234 research outputs found
Lineshape of the Higgs boson in future lepton colliders
The effect of the photon emission (bremsstrahlung) in the cross section of
the process of direct production of the Higgs boson in the future high
luminosity electron and muon colliders is calculated. It was found that cross
section at the top of the Higgs boson resonance peak is reduced by factor 0.347
for the electron collider and 0.548 for the muon collider. Machine spread of
the centre of the mass energy of 4.2MeV (equal to the Higgs width) would reduce
peak cross section further, by factor 0.170 and 0.256 (QED and energy spread)
for electron and muon beams respectively. Possible uncertainties in the
resummed QED calculations are discussed. Numerical results for the lineshape
cross section including QED and many values of the machine energy spread are
provided.Comment: 18 pages, 7 figures; added new reference
Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements
We have measured the low-temperature specific heat of the geometrically
frustrated pyrochlore Heisenberg antiferromagnet Gd2Sn2O7 in zero magnetic
field. The specific heat is found to drop exponentially below approximately 350
mK. This provides evidence for a gapped spin-wave spectrum due to an anisotropy
resulting from single ion effects and long-range dipolar interactions. The data
are well fitted by linear spin-wave theory, ruling out unconventional low
energy magnetic excitations in this system, and allowing a determination of the
pertinent exchange interactions in this material
Juxtaposition of Spin Freezing and Long Range Order in a Series of Geometrically Frustrated Antiferromagnetic Gadolinium Garnets
Specific heat measurements in zero magnetic field are presented on a
homologous series of geometrically frustrated, antiferromagnetic, Heisenberg
garnet systems. Measurements of Gd3Ga5O12, grown with isotopically pure Gd,
agree well with previous results on samples with naturally abundant Gd, showing
no ordering features. In contrast, samples of Gd3Te2Li3O12 and Gd3Al5O12 are
found to exhibit clear ordering transitions at 243 mK and 175 mK respectively.
The effects of low level disorder are studied through dilution of Gd3+ with
non-magnetic Y3+ in Gd3Te2Li3O12. A thorough structural characterization, using
X-ray diffraction, is performed on all of the samples studied. We discuss
possible explanations for such diverse behavior in very similar systems.Comment: Accepted for publication in Physical Review
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