700,282 research outputs found
Constraints on large-extra-dimensions model through 125 GeV Higgs pair production at the LHC
Based on the analysis of 5 fb^-1 of data at the LHC, the ATLAS and CMS
collaborations have presented evidence for a Higgs boson with a mass in the 125
GeV range. We consider the 125 GeV neutral Higgs pair production process in the
context of large-extra-dimensions (LED) model including the Kaluza-Klein
(KK)excited gravitons at the LHC. We consider the standard model(SM) Higgs pair
production in gluon-gluon fusion channel and pure LED effects through graviton
exchange as well as their interferences. It is shown that such interferences
should be included; the LED model raises the transverse momentum (Pt)and
invariant mass (M_HH) distributions at high scales of Pt and M_HH of the Higgs
pair production. By using the Higgs pair production we could set the discovery
limit on the cutoff scale M_S up to 6 TeV for delta = 2 and 4.5 TeV for delta =
6.Comment: 6 figure
A Density Spike on Astrophysical Scales from an N-Field Waterfall Transition
Hybrid inflation models are especially interesting as they lead to a spike in
the density power spectrum on small scales, compared to the CMB, while also
satisfying current bounds on tensor modes. Here we study hybrid inflation with
waterfall fields sharing a global symmetry. The inclusion of many
waterfall fields has the obvious advantage of avoiding topologically stable
defects for . We find that it also has another advantage: it is easier to
engineer models that can simultaneously (i) be compatible with constraints on
the primordial spectral index, which tends to otherwise disfavor hybrid models,
and (ii) produce a spike on astrophysically large length scales. The latter may
have significant consequences, possibly seeding the formation of
astrophysically large black holes. We calculate correlation functions of the
time-delay, a measure of density perturbations, produced by the waterfall
fields, as a convergent power series in both and the field's correlation
function . We show that for large , the two-point function is
and the
three-point function is .
In accordance with the central limit theorem, the density perturbations on the
scale of the spike are Gaussian for large and non-Gaussian for small .Comment: 15 pages in double column format, 6 figures. V2: Further
clarifications, updated to coincide with version published in Physics Letters
Indication for Large Rescatterings in Charmless Rare B Decays
The current wealth of charmless B decay data may suggest the presence of
final state rescattering. In a factorized amplitude approach, better fits are
found by incorporating two SU(3) rescattering phase differences, giving delta ~
65 degree and sigma ~ 90 - 100 degree. Fitting with unitarity phase phi_3 as a
fit parameter gives phi_3 ~ 96 degree, the CP asymmetries A_{pi pi}, S_{pi pi}
agree better with BaBar, and the sigma phase is slightly lower. Keeping phi_3 =
60 degree fixed in fit gives S_{pi pi} ~-0.9, which agrees better with Belle.
With the sizable delta, sigma rescattering phases as fitted, many direct CP
asymmetries flip sign, and B0 --> pi0 pi0, K- K+ rates are of order 10^{-6},
which can be tested soon.Comment: 6 pages, 4 figures, updated, references adde
The Crystallography of Strange Quark Matter
Cold three-flavor quark matter at large (but not asymptotically large)
densities may exist as a crystalline color superconductor. We explore this
possibility by calculating the gap parameter Delta and free energy Omega(Delta)
for possible crystal structures within a Ginzburg-Landau approximation,
evaluating Omega(Delta) to order Delta^6. We develop a qualitative
understanding of what makes a crystal structure stable, and find two structures
with particularly large values of Delta and the condensation energy, within a
factor of two of those for the CFL phase known to characterize QCD at
asymptotically large densities. The robustness of these phases results in their
being favored over wide ranges of density and though it also implies that the
Ginzburg-Landau approximation is not quantitatively reliable, previous work
suggests that it can be trusted for qualitative comparisons between crystal
structures. We close with a look ahead at the calculations that remain to be
done in order to make contact with observed pulsar glitches and neutron star
cooling.Comment: 6 pages, 3 figures. Contribution to the proceedings of Strangeness in
Quark Matter 2006, UCLA. Talk given by Rishi Sharm
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