Particle Physics

Particle physics is the science which identifies nature's constituents and interactions at the most fundamental level, with an emphasis on comparing theoretical ideas with both terrestrial experiments and astrophysical observations. This mandate gives it a strong overlap with string theory, quantum gravity and cosmology. Particle physicists at Perimeter Institute are currently involved in identifying how cosmological observations and terrestrial accelerator and underground experiments constrain the theoretical possibilities for physics beyond the Standard Model.

Displaying 697 - 708 of 1410

Sequestering the Standard Model Vacuum Energy

Nemanja Kaloper
University of California System
February 21, 2014

PIRSA:14020109
Particle Physics
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders

Sunghoon Jung
Korea Institute for Advanced Study
January 16, 2014

PIRSA:14010103
Particle Physics
Beyond the Standard Paradigm

Paul Langacker
Institute for Advanced Study (IAS)
January 15, 2014

PIRSA:13010116
Particle Physics
No GUTs, All Glory: Charge Quantization and the Standard Model from Nonlinear Sigma Models

John Kehayias
University of Tokyo
December 06, 2013

PIRSA:13120056
Particle Physics
BBN and the Unnatural Weak Scale

David Pinner
University of California, Berkeley
December 05, 2013

PIRSA:13120058
Particle Physics
Using the Higgs as a Direct Probe of New Physics

Michael Park
Rutgers University
December 05, 2013

PIRSA:13120050
Particle Physics
Jets Without Jets

Daniele Bertolini
Massachusetts Institute of Technology (MIT)
December 04, 2013

PIRSA:13120052
Particle Physics
Fully exploring exotic production of the 125 GeV Higgs

Felix Yu
Fermi National Accelerator Laboratory (Fermilab)
December 03, 2013

PIRSA:13120047
Particle Physics
Cornering Gluinos at the LHC

Jared Evans
Rutgers University
December 02, 2013

PIRSA:13120057
Particle Physics
Insightful supersymmetry

Erich Poppitz
University of Toronto
November 27, 2013

PIRSA:13110061
Particle Physics
Classical Space Times from S Matrices

Ira Rothstein
Carnegie Mellon University
November 26, 2013

PIRSA:13110053
Particle Physics
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics

Sequestering the Standard Model Vacuum Energy

Nemanja Kaloper
University of California System
February 21, 2014

PIRSA:14020109
Particle Physics
We propose a very simple reformulation of General Relativity, which completely sequesters from gravity {\it all} of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the universe. For them to be nonzero, the universe should be finite in spacetime. If this matter is the Standard Model of particle physics, our mechanism prevents any of its vacuum energy, classical or quantum, from sourcing the curvature of the universe. The mechanism is consistent with the large hierarchy between the Planck scale, electroweak scale and curvature scale, and early universe cosmology, including inflation. Consequences of our proposal are that the vacuum curvature of an old and large universe is not zero, but very small, that wDE≃−1 is a transient, and that the universe will collapse in the future.
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders

Sunghoon Jung
Korea Institute for Advanced Study
January 16, 2014

PIRSA:14010103
Particle Physics
Discovery of the Higgs boson and lack of discovery of superpartners in the first run at LHC are both predictions of split supersymmetry with thermal dark matter. We discuss what it would take to find gluinos at hadron supercolliders, including the LHC at 14 TeV center of mass energy, and future pp colliders at 100 TeV and 200 TeV. We generalize the discussion by re-expressing the search capacity in terms of gluino to lightest superpartner mass ratio, and apply results to other scenarios, such as gauge mediation and mirage mediation. In those models, distinctive gaugino mass ratios arise at leading order, but can be significantly modified by large logarithmic quantum corrections from split spectrum.
Beyond the Standard Paradigm

Paul Langacker
Institute for Advanced Study (IAS)
January 15, 2014

PIRSA:13010116
Particle Physics
I reexamine the current situation in particle and neutrino physics from a top-down perspective, discussing such underlying issues as uniqueness versus environment, minimality versus remnants, and naturalness versus tuning.
No GUTs, All Glory: Charge Quantization and the Standard Model from Nonlinear Sigma Models

