Theory Seminars Archive

Thursday, November 23, 2017

Speaker: Ahmed Ismail

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Signatures of New Anomalous Gauge Bosons

Abstract:  Gauge anomalies occur in nearly all Abelian extensions of the Standard Model without additional chiral fermions. The lack of detection of new particles suggests that if a new gauge boson exists, we can integrate out the heavy anomaly-canceling fermions at high scales to obtain a low-energy effective field theory with a non-conserved current. We review the construction of this theory and discuss its phenomenological applications, with a focus on the Wess-Zumino terms describing the effective low energy anomalies. In particular, we show that the requirement of theoretical consistency in dark matter models can lead to enhanced indirect detection signatures.

Thursday, November 9, 2017

Time: 2:00 PM -- 5:00 PM

 Location: HP4351

 Speaker: Jonathan Feng

 Title: FASER

 Speaker: Tracy Slatyer

 Title: Resummation for WIMPs

 Speaker: Michael Peskin

 Title: Extracting High-Precision Higgs Boson Couplings at the 250 GeV IL


Thursday, October 12, 2017

Speaker: Yongcheng Wu

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Searching for CPV effects in h->\tau\tau at the LHC and future e+e- collider

Abstract: TBD

Thursday, October 5, 2017

Speaker: Simon Caron-Huot

Time: 2:30PM -- 4:30PM

Location: HP4351

Title: When does the gluon reggeize?

Abstract: I will review the phenomenon of gluon reggeization, and how it controls the energy dependence of high energy forward scattering in perturbative QCD, from a modern perspective based on the eikonal approximation. I will present several novel applications, including its interplay with infrared logarithms and with the more standard evolution of parton distribution functions at small momentum fraction, and present recent progress toward determining the evolution to three-loops. Based on 1309.6521 and 1604.07417.


Thursday, September 28, 2017

Speaker: Ariel Edery

Time: 3:30PM -- 4:30PM

Location: HP4351

Title:  Where does the scale originate from in going from pure R^gravity to the equivalent Einstein gravity?

Abstract: Higher-derivative gravity theories have the well-known problem of not being unitary. However, there is one exception: pure R^2 gravity (R^2 gravity alone). Not only is it unitary but it has recently been shown by a few groups that this theory is equivalent to Einstein gravity with a non-zero cosmological constant minimally coupled to a massless scalar field. The original theory is scale-invariant but the equivalent Einstein theory is not. A crucial question is ``where does the scale originate from?" We point out that the conformal transformation that is performed in going from R^2 to Einstein gravity naturally selects a background spacetime with non-zero Ricci scalar R. This vacuum state does not preserve the symmetry of the action and the scale symmetry is spontaneously broken. We identify the massless scalar field as the Nambu-Goldstone boson associated with the broken symmetry.

Thursday, September 14, 2017
Speaker: Miki Gintner

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: The direct and indirect limits for the strong BSM SU(2)_L+R vector resonance phenomenology

Abstract: First, a simple effective model for the early LHC signs ofstrongly-interacting new physics including a new SU(2)_L+R vectorresonance triplet will be introduced. Then, the current limits for the model's free parameters based on the latest LHC measurements will be shown. Besides, the low-energy electroweak precision data restrictionsalong with the unitarity limits on the validity of the model will be discussed.

Thursday, July 27, 2017
Speaker: Jérôme Claude

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Search for a doubly charged Higgs boson through vector boson scattering with the ATLAS detector


Abstract: The hierarchy problem suggests that there must be physics beyond the Standard Model (SM) in the electroweak sector. A deviation from SM-predicted values in the Higgs coupling to vector bosons would allow these new physics in the form of an extension to the Higgs sector. The Georgi-Machacek model introduces scalars in higher isospin multiplets to the SM, including a doubly-charged Higgs, while preserving custodial symmetry. This new scalar is potentially accessible as a resonance through charged vector boson scattering (W+ W+ → W+ W+) in the 30 fb-1 of √s = 13 TeV data collected by the ATLAS detector at the Large Hadron Collider (LHC).

This search focuses on the final state of this resonance which includes a pair of same-sign leptons accompanied by a pair of forward jets and missing transverse momentum (MET). Same-sign leptons in the final state are a rare feature of the standard model, and so the background is dominated by charge misidentification. Techniques to reduce these types of background are presented, and the potential for discovery or exclusion is discussed.

Thursday, July 13, 2017
Speaker: Sebastian Rosado Navarro

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Flavour change study in the Higgs bosons production at the LHeC

Abstract: TBD

Tuesday, July 4, 2017

Speaker: Jim Cline

Time:  11AM

Location: HP4351

Title: B decay anomalies from nonabelian horizontal symmetry


I consider a theory of flavor in which matter transforms under a local SU(3)_L x SU(3)_R flavor symmetry group, acting in the same way on quarks and leptons. It breaks to a U(1) subgroup whose associated Z' gauge boson can explain the observed anomalies in B->K l l decays. To satisfy ATLAS dilepton and perturbativity constraints, the Z' mass should be not far above 5 TeV, hence close to discovery at LHC. New contributions to B-\bar B and K-\bar K mixing are not much below current limits, and possibly also lepton-flavor violating decays mu -> 3e, tau -> 3l and violation of CKM unitarity.

Thursday, April 13, 2017

Speaker: Josh Berger

Time: 3:30PM -- 4:30PM

Location: HP4351

Title: Hydrogen Axion Star: Metallic Hydrogen Bound to a QCD Axion BEC

Abstract: As a cold dark matter candidate, the QCD axion may form Bose-Einstein condensates, called axion stars, with masses around 10−11M⊙. In this paper, we point out that a brand new astrophysical object, a Hydrogen Axion Star (HAS), may well be formed by ordinary baryonic matter becoming gravitationally bound to an axion star. We study the properties of the HAS and find that the hydrogen cloud has a high pressure and temperature in the center and is likely in the liquid metallic hydrogen state. Because of the high particle number densities for both the axion star and the hydrogen cloud, the feeble interaction between axion and hydrogen can still generate enough internal power, around 10^13 W×(ma/5 meV)^4, to make these objects luminous point sources. High resolution ultraviolet, optical and infrared telescopes can discover HAS via black-body radiation.