212 research outputs found
Pressure Evolution of Magnetism in URhGa
In this paper, we report the results of an ambient and high pressure study of
a 5f-electron ferromagnet URhGa. The work is focused on measurements of
magnetic and thermodynamic properties of a single crystal sample and on the
construction of the p-T phase diagram. Diamond anvil cells were employed to
measure the magnetization and electrical resistivity pressures up to ~ 9 GPa.
At ambient pressure, URhGa exhibits collinear ferromagnetic ordering of uranium
magnetic moments {\mu}U ~ 1.1 {\mu}B (at 2 K) aligned along the c-axis of the
hexagonal crystal structure below the Curie temperature TC = 41K. With the
application of pressure up to 5GPa the ordering temperature TC initially
increases whereas the saturated moment slightly decreases. The rather
unexpected evolution is put in the context of the UTX family of compounds.Comment: arXiv admin note: text overlap with arXiv:1611.0327
An infinite family of magnetized Morgan-Morgan relativistic thin disks
Applying the Horsk\'y-Mitskievitch conjecture to the empty space solutions of
Morgan and Morgan due to the gravitational field of a finite disk, we have
obtained the corresponding solutions of the Einstein-Maxwell equations. The
resulting expressions are simply written in terms of oblate spheroidal
coordinates and the solutions represent fields due to magnetized static thin
disk of finite extension. Now, although the solutions are not asymptotically
flat, the masses of the disks are finite and the energy-momentum tensor agrees
with the energy conditions. Furthermore, the magnetic field and the circular
velocity show an acceptable physical behavior.Comment: Submitted to IJTP. This paper is a revised and extended version of a
paper that was presented at arXiv:1006.203
Hadron Production in Diffractive Deep-Inelastic Scattering
Characteristics of hadron production in diffractive deep-inelastic
positron-proton scattering are studied using data collected in 1994 by the H1
experiment at HERA. The following distributions are measured in the
centre-of-mass frame of the photon dissociation system: the hadronic energy
flow, the Feynman-x (x_F) variable for charged particles, the squared
transverse momentum of charged particles (p_T^{*2}), and the mean p_T^{*2} as a
function of x_F. These distributions are compared with results in the gamma^* p
centre-of-mass frame from inclusive deep-inelastic scattering in the
fixed-target experiment EMC, and also with the predictions of several Monte
Carlo calculations. The data are consistent with a picture in which the
partonic structure of the diffractive exchange is dominated at low Q^2 by hard
gluons.Comment: 16 pages, 6 figures, submitted to Phys. Lett.
Low Q^2 Jet Production at HERA and Virtual Photon Structure
The transition between photoproduction and deep-inelastic scattering is
investigated in jet production at the HERA ep collider, using data collected by
the H1 experiment. Measurements of the differential inclusive jet
cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the
transverse energy and the pseudorapidity of the jets in the virtual
photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3
< y < 0.6. The interpretation of the results in terms of the structure of the
virtual photon is discussed. The data are best described by QCD calculations
which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
A Purity Monitoring System for the H1 Liquid Argon Calorimeter
The ionization probes used for monitoring the liquid argon purity in the H1
calorimeter are described and results of their operation in tests at CERN and
during the period 1992 to the end of 1998 at HERA are given. The high
sensitivity of the charge measurements leads to refined charge collection
models, and to the observation of a variation of the ionization yield of our
electron sources with temperature.Comment: 26 pages, 14 figure
Unbinned Deep Learning Jet Substructure Measurement in High ep collisions at HERA
The radiation pattern within high energy quark- and gluon-initiated jets (jet
substructure) is used extensively as a precision probe of the strong force as
well as an environment for optimizing event generators with numerous
applications in high energy particle and nuclear physics. Looking at
electron-proton collisions is of particular interest as many of the
complications present at hadron colliders are absent. A detailed study of
modern jet substructure observables, jet angularities, in electron-proton
collisions is presented using data recorded using the H1 detector at HERA. The
measurement is unbinned and multi-dimensional, using machine learning to
correct for detector effects. All of the available reconstructed object
information of the respective jets is interpreted by a graph neural network,
achieving superior precision on a selected set of jet angularities. Training
these networks was enabled by the use of a large number of GPUs in the
Perlmutter supercomputer at Berkeley Lab. The particle jets are reconstructed
in the laboratory frame, using the jet clustering algorithm.
Results are reported at high transverse momentum transfer GeV,
and inelasticity . The analysis is also performed in sub-regions
of , thus probing scale dependencies of the substructure variables. The
data are compared with a variety of predictions and point towards possible
improvements of such models.Comment: 33 pages, 10 figures, 8 table
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