proton-proton collisions in late 2009 and to run for about one year before shutting down for further maintenance. Because the fundamental interactions occuring in such collisions are between constituents of the protons, such collisions sweep out a range of centre-of-mass energies up to a maximum of 14 TeV. This is a feature of hadron colliders that makes them particularly well suited to the discovery of new phenomena. Since 2010 the LHC has operated in a cycle of multi-year data-taking periods (Runs) alternating with long shutdown periods (LS) used for maintenance, repairs and detector upgrades. Run-1 ended in 2012 and accumulated the dataset that was ultimately used for the discovery of the Higgs boson (see below). After the first long-shutdown period (LS1) data-taking resumed in 2015, with Run-2 lasting until the end of 2018. This was followed by LS2, which was used to install (Phase-1) detector upgrades to ensure the ability of the ability of the detector to operate at the higher luminosities planned for the future. The shudown was prolonged, in part due to the effects of the COVID19 pandemic, with the next data-taking periof (Run-3, now in progress) starting in 2022.

The current theory describing our understanding of the fundamental constituents of matter and their interactions, the Standard Model, has been extraordinarily successful and has survived all the experimental tests to which it has so far been subjected, some of them tremendously precise. The Large Electron-Positron (LEP) collider at CERN was decomissioned in 2001 after over a decade of data taking, at centre-of-mass energies between 90 and 209 GeV, which resulted in confirmation of the Standard Model to very high precision, especially in the electroweak sector which it was designed to study (see LEP Electroweak Working Group web pages ).

However, despite the successes of the Standard Model, there are strong theoretical motivations for the widespread belief that this theory represents a low-energy effective theory that cannot survive intact to arbitrarily high energy. Furthermore, some theoretical arguments point to a scale for physics beyond the SM that is around 1 TeV, an energy range that is accessible at the LHC. At the start of the LHC experimental program, the Higgs boson, predicted by the Standard Model, had yet to be observed. It was discovered by the ATLAS and CMS collaborations in 2012. Searches for physics Beyond the Standard Model, however, have so far not found significant evidence for new phenomena. These searches continue.

Several detectors of different types were constructed for use at the LHC. Two of these, CMS and ATLAS, are general purpose detectors designed to have broad capabilities for the discovery of the Higgs boson as well as for new physics searches. The Canadian high-energy physics commumity plays an important role in the ATLAS Collaboration , with responsibilites for construction of significant portions of the liquid-argon calorimeters in the endcap region of the detector. For years, much of my effort was focussed on the completion and testing of the ATLAS forward calorimeter, modules of which were constructed at University of Arizona, Carleton University in Ottawa, and here at U of T. In the summer of 2003 the first full FCal was tested in electron and hadron beams at CERN. First published results from these tests can be found in the publications section, below. In the summer of 2004 the FCal group also took part in tests of a slice of a full endcap calorimeter. This combined endcap testbeam is designed to study the transition region between the forward calorimeters and the other endcap calorimeters, the electromagnetic endcap calorimeter (EMEC) and the hadronic endcap calorimeter (HEC). Published results from this test can be found below. I also served as a commissioning coordinator of the endcap calorimeter, with responsbilities for commissioning without beam.

Since before the start of LHC operations I have been a member of the Liquid Calorimeter Steeting and Management Groups. I am also a longstanding member of the LAr Calorimeter Institute Board.

I have been involved with the ATLAS Phase-2 upgrades since about 2013, serving as the Phase-2 hardware coordinator from 2013-2016 and as the Phase-2 Upgrade Co-convenor from 2015-2017 and as the Phase-2 resources coordinator since 2017.

I served as the Spokesperson of the ATLAS Canada collaboration from 2015 until stepping down in 2023. I remain the project leader for the CFI-funded Phase-2 upgrades of the ATLAS detector, including contributions to the replacement of the on- and off-detector readout electronics of the Liquid Argon calorimter, and the construction of a new all-silicon tracker, the ITk. Funding for this work came from CFI 2017 Innovation Fund competition.

Other ATLAS Activities

Member, ATLAS Liquid Argon Calorimeter Project Leader Search Committee: 2024

Member, ATLAS Panel on Opertating Tasks Sharing (POTS): 2018-2021

Member, ATLAS Publications Committee: 2014-2016

Chair, ATLAS Liquid Argon Calorimeter Speakers Committee: 2015

Member, ATLAS Liquid Argon Calorimeter Speakers Committee: 2012-2014

Other Professional Activities

I have served variously as an external examiner for PhD defences, and a reviewer for promotions reviews in both Canada and Europe.

I have served two three-year terms on the Scientific Council of the Institute of Particle Physics (IPP) and one year as its Secretary Treasurer. I have also served on a number of IPP tenure and promotion review committees.

I have served as a Grant Reviewer for the US DOE as well as on internal Universtiy of Toronto review committees.

I have served as the Associate Chair for Undergraduate Studies at the University of Toronto since July 2019.

Selected Talks

ATLAS Canada Status Report
IPP 50th Anniversary Symposium, Ottawa, May, 2022.

Standard Model and Higgs Physics at the HL-LHC with ATLAS and CMS
LHCP 2016, Lund, Sweden, June, 2016.

