2,069 research outputs found
Search for the Top Partner at the LHC using Multi-b-Jet Channels
Vector-like quarks are introduced in various new physics models beyond the
standard model (SM) at the TeV scale. We especially consider the case that the
quark is singlet (triplet) under the SU(2) (SU(3)) gauge group and
couples only to the third generation quarks of the SM. The vector-like quark of
this kind is often called a top partner. The top partoner decays into
and . In the ATLAS and CMS collaborations, the top partner has
been searched in the final states of and , while the search based on
the decay mode has not been started yet. However, the decay into
is important since it is significantly enhanced if some strong dynamics
exists in the TeV scale. In the presence of a light higgs boson, the decay mode
followed by produces three bottom quarks. We study
the sensitivity for the top partner using multi-b-jet events at the 8 TeV run
of the LHC experiment. The multi-b-jet eventss turn out to play a complementary
role to the existing and searches by the ATLAS and CMS
collaborations.Comment: 26 pages, 9 figures, 10 Table
Subspace Variational Quantum Simulator
Quantum simulation is one of the key applications of quantum computing, which
can accelerate research and development in chemistry, material science, etc.
Here, we propose an efficient method to simulate the time evolution driven by a
static Hamiltonian, named subspace variational quantum simulator (SVQS). SVQS
employs the subspace-search variational eigensolver (SSVQE) to find a
low-energy subspace and further extends it to simulate dynamics within the
low-energy subspace. More precisely, using a parameterized quantum circuit, the
low-energy subspace of interest is encoded into a computational subspace
spanned by a set of computational basis, where information processing can be
easily done. After the information processing, the computational subspace is
decoded to the original low-energy subspace. This allows us to simulate the
dynamics of low-energy subspace with lower overhead compared to existing
schemes. While the dimension is restricted for feasibility on near-term quantum
devices, the idea is similar to quantum phase estimation and its applications
such as quantum linear system solver and quantum metropolis sampling. Because
of this simplicity, we can successfully demonstrate the proposed method on the
actual quantum device using Regetti Quantum Cloud Service. Furthermore, we
propose a variational initial state preparation for SVQS, where the initial
states are searched from the simulatable eigensubspace. Finally, we demonstrate
SVQS on Rigetti Quantum Cloud Service
Muon g-2 and LHC phenomenology in the gauge symmetric model
In this paper, we consider phenomenology of a model with an
gauge symmetry. Since the muon couples to the gauge boson
(called boson), its contribution to the muon anomalous magnetic moment
(muon g-2) can account for the discrepancy between the standard model
prediction and the experimental measurements. On the other hand, the
boson does not interact with the electron and quarks, and hence there are no
strong constraints from collider experiments even if the boson mass is of
the order of the electroweak scale. We show an allowed region of a parameter
space in the symmetric model, taking into account consistency
with the electroweak precision measurements as well as the muon g-2. We study
the Large Hadron Collider (LHC) phenomenology, and show that the current and
future data would probe the interesting parameter space for this model.Comment: 26 pages, 12 figure
Monopole-vortex complex in a theta vacuum
We discuss aspects of the monopole-vortex complex soliton arising in a
hierarchically broken gauge system, G to H to 1, in a theta vacuum of the
underlying G theory. Here we focus our attention mainly on the simplest such
system with G=SU(2) and H=U(1). A consistent picture of the effect of the theta
parameter is found both in a macroscopic, dual picture and in a microscopic
description of the monopole-vortex complex soliton.Comment: 18 pages 3 figure
Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCoO
Ultrasound velocity measurements of the orbitally-frustrated GeCoO
reveal unusual elastic instabilities due to the phonon-spin coupling within the
antiferromagnetic phase. Shear moduli exhibit anomalies arising from the
coupling to short-range ferromagnetic excitations. Diplike anomalies in the
magnetic-field dependence of elastic moduli reveal magnetic-field-induced
orbital order-order transitions. These results strongly suggest the presence of
geometrical orbital frustration which causes novel orbital phenomena within the
antiferromagnetic phase.Comment: 5 pages, 3 figure
Magnetic-Field-Induced 4f-Octupole in CeB6 Probed by Resonant X-ray Diffraction
CeB6, a typical Gamma_8-quartet system, exhibits a mysterious
antiferroquadrupolar ordered phase in magnetic fields, which is considered as
originating from the T_{xyz}-type magnetic octupole moment induced by the
field. By resonant x-ray diffraction in magnetic fields, we have verified that
the T_{xyz}-type octupole is indeed induced in the 4f-orbital of Ce with a
propagation vector (1/2, 1/2, 1/2), thereby supporting the theory. We observed
an asymmetric field dependence of the intensity for an electric quadrupole (E2)
resonance when the field was reversed, and extracted a field dependence of the
octupole by utilizing the interference with an electric dipole (E1) resonance.
The result is in good agreement with that of the NMR-line splitting, which
reflects the transferred hyperfine field at the Boron nucleus from the
anisotropic spin distribution of Ce with an O_{xy}-type quadrupole. The
field-reversal method used in the present study opens up the possibility of
being widely applied to other multipole ordering systems such as NpO2,
Ce_{x}La_{1-x}B_{6}, SmRu_{4}P_{12}, and so on.Comment: 5 pages, 4 figures, submitte
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