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Register a new userConstraints on atmospheric charmed-meson production from IceCube
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Added by
Tomasz Palczewski PhD
Publication date
2016
fields
Physics
and research's language is
English
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At very-high energies (100 TeV - 1 PeV), the small value of Bjorken-x ($le10^{-3}-10^{-7}$) at which the parton distribution functions are evaluated makes the calculation of charm quark production very difficult. The charm quark has mass ($sim$1.5$pm$0.2 GeV) significantly above the $Lambda$$_{QCD}$ scale ($sim$200 MeV), and therefore its production is perturbatively calculable. However, the uncertainty in the data and the calculations cannot exclude some smaller non-perturbative contribution. To evaluate the prompt neutrino flux, one needs to know the charm production cross-section in pN -> c$bar{c}$ X, and hadronization of charm particles. This contribution briefly discusses computation of prompt neutrino flux and presents the strongest limit on prompt neutrino flux from IceCube.
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We analyze the IceCube four-year neutrino data in search of a signal from the Fermi bubbles. No signal is found from the bubbles or from their dense shell, even when taking into account the softer background. This imposes a conservative $xi_i<8%$ upper limit on the cosmic-ray ion (CRI) acceleration efficiency, and an $etaequiv xi_e/xi_i gtrsim0.006$ lower limit on the electron-to-ion ratio of acceleration efficiencies (at the $2sigma$ confidence level). For typical $xi_i$, a signal should surface once the number of IceCube neutrinos increases by $sim$an order of magnitude, unless there is a $<$PeV cutoff on the CRI spectrum.
The existence of diffuse Galactic neutrino production is expected from cosmic ray interactions with Galactic gas and radiation fields. Thus, neutrinos are a unique messenger offering the opportunity to test the products of Galactic cosmic ray interactions up to energies of hundreds of TeV. Here we present a search for this production using ten years of ANTARES track and shower data, as well as seven years of IceCube track data. The data are combined into a joint likelihood test for neutrino emission according to the KRA$_gamma$ model assuming a 5 PeV per nucleon Galactic cosmic ray cutoff. No significant excess is found. As a consequence, the limits presented in this work start constraining the model parameter space for Galactic cosmic ray production and transport.
On 22nd September 2017, the IceCube Collaboration detected a neutrino with energy of about 290 TeV from the direction of the gamma-ray blazar TXS 0506+056, located at a distance of about 1.75 Gpc. During the same time, enhanced gamma-ray flaring was also simultaneously observed from multiple telescopes, giving rise to only the second coincident astrophysical neutrino/photon observation after SN 1987A. We point out that for this event, both neutrinos and photons encountered a Shapiro delay of about 6300 days along the way from the source. From this delay and the relative time difference between the neutrino and photon arrival times, one can constrain violations of Einsteins Weak Equivalence Principle (WEP) for TeV neutrinos. We constrain such violations of WEP using the Parameterized Post-Newtonian (PPN) parameter $gamma$, which is given by $|gamma_{rm { u}}-gamma_{rm{EM}}|<5.5 times 10^{-2}$, after assuming time difference of 175 days between neutrino and photon arrival times.
A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18,000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject mis-reconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than one percent. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric muon neutrino plus muon antineutrino flux.
Adopting the Standard Halo Model (SHM) of an isotropic Maxwellian velocity distribution for dark matter (DM) particles in the Galaxy, the most stringent current constraints on their spin-dependent scattering cross-section with nucleons come from the IceCube neutrino observatory and the PICO-60 C$_3$F$_8$ superheated bubble chamber experiments. The former is sensitive to high energy neutrinos from the self-annihilation of DM particles captured in the Sun, while the latter looks for nuclear recoil events from DM scattering off nucleons. Although slower DM particles are more likely to be captured by the Sun, the faster ones are more likely to be detected by PICO. Recent N-body simulations suggest significant deviations from the SHM for the smooth halo component of the DM, while observations hint at a dominant fraction of the local DM being in substructures. We use the method of Ferrer et al. (2015) to exploit the complementarity between the two approaches and derive conservative constraints on DM-nucleon scattering. Our results constrain $sigma_{mathrm{SD}} lesssim 3 times 10^{-39} mathrm{cm}^2$ (6 $ times 10^{-38} mathrm{cm}^2$) at $gtrsim 90%$ C.L. for a DM particle of mass 1~TeV annihilating into $tau^+ tau^-$ ($bbar{b}$) with a local density of $rho_{mathrm{DM}} = 0.3~mathrm{ GeV/cm}^3$. The constraints scale inversely with $rho_{mathrm{DM}}$ and are independent of the DM velocity distribution.
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