Upgrade Plans for ATLAS Forward Calorimetry for the HL-LHC
CHEF 2013, Paris, France, April, 2013.
Contribution to conference record pdf file

Inclusive Jet and Multi-jet Production at ATLAS and CMS
PLHC 2012, Vancouver, BC, June, 2012.

The ATLAS Liquid Argon Calorimeter: One Year of LHC Operation and Future Upgrade Plans for HL-LHC
ANIMMA 2011, Ghent, Belgium, June , 2011.
Contribution to conference record pdf file

First ATLAS Results from Lead-Lead Collisions at the Large Hadron Collider
CAP Congress 2011, St. John's, NL, June, 2011.

The First LHC Beams in ATLAS
Aspen Winter Conference, Aspen, Colorado, February, 2009.

The ATLAS Experiment at the CERN Large Hadron Collider
Invited Talk, WNPPC'08, Banff, February, 2008.

Performance of the ATLAS Liquid Argon Forward Calorimeter in Beam Tests
Como, Italy, October 2007.
Contribution to conference record pdf file

Selected Publications

The ATLAS Detector for the LHC Run-3.
The ATLAS Collaboration (G. Aad et al.), arXiv:2305.16623 , accepted by JINST.

Luminosity determination in pp collisions at 13 TeV using the ATLAS detector at the LHC.
The ATLAS Collaboration (G. Aad et al.), arXiv:2212.09379, EPJC 83 (2023) 982.

The Phase-I Trigger Readout Electronics Upgrade of the ATLAS Liquid Argon Calorimeters.
The ATLAS Liquid Argon Calorimeter Group (G. Aad et al.), arXiv:2202.07384, JINST 17 (2022) P05024.

Search for heavy resonances decaying into a pair of Z bosons in the llll and llvv final states using 139 fb-1 of proton-proton collisions at 13 TeV with the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.), arXiv:2009.14781, EPJC 81 (2021) 332.

Search for dijet resonances in events with an isolated charged lepton using 13 TeV proton-proton collision data collected by the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.), arXiv:2002.11325, JHEP 06 (2020) 151.

Measurement of W±-boson and Z-boson production cross-sections in pp collisions at ps=2.76 TeV with the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.), Eur. Phys. J. C 79 (2019) 901, arXiv:1907.03567 [26 pages].

Measurement of the production cross section for a Higgs boson in association with a vector boson in the H --> WW* --> lvlv channel in pp collisions at 13 TeV with the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.), arXiv:1903.10052, Phys. Lett. B 798 (2019) 134949.

Luminosity determination in pp collisions at 8 TeV using the ATLAS detector at the LHC.
The ATLAS Collaboration (M. Aaboud et al.) Eur. Phys. J. C 76 (2016) 653.

Search for a high-mass Higgs boson decaying to a W boson pair in pp collisions at 8 TeV with the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.) JHEP 01 (2016) 032.

Study of (W /Z)H production and Higgs boson couplings using H ! W W decays with the ATLAS detector.
The ATLAS Collaboration (G. Aad et al.) JHEP 08 (2015) 137.

Observation of a new particle in the search for the Standard Model Higgs Boson with the ATLAS detector at the LHC.
ATLAS Collaboration (G. Aad et al.),
Phys. Lett. B 716 (2012) 1.

The ATLAS Forward Calorimeters
A. Artamonov et al., JINST 3 (2008) P02010

Performance of the ATLAS Liquid Argon Endcap Calorimeter in the Pseudorapidity Region 2.5 < |eta| <4.0 in Beam Tests.
J. Pinfold et al., NIM A 593, (2008) 324-342.

Energy Calibration of the ATLAS Liquid Argon Forward Calorimeter
J.P. Archambault et al., JINST 3 (2008) P02002

Electron Signals in the Forward Calorimeter Prototype for ATLAS
J.C. Armitage et al., JINST 2 (2007) P11001.

Graduate Students

Kyle Amirie 2022-

Sahibjeet Singh 2020-2024 High Energy Physics at Low(er) Energies: Precision Measurements in Top Quark Physics at 5.02 TeV.

Sana Ketabchi Haghighat 2016-2022 Measurement of the cross section of the Higgs boson production in association with a Z boson and decaying into WW* .

Joseph Carter 2016-2022 Luminosity studies and a search for heavy resonances decaying into a pair of Z bosons with the ATLAS detector.

Vincent Pascuzzi 2015-2019 Looking for Beyond the Standard Model Physics in Dijet-Plus- Lepton Final-State Events Collected with the ATLAS Detector.

Aaron Liblong 2013-2019 Search for Associated production of the Higgs boson with the ATLAS detector

Ossama AbouZeid 2009-2015 The Search for a Heavy Higgs Boson in the H --> WW* --> lvjj Channel with the ATLAS Detector.

Peter Thompson 2006-2013 Measurement of the Inclusive Jet and Dijet Cross-sections using 2010 Data from the ATLAS Detector and Calibration Studies and Simulation of the ATLAS Forward Calorimeter.

Gabriel Rosenbaum 2005-2010 Dijet Azimuthal Decorrelations in pp Collisions at 7 TeV.


In recent years I have taught mainly in our Undergraduate Advanced Lab

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