Joint Theory Seminar
Speaker: Yue Zhao (Stanford/SLAC)
Title: A Complete Model of Low-Scale Gauge Mediation
Host: Hsin-Chia Cheng
Room: 432
Abstract: 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 couplings that generate large A-terms at the messenger scale and viable mu/Bmu-terms.
Our models are simple, economical, and complete realizations of supersymmetry at the weak scale.
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High-Energy Seminars
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9:00am - 10:00am
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HE Seminar
Speaker: Jason Gallicchio
Title: Quark/Gluon Tagger in Theory and Data
Host: Chertok
Room: 416
Abstract:
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 light-quark jets. I will discuss applications, address theoretical issues in the definitions of quark and gluon jets, and show progress that ATLAS has made in measuring these observables.
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High-Energy Seminars
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6:30am - 7:30am
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Joint Theory Seminar
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Room: 432
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HE Seminar
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Host:
Room: 285
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High-Energy Seminars
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6:30am - 7:30am
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Joint Theory Seminar
Speaker: Yuhsin Tsai (UC Davis)
Title: Baryogenesis and Superparter Oscillations in R-symmetric SUSY
Host: Yuhsin Tsai
Room: 432
Abstract: Weak scale SUSY with R-symmetry is a plausible solution to the SUSY flavor problem. In this talk, we discuss 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. R-symmetric models can also give spectacular signals at the LHC. If a tiny Majorana mass splits the degenerate mass eigenstates of gauginos and higgsinos, states produced at the LHC can oscillate between the spraticles and their Dirac mass partners. With displaced decays, the oscillation can be visible in the distribution of displaced vertex lengths at the LHC.
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High-Energy Seminars
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9:00am - 10:00am
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HE Seminar
Speaker: Guido D'Amico (NYU)
Title: Unwinding Inflation
Host: Nemanja
Room: 416
Abstract: When electric-type flux winds around compact extra dimensions, a single quantum event can break a flux line and initiate a classical cascade that unwinds many units of flux. From the 4D point of view, this is the formation of a thin-wall bubble containing an open FRW cosmology, but---unlike Coleman-de Luccia bubble formation---the vacuum energy inside the bubble is initially only slightly reduced, and then decreases steadily throughout the cascade. If the initial number of flux quanta $Q \simgeq 100$, this can result in $N \simgeq 60$ efolds of inflationary expansion while producing a scale-invariant spectrum of adiabatic density perturbations, with amplitude and tilt consistent with observation. The power spectrum has a small oscillatory component that does not decay away during inflation, with a period set approximately by the light-crossing time of the compact dimension. Since the ingredients are fluxes wrapping compact dimensions, wound inflation fits naturally into the string landscape, but does not appear to suffer from the eta problem or require fine-tuning (beyond the usual anthropic requirement of small vacuum energy after reheating).
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High-Energy Seminars
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5:10am - 6:10am
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LHC Lunch
Speaker:
Title:
Host: Markus Luty
Room: 430
Abstract:
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High-Energy Seminars
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6:30am - 7:30am
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Joint Theory Seminar
Speaker: Flip Tanedo (LEPP Cornell University)
Title: Goldstone Fermion Dark Matter
Host: Yuhsin Tsai
Room: 432
Abstract: 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.
Typical WIMP candidates in the MSSM require a tuned spectrum to simultaneously obtain the observed dark matter relic abundance and avoid the upper limit on the WIMP nucleon cross section from direct detection experiments. Goldstone fermions can avoid this tuning since their annihilation rate is naturally fixed by interactions within the nonlinearly realized sector while the direct detection cross section is controlled by mixing with the Higgs sector. For a global U(1) broken at the TeV scale, one naturally obtains a 100 GeV scale Higgs-portal WIMP candidate whose direct detection rate is suppressed by three orders of magnitude.
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9:00am - 10:00am
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HE Seminar
Speaker: Tuhin Roy
Title: Qjets: A Non-deterministic Approach to Tree-based Jet Substructure
Host: Markus Luty
Room: 416
Abstract: 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, we propose 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, such as the variance of the distribution, provide new handles for signal and background discrimination. For example, we find that employing a set of trees substantially reduces the observed fluctuations in the pruned mass distribution, enhancing the likelihood of new particle discovery for a given integrated luminosity. Furthermore, we introduce a new quantity `volatility', a cut on which reduces the luminosity needed for a given significance requirement by a factor of two.
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High-Energy Seminars
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5:10am - 6:10am
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LHC Lunch
Speaker: Tia Miceli
Title: Dark matter, extra dimensions, and Z decays at CMS
Host: Markus Luty
Room: 430
Abstract: CMS has collected 5-fb of proton-proton collision data during the 2011 LHC running at 7 TeV. Presented is the analysis of collisions in which a single photon recoils from invisible particles. The results are consistent with the predicted cross section of Z bosons decaying to neutrino pairs. Subsequently, competitive limits are placed on ADD large extra dimensions, and a model of dark matter.
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High-Energy Seminars
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6:30am - 7:30am
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Description:
Joint Theory Seminar
Speaker: Ian Low (Northwestern U and Argonne Lab)
Title: Higgs Identification
Host: Hsin-Chia Cheng
Room: 432
Abstract: 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. I will discuss preliminary efforts in this direction and explore implications of current measurements on future searches at the LHC and beyond.
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High-Energy Seminars
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9:00am - 10:00am
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HE Seminar
Speaker: Mike Hance (LBNL)
Title: Searching for New Physics in Multilepton Events with the ATLAS Experiment
Host:
Room: 416
Abstract: 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). I'll describe some recent analyses from ATLAS based on multilepton signatures. In particular, I'll focus on new model-independent limits for anomalous production of multilepton events that can be used to test a variety of BSM scenarios.
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High-Energy Seminars
Time:
5:10am - 6:10am
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Description:
LHC Lunch
Speaker:
Title:
Host: Markus Luty
Room: 430
Abstract:
6:30am» Joint Theory Seminar - Yue Zhao