A
bstract
The IceCube detector has recently reported the observation of 28 events at previously unexplored energies. While the statistics of the observed events are still low, these events hint at ...the existence of a neutrino flux over and above the atmospheric neutrino background. We investigate the possibility that a significant component of the additional neutrino flux originates due to the decay of a very heavy dark matter (VHDM) particle via several possible channels into standard model particles. We show that a combination of a power law astrophysical neutrino spectrum and the neutrino flux from the decay of a DM species of mass in the range 150 − 400 TeV improves the fit to the observed neutrino events than that obtained from a best-fit astrophysical flux alone. Assuming the existence of an astrophysical background described by the IC best-fit, we also show that, for the decay of even heavier DM particles (
m
DM
~ 1 PeV), the same observations impose significant constraints on the decay lifetimes. Allowing the astrophysical flux normalization to vary leads to modifications of these limits, however, there is still a range of dark matter mass and lifetime that is excluded by the IC results.
A
bstract
We re-evaluate the prompt atmospheric neutrino flux, using the measured charm cross sections at RHIC and the Large Hadron Collider to constrain perturbative QCD parameters such as the ...factorization and renormalization scales, as well as modern parton distribution functions and recent estimates of the cosmic-ray spectra. We find that our result for the prompt neutrino flux is lower than previous perturbative QCD estimates and, consequently, alters the signal-to-background statistics of the recent IceCube measurements at high energies.
A
bstract
We evaluate the prompt atmospheric neutrino flux at high energies using three different frameworks for calculating the heavy quark production cross section in QCD: NLO perturbative QCD,
k
T
...factorization including low-
x
resummation, and the dipole model including parton saturation. We use QCD parameters, the value for the charm quark mass and the range for the factorization and renormalization scales that provide the best description of the total charm cross section measured at fixed target experiments, at RHIC and at LHC. Using these parameters we calculate differential cross sections for charm and bottom production and compare with the latest data on forward charm meson production from LHCb at 7 TeV and at 13 TeV, finding good agreement with the data. In addition, we investigate the role of nuclear shadowing by including nuclear parton distribution functions (PDF) for the target air nucleus using two different nuclear PDF schemes. Depending on the scheme used, we find the reduction of the flux due to nuclear effects varies from 10% to 50% at the highest energies. Finally, we compare our results with the IceCube limit on the prompt neutrino flux, which is already providing valuable information about some of the QCD models.
Newborn, strongly magnetized neutron stars (so-called magnetars) surrounded by their stellar or merger ejecta are expected to be sources of ultrahigh-energy neutrinos via decay of mesons produced in ...hadronic interactions of protons which are accelerated to ultrahigh energies by magnetic dissipation of the spindown energy. We show that not only pions and kaons but also charm hadrons, which are typically neglected due to their small production cross sections, can represent dominant contributions to neutrino fluence at ultrahigh energies, because of their short lifetimes, while the ultrahigh-energy neutrino fluence from pion and kaon production is suppressed at early times due to their significant cooling before their decay. We show that the next-generation detectors such as Probe Of Extreme Multi-Messenger Astrophysics (POEMMA), Giant Radio Array for Neutrino Detection (GRAND) and IceCube-Gen2 have a good chance of observing neutrinos, primarily originating from charm hadrons, from nearby magnetars. We also show that neutrinos from nearby magnetar-driven merger novae could be observed in the time interval between 102 s and 103 s, where the charm hadron contribution is dominant for neutrino energies above 108 GeV, of relevance to next generation detectors. We also comment on potential impacts of the charm hadron contribution to the diffuse neutrino flux.
The AdS/CFT correspondence in principle gives a new approach to deep inelastic scattering as formulated by Polchinski and Strassler. Subsequently Brower, Polchinski, Strassler and Tan (BPST) computed ...the strong coupling kernel for the vacuum (or Pomeron) contribution to total cross sections. By identifying deep inelastic scattering with virtual photon total cross section, this allows a self consistent description at small-
x
where the dominant contribution is the vacuum exchange process. Here we formulate this contribution and compare it with HERA small-
x
DIS scattering data. We find that the BPST kernel along with a very simple local approximation to the proton and current “wave functions” gives a remarkably good fit not only at large
Q
2
dominated by conformal symmetry but also extends to small
Q
2
, supplemented by a hard-wall cut-off of the AdS in the IR. We suggest that this is a useful phenomenological parametrization with implications for other diffractive processes, such as double diffractive Higgs production.
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