John Kehayias
University of Tokyo
December 06, 2013

PIRSA:13120056
Particle Physics
I will present recent and ongoing work in collaboration with Tsutomu Yanagida and Simeon Hellerman (arXiv:1309.0692 and 1312.xxxx) on a new way to obtain charge quantization, without a GUT or monopole solution. In the CP^1 model, SU(2)_G/U(1)_H, consistency conditions for a charged field and its transformation properties over the entire group manifold lead to a charge quantization condition. By gauging the U(1)_H and identifying it with hypercharge, we find charge quantization in the SM without a monopole or GUT, purely from the structure and dynamics of the nonlinear sigma model. This is easily extended to CP^2 and general CP^k models. Phenomenologically, the CP^1 model has a fractionally charged stable Nambu-Goldstone boson (NGB), which has intriguing applications to nuclear physics and dark matter. The CP^2 model has the Higgs as the NGB. With some additional minor assumptions, anomaly freedom then leads to the matter content of a generation in the SM.
BBN and the Unnatural Weak Scale

David Pinner
University of California, Berkeley
December 05, 2013

PIRSA:13120058
Particle Physics
The discovery of a perturbatively-coupled, 125 GeV Higgs, together with the absence of LHC signals for supersymmetry, places the principle of naturalness under tension. In this talk I will discuss the possibility that the weak scale is unnatural, with its value determined environmentally in the landscape. In particular, this environmental selection may be driven by BBN: as the weak scale is increased, the abundance of Hydrogen in the early universe is rapidly depleted. That our own universe contains an O(1) fraction of primordial Helium arises as a conspiracy among the weak scale, the neutron-proton mass difference, and the planck scale.
Using the Higgs as a Direct Probe of New Physics

Michael Park
Rutgers University
December 05, 2013

PIRSA:13120050
Particle Physics
The discovery of the Higgs boson marks the first direct probe into the mechanism of electroweak symmetry breaking. All evidence currently points to the fact that electroweak symmetry is broken by at least one fundamental scalar, and naturalness remains the most compelling reason to expect additional degrees of freedom at the weak scale. This talk will describe some ideas for how to utilize powerful and proven experimental techniques, in conjunction with the fact that observables directly related to the Higgs boson are now experimentally accessible, to make concrete statements about the existence of possible new degrees of freedom at the weak scale.
Jets Without Jets

Daniele Bertolini
Massachusetts Institute of Technology (MIT)
December 04, 2013

PIRSA:13120052
Particle Physics
Jets are key tools for physics at the LHC. Usually, jets are identified through a jet algorithm. In this talk, I will present an alternative way of thinking about jets, by showing how a broad class of inclusive jet-based observables can be replaced by event shapes. These event shapes do not require any jet clustering, but they still implement a jet-like pT cut on "jets" with an R-like radius. I will discuss various applications, including event selection at trigger-level, event-wide trimming, and alternative definitions for boosted objects identifiers.
Fully exploring exotic production of the 125 GeV Higgs

Felix Yu
Fermi National Accelerator Laboratory (Fermilab)
December 03, 2013

PIRSA:13120047
Particle Physics
I consider the effects of exotic production modes of the 125 GeV Higgs and their impact on Higgs searches and the Higgs discovery. I emphasize that new production modes have been largely overlooked in contemporary tests of the Standard Model nature of the Higgs boson but experimental tests of exotic production modes are viable now or will be soon. I present a couple explicit examples of exotic production arising from chargino-neutralino associated production in the MSSM. As a corollary of this work, I point out that current Higgs coupling fits do not adequately explore the complete space of new physics deviations possible in Higgs measurements.
Cornering Gluinos at the LHC

Jared Evans
Rutgers University
December 02, 2013

PIRSA:13120057
Particle Physics
Gluinos are expected to be light for a natural electroweak scale, but the LHC has not seen them yet. Many possibilities have been proposed to hide natural gluinos in the LHC data, but are these methods really effective? In this talk, I will discuss the current status of kinematically accessible gluinos. By noting the most common features - MET, tops, and high multiplicity - which pervade natural gluino decays, I will argue that there are few places left to hide. I will briefly discuss the remaining weaknesses in LHC coverage and how to bolster them.
Insightful supersymmetry

