Neutrino-nucleon cross section at ultrahigh energy and its astrophysical implications

Abstract

We present a quantitative study of the νN cross section in the neutrino energy range 10 4 < E ν < 10 14 GeV within two transversal QCD approaches: NLO DGLAP evolution using different sets of PDFs and BK small-x evolution with running coupling and kinematical corrections. We show that the non-linear effects embodied in the BK equation yield a slower raise in the cross section for E ν 10 8 GeV than the usual DGLAP based calculation. Finally, we translate this theoretical uncertainty into upper bounds for the ultra-high-energy neutrino flux for different experiments.

Neutrino telescopes as QCD microscopes

“…It is the main goal of this work to present a state-of-the-art calculation, taking into account recent developments in our understanding of perturbative and non-perturbative QCD, for the UHE neutrino-nucleon cross-section relevant for signal detection at neutrino telescopes. While a number of calculations have been provided by different groups in the past, both in the framework of collinear DGLAP factorisation [8,[19][20][21][22][23][24] and beyond it [25][26][27][28][29][30], there are now several significant motivations to revisit this calculation. The improvements made in this work, and their motivation, are detailed below.…”

R -parity violating supersymmetric explanation of the anomalous events at ANITA

“…Assuming the average strength of the anisotropic sources being Φ ν ∼ 2 × 10 −20 (GeV · cm 2 · s · sr) −1 with the mass of the RPV-SUSY mediator stau at m τ = 2 TeV, we use Eqs. (3) and (11) and perform a statistical analysis to find the 3σ favored region of the parameter space in the (λ ijk , m χ 0 1 ) plane, which is shown in the left panel of Fig. 4 as the yellow shaded region.…”

“…Even including the effect of ν τ regeneration [3][4][5][6], the resulting survival probability over the chord length of the ANITA events with energy greater than 0.1 EeV is < 10 −6 [7], largely due to τ -lepton energy loss inside Earth because of ionization, e + e − pair production, bremsstrahlung, and photonuclear interactions [8], thereby excluding the SM interpretation at 5.8σ confidence. A possible way out is by invoking significant suppression of the deep-inelastic neutrino-nucleon cross section above EeV [9][10][11][12][13] due to gluon saturation at small Bjorken-x < 10 −6 [14]. This will likely decrease the exponential attenuation of the Earth-crossing neutrino flux by at most a factor of 2-3 [15][16][17], whereas an order of magnitude or more suppression is needed to explain the two ANITA events.…”

Precision Determination of the Small- x Gluon from Charm Production at LHCb

“…As in the case of F L , we find a sizable reduction of the PDF uncertainties, which represent, by far, the dominant theory uncertainty for this process at high E ν . This way, NLO QCD provides a prediction accurate to ≲10% up to E ν ≃ 10 12 GeV, a region where a rather different behavior is found in scenarios with nonlinear QCD evolution effects [46]. Our results for the UHE cross section are more precise than the existing calculations [47], based on PDF fits where the only constraints on the small-x gluon come from the inclusive and charm HERA data, and they therefore provide a clean handle for disentangling possible beyond the standard model effects in this process [48].…”