Event Category: Particle Seminar

Particle Seminar:
Wednesdays 2:00pm at LBNL

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Abstract: Superradiant instabilities may create clouds of ultralight bosons around black holes, forming so-called “gravitational atoms.” It was recently shown that the presence of a binary companion can induce resonant transitions between a cloud’s bound states. When these transitions backreact on the binary’s orbit, they lead to qualitatively distinct signatures in the gravitational waveform that can dominate the overall behavior … Read More

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Gravitational waves with frequencies below 1 nHz are notoriously difficult to detect. With periods exceeding current experimental lifetimes, they induce slow drifts in observables rather than periodic correlations. In this talk, I will demonstrate that pulsar timing parameters can discover such ”ultralow” frequency gravitational waves. I will present two complementary observables for which the systematic shift induced by gravitational waves … Read More

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One central property of the S-matrix is its invariance under field redefinitions. I will discuss how the geometry of field space makes this invariance manifest. This geometric formulation also has practical consequences. The scattering amplitudes satisfy a geometric soft theorem.  Also, scattering amplitudes and the renormalization group equations for a theory of scalars and gauge bosons only depend on geometric quantities. … Read More

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The Standard Model Higgs becomes tachyonic at high energy scales according to current measurements. This unstable regime of the Higgs potential can be realized in the early Universe during high scale inflation, potentially with catastrophic consequences. In this talk, we will discuss a crucial inherent feature of such configurations that has so far remained ignored: Higgs particle production out of … Read More

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Abstract: In this talk, I will discuss about my recent work about the on-shell understanding of the spontaneously broken gauge theories by employing the on-shell massive spinor formalism and tree unitarity. We start from the most general on-shell three-particle amplitudes with energy growing behavior at most of O(E) involving arbitrary, finite number of massive scalars, spinors and vectors. Then the … Read More

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In this talk, we will explore the possibility that dark matter is a pair of SU(2)_L doublets and consider a novel mechanism of dark matter production that proceeds through the confinement of the weak sector of the Standard Model. This phase of confinement causes the Standard Model doublets and dark matter to confine into pion-like objects. Before the weak sector … Read More

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Abstract:  Dark photons are excellent dark matter candidates and offer compelling experimental targets. However, recently it has been shown that the simplest production scenarios (e.g. inflationary production and axion-dark photon conversion) lead to the formation of topological defects rather than nonrelativistic dark matter, substantially restricting the viable parameter space. I will first explain how defect formation constrains dark photon production … Read More

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Despite the exceptional appeal of the Peccei-Quinn mechanism as a solution to the strong CP problem, alternative mechanisms should still be pursued. In this direction, I will present in the first part of my talk how a Nelson-Barr mechanism (NB) arises automatically in the context of gauged flavor models. Given the tight connection of the strong CP problem with flavor, … Read More