QUANTUM REFLECTION OF MASSLESS NEUTRINOS FROM A TORSION-INDUCED POTENTIAL

In the context of the Einstein–Cartan–Dirac model, where the torsion of the space–time couples to the axial currents of the fermions, we study the effects of this quantum-gravitational interaction on a massless neutrino beam crossing through a medium with a high number density of fermions at rest. We calculate the reflection amplitude and show that a specific fraction of the incident neutrinos reflects from this potential if the polarization of the medium is different from zero. We also discuss the order of magnitude of the fermionic number density in which this phenomenon is observable, in other theoretical contexts, for example, the strong gravity regime and the effective field theory approach.

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Spin effects in the effective field theory approach to Post-Minkowskian conservative dynamics

Journal of High Energy Physics ◽

10.1007/jhep06(2021)012 ◽

2021 ◽

Vol 2021 (6) ◽

Author(s):

Zhengwen Liu ◽

Rafael A. Porto ◽

Zixin Yang

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Scattering Problem ◽

Finite Size ◽

Effective Field ◽

Compact Objects ◽

Scattering Data ◽

Theory Approach ◽

Spin Effects ◽

Radial Action

Abstract Building upon the worldline effective field theory (EFT) formalism for spinning bodies developed for the Post-Newtonian regime, we generalize the EFT approach to Post-Minkowskian (PM) dynamics to include rotational degrees of freedom in a manifestly covariant framework. We introduce a systematic procedure to compute the total change in momentum and spin in the gravitational scattering of compact objects. For the special case of spins aligned with the orbital angular momentum, we show how to construct the radial action for elliptic-like orbits using the Boundary-to-Bound correspondence. As a paradigmatic example, we solve the scattering problem to next-to-leading PM order with linear and bilinear spin effects and arbitrary initial conditions, incorporating for the first time finite-size corrections. We obtain the aligned-spin radial action from the resulting scattering data, and derive the periastron advance and binding energy for circular orbits. We also provide the (square of the) center-of-mass momentum to $$ \mathcal{O}\left({G}^2\right) $$ O G 2 , which may be used to reconstruct a Hamiltonian. Our results are in perfect agreement with the existent literature, while at the same time extend the knowledge of the PM dynamics of compact binaries at quadratic order in spins.

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Precision Higgs couplings in neutral naturalness models: an effective field theory approach

Journal of High Energy Physics ◽

10.1007/jhep02(2021)234 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

Lucien Heurtier ◽

Hao-Lin Li ◽

Huayang Song ◽

Shufang Su ◽

Wei Su ◽

...

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Goldstone Boson ◽

Higgs Sector ◽

New Physics ◽

Effective Field ◽

Precision Measurements ◽

Global Symmetry ◽

Theory Approach ◽

Decay Channels

AbstractThe Higgs sector in neutral naturalness models provides a portal to the hidden sectors, and thus measurements of Higgs couplings at current and future colliders play a central role in constraining the parameter space of the model. We investigate a class of neutral naturalness models, in which the Higgs boson is a pseudo-Goldstone boson from the universal SO(N)/SO(N −1) coset structure. Integrating out the radial mode from the spontaneous global symmetry breaking, we obtain various dimension-six operators in the Standard Model effective field theory, and calculate the low energy Higgs effective potential with radiative corrections included. We perform aχ2fit to the Higgs coupling precision measurements at current and future colliders and show that the new physics scale could be explored up to 2.3 (2.4) TeV without (with) the Higgs invisible decay channels at future Higgs factories. The limits are comparable to the indirect constraints obtained via electroweak precision measurements.

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Searching for charged lepton flavor violation at ep colliders

Journal of High Energy Physics ◽

10.1007/jhep03(2021)230 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

Stefan Antusch ◽

A. Hammad ◽

Ahmed Rashed

Keyword(s):

Standard Model ◽

Charged Lepton ◽

Neutral Current ◽

Effective Theory ◽

Theory Approach ◽

Lepton Flavor Violation ◽

Lepton Flavor ◽

Flavor Violation ◽

The Standard Model ◽

Order Of Magnitude

Abstract We investigate the sensitivity of electron-proton (ep) colliders for charged lepton flavor violation (cLFV) in an effective theory approach, considering a general effective Lagrangian for the conversion of an electron into a muon or a tau via the effective coupling to a neutral gauge boson or a neutral scalar field. For the photon, the Z boson and the Higgs particle of the Standard Model, we present the sensitivities of the LHeC for the coefficients of the effective operators, calculated from an analysis at the reconstructed level. As an example model where such flavor changing neutral current (FCNC) operators are generated at loop level, we consider the extension of the Standard Model by sterile neutrinos. We show that the LHeC could already probe the LFV conversion of an electron into a muon beyond the current experimental bounds, and could reach more than an order of magnitude higher sensitivity than the present limits for LFV conversion of an electron into a tau. We discuss that the high sensitivities are possible because the converted charged lepton is dominantly emitted in the backward direction, enabling an efficient separation of the signal from the background.

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MEDIATION OF SUPERSYMMETRY BREAKING IN EXTRA DIMENSIONS

Modern Physics Letters A ◽

10.1142/s0217732305016750 ◽

2005 ◽

Vol 20 (05) ◽

pp. 297-312 ◽

Cited By ~ 10

Author(s):

CLAUDIO A. SCRUCCA

Keyword(s):

Supersymmetry Breaking ◽

Effective Field Theory ◽

Extra Dimensions ◽

Model Building ◽

Realistic Model ◽

Effective Field ◽

Theory Approach ◽

Classical Level ◽

Gravitational Effects ◽

Gravitational Fields

We review the mechanisms of supersymmetry breaking mediation that occur in sequestered models, where the visible and the hidden sectors are separated by an extra dimension and communicate only via gravitational interactions. By locality, soft breaking terms are forbidden at the classical level and reliably computable within an effective field theory approach at the quantum level. We present a self-contained discussion of these radiative gravitational effects and the resulting pattern of soft masses, and give an overview of realistic model building based on this setup. We consider both flat and warped extra dimensions, as well as the possibility that there be localized kinetic terms for the gravitational fields.

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Hot and cold running water: understanding evolved star winds

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317010602 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 347-350

Author(s):

A. M. S. Richards ◽

M. D. Gray ◽

A. Baudry ◽

E. M. L. Humphreys ◽

S. Etoka ◽

...

Keyword(s):

Mass Loss ◽

Circumstellar Envelope ◽

Number Density ◽

Running Water ◽

Physical Conditions ◽

Evolved Stars ◽

Order Of Magnitude ◽

Homogeneous Regions ◽

Maser Sources

AbstractOutstanding problems concerning mass-loss from evolved stars include initial wind acceleration and what determines the clumping scale. Reconstructing physical conditions from maser data has been highly uncertain due to the exponential amplification. ALMA and e-MERLIN now provide image cubes for five H2O maser transitions around VY CMa, at spatial resolutions comparable to the size of individual clouds or better, covering excitation states from 204 to 2360 K. We use the model of Gray et al. 2016, to constrain variations of number density and temperature on scales of a few au, an order of magnitude finer than is possible with thermal lines, comparable to individual cloud sizes or locally almost homogeneous regions. We compare results with the models of Decin et al. 2006 and Matsuura et al. 2014 for the circumstellar envelope of VY CMa; in later work this will be extended to other maser sources.

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