Erich Poppitz
University of Toronto
November 27, 2013

PIRSA:13110061
Particle Physics
It has recently been realized that some studies of supersymmetric gauge theories, when properly interpreted, lead to insights whose importance transcends supersymmetry. I will illustrate the insightful nature of supersymmetry by two examples having to do with the microscopic description of the thermal deconfinement transition, in non-supersymmetric pure Yang-Mills theory and in QCD with adjoint fermions. A host of strange ``topological" molecules will be seen to be the major players in the confinement-deconfinement dynamics. Interesting connections between topology, ``condensed-matter" gases of electric and magnetic charges, and attempts to interpret the divergent perturbation series will emerge. Much of the presentation will be aimed at non-experts.
Classical Space Times from S Matrices

Ira Rothstein
Carnegie Mellon University
November 26, 2013

PIRSA:13110053
Particle Physics
Progress in calculating S matrix elements have shown that the malicious redundancies in non-linear gauge theories can be circumvented by utilizing unitarity methods in conjunction with BCFW recursion relations. When calculating in this fashion all of the interaction vertices beyond the three point function can be ignored. This simplification is especially useful in gravity which contains an infinite number of such non-linear interactions. It is natural to ask whether off-shell quantities, such as classical solutions, can also be generated using only the three point vertex. In this talk I will show that this is indeed the case by extracting classical solutions to GR from on-hell two to two scattering S-matrix elements. In so doing we will completely circumvent the action as well as the equations of motion. The only inputs will be Lorentz invariance, the existence of a massless spin-two particle and locality. Because of the double copy relation this implies there exists, a yet to be understood, connection between solutions to Yang-Mills theory and Gravity. I will also discuss how this technique can be used to simplify calculations of higher order post-Newtonian corrections to gravitational potentials relevant to the problem of binary inspirals.
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar

Christopher Brust
November 19, 2013

PIRSA:13110051
Particle Physics
The effective number of neutrino species in our universe, Neff, is capable of probing the presence of new light or massless species in our universe. I will first review relevant facts about both CMB measurements of new light species and thermodynamics in the early universe. Then, I will present the effects of many models of BSM physics containing new light species on the CMB, including models containing eV-scale sterile neutrinos compatible with anomalies in neutrino experiments, and interpret the compatibility of the parameter space of these models in terms of the recent results from the Planck satellite. I will argue that the bounds on couplings obtained from the Planck measurement of the CMB are competitive with bounds coming from other areas of physics.

Title	Speaker(s)	Date	Talk Type	Info link
Sequestering the Standard Model Vacuum Energy	Nemanja Kaloper	2014-02-21	Scientific Series	View details
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders	Sunghoon Jung	2014-01-16	Scientific Series	View details
Beyond the Standard Paradigm	Paul Langacker	2014-01-15	Scientific Series	View details
No GUTs, All Glory: Charge Quantization and the Standard Model from Nonlinear Sigma Models	John Kehayias	2013-12-06	Scientific Series	View details
BBN and the Unnatural Weak Scale	David Pinner	2013-12-05	Scientific Series	View details
Using the Higgs as a Direct Probe of New Physics	Michael Park	2013-12-05	Scientific Series	View details
Jets Without Jets	Daniele Bertolini	2013-12-04	Scientific Series	View details
Fully exploring exotic production of the 125 GeV Higgs	Felix Yu	2013-12-03	Scientific Series	View details
Cornering Gluinos at the LHC	Jared Evans	2013-12-02	Scientific Series	View details
Insightful supersymmetry	Erich Poppitz	2013-11-27	Scientific Series	View details
Classical Space Times from S Matrices	Ira Rothstein	2013-11-26	Scientific Series	View details
New Light Species and the CMB - Joint Cosmology/Particle Physics Seminar	Christopher Brust	2013-11-19	Scientific Series	View details

Particle Physics

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