Search results for "Monopole"
showing 10 items of 76 documents
Vacuum Topology of the Two Higgs Doublet Model
2011
We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of GL(8,C). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emergin…
Emergent Soft Monopole Modes in Weakly-Bound Deformed Nuclei
2014
Based on the Hartree-Fock-Bogoliubov solutions in large deformed coordinate spaces, the finite amplitude method for quasiparticle random phase approximation (FAM-QRPA) has been implemented, providing a suitable approach to probe collective excitations of weakly-bound nuclei embedded in the continuum. The monopole excitation modes in Magnesium isotopes up to the neutron drip line have been studied with the FAM-QRPA framework on both the coordinate-space and harmonic oscillator basis methods. Enhanced soft monopole strengths and collectivity as a result of weak-binding effects have been unambiguously demonstrated.
Color Anomaly and Flavor-Singlet Axial Charge of the Proton in the Chiral Bag: The Cheshire Cat Revisited
1997
Quantum effects inside the chiral bag induce a color anomaly which requires a compensating surface term to prevent breakdown of color gauge invariance. We show that the presence of this surface term first discovered several years ago allows one to derive in a gauge-invariant way a chiral-bag version of the Shore-Veneziano two-component formula for the flavor-singlet axial charge of the proton. This has relevance to what is referred to as the ``proton spin problem" on the one hand and to the Cheshire-Cat phenomenon in hadron structure on the other. We show that when calculated to the leading order in the color gauge coupling and for a specific color electric monopole configuration in the bag…
Schematic and realistic model calculations of the isovector spin monopole excitations in 116In
2012
The excitation of Gamow-Teller (GT) and isovector spin monopole (IVSM) Jπ=1+ modes in 116In by (p,n) and (n,p) charge-exchange reactions on 116Cd and on 116Sn, respectively, is studied within the framework of the quasiparticle random-phase approximation. The calculations have been performed both for schematic and realistic model situations. It appears that the calculated admixture of the IVSM and Gamow-Teller (GT) Jπ=1+ excitations is negligible and that the contribution to the strength above 20 MeV of excitation energy, in 116In, is due to the IVSM (σr2t ±) mode. This result is compared with the recent experimental work that reported a large amount of both (p,n) and (n,p) strength beyond 1…
Low energy collective modes of deformed superfluid nuclei within the finite amplitude method
2013
Background: The major challenge for nuclear theory is to describe and predict global properties and collective modes of atomic nuclei. Of particular interest is the response of the nucleus to a time-dependent external field that impacts the low-energy multipole and beta-decay strength. Purpose: We propose a method to compute low-lying collective modes in deformed nuclei within the finite amplitude method (FAM) based on the quasiparticle random-phase approximation (QRPA). By using the analytic property of the response function, we find the QRPA amplitudes by computing the residua of the FAM amplitudes by means of a contour integration around the QRPA poles in a complex frequency plane. Metho…
Giant Monopole Resonances and nuclear incompressibilities studied for the zero-range and separable pairing interactions
2012
Background: Following the 2007 precise measurements of monopole strengths in tin isotopes, there has been a continuous theoretical effort to obtain a precise description of the experimental results. Up to now, there is no satisfactory explanation of why the tin nuclei appear to be significantly softer than 208Pb. Purpose: We determine the influence of finite-range and separable pairing interactions on monopole strength functions in semi-magic nuclei. Methods: We employ self-consistently the Quasiparticle Random Phase Approximation on top of spherical Hartree-Fock-Bogolyubov solutions. We use the Arnoldi method to solve the linear-response problem with pairing. Results: We found that the dif…
Measurement of magnetic monopole transition in electron scattering fromO16as direct test of dispersive effects
1991
For the first time an experiment has been performed to measure a magnetic monopole transition in inelastic electron scattering. In {sup 16}O the 0{sup +}{r arrow}0{sup {minus}} transition to the level at {ital E}{sub {ital x}}=10.957 MeV has been observed with a cross section of {ital d}{sigma}/{ital d}{Omega}=(5.4{plus minus}3.8){times}10{sup {minus}37} cm{sup {minus}2}/sr. Measurement of this transition is a direct signature of two-step contributions in electron scattering. Our measurement is in good agreement with the strength calculated for this transition.
A Brief Discussion on the Performance of the MoEDAL and the LHCf Experiments
2018
The Monopole and Exotics Detector at the LHC (MoEDAL) experiment is an experiment dedicated to searching for beyond standard model (BSM) particles like magnetic monopoles, highly ionizing particles and slow-moving supersymmetric particles. In many ways, this detector complements the BSM searches of ATLAS and CMS. In this document, a brief description of the MoEDAL detector and performance is given. The Large Hadron Collider Forward (LHCf) experiment, on the other hand, is dedicated to measuring the neutral particles produced in the hadronic collision in the very forward region. This document also briefly discusses the LHCf detector and its performance.
MoEDAL: Seeking magnetic monopoles and more at the LHC
2015
The MoEDAL experiment (Monopole and Exotics Detector at the LHC) is designed to directly search for magnetic monopoles and other highly ionising stable or metastable particles arising in various theoretical scenarios beyond the Standard Model. Its physics goals --largely complementary to the multi-purpose LHC detectors ATLAS and CMS-- are accomplished by the deployment of plastic nuclear track detectors combined with trapping volumes for capturing charged highly ionising particles and TimePix pixel devices for monitoring. This paper focuses on the status of the detectors and the prospects for LHC Run II.
Search for Magnetic Monopoles ins=7 TeVppCollisions with the ATLAS Detector
2012
This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb(-1) of pp collisions recorded at a center-of- ...