Events with three or more prompt leptons are rare at hadron colliders. At the LHC, where high interaction energies and rates create extremely busy final states, such multilepton events are well suited as a probe for new physics beyond the Standard Model (BSM). Mike Hance describes some recent analyses from ATLAS based on multilepton signatures. In particular, focusing on new model-independent limits for anomalous production of multilepton events that can be used to test a variety of BSM...
Published 10/30/12
The July 4th announcement of the discovery of a Higgs-like particle at CERN LHC is only the beginning of a challenging program of "Higgs Identification" to establish the quantum numbers and couplings of the new particle, and to reveal its relationship, if any, to electroweak symmetry-breaking and fermion mass generation. Ian Low discusses preliminary efforts in this direction and explore implications of current measurements on future searches at the LHC and beyond.
Published 10/29/12
Jet substructure is typically studied using clustering algorithms, such as kT, which arrange the jets' constituents into trees. Instead of considering a single tree per jet, Tuhin Roy proposes that multiple trees should be considered, weighted by an appropriate metric. Then each jet in each event produces a distribution for an observable, rather than a single value. Advantages of this approach include: 1) observables have significantly increased statistical stability; and, 2) new observables,...
Published 10/23/12
Nonlinear realizations describe the low-energy degrees of freedom of strongly coupled theories with spontaneously broken symmetry. When combined with SUSY, the Goldstone bosons of these theories are complex fields with "Goldstone fermion" super-partners. These, in turn, offer novel weakly interacting massive particle (WIMP) dark matter candidates. Flip Tanedo discusses how these can be used in realistic models of dark matter.
Published 10/22/12
Guido D'Amico describes a new model of inflation using branes unwrapping from extra dimensions.
Published 10/16/12
Weak scale SUSY with R-symmetry is a plausible solution to the SUSY flavor problem. In this talk, Yuhsin Tsai discusses two interesting aspects of R-symmetric SUSY models: electroweak baryogenesis and superpartner oscillations. Regarding baryogenesis, the new superpotential couplings between the adjoints and the Higgs can increase the strength of the electroweak phase transition, and large CP-violating phases consistent with electric dipole moments can generate large baryon asymmetry....
Published 10/15/12
Jason Gallicchio explains how distinguishing light-quark jets from gluon jets on an event-by-event basis could significantly enhance the reach for many new physics searches at the Large Hadron Collider. Through an exhaustive search of existing and novel jet substructure observables, we find that a combination of two simple variables, the charge track multiplicity and the p_T-weighted linear radial moment (width), can filter out over 85-95% of the gluon jets while keeping more than half of the...
Published 10/02/12
Recent signs of a Standard Model-like Higgs at 125 GeV point towards large A-terms in the MSSM. This presents special challenges for gauge mediation, which by itself predicts vanishing A-terms at the messenger scale. In this paper, we review the general problems that arise when extending gauge mediation to achieve large A-terms, and the mechanisms that exist to overcome them. Using these mechanisms, we construct weakly-coupled models of low-scale gauge mediation with extended Higgs-messenger...
Published 10/01/12
The W boson mass is a crucial parameter in the standard model of particle physics, providing constraints on the mass of the Higgs boson as well as on new physics models via quantum loop corrections. Bo Jayatilaka describes the measurement of the W boson mass using data corresponding to 2.2/fb of integrated luminosity collected with the CDF II detector. The measurement, performed using electron and muon decays of W bosons, yields a mass of 80387±19 MeV. This represents the single most precise...
Published 06/04/12
Both the ATLAS and CMS detectors have operated with high efficiency in the first two years of LHC operation and produced an impressive number of physics results. In this talk I will discuss some of the differences between the detectors and describe some unique features of the ATLAS detector and how these features have been exploited in our physics analyses. I will describe some selected recent results and conclude with an overview of the planned, near term ATLAS detector upgrades.
Published 05/22/12
The bulk matter Randall-Sundrum (RS) model is a setup where Standard Model (SM) matter and gauge fields reside in the bulk of 5D warped spacetime while the Higgs field is confined on the IR brane. The wavefunctions of the 1st and 2nd generation matter particles are localized towards the UV brane and those of the 3rd generation towards the IR brane, so that the hierarchical structure of the Yukawa couplings arises geometrically without hierarchy in fundamental parameters. This paper discusses...
Published 05/21/12
I look for a golden region in the parameter space of the NMSSM with a low cut-off where a SM-like Higgs with a mass m_h ~ 125 GeV can be obtained in a minimal bottom-up approach of field content.
Published 05/14/12
The experimental signature of two leptons with the same electric charge is a great way to search for new physics as the backgrounds from Standard Model processes are quite low and a large variety of new physics models can produce this signature, e.g models with extended Higgs sectors, Supersymmetry, additional quark generations, and many more. Beate Heinemann reviews the ATLAS analyses in this signature based on the 2011 LHC data.
Published 05/08/12
It is widely believed that the emergent magnetic gauge symmetry of SQCD is analogous to a hidden local symmetry (HLS). James Barnard explores this idea in detail, deriving the entire (spontaneously broken) magnetic theory by applying the HLS formalism to spontaneously broken SU(N) SQCD. We deduce the Kahler potential in the HLS description, and show that gauge and flavour symmetry are smoothly restored along certain scaling directions in moduli space. We propose that it is these symmetry...
Published 05/07/12
Harald Fritzsch discusses a model of composite weak bosons.
Published 05/01/12
Jamison Galloway reviews recent Higgs data from the LHC and discuss ways in which model-independent conclusions can be drawn. The bottom-up thinking that goes into this can help to determine what other new physics we might anticipate finding at accessible scales, while allowing us to assess emerging proposals for the origins of the hinted Higgs-like state at 125 GeV. Using composite Higgs and the MSSM as two case studies, Galloway discusses the benefits of constructing these generalized...
Published 04/30/12
Bernard Sadoulet discusses the future of dark matter searches.
Published 04/13/12
Tim Tait examines uncertainties in dark matter production at particle colliders.
Published 04/13/12
Ian Shoemaker discusses other missing energy signatures at particles colliders.
Published 04/13/12
Louie Strigari reviews astrophysical constraints on dark matter.
Published 04/13/12
Dave Mason gives a summary of the dark matter workshop at Fermilab.
Published 04/12/12
Spencer Klein reviews results from the IceCube experiment.
Published 04/12/12
Maxim Pospelov reviews how single effective operator approximation can break down.
Published 04/12/12
Yu-Hsin Tsai reviews dark matter to Higgs coupling constraints from LEP.
Published 04/12/12
Roni Harnik reviews the theory of dark matter detection at the LHC.
Published 04/12/12